&EPA
        United States
        Environmental Protection
        Agency
         Environmental Research
         Laboratory
         Athens GA 30605
EPA-600/8-80-012
Auiuisi |9xo
        Research and Development
An Approach to
Water Resources
Evaluation of
Non-Point
Silvicultural
Sources
(A Procedural
Handbook)

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                RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and  application of en-
vironmental technology.  Elimination  of traditional grouping  was  consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:

      1.  Environmental  Health Effects Research
      2.  Environmental  Protection Technology
      3.  Ecological Research
      4.  Environmental  Monitoring
      5.  Socioeconomic Environmental Studies
      6.  Scientific  and Technical Assessment Reports (STAR)
      7  Interagency Energy-Environment Research and Development
      8.  "Special"  Reports
      9.  Miscellaneous Reports

This report has been assigned to the "SPECIAL" REPORTS series. This series is
reserved for reports targeted to meet the technical information needs of specific
user groups. The series includes problem-oriented reports, research application
reports, and executive summary documents. Examples include state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the  results of major research and  development efforts.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia  22161.

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                                                     EPA-600/8-80-012
                                                     August 1980
                 An Approach To
     WATER RESOURCES EVALUATION
OF NON-POINT SILVICULTURAL SOURCES
            (A Procedural Handbook)
                          by
                     Forest Service
           United States Department of Agriculture
                  Washington, D.C. 20250
         Interagency Agreement No. EPA-IAG-D6-0660
                     Project Officer
                     Lee A. Mulkey
       Technology Development and Applications Branch
            Environmental Research Laboratory
                 Athens, Georgia 30605
             Environmental Research Laboratory
             Office of Research and Development
            U.S. Environmental Protection Agency
                  Athens, Georgia 30605

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                                       DISCLAIMER

  This report has been reviewed by the  Environmental Research Laboratory,  U.S. Environmental
Protection Agency, Athens, Georgia,  and approved for publication. Approval does not signify that the
contents necessarily reflect the views and  policies of the U.S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute endorsement or recommendation for
use.
                                             11

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        SPECIAL DEDICATION
           DAVID A. FALLETTI
  Dave Falletti recently met an untimely death
while the manuscript was being prepared.  He put
in many hours of work and much dedication to the
project, taking it through many complex obstacles.
Those who have carried on this work have been
guided by Dave's inspiration. The final document
represents many of his ideas which we hope will be
put into practice.
                    111

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                                         FOREWORD

  Our Nation's forests are major sources of valuable resources  including water  supplies,  wildlife
habitats, recreational areas, and timber products. As pressures for these resources increase, the need to
integrate resource management practices with techniques for controlling soil erosion and preventing the
discharge of pollutants into the Nation's waters becomes more important. To further this integration,
the  Forest  Service,  U.S.  Department of  Agriculture, and the Athens Environmental Research
Laboratory, U.S. Environmental Protection Agency, established a research project to develop methods
for  identifying and assessing alternative  technical solutions to pollution problems associated  with
specific silvicultural activities.

  This  handbook  addresses the technical  aspects of  non-point  source  water pollution related to
silviculture as expressed in the Federal Water Pollution Control Act Amendments of 1972 and the Clean
Water Act of 1977. It was designed to aid environmental  managers in developing water quality manage-
ment plans, strategies, and implementation programs and should be used in conjunction with local ex-
pertise and information on economic, social, and institutional aspects of silvicultural activities.
                                                      David W. Duttweiler
                                                      Director
                                                      Environmental Research Laboratory
                                                      Athens, Georgia
                                              IV

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                                               ABSTRACT
  This handbook provides an analysis methodology that
can be used  to  describe and  evaluate changes to the
water resource resulting from non-point silvicultural ac-
tivities. It covers only the pollutant generation and trans-
port processes and does not consider the economic, so-
cial and political aspects of pollution control.
  This state-of-the-art approach for analysis and predic-
tion of pollution from non-point silvicultural activities is
a rational estimation procedure that  is useful in making
comparative analyses of management alternatives. These
comparisons  are used in selecting preventive  and miti-
gative controls  and require site-specific  data for the
analysis.
  This handbook also  provides quantitative techniques
for estimating potential changes in  streamnow,  surface
erosion,  soil  mass movement, total potential sediment
discharge,  and temperature. Qualitative discussions of
the impacts of silvicultural activities on dissolved oxy-
gen, organic matter, nutrients, and introduced chemicals
are included.
  A control section provides a list of control practices
that have been used effectively and a methodology for
selecting mixtures of these controls for the prevention
and mitigation of water resource impacts. Such mixtures
are the technical basis for formulating Best Management
Practices.

  This  report was submitted in fulfillment  of Inter-
agency  Agreement Number EPA-IAG-D6-0660 by  the
Forest Service, U.S. Department of Agriculture, under
an agreement with the U.S.  Environmental Protection
Agency. This  report covers  the  period  December  1,
1976, to December 1, 1979, and work was completed as
of December 1, 1979.

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                                CONTENTS

Special Dedication	  iii
Foreword	  iv
Abstract	   v
Acknowledgements  	  viii
Conversion Factors  for U.S. and Metric Units 	  ix
            Introduction

            Chapter I   — Procedural Summary

            Chapter II   — Control Opportunities

            Chapter in  — Hydrology

            Chapter IV  — Surface Erosion

            Chapter V   — Soil Mass Movement

            Chapter VI  — Total Potential Sediment

            Chapter VII — Temperature

            Chapter VIII — Procedural Examples

            Chapter IX  — Dissolved Oxygen and Organic Matter

            Chapter X   — Nutrients

            Chapter XI  — Introduced Chemicals

            Glossary XII
                                     vn

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                                    ACKNOWLEDGEMENTS
   This handbook has been in preparation for ap-
 proximately  2Vz years.  While it is impossible to
 acknowledge all the people who have contributed
 to its publication,  special  appreciation goes to
 those who reviewed the draft copy and provided in-
 valuable comments and suggestions.
   Mike Barton, Bob Meurisse, Lee  Mulkey, and
 Dave Falletti  laid the original ground work for the
 interagency agreement. Their continuous support
 and advice maintained a continuity towards the in-
 tended goals.
   The "Control Opportunities" chapter was the
 collective work of many individuals.  A committee
 chaired by Wayne  Patton prepared  the material.
 Committee members were George Dissmeyer, Joe
 Gorsh,  Lee  Cromley, Al Dahlgreen, Clay Smith,
 Doug Roy, Bill Beaufait, and Leland Fansher.
  Numerous individuals provided data and advice
for the  "Hydrology"  chapter, including Richard
Goldstein,  Dennis  Harr,  John Hewlett,  Jim
Hornbeck, Dale Huff, Jim Lynch, Jim Mankin,
Jim Rogers,  Lloyd Swift, Stan Ursic, Elon Verry,
and all who reviewed earlier proposals. The tech-
niques  presented  in  the  "Total  Potential
Sediment" chapter are the extensions of field ap-
plications developed  by both researchers  and ap-
plied wildland hydrologists of the Northern Region,
U.S. Forest Service.  Special  thanks go to  Lee
Silvey, Dale Pfankuch, Bob Delk, Charles Leaf,
and Luna Leopold. George Brown and Jon Brazier
assisted  with and reviewed  the  "Temperature"
chapter.  John Crumrine's and Art O'Hayre's sug-
gestions and comments on the "Dissolved Oxygen
and Organic  Matter"  and "Nutrients" chapters
were greatly appreciated.

  Special thanks go to all the editing, graphics,
clerical staff,  and detailers for their work on both
the draft  and  final  manuscripts.  Coordinating
editors were Marianne Rieux  (draft manuscript)
and  Janet Sheppard  (final  manuscript).  Also
editing  were  Lynnea  Erickson,  Charlotte  Yar-
rington, Pete  Baez, and Vivian kollis. Joyce Reid
was primary illustrator assisted by Mamie Benson.
Typing was shared by Edie DeWeese,  Lorraine
Jehu,  Anne  Peterson,  Annie  Hanson,  and Jo
Laaksonen. Marilyn  Whitfield, assisted  by Eva
Erickson, coordinated the  office throughout work
on the manuscript.
                                              VIM

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            CONVERSION FACTORS FOR U.S. AND METRIC UNITS
 To convert
  column 1
into column 2,
 multiply by
             Column 1
                     Column 2
 To convert
  column 2
into column 1,
 multiply by
                                 LENGTH
     0.621
     1.094
     0.394
     0.386
   247.1
     2.471
     0.00003531
     0.00973
     1.057
     1.3079
     1.102
     2.205
     0.035
    14.50
     0.9869
     0.9678
    14.22
     0.446
     0.892
  (H
+ 32
            kilometer, km
            meter, m
            centimeter, cm
                      mile, mi
                      yard, yd
                      inch, in
                                  AREA
            kilometer2, km2
            kilometer2, km2
            hectare, ha

                        VOLUME
            centimeter3, cm3
            meter3, m3
            liter
            meter3, m3
                                  MASS
            ton (metric)
            kilogram, kg
            gram, g
                      mile2, mi2
                      acre, acre
                      acre, acre
                      foot3, ft3
                      acre-inch
                      quart (liquid), qt
                      cubic yard, yd3
                      ton (U.S.)
                      pound, 1b
                      ounce (avdp), oz
                                PRESSURE
            bar
            bar
            kg (weight)/cm2
            kg (weight)/cm2
                      Ib/inch2, psi
                      atmosphere, atm
                      atmosphere, atm
                      Ib/inch2, psi
        YIELD OR RATE
ton (metric)Xhectare     ton (U.S.)/acre
kg/ha                 Ib/acre

        TEMPERATURE
Celsius                Fahrenheit
-17.8C                OF
OC                    32F
20C                   68F
100C                  212F
   1.609
   0.914
   2.54
   2.590
   0.00405
   0.405
 28316.8
   102.8
     0.946
     0.7646
   0.9074
   0.454
  28.35
   0.06895
   1.013
   1.033
   0.07031
                                                      2.240
                                                      1.12
     (°F-32)
   9
    62.43
     8.108
    97.29
     0.00973
     0.00981
            gm/cm3
                                 DENSITY
                      Ib/ft3
                WATER MEASUREMENT
            hectare-meters, ha-m    acre-feet
            hectare-meters, ha-m    acre-inches
            meters3, m3             acre-inches
            metersVhour.mVhour   feetVsec
                                                               0.016
                                          0.1233
                                          0.01028
                                        102.8
                                        101.94

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                                      INTRODUCTION
  The  Federal Water  Pollution Control  Act
Amendments  of 1972, commonly referred to  as
Public  Law  92-500,  established  definite  goals
regarding the restoration and maintenance of the
physical, chemical, and biological  integrity of the
Nation's  waters.  The Act requires  that water
quality management planning, carried out under
Section 208 of the Act, include a process that iden-
tifies non-point sources of water pollution and that
establishes methods to control those sources to the
extent feasible. Non-point sources  associated  with
silviculture and related runoff  are among several
sources specifically mentioned in the Act as areas
to  be  addressed during 208   planning  and
implementation.
  The purpose of this technical  handbook is  to
provide a systematic, procedural,  and analytical
methodology for identifying and  assessing alter-
native technical solutions to existing or potential
non-point  source problems associated with  site-
specific silvicultural activities.  While  the specific
analytical  methods presented  are not the  only
methods available, they were carefully chosen ac-
cording to the capabilities of the  science and the
present state-of-the art.
  Non-point sources of pollution  result  from
natural causes, human actions, and the interac-
tions between natural events  and conditions as-
sociated with human use of  the land and its
resources. To  control these sources,  the United
States Environmental Protection  Agency (EPA)
has adopted, through Federal Regulation, the  con-
cept of Best Management Practices. As defined by
EPA,
  Best  Management  Practices (BMP) means  a
  practice  or combination of practices  that are
  determined by a state  (or designated area-wide
  planning agency) after  problem assessment, ex-
  amination  of alternative  practices,  and  ap-
  propriate public  participation to be the most ef-
  fective,   practicable (including technological,
  economic,  and  institutional considerations)
  means of preventing or reducing the amount of
  pollution generated  by non-point sources  to a
  level compatible with water quality goals.
  This handbook deals specifically with the  con-
cern and requirement for  control  of  non-point
sources  of water pollution related to silvicultural
activities as expressed in the Federal Water Pollu-
tion Control  Act Amendments  of 1972 and the
Clean Water Act of 1977. The handbook covers only
the technical aspects of non-point source water pol-
lution control; it  does  not address the  economic,
social,  and institutional  aspects that are also an
important part of the Best Management Practices
identification  process.  The  economic  considera-
tions are described in "Silvicultural Activities and
Non-Point  Pollution  Abatement:   A  Cost-
Effectiveness  Analysis  Procedure"  (USDA  FS
1978). The social  and institutional considerations
are manifested through public involvement during
environmental assessment review processes.
         DEFINITION OF EXISTING
           WATER QUALITY AND
      WATER QUALITY OBJECTIVES


  A prerequisite for use of this technical evaluation
procedure  is the identification  of existing  water
quality and water quality objectives as quantifiable
numerical  expressions. This type  of objective
provides a base against which the impacts of the
proposed silvicultural activities  can  be  compared
so the degree of additional control measures neces-
sary can be identified.
  In defining water quality objectives  against
which analysis results will be compared,  it must be
noted that the present state-of-the-art is, at best, a
rational  estimation  procedure.  Comparative
analysis will often fall short of predicting absolute
values.

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    APPLICATION OF THE PROCEDURE


   Silvicultural activities  to which the  described
 procedures apply include timber harvesting, trans-
 portation systems, and various cultural practices
,such as site preparation and timber stand improve-
 ment. These silvicultural activities are discussed in
 relationship to the principal potential water pollu-
 tants that may be generated and transported from
 the site.  Such pollutants  include inorganic sedi-
 ment, nutrients  (primarily  nitrogen and
 phosphorus),  heat, organic debris and introduced
 chemicals such as pesticides and fertilizers.
   Technical  procedures and methods suggested in
 this handbook fit within the overall process for non-
 point  source control as identified in EPA's "Non-
 Point Source Control Guidance Silviculture" docu-
 ment  (Singer and Maloney 1977).  The subjects
 covered  in this handbook are those within the
 shaded area shown in the process outline, figure 1.
 Included are the specific analysis methods required
 to meet steps 1 through 7 of the non-point control
 process. The methodology also provides  a simula-
 tion technique that can be used to  estimate the
 past and present condition of receiving waters (step
 3) when such information  is not available.
  The procedure gives proper recognition to space
and time variations occurring in natural environ-
ments, to  the pollution generation  processes  in-
volved, and  to defined water  quality objectives.
Thus,  it  permits  evaluation  of water  quality
management  options at a level  compatible with
other resource evaluations. It  also permits  com-
parison of the effects  of  proposed  management
alternatives  on  water   quality  in   different
watersheds and on different areas within  a specific
watershed, given the same data base.
  Application of  the  technical  methodology
generally requires  a basic knowledge  of hydrology
plus a working knowledge of forestry, soil science,
and engineering principles  as they are applied in a
natural environment. For  all practical  purposes,
analysis  and  prediction of non-point sources of
water pollution is  a rational estimation procedure
that is useful in  comparative analysis  of alter-
natives. Therefore, it is  necessary  for  informed
professionals to use local experience in applying the
analysis techniques.
  Although primarily a guide for the  technical
specialist, the handbook is also designed  for water
quality management  planners  and  other  land
managers. The flow charts in the "Introduction,"
"Procedural  Summary,"  and  "Control Oppor-
tunities" chapters guide these managers in  defin-
ing technical assessments needed. The analytical
procedures and references in the technical chapters
guide technical specialists  or consultants in mak-
ing those assessments.  The step-by-step illustra-
tions in the "Control Opportunities" chapter guide
project  designers and managers  in identifying ap-
propriate practices for the  particular  activity  and
site conditions.
    CHARACTERIZATION OF THE SITE


  Because the character of a site largely  deter-
mines the non-point sources that might be en-
countered and the effectiveness of specific control
measures, good site characterization data is  essen-
tial.
  Soil survey reports, stream survey  reports, and
geologic,  climatic,  topographic, and vegetation
maps with accompanying descriptive  materials all
provide input for development  of water quality
plans and other environmental assessments. The
level of detail in these documents should be com-
patible with the degree of reliability expected from
the analysis (recognizing the sensitivity as well as
the strengths and  weaknesses  of  the  analytical
procedure in terms of data  input.)
  In order to evaluate non-point sources on specific
sites or projects, the level of information must be
compatible with the map resolution used to iden-
tify the first-, second-, or  third-order  drainage
basins as  described by Strahler (1957). The  hand-
book analysis procedure is applicable  only to these
headwater areas (third-order basins or smaller).
  A larger  basin  may  be  characterized  from
selected third-order drainages within that basin
through data analysis  and extrapolation  based
upon the similarities in site and  management ac-
tivities. These evaluations may be useful in iden-
tifying general types of practices which may  repre-
sent BMP and in analyzing responses for specific
silvicultural  activities  basin-wide.  However, the
site-specific analysis is the  only  option that con-
siders site and activity variability  and the iden-
tification of a site-specific BMP.
  An environmental setting  is a continuum  which
includes the  hydrologic cycle, the nutrient  cycle,
and the erosion/sediment processes. The nature of
the non-point process is such that the potential pol-
lutant  must  be traced as thoroughly as  possible

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<~*
^->
 8
      NATURAL CONDITIONS
        BIOLOGIC
        PHYSIOGRAPHIC
        CLIMATIC
      PAST & CURRENT
      SILVICULTURAL
      ACTIVITIES
      CONDITION OF
      RECEIVING WATERS,
      PAST & PRESENT
      WATER QUALITY GOALS
ECONOMIC
SOCIAL
INSTITUTIONAL
CONSIDERATIONS
                               NATURAL POLLUTION
                                      IN HAZARD tND EX
                                        ^
                                      ESASJ
                                          PROBLEMS
                                                                SILVICULTURAL BMP
                                                                CONTRIBUTION TO
                                                                WATER QUALITY
                                                                MANAGEMENT
                                                                PROGRAM
                                                         NO PROBLEM

                                                             YES
                                                        ACTIVITIESDESIGNED
                                                        WITHIN CONDITIONS
                                                        AND HAZARDS
                                                                   I
                                                                   NO
                                                                         YES
                                                       NO
                               FEASIBLE BMP
                               IMPLEMENTATION
                                                 ATTAINMENT OF
                                                 DESIRED CONDITION —'
                                                 IN RECEIVING WATERS
       Figure 1.—Non-point pollution control process for silviculture (Singer and Maloney 1977).

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 through the entire system; therefore, all major en-
 vironmental  factors  significantly  affecting  its
 generation and transport  (into  the receiving
 waters)  must be recognized. Then these factors
 must  be related to  the physical  and biological
 processes that govern the pollutant's ultimate dis-
 position. This process is critical in  determining
 controls  for non-point  sources  caused  by
 silvicultural activities because most water quality
 constituents identified  as  pollutants also occur
 naturally  within the system.  The  analysis
 methodology is structured to differentiate natural
 pollution sources from those  which may  have
 resulted from human activities.
   This document does not discuss all potential pol-
 lutants.  It does  describe, in a procedural  manner,
 those potential pollutants that have been identified
 as being most important on a national basis.
        General Procedural Description


  The handbook procedure addresses the examina-
tion of the factors associated with generation and
transport of pollutants; it discusses identification,
in comparative, numerical, or qualitative terms, of
the changes in pollutant output expected to follow
particular silvicultural activities on a specific site.
  The techniques suggested for comparing existing
water quality with the water quality changes ex-
pected from proposed silvicultural activity provide
a rational approach for dealing with the following
facts: (1)  day-to-day variations in water quality in
undisturbed forest watersheds are substantial, par-
ticularly during the periods of changing flows; and
(2) fluctuations in undisturbed systems may be as
great as those in apparently similar, but disturbed,
systems.
  The procedure evaluates proposed  silvicultural
plans to identify expected changes in water quality
and  to determine  the type and degree of control
needed, if any, to meet water  quality objectives.
The  evaluation process continues until: (1) a com-
bination of preventive and mitigative controls that
meets the objectives has been identified, or  (2) an
acceptable land use alternative,  which meets the
objectives, has been determined. Mitigative con-
trols may  be necessary to correct existing non-point
sources before any new  activities  can be  made
technically acceptable.
  The following requirements must be met  before
applying the analysis procedure presented in this
handbook:
  1. Water quality objectives should be identified
and described with current information suitable for
comparative analyses.
  2. The pollutants should be identified in terms
of units, time, and space; and those terms should
be  compatible with  the terms  of the  analysis
procedure.
  3. Specific  information as  required  for  the
analysis should  be  available  to evaluate  the
silvicultural impacts onsite on a third-order basin
or smaller.
  4. The  causes  of non-point  sources  should  be
recognizable.
  5. Water quality existing  prior to  initiation of
silvicultural activities  should be measured or es-
timated with a  reasonable  degree of reliability
through analysis  of other appropriate types of in-
formation.
  6. Water  quality after silvicultural activities
should be estimated using the same approach ap-
plied to define existing conditions.
  This  document  includes  an  introduction;  a
procedural summary; a control opportunities sec-
tion; five technical chapters with quantitative dis-
cussions of hydrology,  surface  erosion, soil mass
movement,  total  potential  sediment,  and
temperature; an example demonstrating the quan-
titative procedures; three technical chapters with
qualitative discussions  of nutrients, dissolved ox-
ygen and  organic  matter,  and  introduced
chemicals; and a glossary of terms. The procedural
summary  provides  a  general  overview  and  a
simplified analysis methodology for  each subse-
quent chapter showing the general processes and
their relationships. The control opportunities and
technical chapters present a detailed discussion of
the procedures involved and the interrelationships
between processes.
  The  general procedure and interrelationships
between  the control opportunities and the
technical  chapters,   both quantitative  and
qualitative,  are  presented in the  flow diagram,
figure 2. The diagram depicts the iterative process
that may  be required if the proposed silvicultural
activity does not meet water resource goals. During
this  process,  the control  opportunities are
evaluated and the silvicultural  activity revised as
needed.

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                                           WATER QUALITY
                                              OBJECTIVE
                                              PROPOSED
                                           SILVICULTURAL
                                              ACTIVITY
QUANTITATIVE
  ANALYSIS
QUALITATIVE
 ANALYSIS
                                                                     i
                                                                   DISSOLVED
                                                                    OXYGEN
                                                                   & ORGANIC
                                                                    MATTER
                                                                                  NUTRIENTS
       INTRODUCED
        CHEMICALS
PROPOSED
SILVICULTURAL
ACTIVITY
TECHNICALLY
ACCEPTABLE
/ WATER \
/ QUALITY \
^ YES /OBJECTIVE MET \ NO ^


CONTROL
OPPORTUNITIES

J
\l














PROCEDURAL STEP, /\. npriQinw
COMPUTATION OR / \ pniNT
EVALUATION ^ 	 ^


. f

r



UbNU 1 to UnAr 1 bn
IN HANDBOOK


     Figure 2.—Interrelationships between the quantitative, qualitative, and control chapters and their applica-
                                tion to a proposed silviculture! activity.

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                                     LITERATURE CITED
Singer, J. R. and R. C. Maloney. 1977. Nonpoint     U.S.  Department of Agriculture, Forest  Service.
  source control guidance for silviculture. U.S. En-       1978. Silvicultural activities and non-point pol-
  viron. Prot. Agency, Washington, D.C.               lution abatement: a cost-effectiveness  analysis
                                                    procedure. Prepared under Interagency Agree-
Strahler, A.  N. 1957.  Quantitative  analysis       ment No. EPA-IAG-D6-0660 with the Environ.
  of watershed geomorphology.     Trans.  Am.       Prot. Agency, Athens, Ga.
  Geophys. Union 38:913-920.

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             Chapter I

PROCEDURAL SUMMARY
 This chapter was prepared by a committee composed
 of the individual coordinators for chapters II to XI.
            Leif E. Si verts

              Chairman
                 Li

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                         CONTENTS
                                                       Page
INTRODUCTION	   I.I
PROCEDURAL SUMMARY FOR CHAPTER II: CONTROL OPPOR-
 TUNITIES 	   1.3
PROCEDURAL SUMMARY FOR CHAPTER IE: HYDROLOGY	   1.6
   RAINFALL DOMINATED AREAS	   1.6
   SNOW DOMINATED AREAS	   1.8
PROCEDURAL SUMMARY FOR CHAPTER IV: SURFACE EROSION ....   1.10
PROCEDURAL SUMMARY FOR CHAPTER V: SOIL MASS MOVEMENT   1.12
PROCEDURAL SUMMARY FOR CHAPTER VI: TOTAL POTENTIAL SEDI-
 MENT 	   1.14
PROCEDURAL SUMMARY FOR CHAPTER VII: TEMPERATURE 	   1.17
SUMMARY OF CHAPTER VIII: PROCEDURAL EXAMPLES	   1.19
SUMMARY OF CHAPTER IX: DISSOLVED OXYGEN  AND ORGANIC
 MATTER	   1.19
SUMMARY OF CHAPTER X: NUTRIENTS 	   1.19
SUMMARY OF CHAPTER XI: INTRODUCED CHEMICALS 	   1.20
                           I.ii

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                               LIST OF FIGURES

                                                                            Page
I.I.—Generalized flow diagram for utilizing the control opportunities	    1.2
1.2.—Generalized flow diagram for the hydrology analysis	    1.7
1.3.—General flow diagram for the surface erosion analysis	    1.10
1.4.—General flow diagram for the soil mass movement analysis	    1.12
1.5.—General flow diagram for the total potential sediment analysis	    1.15
1.6.—General flow diagram for the temperature analysis	    1.17
                                      I.iii

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                                      INTRODUCTION
  This  chapter  summarizes  all procedures
presented in the handbook. It is  meant to provide
an overview of the analyses, clarify usage of tech-
niques and information, and indicate the interrela-
tions  between  the various  chapters. Procedural
summaries appear for the quantitative chapters II -
VII while general summaries are  presented for the
qualitative chapters VIII   XI. Included here for
each quantitative chapter is a basic flow diagram
which  is briefly explained by component.  More
detailed flow charts,  explanations of procedures,
and  the  logic behind those  procedures may be
found  in the individual technical chapters. The
descriptions included  in this chapter are provided
only for purposes of illustrating interrelationships;
they are not to be considered as descriptions of the
actual  steps necessary for technical analysis.
                                               I.I

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                                CONTROL
                             OPPORTUNITIES
  EVALUATION OF
  WATER QUALITY
        FOR
UNDISTURBED AREAS
  EXISTING
    SITE
CONDITIONS
 EVALUATION OF WATER
QUALITY FOR DISTURBED
        AREAS
(POSSIBLE APPLICATION
     OF CONTROLS)
                            DEFINE PROPOSED
                         SILVICULTURAL ACTIVITY
                         (POSSIBLE APPLICATION
                              OF CONTROLS)
                                   I
                          EVALUATION OF WATER
                          QUALITY RELATED TO
                        PROPOSED SILVICULTURAL
                          ACTIVITY (SIMULATED)
  WATER QUALITY
  OBJECTIVES MET
   OMPAREs
 TO WATER
  QUALITY
OBJECTIVES
 OBJECTIVES NOT MET
(POSSIBLE APPLICATION
     OF CONTROLS)
                                                                   PROCEDURAL STEP
                                                                   COMPUTATION OR
                                                                     EVALUATION
            Figure 1.1.—Generalized flow diagram for utilizing the control opportunities.
                                   1.2

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                             PROCEDURAL  SUMMARY FOR
                      CHAPTER II:  CONTROL OPPORTUNITIES
  Because  silvicultural activities  change certain
landscape characteristics, primarily by causing soil
disturbance, by altering the vegetative cover, and
by changing local drainage patterns, the generation
and transport of potential pollutants may be ac-
celerated.  Utilization  of  effective control  tech-
niques must then be considered.
  In this handbook, control techniques are grouped
into  procedural,   preventive,  and  mitigative
categories.  Procedural controls are those concerned
with administrative actions.  Preventive controls
apply to the pre-implementation,  planning phase
of a silvicultural activity. Mitigative controls are
physical, chemical,  or vegetative measures applied
to ameliorate problems that exist  now, as well as
those  that  may exist after a silvicultural activity
has taken place.
  Procedural, preventive, and/or mitigative control
practices can  be prescribed for various reasons,
commonly including: (1)  protection  of water
quality, (2) protection of capital investments such
as roads and buildings, and (3) protection of site
productivity.  It   may  not  be  necessary  to
specifically formulate  controls for water quality
because  the controls imposed for site protection
may be adequate to meet water quality objectives.
It is logical to first design a management plan to in-
sure protection of site productivity and capital in-
vestments.  If subsequent analyses show such a plan
to be inadequate to meet water quality objectives,
additional  controls  can be prescribed as needed.
  The  control  measures are presented in four dif-
ferent ways. First,  there is an activity-impact list
that describes each silvicultural activity and its as-
sociated resource impacts. Next there  is a list of
resource impacts   and  possible  control oppor-
tunities. Then each control is presented in a series
of tables that display their  relationship to  the
variables in each of the technical chapters. Finally,
there is a description of each control and whether it
is procedural, preventive,  or mitigative.
  Figure I.I is a general flow diagram which sum-
marizes the control  selection process. This process
is explained on the  following pages.
                   EXISTING
                     SITE
                 CONDITIONS
  The existing water quality must  be known so
that any  changes  in  the quality  following  the
proposed silvicultural activity can be evaluated. It
is essential that some base be established so that
impacts can be properly assessed.  The existing
water  quality and site conditions  should be
measured whenever possible.  If this is not feasible,
then the existing water quality may be simulated
using the procedures  provided  in  the technical
chapters or  locally derived procedures that have
proven effective.
  The existing water quality will be  greatly in-
fluenced by the  history of the site,  specifically
natural (fires,  floods,   etc.) and   man-induced
(previous  silvicultural  operations,  mining, etc.)
disturbances. It must be determined if the site has
been previously disturbed and if the disturbance is
a contributing non-point source.
               EVALUATION OF
            WATER QUALITY FOR
            UNDISTURBED AREAS
  The measured or simulated water quality for an
undisturbed site or a site that has previously been
disturbed but no longer has contributing non-point
sources is compared to the water quality objectives
that have been established for the site. The objec-
tives should not be exceeded. If they are exceeded,
the  objectives may  be  incompatible  with  the
natural conditions and should be reviewed by the
appropriate authority.
                                               1.3

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           EVALUATION OF WATER
          QUALITY FOR DISTURBED
       AREAS (POSSIBLE APPLICATION
               OF CONTROLS)
  The measured or simulated water quality for a
disturbed site is compared to the water quality ob-
jectives that have been established for the site. If
the objectives are exceeded, mitigative  controls
should be considered to ameliorate existing non-
point sources. If the application of mitigative con-
trols is not feasible, the objectives can be reviewed
by the appropriate authority or the management of
the site can be reevaluated.
                  COMPARE
                      TO
               WATER QUALITY
                 OBJECTIVES
  The estimated post-silvicultural activity water
quality is compared to the established objectives. If
the  objectives  are not exceeded,  the  proposed
silvicultural activity is compatible and may be con-
sidered technically acceptable. If the objectives are
exceeded,  control  opportunities should  be
evaluated  and  incorporated  into a  revised
silvicultural plan where appropriate.
             DEFINE PROPOSED
          SILVICULTURAL ACTIVITY
         (POSSIBLE APPLICATION OF
                 CONTROLS)
  The control  opportunities  can be  used as a
reference to help in the formulation of the initial
silvicultural  plan.  Mixtures  of preventive,
mitigative, and procedural controls can collectively
become a silvicultural plan.
      EVALUATION OF WATER QUALITY
  RELATED TO PROPOSED SILVICULTURAL
           ACTIVITY (SIMULATED)
  The water quality that will follow the proposed
silvicultural activity is estimated using the simula-
tion procedures provided in the technical chapters
or locally derived procedures that have proven ef-
fective. The same simulation procedures used for
evaluating the existing conditions must be used to
simulate the post-silvicultural activity  water
quality.
              OBJECTIVES NOT
        MET (POSSIBLE APPLICATION
               OF CONTROLS)
  When the proposed silvicultural activity results
in non-point source pollution such that the water
quality  objectives  are  exceeded,  control  oppor-
tunities are evaluated that could be used to reduce
these potential impacts. Preventive controls are in-
itially evaluated, and those that are determined to
be feasible are incorporated  into the silvicultural
activity plan. The revised  silvicultural  activity
plan, including additional preventive controls, is
evaluated using the simulation procedure. If the es-
timated  water  quality  following   the  revised
silvicultural activity meets the objectives the ac-
tivity is considered technically acceptable from a
water quality standpoint. If the objectives are ex-
ceeded,  mitigative controls  are evaluated; and
those that are determined to be feasible are incor-
porated into the plan. The revised silvicultural ac-
tivity plan, including  both  preventive and
mitigative controls, is evaluated using the simula-
tion  procedure.  The  resulting estimated  water
quality is compared to the objectives. New controls
may replace  portions of  the silvicultural plan or
may be simply added to it to form a revised plan. It
is recommended that several  mixes of controls that
meet water  quality  goals  be formulated and
presented to the manager.
                                              1.4

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               WATER QUALITY
              OBJECTIVES MET
  The proposed silvicultural activity is technically
acceptable if the simulated water quality following
that activity meets the objectives set for the stream
or stream segment. Implementation follows the ap-
propriate economic and social evaluations.  If the
proposed silvicultural  activity  would result in  a
degradation of water quality that would exceed the
objectives,  controls should be instituted  and the
plan revised to incorporate them. If the objectives
would be exceeded even when controls have been
considered, the objectives  should be reviewed or
the land uses for  the site should  be reevaluated.
                                               1.5

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                           PROCEDURAL  SUMMARY FOR
                             CHAPTER III: HYDROLOGY
  The technical procedure begins with a descrip-
tion and an analysis of the hydrologic system of the
area under study. Among the many variables con-
sidered in  the  evaluation  are  precipitation,
evapotranspiration, soil water status,  and
streamflow. All of these variables influence, either
directly or indirectly, the availability of energy for
generation and/or transport of  non-point source
pollutants. Thus, results of the hydrologic analyses
provide essential input  for analysis  of non-point
source  pollution   potentials  using  methods
described  in subsequent chapters.
  Hydrologic response to silvicultural  activities
varies greatly from region to region, as well as from
site to site within a hydrologic  region. For those
hydrologic regions where snowfall dominates the
hydrologic cycle, all pertinent processes, including
snow redistribution, are discussed, and  methods
are presented for evaluation. However,  in other
parts of the country, some processes,  such as snow
redistribution are not significant.  To account for
these regional hydrologic differences, guidelines are
presented for modifying  the basic, more  com-
prehensive analytic  framework.
  The objective of this evaluation is to estimate the
amount  of  water  potentially  available for
streamflow that is  generated before and after a
proposed silvicultural activity. Water available for
streamflow  is distributed either  as an annual
hydrograph  in which  6-day average  discharge
values are plotted or as a flow  duration curve in
which  7-day  average  discharge  values  are
calculated. Figure 1.2 is a flow diagram that out-
lines the principal steps of the hydrology analysis.
A description of the flow diagram  follows.
                  DOMINANT
               PRECIPITATION
  The hydrologic evaluation procedure for rainfall
 dominated regions differs  from  the hydrologic
 evaluation procedure for  snowfall dominated
 regions. The predominant form of precipitation is
determined, and the  corresponding  hydrologic
evaluation procedure is selected.
     RAINFALL DOMINATED AREAS
  If rainfall dominates the precipitation regime of
the watershed of interest, the procedure as outlined
below is applied.
      c
SEASONAL PRECIPITATION
  An estimate of seasonal precipitation is needed.
     SEASONAL EVAPOTRANSPIRATION
   Seasonal evapotranspiration is either estimated
 input or estimated using regional graphs which
 relate evapotranspiration  to  season of the year.
 Latitude is an additional variable needed for the
 Appalachian  Mountain  and Highland hydrologic
 region.
                                                        SEASONAL EVAPOTRANSPIRATION
                                                           ADJUSTED FOR LEAF AREA
                                                    INDEX REDUCTION AND ROOTING DEPTH
  The leaf area index before and after the proposed
silvicultural activity is estimated in the field or is
derived  from  basal  area-leaf  area  index
relationships developed for the hydrologic region. A
reduction in leaf area index results in less water lost
through evapotranspiration, which in turn leaves
more water available  for streamflow. Rooting
depth, a reflection of soil  depth,  influences the
                                              1.6

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                                HYDROLOGY
                                DOMINANT
                              PRECIPITATION
                                                                       PROCEDURAL STEP.
                                                                       COMPUTATION OR
                                                                        EVALUATION
            SNOW
c
                                                       RAIN
SEASONAL PRECIPITATION
                                       c
SEASONAL PRECIPITATION
    SEASONAL PRECIPITATION
        ADJUSTED FOR
     SNOW REDISTRIBUTION
          SEASONAL
     EVAPOTRANSPIRATION
                                                 SEASONAL
                                            EVAPOTRANSPIRATION
          SEASONAL
     EVAPOTRANSPIRATION
   ADJUSTED FOR REDUCTION
       IN COVER DENSITY
                                                SEASONAL
                                           EVAPOTRANSPIRATION
                                         ADJUSTED FOR REDUCTION
                                          IN LEAF AREA INDEX AND
                                              ROOTING DEPTH
    WATER AVAILABLE FOR
    ANNUAL STREAMFLOW
                                           WATER AVAILABLE FOR
                                           ANNUAL STREAMFLOW
         NORMALIZED
        DISTRIBUTION
     GRAPH ADJUSTED FOR
         CHANGES IN
        COVER DENSITY
    PRE AND POST
    SILVICULTURAL
ACTIVITY HYDROGRAPHS
                                          REGIONAL FLOW DURATION
                                           ADJUSTED FOR WATER
                                           AVAILABLE FOR ANNUAL
                                               STREAMFLOW
                                               FLOW DURATION CURVE
                                              ADJUSTED FOR REDUCTION
                                             IN LEAF AREA INDEX, ASPECT,
                                                AND ROOTING DEPTH
                                                   PRE AND POST
                                                   SILVICULTURAL
                                                 ACTIVITY FLOW AND
                                                 DURATION CURVES
            Figure I.2.—Generalized flow diagram for the hydrology analysis.
                                  1.7

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amount of water available for evapotranspiration.
Greater storage capacity results in more water be-
ing available to evapotranspiration loss.
          WATER AVAILABLE FOR
           ANNUAL STREAM FLOW
  Water  available for seasonal  streamflow  is
calculated  by  subtracting  adjusted  seasonal
evapotranspiration  from seasonal  precipitation.
Summation of  water available  for  seasonal
streamflows results in water available for annual
streamflow.
         REGIONAL FLOW DURATION
       CURVE ADJUSTED FOR WATER
          AVAILABLE FOR ANNUAL
               STREAMFLOW
       SNOW DOMINATED AREA
                                                  If snow dominates the precipitation regime of the
                                                watershed of interest, the procedure outlined below
                                                is applied.
      c
SEASONAL PRECIPITATION
                                                  An estimate of seasonal precipitation is needed.
         SEASONAL PRECIPITATION
           ADJUSTED FOR SNOW
              REDISTRIBUTION
  A regional flow duration curve is selected from
 those provided or is supplied by the user. It is ad-
 justed for the water available as annual streamflow
 prior to the silvicultural activity. The flow duration
 curve  is  based  upon  7-day  average  discharge
 values.
  For geographic areas in which snow redistribu-
tion is likely, the size and orientation of open areas
must be  known to  evaluate the potential
redistribution of snow. The amount of snow that is
redistributed is determined largely  by the size of
the opening in the overstory.
          FLOW DURATION CURVE
       ADJUSTED FOR REDUCTION IN
       LEAF AREA INDEX, ASPECT, AND
              ROOTING DEPTH
  The post-silvicultural activity flow duration
 curve is calculated  by  adjusting the  pre-
 silvicultural activity flow duration curve  for the
 leaf area index reduction and aspect and  rooting
 depth for the site. This is done with a least  squares
 equation.
       PRE- AND POST-SILVICULTURAL
     ACTIVITY FLOW DURATION CURVES
  Pre- and post-silvicultural activity flow duration
curves for 7-day average values are plotted.
     SEASONAL EVAPOTRANSPIRATION
  Seasonal evapotranspiration is either estimated
input or  estimated using regional graphs  which
relate precipitation and aspect to evapotranspira-
tion. More water is lost by evapotranspiration from
southern  aspects than from northern aspects.
     SEASONAL EVAPOTRANSPIRATION
        ADJUSTED FOR REDUCTION
             IN  COVER DENSITY
  A reduction in  cover density may result in a
reduction of evapotranspiration loss. Cover density
changes may  be estimated from basal area-cover
density relationships.
                                            1.8

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           WATER AVAILABLE FOR
           ANNUAL STREAMFLOW
  Water  available  for  seasonal  streamflow is
calculated  by  subtracting adjusted  seasonal
evapotranspiration from  seasonal  precipitation.
Summation  of  water  available  for  seasonal
streamflow  yields water  available for  annual
streamflow.
         NORMALIZED DISTRIBUTION
           GRAPH ADJUSTED FOR
        CHANGES  IN COVER DENSITY
which occurs during consecutive 6 day intervals.
Distribution graphs are presented for  open and
fully forested areas. Interpolation is necessary to
obtain  a  normalized  distribution graph for
silvicultural  treatments  intermediate  to  fully
forested and open.
       PRE- AND POST-SILVICULTURAL
          ACTIVITY HYDROGRAPHS
  The  normalized  distribution  graphs  for  the
hydrologic region are selected. These graphs repre-
sent the distribution of annual flow as a percentage
  Multiplication of values on the normalized dis-
tribution graph by the water available for annual
streamflow and a conversion  factor results in a
hydrograph with  units  of cubic  feet/second.
Hydrographs for each silvicultural activity area are
calculated separately and then summed to give the
pre-  or post-silvicultural  activity hydrograph for
the entire watershed.
                                             1.9

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                  PROCEDURAL SUMMARY FOR CHAPTER IV:
                                  SURFACE EROSION
  A Modified Soil-Loss Equation is presented as a
method that may be used to estimate surface ero-
sion  from disturbed  sites. Tables, graphs, and
equations are used for the evaluation process. To
apply these tools, information characterizing soils,
topography, and ground cover must be obtained for
a given site.
  The objective of this analysis procedure is to es-
timate the quantity of accelerated soil loss (tons/
year) and the amount that might reach a stream
under given silvicultural activity conditions. Soil
loss is based on four factors to evaluate the detach-
ment of soil particles on a site. If this  detached
material is  not delivered to a  water course, there
will  be no degradation of water quality.
  Estimates of sediment which may be delivered to
a stream system are  based on eight factors. The
model delivers eroded material across a reference
boundary, such as out of a clearcut block and into
an adjacent area.
  Figure 1.3 is  a  flow diagram that outlines the
principal steps involved in a surface erosion evalua-
tion. A narrative explaining the flow diagram fol-
lows.
             ONSITE ESTIMATED
            SURFACE SOIL LOSS
  Estimated  potential  surface erosion is  based
upon  a modified version of Wischmeier and
Smith's Universal Soil  Loss Equation. Modifica-
tions were made to adopt their equation to forested
situations  and silvicultural  activities.  The
modified equation uses  the four following factors:
(1) rainfall, (2)  soil erodibility, (3) slope gradient
and slope  length of  disturbed site, and (4) the
vegetation present and management applied. The
solution of the equation  gives estimated soil loss in
tons/acre/year. When multiplied by the acres dis-
turbed, the result is tons/year.
                                          SURFACE
                                          EROSION
                    ONSITE ESTIMATED
                    SURFACE SOIL LOSS
                                   1
         SEDIMENT
      DELIVERY INDEX
                                   ESTIMATED POTENTIAL
                                          SEDIMENT
                                   DELIVERED TO STREAM
                       Figure I.3.—General flow diagram for the surface erosion analysis.
                                             1.10

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                  SEDIMENT
               DELIVERY INDEX
roughness, and (8) special characteristics of a local
site, if applicable.
  The delivery index represents the fraction of the
available sediment which might reach a stream.
  The  delivery  index  is  used to estimate the
amount of eroded material on a disturbed site that
might reach the closest stream channel. The index
is estimated from factors that are assumed to con-
trol sediment delivery: (1) available water for sur-
face runoff, (2) texture of the eroded material, (3)
amount  of ground  cover  present  in the  area
between the disturbed site and stream channel, (4)
overall slope shape, (5) slope gradient of the land,
(6) distance material must travel between the dis-
turbed  site  and  stream channel,  (7)  surface
      ESTIMATED POTENTIAL SEDIMENT
           DELIVERED TO STREAM
  The onsite annual estimated surface soil loss in
tons/year is multiplied by the delivery index to ob-
tain an  estimate of the quantity of material that
may be delivered  to a stream.  The result is in
tons/year. This estimated value is required as input
into  the  analysis of total  potential sediment
production (chapter VI).
                                              1.11

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                           PROCEDURAL SUMMARY FOR
                       CHAPTER V: SOIL MASS MOVEMENT
  The chapter on soil mass movement provides a
method for identifying and qualitatively assessing
the site factors and management activities that in-
crease the hazard of soil mass movement. Soil mass
movements are classified into two general types:
(1)  the debris  avalanche-debris flow,  and (2) the
slump-earthflow. Overall ratings can be made  in
terms of high,  moderate, or low hazard.
  Only material that is  delivered  directly  to  a
channel  system is  considered under soil  mass
movement. It is recognized that mass movement
produces  a supply of credible material that may
reach stream channels at a much later date than
the actual  mass movement event and that con-
siderable  onsite  resource damage  may  occur.
Unless the material reaches a channel, however, no
water quality degradation would occur. The  effect
that any failure will have on water quality degrada-
tion depends primarily on the size and volume of
material reaching  a channel and the energy of the
stream system for transport.
  The  information obtained  from the soil  mass
movement evaluation is used  as input to the total
potential sediment estimation (chapter VI).
  The objective of this analysis procedure is  to es-
timate the hazard of a soil mass movement and to
estimate the quantity of mass movement material,
in tons, that may be deposited in a water course
given the pre- and post-silvicultural activity condi-
tions.  Silvicultural activities may have the poten-
tial to increase the hazard and/or size of a  mass
movement occurrence  as  well as the amount  of
material that may reach a stream.
  Figure 1.4. outlines the principal steps for the soil
mass movement analysis. A description of  those
steps follows.
             SOIL MASS
             MOVEMENT
           HAZARD INDEX
 POTENTIAL SOIL MASS MOVEMENT
                I
       DELIVERY FACTOR
TOTAL POTENTIAL TONS DELIVERED
            TO STREAM
      ACCELERATION FACTOR
                                        Figure I.4.—General flow diagram for the soil mass movement analysis.
                                            1.12

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               HAZARD INDEX
              DELIVERY FACTOR
  The hazard index of a soil mass movement occur-
rence is  determined by the type  of movement,
slump-earthflow versus debris  avalanche-debris
flow,  and  a variety  of  onsite  parameters  and
silvicultural activities. The more critical factors in-
clude: (1) slope gradient, (2) slope configuration,
(3)  soil depth, (4)  soil texture, (5) bedding struc-
ture  and  orientation,  (6)  precipitation,   (7)
drainage, (8) vegetation, (9) harvest methods, and
(10) roads.  The result of this subjective evaluation
is  a hazard index—high,  medium, or low.  The
hazard index indicates the intensity of analysis
that may be necessary to adequately evaluate mass
movement.
  The quantity of material in tons that would fae
delivered to a stream is estimated according to: (1)
type of mass movement,  (2) position of failure on
slope,  (3) slope gradient, and  (4) uniformity of
slope. The delivery factor is expressed as a percent.
          TOTAL POTENTIAL TONS
           DELIVERED TO STREAM
  The potential mass movement in tons is mul-
tiplied by the delivery factor to estimate the quan-
tity of material that would enter a stream. The
results are expressed in tons.
                                                             ACCELERATION FACTOR
     POTENTIAL SOIL MASS MOVEMENT
  The  potential  quantity of mass movement, in
tons, that could  occur is estimated. The average
volume of mass movement that has occurred on the
site in the  recent  past  is determined  by type
(slump-earthflow,  or  debris avalanche-debris
flow), or a subjective estimate  is made where there
is no history of mass movement. The volume of
material is converted to tons based upon the type
and bulk density of material that would be carried
in a mass movement event.
  For determination of the quantity of soil mass
movement delivered to a stream channel due  to
silvicultural  activity, measurements  should be
made on an area with similar characteristics and a
history of silvicultural activity comparable to that
being proposed for  the area under analysis. The
ratio of soil mass movement due to silvicultural ac-
tivity to that from natural causes is given as an ac-
celeration  factor. The potential  increase in soil
mass  movement due to  implementation of the
proposed silvicultural activity can be estimated by
multiplying the acceleration factor by the natural
soil movement occurring on  the area. This es-
timated value is used as input into the total poten-
tial sediment analysis (chapter VI).
                                             1.13

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                            PROCEDURAL SUMMARY FOR
                   CHAPTER VI: TOTAL POTENTIAL SEDIMENT
   This chapter provides an analytical framework
 for evaluating potential changes in sediment dis-
 charge associated  with silvicultural  activities.
 Changes in sediment discharge due to introduced
 sources (surface erosion and soil mass movement)
 and flow related increases are evaluated.
   The quantitative evaluation of suspended sedi-
 ment  and bedload sediment is based  on  locally
 derived regression equations. These procedures are
 designed to be used below the silvicultural activity,
 generally  at the mouth of third order  drainages.
 Impacts to  channel  geometry  are  qualitatively
 evaluated  using bedload transport-stream power
 curves developed from local data.
   Figure 1.5 outlines the principal steps for  the
 total potential sediment analysis.
              SUBDRAINAGE AND
     STREAM REACH CHARACTERIZATION
         SEDIMENT RATING CURVES
                     AND
             CHANNEL STABILITY
  Measured suspended sediment concentrations
and concurrent stream discharges for a wide range
of flows collected on the third order drainage are
plotted. The relationship can then be expressed
mathematically in a sediment rating curve. Using
the pre-  and  post-silvicultural  activity
hydrographs, the change in suspended sediment
discharge is calculated in tons/year. Appropriate
data should also be collected on the third order
stream reach so that a channel stability rating  may
be made. This data may be used to form a basis for
determining the limits for stream stability changes.
   After a suitable site has been selected, data can
 be collected for the suspended sediment and bed-
 load rating curves. This data should be obtained on
 a third order drainage that is below the proposed
 silvicultural activity. To evaluate effects of channel
 encroachments, stream reaches immediately below
 or adjacent to  the silvicultural activity should be
 selected for a quantitative evaluation.
   The soil mass movement and  surface erosion
 analyses, as  outlined in  chapters IV and  V,
 characterize the subdrainage with respect to the in-
 troduced sources that are a result  of the proposed
 silvicultural activity and  provide input into the
 total potential  sediment calculations.
       STREAMFLOW HYDROGRAPHS
                     OR
          FLOW DURATION CURVES
  The  streamflow hydrographs or flow duration
curves for the pre- and post-silvicultural activities
are obtained from "Chapter El: Hydrology."
            INTRODUCED SOURCE
           SOIL MASS MOVEMENT
             COARSE AND FINE
  The output  from the  soil mass movement
analysis described in chapter V is  expressed in
terms of total potential tons of material delivered
to the stream. The quantity of material is an es-
timate of the total potential soil mass movement
material  that  may be delivered  to the  closest
available drainageway following the silvicultural
activity. The total volume of material is expressed
as the percentage of coarse and of fine (wash load)
material. Assuming this material is  all available
during the first year after the activity, the percent
of fines can be used as a part of the total suspended
sediment that is compared with the water quality
objective.
  The coarse material is  used with  the bedload-
transport  stream power curve  to provide  a
qualitative estimate of potential stream channel
changes. The total volume is one component of the
total sediment  of all sources that are  available
within the watershed.
                                             1.14

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                                                        TOTAL
                                                 POTENTIAL SEDIMENT
                                                                  PROCEDURAL STEP.
                                                                  COMPUTATION OH
                                                                   EVALUATION
                                              SUBDRAINAGE AND STREAM
                                               REACH CHARACTERIZATION
      STREAMFLOW HYDROGRAPHS
       OR FLOW DURATION CURVES
            I
               CHANNEL GEOMETRY
                   AND IMPACTS
 SEDIMENT RATING
   CURVES AND
CHANNEL STABILITY
BED LOAD
 RATING
 CURVES
                       1
                        INTRODUCED SOURCE:
                        SOIL MASS MOVEMENT
                          COARSE AND FINE
 BED LOAD SEDIMENT
TRANSPORT—STREAM
POWER RELATIONSHIP
                                             Ł_Ł
                                      POTENTIAL STREAM
                                      CHANNEL CHANGE
                                        (QUALITATIVE)
            TOTAL POTENTIAL
          SEDIMENT ALL SOURCES
INTRODUCED SOURCE
 SURFACE EROSION
                                                     S"\_
                                                 UNIT CONVERSION AND
                                                COMPARISON OF TOTAL
                                            POTENTIAL SUSPENDED SEDIMENT
                                                  TO SELECTED LIMITS
                              Figure I.5.—General flow diagram for the total potential sediment analysis.

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           INTRODUCED SOURCE
             SURFACE EROSION
  This is the volume of delivered eroded material
introduced as a result of the silvicultural activity.
It is expressed as tons/year. This volume is added
to the total susperfded sediment increases and com-
pared to the water quality objective.
are evaluated based on the potential changes an-
ticipated  for  given  silvicultural  activities  and
measured channel characteristics. The calculations
are utilized to obtain qualitative interpretations of
stream channel response.
      BEDLOAD SEDIMENT TRANSPORT-
       STREAM POWER RELATIONSHIP
    UNIT CONVERSION AND COMPARISON
                     OF
TOTAL POTENTIAL SUSPENDED SEDIMENT TO
             SELECTED LIMITS
  Selected maximum limits  for suspended sedi-
ment  in milligramsAiter, as set by water quality
objectives, are converted to tons for comparative
purposes. Typical objectives  may be state sedi-
ment  standards  or stream  channel  stability
threshold limits.
  All  potential suspended sediment increases due
to streamflow increases, surface erosion, and wash
load (silts and clays) contributed from soil mass.
movement processes are combined. If the water
quality objective has been exceeded, appropriate
controls for the introduced sources must then be
identified and a reanalysis performed.
         BEDLOAD RATING CURVES
  Applying the  same procedures used  for the
suspended sediment rating curves, a bedload rating
curve for the third order stream reach is prepared.
Pre- and post-silvicultural activity hydrographs or
flow duration curves are used to  determine the
flow-related changes in bedload discharge. These
curves  are also used to  develop bedload-stream
power relationships for a  qualitative evaluation of
stream channel response.
    CHANNEL GEOMETRY AND IMPACTS
  This relationship is  developed from  measured
bedload data and channel geometry for the third
order stream. The variables are: (1) width, (2) sur-
face water slope, (3) particle size of bed material in
transport, (4) bedload transport rates, and  (5)
stream discharge, all obtained over a wide range of
flows.  This  relationship  is used  to determine
qualitative changes in  channel response from in-
troduced  soil  mass  movement  material  and
changes in stream power.
  POTENTIAL STREAM CHANNEL CHANGES
               (QUALITATIVE)
  Changes in the variables affecting stream power
  This is a qualitative output of the changes that
can be expected in terms of scour and deposition
within a channel. These changes are due to altera-
tions in stream power and/or introduced soil mass
movement material.
                                                 TOTAL POTENTIAL SEDIMENT ALL SOURCES
  This is a composite of increases in sediment dis-
charge made available within the watershed as a
result of silvicultural activity. It is composed of all
sources of sediment including: (1) suspended sedi-
ment due to  increased stream flow,  (2) bedload
sediment due to increased stream flow, (3) surface
erosion from all sources, and (4)  soil  mass move-
ment from all sources.
  This is used to compare the pre-activity to post-
activity sediment discharge. An index of the total
potential increases can be determined. Although
expressed in tons/year, temporal  and spatial  dis-
tributions are not analyzed.
                                             1.16

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                          PROCEDURAL SUMMARY FOR
                          CHAPTER VII: TEMPERATURE
  Increased water  temperature  can be  either
beneficial or detrimental to the water resource. For
streams that are cooler than optimum, a moderate
increase in temperature  could increase produc-
tivity and have a beneficial effect on the aquatic
environment.  However,  streams  having
temperatures  that  approach critical  threshold
limits during  the  summer months  could reach
lethal levels if these temperatures were increased.
  When the removal of shading vegetation along
stream  channels increases the stream's exposure to
heating from solar radiation, it also increases the
potential for a rise  in water temperature. The
magnitude of the increase is a function of the fol-
lowing  variables:  (1)  the  amount  of canopy
removed, (2) length of time the stream is exposed
to direct solar radiation,  (3) streambed material,
(4) stream width,  (5) stream discharge, and  (6)
         subsurface inflow. The described procedure, based
         upon the use of a temperature model, provides a
         means of assessing the influence of these variables
         as they are affected by silvicultural activities and
         control practices.  Downstream temperature
         changes are  evaluated using a mixing ratio.

          The objective of this procedural analysis is to es-
         timate the maximum potential daily temperature
         increase (in degrees Fahrenheit)  above  the pre-
         silvicultural activity  water  temperature.
         Silvicultural activities may remove vegetation that
         provides shade to the water surface. The loss of this
         shading  may  result  in  increased  water
         temperatures.

          Figure  1.6 outlines the  principal  steps  in
         evaluating  the  potential  change  in  stream
         temperature.
                                     TEMPERATURE
       INCIDENT HEAT
          LOAD (NET
     SOLAR RADIATION)
                       I
  STREAM
DISCHARGE
EXPOSED SURFACE
       AREA
 FLOWING WATER
                         I
                                  MAXIMUM POTENTIAL
                             DAILY TEMPERATURE INCREASE
                      Figure I.6.—General flow diagram for the temperature analysis.
                                           1.17

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            INCIDENT HEAT LOAD
           (NET SOLAR  RADIATION)
  Incident heat load (net solar radiation), H, is the
source  of  heat influx that  causes  the water
temperature  to  increase.  The amount of solar
radiation that is received by a stream from the sun
is determined primarily by: (1) latitude of the site,
(2)  time of  year,  and  (3)  time of day. These
variables  have  been  combined in figures  and
graphs and an estimated value of net solar radia-
tion in BTU/ft2-minute is  obtained.
                  STREAM
                 DISCHARGE
  The  magnitude  of the water temperature  in-
crease is determined in part by the volume of water
that is flowing in the stream. Discharge should be
measured during  the time of year when water
temperature is critical for pre-silvicultural activity
conditions. However,  if the  hydrology  analysis
(chapter III) indicates that there may be a signifi-
cant change in discharge during this critical time
period  following the silvicultural activity, the dis-
charge estimated by the hydrology analysis should
be  used.  Discharge is expressed  as cubic feet/
second.
             EXPOSED SURFACE
               AREA FLOWING
                   WATER
  Net solar radiation acts as a direct heat influx
only when the radiation strikes the exposed water
surface. Shading keeps this radiation from striking
the water surface. However, because streams are
generally not  completely shaded, some solar radia-
tion strikes the water  surface even  in the  un-
disturbed condition. Silvicultural activities  may
not completely expose the stream. Brush, shrubs,
noncommercial tree species, and/or trees remaining
after a portion of a stand is cut may provide some
shade. The surface area of a stream exposed by the
silvicultural activity  must be estimated in square
feet.
                                                          MAXIMUM POTENTIAL DAILY
                                                            TEMPERATURE INCREASE
  Maximum potential daily temperature increase
can be estimated by evaluating the factors noted
above: (1) net solar radiation, (2) discharge, and
(3) exposed surface area of flowing water. The es-
timated  temperature increase above the  pre-
silvicultural activity water temperature is given in
degrees  Fahrenheit.  This estimated  increase is
compared to  water  quality objectives for  stream
temperature.
                                             1.18

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                                       SUMMARY  OF
                     CHAPTER VIII: PROCEDURAL EXAMPLES
   An  example  is provided  to illustrate  the
 procedures that  have been  described in  the
 preceding  technical  chapters. Two hypothetical
 watersheds with proposed silvicultural activities,
 one in a rain-dominated area and one in a snow-
 dominated area, are presented. Each step in the
 various procedures is described,  along with the
 data needs and any subjective evaluation that is re-
 quired. Use of the control chapter is also illustrated
 to select preventive and mitigative controls.
                                       SUMMARY  OF
         CHAPTER IX: DISSOLVED OXYGEN AND ORGANIC  MATTER
   Silvicultural activities can potentially reduce the
 concentration of dissolved oxygen in the water to
 the lethal level for some aquatic species through in-
 troduction of organic materials and increased water
 temperatures. The state-of-the-art is such that it is
 not possible to rigorously quantify the impacts as-
 sociated with the introduction of organic material
 to the aquatic system. This chapter describes, in
general terms, the processes involved and identifies
situations which  may create undesirable  conse-
quences.
  Water temperature, elevation, aeration  poten-
tial, type of aquatic life present, and stream uses
are considered in the discussion. Essential control
measures can then be selected to protect the values
involved.
                                      SUMMARY OF
                               CHAPTER X: NUTRIENTS
  Nitrogen and phosphorus  are the  nutrients
generally cited as having the greatest potential for
impacting water quality in  a forest environment.
Streams may show symptoms of overenrichment if
there is a continuous supply of nutrients and sub-
stantial periods of low water flow, but generally
there  is  minimal opportunity  for  buildup of
nutrients in streams due to continual transport by
water.
  The  discussion in this  chapter places  major
emphasis  on  the sources  of  nitrogen and
phosphorus in the forest environment, the intracy-
cle processes in the forest, and the nitrogen and
phosphorus outputs from the forest.
  Models  for  predicting soluble  and  insoluble
nutrient losses from silvicultural activities are not
sufficiently developed  and tested  for general ap-
plication. Therefore, only qualitative guidelines are
given for  evaluating  soluable nutrient changes
within a system.
                                             1.19

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                                      SUMMARY OF
                     CHAPTER XI: INTRODUCED CHEMICALS
  Fertilizers  and  pesticides  (insecticides,  her-
bicides and fungicides) are chemicals  commonly
introduced into a watershed as part of silvicultural
activities.  Introduced fertilizers  enter a  water
course  by direct application  of fertilizer to the
water surface or by leaching and subsequent sub-
surface flow of dissolved compounds or decomposi-
tion products. The impact of  pesticides on water
quality depends primarily on the following five fac-
tors: (1) toxicity to man and aquatic organisms, (2)
mobility, (3)  persistence, (4)  accuracy of place-
ment, and (5) orientation to streams.
  This chapter is directed primarily to a discussion
of the types of pesticides and fertilizers used, and
to the types of impacts that have been observed on-
site and in the aquatic ecosystem. The disposition
of introduced chemicals in the forest environment
is discussed.  Because procedures for quantifying
the  impacts  have not been developed for general
application, no attempt has been made to quantify
control effectiveness.
                                            1.20

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                Chapter II

CONTROL OPPORTUNITIES
           this chapter was prepared by:

              W. Wayne Patton
      with major contributions from a committee
      including three silviculturists, two foresters,
       one logging engineer, one civil engineer,
        one hydrologist and one soil scientist

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                            CONTENTS
                                                              Page

INTRODUCTION	   H.l
DISCUSSION 	   H.2
   CONTROLS TERMINOLOGY	   H-2
   POTENTIAL RESOURCE IMPACTS 	   H.2
THE PROCEDURE	   H-5
   PROCEDURAL DESCRIPTION	   H.5
   SECTION A: SILVICULTURAL ACTIVITIES AND POTENTIAL
     RESOURCE IMPACTS  	   11.10
   SECTION B: POTENTIAL RESOURCE IMPACTS AND
     CONTROL OPPORTUNITIES	   11-13
     Control Opportunities For All Listed Resource Impacts	   11.13
     Control Opportunities For Aerial Drift and
       Application of Chemicals 	   II. 13
     Control Opportunities For Bare Soil 	   11.13
     Control Opportunities for Channel Gradient Changes	   11.14
     Control Opportunities For Compaction	   11.14
     Control Opportunities For Debris In Channel	   11.14
     Control Opportunities For Excess Water 	   II. 15
     Control Opportunities For Onsite Chemical Balance Changes	   11.15
     Control Opportunities For Slope Configuration Changes	   11.15
     Control Opportunities For Stream Shading Changes	   11.16
     Control Opportunities For Vegetative  Change	   11.16
     Control Opportunities For Water Concentration	   11.16
   SECTION C: CONTROL OPPORTUNITIES AND SIMULATION
     VARIABLES	   11.17
   SECTION D: CONTROL OPPORTUNITY DESCRIPTIONS	   11.56
LITERATURE CITED 	   11.67
APPENDIX E.A: EXAMPLES ILLUSTRATING VARIOUS USES OF THE
   CONTROL OPPORTUNITIES	   11.68
   EXAMPLE ONE — MITIGATIVE CONTROLS FOR A PREVIOUSLY
     DISTURBED SITE  	   11.68
   EXAMPLE TWO — CONTROLS IN THE FORMULATION OF
     SILVICULTURAL PLANS	   11.70
   EXAMPLE THREE — ADDING CONTROLS WHEN PLANS DO NOT
     MEET WATER QUALITY OBJECTIVES  	   11.72

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                             LIST OF FIGURES
Number                                                                 Page
II.1.   —Procedural flow chart for utilizing control opportunities	   II.4
II.A.l.—Example one procedure 	   11.69
II.A.2.—Example two procedure	   11.71
n.A.3.—Example three procedure	   11.73
                                   U.iii

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                                LIST OF TABLES
Number                                                                      Page

II.1. —Silvicultural and related  activities  and  associated  potential  adverse
         resource impacts	  11.10
II.2. —Potential resource impacts  and  the variables  within the simulation
         procedure affected by those impacts	  11.18
II. 3. —Control opportunities for all resource impacts and the variables within
         the simulation procedure affected by those controls	  11.20
II.4. —Control opportunities for aerial drift and application of chemicals and the
         variables within the simulation procedure affected  by those controls   11.22
II.5. —Control opportunities for bare soil and the variables within the simulation
         procedure affected by those controls	  11.24
II.6. —Control opportunities for channel gradient changes and the variables
         within the simulation procedure affected by those controls	  11.28
II.7. —Control  opportunities for compaction  and  the variables within  the
         simulation procedure affected by those  controls	  11.30
II.8. —Control opportunities for debris in channel and the variables within the
         simulation procedure affected by those  controls 	  11.34
II.9. —Control opportunities for  excess  water and the variables within  the
         simulation procedure affected by those  controls	  11.38
11.10.—Control  opportunities  for onsite  chemical  balance changes and  the
         variables within the simulation procedure affected  by those controls   11.40
n.ll.—Control opportunities for slope configuration changes and the variables
         within the simulation procedure affected by those controls	  11.42
11.12.—Control opportunities for stream  shading  and the variables within the
         simulation procedure affected by those  controls 	  11.46
11.13.—Control opportunities for vegetation changes and the variables within the
         simulation procedure affected by those  controls 	  11.48
11.14.—Control opportunities for water concentration and the variables within
         the simulation procedure affected by those controls	  11.50
                                        Il.iv

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                                      INTRODUCTION
  This chapter lists demonstrated, effective con-
trol practices and suggests ways to choose mixtures
of these and similar controls for the prevention and
mitigation of resource impacts. Because economic
and social analyses are not discussed in this hand-
book, the mixtures of controls presented  in this
chapter do  not represent a "Best  Management
Practice"  (BMP).  These control mixtures form
only the technical base for the BMP.
  Control measures can be prescribed for various
reasons,  including: (1) protection of site produc-
tivity,  (2) protection of capital investments, such
as roads and buildings, and (3) protection of water
quality. Many of the control practices can be used
for all three reasons. For this reason, it may not be
necessary to specifically  formulate  controls for
water quality if controls imposed for site protection
are adequate to meet water quality objectives.
                                               n.i

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                                        DISCUSSION
        CONTROLS TERMINOLOGY
  Distinction is made between three classes of con-
trols — procedural, preventive, and mitigative —
according to the method of operation. These terms
are further defined as:
  Procedural controls. — Procedural controls are
administrative actions  or  sanctions that result in
reduced generation of transport of pollutants. Ex-
amples:  enforcement  of  standards, bonding  of
operators.
  Preventive controls. — Preventive controls ap-
ply to the pre-implementation phase of an opera-
tion. These controls are planning oriented and in-
volve stopping or  changing a  planned  activity
before a pollution-causing disturbance is allowed to
occur. Example: the location of roads and landings
away from the stream.
  Mitigative controls. — Mitigative controls in-
clude vegetative, chemical or physical measures
which alter the response of the water-disturbing ac-
tivity after it has occurred. Example: the revegeta-
tion of disturbed areas.
     POTENTIAL RESOURCE IMPACTS


  A resource may be damaged by impacts upon it if
natural processes  are altered. Potential  resource
impacts are defined and the related processes are
discussed in the following paragraphs. These 11 im-
pacts are considered to be those most important in
terms  of  non-point  source  water pollution and
silvicultural  activities.  They  are  listed
alphabetically and not necessarily by order of im-
portance.
  Aerial drift and application of chemicals. —
Any chemical pesticides, herbicides, or fertilizers
allowed to fall or wash into a stream can affect dis-
solved  oxygen,  nutrient   levels,  and  other
characteristics of that stream.
  Bare soil. — Bare  soil is a result of reduction in
vegetative  ground  cover, rock, and litter. Some
bare soil  is unavoidable  as a result of silvicultural
activities.
  Bare soil can lead to reduced infiltration of water
into the soil profile caused by surface crusting and
the attendant soil compaction. This, in turn, can
cause surface runoff  and water concentration and
finally lead to  rill or gully erosion. In addition,
some changes in the  onsite chemical balance may
occur as a result of increased nutrient leaching and
a reduction in organic matter.

  Channel gradient  change. — A change in chan-
nel slope can alter energy relationships which,  in
turn, can cause channel scour deposition.  Debris
dams or improperly placed culverts in streams can
cause changes in  channel gradient.
  Compaction. — "Soil compaction is the packing
together  of soil particles by  instantaneous forces
exerted at the soil surface resulting in an increase
in soil density through  a decrease in pore  space.
This  loss  of pore  space  reduces  infiltration
capacity, and water movement through the soil is
slowed. Then surface runoff  may occur more fre-
quently  and may increase  in  volume. Erosion
begins; and, once begun, may be difficult to stop.
In a logging operation, the extent of compaction de-
pends on the type of equipment, the terrain over
which the logs are skidded or hauled, the frequency
of travel, and the type of soil and its moisture con-
tent." (Lull 1959).
  Debris in  channel. — Debris in the channel
refers to  those  obstructions in a stream channel
caused by silvicultural  activities. Such obstruc-
tions include debris dams (logs, slash,  rock, etc.),
fill slope encroachment from roads, or any material
deposited in  the  channel due to silvicultural ac-
tivities.
  Such obstructions can deflect flow  which can
erode streambanks. Debris can form dams and the
attendant  water  impoundment can  cause local
flooding. In addition, during high flow, debris can
float downstream, accumulate against bridges, and
become a threat to bridge safety. Introduction  of
vegetative  debris,  in particular needles or  leaves,
can increase Biochemical Oxygen Demand  (BOD)
(Currier  1974, Ponce 1974).  Encroachments and
debris dams can alter velocity, thereby  influencing
exposure time to solar radiation with  a resultant
water temperature increase.
  Excess water. — Excess water is the increase in
channel  flow resulting  from evapotranspiration
                                               H.2

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reduction due to canopy removal. Excess water can
also  be caused by reduced infiltration rates into
bare or compacted soil. This water results in in-
creased energy and consequent bank and channel
erosion.

  Onsite  chemical  balance changes.  —
Silvicultural  activity  can result  in  release  of
chemicals which, in turn,  may leach or wash into
streams,  thereby  affecting  nutrient  and
Biochemical Oxygen Demand (BOD) levels in the
water. For example, chemical balance changes may
result from burning,  excessive amounts of woody
material, or crankcase oil  spills.

  Slope  configuration changes. — Slope con-
figuration changes refer to  an alteration of the land
slope. This may occur  in  road building when cuts
and fills are constructed for the road base, contour
terracing, etc.  Slope  configuration  changes  can
weaken slopes, lead to mass failure, and intercept
subsurface flow.

  Stream shading changes. — Stream  shading
changes occur when  trees  and/or  understory
vegetation that contribute to the shading of water
in streams are removed. Exposing streams to direct
solar radiation increases water temperature.
  Vegetative change. — Vegetative change in-
cludes the removal  of vegetative ground  cover,
canopy cover, or a change in vegetative type.
  Vegetative  change has numerous potential ef-
fects,  including changes in evapotranspiration, soil
protection, soil mass movement, stream shading,
and water velocity of over-the-ground flow on dis-
turbed sites. These changes affect the  hydrologic
processes, surface erosion,  soil mass movement,
stream  temperature,  and  ditch  and stream
velocity. Vegetative manipulation may  also affect
stream nutrients.
  Water concentration.  — Water concentration
occurs when water is intercepted and allowed to
converge instead of infiltrating into the  soil or
spreading naturally. Water  concentration,  as  a
resource impact, is closely related to bare soil, com-
paction,  and excess water.  Concentrated  water
moves with greater force  than  does  the same
amount of water in sheet flow. Concentrated flow
may  cause rill  erosion,  thus  increasing  the
probability of gully erosion.
                                              n.s

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V
CONTROL
OPPORTUNITIES

                                                                                       REVIEW WATER
                                                                                     QUALITY OBJECTIVES
        DEFINED WATER
      QUALITY OBJECTIVES
   REVIEW WATER
QUALITY OBJECTIVES
                                                        XISTIN
                                                         SITE
                                                     CONDITIONS
                                 UNDISTURBED AREA;
                            AREA DISTURBED DUE TO NATURAL
                               OCCURRENCES PRESENTLY
                           CONTRIBUTING NON-POINT SOURCES
                             OF POLLUTION OR PREVIOUSLY
                            DISTURBED AREA THAT NO LONGER
                             HAS CONTRIBUTING NON-POINT
                               SOURCES OF POLLUTION
                   AREA DISTURBED DUE TO
                 MAN-CAUSED OCCURRENCES
                PRESENTLY CONTRIBUTING NON-
                POINT SOURCES OF POLLUTION
                                              CHOOSE AND APPLY
                                              MITIGATIVE CONTROL
                                                   MIXTURE
                 ATE
               QUALITY
              OBJECTIVES
               NOT MET
                                 MEASURE OR SIMULATE
                                EXISTING WATER QUALITY
                      MEASURE OR SIMULATE
                     EXISTING WATER QUALITY
                                                                                             ATE
                                                                                           QUALITY
                                                                                          OBJECTIVES
                                                                                           NOT MET
                                                                  WATE
                                                                 QUALITY
                                                               OBJECTIVES
                                                                   MET
    ATE
  QUALITY
OBJECTIVES
    MET
        WATER QUALITY
     OBJECTIVES PRECLUDE
     FURTHER DEGREDATION
   WATER QUALITY
OBJECTIVES PRECLUDE
FURTHER DEGREDATION
                                                  DEFINED PROPOSED
                                                SILVICULTURAL ACTIVITY
                               WATER
                               QUALITY
                             OBJECTIVES
                                MET
    SIMULATION OF POTENTIAL
     WATER QUALITY USING
     ANALYSIS PROCEDURES
SILVICULTURAL ACTIVITY IS
COMPATIBLE WITH WATER
  QUALITY OBJECTIVES
                                                                                                CHOOSE AND APPLY
                                                                                              PREVENTIVE CONTROLS
              ATE
            QUALITY
          OBJECTIVES
            NOT MET
             WATER QUALITY OBJECTIVES
           PRECLUDE FURTHER DEGREDATION
              OF THE WATER RESOURCE
                                                                                                CHOOSE AND APPLY
                                                                                               MITIGATIVE CONTROLS
                                                  REVIEW WATER
                                                QUALITY OBJECTIVES
                            Figure 11.1.—Procedural flow chart for. utilizing control opportunities.

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                                    THE PROCEDURE
  To meet established water quality objectives, ex-
isting water quality  must be known.  Then, the
proposed silvicultural activity must be evaluated
and the water quality that would result from it es-
timated. By comparing the water quality objectives
with the existing and estimated water resource con-
ditions, the degree and type of control necessary to
meet the objectives can be determined.
  The overall strategy for assessing and evaluating
alternative control opportunities is described using
a procedural flow diagram (fig. II. 1), with a verbal
description of the procedure.  The controls
procedure explains how to use the four major por-
tions of the control information in the handbook's
simulation procedure. Section A  relates  various
silvicultural activities to  the  potential  adverse
resource impacts that may be associated with each
activity.  Section B suggests control opportunities
for each potential resource impact. Section C in-
dicates the relationship between resource impacts
and simulation variables, and between control op-
portunities and the simulation variables. Section D
describes all control opportunities in more detail.
Appendix II. A presents three cases illustrating how
to use the control information in relation to the
overall use of this handbook.
       PROCEDURAL DESCRIPTION
  The  following  paragraphs  describe  the
procedural flow chart in more detail. The indicated
numbers do not represent sequential steps, but act
as points of reference back to the flow chart, figure
11.1.
change must be compared with water quality ob-
jectives.
               DEFINED WATER
            QUALITY OBJECTIVES
                      1
  Prior to any evaluation of the potential change in
the water resource due to a proposed silvicultural
activity,  water  quality objectives  must  be
specified. These objectives  are generally  es-
tablished by legislative or regulatory authority. To
ascertain if a potential change caused by a
proposed silvicultural activity is acceptable, the
                  EXISTING
                    SITE
                CONDITIONS
                      2
  At this point, a decision must  be  made  as to
whether any disturbance in a watershed is natural
or man-caused.
  The  existing condition  of  the  water resource
before  any proposed  silvicultural activity  takes
place must be determined through the use of aerial
photos, historical records, or on-the-ground obser-
vations.
             UNDISTURBED AREA,
             AREA DISTURBED BY
           NATURAL OCCURRENCES
    PRESENTLY CONTRIBUTING NON-POINT
         SOURCES OF POLLUTION, OR
        PREVIOUSLY DISTURBED  AREA
    THAT NO LONGER HAS CONTRIBUTING
     NON-POINT SOURCES OF POLLUTION
                      3
  The water resource condition in areas that have
never been subjected to man-induced disturbances
and in areas that have at one time been disturbed
but have recovered sufficiently and no longer have
contributing  non-point sources  of pollution  is
determined by the  existing  vegetation, soil, and
geology. This represents the natural base condition
of the water resource.
           MEASURE OR SIMULATE
          EXISTING WATER QUALITY
                      4
  Existing water quality should be measured using
a sampling scheme that enables the water quality
                                              n.s

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parameters of interest to be evaluated. If measured
data are not available and cannot be feasibly col-
lected, the existing condition can be estimated us-
ing analysis  procedures presented in subsequent
chapters or locally derived methods.
              WATER QUALITY
                OBJECTIVES
                  NOT MET
                      5
                   WATER
                  QUALITY
                OBJECTIVES
                    MET
                      8
                                                   If the existing water resource  condition meets
                                                 water quality objectives,  a  proposed silvicultural
                                                 activity plan can be formulated.
  The existing water quality is compared with the
water quality objectives. If the existing condition
exceeds the objectives, further evaluation  is re-
quired.
     AREA DISTURBED BY MAN-CAUSED
 OCCURRENCES PRESENTLY CONTRIBUTING
    NON-POINT SOURCES OF POLLUTION
                      9
               REVIEW WATER
            QUALITY OBJECTIVES
                      6
  First of two possible actions.
  If the existing condition of the water resource
does not meet the objectives, the objectives should
be reviewed  and possibly  revised by  the ap-
propriate authority.
  The water quality in areas that have been sub-
jected to man-induced disturbances may be deter-
mined in great part by the non-point source pollu-
tion coming from  the  disturbed  sites.  It  is,
therefore, necessary to evaluate the impact of these
contributing non-point  sources  to  ascertain
whether the existing water quality objective is be-
ing met.
        WATER QUALITY OBJECTIVES
     PRECLUDE FURTHER DEGRADATION
                      7
  Second action.
  Because the objectives are presently exceeded by
the  existing water  resource  condition,  no
silvicultural activity should  be considered  that
would  result in  any further degradation. Alter-
native land use management of the watershed may
be necessary.
      MEASURE OR SIMULATE EXISTING
              WATER QUALITY
                     10
  Existing water quality should be measured using
a sampling scheme that enables the water quality
parameters of interest to be evaluated. If measured
data are not available and cannot be feasibly col-
lected, the existing condition of the water resource
can  be estimated by using analysis procedures
presented in subsequent chapters or locally derived
methods.
                                             H.6

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                    WATER
             QUALITY OBJECTIVES
                   NOT MET
                       11
   The existing water quality is compared with the
 given water  quality  objectives.  If the existing
 quality exceeds the objective, further evaluation is
 required.
                   IDENTIFY
                  RESOURCE
                   IMPACTS
                       12
   First of three possible actions.
   If  a  previous  disturbance  is impacting  water
 quality so that objectives are not met, the simula-
 tion or measurement will show where the pollution
 is originating, how much pollution is present, and
 what kind of pollution is  being produced.  Using
 this information, determine which variables within
 the simulation procedure are causing the pollution.
 Then refer to section C, table II.2 of this chapter
 and  relate  the  involved  variables to  the cor-
 responding resource impacts. (To relate resource
 impacts to the  involved processes, refer to  the
 definitions of the resource impacts in the "Discus-
 sion" section of this chapter.)
   For an example illustrating this use of the con-
 trols procedure, refer to example one in appendix
 II.A.
             CHOOSE AND APPLY
             MITIGATIVE CONTROL
                   MIXTURE
                      13
  Using the list of affected variables involved, refer
to section B or section C (tables II.3 to 11.14)  in
order to choose controls potentially able to mitigate
the  impact. The controls procedure is used  to
prescribe mitigative controls  for a previously dis-
turbed site  so the  proposed  silvicultural activity
may be accomplished without exceeding the water
quality objectives.  This procedure should be run
several times, thereby arriving at several choices
for the manager.  For an example illustrating this
 use of the controls procedure, refer to example one
 in appendix II.A.
                REVIEW WATER
            QUALITY OBJECTIVES
                      14
  Second of three possible actions.
  If existing water quality does not meet the objec-
tives after all feasible mitigative controls have been
selected, these objectives  should be reviewed and
possibly changed by the appropriate authority.
        WATER QUALITY OBJECTIVES
     PRECLUDE FURTHER DEGRADATION
                      15
  Third of three possible actions.
  Because the  water resource goals or standards
are presently being exceeded and the application of
mitigative controls cannot correct the problem and
objective revision is unacceptable, no silvicultural
activity should  be considered that would result in
any further degradation of  the water  resource.
Alternative land use management of the watershed
may be necessary.
                   WATER
                   QUALITY
              OBJECTIVES MET
                      16
                                                     If the existing water quality meets the objectives,
                                                   a silvicultural activity plan can be formulated.
                   DEFINE
         PROPOSED SILVICULTURAL
                  ACTIVITY
                      17
  Define the silvicultural activity and, depending
upon the size and complexity of the activity, such
                                               II.7

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things as a cutting plan, logging plan, transporta-
tion plan, fuel management plan, and site prepara-
tion may be included in the operational  plan.
  The control procedure can be used as a reference
in the formulation of the initial silvicultural plan.
Refer to table II.1 for a list of silvicultural activities
and related potential resource  impacts. For an ex-
ample  illustrating this use of the   controls
procedure, refer to example two in appendix II.A.
  Preventing  pollution is vastly  more  effective
than  mitigating problems after they are created.
Proper planning  and a thorough analysis of the
available options  will allow the manager to choose
the alternatives which best fit the management ob-
jectives, while minimizing non-point  source pollu-
tion potentials and the need for mitigative control.
     SIMULATION OF POTENTIAL WATER
               QUALITY USING
           ANALYSIS PROCEDURES
                      18
  The potential condition of the water resource, as-
suming  implementation  of  the  proposed
silvicultural  operation,  may be simulated using
analysis procedures. Such  analysis estimates the
potential impacts of the  silvicultural  operation
upon the water resource.
  The control procedure can be used in the process
of determining what variables are affected by what
controls in the simulation process.
                    WATER
                   QUALITY
                 OBJECTIVES
                   NOT MET
                      19
  The potential  water quality  following  the
proposed silvicultural activity is compared with
the given water quality  objectives. If these objec-
tives are exceeded, the  proposed silvicultural ac-
tivity should be reconsidered.
                   IDENTIFY
                  RESOURCE
                   IMPACTS
                      20
  First of three possible actions.
  If the proposed silvicultural plan is impacting
water quality  so that objectives are not  met,  the
simulation  will  show  where the  pollution is
originating,  how  much pollution is present, and
what  kind of  pollution is being produced. Using
this information, determine which variables within
the simulation procedure are causing the pollution.
Then refer to section C, table II.2 and relate the in-
volved variables to the corresponding resource  im-
pacts. (To relate resource impacts to the involved
processes, refer to the definitions of the resource
impacts  in the  "Discussion" section  of  this
chapter.)
  For an example illustrating this use of the con-
trols procedure, see example three, appendix II.A.
                                                                CHOOSE AND APPLY
                                                              PREVENTIVE CONTROLS
                                                                         21
  The controls procedure can be used to add new
control opportunities to the silvicultural plan if the
plan has been shown through  simulation  to fall
short of the objective. Refer to section C (tables II.3
to 11.14) and relate the affected variables to poten-
tial preventive controls. Preventive controls are
preferable  over  mitigative  controls,  thus the
procedure  indicates further  simulation with
preventive  controls before  trying mitigative con-
trols.
  For an example illustrating this use of the con-
trols procedure, see example three in  appendix
H.A.
                                                                CHOOSE AND APPLY
                                                               MITIGATIVE CONTROLS
                                                                         22
  If, after incorporating all feasible preventive con-
trols, the water  quality objectives are still ex-
ceeded, mitigative controls should be evaluated.
                                               H.8

-------
  For an example illustrating this use of the con-
trols procedure, refer to example three, appendix
H.A.
               REVIEW WATER
            QUALITY OBJECTIVES
                     23
  Second of three possible actions.
  If, after all  feasible preventive and mitigative
controls have  been applied, the potential water
quality resulting from the proposed silvicultural
operation  exceeds  the  water quality  obejctives,
these objectives should be reviewed and possibly
changed by the appropriate authority.
tive and mitigative controls have been applied, no
silvicultural activity should be considered for the
area at present. Alternative land use management
of the watershed may be necessary.
                   WATER
                  QUALITY
                 OBJECTIVES
                     MET
                     25
  The existing water quality is compared with the
given water  quality objectives.  If the existing
quality exceeds these objectives, further evaluation
is required.
        WATER QUALITY OBJECTIVES
     PRECLUDE FURTHER DEGRADATION
         OF THE WATER RESOURCE
                      24
         SILVICULTURAL ACTIVITY IS
         COMPATIBLE WITH WATER
            QUALITY OBJECTIVES
                      26
  Third of three possible actions.
  Because the potential water quality  resulting
from  the implementation  of  the  proposed
silvicultural  activity  might exceed  the water
resource objectives even after all feasible preven-
  The proposed silvicultural activity is compatible
with  the  water quality objectives and may be
implemented insofar as the water resource is con-
cerned.
                                              n.9

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SECTION A: SILVICULTURAL ACTIVITIES
  AND POTENTIAL RESOURCE IMPACTS
  This  section provides  a  simple  table  with
silvicultural activities listed in one column and the
potentially adverse resource impacts resulting from
each  silvicultural activity  listed  in  the second
column (table ILL). The list  of potential impacts
associated with particular silvicultural activities is
suggested for initial consideration but may need to
be revised according to local  conditions.
  Silvicultural activities listed are:
   1. Methods of cutting
   2. Felling
   3. Yarding methods
   4. Road and access system
   5. Fuel management methods
   6. Site preparation
   7. Other activities
    Adverse resource impacts include:
     1.  Aerial drift and application of chemicals
     2.  Bare soil
     3.  Channel gradient changes
     4.  Compaction
     5.  Debris in channel
     6.  Excess water
     7.  Onsite chemical balance changes
     8.  Slope configuration changes
     9.  Streamside shading changes
    10.  Vegetative change
    11.  Water concentration


    Table II.1 can be used in two ways  —
     1.  In  the formulation of the silvicultural  ac-
        tivity plan.
     2.  In the process of determining what variables
        are affected  by what controls when running
        the handbook simulations.
                    Table 11.1.—Silvicultural and related activities and associated potential
                                      adverse resource impacts
            Activities
Potential adverse resource impacts
            Methods of cutting:
                Clear-cutting	
                Seed tree cutting	{   i  Excess water
                Selection cutting	/   {  Streamside shad ing changes
                Shelterwood cutting	)   (  Vegetative change


            Felling  	    /  Debris in channel
                                                  \  Vegetative change

            Yarding methods:
                Hand pulpwooding	      Compaction

                Animal skidding	     Bare soil
                Tractor skidding	}     Compaction
                                                    Water concentration

                Cable yarding—high lead	    J  Bare soil
                                                  \  Water concentration

                Cable yarding—skyline  	    )  Bare soil
                                                  )  Slope configuration changes

                Cable yarding—balloon 	      Bare soj|

                Aerial skidding 	      Qnsite chemica| ba,ance changes

                                                    Bare sol I
                Mechanized logging	      Compaction
                  (feller, buncher, etc.)                 Water concentration
                                               n.io

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                              Table 11.1—continued
Activities
Potential adverse resource impacts
Road and access system:                   Aer|f'drift and application of
                                           chemicals (dust)
                                         Bare soil
     Construction and maintenance ....      Channel gradient changes
                                         Compaction
                                         Debris in channel
                                         Slope configuration changes
                                         Vegetative change

Fuel management methods:
                                       (  Bare soil
     Burying slash	    J  Compaction
                                       /  Slope configuration changes


                                         IBare soil
                                         Compaction
                                         Slope configuration changes
                                         Water concentration


                                         Aerial drift and application of
                                           chemicals (ash)
     Broadcast burning	      Bare soil
     Hand piling and burning 	      Compaction
     Machine piling and burning 	      Debris in channel
     Prescribed underburning	      Excess water
     Jackpot or spot burning 	      Onsite chemical balance changes
                                         Vegetative change
                                         Water concentration


     Yarding unmerchantable               Bare soil
      material 	      Compaction
                                         Debris in channel

     Lop and scatter	      Debris in channel


                                         Compaction
     Rolling chopper	      Onsite chemical balance changes
                                         Vegetative change


     Chip and spread	,   (  Compaction
     Masticate	}   1  Debns in cna™el
                                       (  Onsite chemical balance changes
Site preparation:

                                         Bare soil
                                         Compaction
     Dozer stripping	      Excess water
                                         Slope configuration changes
                                         Vegetative change
                                         Water concentration


                                         Bare soil
    Terracing  	    J  Compaction
                                         Excess water
                                         Slope configuration changes
                                    n.n

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                              Table 11.1.—Continued
 Activities
Potential adverse resource impacts
    Machine scalping	     / Bare soil
                                        ^ Compaction


    Bedding 	     / Baresoil
                                        I Water concentration


                                         Baresoil
    Plowjng                              Debris in channel
    Disking	}    Slope configuration changes
                                         Vegetative change
                                         Water concentration

                                         Baresoil
    Drags                                Compaction
                                         Vegetative change
                                         Water concentration

    Drainage	     (Baresoil
                                        | Water concentration

                                        / Aerial drift and application of
    Chemical treatment	     /   chemicals
                                        J Debris in channel
                                        ' Vegetative change

Other Activities:

    Mechanized planting	    / Compaction
                                       ^ Water concentration
    Release from plant competition-
      Fire  	      See broadcast burning


      Chemical 	    | Aerial drift and application of
                                       \ chemicals

      Mechanical 	    / Compaction
                                        | Water concentration
    Thinning and cleaning-

      Hand 	    / Debris in channel
                                        \ Vegetative change

                                        ( Compaction
      Mechanized	     } Debris in channel
                                        ( Vegetative change


    c«,rt!ii,o.i~                           ( Aerial drift and application of
    Fertilization	   I cnemicals
    Seeding with treated seeds  	\   < Onsite chemical ba|ance changes
                                       ' Vegetative change
                                    H.12

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   SECTION B: POTENTIAL RESOURCE
               IMPACTS AND
       CONTROL OPPORTUNITIES
  This section provides a list of potential adverse
resource impacts in alphabetical order followed by
a list of suggested controls that may alleviate each
particular impact. Control  opportunities  ap-
plicable to all listed resource impacts are presented
first. For  a description of each control measure,
refer to "Section D: Control Opportunity Descrip-
tions"  in this chapter.
  This section can be used in three ways.
  1.  In the prescription of mitigative controls for a
     previously disturbed site. (See example one,
     appendix II.A).
  2.  In the formulation of the silvicultural activity
     plan.  (See example two, appendix II.A.).
  3.  In the prescription of a mixture of preventive
     and mitigative controls for the alteration  of
     the silvicultural activity plan so it will meet
     established goals. (See example three, appen-
     dix H.A).
          Control Opportunities For
         All Listed Resource Impacts
Conformance to regulations (Procedural)
Enforcement of standards and bonding of operators
  (Procedural)
Limit disturbed area (Procedural)
Monitoring (Procedural)
Road  drainage  maintenance   during storms
  (Procedural)
Select low impact equipment (Preventive)
Specify timing (Procedural)
Timely drainage maintenance (Preventive)
  Control Opportunities For Aerial Drift And
           Application Of Chemicals
Chemical application (Preventive)
Control  ash  or  dust  buildup  (Preventive/
  mitigative)
 Keep pesticides and rodenticides well away from
   surface runoff (Preventive)
 Revegetate treatment areas promptly as local
       conditions dictate (Mitigative)
 Timing of chemical applications (Preventive)
 Waterside area (Preventive)

      Control Opportunities For Bare Soil
 Administrative   closure   of    roads
   (Procedural/preventive/mitigative)
 Appropriate cross-section in roads (Preventive)
 Armoring (Preventive/mitigative)
 Avoid reading steep slopes (Preventive)
 Brush barrier filter at the toe of fill (Preventive/
   mitigative)
 Close roads after use (Procedural/mitigative)
 Cut-and-fill slope configuration (Mitigative)
 Directional felling (Preventive)
 Drainage above  cut slope (Preventive/mitigative)
 Endline  or fly  material  from  waterside  areas
   (Preventive/mitigative)
 Fill slope design  and locations (Procedural/preven-
  tive)
 Hold water onsite (Preventive/mitigative)
Identify soil and geologic characteristics and map
  sensitive areas (Procedural/preventive)
 Leave vegetation between strips  (Preventive)
Limit equipment operation (Preventive)
Machine or hand plant (Preventive)
Prescribe and execute burns under conditions that
  will not result in total  cleanup (Preventive)
Prescribe limits  for the amount of area  disturbed
  by equipment  (Preventive)
Prescribe yarding and skidding layout (Preventive)
Prevent  fire  spread  outside  treatment areas
  (Preventive)
                                              11.13

-------
Protect road  bare  surface  areas  with nonliving
  material (Mitigative)
Reduce log length (Preventive)
Reduce logging road density (Preventive)
Revegetate treated  areas promptly as local condi-
  tions dictate (Mitigative)
Slope length (Preventive)
Species selection (Preventive)
Stabilizing structures or cut slopes (Mitigative)
Type of site preparation treatment (Preventive)
Use maximum spacing and minimum strip width
  in site preparation (Preventive)
Waterside area (Preventive)
Windbreaks or uncut timber to prevent wind ero-
  sion (Preventive)
          Control Opportunities For
          Channel Gradient Changes
Armoring (Preventive/mitigative)
Bridges (Preventive)
Ditch checks (Mitigative)
Ditch maintenance (Procedural/mitigative)
Maintain natural water courses (Preventive)
Oversize ditch drain (Preventive)
Reduction of impounded water (Mitigative)
Repair and stabilize damaged areas (Mitigative)
Space culverts to control velocity (Preventive)

    Control Opportunities For Compaction

Administrative  closure  of  roads  (Proce-
  dural/preventive/mitigative)
Close roads after use (Procedural/mitigative)
Directional felling  (Preventive)
Endline  or fly material  from  waterside  areas
  (Preventive/mitigative)
Identify soil and geologic characteristics and map
  sensitive areas (Procedural/preventive)
Leave vegetation between strips (Preventive)
Limit equipment operation (Preventive)
Machine or hand plant (Preventive)
Prescribe limits for the amount of area disturbed
  by equipment (Preventive)
Prescribe yarding and skidding layout (Preventive)
Reduce logging road density (Preventive)
Reduce vehicle travel (Preventive)
Revegetate treated areas promptly as local condi-
  tions dictate (Mitigative)
Rip or scarify compacted surfaces (Mitigative)
Road and landing location (Preventive)
Species selection (Preventive)
Timing of  use of  off-road,  heavy equipment
  (Preventive)
Type of site preparation treatment  (Preventive)
 Control Opportunities For Debris In Channel

Bench cut and compact fill (Preventive/mitigative)
Bridges (Preventive)
Brush barrier filter at the  toe of fill (Preventive/
  mitigative)
Directional felling (Preventive)
Eliminate source of debris  (Mitigative)
Endline  or  fly material  from  waterside  areas
  (Preventive/mitigative)
Fill  slope  design  and  location  (Procedural/
  mitigative)
Full bench section (Preventive)
Haul woody material offsite (Mitigative)
Limit equipment operation (Preventive)
                                              11.14

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Locate activities producing small, woody fragment
   away from water (Preventive)
Locate corrals away from streams (Animal skid-
   ding) (Preventive)
Maintain ground cover (Preventive)
Protect road  bare surface  areas  with nonliving
   material (Mitigative)
Remove debris from stream (Mitigative)
Repair and stabilize damaged areas (Mitigative)
Revegetate treated areas promptly as local condi-
   tions dictate (Mitigative)
Road and landing location (Preventive)
Waterside area (Preventive)
Woody debris disposal sites (Preventive)
   Control Opportunities For Excess Water
Cutting block design (Preventive)
Identify soil and geologic characteristics and map
  sensitive areas (Procedural/preventive)
Machine or hand plant (Preventive)
Maintain ground cover (Preventive)
Outslope firebreak lines and terraces (Preventive)
Prescribe and execute burns under conditions that
  will not result in total cleanup (Preventive)
Revegetate treated areas promptly as local condi-
  tions dictate (Mitigative)
Species selection (Preventive)
Type of site preparation treatment (Preventive)
Use maximum  spacing and minimum strip width
  in site  preparation (Preventive)
Waterside area (Preventive)
          Control Opportunities For
      Onsite Chemical Balance Changes
Chemical application (Preventive)
Control  ash  or dust  buildup  (Preventive/
  mitigative)
Haul woody material offsite (Mitigative)
Identify soil and geologic characteristics and map
  sensitive areas (Procedural/preventive)
Keep pesticides and rodenticides well away from
  surface  runoff (Preventive)
Locate  corrals  away from streams  (Animal skid-
  ding) (Preventive)
Machine or hand plant (Preventive)
Pile material in patterns  (Preventive)
Protect fuel storage areas (Preventive)
Revegetate treated areas promptly as local condi-
  tions dictate  (Mitigative)
Species selection (Preventive)
Type of site preparation treatment  (Preventive)
Woody  debris disposal sites (Preventive)
          Control Opportunities For
         Slope Configuration Changes
Appropriate cross-section for roads (Preventive)
Avoid reading of steep slopes (Preventive)
Bench cut and compact fill (Preventive/mitigative)
Break gradient of firelines (Preventive/mitigative)
Divert water onto stable areas (Preventive)
Drainage above cut slope (Preventive/mitigative)
Full bench section (Preventive)
Identify soil and geologic characteristics and map
  sensitive areas (Procedural/preventive)
Limit equipment operation (Preventive)
Machine or hand plant (Preventive)
Maintain ground cover (Preventive)
Prescribe yarding and skidding layout (Preventive)
Reduce logging road density  (Preventive)
Reduction of impounded water (Mitigative)
                                              H.15

-------
Revegetate treated areas promptly as local condi-
  tions dictate (Mitigative)
Road and landing location (Preventive)
Species selection (Preventive)
Stabilizing structures on cut slopes (Mitigative)
Type site preparation treatment (Preventive)
          Control Opportunities For
         Streamside Shading Changes
Cutting block design (Preventive)
Directional felling (Preventive)
Revegetate treated areas promptly as local condi-
  tions dictate (Mitigative)
Waterside area (Preventive)
 Control Opportunities For Vegetative Change

Cutting block design (Preventive)
Directional felling (Preventive)
Leave vegetation between strips (Preventive)
Machine or hand plant (Preventive)
Maintain ground cover (Preventive)
Prescribe limits for the amount of area disturbed
  by equipment (Preventive)
Revegetate treated areas promptly as local condi-
  tions dictate (Mitigative)
Species selection (Preventive)
Timing of chemical  application (Preventive)
Type of site preparation treatment (Preventive)

Control Opportunities For Water Concentration
Administrative   closure  of  roads  (Proce-
  dural/preventive/mitigative)
Armoring (Preventive/mitigative)
Avoid reading of steep slopes (Preventive)
Break gradient of firelines (Preventive/mitigative)
Close roads after use (Procedural/mitigative)
Curbs and berms (Preventive/mitigative)
Cut-and-fill slope configuration (Mitigative)
Cutting block design (Preventive)
Ditch  checks (Mitigative)
Ditch maintenance (Procedural/mitigative)
Divert water onto stable areas (Preventive)
Drainage above cut slopes (Preventive/mitigative)
Hold water onsite (Preventive/mitigative)
Identify soil and  geologic characteristics and map
  sensitive areas  (Procedural/preventive)
Leave  vegetation  between strips (Preventive)
Limit equipment operation (Preventive)
Machine or hand plant (Preventive)
Maintain natural water courses (Preventive)
Minimize convergence of firelines (Preventive)
Outslope firebreak lines and terraces (Preventive)
                         [
Oversize ditch drain (Preventive)
Pile material in patterns  (Preventive)
Prescribe limits for the amount of area disturbed
  by equipment (Preventive)
Prescribe yarding and skidding layout (Preventive)
Reduce road  grades (Preventive)
Reduce vehicle travel (Preventive)
Reduction of impounded water (Mitigative)
Remove debris from stream (Mitigative)
Repair and stabilize damaged areas (Mitigative)
Revegetate treated areas promptly as local condi-
  tions dictate  (Mitigative)
Rip or scarify compacted surfaces (Mitigative)
Road and landing location (Preventive)
Road ditch (Preventive/mitigative)
                                               11.16

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Sediment trap  (Mitigative)

Slope length (Preventive)

Space  culverts to  control  road  ditch  erosion
  (Preventive)

Species selection (Preventive)

Timing  of  use of  off-road, heavy equipment
  (Preventive)

Trash racks (Preventive)

Type of site preparation treatment (Preventive)

Use  maximum  spacing and  minimum strip width
  in site preparation (Preventive)

Waterside area (Preventive)
 SECTION C: CONTROL OPPORTUNITIES
      AND SIMULATION VARIABLES


  The matrices (tables n.2 to 11.14) in this section
are the cross-reference system between the "control
opportunities"  and  the  handbook simulation
procedure (chapters HI through XI).
  This section lists all variables used in the hand-
book  simulation  procedure along the horizontal
axis  of the  matrices. Some  of these variables
change only with a change in location or area, for
example, the R or rainfall factor in  the Modified
Soil Loss Equation. Other variables are measured
values like bedload sediment in the total sediment
procedure. The remaining variables (the ones of
concern in this  chapter)  can  be affected,  either
positively  or negatively, by certain controls.
  All controls, therefore, are listed along the ver-
tical axis of the matrices (tables II.3 to 11.14). The
controls are listed under each resource impact they
are associated with. The "X" symbols on the tables
indicate  which  controls affect  which  variables.
These "X's" are placed with reference to the way
the  variable is  being  used  in the  simulation
procedures.  For example, the variable "Type and
location of the cut" has a specific definition. The
use of this variable  is to identify the hydrologic
processes  (i.e., evapotransporation and  snowpack
changes) as they affect  streamflow  and not the
related effects on silvicultural activity such as site
preparation.
  The names of the controls and the "X's" on the
tables  are  designed to  represent  most  major
relationships and, therefore, some specific controls
and their relationships to variables  may not be
covered.
  Table n.2 is a summary showing which simula-
tion variables are affected  by which  resource im-
pacts. The other 12 tables show  which simulation
variables are affected by which controls. Table n.3
shows  control opportunities for all resource im-
pacts. These controls should be considered in any
silvicultural activity  plan.

NOTE: In the process of selecting a mixture of con-
  trols to mitigate or prevent a specific resource
  impact, the effects of  the selected controls on
  other areas of concern must be realized. For ex-
  ample, if, through simulation, a problem is noted
  with surface erosion related to road surfaces, the
  control lists under "Bare Soil," "Compaction,"
  and "Water Concentration" would be referred to.
  A control frequently used to prevent water flow
  across  road surfaces is "Drainage  Above Cut
  Slope." But, in  addition to preventing surface
  flow, it also affects slope configuration which in-
  dicates that drainage ditches above the cut slope
  could cause soil mass movement problems.
                                               E.17

-------
                     Table 11.2—Potential resource impacts and the variables within the
                              simulation procedure affected by those impacts







Resource impacts

Aerial drift and applica-
tion of chemicals
Bare soil
Channel gradient
change
Compaction
Debris in channel
Excess water
Onsite chemical balance
changes
Slope configuration
change
Stream shading change
Vegetative change
Water concentration
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)


I
CD
CD













X


«^>
Type and location c

















f
0>
•o
0>
1
DC
















+*
1
O)
•o
J^

CO











X





K (Soil credibility)





X









*-
0>
0>
O)
?
VM (Vegetation-mai

X
X


X







X


2?
Ground cover dens

X
X










X



Ł
1
Ł
~5
CO

















Surface water flux


X


X

X





X
X


0)
1
o>
o
§
CO











X





Surface roughness

















Distance

















o>
o.
0)
(0
o
Q.
o
en











X



Ditch
erosion
(ch. IV)
(app.
IV-C)


m
3
1
.
CC






X
X






X

_

•D
i

















Slope gradient











X




O
«
Drainage character











X





Slope configuration











X





Vegetative cover


X









X
X



o
•j=
3
a
Ł
a
~a
c
<















0
Ł
3
•o
08
>.
~tn
1
c
E
o
35

















Parent material1

















Natural landslides1















1 Measured value.
"Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter  III
5See "Soil Mass Movement," chapter V
•Can be taken from chapter III or measured directly.
'Calculated value.
                                                  11.18

-------
Table 11.2—continued
Resource impacts
Aerial drift and applica-
tion of chemicals
Bare soil
Channel gradient
change
Compaction
Debris in channel
Excess water
Onsite chemical balance
changes
Slope configuration
change
Stream shading change
Vegetative change
Water concentration
Chapter references to the simulation procedure and affected variables
Total sediment
variables
(ch.VI)
Bankful width-depth |




X






S
0
CO
8
I
s
a


X

X






Change in discharge or duration4





X




X
Bankful discharge7











Suspended sediment1











Bedload sediment1











Surface erosion sediment3











Fines-mass movement8











Coarse material-mass movement5











Median size material-mass movement5











Stream
temperature
variables
(ch. VII)
O)
CO
1
1








X
X

o
CO
Ł
0)
CO
o
Q.
X
D


X

X



X
X

Location-latitude1











Year-day-month1











Stream width1











Discharge6











Bedrock1











Azimuth1











Topographic -slope1











Dissolved
oxygen &
organic
matter
(ch. IX)
Nos
cons
eai
X



X

X




Nutrients
(ch.X)
pecific vari
ider effects
ch total sub
X



X

X




Introduced
chemicals
(ch. XI)
ables,
upon
ject
X



X

X




         n.i9

-------
       Table II.3—Control opportunities for all resource impacts and the variables within the simulation
                                   procedure affected by those controls








Control opportunities
for
all resource impacts

Conformance to
regulations
Enforcement of stand-
ards and bonding
of operators
Limit disturbed area
Monitoring
Road drainage mainten-
ance during storms
Select low impact
equipment
Specify timing
Timely drainage
maintenance
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




_
CO
"5
0

X


X
X
X




X




D
o

o
1
o
o
•o
,
1—

X


X
X
X



X
X






f

•a
o>
c
1
cc

X


X
X
X



X
X




+-
c

O)
T3
^
0)
in
_3_
>.
1

I
co
_i

X


X
X
X



X
X






(Soil erodibility)
*

X


X
X
X

X

X
X


^^
0)
E
0)
o>
p
M (Vegetation-ma
>

X


X
X
X

X

X
X





#
round cover dens
O

X


X
X
X

X

X
X






Ł
1
'o
CO

X


X
X
X

X

X
X






X
_2
^
S
CO
0)
o
S
k.
3
CO

X


X
X
X

X

X
X

X




0>
TO
CD
0)
a
o
CO

X


X
X
X



X
X






urface roughness
CO

X


X
X
X

X

X
X






S
To
Q

X


X
X
X



X
X






0>
Q.
CO
Ł
OT
a
o
CO

X


X
X
X



X
X


Ditch
erosion
(ch. IV)
(app.
IV-C)




(Hydraulic radius
cc

X


X
X
X

X

X
X

X



.— ,
(Slope of channe
CO

X


X
X
X

X

X
X

X




(Friction factor)
z

X


X
X
X

X

X
X

X

Soil mass
movement
variables
(ch.V)




Ł
Q.
CD
T3
'5
CO

X


X
X
X



X
X






lope gradient
CO

X


X
X
X

X

X
X




(0
o
to
rainage character
o

X


X
X
X

X

X
X






lope configuration
CO

X


X
X
X



X
X






egetative cover
>

X


X
X
X

X

X
X






nnual precipitatior
<















o
la

•o
oe
I
S
c
E
0
CO


















arent material1
0.


















atural landslides1
z














1 Measured value.
2Changes only with location.
3See "Surface  Erosion," chapter IV
4See "Hydrology," chapter III
'See "Soil Mass Movement," chapter V
•Can be taken  from chapter III or measured directly.
'Calculated value.
                                                  11.20

-------
Table 11.3—continued













Control opportunities
for
all resource impacts






Conformance to
regulations
Enforcement of stand-
ards and bonding
of operators
Limit disturbed area
Monitoring
Road drainage mainten-
ance during storms
Select low impact
equipment
Specify timing
Timely drainage
mantenance
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)








§•
TJ
.C
TJ
s
I
c
m
m

X


X
X
X



X
X

X








CD
Q.
O
CO
CD
C8
L
-I
CO
1
•$.

X


X
X
X



X
X

X



f-
0
3
J
TJ
O
8,
CO
JC
TJ
-t
CD
r
0






















f*.
CD
P
O
CO
TJ
j=
c
ffl
m






















*-
CD
1
•o
CD
C

-1

X


X
X
X



X
X











U)
TJ
W

g
5
-1























Łi
*-•
C
u
-t,
CO
CO
>-
























TJ
5
E
CO
2
CO

























(D
CO
%
Q

























^.
0
•o
m


























.Ł
E
<






















s
o
OT
.2
f-
Q.
S)
CD
O
a
o















Dissolved
oxygen &
organic
matter
(ch. IX)







Nos



Nutrients
(ch. X)







lecific vari


Introduced
chemicals
(ch. XI)







ables
consider effects upon
each total subject







X


X
X
X

X

X


X







X


X
X
X

X

X
X

X







X


X
X
X

X

X
X

X
       11.21

-------
         Table 11.4—Control opportunities for aerial drift and application of chemicals and the variables
                               within the simulation procedure affected by those controls








Control opportunities
for
aerial drift and
application of chemicals
Chemical application
Control ash or dust
buildup
Keep pesticides and
rodenticides away from
surface runoff
Revegetate treatment
areas promptly
Timing of chemical
application
Waterside area
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




CO
Ł
00
s
CO
m













0
•«-
c
o
to
8
T3
C
CO
o>
Q.
>.















f
CO
T3
O>
C
*=
8
tr













c
(I)

0>
•o
1
><
CD
1










X




Latitude1














o
Seasonal precipitat















Width of opening1













c
n
CO
Normalized hydrogr













Surface erosion
variables
(ch. IV)




R (Rainfall)2















CD
a
o
m
•
|
CD
CO










X




K (Soil erodibility)










X
.*-
c
CD
CD
0)
1-
VM (Vegetation-ma
X






X

X
X



&
Ground cover dens
X






X

X
X




Ł
1
s.
"6
CO















Surface water flux
X








X
X




Slope gradient















Surface roughness










X




Distance










X




o>
a
a)
c.
co
«
a.
o
CO











Ditch
erosion
(ch. IV)
(app.
IV-C)




R (Hydraulic radius














— ~
o>
c
CO
c.
o
"o
0)
a
o
CO
CO















N (Friction factor)







X




Soil mass
movement
variables
(ch. V)




Ł
Q.
CD
•o
O
CO















Slope gradient













co
o
co
Drainage character















Slope configuration















Vegetative cover
X






X

X
X



•-
Annual precipitatior












c
o
S
3
Storm intensity & d















Parent material1















Natural landslides1











1 Measured value.
2Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
5See "Soil Mass Movement," chapter V
"Can be taken from chapter III or measured directly.
'Calculated value.
                                                   n.22

-------
Table 11.4—continued












Control opportunities
for
aerial drift and
application of chemicals






Chemical application
Control ash or dust
buildup
Keep pesticides and
rodenticides away from
surface runoff
Revegetate treatment
areas promptly
Timing of chemical
application
Waterside area
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch. VI)







.c
Q.



S
1
c
CO
ffi


















CD
U.
0
CO
o

CO
0>

_™
Ł













g
CO
^
•o
0
CD
O)
CO
c
-o

l_
CD
O)
CO
.c
o



















(D
1
U

T3
"5
"S.
c
CO
m


















c

•a


•O
10
3
CO



















c
CD
•o

CO
0
^
Q}
m















m
•p
CD
F
TJ
in
O
0

i
t
-j
CO

















s.
CD
CD
>


CO
0)
c
u.












„
c
i
>
o
<8
m
E
«
S
m
E
CD
CO
CO
Q
0











CD
F
I
E
CO
CO
E
CO
CD
CO
m
M
w
«
m
(D
^












Stream
temperature
variables
(ch. VII)








c'
«
CO

1
O)
Q)
>
X






X


X






-{=

91
1


1
4-*
m
r

_J










X








^
U)

m
o
4=
Q
Q
_l




















|
O
F
$
•o


>




















^


i
CO
CD
4=
CO























1
o
to
o























^
o
•o

m























|

N
^



















a
o
CO
o
p
Q.
2
O)
o
r>
o












Dissolved
oxygen &
organic
matter
(ch. IX)










Nutrients
(ch.X)









Introduced
chemicals
(ch. XI)







No specific variables
consider effects upon
each total subject






X




X



X
X






X

X


X



X
X






X

X


X



X
X
          11.23

-------
            Table  11.5—Control opportunities for bare soil and the variables within the simulation
                                    procedure affected by those controls
Control opportunities
for
bare soil
Administrative closure
of roads
Appropriate cross-
section for roads
Armoring
Avoid reading steep
slopes
Brush barrier filter at
the toe of fill
Close roads after use
Cut and fill slope
configuration
Directional felling
Drainage above cut slope
Endline of fly material
from waterside area
to upslope landing
Fill slope design and
location
Hold water onslte
Identify soil and geologic
characteristics and
map sensitive areas
Leave vegetation
between site
preparation strips
Limit equipment
operation
Machine or hand plant
Chapter references to the simulation procedure and affected variables
Hydrology
variables
(ch. Ill)
«
CD
CO
"55
in
as
m
















i
D
o
"o
o
1
o
T3
CO
CO
a
>.
















Rooting depth

X

X


X

X







Delivery (user judgment)








X


X

X


Latitude1
















Seasonal precipitation1
















Width of opening1
















Normalized hydrograph1
















Surface erosion
variables
(ch. IV)
OJ
To
"c
'to
CŁ
tr
















CO
Q.
0
CO
1
c.
*-»
O>
CD
CO
_l

X

X


X

X

X
X

X


K (Soil erodibility)
X




X

X

X
X

X

X
X
VM (Vegetation-management)
X

X


X

X

X
X
X

X
X
X
Ground cover density
X

X


X

X

X



X
X
X
CO
k_
3
1
5
CO












X



Surface water flux








X


X

X


Slope gradient

X

X


X



X





Surface roughness














X

Distance

X

X
X

X

X

X
X

X


CO
Q.
CO
co
CO
a
o
CO

X

X


X



X





Ditch
erosion
(ch. IV)
(app.
IV-C)
R (Hydraulic radius)

X




X

X

X



X

CD
C
c
CO
.c
o
"5
CO
Q.
0
CO
CO








X





X

N (Friction factor)


X





X







Soil mass
movement
variables
(ch.V)
c
Q.
CO
•o
5
CO












X



c
CO
2
0)
li
o
CO

X

X






X





Drainage characteristics

X

X


X

X

X
X




Slope configuration

X

X


X

X

X





Vegetative cover





X

X

X



X

X
Annual precipitation1
















Storm intensity & duration1
















Parent material1












X



Natural landslides1












X



'Measured value.
'Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
                                                   H.24

-------
                                          Table 11.5—continued
Control opportunities
for
bare soil
Administrative closure
of roads
Appropriate cross-
section for roads
Armoring
Avoid road ing steep
slopes
Brush barrier filter at
the toe of fill
Close roads after use
Cut and fill slope
configuration
Directional felling
Drainage above cut slope
Endline of fly material
from waterside area
to upslope landing
Fill slope design and
location
Hold water onsite
Identify soil and geologic
characteristics and
map sensitive areas
Leave vegetation
between site
preparation strips
Limit equipment
operation
Machine or hand plant
Chapter references to the simulation procedure and affected variables
Total sediment
variables
(ch. VI)
Bankful width-depth







X


X



X

Water surface slope







X






X

Change in discharge or duration4
















Bankful discharge7
















Suspended sediment1
















Bedload sediment1
















Surface erosion sediment3
















Fines-mass movement5
















Coarse material-mass movement5
















Median size material-mass movement5
















Stream
temperature
variables
(ch. VII)
Vegetative shading







X

X






Length-exposed reach
















Location-latitude1
















lc
4-1
c
1
T3
>
















Stream width1
















Discharge6
















Bedrock1
















Azimuth1
















Topographic slope1
















Dissolved
oxygen &
organic
matter
(ch. IX)
No
con
ei




X


X

X
X



X
X
Nutrients
(ch.X)
ipecific var
sider effectt
ich total sub




X


X

X
X



X
X
Introduced
chemicals
(ch. XI)
ables
tupon
ject




X


X

X
X



X
X
'See "Soil Mass Movement," chapter V
'Can be taken from chapter III or measured directly.
'Calculated value.
                                                    H.25

-------
Table 11.5—continued







Control opportunities
for
bare soil


Prescribe and execute
burns under condi-
ions that will not
result in total
cleanup
Prescribe limits for the
amount of area dis-
turbed by equipment
Prescribe yarding and
skidding layout
Prevent fire spread out-
side treatment areas
Protect bare surface areas
with non-living material
Reduce log length
Reduce logging road
density
Revegetate treated areas
promptly as local
conditions dictate
Slope length
Species selection
Stabilizing structures
or cut slopes
Type of site preparation
treatment
Use maximum spacing
and minimum strip
width in site
preparation
Waterside area
Wind breaks or uncut
timber to prevent wind
erosion
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)





CO

—I
5







X

X




X

X



X
X



X



X
X






•s
._
S
'•o
8
0)
'6
CO







X

X




X

X




X



X




X



CD
E
m
CO
CO
E

VM (Vegetatior




X


X

X

X

X
X

X


X

X

X

X



X
X





2?

c
r
co
S
"o
Q)
Q.
O
CO
CO





































*C"
(J
N (Friction facl













X





X















Soil mass
movement
variables
(ch.V)





«-»
Q.
0)
•o
1







































Slope gradient







X








X



X














CO
o
0)
1

Drainage char;







X








X








X



X







c
g
CO
Slope configur







X








X








X












Q)
Vegetative cov




X


X

X

X







X

X

X

X



X
X





^
o
In
S
Annual precipi


































o
CM
-i
T3
00

Storm intensity






































Z_
Parent materia





































In
(1i
Tl
Natural landsli


































  11.26

-------
Table 11.5—continued
Control opportunities
for
bare soil
Prescribe and execute
burns under condi-
tions that will not
result In total
cleanup
Prescribe limits for the
amount of area dis-
turbed by equipment
Prescribe yarding and
skidding layout
Prevent fire spread out-
side treatment areas
Protect bare surface areas
with non-living material
Reduce log length
Reduce logging road
density
Revegetate treated areas
promptly as local
conditions dictate
Slope length
Species selection
Stabilizing structures
or cut slopes
Type of site preparation
treatment
Use maximum spacing
and minimum strip
width in site
preparation
Waterside area
Wind breaks or uncut
timber to prevent wind
erosion
Chapter reference* to the simulation procedure and affected variables
Total sediment
variable*
(ch.VI)
Bankful width-depth















Water surface slope















Change in discharge or duration4















Bankful discharge7















1
1
CO
3
CO















1
1
at
•a
a
o
*
m















Surface erosion sediment3















0
CO
3
ul















0
+*
I
E
i
3
1
0>
CO
O















Median size material-mass movement*















Stream
temperature
variables
(ch.VII)
Vegetative shading







X

X



X

1
p
3
g
1
s













X

Location-latitude1















Year-day-month1















|
1
E
]
a















Discharge*















Bedrock1















Azimuth1















Topographic slope1















Dissolved
oxygen &
organic
matter
(ch. IX)
Nosp
consh
eacl







X



X

X
X
Nutrients
(ch.X)
eciflc varla
tor effects
i total subj


\




X



X

X
X
Introduced
chemicals
(ch.XI)
bles
upon
set







X



X

X
X
        n.27

-------
     Table 11.6—Control opportunities for channel gradient changes and the variables within the simulation
                                   procedure affected by those controls






Control opportunities
for
channel gradient
changes
Armoring
Bridges
Ditch checks
Ditch maintenance
Maintain natural water
courses
Oversize ditch drain
Reduction of impounded
water
Repair and stabilize
damaged areas
Space culverts to control
velocity
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill]


Ł
<0
8
a
m













**
u
•5
§
1
8
•o
§
CD
Q.
>.















1
•o
o>
1















•o
1
Ł•
.1

s
CO















K (Soil erodibility)













+*
0)
s>
VM (Vegetation-mam
X














Ground cover density
X














Soil texture















Surface water flux








X






Slope gradient















Surface roughness















Distance

X













o>
a
CO
CO

|
u
•5
s.
0
CO
CO

X
X
X






X

X


N (Friction factor)
X

X
X






X



Soil mass
movement
variables
(ch.V)


1
•o
'5
CO















Slope gradient














•a
Drainage characterisi








X






Slope configuration















Vegetative cover















Annual precipitation1













I
?
Storm intensity & du















Parent material1















Natural landslides1













'Measured value.
Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
'See "Soil Mass Movement," chapter V
•Can be taken from chapter III or measured directly.
'Calculated value.
                                                  n.28

-------
Table 11.6—continued








Control opportunities
for
channel gradient
changes






Armoring
Bridges
Ditch checks
Ditch maintenance
Maintain natural water
courses
Oversize ditch drain
Reduction or impounded
water
Repair and stabilize
damaged areas
Space culverts to control
velocity
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch. VI)




Ł
Q.

?
XJ
S
.3
1
GO
X
X



X




X

X




8

CO
CO
CO

CD
2
Ł

X
X


X




X

X
•fc
o
1
TJ
O
CD
O)
CO

TJ
.C
CD
O)
CO
o

















h.
CD
n>
CO
8
TJ
.^
§
m
















-
c
E
"g
Tl
CD
TJ
c

Q.
CO
-)
CO


















c
E

CO
TJ

TJ
m















c
fl)

TJ

o
3
03
o
Ł
CO
















•Ł
E

o
CO
io
F
i
i
u.













%
CD
§
ft
i
E
2
1

m
§
O













M
C
o
CO
1
CO
T

F
s
'co
m

^














Stream
temperature
variables
(ch.VII)




m
c
3
•Ss
I
^
CD
S?
>
















Ł
«
k.


X

CO u (0 o o TJ CD m i ^ E 41 01 Q. ~Z O |c- a 2 O) o a. o Dissolved oxygen & organic matter (ch. IX) Nutrients (ch.X) Introduced chemicals (ch. XI) No specific variables consider effects upon each total subject X X X 11.29


-------
            Table II.7—Control opportunities for compaction and the variables within the simulation
                                    procedure affected by those controls








Control opportunities
for
compaction


Administrative
closure of roads
Close roads after use
Directional felling
Endlineorfly
material from water-
side areas to
upslope landings
Identify soil and
geology character-
istics and map
sensitive areas
Leave vegetation
between site-
preparation strips
Limit equipment
operation
Machine or hand plant
Prescribe limits for
the amount of
area disturbed by
equipment
Prescribe yarding and
skidding layout
Reduce logging road
density
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)





s
CO
CD




























3
O
*_
O
c
o
CO
8
T3
C
CO
CD
Q.
>-































SL
Q.
CD
T5
0>
i
DC




























C
Ł
0)
•o
k_
CO
_>
a














X










X





•o





























"r
n
1
'a
o
E
Q.
"cfl
C
O
CO
s
CO






























"b>
c
CD
a.
o
B
^
2
^




























JC
n
CO
O)
E
Tl
ormalized hy
z




























Surface erosion
variables
(ch. IV)





(Rainfall)2
DC






























•
o
CO
1
D)
CD
f(1















X






X

X

X




Ł•
n
T3
O
CD
'6
CO
^

X
X
X



X



X




X
X



X

X

X
c
CD
F
CD
0)
c
CO
E
1
M (Vegetatiol
>

X
X
X



X






X

X
X



X

X

X



^
'in
CD
•o
round cover
O

X
X
X



X






X

X
X



X

X

X





oil texture
CO











X


















X
urface water
CO














X








X







CD
TO
2
O)
CD
Q.
O
CO























X

X




8
CD
|-
C.
O)
o
0>
8
k_
->
CO
















X




X









istance
Q














X








X

X





CO
.c
CO
CD
a
o
CO























X

X
Ditch
erosion
(ch. IV)
(app.
IV-C)




co
3
'"2
(Hydraulic n
tr
















X












*- -.
Ł
c
CO
c.
o
•5
CD
Q.
O
CO
CO
















X













O
(Friction fac
z



























Soil mass
movement
variables
(ch. V)





Ł
a
CD
T3
'o
CO











X



















c
0)
CO
0)
a>
CO





















X



X


co
o
co
CD
B
m
rainage char
Q





















X



X




1
n>
3
0)
«•—
§
CD
Q.
o
CO





















X



X




CD
egetative cov
>



X



X






X


X



X

X





•-
o
M
a
'o
0)
Q.
To
c
c
<



























c
o

-)
•o
oO
C
«
c
E
o
CO






























^
arent materia
0.











X


















in
CD
T)
To
T3
I
75
k.
3
CO
Z











X














1 Measured value.
2Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
'See "Soil Mass Movement," chapter V
"Can be taken from chapter III or measured directly.
'Calculated value.
                                                  11.30

-------
Table 11.7—continued
Control opportunities
for
compaction
Administrative
closure of roads
Close roads after use
Directional felling
Endline or fly
material from water-
side areas to
upslope landings
Identify soil and
geology character-
istics and map
sensitive areas
Leave vegetation
between site-
preparation strips
Limit equipment
operation
Machine or hand plant
Prescribe limits for
the amount of area
disturbed by
equipment
Prescribe yarding and
skidding layout
Reduce logging road
density
Chapter references to the simulation procedure and affected variables
Total sediment
variables
(ch. VI)
' i.
1 1
S
I
S
D


X



X




|
CD
i
CO
D
a


X



X




unange in discharge or duration*











b
a
a
5
i
D











D
D
D
»











O
5
CD
CO
D
CB
O
TJ
3











surface erosion sediment*











Fines-mass movement8











coarse material-mass movement"











i.
E
I
I
a
i
o
to
c
n
2











Stream
temperature
variables
(ch. VII)
Vegetative shading


X
X



X



c
O
X
E
OJ
s











CD
a
=
D











Year-day-month1











5
a
a
D
to











b
P
IB
Q











J
5











c
3
3











Topographic slope1











Dissolved
oxygen &
organic
matter
(ch. IX)
Nos
cons
eac


X
X


X
X



Nutrients
(ch.X)
leclflc varl
der effects
ih total sub


X
X


X
X



Introduced
chemicals
(ch. XI)
ables
upon
|ect


X
X


X
X



     11.31

-------
Table 11.7—continued








Control opportunities
for
compaction

Reduce vehicle travel
Revegetate treated
areas promptly as
local conditions
dictate
Rip or scarify com-
pacted areas
Road and landing
location
Species selection
Timing of use of
off-road heavy
equipment
Type of site prepa-
ration treatment
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




s
(0
ffi

















u
•s
/pe and location (
i-



















c.
Q.
<0
T3
O)
1
tr

















c

CD
w
I
C0
O




X



X










1
_l



















easonal precipitat
CO



















Ndth of opening1
•s-

















c.
Q_
«
ormalized hydrog
"Z.

















Surface erosion
variables
(ch.IV)




(Rainfall)2
cc



















S (Length-slope)
-i








X
X




X




(Soil credibility)
*
X





X

X
X


X

X
f
Q>
o>
eg
r
M (Vegetation-ma
>
X



X

X


X




X



Ł
round cover dens
O
X



X

X


X




X




oil texture
CO



















X
1
CO






X

X
X




X




ope gradient
CO








X



X

X




urface roughness
CO






X





X

X




istance
o








X





X




00
Q.
(0
1
CO








X





X
Ditch
erosion
(ch. IV)
(app.
IV-C)



^^
(Hydraulic radius
oc








X









^
0
"5
R
o
CO
CO








X










(Friction factor)
"Z.




X



X







Soil maaa
movement
variables
(ch.V)




t
o>
•o
"o
CO



















ope gradient
CO








X








U
to
rainage character
o






X

X





X




o
\
3
D)
E
8
D
CO








X





X




egetative cover
>
X



X



X
X




X



7-
nnual precipitatio
<
















5
00

c
08
~v>
E
b
CO



















5
1
E
^
0
m
Q.















        11.32

-------
Table 11.7— continued










Control opportunities
for
compaction



Reduce vehicle travel
Revegetate treated
areas promptly as
local conditions
dictate
Rip or scarify com-
pacted areas
Road and landing
location
Species selection
Timing of use of
off-road heavy
equipment
Type of site prepa-
ration treatment
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)





Ł

7
TJ
Bankful wi








X











8
o
CO
CD
3
t
CO
I








X







o
co
3
•o
c>
CD
CO
8
•o
Change in





















CD
n>
CO
8
Bankful di






















1
Tl
Suspendei





















•Ł
E
T&
Bed load s


















s.
CD
F
•o
$
§
8
Surface er



















IB
r
®
o
CO
i
i
















s.
§
m
g
a
CO
E
•S

E
CD
CO
i
0















1
E
E
CO

i
s
a
o>
Median sti
















Stream
temperature
variables
(ch. VII)






c*
«
CO
Vegetative




X




X









j.
00
ff
1
o
n
Length-ex





















~
T3
«
Location-It






















Ł
2
CO
I






















^
Tl
Stream wi
























Discharge'
























Bedrock1
























Azimuth1





















&
o
CO
o
Topograpf















Dissolved
oxygen &
organic
matter
(ch. IX)




NOSF



Nutrients
(ch.X)






Introduced
chemicals
(ch. XI)




eciflc variables
consider effects upon
each total subject







X



X





X







X



X





X







X



X





X
            11.33

-------
         Table 11.8—Control opportunities for debris in channel and the variables within the simulation
                                    procedure affected by those controls








Control opportunities
for
debris in channel
Bench cut and
compact fill
Bridges
Brush barrier filter at
toe of slope
Directional felling
Eliminate source of
debris
Endline or fly material
from waterside areas
to upslope landings
Fill slope design and
location
Full bench section
Haul woody material
offsite
Limit equipment
operation
Locate activities produc-
ing small woody
fragments away
from water
Maintain ground cover
Protect road bare surface
area with nonliving
material
Remove debris from
stream
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




Ł































C.
Q.
ID
•o
0)
1
OC

X











X
















*-•
C
E
O)
T3
s
3
>.
I

-------
Table II.8—continued











Control opportunities
for
debris in channel



Bench cut and
compact fill
Bridges
Brush barrier filter at
toe of slope
Directional felling
Eliminate source of
debris
Endline or fly material
from Waterside areas
to upslope landings
Fill slope design and
location
Full bench section
Haul woody material
offsite
Limit equipment
operation
Locate activities produc-
ing small woody
fragments away
from water
Maintain ground cover
Protect road bare surface
area with nonliving
material
Remove debris from
stream
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)






Ł
fc
(ft


6
"5
I


X


X

X




X
X

X

X



X





X






CD
Q.
o
CO

•o CD a a 6 f- CD CO c a T3 a CO c E Tl ? a a 0 c7 c a> h Bed load sed CD T3 8 r 0 Surface eros ?: g E CD *? ? Fines-mass r 1 CD O E nj E 1 i o U) CD ovem E 0> E To CD CO F CD N 'to CO I Stream temperature variables (ch. VII) o> c •o CO Vegetative sF X X r o CO Ł •o CD Length-expo; T Location-latit .c c o 1 T3 I _ TJ 5 CO Ł CO Discharge6 I Azimuth1 CD Q. O CO Topographic Dissolved oxygen & organic matter (ch. IX) Nutrients (ch.X) Introduced chemicals (ch. XI) No specific variables, consider effects upon each total subject X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X n.35


-------
      Table 11.8— continued









Control opportunities
lor
debris in channel
Repair or stabilize
damaged areas
Revegetate treated
areas promptly as
local conditions
dictate
Road and landing
location
Waterside area
Woody debris disposal
sites
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




CO
m














0
o
1
o
0
S
CO
CD
Ł















Rooting depth







X






**
CD
o>
TJ
CD
CO
^
Ł•
1
CD
O





X


X






Latitude1














I
Seasonal precipitati















Width of opening1














\
Normalized hydrogr













Surface erosion
variable*
(ch.IV)




R (Rainfall)2















o
Q.
O
CO
ra
CD
2







X
X






K (Soil credibility)







X
X



CD
E
1
VM (Vegetation-ma





X


X





if
co
1
1
8
•o
c
3
<5





X


X






Ł
1
S
'6
CO















Surface water flux








X






++
0>
1
o>
&
o
CO







X







Surface roughness








X






Distance







X
X






0)
a
5
CO
&
o
CO







X



Ditch
erosion
(ch.IV)
(app.
IV-C)




R (Hydraulic radius

X





X






_
(D
CD
O
0
CD
Q.
0
CO
CO

X





X







N (Friction factor)

X



X

X




Soil mass
movement
variables
(ch.V)




Ł
Q.
0)
T3
'6
CO















.2
TJ
S
O>
CD
a
o
CO







X






CO
i
Drainage character







X







Slope configuration







X







Vegetative cover





X

X
X





7-
Annual Precipitatio












»-
o
i
3
Storm intensity & d















Parent material1















Natural landslides1











n.36

-------
      Table 11.8— continued












Control opportunities
for
debris in channel


Repair or stabilize
damaged areas
Revegetate treated
areas promptly as
local conditions
dictate
Road and landing
location
Waterside area
Woody debris disposal
sites
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch. VI)







c.
Q
®

Bankful widtl

X





X


X








Water surfac

X





X


X


§
?
3
•a
0
0)
O>
CO
o
in
c
0)
a>
1
O


















O)
?
Bankful disc


















o>
U)
Suspended s


















*-•
c

Bed load sed

















E
•o
S
c

Surface eros

















ID
oveme
e
Fines-mass r













Ł.
o>
o>

o
E
E
"5

Coarse mate











HI
0)
§
E

TJ
3
Location-latit


















Ł
c
Year-day-mo



















T-
i
OT




















Discharge'




















Bedrock1




















Azimuth1



















-------
           Table 11.9—Control opportunities for excess water and the variables within the simulation
                                    procedure affected by those controls









Control opportunities
for
excess water
Cutting block design
Identify soil and geology
characteristics and
map sensitive
areas
Machine or hand plant
Maintain ground cover
Out slope fire break lines
or terraces
Prescribe and execute
burn under condi-
tions that will not
result in total clearing
Revegetate treated areas
promptly as local condi-
tions dictate
Species selection
Type of site preparation
treatment
Use maximum spacing
and minimum strip
width in site
preparation
Waterside area
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




I
I
Ł
X


























0
0
o
a
o
o
T3
(0
1
X



























o
TJ
1
O



























o
f
<5
2.
1
§
X





X








X







X




Latitude1



























n
Seasonal precipitati




























Width of opening1


























i-
o.
m
Normalized hydrogr


























Surface erosion
variables
(ch.IV)




R (Rainfall)2
X





















X





•§
O)
I
CO
X















X

X



X
X




K (Soil credibility)




X
X
X









X

X




X

-------
      Table II.9—continued










Control opportunities
for
excess water


Cutting block design
Identify soil and geology
characteristics and
map sensitive
areas
Machine or hand plant
Maintain ground cover
Out slope fire break lines
or terraces
Prescribe and execute
burn under condi-
tions that will not
result in total clearing
Revegetate treated areas
promptly as local condi-
tions dictate
Species selection
Type of site preparation
treatment
Use maximum spacing
and minimum strip
width in site
preparation
Waterside area
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch. VI)





1
V
Bankful width





























S.
o

8

Topographic .
























Dissolved
oxygen &
organic
matter
(ch. IX)



Nutrients
(ch.X)


Introduced
chemicals
(ch. XI)




No specific variables
consider effects upon
each total subject








X








X


X




X






X








X


X




X






X








X


X




X
n.39

-------
           T^ble 11.10—Control opportunities for onsite chemical balance changes and the variables
                         within the simulation procedure affected by those controls








Control opportunities
for
onsite chemical
balance changes
Chemical application
Control ash or dust
build-up
Haul woody material
offsite
Identify soil and
geology character-
istics and map
sensitive areas
Keep pesticides and
rodenticides well
away from surface
runoff
Locate corrals away
from streams (animal
skidding)
Machine or hand plant
Pile material in patterns
Protect fuel storage
areas
Revegetate treated
areas promptly as
local conditions
dictate
Species selection
Type of site prepara-
tion treatment
Woody debris disposal
sites
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




CO
2
CO
CO
8
m































3
O
H-
Type and location c

































*-
Q.
CD
TJ
O>
C
O
&































c
(11

0)
TJ
k_
co
I























X









Latitude1































•j_
o
Seasonal precipitat

































Width of opening1































a
CO
Normalized hydrogr































Surface erosion
variables
(ch. IV)




R (Rainfall)'

































o
CO
O)
c
CD
























X

X






K (Soil erodibility)




X



X







X
X






X

X

X
'c
F
CD
O)
r
VM (Vegetation-ma
X



X










X
X
X





X
X

X

X



**
Ground cover dens
X



X










X
X
X





X
X

X

X




^
1
1








X
























Surface water flux
X























X

X






Slope gradient


























X






Surface roughness















X










X






Distance















X










X






CD
a

-------
Table 11.10—continued
Control opportunities
for
onslte chemical
balance changes
Chemical application
Control ash or dust
build-up
Haul woody material
offsite
Identify soil
and geology character-
istics and map
sensitive areas
Keep pesticides and
rodentlcides well
away from surface
runoff
Locate corrals away
from streams (animal
skidding)
Machine or hand plant
Pile material in patterns
Protect fuel storage
areas
Revegetate treated
areas promptly as
local conditions
dictate
Species selection
Type of site prepara-
tion treatment
Woody debris disposal
sites
Chapter references to the simulation procedure and affected variables
Total sediment
variables
(ch. VI)
Bankful width-depth













Water surface slope













Change in discharge or duration4













Bankful discharge7













Suspended sediment1













Bedload sediment1













Surface erosion sediment3













Fines-mass movement5













S-
E
o
m
E
i
k_
E
01
O













Median size material-mass movement5













Stream
temperature
variables
(ch. VII)
Vegetative shading
X








X
X


Ł
2
8
8
i
_i













Location-latitude1













|
o
•o
>-













Stream width1













Discharge*













Bedrock1













Azimuth1













Topographic slope1













Dissolved
oxygen &
organic
matter
(ch. IX)
Nutrients
(ch.X)
Introduced
chemicals
(ch. XI)
No specific variables
consider effects upon
each total subject
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X
X
X
X
X
X
        11.41

-------
Table 11.11—Control opportunities for slope configuration changes and the variables within the simulation procedure
                                         affected by those controls
Control opportunities
for
slope configuration
changes
Appropriate cross section
for roads
Avoid reading of steep
slopes
Bench cut and compact
fill
Break gradient of fire
lines
Divert water onto stable
areas
Drainage above cut
slope
Full bench section
Identify soil and geology
characteristics and
map sensitive areas
Limit equipment
operation
Machine or hand plant
Maintain ground cover
Prescribe yarding and
skidding layout
Reduce logging road
density
Reduction of impounded
water
Revegetate treated areas
promptly as local
conditions dictate
Road and landing
location
Chapter references to the simulation procedure and affected variables
Hydrology
variables
(ch. Ill)
s
cd
"w
8
CO
















ta
u
B
O
«3
o
o
T3
CO
o
§;
















f
0>
T3
O>
1
cc
X

X


X
X








X
Delivery (user judgment)





X




X


X
X

Latitude1
















Seasonal precipitation1
















Width of opening1
















Normalized hydrograph1
















Surface erosion
variables
(ch. IV)
R (Rainfall)2





X










co
Q.
O
CO
I
.C
•*-•
O)
c
0>
CO
X
X
X
X

X
X




X
X


X
K (Soil erodibility)


X



X
X
X
X
X
X
X


X
VM (Vegetation-management)






X

X
X
X
X
X

X

Ground cover density








X
X
X
X
X

X

Soil texture







X








Surface water flux




X
X





X

X


Slope gradient
X
X
X
X


X




X
X


X
Surface roughness








X

X





Distance
X
X
X
X

X





X
X


X
&
(0
in
CD
a
o
CO
X
X
X








X
X


X
Ditch
erosion
(ch. IV)
(app.
IV-C)
R (Hydraulic radius)
X

X


X
X

X




X

X

•o
'5
CO







X








Slope gradient
X
X
X
X

X
X





X


X
Drainage characteristics
X
X
X
X
X
X
X





X
X

X
Slope configuration
X
X
X
X


X





X


X
Vegetative cover


X



X


X
X
X


X
X
Annual precipitation1
















Storm intensity & duration1
















Parent material1







X








Natural landslides1







X








                                                   11.42

-------
Table 11.11—continued
Control opportunities
for
slope configuration
changes
Appropriate cross section
for roads
Avoid reading of steep
slopes
Bench cut and compact
fill
Break gradient of fire
lines
Divert water onto stable
areas
Drainage above cut
slope
Full bench section
Identify soil and geology
characteristics and
map sensitive areas
Limit equipment
operation
Machine or hand plant
Maintain ground cover
Prescribe yarding and
skidding layout
Reduce logging road
density
Reduction of impounded
water
Revegetate treated areas
promptly as local
conditions dictate
Road and landing
location
Chapter references to the simulation procedure and affected variables
Total sediment
variables
(ch.VI)
Bankful width-depth


X



X

X






X
Water surface slope


X



X

X






X
Change in discharge or duration4
















Bankful discharge7
















Suspended sediment1
















Bedload sediment1
















Surface erosion sediment3
















Fines-mass movement5
















Coarse material-mass movement5
















Median size material-mass movement5
















Stream
temperature
variables
(ch. VII)
Vegetative shading









X




X

Length-exposed reach














X

Location-latitude1
















Year-day-month1
















Stream width1
















Discharge*
















Bedrock1
















Azimuth1
















Topographic slope1
















Dissolved
oxygen &
organic
matter
(ch. IX)
Nutrients
(ch.X)
Introduced
chemicals
(ch. XI)
No specific variables
consider effects upon
each total subject


X



X

X
X
X




X


X



X

X
X
X




X


X



X

X
X
X




X
n.43

-------
                                                    Table II.11—continued






Control opportunities
for
slope configuration
changes
Slope rounding or re-
duction in slope cut
Species selection
Stabilize structures or
cut slopes
Type of site preparation
treatment
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)

S
CO
8
CO
m







u
0
o
«=
CO
8
73
CO
CD
0.








Ł
Q.
CD
T3
O)
C
fc
Ł

X





in
TO
•o
1








Latitude1








Seasonal precipitatio








Width of opening1







Q.
Normalized hydrogra









Surface erosion
variables
(ch. IV)

R (Rainfall)2








CD
Q.
O
To
Ł
O)
CD
_J
2

X
X



X

K (Soil erodibility)


X

X

X
CD
S1
VM (Vegetation-mant


X

X

X

Ground cover density


X

X

X

1
1
S
0
CO








Surface water flux


X



X

Slope gradient

X




X

Surface roughness






X

Distance






X

Q>
I
to
s
o
CO

X




X
Ditch
erosion
(ch. IV)
(app.
IV-C)

tn
3
O
"5
CO
•a
tr








S (Slope of channel)








N (Friction factor)








Soil mass
movement
variables
(ch.V)

Ł
CD
n
'o
CO








Slope gradient

X





w
_o
Drainage characteris

X




X

Slope configuration

X




X

Vegetative cover

X
X

X

X

Annual Precipitation1







I
S
•o
0>
c
E
2
CO








Parent material1








Natural landslides1







'Measured value.
'Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
"See "Soil Mass Movement," chapter V
"Can be taken from chapter III or measured directly.
'Calculated value.
                                                  n.44

-------
Table 11.11— continued













Control opportunities
for
slope configuration
changes




Slope rounding or re-
duction in slope cut
Species selection
Stabilize structures or
cut slopes
Type of site preparation
treatment
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch. VI)









f
o>
7
^
j3
's
"5
«^
_*:
i
m
















8.
o
co

"§
CO
1
5









^—
.2
w
3
•o
o
CD
s>
CO
Ł
'a
.E
CD
CD
CO
O
















"»
0)
CO
Ł
o
CO
T3
1
CO
m















^
CD
E
•o
•Q
CD
a.
CO
CO
















Y.
c
1
CO
0
m












n

CD
E
1
CO
o
o
CD
CD
U
1
V)














Ł
CD

1
CO
CO
E
i
IT








„,
*••
CD
E
>
o
E
CO
CO
2
!s
»
E
i
O







CD
E
o
§
E
ID


i
.2
t_
1
CD
'co
CO
'•%
2








Stream
temperature
variables
(ch. VII)









en
c
1
CO
1
1
1



X











^
.t-
1

0
X
1
1
-1

















1
"i

o
'CO
8
-J

















1:
0
i
jo"
T3
1



















Ł
i
CO
Ł
w



















0)
HI
2"
CO
8
b



















,_
•s
o
•o
m



















,_
Ł
i
'N
<
















CD
o.
o
CO
o
.c
Q.
2
c?
Q.
o








Dissolved
oxygen &
organic
matter
(ch. IX)



Nutrients
(ch. X)


Introduced
chemicals
(ch. XI)








No specific variables
consider effects upon
each total subject










X






X






X
11.45

-------
        Table 11.12—Control opportunities for stream shading and the variables within the simulation
                                     procedure affected by  those controls








Control opportunities
for
streamside shading


Cutting block design
Directional felling
Revegetate treated
areas promptly as
local conditions
dictate
Waterside area
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)




CO
Ł
CO
CO
m
m
X








3
o
0
to
8
•o
CO
t-
X










c.
s.
CD
TO
O)
C
O
o
cc









H
CD
E
o>
3
i
I
CD
0
X




X
X




ID
•a
"co










"c
.y
S
'5.
o
Ł
a
|
CO










?
1
o
•5
=*









a.
CO
1
i
CO
b
z









Surface erosion
variables
(ch. IV)




(Rainfall)2
cc










I
o
CO
1
O)
CD
cn

X





X



s
2
1
'6
CO
*

X




X
CD
E
CD
O>
m
CO
M (Vegetatior
>
X
X



X
X


•>,
co
1
round cover
O
X
X



X
X




oil texture
CO










X
urface water
CO
X





X




CD
1
o>
CD
Q.
o
CO










CO
8
JT
O)
O
CD
1
CO






X




istance
0
X





X




CD
I
CO
o
CO







Ditch
erosion
(ch. IV)
(app.
IV-C)



"in
H5
(Hydraulic n
cc










c
CO
u
"5
CD
Q.
O
CO
CO










fe
(Friction fac
z








Soil mass
movement
variables





Ł
Q.
CD
T3
'5
CO







(ch. V)




CD
1
O)
CD
Q.
0
CO









8
CO
1
CO
u
CD
O>
CO
S
Q










O
5
O
u
o
CO










CD
egetative cov
>
X
X



X
X



o
1
Q.
'o
Ł
CL
"5
c
<








o
^
13
00
'55
1
2
CO











(U
S
CO
E
CO
Q.










I
Tt
"Z
TJ
I
i
Z







1 Measured value.
'Changes only with location.
3See "Surface  Erosion," chapter IV
4See "Hydrology," chapter III
'See "Soil Mass Movement," chapter V
'Can be taken  from chapter III or measured directly.
'Calculated value.
                                                 n.46

-------
    Table 11.12 — continued
*











Control opportunities
for
streamside shading
Cutting block design
Directional felling
Revegetate treated
areas promptly as
local conditions
dictate
Waterside area
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)







.c
Bankful width-dep

X













o
(0
1
i

X







§
+*
3
•o
fe
0>
o>
Change in dischar















Bankful discharge













^
m
Suspended sedim















Bedload sediment











rt
±i
0>
•o
Surface erosion sc













a.
Ł
Fines-mass mover








„
c
b
>
o
Vt
%
Coarse material-rr







I
E
^
E

-------
Table 11.13—Control opportunities for vegetation changes and the variables within the simulation procedure affected
                                             by those controls







Control opportunities
for
vegetation changes

Cutting block design
Directional felling
Leave vegetation
between site prepara-
tion strips
Machine or hand plant
Maintain ground cover
Prescribe limits for
the amount of area
disturbed by
equipment
Species selection
Timing of chemical
applications
Type of site prepara-
tion treatment
Revegetate treated
areas promptly as
local conditions
dictate
Chapter reference* to the simulation procedure and affected variable*


Hydrology
variable*
(ch. Ill)


a
1
1
CD
X




















3
"5
c
o
o
TJ
at
a
a.
>-
X





















Ł
a.
a
TJ
o
o
oc





















c
Q>
O>
T3
fe
in
I

M (Vegetation-mam
>

X


X
X
X



X
X

X

X



X


TK
0)
•o
u
TJ
1
CD
X
X


X
X
X



X
X

X

X



X


2
1
'o
CO






















X
(D
u
3
CO
X



X






X

X

X






lope gradient
CO















X






(A
8
•js
3
CO






X



X




X






istance
o
X



X










X






0)
&
o
CO















X




Ditch
ero*ion
(ch. IV)
(app.
IV-C)


(Hydraulic radius)
DC






















(Slope of channel)
CO






















(Friction factor)
z





















Soil ma**
movement
variable*
(ch.V)


f
o>
T3
'5
CO






















lope gradient
CO










X










8
rainage characterisl
o










X




X






lope configuration
CO










X




X






egetative cover
>
X
X


X
X
X



X
X

X

X



X


1
I
"5
c
<




















o

3
08
C
O
CO






















arent material1
0.






















atural landslides1
z




















'Measured value.
'Changes only with location.
3See "Surface Erosion," chapter IV
4See "Hydrology," chapter III
5See "Soil Mass Movement," chapter V
"Can be taken from chapter III  or measured directly.
'Calculated value.
                                                  11.48

-------
     Table 11.13— continued












Control opportunities
for
vegetation changes

Cutting block design
Directional felling
Leave vegetation
between site prepara-
tion strips
Machine or hand plant
Maintain ground cover
Prescribe limits for
the amount of area
disturbed by
equipment
Species selection
Timing of chemical
applications
Type of site prepara-
tion treatment
Revegetate treated
areas promptly as
local conditions
dictate
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)







1
Tl
Bankful wldth-

X

























S
o
w
Water surface

X




















*
o-
00
3
T»
O
11)
if
'o
_c
1
CO
O



























«
O)
Bankful discha



























§
Suspended se<



























4-*
%
b
1
•a
1
m

























2-
CD
1
r-
Surface erosio


























\
CD
E
CO
1
\L






















i.
c
E
>
E
CO
E
^
Coarse materit




















c
CD
E
>
E
co
E
«
w
«
E
S
'm
a
5





















Stream
temperature
variables
(ch. VII)







O)
Vegetative sha
X
X



X





X















^
•o
Length-expose
X


























%
Location-latituc



























,_
Year-day- mont




























Stream width1




























Discharge*




























Bedrock1




























Azimuth1



























fc
Topographic s




















Dissolved
oxygen &
organic
matter
(ch. IX)



Nutrients
(ch.X)


Introduced
chemicals
(ch. XI)






No specific variables
consider effects upon
each total subject


X



X
X






X

X



X

X



X
X






X

X



X

X



X
X






X

X



X
n.49

-------
Table 11.14—Control opportunities for water concentration and the variables within the simulation procedure affected
                                             by those controls
Control opportunities
for
water concentration
Administrative closure
of roads
Armoring
Avoid roading of steep
slopes
Break gradient of fire-
lines
Close roads after use
Curbs and berms
Cut and fill slope con-
figuration
Cutting block design
Ditch checks
Ditch maintenance
Divert water onto stable
areas
Drainage above cut slope
Hold water onsite
Identify soil and geology
characteristics and
map sensitive areas
Leave vegetation between
strips
Limit equipment
operation
Machine or hand plant
Maintain natural water
courses
Chapter references to the simulation procedure and affected variables
Hydrology
variables
(ch. Ill)
CO
»
CO
$
a
CO







X










3
o
"5
c
o
CO
o
o
•o
c
CD
CD
Q.
Ł







X










Ł
Q.
«
T3
E1
'•5
o
CC


X



X




X






Delivery (user judgment)







X



X
X

X


X
Latitude1


















Seasonal precipitation1


















"b)
1
o
"o
si
*••
T3
5


















Normalized hydrograph1


















Surface erosion
variables
(ch. IV)
R (Rainfall)2














X



CD
a
o
CO
i
j=
«-•
0>
I
co


X
X

X
X
X



X
X

X



K (Soil erodibility)
X



X








X

X
X

VM (Vegetation-management)
X
X


X







X

X
X
X

Ground cover density
X
X


X


X






X
X
X

Soil texture













X




Surface water flux







X


X
X
X

X



Slope gradient


X
X


X











Surface roughness















X


Distance


X
X

X
X
X



X
X

X



0)
Q.
CO
.c
CO
CO
a
o
CO


X



X











Ditch
erosion
(ch. IV)
(app.
IV-C)
R (Hydraulic radius)






X


X

X



X


^
CO
o
"o
CD
Q.
O
CO
CO








X
X

X



X


N (Friction factor)

X






X
X

X






Soil mass
movement
variables
(ch. V)
.c
Q.
CD
•o
'6
CO













X




Slope gradient


X
X

X





X






Drainage characteristics


X
X

X
X



X
X
X





Slope configuration


X
X

X
X











Vegetative cover




X


X






X

X

Annual Precipitation1


















Storm intensity & duration1


















Parent material1













X




Natural landslides1













X




                                                   11.50

-------
Table 11.14—continued
Control opportunities
for
water concentration
Administrative closure
of roads
Armoring
Avoid reading of steep
slopes
Break gradient of fire-
lines
Close roads after use
Curbs and berms
Cut and fill slope con-
figuration
Cutting block design
Ditch checks
Ditch maintenance
Divert water onto stable
areas
Drainage above cut slope
Hold water onsite
Identify soil and geology
characteristics and
map sensitive areas
Leave vegetation between
strips
Limit equipment
operation
Machine or hand plant
Maintain natural water
courses
Chapter reference* to the simulation procedure and affected variables
Total sediment
variables
(ch. VI)
Bankful width-depth















X

X
Water surface slope







X







X

X
Change in discharge or duration4


















Bankful discharge7


















Suspended sediment1


















Bedload sediment1


















Surface erosion sediment3


















Fines-mass movement5


















Coarse material-mass movement6


















Median size material-mass movement6


















Stream
temperature
variables
(ch. VII)
Vegetative shading







X








X

Length-exposed reach







X










Location-latitude1


















|
1
•u
1


















H
I
CO


















Discharge*


















Bedrock1


















Azimuth1


















Topographic slope1


















Dissolved
oxygen ft
organic
matter
(ch. IX)
Nutrients
(ch.X)
Introduced
chemicals
(ch. XI)
No specific variables
consider effects upon
each total subject















X
X
















X
X
















X
X

    11.51

-------
Table 11.14—Control opportunities for water concentration and the variables within the simulation procedure affected
                                             by those controls







Control opportunities
for
water concentration
Minimize convergence of
firelines
Outslope firebreak lines
and terraces
Oversize ditch drain
Pile material in patterns
Prescribed limits
for the amount of
area disturbed
by equipment
Prescribe yarding
and skidding
layout
Reduce road grades
Reduce vehicle
travel
Reduction of
impounded water
Remove debris from
stream
Repair and stabilize
damaged areas
Revegetate treated
areas promptly
as local condi-
tions dictate
Rip or scarify com-
pacted surface
Road and landing
location
Road ditch
Chapter references to the simulation procedure and affected variables


Hydrology
variables
(ch. Ill)


CO
CD
CO
"5
CO
CO
CD
































3
U
O
g
1
c
CO
CD
CL
1-

































.c
Q.
CD
•o
CD
C
1
CL





























X
X

CD
fc
CD
3
|
"35
0

















X







X




X


Latitude1
































c
Seasonal precipitatic

































Width of opening1
































a
Normalized hydrogre

































Surface erosion
variables
(ch. IV)


SL.
To
c
I
cc

































CD
CL
0
CO
i
O)
I
CO









X


X
X















X



K (Soil erodibility)





X



X


X


X





X





X

X

CD
CO
VM (Vegetation-man





X



X


X


X









X

X




^
Ground cover densit





X



X


X


X









X

X





CD
3
'o
CO

































Surface water flux

X

X








X




X









X





'c
CD
01
CD
a
o
CO



X








X
X















X



Surface roughness









X

















X





Distance



X








X
X















X
X


&
CO
co
CD
a
o
CO












X
X















X

Ditch
erosion
(ch. IV)
(app.
IV-C)


R (Hydraulic radius)




X
















X







X
X


CD
CO
O
•5
CD
a
o
CO
CO













X







X







X
X


N (Friction factor)





















X







X
X

Soil mass
movement
variables
(ch. V)


Ł
Q.
CD
5
CO

































C
.CD
CO
CD
&
O
CO



X





X



















X


*-•
Drainage characteris

X

X





X







X









X

X



Slope configuration



X





X



















X



Vegetative cover









X


X


X









X



X



Annual precipitation1































o
CO
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                                                  n.52

-------
Table 11.14—Control opportunities for water concentration and the variables within the simulation
                      procedure affected  by those controls — continued













Control opportunities
for
water concentration





Minimize convergence of
firelines
Outslope firebreak lines
and terraces
Oversize ditch drain
Pile material in patterns
Prescribed limits
for the amount of
area disturbed
by equipment
Prescribe yarding
and skidding
layout
Reduce road grades
Reduce vehicle
travel
Reduction of
impounded water
Remove debris from
stream
Repair and stabilize
damaged areas
Revegetate treated
areas promptly
as local condi-
tions dictate
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pacted surfaces
Road and landing
location
Road ditch
Chapter references to the simulation procedure and affected variables


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variables
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                                          11.53

-------
                                               Table II.14— continued






Control opportunities
for
water concentration

Sediment traps
Slope length
Space culverts to
control velocity
Species selection
Timing of use of
off-road heavy
equipment
Trash racks
Type of site
preparation
treatment
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and minimum
strip width in
site preparation
Waterside area
Chapter references to the simulation procedure and affected variables


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variables
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'Calculated value.
                                                   11.54

-------
Table 11.14 — continued













Control opportunities
for
water concentration



Sediment traps
Slope length
Space culverts to
control velocity
Species selection
Timing of use of
off-road heavy
equipment
Trash racks
Type of site
preparation
treatment
Use maximum spacing
and minimum
strip width in
site preparation
Waterside area
Chapter references to the simulation procedure and affected variables


Total sediment
variables
(ch.VI)








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     n.55

-------
SECTION D: CONTROL  OPPORTUNITY
               DESCRIPTIONS


  All controls are listed in alphabetical order with
a brief description of each control. Some reference
sources are listed, but, in general, the following can
be contacted for further information regarding the
controls.

  Engineering Controls
    Engineering, Forest Service
    Soil Conservation Service
    Soil Conservation Districts
    State and county highway departments
  Silvicultural Controls
    State and Private Forestry Offices, Forest Ser-
    vice
    Timber Management, Forest Service
    Watershed Management, Forest Service
    Soil Conservation Service
    Soil Conservation Districts
  This section  can be  used in any phase  in the
process of choosing mixtures of controls.

        Administrative Closure of Roads
  Procedural/Preventive/Mitigative — Bare Soil,
       Compaction, Water Concentration
  Closing roads to  all traffic during wet periods of
the year prevents rutting  and related concentrated
flow  in ruts. It also reduces compaction and sedi-
ment production on road surfaces.

      Appropriate Cross-Section for Roads
Preventive  —  Bare  Soil,  Slope  Configuration
                   Changes
  Consider  the erosion  potentials from  various
cross-sections of the road. Choose cross-sections
that offer the least impact on the resource.
  Design combinations can be chosen from existing
typical cross-sections. See State or local highway
departments for information. The least erodible
section  will  vary  with condition of soils, cross
slopes, precipitation, and road locations. Some ex-
amples are:

  1.  Crown with ditch and culverts
  2.  Crown with ditch and water bars
  3.  Dips
  4.  Inslope with culverts
  5.  Inslope with water bars
  6.  Outslope
  7.  Turnpike
                   Armoring
       Preventive/Mitigative — Bare Soil,
Channel Gradient Changes, Water Concentration
  Armoring protects ditches, channels, and low
water crossings or outfalls. In addition, it stabilizes
the channel, prevents damage from eddies, reduces
erodible material, and reduces maintenance.
  Some examples of armoring are: armor ditches,
armor  cut banks for concentrated flow, armor fill
slopes  below vertical curve sags, armor culvert in-
lets, armor tops of cut ditches,  armor at  cross
drainage pipes and ground or channel culvert dis-
charges.


         Avoid Reading of Steep  Slopes
  Preventive — Bare Soil, Slope Configuration
         Changes, Water Concentration
  If alternatives are available, locate roads on flat-
ter slopes.  Vary both the grade and alignment to
minimize mileage on steeper slopes. Roads should
be  built to grade on slopes. Such road planning
reduces bare soil per mile of road,  reduces slope of
cut-and-fill slopes, and reduces length of cut-and-
fill slopes.
  However, it should be noted that increasing road
mileage can also increase total sediment produc-
tion.
          Bench Cut and Compact Fill
   Preventive/Mitigative — Debris in Channel,
          Slope Configuration  Changes
  Cut benches into natural slope and compact fills
to reduce mass failure. This method is usually used
on cross slopes greater than 30 percent in unstable
material.  Compaction  increases  shear  strength
within fills, reduces length and amount of fill slope
material,  and reduces the probability of slumps
within the fill. Benches reduce chances for mass
failure.
           Break Gradient of Firelines
Preventive/Mitigative —  Slope  Configuration
                    Changes
  Change gradient of  fireline at intervals by an-
gling slightly up or downslope. This will reduce the
length of the  distributed slope and reduce  both
water  velocity  and  concentration.  Outsloping
should also be continued with gradient breaking to
prevent water concentration, especially in sensitive
areas.
                                              11.56

-------
                    Bridges
   Preventive — Channel Gradient Changes,
              Debris in Channel
  Use  bridges  or large  oval  or arch  over  live
streams. Streamflow will be restricted less than the
flow  through culverts. In addition, channel scour
will  be reduced  because outlet velocities  from
culverts are eliminated.
  Standard bridge  design methods are available
through State highway offices.


     Brush Barrier Filter at the Toe of Fill
       Preventive/Mitigative — Bare Soil,
               Debris in Channel
  Build a debris barrier of slash at the toe of the fill
to trap sediment  from roads or landings. Barriers
may be covered with filter cloth. Brush barriers are
often considered  a temporary measure effective
only until vegetative cover is established.

             Chemical Application
     Preventive —  Aerial Drift of Chemicals
   Select chemicals on the basis of particle size and
volatility. Heavier  and larger particles drift less.
Choose the most accurate application method for
the job within economic reason (e.g.,  helicopter,
fixed wing aircraft,  or low elevation spraying). Ac-
curate placement of the chemical cuts down on
aerial  drift of chemicals. Choose the proper size
nozzle, correct formulations,  and carriers for site
specific  conditions. Use properly  trained  and
licensed  application  personnel to  reduce the
likelihood  of accidental spills and  increase the
probability  that chemicals will be mixed and ap-
plied properly. Use only EPA-approved chemicals
and  follow the label instructions.
   See  also  "Conformance to  Regulations"  and
"Timing of Chemical Application."

             Close Roads After Uses
       Procedural/Mitigative — Bare Soil,
        Compaction, Water Concentration
  Close temporary timber access roads to all traffic
when not used for timber needs. This allows the
road's  surface to  stabilize and vegetative cover to
become  established.  Rutting  is substantially
reduced.
  Drainage facilities  need  to be  oversize or
removed to prevent destruction during periods of
nonuse  and reduced  maintenance.   Drainage
maintenance must be kept current. The road sur-
face  may be scarified and seeded upon closure.
          Conformance to Regulations
      Procedural — All Resource Impacts
  Follow  EPA  regulations  regarding  chemical
handling and application. Regulations are designed
to reduce application error.
  Refer to various EPA handbooks for the most up-
to-date regulations.

          Control Ash or Dust Buildup
Preventive/Mitigative — Aerial Drift of Chemicals,
       Onsite Chemical Balance Changes
  Avoid  ash or dust concentration in  areas where
wind or chemical seep could deposit materials into
waterways.
  Slash burning can be done on a dispersed rather
than on a concentrated basis. In addition, cuts and
fills from roadbuilding or landing construction can
be located away from streams and/or  stabilized
quickly.

               Curbs  and Berms
  Preventive/Mitigative — Water Concentration
  Construct asphalt or concrete curbs or earthen
berms on roadway above tops of fill slopes to pre-
vent water on road surface from running over fill
slope.
  See  local Forest  Service or  State or  county
highway  departments for standard drawings. Some
examples are:  asphalt or concrete curbs on paved
roadway  and earth  dikes on roadway.

        Cut-and-Fill Slope Configuration
  Mitigative — Bare Soil, Water Concentration
  Leave  bank  surfaces rough or bench them. Such
treatment  may  reduce flow  velocity  and  aid  in
revegetation.
  Information can be obtained from the Forest Ser-
vice, Soil Conservation Service, or State highway
departments. Some examples  are: rough  cut banks
and bench fill or cut banks.

             Cutting Block Design
          Preventive — Excess Water,
          Streamside Shading Change,
    Vegetation Change, Water Concentration
  Limit  the size of cutting blocks and disperse
them  to  prevent excess water  in subsoil  and  to
maintain root  strength. This will allow soils under
fully  vegetated units  to  be  dried  through
evapotranspiration during  growing seasons and the
distances from top to bottom of cutting blocks to be
reduced.
                                              11.57

-------
  This application is most effective on areas with
fine-textured subsoils (clays) and erodible surface
soils (like those derived from decomposed granite);
on steep slopes; on clearcut and seed tree cut areas;
and  on areas  with  heavy precipitation falling as
rain. Specific treatment methods include:

  1.  Orient  cutting blocks with  adequate buffer
     strips.
  2.  Orient cutting blocks at right angles to slopes.
  3.  Disperse cutting blocks.
  4.  Design more but smaller cutting blocks.

               Directional Felling
      Preventive — Bare Soil, Compaction,
 Debris in Channel, Streamside Shading Changes,
    Vegetation Changes, Water Concentration
   Use directional felling as a way of concentrating
 felled  trees to increase logging efficiency and to
 lessen site disturbance. Use direct felling to  pre-
 vent trees from falling into the water, especially in
 waterside areas. Also, fell trees  that are close to
 roads or streambanks and that would naturally up-
 root before the next silvicultural  activity; this will
 reduce potential bank erosion.

                 Ditch Checks
    Mitigative — Channel Gradient Changes,
              Water Concentration
   Construct a series of armored check dams in the
 road side ditch. This reduces velocity in ditch by
 reducing effective grade, mitigates cut bank under-
 cutting, and controls grade.

               Ditch Maintenance
 Procedural/Mitigative  — Channel  Gradient
                   Changes,
              Water Concentration
   Clean ditch  to original cross-sections and leave
 grass lining and vegetative cover. This prevents un-
 dercutting and degradation of  ditch edges  and
 reduces sediment leaving ditch.

        Divert Water Onto Stable Areas
   Preventive — Slope Configuration Changes,
              Water Concentration
  Avoid diversion of water onto erosive or mass
failure-sensitive areas. Water on such areas can in-
crease  erosion. Damage can be avoided by locating
sensitive areas before an activity is started. Consult
soil,  hydrologic, and geologic maps to locate sen-
sitive areas.
           Drainage Above Cut Slope
       Preventive/Mitigative — Bare Soil,
Slope  Configuration Changes, Water Concentra-
                      tion
  Place  drainage  above  cut slope  parallel to
roadway to intercept overland and some shallow,
subsurface flow before it can run over and down the
cut slope.
  Use  engineering design obtainable from Forest
Service or State or local  highway  departments.
Design examples are: use of a perforated pipe at top
of cut bank and ditch  above cut.

           Eliminate Source of Debris
        Mitigative —  Debris in Channel
  Seek out and eliminate sources of organic debris
pollutant to prevent their continued entry  into
water.  Specific treatments  are:  burning woody
debris, burying woody debris, constructing barriers
to keep debris out of channels, hauling debris off-
site, rearranging debris, and revegetating.

  Endline or Fly Material from Waterside Areas
              to Upslope Landings
       Preventive/Mitigative — Bare Soil,
         Compaction, Debris in Channel
  Remove  organic material,  resulting from
silvicultural  activity,  from  waterside areas.
Facilitate harvest of merchantable  material  and
removal of unused material and slash, within en-
vironmental constraints of the area.  Equipment
used must be capable of pulling or lifting logs from
beds to landings. Lifting the leading  end  of the log
or the  entire log is desirable. Material that might
enter water must be removed.
  This method applies in  areas where tractor or
other ground-lead methods would cause  compac-
tion or channelization of riparian soils, or cause
pollution  of water.  Soil conditions may  influence
the need for this control, which is more critical as
slopes  steepen.

Enforcement  of Standards and  Bonding of
                   Operators
       Procedural — All Resource Impacts
  Consider contracts  with specifications  for
bonding all contractors and permittees using  per-
formance criteria. Insure that planned erosion  con-
trol measures and all other planned controls are ac-
tually  carried out on the ground.
  Enforcement controls, combined with monitor-
ing, can  insure protection of water  quality ac-
cording to project plans.  Sample  contracts are
                                               11.58

-------
available  from State foresters or Forest Service
State and Private Forestry offices.


         Fill Slope Design and Location
 Procedural/Preventive, Mitigative — Bare Soil,
               Debris in  Channel
  When constructing roads, do not allow debris to
reach  stream.  Prevent fill slope material from
reaching stream  by following design, controlling
blasting, and controlling length of fill slope during
construction. Reduce fill  slope length to prevent
stream encroachment by toes  of fill  slopes.
  Designs can  be obtained from  highway depart-
ments. Specific treatments include:  gabion place-
ment at the fill slope edge and retaining structures
at the toe of fill slope.


               Full Bench Section
        Preventive — Debris  in  Channel
          Slope Configuration Changes

  Build  roadbed  entirely on natural  ground in
steep  areas.  Side casts  and  fill  slopes  are
eliminated.
  Dispose of excess material  in stable areas.  See
Forest Service or local  highway department for
design specifications.
          Haul Woody Material Offsite
        Mitigative — Debris in Channel,
       Onsite Chemical Balance Changes
   Haul chips and other small woody material that
 result from silvicultural activity  and that could
 add chemicals or result in debris in the stream, to
 offsite disposal areas.
               Hold Water Onsite
       Preventive/Mitigative — Bare Soil,
              Water Concentration
  Retaining water in place through restriction of
water movement is one key to minimizing pollu-
tion. Use control measures that will disperse water
and not allow water to concentrate to prevent sedi-
ment movement  and establishment of bare  soil.
Keep unnecessary site disturbance at a minimum
for all silvicultural activities and use site stabiliza-
tion  techniques before,  during,  and  after com-
pleting these activities. Check local  sources for ac-
ceptable measures to prevent or remedy  the  un-
necessary movement of water.
    Identify Soil and Geologic Characteristics
            and Map Sensitive Areas
Procedural/Preventive — Bare Soil, Compaction,
    Excess Water, Onsite Chemical Changes,
Slope Configuration  Changes,  Water  Concentra-
                      tion
  Using  soil analysis techniques, determine the
soil/moisture relationship of sites where degrada-
tion is likely to occur with normal use. Define the
limiting  percentage  of compaction that will  be
tolerated on a given percentage of the site area.
Also, define what percent of the area may be com-
pacted. Before beginning the operation, study sur-
veys of the area  to  locate sensitive areas. Avoid
these sensitive  areas during the  operation. Such
determinations aid  in identifying  the types of
systems  that  could  be  used  to carry out  the
silvicultural prescription, aid  in  selecting  proper
equipment,  and also may reduce  the number and
cost of mitigative measures.
  Useful information may be obtained from com-
partment examinations,  soil surveys,  hydrologic
surveys, and geologic surveys. This technique is es-
pecially effective in areas prone to mass movement.

     Keep Pesticides and Rodenticides Well
           Away From Surface Runoff
     Preventive — Aerial  Drift of Chemicals,
       Onsite Chemical Balance  Changes
  Exposing chemicals to surface runoff areas can
seriously influence both plant and  animal com-
munities. Identify potential surface runoff areas
and restrict chemical  use  near  these  areas.
Pesticides are commonly  applied in aerial opera-
tions and chemical  drifting is a  major problem.
Regulations concerning chemical  use, application
procedures,  and  critical  on-the-ground problem
areas must  be  understood by licensed personnel
before chemical application.
  Refer to controls  on "Chemical Application,"
"Conformance to Regulations," and "Timing of
Chemical Application."
        Leave Vegetation Between Strips
      Preventive — Bare Soil, Compaction,
    Vegetation Changes, Water Concentration
  When using  stripping  techniques  for site
preparation, leave some unstripped ground at in-
tervals; this forms small filter strips around and
within the stripped areas.
  Refer to Forest Service Region 4 handbooks for
more information on stripping techniques.
                                               H.59

-------
             Limit Disturbed Area
      Procedural — All Resource Impacts

  Limit areas where work activity takes place at
any given time. Require that one operational area
be  stabilized  before beginning  work on another
area. An operational area can be defined in terms of
the maximum number of active cut blocks, max-
imum  number of acres without seeding, or max-
imum miles of road without installation of perma-
nent erosion controls. Active  areas should be only
large enough to allow most equipment to work con-
currently.

  This control is especially useful on large projects.

          Limit Equipment Operation
      Preventive—Bare Soil, Compaction,
Debris in  Channel,  Slope Configuration Changes,
              Water Concentration
  Limit or eliminate operation of heavy equipment
on  unstable or highly erodible soils. In addition,
equipment operation in  streams should  be
minimized. Limit  equipment operation by  cable
methods of logging and by winching (endlining)
logs in unstable areas.
  This  application  is  most  effective  on  steep
grounds where soil  masses are unstable and/or
where soils are erodible.

       Locate Activities Producing Small,
      Woody Fragments Away From Water
        Preventive  — Debris in Channel
  Keep chipping and mastication operations well
away from streams  and water courses.

      Locate Corrals Away From Streams
              (Animal Skidding)
        Preventive — Debris in Channel,
       Onsite Chemical Balance Changes
  When using animals in logging operations,  place
corrals well away  from stream courses. Animal
waste should be kept out of the water. Water may
have to be hauled for the animals.

            Machine or Hand Plant
   Preventive—Bare Soil, Compaction, Excess
   Water, Onsite Chemical Balance Changes,
Slope Configuration Changes, Vegetation Changes,
             Water Concentration

  The method of tree planting, either by machine
or hand, often governs the intensity of site prepara-
tion treatments. Machine planting usually requires
that the site be cleared of logs,  limbs, and  other
larger debris.  Debris is not a  problem for hand
planting as long as crews can walk through it and
trees can be planted at the prescribed spacing. If
debris is too heavy for hand planting, the situation
is often rectified by a light burn which consumes
the small material and often does not expose exces-
sive amounts of soil. In some areas, fire will expose
unacceptable amounts of bare soil and mechanical
removal of debris is the  only alternative.  Also,
mechanical debris removal is needed to reduce fire
hazard and for other resource purposes. In many
situations machine planting  and  associated site
preparation can be fully acceptable.

            Maintain Ground  Cover
 Preventive — Debris in Channel,  Excess Water,
          Slope Configuration Changes,
              Vegetation Changes
  Maintain  as much vegetation,  which may in-
clude trees, understory, and litter,  as is consistent
with  management objectives;  or  establish tree
regeneration and desirable species of understory
vegetation. Evapotranspiration reduces amounts of
water  in  the  soil.  Mechanical  protection
strengthens slopes against mass failure.
  Vegetation,  through  physiological use of soil
moisture,  will  dry soil masses and  prevent satura-
tion of subsoils. Ground covered by vegetation will
be protected from  the impact of raindrops during
heavy  precipitation,  thus  preventing detachment
and downhill transport of soil particles. Vegetation
will produce a protective layer of duff.  Infiltration
will be enhanced and ground surface water flow will
be reduced or eliminated. Tree roots and roots of
other species reinforce the soil  mass.

        Maintain Natural Water Courses
    Preventive — Channel Gradient Changes,
              Water Concentration
  Keep stream channels free of debris which might
deflect or constrict water flow and which could ac-
celerate bank  or channel erosion. Keeping stream-
banks  and channels  stable in this manner will
reduce  sediment loads. Road  crossings,  bridges,
culverts, fords, and  other  stream  encroachments
should be aligned and constructed to  reduce im-
pacts on flow  characteristics.
  Remove all introduced organic material from the
stream course  as soon as it is introduced to prevent
damming and streambank alteration. Refer to con-
trols  on  "Directional  Felling" and  "Waterside
Areas." Both are important in maintaining natural
water courses.
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       Minimize Convergence of Firelines
       Preventive — Water Concentration
  When locating and constructing firelines, avoid
downhill convergence. If firelines do not converge,
water  will  be  prevented from  concentrating
severely.

                  Monitoring
       Procedural — All Resource Impacts
  Monitor silvicultural and related activities with
periodic inspections. Schedule inspections to allow
for maintenance prior to periods of heavy  runoff.
Pay particular  attention  to  drainage facilities.
Monitoring by itself is not a control; however, it is a
way to make  sure other controls  are carried out
properly.  See  "Enforcement  of  Standards and
Bonding of Operators."

     Outslope Firebreak Lines and Terraces
Preventive — Excess Water, Water Concentration
  When  constructing firebreak  lines or terraces,
make certain they are  outsloped  so water is not
concentrated by insloping.  Gully  erosion can  be
controlled by outsloping.
  Information regarding laying of grade and other
design criteria can be obtained from local highway
departments or Forest Service Engineering person-
nel.

             Oversize Ditch Drain
    Preventive — Channel Gradient Changes,
              Water Concentration
  Install culverts that are larger than necessary for
anticipated runoff, thus allowing some debris plug-
ging before water will flow over  road.
  See Forest Service or  State and county highway
departments for culvert size requirements. This is
particularly effective when roads  are closed to users
and when maintenance inspections are infrequent.

           Pile Material  in Patterns
Preventive — Onsite  Chemical Balance Changes,
             Water Concentration
  Pile debris from cutting, site preparation, or fuel
management in patterns which prevent concentra-
tion of water.  Gullying  can be prevented  by
avoiding  water  concentration  around  piles  of
material.  Avoid  diverting  water  onto  sensitive
areas.

 Prescribe and Execute Burns Under Conditions
     That Will Not Result in Total Cleanup
     Preventive — Bare Soil, Excess Water
  Fuel treatment burns should be cool enough to
 leave unburned and partially burned material on
 the site. This offers some ground cover protection
 for the soil. Alter firing patterns to reduce overall
 burn intensity so less soil is bared. Some fuel treat-
 ment goals may have to be revised as a result of this
 control. Consider special burning techniques such
 as the jackpot or spot burn.
  The  Forest Service  and  its State  and Private
 Forestry offices will have fuel treatment guidelines
 that describe fire manipulation in detail.

      Prescribe Limits for Amount of Area
            Disturbed by Equipment
      Preventive —  Bare  Soil, Compaction,
    Vegetation Changes, Water Concentration
  Minimize  bare soil  area necessary to satisfy
 silvicultural  objective. Increase the amount of
 acres served by roads or landings by planning truck
 roads,  skid roads, and landings at  the same time
 and by maintaining wider spacing between truck
 roads and skid roads.

     Prescribe Yarding and Skidding Layout
   Preventive — Slope Configuration Changes,
              Water Concentration
  Design yarding and skidding patterns to radiate
 downhill. Skid roads oriented this way will spread,
 rather than collect, water. Thus, water will not be
 concentrated and its energy for eroding material
 into bodies of water will be reduced. The water will
 also have an increased opportunity to infiltrate.
  Water concentration caused by skid roads and
 trails becomes more severe with increased slope
 and precipitation and  decreased soil  particle size.
 Water concentration must  also be considered on
 shallow slopes particularly in the Southern United
 States.

  Prevent Fire Spread  Outside Treatment Areas
             Preventive — Bare Soil
  Take steps before the fuel treatment operation to
 prevent  fire  spread outside treatment areas by
 using firebreaks and having equipment available.
 If fires are contained, less bare soil is  exposed and
 aerial drift of ash and  dust  can be  reduced.

           Protect Fuel Storage Areas
 Preventive — Onsite Chemical Balance Changes
  Place fuel  storage areas in locations well away
from streams or water courses and take precautions
to impound or divert a possible fuel spill.
  Dimensional ditches  and impoundments with
straw bales to soak up excess fuel can be effective.
                                              11.61

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        Protect Road Bare-Surface Areas
            With Nonliving Material
   Mitigative — Bare Soil, Debris in Channel
  Armor bare soil related to roads,  especially  in
specific locations  that  are  not  able  to  be
revegetated.
  Use appropriate structural thickness designs and
pavement design methods. See local Forest Service
or county  highway  department  for  appropriate
design criteria. Examples are:
  1.  Gravel road surface: high cost although lower
     than asphalt paving.
  2.  Asphalt road surface:  high  cost  relative  to
     other  treatments.
  3.  Spot gravel on critical areas of road surface:
     used on "soft" areas of road.
  4.  Dust oil applied to road surface: prevents ag-
     gregate breakdown, must be used frequently
     to be  effective.
  5.  Shot crete surface of cut-and-fill slopes: used
     only when all else  fails; cost is high.
  6.  Jute mats or excelsior pads on cut-and-fill
     slopes: rarely  used singly,  usually used  in
     combination with revegetation.
  Prescribe limits for the amount of area disturbed
by equipment by constructing narrow truck roads
and avoiding unnecessary movement of vehicles off
established road and landing areas.
  Do not make unnecessary roads. Roads should be
designed using such  techniques as "rolling dips."

              Reduce Road Grades
       Preventive — Water Concentration
  Reducing road grades tends to reduce ditch ero-
sion  and road surface erosion by reducing  water
velocity. However, there is the possibility of in-
creasing road mileage,  in  order to use  flatter
grades, to the point  where total sediment  yield is
increased. Refer to road design standards  of local
highway departments.

              Reduce Log Length
            Preventive — Bare Soil
  Reduce log length  prior to yarding, skidding,  or
hauling to  require less turning space in the woods
and to allow use of lower standard roads. (The use
of smaller  vehicles can  mean less turning  space
which,  in turn, reduces the amount of disturbed
area.)

  However, logging efficiency must be considered.
The additional cost of bucking tree-length logs into
one or  more logs in the  woods must be compared
with the  potential disturbance and  exposure of
bare soil if the logs are not bucked.

         Reduce Logging Road Density
     Preventive — Bare Soil,  Compaction,
          Slope Configuration  Changes
  Hold  logging road density  in areas sensitive to
mass failure to a minimum. If  critical areas must
be crossed, use bridge, complete fill techniques, or
center balance slope methods.
  Note that reduction of roads could require a more
expensive logging systsem.

           Reduce Vehicular Travel
Preventive — Compaction, Water Concentration
  Since ruts and compacted tracks can cause water
concentration,  a simple  reduction  of vehicular
travel to only that which is  absolutely necessary
would help alleviate water concentration impacts.

        Reduction of Impounded Water
   Mitigative — Channel Gradient Changes,
Slope Configuration Changes,  Water  Concentra-
                      tion
  Divert water from impoundment to prevent ex-
cess water from accumulating and increasing the
surface  erosion and mass failure risk. Drain  im-
pounded water away  and spread  water over more
absorbent surfaces. Increase the absorption rate of
the impoundment, if possible, by ripping,  scarify-
ing,  roughening the surface,  or  establishing
vegetative cover. In addition, during  or after the
operation, prevent debris dam or barrier formation
that could lead to water concentration. Locate and
remove  small dams before problems become large
and costs go up.
  Specific examples include:
  1. Install a  ditch drain culvert that discharges
    onto undisturbed natural ground above and as
    near  to streams as possible.
  2. Drain project  prior  to  seasonal shutdown.
    Ditch, crown,  water bar,  and remove tem-
    porary fills and culverts.
  3. Keep project  drained during construction;
    construct ditches, temporary culverts, etc.

          Remove Debris From Stream
Mitigative — Debris in Channel, Water Concentra-
                      tion
   Remove organic and inorganic debris which has
entered the stream from silvicultural and related
activities. This reduces pollution from debris and
prevents undercutting of slopes.
                                              11.62

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  Debris  removal should  utilize least damaging
methods.  Specific treatments include:
  1. Hazard debris removal
  2. Lining out debris
  3. Lifting out with loader
  4. Lifting out with helicopter
  5. Scattered,  free floating debris  (chips,  slack,
     fragments)  can be  gathered  by towed or
     stationary  booms  or  partially  submerged
     screens.

      Repair and Stabilize Damaged Areas
    Mitigative — Channel Gradient Changes,
     Debris in Channel, Water Concentration

  Shape and stabilize areas damaged during the
operation with organic or inorganic material using
outsloping techniques to prevent water concentra-
tion. Restore streambanks and stream bottoms to
as near original  configuration as possible. Prevent
continued deterioration  of the aquatic environ-
ment. Use combinations of soil replacement, place-
ment of gabions, and riprap.
  A field  decision will have to be made regarding
whether or not the repair effort would cause more
damage than that existing before repairs were un-
dertaken.  Forest Service,  Soil Conservation Ser-
vice, or county agents can offer design advice.


       Revegetate Treated Areas Promptly
          As Local Conditions Dictate
     Mitigative — Aerial Drift of Chemicals,
   Bare Soil, Compaction, Debris in Channel,
Excess Water, Onsite Chemical Balance Changes,
Slope Configuration Changes, Streamside Shading
         Changes, Water Concentration

  Revegetate  using  artificial  techniques to es-
tablish  a  plant  cover on bare soil surfaces —
usually skid trails, ditches,  and other disturbed
areas. Stabilize the soil surface. Revegetation can
also increase shading on water. Apply grass, shrub,
tree seed,  or sod and/or seedlings to exposed areas;
add fertilizer, lime, mulch, or jute mats  as local
conditions dictate. This  will reduce soil  eroding
energy from water related sources.
  See Soil Conservation Service, Forest Service, or
extension  agent for local grass species and require-
ments for  fertilizer, lime, mulch, etc. Grass  cover
can be very difficult  to establish on arid or sterile
soils or on  fill slopes over 1:1. Jute mats or excelsior
pads are often required to hold seed to establish
grass in critical areas.
       Rip or Scarify Compacted Surfaces
 Mitigative — Compaction, Water Concentration
  Ripping or scarifying may restore the site's
natural water-holding capacity, restore water in-
filtration capability, increase  root  permeability,
and increase the site's potential to reestablish a
vegetative cover. On trails compacted by off-road,
heavy equipment,  the compacted  layer can  be
remedied by single ripping when layer width is less
than two times the  depth of  compaction.  On
landings and concentrated use areas where com-
paction has occurred, the site should be ripped to
the depth of compacting. On skid trails, roads, and
landings with surface compaction of 8 inches or
less, scarification can mitigate some damage.
  Need for treatment is determined by examina-
tion and testing proctor curves.

          Road and Landing Location
 Preventive — Compaction, Debris in Channel,
Slope Configuration Changes,  Water  Concentra-
                      tion
  Avoid  unstable areas and critical  slope con-
figuration. Prevent  water  from accumulating,
channeling,  eroding, and  degrading  water and
site quality. Keep logging roads and skid trails out
of stream bottomlands. Avoid sustained grades; at-
tempt to vary the grade. Whenever possible, locate
water concentrating activities on  high ground.
  Require that hydrologic and soils information be
put into an area logging plan. Develop  a transpor-
tation plan that serves all of the resources with the
least total impact by reducing duplication of roads.
Specific considerations are:
  1.  Avoid known slump/slide areas.
  2.  Avoid areas with high risk of mass failure.
  3.  Avoid concave slopes in close  proximity to
     streams.
  4.  Place roads on convex slopes above streams.

                  Road Ditch
 Preventive/Mitigative —  Water Concentration
  Drain inside road ditch with pipe or water bar.
  This is  a positive method of controlling surface
routing across a road. A plugged ditch may  cause
mass failure and accelerated road surface erosion.
Therefore, maintenance is necessary.

                Road Drainage
   Preventive — Compaction,  Excess Water,
Slope Configuration Changes,  Water  Concentra-
                     tion
  Divert road runoff at frequent intervals to reduce
                                              11.63

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volume and velocity, thereby  reducing erosion
potential and providing the opportunity for water
to infiltrate soil before reaching  stream.  Road
drainage and spreading techniques include dipping
of sustained grades,  outsloping and/or insloping
and cross draining of water onto areas most capable
of spreading and infiltrating the runoff. This con-
trol  could pertain  to tractor trails, roads, and
landings.   Additional treatments are  lead off
ditches and water bars. For design specifications,
consult Forest Service regional road manuals and
related publications.


   Road Drainage Maintenance During Storms
       Preventive — All Resource Impacts
  Patrol roads when heavy precipitation is forecast
and  during precipitation. Keep drainage system
functioning during runoff (unplug culverts, remove
slides from ditches, etc.). Storm patrol organiza-
tion and procedures must be established before the
storm  occurs.  Labor and  equipment  must be
available for emergency work. Storm forecasting is
required.
  Storm patrol is particularly useful in areas of fre-
quent, very heavy rainfall with steep slopes and un-
stable material.


                 Sediment Trap
       Mitigative —  Water Concentration
  Excavate or   dam a sediment  pond below
culverts. This sediment trap provides a  pond of
water below the  culvert, thus allowing sediment to
settle out.
  See  Forest Service or State or  local  highway
department for design characteristics. Application
is very  site specific. This is a short-term control
which is  usually effective  only  until vegetative
cover has become established. Pond will eventually
silt full.


         Select  Low Impact Equipment
       Preventive — All Resource Impacts
  Determine what type of equipment can minimize
compaction and accomplish the required  work.
Make determinations of the equipment's pulling
capacity,  pounds/square inch of float, speed, and
stability.
  May  require  equipment  other than  what  is
presently used in the area or a change to a different
system that meets the resource objective (i.e., trac-
tor to cable).
                 Slope Length
  Preventive — Bare Soil, Water Concentration
  Avoid  silvicultural  treatments  using  long
downslope  distances to  prevent high  overland
water velocities and decrease erosion.
  The  Forest Service  has  standard placement
tables for critical distances.

  Space Culverts to Control Road Ditch  Erosion
    Preventive — Channel Gradient Changes,
             Water Concentration
  Space ditch drain  culverts to control quantity
and velocity of water flowing in roadside ditches.
Proper  drainage  regulates  water  quantity and
velocity, soil detachment, and transport.
  See Forest Service or state highway departments
for standards. Additional ditch drain culverts may
help to  control active ditch erosion.

               Species Selection
Preventive  —  Bare Soil,   Compaction,  Excess
                    Water,
       Onsite Chemical Balance Changes,
Slope Configuration Changes, Vegetation  Changes,
             Water Concentration
  The tree species to be planted often govern the
type and the intensity of site preparation treat-
ments.  Tree seedlings have  varying tolerance to
plant competition.  As a  general  rule,  tolerant
species  require less intensive treatments, while in-
tolerant species require more  intensive treatments.

                Specify Timing
      Procedural — All Resource Impacts
  Specify timing of control application and/or work
phases that are critical to quality control. Timing
should be specified in terms  of both calendar and
spatial  relationships.  Such  timing  specification
should  be  used for  vegetative establishment,
culvert  and bridge  installation, earth work, es-
tablishment of size, number,  and placement of ac-
tive areas, and the scheduling of activity on these
areas.

      Stabilizing Structures on Cut Slopes
            Mitigative — Bare Soil,
          Slope Configuration Changes
  A variety of engineering structures may be in-
stalled where the toes of unstable slopes have been
truncated by bank  cutting in streams, road cuts,
skid roads, or firelines. Cut banks and/or  fill slopes
at the toes of slopes can be counterbalanced with
rock to  stop mass soil wasting at toes of unstable
                                               H.64

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slopes and potential upslope mass failure. Specific
treatments  include:  Steel  cribbing structures,
gabions, corrugated pipe, and rock.
         Timely Drainage Maintenance
      Preventive — All Resource Impacts

  Keep   maintenance  current,  particularly  off
drainage facilities. Insure that drainage facilities
are functioning properly at all times, especially
prior to periods of heavy runoff.
  Much of the drainage maintenance work can be
done by personnel other than maintenance crews.
Quite often the only  "equipment"  needed is a
shovel.
        Timing of Chemical Application
     Preventive — Aerial Drift of Chemicals,
              Vegetation Changes

  Apply  chemicals  during  calm,  dry weather
 (mornings  and  evenings).  Little  drift  is en-
 countered if chemicals are applied during calm
 weather.  Rainstorms  can  wash freshly  applied
 chemicals into water.  Avoid high runoff periods
 when applying chemicals. Refer to "Chemical Ap-
 plications" control for  further considerations.
  Timing of Use of Off-Road, Heavy Equipment
 Preventive — Compaction, Water Concentration

   Analyze soil to determine its characteristics and
 define the soil  moisture limits for using heavy
 equipment.  Limit use of heavy equipment when
 soil moisture is high and thus reduce chances of soil
 compaction.  Include timing constraints  in con-
 tracts if applicable.
                  Trash Racks
       Preventive — Water Concentration

  Locate trash racks at, or upstream from, culvert
entrances to catch debris before it plugs culverts.
This can reduce bank cutting around culvert
entrances caused  by plugging  and reduces the
chance for water to overflow roads during high
water. Note, however, that with great amounts of
debris, trash racks are not effective; they may ac-
tually make the problem worse. Numerous  stan-
dard drawings exist. See Forest Service or State
highway  department.
      Type of Site Preparation Treatment
Preventive  —  Bare  Soil,  Compaction,  Excess
                    Water,
       Onsite Chemical Balance Changes,
Vegetative Changes, Slope Configuration Changes,
             Water Concentration
  Site preparation is used to create a favorable en-
vironment for tree establishment and to secure ac-
ceptable tree survival and  stocking. There  is a
broad range of site preparation treatments with a
wide range  of potential impacts. The treatment
chosen for a given site is governed  by  the site's
physical and residual stand characteristics, the
tree species to be planted, whether the trees can be
machine or  hand planted, and whether  regenera-
tion will be  by seedlings or seed. Site preparation
uses  hand and mechanical  methods, herbicides,
and fire, or  combinations of these treatments.
  The principle here is that many characteristics
will govern  what  site preparation treatments are
used. Several possible treatments can be applied to
a given  site; the  one  chosen depends  upon the
management goals for that site.
  Refer  to  Dissmeyer  and  Singer (1977)  and
Balmer  and others (1976) for more complete infor-
mation.

      Use Wind  Breaks or Uncut Timber
            to Prevent Wind Erosion
            Preventive — Bare  Soil
  Leave wind  breaks or uncut timber around
silvicultural and related activities in wind erosion
areas. These can  slow or disrupt wind currents
which could cause erosion. Disrupted wind currents
will drop suspended soil particles.

  Use Maximum Spacing and Minimum Strip
           Width in Site  Preparation
     Preventive — Bare Soil, Excess Water,
             Water Concentration
  Leave undisturbed  vegetation or ground cover
between site preparation  strips. Leave  the max-
imum width possible to meet silvicultural prescrip-
tions. Continuous blocks of bare soil will be broken
up, thus preventing water concentration and sur-
face soil loss.

                Waterside Area
    Preventive — Aerial Drift of Chemicals,
  Bare  Soil, Debris in Channel,  Excess  Water,
Streamside  Shading Changes, Water Concentra-
                     tion
  Waterside areas are  strips of vegetated land
                                              11.65

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where treatment is carefully controlled. Such zones
are often  located  between  cut,  site-prepared,
burned,  fertilized,  herbicided, and  pesticided
areas, roads, and streams. Vegetation in the water-
side area reduces amounts of debris, surface runoff,
erosion, and chemicals reaching the stream while
reducing the impact  of some management ac-
tivities on water temperatures.  Use mapping and
on-the-ground reconnaissance to identify aquatic
areas which, because of direction of flow, shoreline
arrangement, exposure, wind patterns, and related
phenomena,  are  susceptible  to  temperature
changes. Modify silvicultural prescriptions accor-
dingly.
  Provide shade on treated areas and in strategic
locations near riparian zones and water surfaces to
disrupt radiation patterns and slow air movement
into sensitive areas. Maintain temperature regimes
of the aquatic environment. Leave as much native
vegetation  on treated areas as possible.  Avoid
"total  cleanup" of  debris. Protect vegetation in
riparian areas and leave substantial windfirm trees
in areas  where they will  obstruct radiation onto
riparian zones and onto water, particularly in the
shallows.
  Refer to the "Directional Felling"  control for
harvesting timber in waterside areas.  The Forest
Service's State and Private Forestry group has in-
formation on proper layout and design of waterside
areas.

          Woody Debris Disposal Sites
       Preventive — Debris in Channel,
       Onsite Chemical Balance Changes
  Do not pile woody material or ash where it could
wash into streams.  Chemical  seep  from  wood
should not be allowed to reach water bodies.
  Downstream  culverts  and trash racks will need
less  maintenance and  organic matter will  be
prevented from changing the chemical balance in
streams. Very little is known about water pollution
caused by chemical leaching from wood.
                                              11.66

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                                  LITERATURE CITED
Balmer, W. E., H. L. Williston, G. E. Dissmeyer,
  and C. Pierce. 1976. Site preparation — why and
  how. U.S. Dep. Agric. For. Serv. Bull. 8 p. State
  and Private For., Southeast. Area, Atlanta, Ga.


Currier, J. B. 1974. Water quality effects of logging
  residue  decomposition  from  lodgepole  pine.
  Ph.D. diss. Colo. State Univ., Fort Collins. 152 p.

Dissmeyer, G.  E., and J.  R. Singer. 1977. Role of
  foresters in  the areawide waste  treatment
  management planning process. South.  J. Appl.
  For., Vol. 1 (No. 1). 5 p.


Howe, G. E. [n.d.] The evolutionary role of wildfire
  in the Northern Rockies and implications for
  research managers.  Tall Timbers  Fire  Ecol.
  Conf. No. 14 and Intermt. Fire Res. Counc. Fire
  and Land Manage. Symp. Proc. p.257-265.

Kochenderfer,  J. N. 1970. Erosion control on log-
  ging roads in the Appalachians. USDA For. Serv.
  Res. Pap. NE-158, 28 p. Northeast  Exp. Stn.,
  Upper Darby, Pa.
Lull, H. W. 1959. Soil compaction on forest and
  range lands. U.S. Dep. Agric. Misc. Publ. No.
  768, 33 p.

Ponce, S. L. 1974. The biochemical oxygen demand
  of Douglas-fir  needles and red alder leaves in
  stream water.  M.S. thesis. Oreg. State Univ.,
  Corvallis. 141 p.

Smith, D. M. 1977. The scientific basis for timber
  harvesting practices. J. Wash. Acad. Sci. 67(1)3-
  11.

Stone, E.  1973. The impact  of timber harvest on
  soils and water. Report of the President's Ad-
  visory Committee on Timber and the Environ-
  ment,  p. 427-467.  (Reprinted  by U.S.  Dep.
  Agric., For. Serv. June  1977.)

U.S. Department of Agriculture, Forest  Service.
  1977.  The  scientific base for  silviculture and
  management decisions  in  the  National Forest
  system.  (Selected papers  used as background
  material for testimony given by the Chief of the
  Forest Service to Congressional Committees in
  March 1976.) Unnumb. publ.,  59 p. U.S. Dep.
  Agric., For. Serv., Washington, D.C.
                                             11.67

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                   APPENDIX II.A: EXAMPLES  ILLUSTRATING
              VARIOUS USES OF  THE CONTROL OPPORTUNITIES
EXAMPLE ONE — MITIGATIVE CONTROLS
                     FOR
     A PREVIOUSLY DISTURBED SITE
  Example one procedure. — This example  il-
lustrates the  use  of the controls  procedure  to
prescribe mitigative controls for a previously dis-
turbed site (disturbed by man) so that silvicultural
activity can be accomplished  without exceeding
water quality objectives. (Fig. II.A.l illustrates this
application of the procedure.)

  This procedure should be run  several times,
thereby arriving at several choices for the manager.

  1. Simulate,   using  handbook  procedures,  or
    measure   watershed  condition  before
    silvicultural planning begins.
  2. If a previous disturbance (a road, a landing,
    etc.) is impacting water quality so that objec-
    tives are not met,  the  simulation will show
    where the  pollution is originating, how much
    pollution there is, and what kind of pollution
    is  being produced. Using  this  information,
    determine which variables within the simula-
    tion  procedure are  causing the  pollution.
    Then refer to table II.2 and relate the involved
   variables to the corresponding resource  im-
   pacts (bare soil, compaction, etc.). (To relate
   the resource impacts to the involved processes
   — increased runoff,  reduced infiltration,  etc.
   — refer to the definitions of the resource  im-
   pacts  in the "Discussion" section  of  this
   chapter.)
3.  Once the resource impacts are identified, refer
   to section B or section C, tables II.3 to 11.14 of
   this chapter for a list of controls that could
   mitigate the resource impacts. At this point, a
   mix of  such controls is selected.
4.  Then use section D for  a description of  the
   selected controls. Reference sources are listed
   in section D for  those controls needing an ex-
   panded, technical definition.
5.  Use section C to cross-reference the control
   opportunities  with  the  variables and
   procedures used in the handbook simulation.
6.  Simulate (using handbook  procedures)  the
   potential outcome of using the new mixture of
   mitigative controls to meet the  water quality
   objectives.
7.  If the water quality objectives  are not met,
   new mixes of mitigative controls will have to
   be chosen  and  simulated  again  using  the
   handbook procedures.
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    WATER
   QUALITY
OBJECTIVES MET
                 SIMULATE OR MEASURE
                EXISTING WATER QUALITY
  WATER
 QUALITY
OBJECTIVES
 NOT MET
                             RECOGNIZE THE SOURCE, QUANTITY AND TYPE
                               OF POLLUTION. IDENTIFY THE INVOLVED
                                      SIMULATION VARIABLES ^
                                USING TABLE 11.2, RELATE VARIABLES
                                  TO SPECIFIC RESOURCE IMPACTS
                                IDENTIFY AND LIST WATER RESOURCE
                             IMPACTS RESPONSIBLE FOR WATER QUALITY
                                    OBJECTIVES NOT BEING MET
                              IDENTIFY THOSE CONTROLS THAT COULD
                                 MITIGATE THE IMPACTS. REFER TO
                               SECTIONS B OR C (TABLES 11.3 TO 11.14)
                             OF THE CONTROL OPPORTUNITIES CHAPTER
                                  LOOK AT CONTROL DEFINITIONS
                              SO CONTROLS ARE FULLY UNDERSTOOD
                                         SEE SECTION D
                              DETERMINE WHICH SIMULATION ROUTINES
                               ARE AFFECTED BY NEW CONTROLS BY
                            CROSS REFERENCING CONTROL OPPORTUNITIES
                                  WITH VARIABLES USED IN EACH
                               SIMULATION ROUTINE. SEE SECTION C,
                                    TABLES II.3 THROUGH 11.14
                               SIMULATE USING DIFFERENT CONTROL
                                 MIXTURE AND ALTERED VARIABLES
                                 WATER
                                QUALITY
                             OBJECTIVES MET
             'WATERN
             QUALITY
           OBJECTIVES
            NOT MET
                                         CONTINUE OPERATION UNTIL WATER
                                           QUALITY OBJECTIVES ARE MET
                                           OR UNTIL NO MORE MITIGATIVE
                                        CONTROLS CAN FEASIBLY BE APPLIED
               Figure II.A.1—Example one procedure.
                          H.69

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  EXAMPLE TWO — CONTROLS IN THE
              FORMULATION
        OF SILVICULTURAL PLANS
  Example two procedure. — This example il-
lustrates the  use of the control as a reference to
help in the formulation of the initial silvicultural
plan. (Fig. n.A.2 illustrates this application of the
procedure.)
  This procedure  should  be run  several times,
thereby arriving at several choices for the manager.
  1.  List the resource impacts associated  with
     silvicultural activity by referring to section A,
     table II.l, of this chapter. For example, bare
     soil and  compaction might be associated with
     tractor skidding operations.
2.  Once  the  resource impact has been deter-
   mined, a list of controls which could prevent
   or mitigate each impact can be made by refer-
   ring to section B.

3.  Then go to section D for an expanded defini-
   tion of each control.

4.  Refer  to  section C for cross-correlation
   between the  control and the variable or
   variables it affects for simulation  of possible
   effects  on the stream.

5.  Narrow the control list to those controls most
   effective in preventing or mitigating resource
   impacts.

6.  Include the  most effective  controls in the
   proposed silvicultural plan.
                                              11.70

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 IDENTIFY RESOURCE IMPACTS ASSOCIATED
   WITH EACH PROPOSED SILVICULTURAL
 ACTIVITY BY REFERRING TO THE CONTROL
        OPPORTUNITIES CHAPTER
         (SECTION A, TABLE 11.1)
                 1
IDENTIFY CONTROLS WHICH COULD PREVENT
      OR MITIGATE EACH IMPACT BY
      REFERRING TO THE CONTROL
   OPPORTUNITIES CHAPTER (SECTION B)
  REFER TO SECTION D OF THE CONTROL
OPPORTUNITIES CHAPTER FOR A DEFINITION
OF EACH POTENTIAL CONTROL OPPORTUNITY
DETERMINE WHICH CONTROLOPPORTUNITIES
     AFFECT WHICH VARIABLES IN THE
   HANDBOOK SIMULATION PROCEDURE
  BY USING SECTION C TABLES 11.3 TO 11.14
 IN THE CONTROL OPPORTUNITIES CHAPTER
                 I
DETERMINE WHICH CONTROLOPPORTUNITIES
ARE THE MOST EFFECTIVE BY CALCULATING
    THE MAGNITUDE OF THE CONTROL
  OPPORTUNITY APPLICATION UPON THE
  SIMULATION PROCEDURE CONTAINING
        THE AFFECTED VARIABLE
    INCLUDE THE EFFECTIVE CONTROL
    OPPORTUNITIES IN THE PROPOSED
      SILVICULTURAL ACTIVITY PLAN
       Figure M.A.2.—Example two procedure.



                 11.71

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EXAMPLE THREE — ADDING CONTROLS
                WHEN PLANS
     DO  NOT  MEET WATER QUALITY
                OBJECTIVES
  Example three procedure. — This example il-
lustrates use of the controls procedure as a way to
add new control opportunities to the silvicultural
plan if the plan has  been shown, through simula-
tion, to fall short of the water quality objectives.
(Fig.  n.A.3  illustrates  this application of  the
procedure.)
  This procedure should be run several times, ar-
riving at several control mixes that all meet the
water quality objectives, to  give  the  manager a
choice.
   1.  Simulate  (using  the handbook  simulation
      procedure) the water quality based upon the
      proposed silvicultural plan.
   2.  If  the  simulation procedure shows the
      silvicultural  plan  to meet the established
      water quality  objectives,  then  no further
      reference needs to be made to the controls
      chapter. If the silvicultural  plan is shown,
      through simulation, not to  meet  the  es-
      tablished water quality objectives, then  a
      new mix of controls should be selected using
      the controls procedure.

   3.  If objectives are not met, the simulation will
      show where the pollution is originating, how
      much pollution there is, and what kind of
      pollution is being produced. Using this infor-
      mation, first  determine  which  variables
      within the simulation procedure are causing
      the pollution. Then, refer  to table II.2 and
      relate the involved variables to  the cor-
      responding resource impacts (bare soil, com-
      paction, etc.) (To relate the resource impacts
      to the involved processes — increased runoff,
      reduced infiltration, etc.  —  refer to the
      definitions of the  resource impacts in the
      "Discussion" section of this  chapter.)

   4.  When the water resource impacts have been
      identified, refer to  section  B or section  C,
      tables II.3 to n.14, for a list of controls that
      could prevent the water resource impacts. At
      this point, a mix of such controls is selected
      and is added to, or used to replace, parts of
      the  silvicultural  plan. Determine  which
      variables should be altered  by referring to
      the tables in section C. The values of the
    variables should be altered to reflect the new
    control mixture before the next simulation.
    For example, if a simulation  shows too much
    heat resulting from too much sunlight strik-
    ing the water surface of a stream, the next
    step would  be  to check the cutting block
    design in the cutting and logging portions of
    the proposed silvicultural plan to find out
    which parts of the plan are directed toward
    the problem. If the plan calls for  cutting
    blocks to be located too close to the stream,
    then a new control relating to cutting block
    design and location should be added to the
    plan to prevent water temperature increase.
 5.  Then use section D for description of the
    selected  controls.   Reference  sources  are
    listed in section D for those controls needing
    an expanded, technical definition.
 6.  Use section C to cross-reference the control
    opportunities  with  the  variables  and
    procedures used in the handbook simulation.
 7.  Simulate (using handbook procedures) the
    potential outcome of using the new mixture
    of  preventive controls to meet the water
    quality objectives.
 8.  If the  water quality objectives  are met, no
    further simulations using different mixtures
    of controls are needed (unless economics dic-
    tate several simulations). If the water quality
    objectives are not met, new mixes of controls
    will have to  be chosen and simulated again
    using the handbook procedures.
 9.  If after the addition of preventive controls
    the objectives are not met,  the simulation
    will show where the  pollution is originating,
    how much pollution there is, and what kind
    of pollution is being produced. Using this in-
    formation, determine which variables within
    the simulation  procedure are  causing the
    pollution. Then refer to table II.2 and relate
    the involved variables to the corresponding
    resource  impacts (bare  soil,  compaction,
    etc.). (To relate the resource impacts to the
    involved  processes  — increased  runoff,
    reduced  infiltration,  etc. — refer  to the
    definitions of the resource impacts  in the
    "Discussion."

10.  When the water resource impacts  have been
    identified, refer  to section  B or section C,
    tables II.3 to 11.14, for a list  of controls that
    could mitigate the resource impacts. At this
    point, a mix of such controls is selected and
                                               11.72

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           WATER
          QUALITY
       OBJECTIVES MET
                SIMULATE WATER QUALITY RESULTING FROM
                 PROPOSED SILVICULTURAL ACTIVITY PLAN
  WATER
  QUALITY
OBJECTIVES
  NOT MET
                                       RECOGNIZE THE SOURCE, QUANTITY
                                        AND TYPE OF POLLUTION. IDENTIFY
                                      THE INVOLVED SIMULATION VARIABLES
                                       USING TABLE 11.2, RELATE VARIABLES
                                         TO SPECIFIC RESOURCE IMPACTS
                                       IDENTIFY AND LIST WATER RESOURCE
                                    IMPACTS RESPONSIBLE FOR WATER QUALITY
                                           OBJECTIVES NOT BEING MET
                                     IDENTIFY THOSE CONTROLS THAT COULD
                                        PREVENT THE IMPACTS. REFER TO
                                      SECTIONS B OR C (TABLES 11.3 TO 11.14)
                                    OF THE CONTROL OPPORTUNITIES CHAPTER
                                         LOOK AT CONTROL DEFINITIONS
                                     SO CONTROLS ARE FULLY UNDERSTOOD.
                                                SEE SECTION D
                                    DETERMINE WHICH SIMULATION ROUTINES ARE
                                     AFFECTED BY NEW CONTROLS BY CROSS
                                    REFERENCING CONTROL OPPORTUNITIES WITH
                                      VARIABLES USED IN EACH SIMULATION
                                            ROUTINE. SEE SECTION C,
                                            TABLES II.3 THROUGH 11.14
                                      SIMULATE USING DIFFERENT CONTROL
                                        MIXTURE AND ALTERED VARIABLES
Figure M.A.3.—Example three procedure.
                                        WATER
                                       QUALITY
                                    OBJECTIVES MET
              WATER
             QUALITY
           OBJECTIVES
            NOT MET
                                    11.73

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    RECOGNIZE THE SOURCE QUANTITY
    AND TYPE OF POLLUTION. IDENTIFY
  THE INVOLVED SIMULATION VARIABLES
   USING TABLE 11.2, RELATE VARIABLES
    TO SPECIFIC RESOURCE IMPACTS
   IDENTIFY AND LIST WATER RESOURCE
IMPACTS RESPONSIBLE FOR WATER QUALITY
       OBJECTIVES NOT BEING MET
 IDENTIFY THOSE CONTROLS THAT COULD
    MITIGATE THE IMPACTS. REFER TO
   SECTIONS B OR C (TABLES 11.3 TO 11.14)
OF THE CONTROL OPPORTUNITIES CHAPTER
     LOOK AT CONTROL DEFINITIONS
  SO CONTROLS ARE FULLY UNDERSTOOD.
            SEE SECTION D
DETERMINE WHICH SIMULATION ROUTINES ARE
  AFFECTED BY NEW CONTROLS BY CROSS
REFERENCING CONTROL OPPORTUNITIES WITH
   VARIABLES USED IN EACH SIMULATION
        ROUTINE. SEE SECTION C,
        TABLES II.3 THROUGH 11.14
  SIMULATE USING DIFFERENT CONTROL
    MIXTURE AND ALTERED VARIABLES
    WATER
    QUALITY
OBJECTIVES MET
   WATER
  QUALITY
OBJECTIVES
  NOT MET
                  CONTINUE OPERATION UNTIL
                  WATER QUALITY OBJECTIVES
                      ARE MET OR UNTIL
                NO MORE MITIGATIVE CONTROLS
                   CAN FEASIBLY BE APPLIED
   Figure H.A.3.—Example three procedure — continued.
                 n.74

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11.
is added to the silvicultural plan. For exam-
pie, if a simulation shows too much sediment
resulting from  road related surface erosion,
the next step would be to check the transpor-
tation portion of the silvicultural plan to find
out  what  controls  directed  toward  the
problem are part of the plan. If plans call for
the road surface to be  "dirt," then a new con-
trol (Protect Road Surface Area) can be ad-
ded to the plan to mitigate the  surface ero-
sion.
Then use section D for a description of the
selected controls.  Reference  sources  are
listed in section D for those controls needing
an expanded,  technical definition.
12.  Use section C to cross-reference the control
    opportunities  with  the  variables  and
    procedures used in the handbook simulation.
13.  Simulate (using handbook procedures)  the
    potential outcome of using the new mixture
    of  mitigative controls  to meet the water
    quality objectives.
14.  If the water quality objectives are met, no
    further simulations using different mixtures
    of controls are needed (unless economics dic-
    tate several simulations). If the  water
    quality objectives are not met, new mixes of
    controls will  have  to be  chosen  and
    simulated   again using  the  handbook
    procedures.
                                            11.75

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              Chapter III

         HYDROLOGY
this chapter was prepared by the following individuals:
           Charles A. Troendle
             Charles F. Leaf

         with major contributions from:
             W. Toby  Hanes
            Mark R. Spearnak
            Ronald D. Tabler
             James L.  Smith
            Richard C. Patten

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                               CONTENTS
                                                                     Page

INTRODUCTION	  HI.l
DISCUSSION: OVERVIEW OF THE HYDROLOGIC CYCLE	  HI.2
    DISPOSITION OF PRECIPITATION	  m.4
      Effect Of The Canopy On Water Losses	  m.4
      Effects Of Litter Cover On Disposition Of Precipitation 	  HI.6
    MOVEMENT OF WATER INTO THE SOIL WATER COMPLEX	  ni.6
      Infiltration Of Water 	  HI.6
        Factors Affecting Infiltration Rates — A Summary	  HI.6
        Evaluation Of Infiltration And Role Of The Soil Profile 	  ni.6
      Dissipation Of Water In The Soil Water Complex	  HI.7
        Transpirational Depletion Of Soil Water 	  HI.8
        Soil Moisture Regimes	  El.8
        Streamflow Generating Processes	  HI.9
        Factors Affecting Individual Storm Response 	  HI. 10
DISCUSSION: IMPACT OF SILVICULTURAL ACTIVITIES ON THE
  HYDROLOGIC CYCLE 	  ffl.12
    THE BASIC HYDROLOGIC PROCESSES  AFFECTED BY
    SILVICULTURAL ACTIVITIES	  HI.14
      General Consideration — Vegetative Cover	  HI. 14
        Forest Cover Density (Cd)	  HI. 14
        The Leaf Area Index (LAI)	  HI. 14
      Effects  Of Silvicultural Activities On Precipitation	  HI. 15
        Effect Of Silvicultural Activities On Precipitation As Rainfall	  HI. 15
        Effect Of Silvicultural Activities On Precipitation As Snowfall	  HI. 15
        Effect Of Silvicultural Activities On Snowmelt Processes	  HI. 17
        Effects Of Silvicultural Activities On Infiltration Rates	  HI. 18
      Influence Of Silvicultural Activities On Evapotranspiration	  HI 18
    SUMMARY 	  ni!l9
PROCEDURE: EXPLANATION OF THE METHODOLOGY FOR
  PREDICTING IMPACTS OF SILVICULTURAL ACTIVITIES
  ON THE HYDROLOGIC CYCLE	  ra 20
    PROCEDURAL FLOW CHART	  ni 20
    PROCEDURAL DESCRIPTION	  nL20
      Use Of Site Specific Data	  HI 20
      Use Of The Annual Or Seasonal Hydrologic Budget	  HI 21
      No Quantification On The Hydrologic Impact Of Mechanical Disturb-
       ances   	  ni.21
      The Importance Of Onsite Response	  HI 21
      Use Of Models To Simulate Hydrologic Response	  HI 21
       Evapotranspiration	  HI 22
       Outflow 	  m'_22
       Soil Moisture	  HI 23
      Definitions Used 	  HI 23
                                    HLii

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                                                             Page
PROCEDURAL DESCRIPTION: DETERMINING EVAPOTRANSPIRATION
  AND WATER AVAILABLE FOR STREAMFLOW (ET ESTIMATION)
  (RAIN DOMINATED REGIONS) 	  ffl.24
    METHODOLOGY USED FOR DETERMINING EVAPOTRANSPIRA-
     TION AND WATER AVAILABLE FOR STREAMFLOW 	  EI.24
      Examples: Determining Evapotranspiration And Water
        Available For Streamflow	  El.35
        Example 1. The Needle Branch Watershed	  HI.38
        Example 2. The Coweeta Watershed	  HI.38
        Example 3. The Grant Watershed	  HI.41
PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
  IN STREAMFLOW (STREAMFLOW ESTIMATION) (RAIN DOMINATED
  REGIONS)	  111.45
    PROCEDURAL FLOW CHART	  111.45
      Examples: Determining Potential Changes In Streamflow	  111.52
PROCEDURAL DESCRIPTION: DETERMINING EVAPOTRANSPIRATION
  AND WATER AVAILABLE FOR  STREAMFLOW (ET ESTIMATION)
  (SNOW DOMINATED REGIONS)	  HI.62
    REGIONAL DESCRIPTIONS	  HI.62
     New England/Lake State Hydrologic Region (1) 	  El.62
     Rocky Mountain/Inland Intermountain Hydrologic Region (4)	  El.62
     Pacific Coast Hydrologic Provinces (5,6,7)	  111.63
    LIMITATIONS  AND  PRECAUTIONS: PROBLEMS ASSOCIATED
     WITH HYDROLOGIC MODELING FOR SNOW REGIONS 	  ni.64
    PROCEDURAL FLOW CHART	  EI.64
      Example:  Determining  ET And  Water  Available For Annual
      Streamflow (Snow Dominated Regions) 	  EI.95
PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
  IN STREAMFLOW  (STREAMFLOW ESTIMATION)  (SNOW
  DOMINATED REGIONS)	  HI.97
   PROCEDURAL FLOW CHART	  HI.97
      Example:  Determining Streamflow Timing And Volume Changes
      With Silvicultural Activities, Excluding "New England/Lake States
      (Region 1)"	  EI.122
PROCEDURAL  DESCRIPTION: DETERMINING  SOIL  MOISTURE
  CHANGES AND INDIVEDUAL EVENT STORM RESPONSE	  El.124
   SOIL MOISTURE CHANGES (RAIN DOMINATED REGIONS)	  IE.125
   SOIL MOISTURE CHANGES  (SNOWFALL DOMINATED REGIONS) ..  IE. 128
   PREDICTING INDIVIDUAL STORM RESPONSES	  IE. 140
     Basis For Evaluating The Design Event	  IE.140
     Selecting The Return Period For The Design Event	  El. 141
     Selection Of Precipitation Input	  IE. 141
CONCLUSIONS	  m-142
LITERATURE CITED 	  IIL143
APPENDIX III.A: EFFECT OF LARGE OPENINGS ON EVAPORATION
  AND TRANSPORT OF BLOWING SNOW	  EI.148
APPENDIX m.B:  HYDROLOGIC  MODELING	  EI.153
  PHILOSOPHY	  BI.153
  SELECTION OF MODELS USED	  EI.153
  GENERAL PRINCE>LES FOR APPLICATION AND USE OF MODELS .  BI.154
   Subalpine  Water Balance Model Description  	  El.154
     Input Requirements For WATBAL	  BI.155
                               IH.iii

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                                                                     Page
                  I

    PROSPER Model	    m.155
     Input Requirements For PROSPER	    HI.157
    Model Output 	    ffl.157
APPENDIX m.C: CALIBRATIONS OF SUBALPINE WATER BALANCE
  MODEL	    HI.159
    INDEX WATERSHEDS	    HI.159
     Rocky Mountain/Intermountain Hydrologic Region (4)	    HI. 159
       Model Calibration	    HI.160
     Continental/Maritime Hydrologic Province (6)	    HI. 162
       UCSL Simulation Validity	    HI.164
     Central Sierra Hydrologic Province (7)	    HI. 164
       CSSL Simulation Validity	    HI.166
       Alternate Simulations (CSSL)	    HI.167
     Northwest Hydrologic Province (5)	    El.167
       WBSL Simulation Validity	    ffl.168
APPENDIX m.D: CALIBRATION AND  VALIDATION SUMMARY FOR
  SITES MODELED WITH PROSPER 	    HI.169
    THE APPALACHIAN HIGHLANDS AND MOUNTAIN REGION (2) ..    HI. 169
       Leading Ridge, Pennsylvania	    ni.169
       Fernow, West Virginia	    HI.171
       Walker Branch, Tennessee	    ffi.171
       Coweeta, North Carolina	    ffl.171
    THE GULF AND ATLANTIC COASTAL PLAIN/PIEDMONT
     REGION (3)	    EI.172
       White Hall, Georgia	    HI.172
       Oxford, Mississippi	    ni.172
    PACIFIC COAST HYDROLOGIC PROVINCES — NORTHWEST (5),
     CONTINENTAL/MARITIME (6), AND CENTRAL SIERRA (7)
     LOW ELEVATION 	    HI.173
       H. J. Andrews, Oregon 	    HI.173
                                     m.iv

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                          LIST OF EQUATIONS



Equation                                                           Page

m.i    pg=R0+Et+AS   ............................................. m.2

m.2    pf=(i-B/A)  .................................................. m.2

m.s    Poadj=i + (po-i)(.5o/X)       ................................. m.i7

ffl.4    ETA = ETB X COT X RD X Silvicultural State Area ................ m.33

             i
m.5    Qw= 2 (Q_X Prescription Area/Watershed Area)                  m.35
           P=l  p                              ...................

m.6    AR = Qw      .................................................. HI.48
             QR
HI.7    Qi=QR.XAR  ................................................. EI.48
m.s    RD =   w   [[[ m.49
            RDA
m.9   AQi = bb +btQi + b2CD + b3AS + b4CD   ........................ HI.49


nuo   Qaverage=f.5(Qi+QN)+   ^
               L             i=2

m.ll   AQi=b0 + b1Qi+b2CD

           + b3AS + b4RD + b5SineDay   .............................. HI.51



IH.12   Sine Day = Sin /360 x Day # \  +2  ........................... ffl 51
                     \     365    /

TTT 10         1 ~PoadjX
HI.13   pf -- - - - -  .......................................... HI.77
               1   2^.

             n
ffl.14   ETA= S
                           	 m.94

              35
in.15   Qp=   2   QT   	 ffl.94
            T=30
TTT     , .,	(inches) (watershed area in acres)	   	 III.120
lll.lo   vClsj  —
               (12 in/ft) (1.98) (number of days in interval)

HI.A.1  Q =  |5000/(1 + 250 t^)  0.87P3 - 0.25

                                                     1
            + (0.13P3 - 0.155) a  + (0.355 - 2P3/3)b - P3c/3j   	  m.148

EI.A.2  Qlogs = P3D - 1.53Q - 4.67P3H - 0.355D = 3.255H  	 m.149


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                              LIST OF FIGURES
Figure

m.l.  —The hydrologic cycle consists of a system of water storage compart-
           ments and the  solid,  liquid,  or gaseous flows of water within and
           between the storage points	 HI.3
ffl.2.  —Significance of wind-caused snow redistribution in the subalpine zone HI.5
in.3.  —The relationship between streamflow, soil moisture, and evaporative
           demand in a deciduous forest in a humid environment	 ni.8
HI.4.  —Downslope  movement of water on a forested upland watershed	 ni.10
III.5.  —A time-lapse view of a basin showing expansion of the source area and
           the  channel system during a storm	 HI. 11
III.6.  —Snow  retention as a function of size  of clearcut	 HI. 16
in.7.  —New growth does  not affect total  snow storage in this lodgepole pine
           area of the Fraser Experimental Forest	 HI.16
ELS.  —Relationships showing evaportranspiration as  a function of available
           soil  water 	 HI. 18
ffl.9.  —Flow  chart  of methodology for determining evapotranspiration and
           water available  for annual streamflow in rainfall dominated regions jn.25
III.9a. —Hydrologic  regions and provinces	 HI.26
IH.IO. —Simulated seasonal evapotranspiration for the Pacific Coast hydrologic
           provinces	 ni.28
IE. 11. —Average  evapotranspiration  for  the  Appalachian Mountain and
           Highlands hydrologic  region (2) by latitude  	 El.28
m.12. —Seasonal average evapotranspiration for the Eastern Coastal Plain and
           Piedmont hydrologic region (3)	 ni.29
ni.13. —Leaf area index - basal area relationship for hardwood stands in the Ap-
           palachian Mountain and  Highlands region	 HI. 30
HI.14. —Leaf area index   basal area relationship for conifer stands in the Ap-
           palachian Mountain and  Highlands region	 HI. 30
ni.15. —Evapotranspiration modifier coefficients, for all seasons, for the Pacific
           Coast hydrologic provinces	 111.31
in.16. —Evapotranspiration  modifier coefficients, for all seasons, for the Ap-
           palachian Mountains  and Highlands hydrologic region (2)	 HI.32
m.17. —Evapotranspiration  modifier coefficients,  for  all  seasons,  for  the
           Eastern Coastal Plains and Piedmont hydrologic region (3)	 HI 32
III.18. —Root  depth modifier  coefficients,  by season, for  the Pacific  Coast
           hydrologic provinces	 HI.34
IE.19. —Root depth  modifier coefficients, by season, for the Appalachian Moun-
           tains and Highlands hydrologic regions (2)	 HI.34
ITL20. —Root depth modifier coefficients,  by season, for the Eastern Coastal
           Plains and Piedmont  hydrologic regions (3)  	 HI 34
                                       m.vi

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                                                                             Page
EI.21.  —Flow chart of methodology for determining 7-day flow duration curve
           and  change in streamflow for  specific flow  change  for  rainfall
           dominated regions  	  ni.46
111.22.  —Potential  excess water available for streamflow, 7-day flow duration
           curve for Pacific, Appalachian, and Eastern Coastal regions	  El.47
ni.22a.—Pre- and  post-silvicultural  activity 7-day  flow  duration curve  for
           Needlebranch	  El 59
III.22b.—Pre- and post-silvicultural  activity 7-day flow duration  curve for
           Coweeta	  EI.60
EI.22c.—Pre- and post-silvicultural activity 7-day flow duration curve for Grant
           Memorial Forest Watershed	  El.61
EI.23.  —Flow chart of methodology for determining water available for annual
           streamflow, snow dominated regions	  El.67
EI.24.  —Precipitation-evapotranspiration  relationships  for  Rocky  Moun-
           tain/Inland Intermountain hydrologic region (4),  winter season, by
           energy aspect	  EI.79
ni.25. —Precipitation-evapotranspiration  relationships  for Rock  Moun-
           tain/Inland Intermountain hydrologic region (4),  spring season, by
           energy aspect	  EI.79
EI.26.  —Precipitation-evapotranspiration  relationships  for  Rocky  Moun-
           tain/Inland Intermountain  hydrologic region (4), summer and fall
           season,  by energy aspect	  EI.80
111.27.  —Precipitation-evapotranspiration  relationships  for  the   Northwest
           hydrologic province (5), early winter season, by energy  aspect  ....  EI.80
EI.28.  —Precipitation-evapotranspiration  relationships  for  the   Northwest
           hydrologic province (5), late winter season, by energy aspect 	  111.81
EI.29.  —Precipitation-evapotranspiration  relationships  for  the   Northwest
           hydrologic province (5), spring season,  by energy  aspect	  El.81
IE.30.  —Precipitation-evapotranspiration  relationships  for  the   Northwest
           hydrologic  province (5), summer and fall season,  by energy aspect  El.82
EI.31.  —Precipitation-evapotranspiration relationships  for  the Continental/
           Maritime  hydrologic province (6), winter season,  by energy aspect  EI.82
EI.32.  —Precipitation-evapotranspiration relationships  for  the Continental/
           Maritime  hydrologic province (6), spring season,  by energy  aspect  EI.83
111.33.  —Precipitation-evapotranspiration relationships  for  the Continental/
           Maritime  hydrologic  province (6),  summer  and fall  seasons,  by
           energy aspect	  EI.83
EI.34.  —Precipitation-evapotranspiration relationships for the Central Sierra
           hydrologic province (7), winter season, by energy aspect	  El.84
EI.35.  —Precipitation-evapotranspiration relationships for the Central Sierra
           hydrologic province (7), later winter season, by energy  aspect	  III.84
ni.36.  —Precipitation-evapotranspiration relationships for the Central Sierra
           hydrologic province (7), spring season, by energy aspect	  El.85
111.37.  —Precipitation-evapotranspiration relationships for the Central Sierra
           hydrologic province (7), summer and fall season, by energy aspect  III.85
III.38. —Precipitation-evapotranspiration  relationships for the  New
           England/Lake States hydrologic region (1), fall-early winter season,
           by energy aspect	  111.86
                                        Ill.vii

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                                                                              Page

III.39.  —Precipitation-evapotranspiration  relationships  for  the  New
           England/Lake States hydrologic region (1), later winter-early spring
           season, by energy aspect	   ni.86
III.40.  —Precipitation-evapotranspiration  relationships  for  the  New
           England/Lake States hydrologic region (1), growing season, by energy
           aspect 	   HI.87
ffl.41. —Basal area-cover density relationships for the Rocky Mountains/Inland
           Intermountain hydrologic region (4) — spruce-fir, lodgepole pine, and
           ponderosa pine for stem diameter 4 inches dbh	   ffi.88
ffl.42. —Basal area-cover density  relationships for the Continental/Maritime
           hydrologic province  (6)	   HL89
m.43. —Basal area-cover density relationships for the Central Sierra  hydrologic
           province (7) 	   m.89
ffl.44. —Basal area-cover density  relationships for the Northwest  hydrologic
           province (5) 	   HI.90
ni.45. —Basal area-cover density relationships for the  New England/Lake
           States hydrologic region (1)	   ffl.90
ffl.46. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Rocky  Mountain/Inland Intermountain hydrologic
           region (4) 	   EI.91
ffl.47. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Continental/Maritime hydrologic province (6)  high
           and intermediate energy aspects — spring, summer, and fall seasons   HI.91
IE.48. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Continental/Maritime hydrologic province (6)  high
           and intermediate energy aspects —  winter season	   HI.91
ni.49. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Continental/Maritime hydrologic province (6) low
           energy aspects  — all seasons	
in.50. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Central Sierra hydrologic province (7)  intermediate
           and low energy aspects  — early and late winter seasons	   ni.92
m.51. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Central Sierra hydrologic province (7)  intermediate
           and low energy aspects  — spring,  summer,  and fall seasons	   ni.92
ni.52. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Central Sierra hydrologic province (7) high energy
           aspects — spring, summer, and fall seasons	   HI. 92
ni.53. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Central Sierra hydrologic province (7) high energy
           aspects — early and late winter seasons 	   HI 92
ffl.54. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Northwest hydrologic province (5) all energy aspects
           — spring, summer,  and fall seasons	   ni.93
ni.55. —Evapotranspiration modifier  coefficients  for forest  cover  density
           changes for the Northwest hydrologic province (5) all energy aspects
           — early and late winter seasons	   111.93
                                       Hl.viii

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                                                                               Page
IE.56. —Evapotranspiration  modifier  coefficients  for  forest  cover  density
           changes for the New England/Lake States hydrologic region (1) all
           energy aspects — all seasons	   ni.93
IE.57. —Flow chart of methodology for calculation of composite hydrograph and
           7-day flow duration curve,  snow dominated regions	   HI. 98
III.58. —Potential water excess distribution graphs for Rocky Mountain/Inland
           Intermountain hydrologic region (4) — baseline conditions, all energy
           aspects	   ni.104
ni.59. —Potential water excess distribution graphs for Rocky Mountain/Inland
           Intermountain hydrologic region (4) — treated conditions, low energy
           aspects	   ni.105
in.60. —Potential water excess distribution graphs for Rocky MountainAnland
           Intermountain  hydrologic  region  (4) —  treated  conditions,  in-
           termediate energy aspects  	   HI. 105
in.61. —Potential water excess distribution graphs for Rocky Mountain/Inland
           Intermountain  hydrologic  region (4) —  treated conditions,  high
           energy aspects	   HI.106
ffl.62. —Potential water excess distribution graphs for Continental/Maritime
           hydrologic region (6) — baseline conditions, all energy aspects ....   jjj ^gg
in.63. —Potential water excess distribution graphs for Continental/Maritime
           hydrologic region (6) — treated conditions, low energy aspects ....   m 109
111.64. —Potential water excess distribution graphs for Continental/Maritime
           hydrologic region (6) — treated conditions, intermediate  energy
           aspects	   ffl.109
in.65. —Potential water excess distribution graphs for Continental/Maritime
           hydrologic region (6) — treated conditions, high energy aspects .. .   HI. 110
111.66. —Potential water excess distribution graphs for Central Sierra hydrologic
           region (7) — baseline conditions, all energy aspects	   El. 110
ni.67. —Potential water excess distribution graphs for Central Sierra hydrologic
           region (7) — treated conditions, low energy aspects	   HI. 114
111.68. —Potential water excess distribution graphs for Central Sierra hydrologic
           region (7) — treated conditions, intermediate energy aspects 	   HI. 114
111.69. —Potential water excess distribution graphs for Central Sierra hydrologic
           region  (7) — treated conditions, high energy aspects	    ni.115
111.70. —Potential water excess distribution graphs for the Northwest hydrologic
           region  (5) — baseline conditions, all energy aspects	    HI. 115
IE.71. —Potential water excess distribution graphs for the Northwest hydrologic
           region (5) — treated conditions, low energy aspect	    jjj j^g
ni.72. —Potential water excess distribution graphs for the Northwest hydrologic
           region (5)  — treated  conditions, intermediate energy aspect	    HI.116
IE.73. —Potential water excess distribution graphs for the Northwest hydrologic
           regions  (5) — treated conditions, high energy aspects	    El.117

ni.74. —Potential excess water flow duration curve for the New England/Lake
           States  hydrologic region (1)  — baseline conditions,  all  energy
           aspects	    EI.121
EI.75. —Potential excess water flow duration curve for the New England/Lake
           States  hydrologic region  (1)  — treated  conditions, low  energy
           aspects	    HI. 121
                                         ffl.ix

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                                                                              Page
III.76.  —Potential excess water flow duration curve for the New England/Lake
           States  hydrologic  region  (1)  — treated conditions,  intermediate
           energy  aspects	 ITI.121
in.77.  —Potential excess water flow duration curve for the New England/Lake
           States  hydrologic  region  (1)  —  treated conditions,  high  energy
           aspects	 ni.122
III.78.  —Average simulated soil moisture deficit, root zone only (upper 3 feet),
           for the Pacific Coast hydrologic provinces	 HI.126
III.79.  —Average simulated soil moisture deficit, root zone only (upper 3 feet),
           for the Appalachian Mountain and Highlands hydrologic region (2) HI. 126
111.80.  —Average simulated soil moisture deficit, root zone only (upper 3 feet),
           for the Eastern Coastal Plain  and Piedmont hydrologic region (3) . HI. 126
ni.81.  —Seasonal soil moisture deficit modifier coefficients for the Pacific Coast
           hydrologic provinces	El. 127
III.82.  —Seasonal  soil moisture deficit modifier coefficients for the Appalachian
           Mountains and Highlands hydrologic region  (2) 	HI. 127
IE.83.  —Seasonal soil  moisture  deficit modifier coefficients for the Eastern
           Coastal Plains and Piedmont  hydrologic region  (3)	 III.128
111.84.  —Baseline  soil water requirement relationships  for the Rocky Moun-
           tain/Inland Intermountain region (moderate soil depth) 	 HI. 129
111.85.  —Seasonal  soil moisture  recharge  requirements  for the Rocky Moun-
           tain/Inland  Intermountain  hydrologic  region  (4)  — low energy
           aspects (high north)	 HI.129
III.86.  —Seasonal  soil moisture  recharge requirements  for the Rocky Moun-
           tain/Inland  Intermountain  hydrologic  region  (4) —  high energy
           aspects (low south) 	 El.130
111.87.  —Seasonal  soil moisture  recharge  requirements  for the Rocky Moun-
           tain/Inland  Intermountain  hydrologic region (4)  —  intermediate
           energy  aspects	 El. 130
EI.88.  —Baseline seasonal soil moisture recharge requirements for the Continen-
           tal/Maritime hydrologic province (6) — all energy aspects	 El. 131
111.89.  —Seasonal  soil  moisture  recharge requirements for the  Continental/
           Maritime  hydrologic province (6) — low energy aspects	 El. 132
IE.90.  —Seasonal  soil  moisture requirements  for  the  Continental/Maritime
           hydrologic province (6) — intermediate energy aspects	 EL 132
IE.91.  —Seasonal soil  moisture  recharge requirements for the  Continental/
           Maritime hydrologic province (6) — high energy aspects  	 jjj 133
El.92.  —Baseline seasonal soil moisture recharge requirements for the Central
           Sierra hydrologic province (7) — all energy aspects	 El.133
IE.93.  —Seasonal  soil moisture  recharge requirements  for the  Central Sierra
           hydrologic province (7) — low energy aspects 	 El. 134
IE.94.  —Seasonal  soil moisture  recharge requirements  for the  Central Sierra
           hydrologic province (7) — intermediate energy aspects	 El. 134
EI.95.  —Seasonal  soil moisture  recharge requirements  for the  Central Sierra
           hydrologic province (7) — high energy aspects	 El. 135
III.96.  —Baseline  seasonal  soil moisture recharge  requirements for  the
           Northwest hydrologic province (5) — all energy aspects	 El. 136
                                       m.x

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                                                                          Page
in.97. —Seasonal  soil moisture recharge requirements  for  the  Northwest
          hydrologic  province (5) — low energy aspects  	 HI. 136
ni.98. —Seasonal  soil moisture recharge requirements  for  the  Northwest
          hydrologic  province (5) — intermediate energy aspects 	  HI. 137
ni.99. —Seasonal  soil moisture recharge requirements  for  the  Northwest
          hydrologic  province (5) — high energy aspects	 HI. 137
IE.100.—Baseline seasonal soil moisture  recharge requirements for the New
          England/Lake States hydrologic region (1) — all energy aspects  .. HI. 138
III.101.—Seasonal soil moisture recharge  requirements for the  New
          England/Lake States hydrologic region (1) — low energy aspects .. El. 138
III.102.—Seasonal soil moisture recharge  requirements for the  New
          England/Lake States hydrologic region (1) — intermediate energy
          aspects	 El. 139
III.103.—Seasonal soil moisture recharge  requirements for the  New
          England/Lake States hydrologic region (1) — high energy aspects . HI. 139
III.A.l.—General pattern of snow accumulation in large clearcut blocks	 HI. 148
in.A.2.—Cinnabar Park, Medicine Bow National Forest	 HI. 150
ni.A.3.—Snowglades forming downwind of clearcut blocks on the Medicine Bow
          National Forest	 HI.151
HLA.4.—Residual timber on downwind side of clearcut	 III. 152
m.A.5—Windfall on lee side of 1972-73 clearcut	 HI. 152
m.B.l.—General flow  chart of subalpine Water Balance Model WATBAL model HI. 154
m.B.2.—Schematic of PROSPER	 HI. 156
m.C.l.—Base  map for  Wolf  Creek  watershed, San Juan  National  Forest,
          hydrologic  subunits 	 HI. 160
m.C.2.—Extent of forest cover on Wolf Creek watershed  	 III. 161
                                     m.xi

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                                LIST OF TABLES
Number                                                                    Page

ELI. —Increases  in water  yield  following  forest  cutting,  by  forest type,
          geographic location, and type of cutting 	El. 12
III.2. —Ranges of forest cover density and transmissivity	III. 14
IE.3. —Least square  coefficients  for equation  III.9 for simulated  potential
          change  in water  available for streamflow for the  Pacific  Coast
          provinces	 III.49
III.4. —Least square  coefficients  for equation  in.9 for simulated  potential
          change in water available for streamflow for the Appalachian Moun-
          tains and Highlands  	HI.50
III.5. —Least square  coefficients  for equation  III.9 for simulated  potential
          change in water available for streamflow for the Coastal Plains/Pied-
          mont 	 111.50
ni.6. —Sine of day values (S) for use with flow prediction equation IE. 11. Where
          S= sin (360 x day #/365)  +2  	 111.51
III.7. —Least square  coefficients  for equation  El. 11 for the  Pacific  Coast
          provinces — low elevation	 111.52
IE.8. —Least square coefficients for equation EI.ll for the Appalachian Moun-
          tains and Highlands  	 IE.52
IE.9. —Least square coefficients for equation EI.ll for the Coastal Plain/Pied-
          mont 	 IE.52
111.10.—A  comparison  (cm)  of the evapotranspiration method  and  the least
          squares  method  to measured values for the three watershed
          examples	 IE.52
IE. 11.—Digitized excess water distribution for the Rocky Mountain/Inland Inter-
          mountain hydrologic province (4), low energy aspects	 IE. 107
IE.12.—Digitized excess water distribution for the Rocky Mountain/Inland Inter-
          mountain hydrologic province (4), intermediate energy aspects	 El. 107
El. 13.—Digitized excess water distribution for the Rocky Mountain/Inland Inter-
          mountain hydrologic province (4), high energy aspects 	 El. 108
El.14.—Digitized  excess  water distribution  for the  Continental/Maritime
          hydrologic province (6), low energy aspects	 HI.Ill
El. 15.—Digitized  excess  water distribution  for the  Continental/Maritime
          hydrologic province (6), intermediate energy aspects	 El.Ill
El. 16.—Digitized  excess  water distribution  for the  Continental/Maritime
          hydrologic province (6), high energy aspects	 El. 112
EI.17.—Digitized excess  water  distribution  for the  Central Sierra hydrologic
          province (7), low energy  aspects	 El. 112
IE.18.—Digitized excess  water  distribution  for the  Central Sierra hydrologic
          province (7), intermediate energy aspects	 El.113
III. 19.—Digitized excess  water  distribution  for the  Central Sierra hydrologic
          province (7), high  energy aspects	 EI.113
EI.20.—Digitized  excess  water distribution  for the  Northwest hydrologic
          province (5), low energy  aspects	 El. 118
                                        m.xii

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                                                                            Page

III.21.—Digitized  excess  water  distribution for the  Northwest hydrologic
          province (5), intermediate aspects	 m.118
ni.22.—Digitized  excess  water  distribution for the  Northwest hydrologic
          province (5), high energy aspects	 HI.119
IE.23.—Soil moisture adjustment coefficients for the Rocky Mountain/Inland
          Intermountain hydrologic region (4) by aspect/elevation and season  HI. 128
in.24.—Soil moisture  adjustment  coefficients for the Continental/Maritime
          hydrologic province (6) by aspect/elevation and season	 HI. 131
HI.25.—Soil moisture adjustment coefficients for  the Central Sierra hydrologic
          province (7)  by aspect/elevation and season	 HI. 131
in.26.—Soil moisture  adjustment  coefficients for the Northwest hydrologic
          province (5)  by aspect/elevation and season	 HI. 135
in.A.I.—Summary of  equations  for quantifying snow accumulation in large
           clearcuts (D >  15H) 	 ffl.149
ni.C.l.—Mean annual water balances (in.) for typical subalpine watersheds in
           the Rocky Mountain/Inland  Intermountain region  	 HI. 159
III.C.2.—Geographic description of the  drainage basin,  Wolf Creek watershed,
           Colorado	 HI.161
III.C.3.—Streamflow data (1969-1973) on a monthly residual volume basis, ad-
           justed to account for diversions from Wolf Creek	 III. 162
m.C.4.—UCSL substation description	 HI.162
m.C.5.—UCSL calibration and validation	 HI.163
III.C.6.—CSSL substation description	 HI.165
ffl.C.7.—CSSL calibration and validation	 HI.165
ffl.C.8.—WBSL substation description	 HI.167
III.C.9.—WBSL calibration and validation  	 ffl.167
ni.D.l.—Calibration and validation summary for sites modeled by PROSPER  HI. 170
                                       IH.xiii

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                           LIST OF WORKSHEETS
Number                                                                    Page
III. 1.—Water available  for streamflow  for the  existing condition  in  rainfall
        dominated regions. (Needle Branch)	  El.36
m.2.—Water available  for streamflow for the  proposed condition  in  rainfall
        dominated regions. (Needle Branch)	  III.37
III.l.—Water available  for streamflow  for the  existing condition  in  rainfall
        dominated regions. (Coweeta)	  III.39
III.2.—Water available  for streamflow for the  proposed condition  in  rainfall
        dominated regions. (Coweeta)	  III.40
III.l.—Water available  for streamflow  for the  existing condition  in  rainfall
        dominated regions. (Grant) 	III.42
III.2.—Water available  for streamflow for the  proposed condition  in  rainfall
        dominated regions. (Grant) 	III.43
in.3.—Flow duration curve for existing condition, rain dominated region. (Nee-
        dle Branch)  	111.53
in.4.—Flow duration curve for proposed condition, rain dominated regions — an-
        nual hydrograph unavailable. (Needle  Branch) 	  III.54
III.3.—Flow duration curve  for  existing condition,  rain  dominated  region.
        (Coweeta)	  111.55
in.4.—Flow duration curve for proposed condition, rain dominated regions — an-
        nual hydrograph unavailable. (Coweeta) 	  III.56
ffl.3.—Flow duration curve  for  existing condition,  rain  dominated  region.
        (Grant)  	  m.57
m.4.—Flow duration curve for proposed condition, rain dominated regions — an-
        nual hydrograph unavailable. (Grant)  	  HI.58
III.5.—Water available  for streamflow  for the  existing  condition in  snow
        dominated regions, (example)	  HI.68
HI.6.—Water available  for  streamflow  for  the proposed  condition in  snow
        dominated regions, (example)	  Ill 72
ni.7.—Existing condition hydrograph for snow dominated regions, (example) .  in.100
III.8.—Proposed condition hydrograph for snow dominated  regions,  (example)  ffl.102
                                    IH.xiv

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                                      INTRODUCTION
  The objective of the hydrology chapter is to pre-
sent a methodology which will help to predict the
potential impacts of silvicultural activities on the
hydrologic  cycle, or at  least those components
which most significantly affect  non-point source
pollution. The state-of-the-art in hydrology is such
that a methodology cannot be presented in a hand-
book without falling short in terms of both process
definition and  predictive capabilities.   The
methodology   presented  was formulated using
relationships  developed from simulations using ex-
isting hydrologic models. The data bases used  in
the simulations were from representative  and ex-
perimental watersheds and  the  relationships ex-
trapolated  for regional  applications.  Because  of
weaknesses of the state-of-the-art in modeling and
in the limited number of data bases, many assump-
tions had  to be   made which weaken  the
methodology if misinterpreted. Correct application
of the methodology is not a simple matter of "plug-
ging in numbers and turning  the crank." Because
hydrology plays  a role in virtually all aspects  of
non-point source pollution, the  procedure should
be carefully applied only by qualified individuals.
  For this reason, an "Overview of the Hydrologic
Cycle" is presented first. It describes the salient
hydrologic  processes  in  stream and storm  flow
generation  that can be impacted by management
and which  have the most significant potential for
influencing  non-point  source  pollution. Another
section, "The Impact of Silvicultural Activities on
the Hydrologic Cycle," is also included to present a
subjective means of evaluating the potential im-
pacts that silvicultural activities can have on those
key processes or components. It is believed that the
qualitative sections will be useful to the technically
oriented  user  of the  handbook and enable the
necessary assumptions and interpretations to be
made regarding  the methodology as it applies  to
the specific  application. It has been found, for ex-
ample, that presenting the various procedures for
routing the  components  of streamflow — surface
runoff, subsurface  flow, and ground water — was
not possible in a handbook given the state-of-the-
art; yet the overview may help the user to make the
right decision concerning the potential occurrence
of and impact on each component.

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                          DISCUSSION: OVERVIEW OF  THE
                                  HYDROLOGIC CYCLE
  The water balance. — The hydrologic cycle can
be  discussed  in terms of the  disposition  of
precipitation as expressed by the water balance:
              P =R0 + Et+AS
(in.i)
where:
  Pg  =  Gross precipitation during a time interval
         t,
  R0  =  Streamflow or total water yield during a
         time interval t,
  Et  =  Evapotranspiration  or  precipitation
         which is vaporized and returned to the
         atmosphere by evaporation from the land
         and vegetal surfaces or transpired by the
         vegetation during a time interval t, and
  AS  =  Change  in storage or  that  portion of
         precipitation which is  retained or lost
         from storage in the earth's mantle during
         the time interval t. The change in storage
         approaches zero as the  time interval (t)
         increases.

   Silvicultural activities have virtually no effect on
 the amount of precipitation entering  the  system
 but can  influence the disposition of that  rain or
 snowfall  in both time and space on a small or local
 scale. It is by altering the components of the above
 water balance through alteration of the processes
 involved that man has the opportunity to influence
 the hydrologic regime.
   Energy and precipitation.  — The  hydrologic
 cycle has two  inputs:  energy and  precipitation.
 Energy controls both the form of precipitation as it
 enters the system (whether rain or snow) and dis-
 position  of the precipitation within the system.
 Figure III.l  presents the hydrologic  cycle as  a
 system of water storage compartments  and depicts
 the relative transfer of liquid, gaseous,  or solid
 water to  the various components of the budget (Pg,
 Ro, Et, and AS).
   Precipitation falls in the liquid or solid phase or
 in combinations of both. Chow (1964) gives more
 detailed  information on  precipitation  forms but
 three are assumed to be  of significant interest to
 the forest hydrologist —  rainfall, snowfall, and  a
 combination of rain  and snow.
  Distinguishing  between  rain and snow.  —
Distinguishing between rain and snow (whether or
not precipitation falls as water droplets or ice
crystals)  depends  on complex  thermodynamic
processes. Obviously,  when  air temperatures are
warm, it rains; when they are cold, snow falls. One
method which appears to give a reasonable dif-
ferentiation between rain and snow (or combina-
tions thereof) can be illustrated by the following:

               Pf=(l-B/A)            (III.2)
where:
  Pf  =  The form of  precipitation; rain, snow, or
         a mix (if Pf  > 1 then precipitation form
         = snow, if Pf < 0 then precipitation form
        = rain,  if 0 > Pf < 1 then precipitation
         form = mix  of rain and snow),
  B   =  Difference  between  the  maximum
         temperature  (Tmax),  during some inter-
         val of time, and the temperature at which
         snow falls,
  A   =  Difference between the maximum (Tmax)
         and minimum (Tm;n) temperatures dur-
         ing the same interval of time.
and where:
  T   =  Threshold temperature or temperature at
         which snow falls,
  Tmax=  Maximum temperature  during time in-
         terval, and
  Tmin =  Minimum temperature during time in-
         terval.
  If used with some judgment, equation  III. 2
should enable the user to make a reasonable dif-
ferentiation between whether the storm event was
rain or snow.
  Evaluating snowmelt. — In the United States,
snowmelt processes have been the subject of much
study since the late 1930's.
  Thermal indices provide reasonable estimates of
melt  when  the objective  is  merely  to  predict
snowmelt, the simplest being the air temperature
method (U.S. Army 1960). However, thermal  in-
dices are not adequate for evaluating the snowmelt
process because they  do not adequately  consider
the  complex  energy  exchanges that take place
between  the  forest cover and snow environment.
Chow (1964) treats the subject of snowmelt in some
                                               III. 2

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                  WATER STORAGE IN ATMOSPHERE
      OUTPUT
      (Gaseous)
                  INPUT
    Evapotranspiration

           1    %
           Evaporation
                  (Interception)
                     Loss
 Transpiration
               Rain, Snow,
               Condensation
                       NTERCEPTION
                         STORAGE
                          (On plants)
   Stemflow,
  Canopy-drip
Wind-blown Snow
                                         Throughfall
                          SURFACE STORAGE
                                 (On soil)
                                        Infiltration
                         SOIL-WATER STORAGE
                             (Above water table)
                            GROUNDWATER
                                STORAGE
                             (Below water table)
                           Seepage
                                        Seepage
                                 OUTPUT
                                  (Liquid)
                              Total Water Yield
Figure 111.1—The hydrologic cycle consists of a system of water storage compartments and the solid, liquid,
   or gaseous flows of water within and between the storage points (Anderson and others 1976).
                                  III.3

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detail.  A  comprehensive  analysis  of  several
watershed and snowmelt models will also be found
in Sohn and others (1976)  and Jones  and Leaf
(1975).
  A  practical  quantification of  the  snowmelt
process  requires   compromise.  For  example,
research has shown that solar radiation is the prin-
ciple cause of snowmelt. There may be exceptions
in those areas  where large  sources and sinks  of
energy  are involved  in  the  sensible  (convec-
tion/advection)  and latent  (evaporation/conden-
sation)  heat exchange processes. However, ade-
quate determination of these exchange processes
requires more data  and sophisticated analytical
tools than are normally available. Accordingly, the
best approach is to:  (1) consider the energy balance
from incoming  solar  radiation  and temperature,
and (2)  modify this  balance to account for sensible
and  latent  heat exchange in those  areas where
these  processes  significantly  affect  snowmelt.
While  solar radiation is  the  principal cause  of
runoff from snowmelt, in some parts of the United
States (the Pacific Coast,  for example) runoff can
occur from combinations  of both snowmelt and
rainfall.  Such  rain on  snow events can  be
catastrophic, causing severe  erosion and  mass
movement. These are the largest streamflow events
and occur in winter during wet mantle conditions.
Thus, as discussed subsequently in this handbook,
the runoff potential  from both forest  and open
areas is similar.
    DISPOSITION OF PRECIPITATION
  As precipitation falls to earth, it can strike any
one of several surfaces including foliage and stems
of the vegetative cover, litter or organic debris on
the soil surface, mineral soil, or open water such as
streams,  rivers, ponds, and lakes.
  Channel precipitation. — Precipitation falling
on the open water (channel system) immediately
becomes  streamflow  and all further losses are
beyond the scope of this handbook. Little that man
does or can do in silvicultural activities has any ef-
fect on the channel precipitation component other
than to increase it, either by reducing interception
losses or increasing the amount of live  channel.
Normally  channel  precipitation  represents  a
variable,  but  small, percentage  of the  total
precipitation.
    Effect Of The Canopy On Water Losses

  For precipitation falling on the land mass, the
first opportunity for loss occurs from that which
strikes and is intercepted by the vegetative canopy.
Water which wets or sticks to the canopy is either
retained and evaporated back to the atmosphere,
or detained and allowed to drop to the forest floor,
or  redeposited  elsewhere  (as  in  the  case for
windblown snow). A  small  percentage of  the in-
tercepted water runs  down the branches and tree
bole as stemflow and enters the soil.
  That portion of water evaporated back from the
canopy is of the most concern, as it represents a loss
from the system ("interception loss") as part of the
evapotranspirational process.  Several factors in-
fluence the magnitude of interception  losses —
crown density; species; season; latitude; and storm
frequency, size, intensity and duration. Generally,
it can  be noted that conifers intercept more than
hardwoods, and a greater percentage of precipita-
tion in small volume storms is intercepted than in
large volume storms (Helvey 1971a, Douglass and
Swank 1975). In general, interception loss increases
with  increases  in  the foliage  surface  and  the
number of storms, and it decreases with increasing
storm size and duration.
  Several equations are available which  can be
used to estimate interception losses. These have
been summarized by Helvey  (1971a) for various
tree species. The summary represents equations for
individual events; and little difference was noted in
seasonal interception losses for coniferous species,
while deciduous species  varied significantly by
season.
  Rainfall  regimes.  —  Interception  averages
about  10 percent of the  precipitation falling on
deciduous forest stands in the summer and about 5
percent during leafless periods. On the other hand,
fully stocked conifers intercept  15 to 20 percent in
the summer and only slightly less in the winter. As-
suming uniform rainfall, seasonal differences in in-
terception losses in conifers are mostly a function of
available energy. Conifers may annually  intercept
4 to 6 inches more water than hardwoods under
identical  precipitation conditions (Douglass and
Swank 1975). This observation is a generality for
rainfall regimes and, as will be shown, is a function
of the  amount and seasonal distribution of both
precipitation and energy. Under snow dominant
regimes the process is similar, but the relative ef-
fect of interception may  vary.
                                               m.4

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  Snowfall regimes. —  In  some predominantly
snowfall regimes,  the  snow may  rest on tree
canopies only during periods of cloudy weather, low
temperatures and frequent snowfall. For example,
in the Rocky Mountain region wind generated vor-
tices and eddies  quickly strip the snow from the
trees.  In a  short  time  this  airborne snow is
redeposited at varying distances from where it was
initially retained  on the canopy (Hoover and Leaf
1967) and  little loss occurs.  In other  geographic
areas, redistribution may  not be as dominant and
thus may have a lesser effect on the seasonal snow-
pack. However large or small the  impact of snow
redistribution, the potential should be evaluated in
all  regimes  (Anderson and others   1976).
Significance of the redistribution phenomenon is il-
lustrated in figure ni.2, a time-lapse sequence of a

typical snowfall event  in  central  Colorado.  In
regions where snow interception loss is significant,
one general equation for estimating the loss on con-
iferous trees has been proposed by Satterlund and
Haupt (1967).

  Whether in the form of rain or snow, interception
losses occur from the gross precipitation (Pg) with
the remainder (Pnet) passing through to the forest
floor. Precipitation (Pnet) in  the form of snow is
delivered below the canopy and accumulates until
it melts; precipitation (Pnet) in the form of rainfall
occurs as  either stemflow, throughfall, or direct
precipitation,  which later has an opportunity for
further loss by litter interception. Water from the
melting snowpack  is subject to litter interception
much the  same as rainfall.
                                                      B
                                                    A This photograph was  taken during moderate
                                                    snowfall that continued throughout the day of Feb-
                                                    ruary 4, 1970, at the Fraser Experimental Forest.
                                                    The storm ceased during the night.
                                                    B The  most exposed trees were already bare of
                                                    snow by noon on February 5, 1970. Individual vor-
                                                    texes look  like  artillery bursts on the mountain-
                                                    sides.  Vortexes were moving rapidly eastward
                                                    (from right to left), and each one was visible for less
                                                    than 60 seconds.
                                                    C By 4:00 p.m. on  February 5, 1970, all snow was
                                                    gone from exposed tree crowns. The white patches
                                                    are snow in the clearcut blocks on the upper portion
                                                    of the Fool  Creek watershed.
                          Figure III.2—Significance of wind-caused snow redistribution
                                         In the subalpine zone.
                                               rn.s

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          Effects Of Litter Cover On
         Disposition  Of Precipitation
  Litter  interception  loss  is  precipitation  in-
tercepted or detained  by the litter on the forest
floor and eventually evaporated back to the at-
mosphere without infiltrating the mineral soil. It
ranges from 2 to 20 percent of the gross precipita-
tion (Helvey 1971) and, like canopy interception, is
strongly related to storm frequency and size. Litter
interception loss normally averages only a few per-
cent and represents a  much smaller loss than
canopy interception under fully  forested  condi-
tions.
  Benefits of the litter cover far exceed the cost in
terms  of water loss. Litter provides a protective
cover which absorbs the energy of rainfall impact
and prevents detachment of surface soil particles.
It is far  more significant in this respect than the
vegetative canopy itself. The degree to which cover
is effective  in reducing rainfall impact energy at
the soil surface is a function of where it is located
with respect to mineral soil. Approximately 80 to 90
percent of the gross precipitation  (Pg) reaches the
mineral  soil,  and the closer  the  cover is  to  the
mineral soil, the more  effective it can be in reduc-
ing rainfall  impact.
    MOVEMENT OF WATER INTO THE
           SOIL WATER COMPLEX
             Infiltration Of Water
  In most  undisturbed forests in humid and sub-
humid climates, rainfall and snowmelt usually in-
filtrate. (This  is a general observation although
there are exceptions.)  In our  general process con-
siderations, we assume that all precipitation,  ex-
cept the interception losses or otherwise detained
and  evaporated water, infiltrates the soil mantle
and  at least temporarily becomes part of the soil-
water complex. The limiting factor in infiltration of
water into undisturbed soils is generally not the in-
filtration rate; this usually  far exceeds  normal
precipitation intensities.  Failure to infiltrate un-
disturbed soil is more often associated with a lack
of soil-water storage capacity — there is no place
for the  water to go. There are regions and sites
where a combination  of storm size,  frequency of
event, and/or soil characteristics causes a failure in
infiltration, but this is not the general case.
Factors Affecting Infiltration Rates
— A Summary

  Although infiltration characteristics  of mineral
soil  are a function of several factors, the primary
one  is pore size  distribution in  the  surface layer.
The larger  the pores,  the greater the infiltration
rate. Pore size distribution, in turn, is controlled
by:
  1. Texture. The parent material and its weather-
     ing. These determine the soil particle size or
     the proportion of sand, silt, and clay. Textural
     characteristics influence infiltration rates to
     some degree because sands have larger pores
     than do clay soils. Texture is independent of
     vegetation and, although it influences infiltra-
     tion, it usually is not  altered  by  man's ac-
     tivities.
  2.  Soil  structure.  The aggregates  and
     macropores  result from incorporated organic
     matter and tree-root and organism activity.
     Vegetation,  directly and indirectly, is  very
     significant  in  developing   good  structural
     characteristics and in  maintaining high in-
     filtration  rates.
  3.  Soil moisture level. At  the start of the event
     the antecedent soil water levels also influence
     infiltration since the drier the soil, the greater
     the initial rate,  and the greater  the capacity
     for storage.
  Most forest soils are developed under  conditions
of adequate rainfall  and profile development, at
least at  the surface (organic and  mineral soil),
which is adequate to insure an extremely high in-
filtration  rate  assuming   storage   capacity  is
available.
  It  should be noted that all factors which can
greatly reduce the baseline infiltration are in-
fluenced either by the degree to which the surface
organic layer and mineral are soil disturbed or in-
capacitated (such as by frost &r mechanical means)
or the degree to which storage capacity is reduced.


Evaluation Of Infiltration And Role Of The
Soil Profile

  Several  factors  need  to  be  considered  in
evaluating  the  infiltration  characteristics of  a
watershed  or  site.  First, precipitation is not dis-
tributed uniformly over time so that the basin can
recover or  adjust to  irratic pulses of intense
precipitation.   By  the  same  token,  antecedent
                                                m.6

-------
moisture contents and  infiltration rates  are  not
spacially or temporally uniform, so that conditions
which exist at one point may differ at another point
and they can be compensating.
  The infiltration  process is a  function of the
physical and hydrologic state of the entire  soil
profile on which the precipitation (or melt water) is
falling  and, as  suggested,  is  not  necessarily
restricted to a finitely thin surface layer. Assuming
the surface  layer is not saturated, the water in-
filtrates  the surface  and  percolates  vertically
through the profile at a rate controlled by  the con-
ductivity of successively deeper soil horizons as the
wetting front goes deeper. Assuming the rate of in-
filtration does not exceed the permeability of the
deeper horizons,  the water will tend  to pass ver-
tically. In many situations the deeper layers pre-
sent a temporary restriction  or impedance to the
vertical  movement of water  when infiltration or
percolation  into the horizon  exceeds the vertical
rate of translation through it. Under  these condi-
tions, water is detained in the overlying layers and
occupies available storage.
  Depending upon input (rainfall or snowmelt) in-
tensity and volume, and upon antecedent moisture
conditions, saturation may occur in intermediate
or even  surface soil  horizons. Once  the rate at
which water enters a horizon exceeds the rate at
which water can  leave the horizon vertically, the
opportunity for lateral  downslope movement in-
creases.  This applies whether the impedance or
restriction to vertical movement is an underlying
soil layer with restricting permeability or bedrock.
Rainfall (rain, meltwater, or a combination) inten-
sity has a significant effect on  where lateral flow oc-
curs in the mantle.  Under  low  intensity input,
bedrock may be the impeding layer; under more in-
tense input, an overlying horizon may become the
restrictive layer and become the impedance to ver-
tical movement.
  The rate at which  water can move or be
translated in the  soil mantle is a  function of the
conductivity of the soil. The conductivity (K) is in
turn a function of the soil moisture  content  (9)
and,  generally, the conductivity  (K)  has been
shown to decrease exponentially  with decreasing
soil moisture content (0).  Depending on  antece-
dent moisture conditions, any horizon (especially
those removed  from the surface)  may act as an
impeding layer simply as a result of their low initial
moisture content. This  is  more significantly  as-
sociated with clay soils or soils with poor structural
development.
  The above discussion primarily describes the role
the soil profile plays in infiltration; however, it also
qualitatively  establishes  the conditions  under
which perched water tables are formed and rapid
subsurface stormflow generated. Soil water move-
ment in nonstorm periods is somewhat similar ex-
cept that soil matric potential plays a more signifi-
cant role and the time frame for movement is much
longer. The discussion is valid everywhere and  is
primarily  dependent  on  whether the  profile
described is several to many feet deep or only a few
inches thick. In most forest situations, the surface
organic layer and  the surface mineral soil horizon
are well developed both texturally and structurally
and thus have  adequate storage capacity. These
layers then act  as a buffer, absorbing the rainfall
and either temporarily storing it or  allowing it to
pass on to other lateral or vertical positions. In this
respect, mantle  storage tends to dampen the effect
of input intensity, thus allowing the  system to dis-
sipate the  water internally. The two most signifi-
cant factors in this process, then, are  the size of the
event and available storage capacity; when size ex-
ceeds capacity,  failure to infiltrate occurs.

  There are some sections of the country, and local
sites everywhere, in which profile development and
organic accumulations are inadequate for the infre-
quent  but  highly intense rainfall events,  causing
infiltration failure. By the same token, the  effect of
lateral downslope migration of water or lateral sub-
surface water movement can cause lower slope
positions to fail  more frequently than upper slope
positions because  of higher antecedent moisture
conditions. Soil  mantle constrictions or rock out-
crops,  soil  freezing, and mechanical disturbance
also alter this dynamic and variable process.
    Dissipation Of Water In The Soil Water
                    Complex

  Water which infiltrates becomes, at least tem-
 porarily, part of the soil water storage. Depending
 on  the hydraulic gradient or driving force  in the
 soil, water may (1) be held in place, (2) follow the
 dominant gradient and percolate vertically  or,  (3)
 move laterally toward the stream channel. Further,
 water may be lost as part of the soil water complex
 through  evaporation from the  soil surface, deep
 seepage to ground water, quick flow to a stream, or
 absorption rby vegetation roots and  then  tran-
 spirational loss to the atmosphere.
                                                m.7

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Transpirational Depletion Of Soil Water

  The rate at which plants use water is a function
of the amount of water and energy available to con-
vert water to vapor (reflected by index parameters
such as air temperature, solar radiation, wind, and
vapor  pressure  deficits). Generally,  during  the
growing season transpiration  occurs at the max-
imum rate  until water  becomes limiting to  the
plant, at which time transpiration rate decreases;
or, given the available energy, a fully stocked stand
of vegetation will transpire  at the maximum rate
for the energy available as long as water to do so is
not limiting. The actual function for any particular
stand  or  site varies  depending  on  soil
characteristics, stand or cover density, species, and
available energy and water.  Silvicultural activities
that  reduce  the canopy, change the plant-soil-
water interaction.
  Small watershed studies  (Anderson and others
1976) have  been effective in defining the water
balance and its changes due to silvicultural ac-
tivities. These studies have shown that a signifi-
cant but varying amount is absorbed by,  and lost
through, the vegetation;  the remainder (assuming
no change in storage over the long run) appears as
streamflow with  a small but varying amount lost as
either deep seepage or  water that  bypasses  the
stream gaging site.
                         Soil Moisture Regimes

                           Generally, soil water levels are highest during the
                         dormant season or following  seasonal  snowmelt;
                         levels are lowest during the mid to late growing
                         season when accumulated transpirational drain is
                         the greatest. This varies  as a  function of the
                         precipitation regime,  soil physical properties and
                         depth, geology, position on slope, aspect, and the
                         vegetation complex.

                           One example of a soil moisture distribution for a
                         humid region with deciduous forest cover, uniform
                         rainfall throughout the  year, and moderate soil
                         depth is shown in figure III.3. In this case, soil
                         moisture recharge (see fig.  III.3) begins sometime
                         during  the fall  when precipitation exceeds
                         evapotranspirational demand, thus resulting in a
                         surplus  of water.  This  surplus, in part, goes to
                         storage  and  the  balance  results  in higher
                         streamflow levels. During the period  of recharge,
                         storage potential decreases, streamflow base levels
                         increase, and the basin is potentially more respon-
                         sive to individual storm events in terms  of produc-
                         ing stormflow (not shown). During periods of max-
                         imum soil moisture deficiencies, basin response, in
                         terms of percentage of precipitation  returned as
                         stormflow,  may  be  low with  the  majority of
                         precipitation stored in the soil mantle. On the same
     Lu
    Q. U-
    Oil
    oc 5
    O
    CO
           High
           Low
                                                                                  Soil Moisture
                                                             ET
                     T~
                      F
-T-
 M
T
 A
M
T
 J
                                                      J

                                                    TIME
T
 A
~T
 S
                                               O
                                               N
T~
 D
        Figure 111.3.—The relationship between streamflow, soil moisture, and evaporative demand in a deciduous
                                    forest in a humid environment.
                                                III.8

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basin, the response can be high during wet antece-
dent  conditions  (Hewlett,  Cunningham,  and
Troendle  1977),  when less storage  capacity is
available.
  In humid regions such as  the Pacific Northwest,
non-point source pollution problems  can be  most
critical when soil moisture  storage capacity is
minimal due to basin recharge. During this period
the evapotranspiration processes have  little in-
fluence on the quantity of water delivered to the
stream and the  runoff potential  is  equally high
from both forested and open areas. In such cases,
the stormflow analysis procedures discussed subse-
quently in this handbook are needed to evaluate
silviculture's impact on  water  quality.  The
proposed  methodology focuses on evaluating im-
pacts  on  the hydrologic cycle from  forest cover
changes. This is not to say that other activities can-
not  have a  significant   effect in modifying
hydrologic  responses  (road  design,  drainage,
yarding, etc.) particularly  during storm events.
The user is encouraged to first consider the impacts
from  forest cover changes since  modifications in
antecedent conditions (soil moisture regime)  must
be known before  making an  adequate stormflow
analysis.
  The pattern expressed in  figure HI.3 varies with
(1) soil depth and soil water storage  capacity, (2)
seasonal distribution and form of precipitation, (3)
latitude (energy input), (4) vegetative cover, and
(5) other  factors. Consequently,  this  figure is
representative only  to illustrate  the  changing
relationship of input, output, and storage.
  Figure III.3 signifies the basic relation between
precipitation  and its  disposition  as streamflow,
evapotranspiration,   and   soil  water  storage.
Whenever storage  capacity  (or  soil  moisture
deficit) is great  or evapotranspirational  potential
high,   streamflow can be  expected  to be  low,
although response to individual storms can be high.
Streamflow and response to net precipitation will
always be high when storage capacity is  low  or 0.
Streamflow Generating Processes

  Interacting  with the factors listed  above is the
relative role of various flow generating components
of surface, subsurface,  and ground water flow. The
pathway that water takes to  the stream channel
controls its  availability to  be stored, to be used,
and to carry pollutants.
  As noted in  the discussion on infiltration, we as-
sume  that almost all  precipitation that is not in-
tercepted infiltrates the soil mantle. This  is a basic
and significant assumption, since water which does
not  infiltrate has no  opportunity for  internal
chemical exchange. By  the same token, little op-
portunity is available to filter sediments and other
pollutants  from surface water  if it  has not in-
filtrated.  Whenever  man's  activities  alter  the
pathway water takes to the channel, the potential
effect in changing water quality may be great. In
effect,  subsurface flow  processes dominate  the
system  and  open water on the  soil  surface is
observed only when the ability of the  subsurface
system to accept that water has been overridden.
Furthermore, locally observed open water on the
surface does not  always  leave the basin as overland
flow. It  must move all the way to the channel via
the surface to be defined as true surface runoff or
overland flow.

  Describing subsurface water  movement is ex-
ceedingly difficult because, like infiltration,  it is
such a complex  process. We can assume, however,
that gravity is the major driving force, and we can
visualize the steady  movement of soil water from
the ridge to the stream (see fig. in.4).  The max-
imum amount of water available at the ridge site in
the  ideal system is  assumed to be  limited to
precipitation input, but at  successive points
downslope, the amount of water available exceeds
local precipitation input by the amount draining
from positions upslope.
  As water migrates laterally downslope, it has the
opportunity at  any  point to remain in place as
storage,  to migrate  further,  to be  lost  in  the
evapotranspirational  process,  or to  percolate
deeper as seepage to ground water.
  Total available energy and water vary with posi-
tion on slope,  and,  as a result,  the  various
relationships presented  in figure in.3 can be quite
varied within the system. It has been shown that
soil moisture can vary with season, aspect, crown
density, position on slope, and soil physical proper-
ties, as  well as  with antecedent rainfall  (Zahner
1967, Kochenderfer and Troendle 1971, Helvey and
others 1972).
  At any point in time,  soil water storage potential
per unit depth may be greater at the ridge than at
channel positions. During a storm event or during
active snowmelt periods, the lower slope positions
(because of higher antecedent moisture and  less
available storage) which yield higher conductivities
are  more  responsive  and more  influential in
streamflow production;  that is, streamflow and its
solutes are  most responsive to conditions that exist
                                               in.9

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                                                         Rainfall
                                                                                    New Ram
                                                                                    Last Rain
Channel Expansion
When the subsurface I
flow of water exceeds
the capacity of the soil
profile to transmit it,
channel length will
grow
                                                                  '   „ New Rain
                                             New Rain
                                             Last Rain
                   Saturated Zone
           Direct Runoff
        Figure 111.4.—Downslope movement of water on a forested upland watershed. This illustrates the variable
                source areas responsible for direct runoff and baseflow (Hewlett and Hibbert 1967).
at lower slope positions because these positions
serve as a  direct source and drain to the  channel
system.
  The significance of this process is demonstrated
for a watershed  condition in figure III.5. At the
start of the storm (or at any other time), the surface
channel system needed to drain lower slope posi-
tions and headwater hollows exists at some level
which is sufficient to drain the open water in the
system. As the event (or time) proceeds, the lower
slope positions, which quickly begin to yield water,
and the channel  system expands to drain  this ad-
ditional free water flowing from the saturated soil
horizon. This continues through the rainfall event.
Following the  event,  the source  area recedes to
something  approaching the pre-event condition.
This reflects the dynamic and variable nature of
streamflow generating  source areas and includes
both storm and nonstorm periods.
                              Factors Affecting Individual Storm Response

                                Nature is  never as uniform as idealized in the
                              two preceding figures. First of all, soil mantles are
                              seldom as uniformly distributed  as depicted  in
                              figure III.4; there are depressions, outcrops, ridges,
                              and swales.  At the same  time, soils  vary both  in
                              physical properties and depth. As a result, storage
                              capacity and moisture content are quite  variable.
                              Figures III.4 and III.5, however, contain the rudi-
                              ments of the  process: (1) water infiltrates;  (2) water
                              moves laterally downslope and concentrates; (3)
                              when the capacity (saturation point) of the soil is
                              exceeded,  water exfiltrates;  and  (4) the process
                              varies with  slope  length,  soil depth,  antecedent
                              moisture conditions, and  size of storm.
                                In the case of a rock outcrop or soil constriction
                              at midslope,  the downslope migration of subsurface
                              water is  impeded  by the restricted  soil depth.
                                                IH.10

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         Figure III.5.—A lime-lapse view of a basin showing expansion of the source area and the channel system
                                during a storm (Hewlett and Troendle 1975).
Water storage capacity is decreased, and  satura-
tion may occur quickly. There is no place for sub-
surface water  to  go so it surfaces and  travels
overland in a draw or rill to the channel, becoming
part of it. Similarly, wet weather seeps  can be
caused by contacts between  soils of differing
physical properties. Man-caused  interruptions,
such as roads, can act in the  same manner.

  The variability  of soil moisture is  such that
stormflow  sources  in one storm may not  be the
same as those in the next. Systems not overloaded
under small storms or dry conditions may become
overloaded  under larger storms or wet conditions.
Seeps may  occur as (1) sheet flow from either a con-
tinuous constriction  or outcrop along a contour or
(2) as a spring from a constriction in a swale where
subsurface  flow has concentrated.
  Every basin has its own signature in this respect.
Each must be interpreted individually. Water sur-
faced in this manner flows toward the channel. If
conditions permit,   it will  reinfiltrate.  In other
cases, it may flow to the channel and become an ex-
tension of the channel system. Any precipitation
falling directly on this channel extension is, in  ef-
fect, channel precipitation.
  Streamflow from both rainfall  and snowmelt is
generated primarily  in this manner. The objective
of this discourse is to dispel the idea that stormflow
from undisturbed basins is generated as "precipita-
tion excess" or water failing to infiltrate and flow-
ing toward the channel as overland flow. Overland
flow resulting  from  failure  to infiltrate can
dominate the hydrograph,  but the likelihood is
restricted to minor portions of the country, specific
sites, or extreme  rainfall events.
                                               in.ii

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      DISCUSSION: IMPACT OF  SILVICULTURAL ACTIVITIES ON THE
                                   HYDROLOGIC CYCLE
  Hibbert (1967) first summarized the results of 39
experiments conducted at various  places around
the world on the  effect of altering forest cover on
water  yield.  Since  that  date there  have been
numerous  other  studies  (Anderson  and  others
1976). Cutting the  forest reduces  evapotran-
spirational  demand,  alters  the  soil moisture
regime, and results in increased streamflow. While
it is not a purpose of this handbook to review the
literature, the following table summarizes some of
the  observed  responses to  forest  cover removal
which have been observed in United States. Table
in.l was  reproduced from  Anderson  and others
(1976). This  reference  provides a comprehensive
review of the literature on impacts from forest cut-
ting.
  The objective of this section is to describe  the
process changes occurring in the hydrologic cycle
that are  responsible for the water  yield changes
                                          summarized in Table III.l. The indicated response
                                          results from process  modification. Depending on
                                          the region, the impact on the various processes dif-
                                          fered.

                                             The  removal  of vegetation  increases the  net
                                          precipitation  and possibly its distribution by both
                                          reducing the amount of interception storage and, in
                                          some cases, causing the redistribution of snow. The
                                          infiltration characteristics  of  the experimental
                                          watersheds more than likely were not significantly
                                          altered. The most significant direct response to the
                                          various silvicultural activities summarized in table
                                          ni.l was the reduction in transpiration associated
                                          with  eliminating vegetation. This is  reflected in
                                          higher soil moisture levels, which contribute to
                                          both higher base flow levels and/or wetter antece-
                                          dent conditions, and possibly resulting in greater
                                          direct runoff or quick flow during storm  events.
                Table III.1.—Increases in water yield following forest cutting, by forest type,
                  geographic location, and type of cutting (Anderson and others 1976)
                                   Percent
               Mean               of area
Forest  Mean   annual   Silvicultural  of basal
 area  precip- stream-    activity    area(b)
(acres)  Station   flow                removed Regrowth 1
                                          Water yield increases by years after silvicultural activity:
  39
  59
  85
  59
  38
  90
  85
        --- Inches —
                                                  •Inches	    	Percent-
48
57
60
57
59
58
59
                                   (1) Mixed Hardwoods, Western North Carolina
40
33
23
85
70
212
71
50
22
72
75
71
81
79
73
80
77
72
31
30
24
50
48
42
51
41
33
Clearcut
Clearcut
Clearcut
Clearcut
Selection cut
Selection cut
Selection cut
Selection cut
Riparian cut
100
100
100
50
22 b
30b
35 b
27b
12
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
14.4 10.9 10.9 9.8
16.8 13.0 11.7 11.4
5.0 3.7 2.3 4.4
7.8 6.1 5.1 4.4
3.9 2.2 2.8 1.1
Averaged 0.98 per year
Averaged 2.17 per year
Nonsignificant
Nonsignificant
7.
11,
3,
3,
1.




,9
,2
,1
.9
.5




66
65
—
—
6




                                                                                 46   29   26   31
                  (2) Northern Hardwoods, Central New Hampshire

35   Cleared         100       No   13.5 10.8  9.4            40   29   19

                  (3) Mixed Hardwoods, Northern West Virginia

30   Cleared         100       No   10.3                      —
23   Clearcut        100      Yes    5.1  3.4  3.5  0.6  2.2  19   16   —
       (except       (83b)
       for culls)
30   Clearcut         50       No    6.1  5.8                 —   —
26   Selection cut      36      Yes    2.5  1.4  0.3  1.2 -0.2  10    5    1
30   Selection cut      22      Yes    0.7  0.1 -0.7 -1.6  0.7   2    0   —
25   Selection cut      14      Yes    0.3  1.3  0.3  0.3  0.0   1    5    1
4   —

1    0
                                               m.12

-------
                                           Table III.1.—continued
                                      Percent
                 Mean                of area
 Forest   Mean  annual   Silviculture)  or basal
 area   precip- steam-     activity    area(b)
(acres)   itation   flow                 removed Regrowth  1
                                              Water yield increases by years after silviculture! activity:
 106
 237
 250
 200
 714
1,163
 248
 318
 323
  95
  46
  12
 875
         ---Inches ---
37     13
90     57
90     57
30
27
32
32
19
     Clear cut
     Clearcut
     Clearcut
                                 	Inches	Percent-
               (4) Oak Type, Central Pennsylvania

                  20
            No    2.7

(5) Douglas-fir, Western Oregon
                          17
                 100      Yes  18.2 18.0                  36   33
                  30      Yes   5.9   6.4   5.9  11.7  8.9  16   14    19   38   24
21      6.1   Clearcut
                    (6) Aspen and Conifers, Colorado

                      100       Yes    1.4   1.9   1.0  0.8   0.5   19   27   16

                    (7) Lodgepole Pine and Spruce-Fir, Colorado
                                                                           12   12
                 11
3.2
3.4
3.4
0.9
     Clearcut
Clearcut
Selection cut
Selection cut
                  40
            Yes
3.3  5.2  3.7   4.6   5.4   32   35   43   63    71
(8) Mixed Conifers, Arizona
   16       Yes    1.2
                          16
   32       Yes    0.5   2.0  1.6   1.9   1.2   56
   45       Yes  Nonsignificant
                               45   —    —    —
               (9) Utah Juniper, Central Arizona

Cabled, burned, 100       Yes   Nonsignificant
seeded to grass
               (10) Chaparral, Central Arizona
26      2.2
26      2.2
     Herbicide
     Herbicide
                 90       Yes    3.4   3.0   2.6  9.8  14.2  111   292  589  451  235
                 40       Yes    3.0   0.9   1.8            299   517  223
                         (grass)
          25     4.1   Chemical kill
                           (11) Oak-Woodland, Central California

                             100       Yes   4.0   7.9   4.0
                                      (grass)
                                                                 25   65  300
26      2.5
                   (12) Chaparral with Woodland along Streams, Southern California

     Riparian cut     2-4       Yes   0.4                        —
                                                  IJ.I.13

-------
                                       Table 111.1.  — continued
                                 (13) Ponderosa pine, Beaver Creek, Arizona
                   Mean
      Watershed no.  winter
         and year   stream
                   flow
                         Difference between predicted and
              Percent of     actual streamflow by years
            area treated or     after silviculture! activity
Silviculture!    basal area (b)
  activity        removed    123456
Mean difference

12,1967
9,1968

17,1969
14,1970


16,1972
Inches
6.04
6.70

7.63
4.71


5.45

Clearcut
Clearcut in uniform
strips
Thinning
Clearcut in irregular
strips, thinning
between strips
As above

100
32

75
50


65

3.79
1.98

.85
.71


5.60

0.92
.61

1.45
.70




1.81 1.47 1.39 3.29
.34 .84 1.74

1.51 2.93
1.61



Inches
2.00
1.10

1.68
1.01


5.60
Percent
35
16

222
21


103
       Blank = no data available; dash = no percent given in source reference.
  THE BASIC HYDROLOGIC PROCESSES
               AFFECTED BY
        SILVICULTURAL ACTIVITIES
  General Consideration — Vegetative Cover


  In snowfall dominant regimes, vegetation will be
briefly mentioned in terms of the parameter forest
cover density.  In rainfall dominant regimes, this
parameter is leaf area index or vegetal surface.
  Obviously, every stand has both a leaf area index
and a  cover  density,  but  they  may  not be
numerically  correlated.  Cover density  is  most
significantly reflected in defining energy transmit-
ted to the snowpack, while leaf area index relates to
the potential for dissipating energy in the canopy
through evaporation of intercepted water and by
transpiration.  The terms are conceptually  syn-
onymous, but differing definitions were required by
the nature of the parameter use in the model used
to develop the  relationships for the handbook.

Forest Cover Density (Cd)

  Forest cover  density (Cd) is an index, which
theoretically ranges from zero to less than one, and
references the capability of the stand or cover to in-
tegrate and utilize the energy  input  to transpire
water.  It  represents the  efficiency  of the three
dimensional  canopy  system to  respond to  the
energy input. It varies  according to crown closure,
vertical foliage distribution,  species,  season,  and
stocking.  It is  significant in defining the energy
transmitted to the ground  or  the transmissivity
coefficient. The cover  density  and transmissivity
coefficient do not add up to one. Some estimates of
cover density and transmissivity are listed in table
m.2.
                          Table III.2.—Ranges of forest cover density and transmissivity
Forest type
Lodgepole pine
Spruce-fir
Aspen
Foliated
Defoliated
Forest cover density
0.25-0.45
0.50-0.65
0.35
0.20
Transmissivity
0.35-0.30
0.30-0.25
0.35
0.50
                         The Leaf Area Index (LAI)

                           The leaf area index (LAI) is used in areas where
                         precipitation  is  lost  most significantly by the
                         evapotranspirational process. It is the ratio of leaf
                         surface area to ground surface area. Rather than in-
                         dexing transmissivity, it indexes the area of the
                         major intercepting  and  transpiring surface (the
                         ratio of area of leaf surface to ground surface).
                           As the vegetation reoccupies  an area that has
                         been cut, forest cover density (Cd) or leaf area index
                         (LAI)  increases with  time  until reaching a  max-
                         imum value with respect  to utilization of water
                         given the available water and energy. The rate at
                         which forest cover reaches this plateau depends on
                         environmental  conditions,   stocking  levels,  and
                         species.   For  example, in  subalpine  coniferous
                         forests  in the Rocky Mountains, full  hydrologic
                         recovery can vary from 30 to more than 80 years. In
                         contrast,  in the humid climate of the eastern Ap-
                         palachians, hydrologic recovery to pre-silvicultural
                         activity levels can occur in just  a few years.
                           Once adequate vegetation has been established
                         on a cutover site, the time span for recovery to full
                         hydrologic utilization or pre-silvicultural activity
                         levels varies. These time spans begin after success-
                         ful  regeneration has been established. For Ap-
                         palachian hardwoods  the lag time between harvest
                                                III. 14

-------
and establishment may be less than 1 year, while it
may be 15 to 30 years for spruce-fir in the sub-
alpine. Hydrologic recovery may occur in as little
as 5 years for Douglas-fir in the Pacific Northwest
once the regeneration has been established.
     Effects Of Silvicultural Activities On
                 Precipitation


  Precipitation is a key input to the hydrologic cy-
cle. Though simply stated in the  hydrologic equa-
tion (eq. III.l), it is affected by a host of dynamic
processes  which range  from large  scale
meteorologic-topographic   interactions   to   local
precipitation that falls on a watershed surface.
Effect Of Silvicultural Activities On
Precipitation As Rainfall

  The distribution of precipitation which occurs as
rainfall is affected to a lesser degree by Silvicultural
activities than distribution which occurs as snow-
fall.  The  most significant  alteration due  to
silviculture takes place in the interception process.
As these vegetative surfaces are reduced by timber
cutting, so is interception loss; the result is that a
greater  percentage  of gross  precipitation  is
available to the soil water system.
Effect Of Silvicultural Activities
On Precipitation As Snowfall

  In  some  areas  in which the major form  of
precipitation  is snowfall,  the  meteorological-
topographic relationship as it affects snow distribu-
tion may not be significant; but in other areas, it is.
In the Rocky Mountain/Intermountain region, for
example,  snowfall  is  the  dominant  form  of
precipitation, and windblown snow  dominates the
regime. In  this area, when the forest cover  is
removed through spatially  distributed openings,
snowfall distribution is changed.  Put another way,
the aerodynamic characteristics  of  the watershed
are modified through Silvicultural activities.
  Objective methods for quantifying the univer-
sality of the effects of  Silvicultural activities on
snow  redistribution through snowblowing are not
yet available,  and quantification of these  effects
must  be based on considerable judgment and ex-
perience in a particular  area.  However,  a few
generalizations can be made for those areas where
it has been observed to occur, such as in the dry
snows of the Rocky Mountains.
   The aerodynamic change in roughness of the
vegetative surface. — This modifies  patterns of
snow accumulation, so that more snow may ac-
cumulate in the cutover area and less in the uncut
forest. Significant increases in snow accumulation
near the center of small forest openings are largely
offset by large decreases in snowpack below the un-
disturbed forest so that total snow  storage  on
watersheds  subjected  to  cutting is not changed.
When openings  are  large,  greater than 15H in
diameter  (H  =  height  of surrounding  trees),
however,  total  watershed snow  storage may  be
decreased through large  sublimation  losses and
transport of snow out of the basin (fig.  HI.6). The
technical basis  and  procedures  for  computing
retention coefficients for openings beyond 15H were
developed by Tabler  (1977) and presented in  ap-
pendix A. Figure in.6 can be used as  a guide for
openings beyond 15H, but for site specific applica-
tions beyond 15H, the equations in appendix A are
recommended.
   Retention of snow as a result of forest cutting.
— Snowfall is the major form of precipitation in the
Pacific Coast province (Sierra Nevada and Pacific
North Coast)  above elevations ranging from 6,000
feet elevation in the  Southern Sierra  Nevada to
4,000 feet elevation in the Northern Sierra Nevada.
However, considerable quantities  of precipitation
fall as rain or mixed rain-snow at elevations up to
3,000  to 4,000 feet above these  lower  baselines.
Snows are wet, and windblown snow may seldom
result  in appreciable  redistribution of snow. The
relation between snowpack depth  and  water con-
tent between  snowpacks  in the open  and under
various forest densities varies with (1) time of year
(reflecting influence of differential melt); (2) per-
cent of precipitation that was rain vs snow; (3) size
of snowstorms (which affected placement of snow
lodged on tree canopies); (4) species crown type;
and (5) melt regime as affected by aspect.
   Studies in Canada (Swanson and others 1977)
and the United  States show that any large reten-
tion of snow as a result of forest cutting can be an
important factor in determining  the  amount of
runoff. For example, in the lodgepole pine type in
Colorado, this redistribution effect is not greatly
diminished 30 years after timber harvest, in spite of
regrowth of trees and associated increase in forest
cover density. It is thought that changes in natural
snow  accumulation patterns produced  by timber
                                                III. 15

-------
                                  10               15             20
                                    DIAMETER OF CLEARCUT
                                          (in multiples of H)

                     Figure III.6.—Snow retention t» a function of size of clearcut.
                               H is the height of surrounding trees.
25
30
Figure III.?.—New growth does not affect total snow storage in this lodgepole pine area of the Fraser Ex-
  perimental Forest. This 8-acre plot, cut 28 years ago to remove all but 2,000 of trees larger than 9.5 inches
  dbh, still functions as an opening, with wind controlled by surrounding old-growth forest (Leaf 1975).
                                            m.i6

-------
harvest will persist until the new crop of trees ap-
proaches the height of the remaining undisturbed
forest (fig. HI.7).

  The significance of the snow retention coef-
ficient in the Rocky Mountains. — This lies in the
opportunity that exists for both decreasing the net
water loss from the pack and for altering the melt
rate. As already noted, it can be expected that the
transpiration  losses  in  the openings  will  be
decreased following cutting. The magnitude of in-
crease in plant water use after cutting is  dependent
upon many  items.  One  of the most  important
relates  to size of the opening and the extent that
roots from trees on the periphery reach  into the
opening. Also, if the area lies on a slope, some of the
"saved" water resulting from transpiration reduc-
tion will migrate downslope into forested areas and
be utilized by timber growing downslope from the
cutover area. By placing a greater percentage of the
total snow pack in these openings and  less in the
residual forest, one can expect  to reduce the ex-
posure of the net precipitation (in this case snow)
to  evapotranspirational processes.  Because  this
snow is redistributed and because cover  conditions
have been altered, we are exposing a significantly
greater proportion of the pack to sunlight, and can
expect differing melt rates. In contrast,  as the size
of the  opening increases (beyond 15H),  the oppor-
tunity for increased ablation losses and wind scour
can reduce  the  net  precipitation below  pre-
silvicultural  activity levels. This effect is signifi-
cant in that it represents a net loss in water input
to the system.
  Optimum  redistribution of snow.   — In old-
growth subalpine forests, optimum redistribution
of snow occurs when (a) the stand is harvested in
small patches of less than 5H in diameter; (b) the
patch  cuts are protected  from wind; and (c) the
patches are interspersed at least 5 to 8H apart. It
should  be  emphasized that the  redistribution
theory is valid only when timber is harvested in
small patches which occupy less than 50 percent of
the watershed.
  Since we are talking about a redistribution of a
finite amount of snow, there is a contributing area
for  the increases occurring in the openings. The
area of contribution is about equal to the opening;
therefore, if the openings occupy  more than 50 per-
cent of the area, redistribution will be less efficient.
In these situations P0 would have to be adjusted to
reflect the limiting contributing area. If the area
cut exceeds 50 percent, the following adjustment in
Po can be used:
                     (p0-D(.50/X)
                              (HI.3)
where:
 Poadj
 Po
adjusted snow retention coefficient
snow retention coefficient from figure
HI.6
      X =
                 open area
           total impacted area

  For purposes of this handbook, areas impacted
by patch  cutting can be defined by a perimeter
around the cutting unit located approximately the
width of the patch cuts away from them. It should
be noted  that wind protection implies an  equal
perimeter width below ridge tops and known wind
exposed areas.
Effect Of Silvicultural Activities
On Snowmelt Processes
  The effect of silvicultural activities on complex
snowmelt processes cannot be conveniently deter-
mined using a total energy balance model. A com-
promise procedure is to consider radiation as the
primary energy source available for snowmelt and
to concentrate on energy-vegetation interactions.
  Snowmelt is assumed to be affected by: (1) In-
coming shortwave radiation adjusted for the reflec-
tivity on  the  snowpack;  the  net can vary from
about 0.90 to 0.4, depending on such factors as age
of the snowpack surface and other conditions; (2)
longwave radiation balance between the snowpack
and sky; and (3) the longwave radiation balance
between the forest cover and snowpack.
  These  factors are,  in turn,  related  to two
parameters  — transmissivity (percent  of solar
radiation which passes through the forest canopy to
the forest floor) and the forest cover density, these
will be discussed under the heading "Vegetation."
  The addition of rainfall or snowfall to an existing
snowpack is another factor determining the  melt
rate  of snow,  and  thus the amount of  water
available for infiltration.
   Effects of a rainfall event on snowpack
energy. — Effects of a rainfall event on snowpack
energy can be indexed by computing the caloric
gain due  to rainfall. If the snowpack is cold, the
caloric input from the rain is  used to satisfy all or
part of the caloric deficit in the snowpack itself. If
the input more than satisfies the deficit, then the
remainder is expressed as energy in free water; the
caloric input from that water is allowed to generate
other melt.
                                               III. 17

-------
  The melt-producing capability of rain on snow is
small, however. For example, 1 gm of rain at 8° C
will release  approximately 8 calories of  energy/
square cm to an isothermal pack. This will pro-
duce 0.1 g of melt or 1.1 cm of runoff.  However,
if the snowpack is cold, the  rain will freeze and
release an additional 80 calories of energy and may
rapidly bring the pack to an isothermal condition.
  Effects of condensation  on snowpack energy.
—  In contrast, condensation on  an isothermal
snowpack is  significantly more efficient  in adding
energy to  the  pack  as  it  releases about  600
calories/gm of condensation/square cm.  However,
it is unlikely that more than a fraction of the total
energy in the pack is added by  condensation.
  Effects of snowfall on  snowpack energy. —
For snowfall, the effects on  the pack  are similarly
indexed by computing the  caloric  gain or loss due
to snowfall.  If the snow falls within the "warm"
range of 32° to 35° F there is  no  caloric loss.
However, snow  falling  at lower temperatures in-
creases the caloric deficit.
  As  suggested by the brief discussion above,
energy dissipation with respect to snowmelt is com-
plex  and  alterations  in energy balance  due to
silvicultural  activities further  complicate  the
process, both in respect to defining the process and
in quantifying the process  once defined. In sum-
mary, timber harvest may alter both the accumula-
tion and the melt  rate of the snowpack.
Effects Of Silvicultural Activities On Infiltra-
tion Rates

  Unless soil disturbance occurs (which is always
the  case with roads,  skid trails,  or  log  decks),
silvicultural activities do little to influence infiltra-
tion directly. Water will  still infiltrate the un-
disturbed,  unsaturated  soil  surface. It must be
noted, however, that soil moisture levels may be
higher following  harvesting  (as   discussed
previously) and available storage capacity may be
decreased,  depending on pattern and intensity of
harvest, season, region, etc. Decreased storage will,
in turn, limit the infiltration process in some places
and, for some events, speed up the flow of subsurfce
soil water in others, thus indirectly affecting the
pathway of water to a channel.
  It is beyond the scope  of this section to attempt
to quantify the impact of soil disturbance on either
infiltration or water routing. Silvicultural activities
result in mechanical disturbance of 5 to 15 percent
of the harvest area (primarily in roads and skid
trails). We have already described the potential for
intercepting  rainfall,  snowmelt,  and  subsurface
water with the road net. The problem is increased
following harvesting since the soil  will be wetter,
the opportunity for intercepting subsurface water
greater,  and  the potential  for  affecting  the
hydrograph greater. However, by properly locating
roads, such as building them higher on the hillside,
maintaining  adequate drainage  structures at
proper intervals, and utilizing the other control
practices recommended, the water falling  on the
disturbances and  intercepted by the cuts can be
redistributed over the basin and infiltrated prior to
reaching the  channel, thereby minimizing the im-
pact on the hydrograph.

Influence  Of Silvicultural  Activities  On
               Evapo transpiration
  The  evapotranspiration   process  is   most
significantly  modified  by silvicultural activities.
Figure HI.8  illustrates the relationship  between
stand reduction and evapotranspiration rates.
  In figure III.8,Ea  is the actual evapotranspiration
rate based on stand  condition  and  Es  is  the
potential rate computed by any one of a number of
empirical equations. The figure demonstrates the
relationship  between  fully  forested  (complete
hydrologic  utilization), open (minimum hydrologic
utilization),   and  intermediate  conditions  in-
dicative  of the range  of  relative water use  im-
mediately after, and several years after, harvesting.
One may reasonably assume that water use under
 O
 tr
 o_
 Ł
 <
 LU
       100 —
O
O
    (0  en
 _ tU |UJ

 111
 O
 0.
 I-
 -z.
 HI
 O
 cc
 LU
 CL
    Wilting Point               Field Capacity
            AVAILABLE SOIL WATER
Figure 111.8.—Relationships showing evapotranspiration as a
  function of available soil water for: Old-growth forest and
  open conditions and complete hydrologic utilization.
                                               m.i8

-------
complete hydrologic utilization during the growing
season proceeds at rates limited only by available
energy until  soil water itself is depleted to some
threshold  value. The  threshold assumed in figure
III.8 is 50 percent of the maximum available for
transpiration (i.e., 50 percent of the field capacity
index);  thereafter,  transpiration  is  assumed to
decrease in proportion to the amount of soil water
below one-half of the field capacity index.
  Under the open  condition, actual evaporative
loss occurs at the potential rate when the soil is at
or above field capacity, but it drops to zero very
quickly as  the  soil   dries slightly  below  field
capacity.
  As  forest vegetation  reoccupies cutover areas
(i.e., the partially recovered curve) and consump-
tive use is increased, the relationship expressed in
figure in.8 changes until,  as the  forest cover is
reestablished, it ultimately  approaches that of the
fully occupied forest. It is this phenomenon which
is primarily responsible for diminishing water yield
increase over time  following timber harvest.  The
rate at which this transition occurs depends upon
forest species, climate,  and stand conditions.
  The rate at which complete hydrologic utiliza-
tion is reestablished depends also  on the type of
vegetation that reoccupies the site and on its origin
and  subsequent management.  Some tree species
(for example, spruce-fir forests) are very difficult to
regenerate and,  therefore,  require  the longest
period of time for regrowth. Other species, such as
northern hardwoods, do not require as much time
to reestablish themselves. Finally, many cutover
areas can be subjected to vigorous regrowth — be it
from sprouts, seeds, or herbaceous vegetation —
and as a result, complete hydrologic utilization of
the site takes place in a relatively  short period of
time.
  The implication which can be drawn from the
relationship expressed  in figure  ni.8 is that the
result of a reduced  transpirational  loss will main-
tain  higher soil moisture levels. We have already
described the potential effect of the higher antece-
dent conditions on infiltration, storm response, and
increased flow levels.
  In humid regions, the increased growing season
flow levels can increase the length of the first order
perennial  channels. This can be effective in in-
creasing  the amount   of channel precipitation,
although this will  have minimal  effect on  the
hydrograph. More important  might be the con-
tinual  channel scour  associated  with  the
lengthened channel.
                 SUMMARY

  The potential impact  any silvicultural activity
will have on the hydrologic response of a basin,
either short- or long-term, can  be evaluated in
terms of the changes  which  will occur  in the
balance components of precipitation modification,
evaporative changes, and storage changes.
  In considering the impact of the removal of forest
cover  on evapotranspiration, soil  moisture  and
streamflow levels, we have described the expected
changes. There are exceptions,  especially  local
problems,  which  need  to  be  interpreted  and
evaluated by the user.
  For example, in the black spruce bogs and fens of
the Lake States region, strip and clearcutting ex-
periments have shown little effect of treatment on
annual water yield  from high water table organic
soils (Verry 1976). Higher water tables have been
observed on these sites during rain events following
clearcutting,  while  these same sites  have  lower
water tables  during extended dry periods; but on
an annual basis, there is no net change in either the
evapotranspiration loss or water yield. Apparently,
high water table areas evapotranspire at the max-
imum rate regardless  of the vegetation present.
This assumes, of course, that free water is available
at the  surface, either  directly  through  organic
"wicking"  or by the presence of  adequate lush
lower  vegetation. The same principles  would apply
to other high water table sites in both organic and
inorganic soils throughout this  and other regions.
Whenever the water table is at or near the surface,
evapotranspiration will occur at or near maximum
rates,  regardless of the vegetation present, and any
modification in the vegetation due to silvicultural
activities will have  little effect on evapotranspira-
tion or streamflow.
  In using the subsequent methodology to evaluate
the impact  of silvicultural  activities  on  the
hydrology  of the  planning unit, the  user is
cautioned  to weigh the effect, if any,  of the
presence of high water table sites, regardless of the
hydrologic  region. Needless  to say, a significant
portion of the  Lake States, New  England,  and
Coastal Plain regions would have high water areas
on which silvicultural activities would have little
effect on the total water balance. This represents
one of many localized site specific situations where
the user will have to  adjust  the methodology-
derived answer to fit the application. The basis for
doing  so  is  outlined  in the  discussion on the
hydrologic  cycle and management impacts on it.
                                               m.19

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PROCEDURE:  EXPLANATION OF THE METHODOLOGY FOR PREDICTING
IMPACTS OF SILVICULTURAL ACTIVITIES ON THE HYDROLOGIC CYCLE
       PROCEDURAL FLOW CHART
  The basic  procedural steps for estimation  of
water yield changes due to silvicultural activity are
presented in chapter I. More detailed flow charts
are presented  in subsequent procedural sections.
They appear  as figures III.9,  EI.21, IH.23, and
m.57.
  In essence,  the methodology  extrapolates the
results of research and long-term observations on
specific  sites  to  other offsite  locations.  The
methodology is intended to complement sound
scientific judgment, not replace  it; and to insure
reasonable  evaluations where, because of the lack
of experience, the judgment is less than optimum.
       PROCEDURAL DESCRIPTION
  This  section  contains  the  procedures  and
methodology developed  to  predict  the impact of
silvicultural activities on the hydrologic cycle, and
is presented in a regional format. The regional coef-
ficients and modifiers were developed from simula-
tions using  available   hydrologic  models.  The
specific models and assumptions for their use are
presented and documented  in appendix B.
  The continental United Sates was stratified into
five hydrologic regions, as depicted in figure IH.9a,
based on major climatic  and hydrologic influences.
Observed data from representative and experimen-
tal  watersheds from each  region  were used  to
calibrate the models. The data base, in terms of the
number  of calibration  years and the number of
watersheds, varied for each region and each model.
However, given the constraints,  all available data
were utilized. Time  was the most  critical factor,
but  data were  also limiting  in terms of both
availability and in terms of the format in which it
was  available — if it existed. In calibrating the
models, there was no true statisitcal evaluation of
the simulation; "goodness of fit" was subjectively
interpreted by how well the simulations matched
either the observed hydrograph, soil moisture dis-
tributions as they  were  understood,  or  local
evapotranspiration estimates.
  The objective was to extrapolate the experimen-
tal observations  for regional use. Admittedly, the
effort did not  produce a  comprehensive  work
reflecting all the regional variability; therefore, site
specific information  should be supplied whenever
possible. However, the total effort is geared to the
long-term, annual and seasonal water balance,  by
region. In this respect the methodology is adequate
for characterizing response, given the current state-
of-the-art.
          Use Of Site Specific Data
  The format used in developing the analytical
procedure segments the methodology to allow in-
corporation of local or site specific data bases where
possible or to allow use of differing assumptions or
techniques, if necessary, so that the analyses would
be  more site  specific.  The  coefficients  and
modifiers presented  are regional and  should be
used  only if  a site  specific  data  base  is  not
available. The  analytical framework presented is
sound, however, and will yield reasonable results
which are applicable in the respective regions.

  For example, the variability in regional snow-
pack  development and characteristics has been
recognized, but not all variability has been  ad-
dressed.  The main concern was to look  at  the
response to the  input  of  water  within the
framework of a hydrologic balance. The  energy
balance equations used in developing the snowpack
relationships  are  radiation-  and  temperature-
driven, and the results should be compatible in
each region. The basic principles in  the snowmelt
model used  in the  simulation analysis were
developed in the Far West and recently adapted for
use in the Rocky Mountain/Intermountain region.
Thus, it is believed that the simulation of snowmelt
and rain-on-snow occurrences in the Central Sierra
and Pacific Northwest, for example, are reliable. A
review of current  modeling procedures applicable
to these regions did not lead to other conclusions.

  The site specific role of certain relationships also
needs to be evaluated. Based on research, primarily
in the Rocky  Mountains, snow retention coef-
ficients are to be used to "redistribute" snow fol-
lowing cutting in those areas where blowing snow is
significant. However,  blowing snow is not neces-
sarily significant  everywhere that  snow occurs.
This requires an interpretation. By the same token,
                                              m.20

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the retention coefficients themselves  may not be
exact for every site on which blowing snow does oc-
cur, requiring another decision. The relationship is,
however, the only one that has been quantified. Its
use is recommended if a site specific improvement
is not available.
   The same cautions apply to the  estimates of
regional evapotranspiration,  the estimates  of
rooting depth impacts, and so on. Any site specific
information should  improve the evaluation. In
many applications, however, there may not be site
specific data available.
       Use Of The Annual Or Seasonal
              Hydrologic Budget


  The methodology is oriented toward the annual
 or seasonal hydrologic budget. It is recognized that
 the  most significant opportunity for impacts on
 non-point source pollution may be associated with
 individual short-term events. In the South or East
 these  may  be large rainfall events  or thunder-
 storms.  Combined events such  as  rain-on-snow
 may be  extreme in areas such as  the  East, the
 Northeast, or the Pacific Coast. The magnitude of
 the response to these events, however, is a function
 of  the time  of the  year in which they  occur
 (reflecting antecedent conditions), the size of the
 event (be it rain, rain-on-snow, etc.), and its dura-
 tion.
  As part of evaluating the potential impact of the
silvicultural activity on these events, the long-term
balance should first be evaluated and then the
short-term event superimposed on the evaluation.
Obviously, if the soil moisture regime is the same in
both the undisturbed forest and the harvested area
(as is known to occur during winter in many areas),
a significant change in the magnitude of the event
may not be  expected (assuming the  routing or
pathway water takes to the channel has not been
significantly altered). For example, rain-on-snow
events most often occur when basins are recharged,
regardless of  the vegetal  state;  although  the
hydrologic response may be extremely significant,
the effect of the silvicultural  activity itself may be
insignificant.  Summer  events  are often
significantly increased because of higher antece-
dent  moisture  following  harvest.  But  because
neither forest nor harvested area is likely to be fully
recharged during this  period, the respose will still
not be as great as if the event occurred at a time
when  the basin was  recharged. Therefore  it is
necessary to deal with such events individually on
a "design-storm basis." Basic understanding of the
processes that govern stormflow is weak, but stan-
dard methodologies for prediction are referenced,
nevertheless.  The  most  significant basis  for
characterizing changes in  design storm  response
due to silvicultural activities results from changes
which occur in  the long-term hydrologic balance
and is  reflected in the antecedent soil-moisture
conditions.
                                                    No Quantification On The Hydrologic Impact
                                                             Of Mechanical Disturbances
  Quantification  of the  hydrologic  impacts of
mechanical disturbance such as roads, log decks,
and their location cannot be made, although they
have been have qualitatively defined in the earlier
sections in  this chapter.  Using the  criteria
described, the impact of the disturbances on the
hydrology can be minimized using best manage-
ment practices; and subsequent chapters deal more
directly with their impact on pollution and ap-
propriate controls.
     The Importance Of Onsite Response


  The  overall  methodology  deals  with  onsite
responses. The ultimate response in the channel or
at some point  downstream is a routed response
which integrates the complexity of the basin, the
location of the  silvicultural activity, the area ac-
tually logged, and the routing characteristics of the
watershed. Do  not interpret the onsite responses
determined by the proposed methodology as being
a streamflow response, unless local data justify this
assumption.  On  small  (first  order)  headwater
streams, the assumption may be justified. (The ex-
ample presented in this handbook was developed
with the assumption that onsite responses closely
approximate streamflow responses.)


         Use Of Models To Simulate
             Hydrologic Response


  Two models were selected (see appendix B) to
simulate the hydrologic response of differing levels
of harvest on the hydrologic balance. The models,
PROSPER (Goldstein  and others 1974) and the
Subalpine Water Balance Model (WATBAL) (Leaf
and Brink 1973a, 1973b), were used to develop the
                                              in.2i

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hydrologic methodology and procedures presented
in this section. Calibration and validation of WAT-
IS AL and PROSPER are presented in appendices C
and D, respectively. Regional evapotranspiration,
soil  moisture regime,  and  water available  for
streamflow represent simulated averages using the
data base available for the models. The modifier
coefficients presented  to adjust the various compo-
nents of the  hydrologic balance reflecting aspect,
rooting  depth, and  elevation as a  function of
silvicultural activity were developed from simula-
tions  also.
  There are several points to be made about  the
models.
  An evaluation of the methodology (and the ac-
tual modifiers) was made based on how well the
procedural  estimates compared  with  observed
changes from cutting experiments on  various ex-
perimental watersheds. Because of its  nature, the
emphasis of the procedure may appear to generate
absolute values for the annual balance; however,
the objective is  to estimate the change  in  the
balance that will result from  a particular activity.
As such, the methodology is intended primarily as
a planning tool useful  in evaluating the relative
hydrologic  impact  of various management  alter-
natives. Although the regional variability of the
hydrologic  balance is great  in terms  of absolute
numbers, the strength of the  procedure is in  terms
of estimating the expected change (the variability
of which is not as great); thus, the inherent  errors
are not nearly as large.
  The prodecural format is to evaluate modifica-
tions  in the  evapotranspirational  demand before
and after vegetal modification. Potential changes
are then translated to reflect changes  in the soil-
moisture budget.  The  significance of any  soil
moisture or antecedent changes is then reflected in
terms of either potential changes in  short-term
storm response or in  long-term streamflow levels.
  To  those reading  both sections on the  basic
hydrologic  regimes (rainfall   and  snowfall),  dis-
crepancies  in regional  technique will seem  ap-
parent. The inconsistencies are real only to the ex-
tent that the technique has been fitted to a form
best suited to the confidence in the modeled output
generated for each region. The point is that incon-
sistencies in methodology are not real. This chapter
provides techniques for predicting the  general  im-
pact  of  various  silvicultural  activities   on
streamflow,  evapotranspiration, and soil moisture
as a function of aspect, soil depth, season, position
in the watershed, cover type, and climactic regime.
The format for presentation varies,  but is consis-
tent with  accepted practice in each  hydrologic
region and the overall objectives of the handbook.
  Although all of the  major hydrologic processes
were  simulated,  only  those responses  critical to
evaluating the impacts of silvicultural activities on
non-point source pollution are presented. These in-
clude evapotranspiration, soil moisture, and water
potentially available for streamflow.


Evapotranspiration

  The baseline  hydrology  of  the  representative
watersheds  was first simulated; then  the forest
cover was manipulated through a range from full
cover through various  partial  cuts,  to  complete
removal. The vegetation reductions were made
systematically, holding all  other factors constant
(soil depth, aspect, etc.). In some cases the other
parameters (depth, aspect, etc.) were then altered
systematically over all cover densities. Then the
modifier coefficients, or the percent change, were
developed  and extracted. These characterize the
change  in  evapotranspiration  — annual and
seasonal — for various cover density changes as a
function of position,  aspect, soils,  latitude, and
precipitation regime. This gives a technique for es-
timating evapotranspiration changes.


Outflow

  The most useful output  from the  analysis in
terms of non-point source  pollution are  the es-
timates of baseline and post-silvicultural activity
levels of streamflow. Techniques are presented to
predict  baseline  flow  relationships.  These must
then be adjusted to get post-silvicultural activity
levels. (1) For those regions  where hydrographs are
controlled  by   snowpack melt,  the  annual
hydrograph is  more  typically  uniform and the
techniques deal with shifts  in a "normalized" an-
nual hydrograph  of 6-day flow levels.  (2) For the
rainfall  regions,  a  "normalized"  annual
hydrograph will not be presented. Although flow in
these regions does follow a  predictable cycle, the
responses to individual events and other variances
are too great to "normalize." Instead, an expected
flow duration curve for average 7-day flow levels is
presented. The expected flow levels can then be ad-
justed for the proposed activity.

  Using this approach, users of the handbook can
supply their own baseline flow duration curve  or
                                               111.22

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hydrograph, if available, and adjust it using the
techniques presented; or they  can use the nor-
malized curve presented. Based on the simulations,
baseline  flow  levels  can be adjusted to represent
treatment effect to an adequate degree. However,
the state-of-the-art and nature  do not  permit
simulation of  the actual time dependent baseline
conditions for presentation in a handbook format.

 Soil Moisture

   Soil moisture distributions, annual and seasonal,
 were  extracted from  each  of the  simulations  to
 quantify the adjustment in soil water deficits as-
 sociated with cover changes, again as a function of
 position, aspect,  soil  depth,  and  precipitation.
 These moisture level adjustments can then be used
 to adjust the antecedent moisture condition for the
 pre-  and  post-silvicultural activity  storm  flow
 predictions which follow.
                Definitions Used


   In  the hope of minimizing ambiguity and in-
 creasing accuracy, several terms  require precise
 definition. The following definitions are intended
 for use in "Hydrology."
   Condition. — Refers to the hydrologic state of
 the watershed, i.e., baseline, existing, or proposed.
   Baseline condition.  — The hydrologic state of
 the watershed  in  which complete hydrologic
 utilization is achieved. It may be thought of as, but
 is not  necessarily  the  same  as, a fully forested
 watershed  with vegetation (primarily  trees)
 capable of maximum evapotranspiration (ET) for
 the energy and water available.
   Existing condition.  — The current hydrologic
 state of the  watershed.  It may differ from the
baseline condition in that hydrologic adjustments
have been made for vegetation differences from the
baseline condition. The existing condition is  syn-
onymous with the "pre-silvicultural activity  con-
dition."
  Proposed condition. — The hydrologic state of
the watershed following a proposed silvicultural ac-
tivity. It is synonymous with the "post-silvicultural
activity condition."
  Silvicultural prescription. — The management
alternatives applied to a  watershed or watershed
subunit. The delineation of a watershed into a
single  unit  or series  of  subunits to which  the
prescription is to be applied is based on uniformity
of soil depth, vegetation, precipitation, aspect,  and
other unique site factors.  A uniform practive over
the entire  unit  or several  practices resulting in
more than  one silvicultural state per silvicultural
prescription; i.e., the prescription may consist of
patch cutting, thinning, and leaving  part of the
area uncut.
  Silvicultural state. — The status of the vegeta-
tion complex  on  units  of  land  to  which  a
silvicultural  prescription  has  been  applied.  A
silvicultural system or treatment actually applied
to a unit or a description of the  vegetative cover on
all or a part of the unit. The state may be described
as clearcut,  thinned, forested, open, etc.
  Treatment. — Action  taken on vegetation by
nature  or  man,  including  no apparent action.
Silvicultural prescriptions may consist of several
treatments.
  Impacted area. — This refers to uncut and cut
zones of the watershed  which  are  affected  by
silvicultural prescription.
  Unimpacted  area.  —  Those  zones of  the
watershed which are unaffected by a silvicultural
prescription.
                                               m.23

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  PROCEDURAL DESCRIPTION: DETERMINING EVAPOTRANSPIRATION
                  AND WATER AVAILABLE FOR STREAMFLOW
                (ET ESTIMATION) (RAIN DOMINATED REGIONS)
                APPALACHIAN MOUNTAINS AND HIGHLANDS (REGION 2)
           GULF AND ATLANTIC COASTAL PLAIN AND PIEDMONT (REGION 3)
                      PACIFIC COAST REGION (PROVINCES 5, 6, 7)
  The following two sections describe methodology
for evapotranspiration and water yield calculations
for conditions found in the lower elevations of the
Pacific Coast hydrologic provinces (5, 6, and 7), the
Appalachian Mountains and Highlands hydrologic
region (2), and the Gulf and Atlantic Coastal Plain
and Piedmont hydrologic region (3).

  Examples  from three  watersheds —  Needle
Branch, Coweeta (watershed  #28), and Grant
Memorial  Forest (watershed  #1)  — have been
developed to demonstrate application  of the
methodology and to document the procedure. Sam-
ple worksheets for each watershed provide sum-
maries of the calculations performed by manipula-
tion of the variables described.

  The Pacific Coast region, a predominantly con-
iferous area,  is a combination of climatic and
physiographic conditions. Because snowpack
development did not seem to be a significant factor
in our simulations below 3,000 to 4,000 feet, the
PROSPER model was applied. Above that eleva-
tion snowpack development was significant and,
therefore, WATBAL was  used. This discussion
covers the lower  elevation with a  rain dominant
regime only; for the higher elevations see the sec-
tion concerned with snow dominated regions, and
figure in. 23 for the flow chart  describing the ap-
propriate methodology.

  Appalachian Mountains and Highlands region
consists primarily of mixed hardwoods, with some
conifers. Precipitation is moderate, ranging from
approximately 35-40 inches in some northern parts
to nearly 100 inches in higher elevations to the
south. Unlike  the other two regions, latitude was a
significant factor in quantifying the relationships
in the Appalachian Mountains and Highlands
region (2).

  The Gulf and Atlantic coastal plain and Pied-
mont  region  is primarily a coniferous-deciduous
forest  mix with extensive plantations.
          METHODOLOGY USED
           FOR DETERMINING
      EVAPOTRANSPIRATION AND
 WATER AVAILABLE FOR STREAMFLOW


  The flow chart of the procedure for estimating
evapotranspiration  is presented in figure IH9.
Evapotranspiration  estimates are subtracted from
precipitation data supplied by the user to estimate
water that is potentially available for streamflow.
Worksheets ELI and III.2 have been constructed to
follow the flow chart and to facilitate calculations.
They accompany the illustrative examples at the
end of this  section.
  The following discussion keys on the components
of the flow chart mentioned above and details each
step in the analytical procedure. Also noted in the
text are the worksheet columns in  which  the  ap-
propriate factor is entered.
           HYDROLOGIC REGION
               OR PROVINCE
  The region or province that characterizes the
hydrologic regime for the  watershed  of interest
must be decided, (fig. in.9a) Evapotranspiration
calculations  are  based upon regional  hydrologic
relationships.

                 LATITUDE
  Evapotranspiration loss was found to vary with
latitude (item 4 on worksheets) as well as season for
the Appalachian Mountains and Highlands region
(2). Latitude,  in this region, is analogous to the
energy-aspect factor for  snow dominated regions
discussed in subsequent  sections. The latitude of
the drainage under evaluation must be provided.
                                           m.24

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                                      (   Hydrologic Region or Province
                                     c
Latitude
                     No
                                                  Condition
                                            Silvicultural Prescription
                                                   Season
                                               Silvicultural State
                                                 Precipitation
                                                   Baseline
                                              Evapotranspiration
                                      No
                                                    Vege-
                                                  tation <
                                                Fully Forested?
                                                                    Yes
                                                        C
             Leaf Area Index
                                                              Evapotranspiration
                                                              Modifier Coefficient
                                                Rooting Depth
                                             Modifier Coefficient
                                      Yes
                                                                     No
                              Water Available for
                              Annual Streamflow
                                                   Yes
                                              Weighted Adjusted
                                              Evapotranspiration
Figure II 1.9—Flow chart of methodology for determining evapotranspiration and water available for annual
                                 streamflow in rainfall dominated regions.
                                                   111.25

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s

I
3

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                  CONDITION
            SILVICULTURAL STATE
  Calculations of evapotranspiration  and water
available for streamflow are made separately for
each  watershed  condition  (baseline, existing,
proposed).  Condition  applies  to  the  entire
watershed, and the  procedure (as flow  charted)
loops to this  point after evapotranspiration and
water  available for  streamflow have  been
calculated for each successive condition.
       SILVICULTURAL PRESCRIPTION
  For each  condition, divide the  watershed or
management unit into segments based on unifor-
mity of vegetation, soils and other factors defined
for  application of the silvicultural  prescription.
The prescription should be uniform for each seg-
ment or subwatershed and may be uniform for the
entire  watershed.  Similarly,  the  silvicultural
prescription  can be uniform (i.e., forested) for one
condition (existing) and varied (clearcut, thinned)
for  another (post-activity). Silvicultural prescrip-
tion designations allow flexibility to subdivide the
watershed into subunits  based on  significant
silvicultural   or hydrological  characteristics of
either the site  or the prescriptions.  This implies
subdivision based not  only on silvicultural prac-
tice, but also on  uniform soil depth, aspect, and
vegetation.
                   SEASON
  In many cases the watershed or subwatershed
may be characterized as a uniform compartment,
especially in the pre-treatment condition, due to
similarity of such  characteristics as vegetation,
soils,  and climate. However,  the  management
prescription may require several practices or treat-
ments  to  be applied to the compartment. When
this is  done,  the post-treatment situation may
result  in  different degrees  of vegetative cover
(silvicultural states) within each prescription.
  Evapotranspiration estimates are made for each
silvicultural state (items  6  and 7). Silvicultural
state or treatment designations are chosen to group
treatment areas of the watershed or watershed sub-
unit that  are   similar in  hydrologic  response.
Hydrologic response is related to  the  type  and
quantity of vegetation at a site and to such physical
factors such as slope, soil texture, solar radiation,
and precipitation regime. In rainfall dominated
regions, leaf area index (LAI) is a major criterion
for  treatment delineation (see below).
  The procedure is looped so that each silvicultural
state is considered individually  by season  and
prescription.
                PRECIPITATION
  Precipitation  (item  10)  for  the season under
evaluation must be supplied. This estimate may be
based on actual onsite measurements or taken from
other sources. Depending on the objectives, values
may represent long-term averages or extremes.
  Because the  modeling effort is strongest on a
seasonal or annual basis, four seasons were selected
to express the relationships in these  regions. Sum-
mer is represented by June, July, and August; fall
by September, October, and November; winter by
December, January, and February;  and spring by
March, April, and May. The procedure is looped so
that  all activities  within a  prescription are
summed for that season.
                  BASELINE
            EVAPOTRANSPIRATION
  An estimate of the simulated evapotranspiration
for each region can be obtained from figure IE. 10
(Pacific  Coast  provinces-low  elevation); figure
III. 11 (Appalachian Mountains and  Highlands);
                                               m.27

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   40
   35-
   30-
                                                                                            X
                                                                                               X
E 25.
o
                                                                                 X
LU
z
O
co
<
01
CO
   20-
                                                                             X
   10-1


    5-

    0
                SUMMER
                                            I
                                          FALL
                     I
                 WINTER
SPRING
        Figure 111.10—Simulated seasonal evapotransplratlon for the Pacific Coast hydrologic  provinces-
                        Northwest (5), Continental Maritime (6), and Central Sierra (7).
40-


35-


30-


25-


20-
O
03
<
UJ
                                Summer
                                Fall
                                  Spring
                                  Winter
           34  35  36  37  38   39  40  41
                  LATITUDE, degrees
                                          43
Figure 111.11.—Average  evapotranspiratlon for  the Ap-
 palachian Mountain and Highlands hydrologic region (2) by
                     latitude.
and figure III. 12 (Eastern Coastal Plain and Pied-
mont).  Estimates  of  monthly or  seasonal
evapotranspiration may  also  be  obtained from
other  sources if  site  specific  information is
available. Site specific estimates  improve subse-
quent  estimates of change and thus enhance the
evaluation.
  The values  provided represent the  simulated
evapotranspiration losses, by season, for the condi-
tions which existed in the years simulated. These
usually   differ  from  estimates  of  potential
evapotranspiration using  conventional empirical
techniques.  A seasonal  estimate  of baseline
evapotranspiration can be obtained directly from
figures III. 10, IE. 11, or 111.12 by season; or they can
be obtained from other sources if another estimate
is more correct for the site in question.
  Unlike the  snow pack  dominant regions, the
simulations did not show any direct relationship
between precipitation amount and evapotranspira-
tion losses.  Precipitation  throughout  the three
regions under  discussion is generally adequate to
maintain near potential evapotranspiration rates.
                                                m.28

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      40
      30-
   o
UJ
_l
z
o
111
      20-
      10 —
        Oi-
                                                                                      X
                                                                                         X
                                                                                            X
                                                                                  X
                                                                         X
                                                                            X
                       I
                   Summer
                                           Fall
   I
Winter
Spring
                                                 SEASON
                   Figure 111.12.—Seasonal average evapotransplration for the Eastern Coastal Plain
                                     and Piedmont hydrologic region (3).
This does not mean that evapotranspiration does
not vary with precipitation. It does mean that the
state-of-the-art and the models used are such that
in the rainfall regions, it is not possible to give a
predictive technique for evaluating the impact of
variations in precipitation on evapotranspiration
losses.
  There has also been much concern about  both
the effect of aspect on baseline evapotranspiration
and its post-treatment changes. There is only one
experimental  observation  isolating  this  effect
(Swift and  others  1975). PROSPER, the  model
used in hydrologic regions 2 and 3, and hydrologic
provinces  5,  6,  and 7, was  not sensitive  to
simulating aspect effects and detected only a minor
shift. Transpiration was about 5 percent greater on
south facing aspects than on  north facing aspects
for  baseline conditions  and  about  10 percent
greater than on north facing aspects for  the lower
leaf area index (post-silvicultural activity) levels.
In effect, the expected  response  in terms  of in-
creased flow would be slightly greater  on north
slopes  than  south, but the simulations did not in-
dicate  an effect even closely approximating the
level  observed  by Swank   and  Swift (1975).
Simulating  aspect differences should also include
effects of differing  soils,  vegetal  complexes,  and
                                                   precipitation.  If these were  included, the  dif-
                                                   ferences  would  be greater  than that for energy
                                                   alone as  aspect  differences  imply more than just
                                                   energy differences.
                                                     Once the baseline ET values have been obtained
                                                   from figures in. 10 to IE. 12, it must be determined
                                                   if the silvicultural state requires an adjustment in
                                                   ET for changes in vegetative cover.
                                                                    VEGETATION
                                                                      < FULLY
                                                                    FORESTED?
                                                     If vegetation for the silvicultural state under con-
                                                   sideration is less than the fully forested baseline
                                                   condition, modifier coefficients are used to adjust
                                                   evapotranspiration  accordingly.  (Modifier  coef-
                                                   ficients will be discussed shortly.) If vegetation is in
                                                   the fully forested baseline condition, no evapotran-
                                                   spiration adjustments  are necessary,  although a
                                                   site  specific  adjustment may be necessary  for
                                                   rooting  depth differences.  Therefore,  if dealing
                                                   with baseline conditions, the analysis moves to the
                                                111.29

-------
rooting depth considerations.  If vegetal  modifica-
tion from baseline exists or is planned as part of
this step, continue to leaf area index.
               LEAF AREA INDEX
  Leaf area index is used to obtain the evapotran-
spiration modifier  coefficient which, in turn, ad-
justs ET to above ground vegetation conditions. If
the leaf area index (LAI) (item 13) for the site is un-
known, basal area  may be used  to estimate it.
  The leaf area index (LAI) is used to index tran-
spiring surface, and it is the ratio of leaf surface
area to ground surface area. Rather than indexing
transmissivity, it indexes the area of the major in-
tercepting and transpiring surface.
  The model used for the rainfall regions simulated
evapotranspiration losses based on the leaf area in-
dex of the watershed. Estimates for the baseline
leaf area index (LAI) used in the local calibrations
came from scientists at each of the representative
installations.  In many cases it was measured; in
other cases it was an estimate based on experience.
If the necessary information is not available, basal
area (BA) must be converted to leaf area index.
Basal  area should  be readily available since it is
used for planning most silvicultural activities.
  Because of the complexity of basal area-leaf area
index  relationships and present inability to quan-
tify them, it is strongly recommended that a local
expert be contacted to obtain estimates for existing
and proposed conditions for each treatment. If this
is impossible, the curves for hardwoods and con-
ifers provided in the following figures  can be used
to  provide  a  first  approximation.  Complete
hydrologic utilization is simulated whenever leaf
area index exceeds 5 or 6, so the errors associated
with  estimating  the upper  levels  of LAI  are
probably not too great.
  Figure HI.13 represents a first approximation of
the basal area-leaf area index relation for reduc-
tions in a mature hardwood forest and the regrowth
curve, assuming the site was cleared.
  To perform a time series or recovery evaluation,
one would treat   the post-silvicultural activity
evaluation as baseline and work  backwards by es-
timating LAI for various  time intervals along the
regrowth curve.
        10    20   30   40   50   60   70  80   90  100
Figure 111.13.—Leaf area index-basal area relationship tor
  hardwood stands  in the Appalachian  Mountain and
                  Highlands region.
  A preliminary  estimate  of the LAI/BA
relationship for conifers appears in  figure III. 14.
Because of lack of data there was no attempt to ex-
press a regrowth curve.
  Once the LAI for the silvicultural state under
consideration has been estimated, the appropriate
ET modifier coefficient can be determined.

QO

34
32
30
x 28
ui
Q ?fi
Z
<
LU 22 --
< 20

< 18
LU 16
14

10
8
g
4
0




















/
/
/

















/
/

















/
/
/

















/
/

















/
/
/

















/
/

















/
/
/

















/
/









































20   40   60   80  100  120
          BASAL AREA, ft.2
                                    140  160  180
Figure 111.14.— Leaf area index-basal relationship for conifer
stands in the Appalachian Mountain and Highlands region.
                                                ni.so

-------
                 ET MODIFIER
                 COEFFICIENT
  The appropriate modifier coefficient (item 14)
that needs to be applied to the baseline evapotran-
spiration estimate (item 11) can be determined by
entering the appropriate  LAI  into figures III. 15
through III.17. This will adjust the estimate to on-
site  conditions for various leaf area index levels.
Figures 111.15 through III. 17 represent the relative
reduction in evapotranspiration which occurs for
various reductions in leaf area index. In  a  later
computational step, baseline ET will be multiplied
by the ET modifier coefficient and other factors to
estimate the "adjusted ET."


               ROOTING  DEPTH
           MODIFIER COEFFICIENT

  The hydrologic model, PROSPER, is sensitive to
"rooting depth" (item 15) in that it responds to the
                                                defined soil depth from which soil water can be ex-
                                                tracted. Since PROSPER  is a physically based,
                                                process oriented model, it  integrates the interac-
                                                tion between available soil water (water between
                                                field  capacity and wilting point),  precipitation,
                                                and energy. By altering the specified rooting depth,
                                                one can alter the simulated evapotranspiration.
                                                Rooting depth was altered for various simulations
                                                from average to shallow (half the  average) to deep
                                                (twice the average). It is recognized that all roots
                                                are neither contained in nor draw water from the
                                                upper 1.5, 3, or 6 feet of the soil mantle, and that no
                                                hydrologic model will simulate the true effect of
                                                root distribution under all climatic regimes. What
                                                is simulated by altering "rooting depth" is the
                                                relative response in evapotranspiration to changes
                                                in soil depth or soil water availability.
                                                  In general, annual evapotranspiration decreases
                                                with shallow soil and  increases as soil depth  or
                                                moisture availability increases. Beyond a depth of
                                                6 feet (approximately 10 to 12 inches of available
                                                water),  increasing the depth had  little detectable
                                                effect. Thus, given the precipitation amounts and
     1.0-

      .9-


      .8-

      .7-


      -6'

      .5-

      .4'

      .3-

      .2-
HI
O
O
cc
UJ
                                                             	Fall
                                                             	 Winter
                                                            "_._._._ Spring
                                                             	 Summer
                             10
                                    15         20
                                       LEAF AREA INDEX
25
30
35
40
       Figure 111.15.—Evapotranspiration modifier coefficients, for all seasons, for the Pacific Coast hydrologic
                   provinces—Northwest (5), Continental/Maritime (6), and Central Sierra (7).
                                               m.31

-------
 1.0-
o
o

-------
distribution  for the  station years  simulated by
PROSPER, evapotranspiration occurred at a rate
controlled mostly by available energy once the soil
was 6 to 8 feet deep or moisture availability ex-
ceeded 10 to 12 inches. This does not imply roots do
not go deeper or that they will not extract water
from greater depths, especially  during  drought
years.
  Under dry conditions, moisture availability may
be  limiting in the upper soil layer where the ma-
jority of roots occur. The plant will then depend on
greater proportional extraction  by roots  at much
greater depths.
  The simulations indicated that local variation in
relative rooting depth or depth available for root
penetration alters the evapotranspirational loss, a
fact quantified but not predictable (based on ex-
perience or research). As the relative rooting depth
decreases,  the  available  water  (soil  moisture)
decreases,  thus limiting  evapotranspiration. For
most of the hydrologic regions, the average rooting
depth was considered to be about 3 to 4 feet (6 feet
for the southern Appalachians and Gulf and Atlan-
tic coasts).
  Figures  III. 18,  III. 19,  and   HI.20  depict the
relative adjustment in evapotranspiration that was
simulated  as a function of changing the relative
rooting depth. Average soil depths were established
at  4 feet in  the east (Appalachian  Highlands), 3
feet in the west (Pacific Northwest), and 6 feet in
the south. Shallow soils were considered to be one-
half the average, while deep soils were twice the
average. Beyond 6 feet rooting depth, no significant
effect on  transpiration  with  increasing rooting
depth was produced.
  An  estimate of the average soil  depth for the
silvicultural  prescription unit  and figures III. 18
through 111.20 are needed to estimate the rooting
depth modifier  for the site. This is done for all
prescriptions as the coefficient  is used to further
correct ET for  onsite conditions.
 adjusted  evapotranspiration. Further multiplica-
 tion by the area of the silvicultural state (expressed
 as a decimal percent of the watershed area (item
 9)) area weights the ET. It is entered as item 16 on
 the  worksheets and  is  calculated separately for
 each  silvicultural  state by season,  for  each
 prescription. In the form of an equation:
       = ETg X GET

       X RD X Silvicultural State Area   (IH.4)
where:
  ETA= Site specific seasonal evapotranspiration
         loss for a specified silvicultural activity
         for either the existing or proposed condi-
         tion
  ETB= Seasonal baseline evapotranspiration by
         latitude, if appropriate,  derived from
         either figure 111.10,  IH.ll, or IH.12 (or
         some other source)
  CET = Evapotranspiration modifier coefficient
         taken,  by season, from figures in. 15 —
         III. 17 for a specified leaf area index
Silvicultural  State  Area  =  Area  of  silvi-
         cultural state as a decimal % of watershed
         area
  RD = Rooting depth modifier coefficients, from
         figures III. 18, IE. 19, or ffl.20.
  Figures III.15 to III.17 provide the capability of
estimating evapotranspiration, corrected for  leaf
area index and adjusted, if necessary, for either the
existing or proposed condition. Figures El. 18 to
III.20 provide root depth adjustments.
                      ALL
                SILVICULTURAL
            STATES CONSIDERED
            WEIGHTED ADJUSTED
            EVAPOTRANSPIRATION
  The  calculations  are  now  complete  for  one
silvicultural or vegetal state. The loop is repeated
until all silvicultural states (item 7) are considered
by season.
  Multiplication of baseline ET (item 11) by the
ET modifier coefficient (item 14, which equals 1 for
baseline conditions) and the rooting depth modifier
coefficient (item 15) will yield  an  estimate of the
                      ALL
                   SEASONS
                CONSIDERED?
                                               111.33

-------
   1.1
LU
O
 •1.0
LU
O
O
O
O
cc
    .9
    .8



Sha
1.

.. 	 'x'V~
	 ..••••• ^'
X
X
low Ave

Winter &
Spring ___^_
Fall 	



rage Deep
5- 6'
                                      RELATIVE ROOTING DEPTH

   Figure 111.18.—Root depth modifier coefficients, by season, for the Pacific Coast hydrologic provinces-
                    Northwest (5), Continental/Maritime (6), and Central Sierra (7).
I-
UJ
o
H- 1 1
LU
O
O
I
m 1 0
Q
O
O
or
g






Sha
r
, 	 .,._ Winter A Spring

Fall


. • • ' ' ^ '^ ""
low Ave
!' 4

^~
^ • • *
•^. • • ' * '

'age De
{
x
x'


ep
3'
                                     RELATIVE ROOTING DEPTH
       Figure 111.19.—Root depth modifier coefficients, by season, for the Appalachian Mountains and
                                  Highlands hydrologic regions (2).
  1.2
h-

LU
O
LL

LU
O
O
X
I-
o
o
cc.
   1.0
   .9


"~



Shallow Ave
1.5' :
Fall & Winter 	
Summer & Spring 	


•age De
y e



ep
                                      RELATIVE ROOTING DEPTH
      Figure III.20.—Root depth modifier coefficients, by season, for the Eastern Coastal Plains and
                                 Piedmont hydrologic regions (3).
                                               m.34

-------
  Evapotranspiration calculations are performed
for all silvicultural states by season and for all
seasons by prescription. At this point all the neces-
sary adjustments to ET for differing states for one
season and one watershed prescription have been
made. The loop is repeated until all seasons (item
5) have been considered.
                     ALL
               SILVICULTURAL
              PRESCRIPTIONS
               CONSIDERED?
  At this  point all the calculations  for state by
season for one prescription have been made. The
loop is continued until all prescriptions for the con-
dition are completed.
  The difference between  precipitation  and
evapotranspiration  is  water  available  for
streamflow, assuming soil moisture requirements
are negligible. Water available for streamflow is an
onsite estimate since routing through the soil man-
tle has not been simulated.
  Streamflow, by prescription, is estimated in the
following  manner: adjusted seasonal evapotrans-
piration for each state in the prescription (item 16)
is summed, by season, to yield adjusted seasonal
evapotranspiration (item 17) for the prescription.
Item 17 is subtracted  from the seasonal precipita-
tion (item 10) to yield a seasonal estimate of water
available for streamflow (item 18)  for the prescrip-
tion.  Seasonal values  for both evapotranspiration
(item 17)  and streamflow (item 18) are summed to
estimate annual values  (items 19  and 20).
  If the watershed delineation  consists of only one
prescription, the above values represent watershed
values. If the watershed consists of more than one
prescription,  the  values  will  have to be  area
weighted  and summed over prescription.

              WATER AVAILABLE
          FOR ANNUAL STREAMFLOW

   Worksheets ELI and III.2 are useful in arriving
 at  estimates of ET and streamflow, on a seasonal
 and annual basis, by prescription. Because of the
 variable nature of watershed  division,  no
 worksheets have  been  established  for watershed
 summations. Obviously if the watershed  is con-
sidered  uniform, with only  one  prescription
designation, then the  prescription summary is the
watershed summary.
  If more than one prescription  (or unit) is es-
tablished, they must be summed to get annual flow
using the following relationship:
Qw =
      1
      2
    P=l
(Qpx
Prescription Area (P)
 Watershed Area
                                          (III.5)
 where:
                  Qw
                     = Water available for an-
                       nual streamflow for the
                       entire watershed
                  Qp= Water available for an-
                       nual streamflow for the
                       prescription.
                   i = Number of prescriptions
Prescription Area (P) = Area of prescription (P)
     Watershed Area = Area of entire watershed
  In like manner, the user can substitute the ap-
propriate ET values into the equation to get an es-
timate of watershed ET. By the same token, sum-
mation using seasonal rather than annual values
will yield seasonal summaries.
                      ALL
                  CONDITIONS
                 CONSIDERED?

   The procedure is structured so that evapotran-
 spiration and water available for streamflow for one
 condition must be calculated before evapotran-
 spiration and water available for streamflow for
 another  condition is  calculated. The  procedure
 returns to the "Condition" step until all conditions
 have been considered.
                      END
    Evapotranspiration  and  water  available  for
  streamflow  calculations are complete. Values for
  existing  and  proposed  conditions  have  been
  calculated.  The next step is construction of pre-
  and post-silvicultural activity 7-day flow duration
  curves.
   Examples: Determining Evapotranspiration
              And Water Available
                 For Streamflow

   Using figures III.9a to 111.20, a technique for
 determining pre- and  post-silvicultural  activity
 evapotranspiration losses   has  been  presented.
 Specific examples of the  procedure  follow. The
 item numbers in parentheses  relate  to  column
 numbers in the  appropriate worksheets.
                                               m.35

-------
                                                         WORKSHEET  II 1.1

                     Water  available  for  streamflow  for the existing  condition  In  rainfall  dominated regions
(1}  Watershed  name
                           Bra*\tV\
                                                (2) Hydl
Irologlc region   5     (3) Total prescription  area  (acres)  
-------
                                                          WORKSHEET  II I .2

                      Water  available for  streamflow for  the proposed  condition  In  rainfall  dominated  regions
(1)
    Watershed  name  Meejlfc
(2)  Hydrologlc  region   Ł     (3)  Total  prescription  area  (acres)   #37   (4)  Latitude
Season
name/
dates
(5)
Fall
y-t*
Winter
ty-Ł
Spring
ft-%
Summer
*-&
SI 1 v 1 cu 1 tura prescr 1 pt 1 on
Compartment
(6)
Un 1 mpacted
Impacted
Total for se
Un Impacted
Impacted
Fota 1 for se
Un Impacted
Impacted
Total for se
Un Impacted
Impacted
Sllvlcultural
state
(7)


CI0o.v<.iŁt



ason


Clmvcut



ason


CIcareiA



ason



-------
Example  1. The Needle Branch Watershed
Worksheets III.l and III.2 (Needle Branch)
  In this first  example, for the  Pacific Coast
provinces-low  elevation, Dennis Harr  (personal
communication, 1977) provided data from Needle
Branch of the Alsea Watershed in western Oregon.
The baseline LAI of 40 was reduced to an average of
1 for the  first 3 years after silvicultural activity.
Rooting depth was average (4 feet)  and an aspect
correction was  made (effect  assumed=l) for the
north facing watershed.
  The  first step in the procedure is to estimate the
baseline potential evapotranspiration.
  For the pre-treatment condition [see worksheets
III.l and III.2  (Needle Branch)],  the baseline
evapotranspiration by season (from fig.  III. 10) is
shown in the summary below;  the precipitation
data in the example were taken from the data base
record for the H. J. Andrews Experimental Forest.
It should be noted that the watershed has  been
divided into one silvicultural prescription and one
silvicultural state both  before (forested) and  after
(clearcut) treatment.
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Precipitation
(item 10)
11.6 cm ( 6.5 in)
31.2 cm (12.3 in)
128.1 cm (50.4 in)
82.1 cm (24.4 in)
232.8 cm (91. 6 in)
Baseline ET
(item 11)
26 cm (10.2 in)
24 cm ( 9.5 in)
18 cm ( 7.1 in)
30.5 cm (12 in)
98.5 cm (38. 8 in)
  For the pre-treatment (existing)  condition, the
annual evapotranspiration loss is estimated at 98.5
cm or 38.8 inches. In this example the precipitation
is 91.6 inches, so the water potentially available for
streamflow is 52.8 inches.
  For the post-activity conditions, the following es-
timates are presented:

Season
(item 5)


Summer
Fall
Winter
Spring
Total

Baseline ET
(item 11)

(1)
26 cm
24 cm
18 cm
30.5 cm
98.5 cm

ET
modifier
(item 14)
(2)
0.55
0.54
0.28
0.27

Root
depth
modifier
(item 15)
(3)
1.0
1.0
1.0
1.0

Post-
silvicultural
activity ET
(col 1x2x3)
(4)
14.3 cm
13.0 cm
5.0 cm
8.2 cm
40.5 cm
  The potential  change in evapotranspiration is
98.5 cm minus 40.5 cm or 58.0 cm (22.8 inches) of
potential  increase in flow.  The observed  change
averaged  19.8 inches for the 3-year study  period.
The total  potential flow for the post-activity period
is 52.8 baseline inches and 22.8 inches change or
75.6 inches total.
Example 2. The Coweeta Watershed
Worksheets III.l Am* III.2 (Coweeta)


  For the Appalachian Mountains and Highlands,
Hewlett  and  Douglass  (1968)  reported on  a
management  demonstration  on  a  356-acre
watershed at Coweeta Hydrologic Laboratory near
Franklin, North Carolina. Of the 356 acres, 180
were clearcut, 92 were thinned, and the remainder
left uncut. The expected net change in evapotran-
spiration would be estimated in the following man-
ner.
  Again, the watershed is considered fairly uniform
so  only one  silvicultural  prescription  has been
defined for all 356 acres. For the pre-treatment con-
dition,  this also implies one silvicultural state —
forested. For  the post-treatment condition, three
silvicultural states are implied — forested, thin-
ned, and clearcut.
  For existing conditions, the baseline leaf area in-
dex for hardwoods at Coweeta is about 6 (Swift and
others  1975).  The residual leaf area index on the
clearcut portion was 2, while that on the  thinned
portion  was 3  (Patric and Hewlett, personal com-
munication).  The baseline evapotranspiration, as-
suming a leaf area index of 6 (latitude of 35°) and
using figure III.11, is shown in the summary below:
Season
(item 5)
Summer
Fall
Winter
Spring
Annual
Precipitation
(item 10)
27.0 cm (10.6 in)
23.3 cm ( 9.2 in)
75.2 cm (29.6 in)
60.5 cm (23.8 in)
186.0 cm (73. 2 in)
Baseline ET
(item 11)
39.1 cm (15.4 in)
20.1 cm ( 7.9 in)
8.9 cm ( 3.5 in)
13.0 cm ( 5.1 in)
81.1 cm (31.9in)
                                                       For the  pre-treatment condition,  the annual
                                                     evapotranspiration loss is estimated as 81.1  cm or
                                                     31.9  inches (item 17). The precipitation estimate
                                                     represents the  average  for the simulation  years.
                                                     Therefore, if the estimated evapotranspiration is
                                                     31.9 inches and the precipitation is 73.2 inches, the
                                                     water potentially available for streamflow is 41.3
                                                     inches.
                                                m.38

-------
                                                          WORKSHEET 1 1 I . 1

                      Water available for streamflo* for the existing  condition In rainfall  dominated regions
(1)  Watershed  name
(2)  Hydrologlc region   >L    (3)  Total  prescription area (acres)   3S(o    (4)  Latitude  35
Season
name/
dates
(5)
y - y30
Winter
'V~ V
Spring
fl - s/(,
Summer
Silv
cultura prescription
Compartment
(6)
Un impacted


mpacted

ota

for se
Un Impacted
Impac
Tota
:ted
for se
Un i mpacted


Impacted

Tota

for se
Un impacted
Impacted
Si Ivicultural
state
(7)
FoKsttJ





ason
Forested





ason
Fot-«3t«d





ason
Fov-fffftfld





Total for season
(19) Annua ET
Area
Acres
(8)
3St>





3Sfe
3Sfe





351a
3S*t





3S"fe
9St>






Per-
cent
(9)
l.ooo





1 .000
(.000





1.000
1.000





1.000
(.000





1.000
Precipi-
tation
(cm)
(10)
A3. 3





S3.3
7s. a.





7S-.1,
40. sr





to.s"
a?.o





27.0
Basel ine
ET
(cm)
(11)
30.1






f.V






13.0






37.1






Basal
area
(ft2/ac)
(12)




























Leaf
area
Index
(13)
Ł,






ta






le






If






ET
modifier
coef.
(14)
I.O






I.O






I.O






I.O






Root 1 ng
depth
modifier
coef.
(15)
I.O






I.O






I.O






1.0






Weighted
adjusted
ET
(cm)
(16)
ao. i





10.1
p.?





3.9
13.0





13.0
31.1





31.1
(cm)
Weighted
adjusted
seasonal
ET
(cm)
(17)

10. \

3.9

13.0

31.1

(20) Water available for annual streamflow (cm)
Water
aval lable
for sea-
sonal stream-
flow (cm)
(18)

3.2.

64.3


-------
                                                         WORKSHEET  I I I . 2

                      Water  available for streamflow for the proposed condition  in rainfall dominated regions
(1)  Watershed  name
                                                (2) Hydrologic region   3,      (3) Total prescription area  (acres)   35"4    (4)  Latitude   3S
Season
name/
dates
(5)
fl-V»
Winter
lay V.
7i " «*
Spri ng
3/t'*/3\
Summer
fc/-%'
SI 1 vlcu 1 tura prescr ipt ion
Compartment SI Ivicultural
state
(6) (7)
Un impacted
Impacted
Total for se
Unlmpacted
Impacted
Total for se
Un impacted
Impacted
Total for se
Un imp acted
Impacted
IWiW

Cl«a«ui
TViimtd


ason
F»i-«tei

G«artufc
TVinnfcd


ason
rorest«ei

Cl«axiuŁ
TVmvte.^


ason
RiKstetl

Clcarmt.
"TVnA««fi


Total for season
Area
Acres
(8)
81

1*0
92.


3.Tfc
fl

IfO
90,


3Sfc
8-f

180
92.


3Sfc
?,oo

.feo
.TI



l.oo

.fc?
.J^



Rooting
depth
mod 1 f i er
coef.
(15)
(.0

(.0
1.0



1.0

1-0
1:0



1.0

1,0
1.0



I.O

1.0
I.O



Weighted
adjusted
ET
(cm)
(16)
V.Tt

8.A3

-------
  For  post-treatment conditions,  the estimates
would be as follows:
  (1) For the clearcut portion: leaf area index = 2;
      root depth = average; no aspect adjustment.
      [See  worksheet in.2  (Coweeta).]

Season
(item 5)


Summer
Fall
Winter
Spring
Total

Baseline ET
(item 11)
(fig 111.11)
(1)
39 cm
20 cm
9 cm
13 cm
81 cm
ET
modifier
(item 14)
(fig 111.16)
(2)
0.69
0.81
0.65
0.60

Root
modifier
(item 15)
(fig 111.19)
(3)
1.0
1.0
1.0
1.0

Post-
silvicultural
activity ET
(col 1x2x3)
(4)
26.9 cm
16.2 cm
5.8 cm
7.8 cm
56.7 cm
               The pre-activity (baseline)  annual evapotran-
             spiration was 81 cm  (31.9 in) for the watershed.
             The weighted  post-activity evapotranspiration is
             estimated as 65.1 cm (25.6 in), and the change due
             to the proposed silvicultural activity is 6.3 inches.
             The water potentially available for flow following
             the activity increases 6.3 inches from 41.3 to 47.6
             inches.
               The  observed change in  flow  (Hewlett  and
             Douglass 1968) in the watershed studied was 6.2 in-
             ches. It must be remembered that the leaf area es-
             timates  for the treated sites were based on the
             recollections of the investigators. The estimates
             were  unbiased but arbitrary, and the prediction
             may be better than can be generally expected of the
             technique.
   (2) For the thinned portion: leaf area index = 3;
      root depth =  average; no aspect correction.
      [See worksheet III.2 (Coweeta).]
              Example 3. The Grant Watershed
              Worksheets III.l and III.2 (Grant)
Season
(item 5)
Summer
Fall
Winter
Spring
Total
Baseline ET
(item 11)
(fig. 111.11)
(1)
39
20
9
13
81
ET
modifier
(item 14)
(fig. 111.16)
(2)
0.84
0.90
0.76
0.72
Root Post-
modifier silvicultural
(item 15) activity ET
(fig. 111.19) (col 1x2x3)
(3)
1.0
1.0
1.0
1.0
(4)
32.8cm
18.0cm
6.8cm
9.4cm
67.0cm
   (3) For the managed but uncut portion: poten-
      tial evapotranspiration  is the same as the
      baseline condition.
   To estimate  the  net silvicultural  impact  on
evapotranspiration, the following procedure can be
applied  for either  annual  or seasonal  post-
silvicultural activity effect. It simply weights the
relative effect of each management condition as
shown in the table below:
                For the Gulf and Atlantic region, John Hewlett,
              University of Georgia, (personal communication)
              has supplied data for Example 3. The basin is an
              80-acre treated watershed where silvicultural ac-
              tivities occur on  the Georgia Piedmont, south  of
              Athens,  in  the  Grant  Memorial  Forest.  The
              watershed is a pine-hardwood combination with an
              initial leaf area index of 7 and an average rooting
              depth of about  6  feet.  It was  clearcut,  roller
              chopped  twice, and then planted — reducing the
              leaf area index to 0.5. Again, a single silvicultural
              prescription and one silvicultural state were
              selected  for the  small  uniform basin. The net
              change in evapotranspiration was estimated in the
              following manner [and  transferred  to worksheet
              III.l (Grant)]:
                (1)  Assuming a baseline LAI of 7, the baseline
                    evapotranspiration   by  season  (from fig.
                    ni.12) is tabulated as:
Unit
Clearcut
Thinned
Unmanaged
Acres
(item 8)
180
92
84
Area as
%of
total
(item 9)
50.6
25.8
23.6
Unit potential
evapo-
transpiration
56.7 cm
67.0cm
81.0cm
Weighted unit
evapo-
transpiration
(area % x ET)
28.7 cm
17.3 cm
19.1 cm
   Total
             356
                   100.0
65.1 cm
Season
(item 5)
Summer
Fall
Winter
Spring
Precipitation
(item 10)
41.2 cm (16.2 in)
30.2 cm (11. 9 in)
40.3 cm (15.9 in)
20.6 cm ( 8.1 in)
Baseline ET
(item 11)
32.1 cm (12.6 in)
24.9 cm ( 9.8 in)
11.4 cm ( 4.5 in)
23.7 cm ( 9.3 in)
                                                       Total
                                                                    132.3 cm (52.1 in)    92.1 cm (36.2 in)
                                               111.41

-------
                                                         WORKSHEET  I I  I . 1

                      Water available for streamflow for the existing condition  In rainfall dominated regions
(I)
    Watershed  name   6t
Winter
Ml 1.1
7\- A*
Spring
*-%•
Sunnier
*-%
Silviculture prescription
Compartment
(6)
Un Impacted
Impacted
[otal for se
Un Imp acted
Impacted
total for se
Un 1 mpacted
Impacted
Total for se
Un Imp acted
Impacted
SI Ivlcultural
state
(7)
Fn-«ri*i





ason
FbwsUxl





ason
fijvciteJ





ason
MJI tf&tu





Total for season
Area
Acres
(8)
So





SO
16





80
So





So
ffo





80
Per-
cent
(9)
I.OOO





1 .000
1.000





1 .000
I.OOO





1.000
I.OOO





I.OOO
Prec 1 p 1 -
tat ion
(cm)
(10)
30. JL





30.4,
$0.3





.3
ao.fc





ao.t
fl.SL






-------
                                                          WORKSHEET  II I .2

                      Water available for streamflow for the proposed  condition  In  rainfall  dominated regions


(1)  Watershed  name  Gwurit  4J.
               (2) Hydrologlc region  3     (3) Total prescription area (acres)   SO    (4) Latitude
Season
dates
(5)
V'/*>
Winter
•V-&
Spring
3/r%
Summer
X'S/3,
S i 1 v 1 cu 1 tura 1 prescr 1 pt 1 on
Compartment
(6)
Un impacted
Impacted
Total for se
Un Impacted
Impacted
Total for se
Un impacted
Impacted
Tota 1 for se
Un impacted
Impacted
Si Ivlcultural
state
(7)


Cl»a.«ut



ason


Clcueut



ason


Cl«a«u*



ason


"hw-ntfi



Tota 1 for season
Area
Acres
(6)


10



»o


80



JO


ac



So


80



SO
Per-
cent
(9)


1 ooo



1.000


I.Ooo



1 .000


1.000



t.ooo


I.OOO



1.000
Precipi-
tation
(cm)
(10)


3O. X



3o.i



-------
  (2) For post-silvicultural activity conditions [see
      worksheet HI.2 (Grant)], with a LAI = .5, the
      estimates are tabulated as:
Season  Baseline ET
(itemS)   (item 11)
         (fig 111.12)
            ET       Root       Post-
          modifier   modifier  silviculture!
          (Item 14)   (Item 15)   activity ET
          (fig 111.17)   (figlll.20)  (col 1x2x3)
Summer
Fall
Winter
Spring

 Total
32.1 cm
24.9 cm
11.4 cm
23.7 cm

92.1 cm
.47
.47
.41
.34
1.0
1.0
1.0
1.0
15.1 cm
11.7 cm
 4.7 cm
 8.0 cm

39.5 cm
   For  the pre-treatment  condition,  the  annual
 evapotranspiration loss is estimated as 36.2 inches
 (92.1 cm) from an average precipitation of 52.1 in-
 ches (132.3 cm). The water potentially available for
 streamflow is  15.9 inches (40.4 cm).

  The potential change in flow based on changes in
evapotranspiration  from 92.1  cm  (existing  con-
dition)  to 39.5 cm (proposed condition) is 52.6 cm
(20.7 in). Hewlett estimated the observed change
at 11 inches by the paired watershed method. The
simulated water available for streamflow increased
from 15.9 to 36.6 inches.
                                                m.44

-------
    PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
                 IN STREAMFLOW (STREAMFLOW ESTIMATION)
                            (RAIN DOMINATED REGIONS)
                 APPALACHIAN MOUNTAINS AND HIGHLANDS (REGION 2)
            GULF AND ATLANTIC COASTAL PLAIN AND PIEDMONT (REGION 3)
                       PACIFIC COAST REGIONS (PROVINCES 5, 6, 7)
  Distributing the potential changes in streamflow
associated with various silvicultural  activities is
more complex and contains more sources of error
than does estimating evapotranspiration and the
magnitude of change. Streamflow predictions not
only contain  all the  errors inherent in  the
evapotranspiration predictions, but also those er-
rors inherent in maintaining a  time-and-space-
variable soil water budget and  in routing both
saturated and  unsaturated flows to the channel
system.  None  of these  factors involving routing
have been simulated in this effort. Therefore, all
calculations dealing with flow predictions deal with
estimating the  water onsite  that  is potentially
available for streamflow.
  The purpose of this procedure is to distribute the
expected change in  flow,  as estimated by the
preceding ET procedure, over some reasonable es-
timate of the  baseline or pre-treatment flow
regime.
  It has already been noted that the objective is to
estimate the streamflow change and  not the ab-
solute value. Numerous simulations were made for
each watershed data  set to determine the effect of
altering various watershed parameters and cover
conditions on potential streamflow. The complex-
ity of the data generated is  significant because
simulations were made on five to six cover condi-
tions,  three soil depths, two aspects,  and several
latitudes (watersheds) for each region. To facilitate
presentation of the results, a least squares tech-
nique was used to fit the model wherein the change
in flow (AQ) that occurs is a function of the antece-
dent flow level (pre-silvicultural activity flow, Q;),
the reduction in leaf area index (CD), the aspect
(AS), the rooting or soil depth (RD).
  The technique is not, however, a true regression,
and estimates of error are impossible since the data
base is simulated. The  least squares  model does
represent the relationship that existed between the
change in flow and the various levels of the other
parameters used in the simulations.
       PROCEDURAL FLOW CHART
  A flow chart for the suggested methodology of
calculating potential changes in streamflow as-
sociated with silvicultural practices is presented in
figure 111.21.
  At the end of this section are  three examples
which  have been developed  to demonstrate ap-
plication of the methodology; the worksheets for
each example  (in.3 and III.4) are summaries of
calculations performed. A detailed description for
each step follows.
          HYDROLOGIC REGION OR
                 PROVINCE
  Decide which region or province most nearly ap-
proximates the hydrologic  regime for the water-
shed of interest. Streamflow calculations are based
upon  regional  hydrologic  relationships,  and the
regional  characterization  is  the same  for this
procedure as it was for the ET procedure.
                  ANNUAL
               HYDROGRAPH
                AVAILABLE?
  To distribute the expected changes in flow,  it
must be known if a representative hydrograph  is
available for  the  site. If not,  the methodology
presented includes a flow duration curve represen-
                                            HI.45

-------
                            (   Hydrologic Region or Province   j
                                           Hydro-
                                           graph
                                         Available?
  Spe-
cific Flow
 Changes
 Desired?
              Yes
(  Flow and Date of Interest
              +
          Sine Day
                                                          Regional 7-Day Flow
                                                            Duration Curve
                                                          Water Available for
                                                          Annual Streamflow-
                                                          Existing Condition
                                                           Adjustment Ratio
                               Existing Condition 7-Day
                                  Flow Duration Curve
  Leaf Area Index Reduction
                               Leaf Area Index Reduction
            Aspect
                                        Aspect
    Relative Rooting Depth
                                 Relative Rooting Depth
     Change in Streamflow
                                 Change in Streamflow
                                                       Proposed Condition 7-Day
                                                          Flow Duration Curve
     Figure 111.21.—Flow chart of methodology for determining 7-day flow duration curve and change
              in Streamflow for specific flow change for rainfall dominated regions.
                                      m.46

-------
tative of each region over which changes in flow can
be distributed. If a site specific hydrograph is not
available, proceed to the block "Regional 7-Day
Flow Duration  Curves."  If a  representative
hydrograph  is available, proceed to the block
"Specific Flow Changes Desired?"
                   SPECIFIC
               FLOW CHANGES
                   DESIRED?
   If a site specific hydrograph is available, there
 are two options.  First, a determination of the ex-
 pected change in flow for specific flow levels as a
 function of the day or time of year when the flow
level might occur can be performed. This would ap-
ply when concerned with impacts on in-stream flow
needs or on temperature. Changes in specific flow
levels do not replace the procedure for distributing
annual  changes; it is another analytical tool. In
most  applications  interest will be in distributing
the  change  in annual flow  over  the  entire
hydrograph. (This  constitutes a  "no" answer.) In
this case, proceed to the section on "Existing Con-
dition 7-Day Flow Duration Curve" since a site
specific  flow duration curve can be constructed
from  the hydrograph. If estimates of changes in
specific  flow levels  only are desired, proceed to the
"Flow and Date of Interest" section.
           REGIONAL 7-DAY FLOW
              DURATION CURVE
      20.
      15
   .
   o>
   o>

   o

   O
   in
   O
   <
   DC
   UU
      10
—
—
—
—
—
	
—
—
—



•
\
[••! \
\
\ ^
V
\v
Vj_- -







\
-••-^




ANNUAL FLOW E
Appalachian Moi
Eastern Coastal (
Pacific Coast
	 Easl


^••=H7vT




3Y INTEGRATION O
ntains & Highlands
3lain & Piedmont
fie Coast
ern Coastal Plain &
alachian Mountain I

s*=^




F11 POINTS
72.0 cm
75 1r.m 	
139.6cm
Piedmont
i Highlands



                           20              40              60              80

                        PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
             Figure III.22.—Potential excess water available for streamflow, 7-day flow duration curve for the
               Pacific Coast hydrologic provinces—Northwest  (5), Continental/Maritime (6), and  Central
               Sierra (7); for Appalachian Mountains and Highlands hydrologic region (2); and for the Eastern
               Coastal Plain and Piedmont hydrologic region (3).
                                         100
                                               m.47

-------
  Figure III.22 represents distributions of water
potentially available for streamflow for each of the
regions presented as 7-day flow duration curves. As
such, they represent the average expected 7-day
flow distribution for the conditions under which the
simulations for each region were made.  The major
problem with presenting a normalized  flow dura-
tion curve is that the normal variation in climatic,
physiographic,  and local  basin  characteristics
forces almost every annual distribution of flow to
be unique in both time and space. The assumption
made at this point is that a site specific curve is not
available. Therefore, select the duration curve for
the region and adjust it for site specific conditions.
      WATER AVAILABLE FOR ANNUAL
    STREAMFLOW—EXISTING CONDITION
  The flow duration curves presented in figure
III.22  represent  average  distributions  for  the
watershed years simulated in each region. As such,
they represent the distribution of a specific volume
of water for each region and that volume may or
may not represent the expected flow from the site;
an adjustment is therefore necessary. The expected
flow from the site for either baseline  or existing
condition has  already been  calculated  in  the
procedure  for   determining evapotranspiration.
Now the given flow duration curve (from fig. III.22)
must be scaled to  reflect the expected flow. This
would not be necessary if a site specific flow dura-
tion curve were available.
             ADJUSTMENT RATIO
  The  baseline potential flow duration curve  for
the hydrologic region must be adjusted for the site
specific existing condition. This is done through
multiplication of selected points on the curve by
adjustment ratio. The adjustment ratio is defined
as  the ratio  of  water  available for annual
streamflow estimated by the ET procedure  to the
total water available for streamflow represented by
the 7-day flow duration curve for  the  hydrologic
region  (fig. III.22) expressed as:
where
  AR
  Qw
          adjustment ratio
          water available  for annual  streamflow
          for  the existing condition  (from  ET
          calculation, Eq.  ni.5)
  QR  = total  water  available  for  streamflow
          represented by the  regional  7-day flow
          duration curve, (fig III.22)
  For Coweeta, for example, the adjustment ratio
             AR =
                     104.9
                      72.0
= 1.457
where:
  104.9 cm
                  AR =
                         QR
                                         (III.6)
               water  available   for  annual
               streamflow for the existing condi-
               tion
   72.0 cm  = total  water  available  for
               streamflow represented  by the
               regional 7-day flow duration curve
               (from fig. 111.22).

  Once the adjustment ratio is determined, a site
specific flow duration curve for the existing condi-
tion can be constructed.
         EXISTING CONDITION 7-DAY
           FLOW DURATION CURVE
  If a site specific 7-day flow duration curve for the
existing condition is available, no  adjustment is
necessary here. However, flow duration curves from
figure III.22 need to be adjusted in the following
manner.  An acceptable number of points on the
regional 7-day flow duration curve (fig. in.22) must
be selected such that a new line can be fitted after
adjusting the  points for site specific  conditions.
(For example,  11  points at  10  percent intervals
such as from 0 to 100 percent may be chosen.) The
discharge (Qj^)  for each point (i) chosen from the
regional 7-day flow duration curve is multiplied by
the adjustment ratio to give an adjusted flow level
(Qi). For example.

              Qi=QR.XAR               (III7)
where:
  Qi  =  adjusted flow level
  QR. =  the  discharge for each point (i) on the
         regional 7-day flow  duration curve
  AR =  adjustment ratio
                                               III.48

-------
  The existing condition 7-day flow duration curve
is the plot of adjusted flow levels (Qi) versus the
corresponding percent of time the flow is equaled or
exceeded.
  See worksheets IE.3 (Needle Branch, Coweeta,
Grant) for detailed examples of determining the ex-
isting condition 7-day flow duration curve.
  To this point, site specific estimates of the 7-day
flow duration curve for baseline or existing condi-
tions have been made. If a change in vegetal state is
proposed,  the  following   sections   describe  the
procedures necessary to modify the existing flow
duration curve to reflect the impact of the vegeta-
tion change.
  In order to calculate the change  in streamflow
due to the change from existing to proposed condi-
tions, it is necessary to estimate the leaf area index
reduction, aspect,  and relative rooting depth.
              LEAF AREA INDEX
                 REDUCTION
where:
  RD =  relative rooting depth for watershed
  RDW=  rooting depth for watershed
  RDA=  average rooting depth for region
  The average regional rooting depth has been dis-
cussed in a previous section.
                 CHANGE IN
                STREAMFLOW
  As noted earlier, the expected change in annual
flow is a reflection of changes in evapotranspiration
resulting from the average change in leaf area index
for the watershed. This section deals with the dis-
tribution of that change in flow over the annual dis-
tribution or the flow duration curve. This is done
using least square techniques.
                                                     AQ; = ho + biQ; + b2CD + b3AS + b4 RD  (HI.9)
  A representative value for the reduction of leaf
area index (LAI) in units of LAI due to vegetation
changes between existing and proposed conditions
must be supplied. Reduction in LAI is symbolized
as "CD." As indicated previously, basal area can
be used to estimate leaf area index.
                   ASPECT
  A representative aspect for the watershed  or
watershed subunit in coded form must be supplied.
The aspect code is as follows: North aspect = — 1,
south aspect = +1, east or west aspect = 0.
  where:
  AQ;  = simulated  potential  change  in  water
          available for streamflow
    Qi  = simulated potential water available for
          streamflow  under  baseline  or un-
          disturbed conditions (cm/week)
    CD  = the reduction in leaf area index (in units
          of LAI) from baseline
    AS  = dummy variable for aspect (—1 for north
          slopes, +1 for south slopes, 0 for east or
          west slopes)
    RD  = relative rooting depth
    bj   = least squares coefficient
    The coefficients (tables III.3, HI.4, and HI.5) for
  the regional least square models  are as follow:
          RELATIVE ROOTING DEPTH
   Relative rooting depth (RD) for the region is sup-
 plied. It is calculated as:
                                          (m.8)
    Table III.3.—Least square coefficients for equation III.9
     for simulated potential change in water available for
         streamflow for the Pacific Coast provinces
                         RD
Variable
Intercept
Qi
CD
AS
RD
Coefficient
bo
bi
bz
bs
b4
Estimated
coefficients
-0.05
-0.05
0.025
0.013
0.006
                                               m.49

-------
   Table 111.4.—Least square coefficients for equation 111.9
    for simulated potential change in water available for
  streamflow for the Appalachian Mountains and Highlands
 Variable
                    Coefficient
 Estimated
coefficients
 Intercept
 Qi
 CD
 AS
 RD
                       bo
                       bi
                       b:
  -0.03
  -0.03
  0.13
  0.02
  0.03
   Table III.5.—Least square coefficients for equation III.9 for
  simulated potential change in water avilable for streamflow
             for the Coastal Plain/Piedmont
  Variable
                    Coefficient
 Estimated
 coefficients
  Intercept
  Qi
  CD
  AS
  RD
                        bo
                                       -.19
                                       -.12
                                        .20
                                        .01
                                        .02
   Addition of the potential change for streamflow
 for interval i (AQ;) to the existing streamflow for
 interval  i (Q;)  will yield the  post-treatment
 potential streamflow for interval i ( Q; + AQ;).
   The average 7-day potential flow for the existing
 condition can be estimated from the flow duration
 curve using the equation:
                        N-l
Qaverage = [^(Qx + QN) +  2  Q;l X -LQQ-
         L              i=2    J    N-l
                                         (111.10)
                             10
or for N  = 11 points:
           r                 A"      -,
 Average =   -5(Ql + Qn) +   2    Q.   X  .
                           i=2      J
                                          10
The same applies to the post-treatment condition
flows (Qi+AQj).
  Examples of calculations have been worked out
and presented  in worksheets HL3 and IE.4. The
output from the calculations is an estimate of water
available for streamflow distributed over time.
  The least squares method is one of two methods
for  estimating  increase  in  streamflow  due  to
silvicultural activity. The other method involves
computing the difference in water  available for
streamflow between  existing and proposed condi-
tions using evapotranspiration calculations; i.e.,
subtraction of item (20), worksheet ELI from item
(20), worksheet m.2  will accomplish this.
  An estimate of the  change in flow using the least
squares method  can be made as  follows. The
average 7-day flow for either pre- or post-treatment
condition can be estimated from the respective flow
duration curves using equation IIL9 or ni.10. The
average 7-day flow, when multiplied by 52, yields
the average annual flow. The same  applies to the
post-treatment condition flows  ( Q;+ AQ; ). The
difference in the two is also an estimate of the ex-
pected change in flow resulting from the proposed
activity; it will compare with, but not be the same
as,  the  estimates  using the evapotranspiration
calculations.
        PROPOSED CONDITION 7-DAY
           FLOW DURATION CURVE
                   The proposed condition  7-day flow duration
                 curve is  a plot of each adjusted flow level (Q; +
                 AQ;) versus percent of time that flow (Q;+ AQj) is
                 equaled or exceeded.
                   The primary purpose of this methodology is to
                 provide 7-day flow duration  curves for conditions
                 before and after a proposed  silvicultural activity.
                 At this point, sufficient instruction has been given
                 to enable construction  of existing and proposed
                 flow duration curves.  The next step, after plotting
                 the flow duration curves, would be to proceed to the
                 subsequent  procedural  chapters.  However,  if
                 changes in streamflow for a  specific date or for a
                 specific flow level are required,  the  descriptions
                 that follow outline the procedure for their estima-
                 tion.
                   If an evaluation of  the effect of time of year on
                 changes in various flow levels is not needed, the
                 analysis  is now  complete.  If estimates of time
                 dependent changes are necessary, the analysis con-
                 tinues.

                   It should be noted that the  procedure distributes
                 the impact of average vegetal changes over  the
                 average watershed flow duration curve. The ET es-
                 timations made  previously were not  lumped  but
                 were  actually  calculated  by  treatment  and
                 prescription;  they were then  area weighted to ob-
                 tain the net annual change. This is not true of the
                 flow distribution procedure  because it tends to
                 lump the various treatments and prescriptions into
                 a single watershed average, as the methodology is
                 strongest when applied in this manner. However,
                 the method is flexible; if separate evaluations of
                 each treatment or prescription are desired, they
                 can be determined and the relative effect of each
                 component can be evaluated  in the same manner.
                                               HI.50

-------
This depends on the objectives defined and the
resolution desired.
                 LEAF AREA
              INDEX REDUCTION
        FLOW AND DATE OF INTEREST
  An estimate of the reduction in leaf area index is
required as defined for equation HI.9.
  If an annual hydrograph for the existing condi-
tion is  available and/or  if changes in flow for
specific flow levels as functions  of date of occur-
rence are desired, time dependent adjustments can
be made to reflect the effect of silvicultural activity
using the  following least squares model:

AQi=b0+b1Qi+b2CD

    + CD + b3AS +b4RD + b5 Sine Day  (in.ll)

With the exception of sine  day, all variables are as
defined in equation III.9.

                  SINE DAY

  In addition to fitting equation III. 9 for use in ad-
justing the potential flow  duration curve, an ad-
ditional parameter was fitted for  adjusting the an-
nual  hydrograph. Hewlett and others (1977),
Hewlett and Hibbert (1967) and others have found
that the sine of the day (sine of the numerical day
in the year starting  with  December 21 as day 1,
January 1 as day 11 and  so on) is  useful in express-
ing the annual cycle  of hydrologic processes.
 Sine Day =  sin f 360 X Day #  | + 2     (m.l2)
                I      365     J
 Values of sine day for selected days may be found
 in table III.6.
                   ASPECT
  An estimate of aspect is required as defined in
equation in.9.
          RELATIVE ROOTING DEPTH
  An estimate of relative rooting depth is required
as defined in equation m.9.

                 CHANGE IN
                STREAMFLOW
  Equation III.11 is used to estimate the change in
streamflow  caused by  silvicultural activity for
specific levels or dates.
  The estimated coefficients for equation HI. 11 by
regions may be found in tables III.7, ffl.8, or in.9.
  Addition  of the change  in streamflow for  a
hydrograph flow or date i (AQ;) to the hydrograph
streamflow value  for flow or date i  (Qj) gives
hydrograph streamflow  value  (Q;+ AQ;) for the
proposed condition at flow or date i.
                      Table 111.6.—Sine of day value (S) for use with flow prediction equation
                                111.11. Where S = sin (360 x day #/365) + 2
Day
1
7
14
21
28
Dec
1.66
1.76
1.88
2.00
2.12
Jan
2.17
2.27
2.39
2.49
2.59
Feb
2.65
2.72
2.80
2.87
2.92
Mar
2.94
2.98
2.99
3.00
2.99
Apr
2.99
2.97
2.93
2.88
2.82
May
2.77
2.70
2.61
2.52
2.41
Jun
2.36
2.26
2.15
2.03
1.90
Jul
1.84
1.74
1.62
1.51
1.43
Aug
1.37
1.29
1.21
1.14
1.09
Sep
1.06
1.03
1.01
1.00
1.01
Oct
1.01
1.04
1.08
1.13
1.20
Nov
1.23
1.30
1.39
1.49
1.60
                                               m.5i

-------
 Table III.?.—Least square coefficients for equation 111.11
      for the Pacific Coast provinces-low elevation
Parameter
Intercept
QI
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
b>
bs
b«
b>
Estimated coefficient
value
0.21
-0.16
0.02
0.001
0.05
0.91
  Table III.8.—Least square coefficients for equation 111.11
      for the Appalachian Mountains and Highlands
Parameter
Intercept
Qi
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
bt
bi
b4
b.
Estimated coefficient
value
-0.08
0.01
0.13
0.04
0.02
1.17
Table III.9.—Least square coefficients for equation 111.11 for the
              Coastal Plain/Piedmont
Parameter
Intercept
Qi
CD
AS
RD
Sine day
Coefficient
symbol
bo
bi
b2
bs
b4
be
Estimated coefficient
value
-0.19
0.13
0.20
0.01
0.02
-0.18
             The equation (HI.11) allows the adjustment of
           specific flow levels (Q;) as a function of the time of
           occurrence. For example, the effect of treatment on
           a 2 cm flow level in March would not necessarily be
           the same as the  effect of treatment on the same
           flow level if it were  to occur in August.

          Examples: Determining Potential Changes In
                            Streamflow
            An  illustration  of  the calculations has  been
          worked out and is presented in worksheets III.3 and
          III.4. The example uses the regional potential flow
          duration curve and adjusts it for annual streamflow
          estimated in the evapotranspiration calculation for
          Needle Branch watershed previously presented (fig
          m.22a).
            Output from the calculations (wkshts. HI.3 and
          ni.4) is an estimate of water available for annual
          streamflow distributed  over time. Both existing
          and proposed condition levels are expressed as 7-
          day average flow in cubic feet per second. These
          values are  then entered on the worksheets for sedi-
          ment analysis  presented in chapter VI.
            Similar  examples  have  been completed  on
          worksheets in.3 and III.4 for Coweeta (plotted on
          fig. ni.22b) representing the Appalachian Moun-
          tains  and Highlands  and  for  Grant Memorial
          Forest (fig. in.22c) representing the Coastal Plain/
          Piedmont.
            The  following summary  compares  the evapo-
          transpiration method and the least squares method
          to observed values for  the three watersheds used in
          the evapotranspiration estimation procedure.
                  Table 111.10.—A comparison (cm) of the evapotranspiration method and the least
                      squares method to measured values for the three watershed examples
               Watershed
                                       ET method
           Streamflow increases-
            Least squares method
                                                                              Observed
               Needle Branch
               Coweeta
               Grant WS#1
58.0
15.9
52.6
41.5
15.0
54.5
50.3'
15.82
28.03
                 'Harr, D., personal communication.
                 'Hewlett and Douglass (1968).
                 'Hewlett, J., University of Georgia, personal communication.
                                               m.52

-------
                                WORKSHEET I I I .3

                  Flow duration curve for existing condition
                            rain dominated regions
(1)  Watershed name
fJeeqle
                                             (2) Hydrologic region
(3) Water available for annual  streamflow existing condition (cm)

(4) Annual  flow from duration curve for hydrologic region (cm)    I3?.4>

(5) Adjustment ratio (3)/(4)
Point
number
i
(6)
/
z
3
4
5-
k>
7
t
9
10
//

Percent of
t i me f 1 ow
is equaled
or exceeded
(7)
0
10
ao
30
W
s-o
&o
10
80
JO
|00

Regional
flow
(cm/7 days)
(8)
is-.r
10
SO
4.0
/.3
/./s-
•75-
.50
.as-
.IS"
o

Existing
potential
flow Q;
(cm/7 days)
(9)
/4.?
7-7
V.8
/.?
/.3
/./
7
.5"
.a,
.1
0

Existing
potential
flow QJ
(cfs)
(10)
8.3
^
3.7
/./
.7
.&
.1
.3
.1
.06
0

Col.  No.                                 Notes
  (1)   Identification of watershed or watershed subunit.
  (2)   Descriptions of hydrologic regions and provinces are given in text.
  (3)   Item (20)  of worksheet I I 1.1.
  (4)   From figure I I I.22.
  (5)   Item (3)  T item (4).
  (6)   Number  of  each  point  taken from figure 111.22; or user supplied.
  (7)   X-axis  of  figure I I 1.22.
  (8)   From figure 111.22; or user supplied (unnecessary if col. (9) is user
        supplied).
  (9)   Column  (8) x item (5); or  user supplied.
 (10)   Column  (9) x area (acres)  x 0.002363.
                                    III. 53

-------
                                                                WORKSHEET  II I.4
                                                  Flow  duration curve  for proposed condition
                                             rain  dominated  regions—annual hydrograph unavailable
      (1)  Watershed name
                                              (2)  Hydrologic region
      (4) Existing condition LAI
                          	  (5)  Proposed  condition LAI	.

(7)  Rooting depth modifier coefficient (RD)   j     (8) bp  ".OS"   (9)
                (3)  Watershed aspect code (AS)

              (6) Change in LAI  (CD)     3?
                                                                                                                         1
                                                                              -.OS    (10) b2  -035"  (ID b3 -Ql3    (12) b4  .OO&>
Point
number
i
(13)
/
a.
3
4
s
(a
7
&
f
10
II

Percent of
time flow is
equaled or
exceeded
(14)
0
10
AC
30
to
So
60
70
So
10
JOO

Exi sti ng
potential
flow QJ
(15)
N.7
7.7
4.8
/.?
/.3
/.I
.7
.r
-i
.1
0

bQ
(16)
-.OS
-.of
-.OS"
-.oS"
-.OS"
-.OS"
-.OS"
-.oS"
-.OS"
-.05-
-.off

blOj
(17)
-.75-
-.3?
-.a«/
-.10
-.07
-.ot
-.o«*
-.03
-.01
-.01
o

b2CD
(18)
• ?7S-
.?7S"
.175"
MS"
975"
.975-
.975"
.975"
.975-
.9?r
.975-

b3AS
(19)
-.013
-.013
-.013
-.013
-.0)3
-.013
-.0)3
-.013
-.OI3
- OI3
-.O»3

b4RD
(20)
.006,
.004
.006
.006
.004,
.6
.004
.006
.006
006
.OO (a

Of
(cm)
(21)
.18
.54
.fc?
.83
.*(,
.«7
.Ł9
.90
.92.
.91
.93

Oi +AQj
(cm)
(22)
IS.)
S.I,
SS"
a.7
ia
a.o
,fc
/.
-------
                                WORKSHEET I I I .3

                  Flow duration curve for existing condition
                            rain dominated regions
(1) Watershed name
                                             (2)  Hydro logic region
(3)  Water  available  for  annual  streamflow existing  condition  (cm)

(4)  Annual  flow from duration curve for hydrologic  region  (cm)	

(5)  Adjustment  ratio (3)/(4)    |.^S7	
                                                                   /QV.9
                                                                   73.0
Point
number
i
(6)
/
I
3
4
s
1e
1
8
?
10
II

Percent of
time flow
is equaled
or exceeded
(7)
0
10
30
30
40
so
60
70
SO
70
|00

Regional
flow
(cm/7 days)
(8)
?.0
a.7
/.?
14
l^
.7
.r
-V
.3
.a,
o

Existing
potent! al
flow QJ
(cm/7 days)
(9)
13 J
3.?
*.*
1.0
/.*
/.o
•7
,6
.V
.3
O

Existing
potential
flow QJ
(cfs)
(10)
11.0
3.Z
M
/7
AS"
.?
.6,
.r
.3
.as^
o

Col.  No.                                 Notes
  (1)   Identification of watershed or watershed subunit.
  (2)   Descriptions of hydrologic regions and provinces are given in text.
  (3)   Item (20).of worksheet I I 1.1.
  (4)   From figure 11 1.22.
  (5)   Item (3)  T item (4).
  (6)   Number of each point  taken from figure 111.22; or user supplied.
  (7)   X-axis of figure I I 1.22.
  (8)   From figure 111.22; or user supplied (unnecessary if col. (9) is user
        supplied).
  (9)   Column (8) x item (5); or  user supplied.
 (10)   Column (9) x area (acres)  x 0.002363.
                                      m.55

-------
                                                               WORKSHEET I I I.4
      ! 1) Watershed name
                    Cotoceto.
                                                 Flow duration curve for proposed condition
                                            rain dominated regions—annual  hydrograph unavailable
(2)  Hydrologic  region
                                            (5) Proposed condition LAI    3-
  (3)  Watershed  aspect  code  (AS)_

(6)  Change in  LAI  (CD)    3.8
                                                                                                                        0
(4)  Existing  condition  LAI   (p.Q _

(7)  Rooting depth modifier  coefficient (RD)   J     (8)  bp  '.03    (9)  b i  -.03    (10)  b2  «J3     (11)  53
                                                                                                                      (12) b4
Point
number
i
(13)
/
JL
3
V
5

-------
                                WORKSHEET I I I .3

                  Flow duration curve for existing condition
                            rain dominated regions
(1)  Watershed name
Grt
-------
                                                               WORKSHEET  I I I .4
                                                 Flow duration curve for proposed condition
                                            rain dominated regions—annual hydrograph unavailable
(1)  Watershed name
                                                    (2) Hydrologic region
  (3)  Watershed aspect code (AS)_

(6)  Change in LAI  (CD)     b.S"
     (4) Existing condition LAI   7.O        (5) Proposed condition LAI    .   "

     (7) Rooting depth modifier coefficient  (RD)   /     (8) bp -.1?     (9) t>i -. |Cb   (10) b2  .90    (11) 63   . 0 1    (12)
Point
number
i
(13)
1
X
3
V
Ł•
&
7
8
9
(0
II

Percent of
time flow is
equaled or
exceeded
(14)
0
10
ao
30
V°
so
t>0
70
KO
10
100

Existing
potential
flow Q-t
(15)
fc.7
J.O
.7
.6
.5"
.5"
.0
(16)
-.19
-.if
-.1?
-.19
-.19
-.19
-.19
-.19
-.19
-.19
-.1?

blQj
(17)
-.W
-.12.
-.0?
-.07
-.Ofe
-.0&
-.OS'
-.0
/.07
/.o?
AO*
/.09
l.ll
1.12.
1.13

9i + AQj
(cm)
(22)
7.0
40
/.*
1.7
l.t,
U
I.S
l.f
/.3
/.a.
/./

Ql + AQi
(cfs)
(23)
1.3
.V
• 3M
.31.
.30
.•So
.as
.a4>
.as-
.S3
.AI

ss
Item
Col.
(1)
(2)

(3)

(4)
(5)
(6)
(7)
(8)-
(12)
or
No. Notes
Identification of watershed or watershed subunit.
Descriptions of hydrologic regions and provinces gi
in the text.
Northern aspect = +1 , southern aspect = -1 , eastern
western aspect = 0.
Area weighted average for existing condition.
Area weighted average for proposed condition.
Item (4) - item (5).
Area weighted average.
From tables 1 1 1 .3 to 1 1 1 .5.




ven

or







                                                                       Item or
                                                                       Co I. No.
                                                                                              Notes
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
Column (6) of worksheet II
Column (7) of worksheet II
Column (9) of worksheet II
Item (8).
Item (9) x column (15) .
Item (10) x item (6).
Item (11 ) x item (3).
Item (12) x item (7).
Columns (16) + (17) + (18)
Column (15) + column (21 ).
Column (22) x area (ac) x
1 .3.
1.3.
1 .3.





+ (19) +

0.002363
                                                                                                                   (20),
                                                                                                                  for 7-day intervals.

-------
  16-
  14-
  12-
i
•o
LL
UU
Ł  6-
                         r^ Post- treatment
                        ^	
                       20                40                60                80
                         PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
100
            Figure lll.22a.—Pre- and post-silviculture! activity 7-day flow duration curve for Needle Branch.
                                               m.59

-------
           20                40                60                80
              PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
100
Figure lll.22b.—Pro- and post-silvicuKural activity 7-day (low duration curve for Coweeta.
                                   ni.eo

-------
        0             20            40            60            80

              PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
                                                                          100
Figure lll.22c.—Pro- and post-sllviculUiral activity 7-day (low duration curve for Grant Memorial
                                Forest Watershed.
                                   ni.ei

-------
  PROCEDURAL DESCRIPTION: DETERMINING EVAPOTRANSPIRATION
AND  WATER AVAILABLE FOR STREAMFLOW  (ET ESTIMATION)  (SNOW
                               DOMINATED REGIONS)
                          NEW ENGLAND/LAKE STATES (REGION 1)
                  ROCKY MOUNTAIN/INLAND INTERMOUNTAIN (REGION 4)
         PACIFIC COAST REGION, HIGHER ELEVATION ZONES (PROVINCES 5, 6, 7)
  The  following  methodology  is presented  as  a
means of estimating evapotranspiration and poten-
tial streamflow for existing and proposed condi-
tions in snow dominated hydrologic regions.
  In this handbook, the areas in which snow has a
significant hydrologic  role  are the New
England/Lake States hydrologic region  (1),  the
Rocky Mountain/Inland Intermountain hydrologic
region  (4), and the higher elevation zones of the
Pacific Coast hydrologic provinces  (5, 6, and 7).
These areas are shown in figure HI.9a. It is unfor-
tunate  that for purposes of delineation the higher
and lower elevations of the Pacific Coast provinces
are separated, since  hydrologically they are  so
closely interlocked. In fact, the greatest  area of
flood  production  in  this province  lies  in  the
elevational band  where snowpacks can be melted
out by rainfall. Setting of the lower boundary of the
high elevation zone  at 4,000 feet  reduces this
problem somewhat.
  Due  to limited data from the  snow dominated
regions and the necessity to conserve space, there
has been a great  amount of "lumping" of regions
and regional response.  However, differentiations
are made whenever possible.
        REGIONAL DESCRIPTIONS
New England/Lake State Hydrologic Region (1)


  This area  actually comprises two  separate
provinces: New England and Lake States. Wide
differences in wind and temperature subdivide the
region into two sections.
  Snow in the northeastern section of the province
occurs in shallow packs, seldom over 3 feet in depth
on the level; it may reach much greater  depths at
higher elevations. Subject to frequent incursions of
Arctic air from Canada and warm storms from the
Gulf Stream of the  Atlantic Ocean,  these snow-
packs frequently develop very heavy ice layers on
the surface. Spring rains on such packs yield a swift
return flow to streams, causing rapid rises in the
shallow rivers of the region.  Continued rain melts
the relatively thin packs, adding to the flood. Ex-
tremely cold winters and cool summers limit tran-
spiration  opportunities. Soils are frequently rocky
and water-holding capacities vary extensively. In
locations  of glacial till where extensive ice cover
does not exist, the melting snows are absorbed into
the soil mantle.
  In  the  Great Lakes portion of the region,  ice
layering becomes less of a phenomenon, but early
spring melt and flooding become increasingly im-
portant. Snowpacks and snow become increasingly
wetter as one approaches the upper portion of the
Lower Peninsula  and the  Upper Peninsula of
Michigan. Snowfall and snowpacks are deeper and
drier than in much of New  England. High water
absorptive capacity of the soils, lack  of extensive
surface  relief,  and  widespread bog (swamp)
development prevent  extensive flood threats from
melting snow. High water tables generally provide
sufficient water to meet potential evapotranspira-
tion needs. While temperatures can become very
frigid from incursions of Arctic air, the  lakes
provide an ameliorating influence.
  Westward in  Minnesota  and Wisconsin,  more
frigid temperatures are the rule. Snows frequently
are driven by high winds, and the dry snow is sub-
ject to much more  redistribution than  in  other
areas. Snow distribution  is of little importance in
the region except for  this western edge.
    Rocky Mountain/Inland Intermountain
            Hydrologic Region (4)


  This vast area covers parts  or all of South
Dakota, Wyoming, Montana, Colorado, New Mex-
ico, Arizona, Utah, and Idaho. Most of the water
                                            111.62

-------
for  the  region comes from snowpacks which ac-
cumulate  in winter  and  melt in  summer.  In
general, winter temperatures are very cold, snows
are dry, and snowpacks have a thermal gradient.
That is, snow temperatures at the soil surface ap-
proach  those  of the soil  itself (32°F or 0°C).
Temperatures  from the  soil to the  snowpack sur-
face decrease,  until at the air-snow interface they
reach air temperature, frequently —40°. However,
this region is far from homogenous and the climatic
differences affecting snowpack performance should
be recognized.
  The entire region is subject to summer thunder-
storms which can cause disastrous flooding and as-
sist in recharging the soil water supply. The entire
area is  usually subject  to  snow deposition as  a
result of high winds and dry snow,  except for two
major transition zones — (1) northern New Mexico,
southwestern Colorado, northern Arizona, and (2)
northern Idaho. These are transition zones between
the dry, low temperature snowpacks and continen-
tal  frigid winter  climate of the true Rocky  Moun-
tain chain,  and the warm climate, wet snowpacks
of the Pacific Coast. Dependent upon the direction
from which  the storms and air masses come, the
snowpacks  in  these transition areas will be
representative  of one of the other major provinces
all year; or they may resemble one province during
part of the  year and resemble the other  during
another part of the year.
  In western Montana and in Wyoming plains and
rolling hills, there is enormous displacement and
redeposition of snow. This affects evapotranspira-
tion and tree growth since  it removes the  scanty
snow cover from vast areas and concentrates it in a
few locations. Obviously,  this  favors  increased
plant growth and water use in these sites. Evapora-
tion (sublimation) loss from blowing snow is exten-
sive.

  Snows in  the Rocky Mountains of Wyoming and
Colorado and  in the Wasatch Mountains  are dry
and cold (the skiers' famed  "powder snow"). Wind
redeposition is extensive in large, open areas. Par-
ticularly in  Colorado, much of the mountain chain
lies in the  Alpine Zone. Snowpacks  mature  and
melt in response to "ground heat" from below and
to  warm  air  temperatures and increased solar
radiation in the spring. The thermal gradient  in
such packs  creates unstable snow layers; frequent
avalanching occurs from  this  cause and from
melting snow  sliding over  wind slab formations.
Since most melt occurs from the surface of the pack
downward, the pack largely wets up from the sur-
face. Most melt water goes directly into the soil.
Since the  packs are  "cold,"  first  melt goes to
satisfying the thermal demand needed to bring the
snowpack to a thermal equilibrium (32°F or 0°C)
throughout the pack.
  The  shallow snows in northern Arizona  fre-
quently are redeposited by wind. Because of the
lower latitude and higher insolation in winter,
however, midwinter melt is often sufficient to wet
the surface and prevent further movement.
  Southwestern Colorado, northern Idaho, and the
Rocky Mountains of western Montana receive wet-
ter snows and even occasional rain.  These cause
some limited ice layering in  the  snow  in
southwestern Colorado.
Pacific Coast Hydrologic Provinces (5, 6, and 7)
  This region begins in the San Bernardino Moun-
tains of southern California, continues northward
through  the  Sierra  Nevada of  California,  the
Cascades of Washington and Oregon, and includes
the mountain ridges  and peaks of western and
central Nevada. The same type of snowpacks occur
northward  through British Columbia and into
southeastern Alaska, at  least to Anchorage.
  The maritime climate in the winter is warm and
wet. Summers vary depending upon the particular
portion of the province, but generally they are dry
with little  or no  summer precipitation.  Summer
thunderstorm  activity  is  extensive  over  the
southern Sierra Nevada,  adding some water to that
area, largely in the relatively treeless alpine area.
The remainder of the Pacific Coast province, with
the exception of parts of Washington, receives little
summer precipitation.
  Fall and  winter precipitation  is normally  snow,
but extensive  rainstorms sometimes occur  up to
8,000  feet  elevation in  the Central  Sierra  (7).
Significant  snow falls at elevations down to 4,000
feet, and, on rare occasions, significant amounts
fall to  2,000 feet. Rains remove snowpacks up to
6,000  feet  elevation and  infrequently  remove
significant  parts of the packs to over 7,000 feet.
  Snowpack depth is extremely variable and has
been measured at maximum pack from 36 inches to
over 275 inches.
  Snow redistribution normally does not occur due
to the wetness of the snow.
  Snow metamorphism  continues all winter as a
                                              m.63

-------
result of the warm climate, and frequent ice lenses
occur throughout the packs, particularly on south,
open  slopes. Temperatures  normally  remain at
32° F throughout the packs. When rain falls on
packs  significantly lower  than  32°F,   serious
flooding can occur from  rain and melt water flow-
ing over the frozen layer (Smith 1974).
  Snowpack  configuration  of these  warm,  wet
snows typically consists  of a mixture of heavy and
light  density layers  having  different  maturation
schedules  and water-holding capacities. The con-
figurations vary dramatically  by aspect and by
forest cover (Smith 1974, 1975).
  Because of warm  climate, frequent rains,  and
melting snow,  snowpacks in  the subalpine are
usually  wet and remain at  thermal  equilibrium
throughout  the  snow season.  Frequent snowfalls
keep the albedo high (80-90) until spring melt out
is well under way, at which  time albedo drops to
about 45 percent. Major winter  melt is caused more
from  absorption of solar radiation by the rocks,
trees  and shrubs standing  above the  snow than
from  direct solar radiation to the pack. These, in
turn,  heat up and radiate sensible heat to the pack.
This creates the major melt until late season low
albedos of the snow increase radiation absorption
by the pack.
   Because of the isothermal, wet condition of the
snow, forest cover change can be used to direct heat
into or  away from the snow. Melt out date can be
moved forward or backward 2 weeks to 1 month by
increase or decrease of forest  cover (Smith 1974,
1975).
   While wind distribution plays little role in this
province,   differential  melt is substantial.  The
greater  amount of snow in forest openings on the
west-south walls were once thought to be the result
of distribution;  it has since  been found to be the
result of greater melt on the north and east side of
the opening (Smith 1974).
   Forest interception has been found to have little
influence  on snow placement under lodgepole; but
under red fir and other conical-shaped crowns, the
snow caught while the  branches  were extended
depresses the crowns, and snow is deposited near
the tree stem  where it may  differentially melt
(Smith  1974).   This  accounts for the previous
findings that only 65 percent of snow which fell in
the open was found in the forest. At one time it was
believed that much of this was lost to evaporation.
It has since been found  that evaporation accounts
for less than 2  area-inches  over such areas  that
have  half their area in forest and half in open.
    LIMITATIONS AND PRECAUTIONS:
         PROBLEMS ASSOCIATED
   WITH HYDROLOGIC MODELING FOR
              SNOW REGIONS
  There are more problems associated with model-
ing the hydrologic responses of snow covered basins
than with modeling those subject to rainfall.
  Snowfall redistributes the precipitation in time
and  occasionally in space. Snow falling in the
Rocky Mountains  is  not reflected in  the soil
moisture or streamflow until spring melt. In the
Pacific  Coast  province  it  may appear  as soil
moisture or streamflow within a few days, or it may
not appear until spring. Due to lack of ice lenses,
melt or rain falling on snow in this region may enter
the soil under a forest growing on a south slope.
Removal of the forest may result in ice lens forma-
tion in the pack, and rain or melt may flow through
the snow to the stream and never reach the soil to
provide water for satisfaction of soil water deficit.
  Soils are youthful and very porous, thus resulting
in rapid  drainage of surplus  water  following
snowmelt.  Since  summers are usually  long and
without precipitation, early snowmelt results in a
lengthening of the drought season.
       PROCEDURAL FLOW CHART
  Evapotranspiration for snow dominated regions
is  estimated  using  precipitation  and  energy
relationships with subsequent adjustments made
for snow redistribution and vegetation cover den-
sity. The difference  between  precipitation  and
evapotranspiration  becomes  water available  for
streamflow if changes in  soil  moisture storage are
negligible.
  The  flow chart  in  figure III.23  outlines the
methodology procedure for estimation of potential
streamflow.  Worksheets III.5 and in.6 have been
constructed  to facilitate calculations.
  Explanation of the flow chart follows.
     HYDROLOGIC REGION OR PROVINCE
  Based on the preceding discussion, select the
region which most closely characterizes the site.
                                              HI.64

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                 CONDITION
  The condition or point in time for which each
analysis is to be made must be specified. Condition
can represent baseline, existing (if different from
baseline)  or proposed. The following discussion
centers   on  two  conditions—existing  and
proposed—primarily to evaluate impact of planned
activities; but the methodology is flexible and a
variety  of conditions could be considered.  The
methodology  is  looped so that procedural steps
return to this point after both evapotranspiration
and  water available for streamflow  have been
calculated for each condition.
               ENERGY ASPECT
  One of the  first  criteria  for subdividing  the
watershed or management unit is aspect. Energy so
strongly  controls snow  processes that the major
criterion for subdivision is the energy class for  dif-
fering aspects.
  Several aspect and elevation zones were com-
bined into three basic  energy levels. The  energy
aspects were defined as:
  1. High energy-low elevation aspects (low, south
     aspects)
  2. Intermediate energy aspects
     a. Low to mid-elevation north, east, and west
        aspects
     b. High elevation  south aspects
  3. Low energy-high  elevation  aspects  (high
     elevation north, east, and west aspects)

The significance of classifying by aspect is, of
course, in terms of energy available to melt snow
and to  evapotranspire water. The  elevation and
aspect of a site must be determined and placed in
one of the three energy aspects for  use in further
analysis  (item 4).
        SILVICULTURAL PRESCRIPTION
  For each condition, divide the energy aspect or
management  unit  into  subunits  based  on
silvicultural prescription. The prescription should
be uniform for each subunit and may be uniform
for the entire energy aspect. By the same token, the
silvicultural prescription can be uniform (forested)
for one condition (existing) and varied (clearcut,
thinned) for  another.  Silvicultural  prescription
designations  allow  flexibility  to subdivide  the
energy aspect into  subunits based  on significant
silvicultural  or  hydrological  characteristics  of
either  the site or the prescriptions. This  implies
subdivision based not only on  silvicultural prac-
tice,  but also on uniform soil depth and aspect.
                                                                       SEASON
   Evapotranspiration is calculated by season, and
 seasonal dates can vary by region. In the modeling
 effort, selection of seasonal dates for each region
 and province  was based  on  simulated
 precipitation/streamflow relations. Basically, the
 intent was to isolate the fall, the winter (period of
 snowpack development and melt), and the growing
 season. The  season is  entered in item (9).
   In the Rocky  Mountain/Inland Intermountain
 region  (4)  and in  the  Continental/Maritime
 province  (6),  seasonal   evapotranspiration is
 presented for three increments of time as follows:
       Winter: Oct. 1—Feb. 28
       Spring: March 1—June 30
       Summer and fall: July 1—Sept. 30
   In the Pacific Coast/Central Sierra province (7)
 and in the Pacific Coast/Northwest province (5),
 seasonal evapotranspiration is presented for four
 increments of time:
       Early  winter:  Oct. 1—Dec. 29
       Late winter: Dec. 30—Mar. 28
       Spring: Mar. 29—June 26
       Summer and fall: June 27—Sept. 30
   The New  England/Lake States region (1) has
 three seasons, varying slightly from the others:
       Fall, early winter: Oct. 1—Jan. 31
       Late winter, early spring:  Feb. 1—Apr. 30
       Growing season: May  1—Sept. 30
   The procedure is looped  so that evapotranspira-
 tion and water available  for streamflow are es-
 timated by season within  a silvicultural prescrip-
 tion before the next prescription is considered.
                                               m.65

-------
                f  Hydrologic Region or Province   )
                No
                             Condition
                           Energy Aspect
                               Season
                          Silvicultural State
                            Precipitation
        J
                       Silvicultural Prescription      }
      Yes
                No
Snow Retention Coefficient
     from Figure 111.6
                                       Yes
                                                    Snow
                                                   Redistri-
                                                bution Likely?
                                                Yes
                          No
Snow Retention Coefficient
     from Appendix A
                              Adjusted
                            Precipitation
                         Evapotranspiration
                               m.66

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                                                              Cover Density
                                                            Evapotranspiration
                                                            Modifier Coefficient
                                            Adjusted
                                       Evapotranspiration
                                         Water Available
                                     for Annual Streamflow
                                              All
                                             Silvi-
                                            cultural
                                       States Considered?
                                                                    All
                                                                 Seasons
                                                               Considered?
                                       Water Available for
                                       Annual Streamflow
                                              All
                                             Silvi-
                                            cultural
                                          Prescriptions
                                          Considered?
                                                                   All
                                                                 Energy
                                                                 Aspects
                                                              Considered?
                                               All
                                           Conditions
                                          Considered?
Figure 111.23.—Flow chart of methodology for determining water available for annual •treamflow, snow
                                     dominated reglone.
                                          m.67

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(1)  Watershed name
(5)  Vegetation type_
                                            WORKSHEET



               Water available for streamflow for the




(2)  Hydrologic region	



(6)  Annual  precipitation	
Season
name/dates
(9)

Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
SI Ivicultural
state
(11)






Total for season
Area
Acres
(12)







%
(13)







Precipi-
tat I on
(in)
(14)







Snow
retention
coef .
(15)







Adjusted
snow
retention
coef.
(16)







Adjusted
precipi-
tation
(in)
(17)









Un impacted
Impacted






Total for season












































Un impacted
Impacted






Tota 1 for season












































Un impacted
Impacted






Total for season











































Water
aval lable
for annual
streamflow
(In)
Un Impacted
Impacted
(30)
(31)
(32)
(33)
(34)
(35)
                                                    111.68

-------
Ill .5




existing condition in snow dominated  regions




(3) Total watershed area (acres)  	
(7) Windward length of open area (tree heights)
 (4)  Dominant  energy-aspect



	 (8)  Tree  height  (feet)
ET
(In)
(16)







Basal
area
(ft2/ac)
(19)







Cover
density
%
(20)







1Cm







ET
mod I f I er
coef .
(22)







Adjusted
ET
(in)
(23)







Water available for streamflow (In)
(24)







(25)







(26)







(27)







(28)







(29)























































































































































































































































































                                                   m.69

-------
Notes for Worksheet I I 1.5

Item or
Co I. No.                                 Notes
  (1)         Identification of watershed or watershed subunlt.

  (2)         Descriptions of hydrologic regions and provinces are given in
              the text.

(3)-(8)       User supplied.

  (9)         Seasons for each hydrologic region are described in the text.

  (10)        The unimpacted compartment includes areas not affected by
              siIvicultural  activity.   The impacted compartment Includes areas
              affected by siIvicultural  activity.  Impacted areas do not have
              to be physically disturbed by the si IvicuItural  activity.  For
              example, if an area is subject to snow redistribution due to a
              si IvicuItural  activity,  it is an impacted area.

  (11)        Areas of similar hydrologic response as identified and
              delineated  by vegetation or si IvicuItural  activity.

  (12)        User supplied.

  (13)        Column (12) T item (3).

  (14)        User suppIied.

  (15)        From figure I I I.6 or appendix A or user supplied.

  (16)        Snow retention coefficient adjustment for open areas:
                                   .50
               Poadj = 1  + ( Po~1)(~x~)
        where:
               Poadj = adjusted snow retention coefficient for open areas
                       (receiving areas)

                  P0 = snow retention coefficient for open areas
                       open area (in acres)
                       impacted area (in  acres)
                                      m.70

-------
              Snow retention  coefficient  adjustment  for  forested  source
              areas (impacted forest areas):
                  , 1 - PoadJ  X
                r         1-X
         where:

               Pf  = adjusted  snow retention  coefficient  for  areas affected by
                    snow redistribution  (source areas)
                    open area (in acres)
                A  =
                    impacted  area (in acres)
  (17)         Column (14)  x column (16)

  (18)         From figures 111.24 to 111.40  or  user  supplied.

  (19)         User supplied (not required if  %  cover density is  user
              supplied)-

  (20)         From figures 111.41 to 11 I.45  or  user  supplied.

  (21)         (Column  (20) -f  Cdmax)  x 100 where Cdmax is tne I cover  density
              required for complete  hydro logic  utilization.   C^max is
              determined by professional  judgment at the site.

  (22)         From figures I I I.46 to I I 1.56.

  (23)         Column (18)  x column (22).

(24)-(29)     The  quanitity [column  (17)-column (23)] x  column (13).

  (30)         Sum  of column (24).

  (31)         Sum  of column (25).

  (32)         Sum  of column (26).

  (33)         Sum  of column (27).

  (34)         Sum  of column (28).

  (35)         Sum  of column (29).
                                    HI.71

-------
(1)  Watershed  name
(5)  Vegetation  type_
                                            WORKSHEET



               Water  available for  streamflow  for the




(2)  Hydro I ogle region	



(6)  Annual  precipitation	
Season
name/dates
(9)

Si Ivicultural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11)






Total for season
Area
Acres
(12)







*
(13)







Precipi-
tat I on
(In)
(14)







Snow
retention
coef .
(15)







Adjusted
snow
retention
coef.
(16)







Adjusted
precipi-
tation
(In)
(17)









Un impacted
Impacted






Tota 1 for season












































Un Impacted
Impacted






Tota 1 for season












































Un impacted
Impacted






Tota 1 for season











































Water
aval I able
for annual
streamflow
(In)
Un Impacted
Impacted
(30)
(31 )
(32)
(33)
(34)
(55)
                                                    m.72

-------
I I 1.6




proposed condition in  snow dominated  regions




(3) Total watershed area (acres)	
(7) Windward length of open area (tree  heights)
 (4)  Dominant  energy-aspect



	  (8)  Tree  height  (feet)
ET
(in)
(18)







Basal
area
(ft2/ac)
(19)







Cover
density
%
(20)







*°?3W







ET
mod i f i er
coef .
(22)







Adjusted
ET
(In)
(23)







Water available for streamflow (in)
(24)







(25)







(26)







(27)







(28)







(29)







                                                     m.73

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Notes for Worksheet I I 1.6

Item or
Col. No.                                Notes
  (1)         Identification of watershed or watershed subunlt.

  (2)         Descriptions of hydrologic regions and provinces are given in
              the text.

(3)-(8)       User supplied.

  (9)         Seasons for each hydrologlc region are described In the text.

  (10)        The unImpacted compartment includes areas not affected by
              si Ivicultural  activity.  The Impacted compartment Includes areas
              affected by siIvlcultural  activity.  Impacted areas do not have
              to be physically disturbed by the siIvlcultural  activity.  For
              example, If an area Is subject to snow redistribution due to a
              siIvlcultural  activity, It Is an Impacted area.

  (11)        Areas of similar hydrologlc response as identified and
              delineated by vegetation or siIvlcultural  activity.

  (12)        User supplled.

  (13)        Column (12) T Item (3).

  (14)        User supplled.

  (15)        From figure I I I.6 or appendix A or user supplied.

  (16)        Snow retention coefficient adjustment for open areas:
                                   .50
               poadj = 1  + ( PO-IH—)

        where:

               poadj = adjusted snow retention coefficient for open areas
                       (receiving areas)

                  Po = snow retention coefficient for open areas
                       open area (in acres)
                       impacted area (in acres)
                                    HI.74

-------
              Snow  retention  coefficient  adjustment  for  forested  source
              areas (impacted forest  areas):
                 , 1- PpadJ  X
                T         1-X
         where:

              Pf = adjusted  snow  retention coefficient  for  areas affected  by
                    snow  redistribution  (source areas)
                    open  area (In  acres)
                    impacted  area  (in acres)
  (17)         Column (14)  x column (16)

  (18)         From  figures I I 1.24  to  11 1.40 or  user  supplied.

  (19)         User  supplied  (not required if  %  cover density is user
              supplied).

  (20)         From  figures 111.41  to  11 1.45 or  user  supplied.

  (21)         (Column (20) 4  Cdmax) x 100 where Cdmax is the % cover  density
              required for complete hydro logic  utilization.   C(jmax is
              determined  by professional  judgment at the site.

  (22)         From  figures I I I.46  to  111.56.

  (23)         Column (18)  x column (22).

(24)-(29)     The quanitity [column  (17)-column (23)] x  column (13).

  (30)         Sum of column  (24).

  (31)         Sum of column  (25).

  (32)         Sum of column  (26).

  (33)         Sum of column  (27).

  (34)         Sum of column  (28).

  (35)         Sum of column  (29).
                                     IE.75

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               SILVICULTURAL
                    STATE
  In order to assess the overall hydrologic effect of
silvicultural prescriptions on streamflow, each area
receiving different treatments  is  considered  in-
dividually (items 10 and 11). The summation of
hydrologic effects in each treatment area yields an
overall effect for the prescription. Treatment areas
are  delineated  and grouped to  reflect  similar
hydrologic response. For example, large open areas
may be grouped, small open areas may be grouped,
forested  areas  may  be  grouped.  Hydrologic
response  is  related to  the type and  quantity  of
vegetation at a site as  well as to physical factors
such as slope,  soil texture, solar  radiation, and
precipitation regime. In snow dominated regions,
cover density  (Cd) and snow  redistribution  are
major criteria used for  identification and delinea-
tion of silvicultural activity areas. Cover density
and snow redistribution are discussed  later in this
section.
changed. If snow redistribution is not a factor, or if
openings are not present, precipitation need not be
adjusted and  gross precipitation should be con-
sidered synonomous with "adjusted precipitation."
  If openings are present, it must be considered if
snow redistribution is likely.

                    SNOW
               REDISTRIBUTION
                   LIKELY?
  As noted, precipitation characteristics in some
regions are such that the creation of openings can
significantly alter snow distribution, while in other
regions this is not the case. If openings are con-
sidered not to affect snow distribution (answer =
no) the precipitation estimate made above is con-
sidered to be the adjusted precipitation. If openings
can  affect  distribution then sizes  must be
evaluated  since  this  influences  redistribution
characteristics.
               PRECIPITATION
                                                                      OPENING
                                                                       >15H?
  An estimate of precipitation by season (item 14)
must be supplied. It may vary by energy aspect.
Based on site measurements or extrapolation from
other data, the estimate may represent a long-term
mean or an extreme value, depending upon the ob-
jectives defined.
                  OPENINGS
                  PRESENT?
  In some  areas  in  which  the major  form  of
precipitation  is  snowfall,  the meteorological-
topographic relationship may not  be significant,
but in  other  areas it is.  In the  Rocky Moun-
tain/Intermountain region, for example, snowfall is
the dominant form of precipitation and windblown
snow dominates the regime. In this area, when the
forest  cover  is  removed  through spatially  dis-
tributed  openings,  snowfall  distribution  is
  The  aerodynamic change  in  roughness  of  the
vegetative surface modifies patterns of snow  ac-
cumulation so that  more snow may accumulate in
the cutover area and less in the uncut forest.
  Objective methods for quantifying the univer-
sality of the effects of silvicultural activities on
snow redistribution through snowblowing are  not
yet available;  quantification of these effects must
be based on considerable judgment and experience
in a particular area.
  Significant increases in snow accumulation near
the center of small forest openings—less than 15H
in diameter (H = height of surrounding trees) —
are substantially  offset by  decreases in snowpack
below the undisturbed forest so that  total snow
storage  on watersheds subjected cutting  is  not
changed. For  openings less than 15H, determine
the redistribution coefficient directly from figure
in.6. When openings are large — greater than 15H
in  diameter  —  however,  total  watershed snow
storage  may be decreased through  large sublima-
tion losses and transport of snow out of the basin
                                               m.76

-------
 (see fig. III.6  for approximate effect).  Openings
 greater than 15H in diameter or greater than 15H
 in windward length produce a more complex snow
 redistribution  than  smaller openings. A detailed
 discussion  of  snow  redistribution for  openings
 greater than 15H is presented in appendix in.A.
  Depending upon the average size of the openings
 in the silvicultural state, obtain a retention coef-
 ficient from figure ffi.6,  appendix in.A. or local
 derivation,  and  proceed  to determining the ad-
 justed snow retention coefficient.
       SNOW RETENTION COEFFICIENT
               FROM  FIGURE 111.6
   For clearcuts less than 15H  in diameter or in
 windward length, the  snow retention  coefficient
 (item 15) may be found on figure ELS. A represen-
 tative average length or diameter can be applied to
 a watershed with openings of varying diameters or
 windward lengths. Alternately, if greater resolution
 is required, the watershed can be subdivided so
 that  openings can be handled  individually or in
 groups.
   Any large retention of snow as a result of forest
 cutting can be an important factor in determining
 the amount of runoff. For example, in the lodgepole
 pine  type in Colorado,  this redistribution effect is
 not   greatly diminished  30  years  after  timber
 harvest, in spite of regrowth of trees and associated
 increase in forest cover density. It is thought that
 changes in  natural  snow accumulation patterns
 produced by timber harvest will persist until the
 new  crop of  trees approaches  the  height  of the
 remaining undisturbed  forest.
   The significance of the snow retention coefficient
 (p) lies  in  the opportunity that exists for both
 decreasing the net water loss from the pack and for
 altering the melt rate. As already noted, it can be
 expected that the transpiration losses in the open-
 ings will be decreased following cutting. By placing
 a greater percentage of the total  snowpack in these
 openings and less in the residual forest, the ex-
 posure of the net precipitation (in this case, snow)
 to evapotranspirational processes can be reduced.
 Because this  snow is redistributed and because
 cover conditions have been altered, a significantly
greater  proportion of  the pack  is exposed  to
sunlight, and differing melt rates can be expected.
  In contrast, as the size of the  opening increases
beyond 15H, the opportunity for increased ablation
losses and wind scour reduces the net precipitation
 below pre-silvicultural activity levels. This effect is
 significant since it represents a net loss in water in-
 put to the system.
   In  old-growth subalpine forest,  optimum
 redistribution of snow occurs when the stand is (1)
 harvested  in small patches  of less than  5H  in
 diameter;  (2) the patch  cuts  are protected from
 wind; and (3) the patches are interspersed at least 5
 to 8H apart.
   In regard to redistribution of a finite amount of
 snow, in openings less than  15H there is  a con-
 tributing area for  increases occurring in the open-
 ings. The area of contribution is about equal to the
 area of the opening; therefore, if the openings oc-
 cupy more than 50 percent of the area,  redistribu-
 tion will be less efficient. In  these situations  P0,
 would have to be adjusted to reflect the limiting
 contributing area. If the area cut exceeds 50 per-
 cent, the following adjustment in p0  can be used:
                                          (IH.3)
    X    =
                  open area
            total impacted area
It  should be emphasized that the redistribution
theory does not require adjustment when timber is
harvested in small patches which occupy less than
50 percent of the watershed. In this case P0 = Poadj
since P0adj is used in the following  equation. The
snow retention coefficient for the residual  forest
stand (p f ) is calculated and weighted as follows:
=   1-PoadjX
                                        (m
  u
where:
      pf   = adjusted snow retention coefficient
              for forested areas affected by snow
              redistribution
      poadj = adjusted snow retention coefficient
              for open area (item 16)
   The snow  retention coefficient for the forested
impacted area is calculated under the assumption
that a silvicultural activity  causes no net increase
or decrease of snow on the impacted area. Total im-
pacted  area  in snow dominated regions  includes
areas affected by  a silvicultural activity  either
directly  or indirectly. These  effects  may involve
snow redistribution and evapotranspiration.

       SNOW RETENTION  COEFFICIENT
              FROM APPENDIX A

  The procedure for calculation of snow retention
coefficients  for openings  larger than  15H  in
diameter or windward  length is found in appendix
III.A.
                                                HI.77

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          ADJUSTED PRECIPITATION
  Adjusted seasonal precipitation (item 17) for a
silvicultural  state  is obtained  by  multiplying
seasonal precipitation (supplied by the user) by the
adjusted snow retention coefficient for that area. If
snow distribution is not significant for an activity
area, the snow retention coefficient is 1.0. The es-
timates of precipiation, corrected for treatment are
now used to estimate site specific evapotranspira-
tion.
            EVAPOTRANSPIRATION
  Analysis of  several hundred station years of
records simulated by the Subalpine Water Balance
Model (Leaf  and  Brink 1973) has  shown that
seasonal evapotranspiration (item 18) can be ex-
pressed as a function of seasonal precipitation. In
some  areas the  data  base  did  not encompass
precipitation levels which would result in limiting
the evapotranspiration level,  and for these regions
the  potential  effect  has been estimated.  Since
much  of the area affected by  snowpack develop-
ment is close to  being  arid,  the  baseline level of
evapotranspiration can  be limited by insufficient
precipitation.
  The  evapotranspiration/precipitation  relation-
ships developed  for the Rocky Mountain/Inland
Intermountain hydrologic region (4) are plotted on
figures ffl.24 to HI.26. Unlike the presentation for
rain dominated  regimes, the relationships are
presented as functions of seasonal precipitation by
energy aspect zones.


  Similar relationships for the other hydrologic
regions follow:
  Pacific Coast — Northwest (5) on figures m.27 to
  HI.30
  Continental/Maritime  (6) provinces on figures
  HI.31 to m.33
  Central Sierra  (7) on  figures  IH.34  to 111.37
  New England/Lake  States (1) on figures in.38 to
  m.40.
  It  can be noted that simulated evapotranspira-
tion  is strongly  precipitation  dependent at low
precipitation levels.
  Consulting  these figures (HI.24 to 111.40),  it is
possible to estimate baseline evapotranspiration
for a given precipitation regime. The curves repre-
sent normalized averages based on simulations. If
more accurate  baseline estimates  of actual  or
potential evapotranspiration can be supplied, these
may be more  representative of a specific site. The
input required is an estimate of seasonal precipita-
tion from  which  evapotranspiration  can be es-
timated.
  One apparent discrepancy can be noted. A close
inspection  of the curves  reveals that, for those
seasons in which evapotranspiration is precipita-
tion dependent, the change in ET per unit change
in precipitation may be greater than 1. The curve
represents  an integrated response and should not
be used to evaluate a change in seasonal precipita-
tion alone, as  the curves represent dependence not
only on seasonal precipitation but on antecedent
precipitation as well.
  In the Rocky Mountain/Inland Intermountain
hydrologic  region, the October 1 through February
28 interval (figs. III.24 to III.26) is not precipitation
dependent since losses are essentially from in-
terception and evaporation from the snow surface.
These  losses are aspect dependent,  as shown in
figures  in.24  to III.26. Evapotranspiration losses
during  the  March  1-June  30  interval vary  with
precipitation below about 12 inches and  also de-
pend on aspect. No aspect dependence was found
for evapotranspiration  losses during the July  1-
September 30 interval, as shown in  figure 111.26.
  In the Continental/Maritime province  (6), the
winter interval was found not to be precipitation
dependent,  since losses are essentially from in-
terception and snow evaporation. These losses are
aspect dependent (figs. EI.31 to 111.33). Evapotran-
spiration losses during the March 1-June 30 inter-
val vary with precipitation below about 15 inches,
and also depend on aspect. No aspect dependence
was found for  evapotranspiration losses during the
July 1-September 30 interval (fig. HI.33).
  In the Central Sierra province (7), both the early
and  late winter intervals were found not to be
precipitation  dependent, since losses are essen-
tially from interception  and evaporation  from
snow. These losses are aspect dependent as in-
dicated by figures ni.34 to ni.37. Evapotranspira-
tion losses  during the  March 29-June 26 interval
(fig. ni.36) vary with precipitation below about 12
inches,  and  also depend on aspect. No aspect
dependence  was  found  for  evapotranspiration
                                                m.78

-------
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Ł 5-
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East & West Aspects


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I
  CO
             6          8          10         12
     SEASONAL PRECIPITATION, inches
                                                                                        14
16
            Figure 111.24.—Precipitation-evapotranspiration relationships for Rocky Mountain/Inland Inter-
                        moun»_
-------
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6 ' 8 10 12 14 1(
w SEASONAL PRECIPITATION, inches
 Figure 111.26.—Precipitation-evapotranspiration relationships (or Rocky Mountain/Inland Inter-
         mountain hydrologic region (4), summer and fall season, by energy aspect.
CO
CD
ANSPIRATION, inc
o ^ cn c
1 1 1 1 1 1 1
5ONAL EVAPOTF
— N) C
1 1
55 c
CO




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OC A




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0 3
South
' 'f;>
East & Wes
North

1
0 4
Aspect
5t Aspects
Aspect

1
0 5




1
0 6C
                         SEASONAL PRECIPITATION, inches
Figure  111.27.—Precipitatlon-evapotranspiratlon relationships  for  the  Northwest hydrologic
                   province (5), early winter season, by energy aspect.
                                       m.so

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o —
i 5:
to 4 —
Ł 3-
3ONAL EVAPOl
-A ro
1
< 1








1








1








1








South Aspect
East & We
North

1
st Aspects
Aspect

1








1
                      10
   20             30             40
SEASONAL PRECIPITATION, inches
50
60
          Figure  111.28.—Precipitation-evapotranapiration  relationships  for the Northwest  hydrologic
                            province (5), late winter season, by energy aspect.
in

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o
c
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0 10-

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East & West Aspects
South













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Aspect













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I
                             468
                       SEASONAL PRECIPITATION, inches
10
12
 Figure 111.30.—Precipitation-evapotranspiration relationships for  the  Northwest  hydrologic
                province (5), summer and fall season, by energy aspect.
CO IU —
03 _
O _
C
1 5-
|—
DC
CL 4-
CO ^
Z
0
CL
SEASONAL EV/
-» ro
1 1
(










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5 1










0 ' 1





Sout

East
Nort

5 ' 2





h Aspect

& West Aspec
n Aspect

0 2







ts


5 3C
                       SEASONAL PRECIPITATION, inches
Figure  111.31.—Precipitation-evapotranspiration relationships for  the Continental/Maritime
               hydrologic province (6), winter season, by energy aspect.
                                      111.82

-------
0

o
c
Z
O
a.   4 —
co     ~

<
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Q.



UJ
Z
o
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UJ
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—








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All So
Mid &
	
Highfs
^- 	 	 •





nth & All Low
Elevations
High East, West Aspects
orth













                                     10            15            20

                                SEASONAL PRECIPITATION, inches
                                                                                25
30
         Figure III.32.—Precipitalion-evapotranaplratlon  relationships  for the Continental/Maritime
                        hydrologic province (6), spring season, by energy aspect.
1 -
0 _
z" ~
O
i 5-
W 4 —
E 3-
O
Q.
ol 2-
_J
0
UJ
CO 1
C



x
/X
/



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1
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i e
Ally
_^- — 	
^-^ 	







1
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\spects — All
	 •








1
J 1
Elevations
^— ^-^— ^— ^^— ^^








1
0 1
                                 SEASONAL PRECIPITATION, inches
         Figure 111.33.—Precipitatlon-evapotrarapiratlon  relationships  for the  Continental/Maritime
                   hydrologic province (6), summer and fall seasons, by energy aspect.
                                              EI.83

-------
 CO
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.c
 o
 c
Z
g


<
tr
Q.
CO

<
cr

O
QL
<

LU
_l
<

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<
UJ
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b.u —
4.0 —
3.0 —
2.0 —
1.0 —
.8 —
.6 —
.5 —
(






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I
5 1






D 1






5 ' 2


South Aspect
East & West A
North Aspect

0 2



spects


I
5 30
                                        SEASONAL PRECIPITATION, inches



              Figure 111.34.—Precipitation-evapotranspiration relationships for the Central Sierra hydrologic
                                  province (7), winter season, by energy aspect.
  CO
  0)
  .c
  o
  c
  o_
  CO

  <
  DC

  O
  CL
  <

  HI
  o
  CO
  <
  111
  CO
5 —
4 —
3 —

p _


1









I








I








1








1



South Aspect






East & West Aspects
North Aspect

1


1
0 10 20 30 40 50 6C
                                        SEASONAL PRECIPITATION, inches
              Figure 111.35.—Precipitation-evapotransplration relationships for the Central Sierra hydrologic
                                province (7), late winter season, by energy aspect.
                                                    m.84

-------
 (0  1n
 
-------
1 5~
1 4-
!r 3-
a.
CO
z
DC 2
L EVAPOT
H 1-
CO
ft








, i








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t 5 I








1
3 7 I



South Aspect
East & West f
North Aspect


3 9 1




Aspects



0 11 12
 CO
                              SEASONAL PRECIPITATION, inches
             Figure 111.38.—Precipitaiion-evapotranspiration relationships for the New England/Lake States
                         hydrologic region (1), fall-early winter season, by energy aspect.
 (O
 
-------
 in
 05
 u
 c
 Z
 O
 DC
 Q.
 CO
  O
  Q.
  <
  UJ
  z
  O
  CO
  <
  m
  CO


10 —
5-
4-
3


East & West
*'
/




Aspects ^ 	
^"





	 • —
•^ ^ —














South Aspecl


North Aspect














   10            15             20
SEASONAL PRECIPITATION, inches
25
30
             Figure 111.40.—Precipitation-evapotranspiration relationships for the New England/Lake States
                           hydrologic region (1), growing season, by energy aspect.
losses during the June 27-September 30 interval
(fig. 111.37). However, due to the typically dry sum-
mer months, soil moisture deficits severely limit
evapotranspiration in the lower snow accumulation
areas to the south and at low elevations. The low
elevation  curve of figure in. 34  reflects  the  low
evapotranspiration  associated  with  high  soil
moisture stresses. Where higher snowpacks  and
later melt seasons provide more residual soil water,
evapotranspiration during the summer and fall is
markedly higher, as  shown in the upper curve.
  In the Northwest  province, both the early  and
late winter intervals were found not to be precipita-
tion dependent, and  losses are essentially from in-
terception and evaporation from snow. These losses
vary with aspect as illustrated in figures 111.27 to
111.29. Evapotranspiration losses during the March
29-June 26 interval (fig. 111.29) vary with precipita-
tion below about 12 inches  and also depend on
aspect.  Aspect  dependence  was also found  for
evapotranspiration  losses during the  June  27-
September 30 period (fig. 111.30) as well.
  In the  New England/Lake States hydrologic
region, the data base for simulations (fig. in.38 to
ni.40) did not provide data  points for low annual
precipitation  amounts.   In   addition,  the
                 predominantly  wet summers  result  in  an
                 evapotranspiration rate that approaches the poten-
                 tial rate. Compared to western regions, elevation
                 was not  considered  a significant  parameter af-
                 fecting evapotranspiration. Again, considering the
                 wet growing season, soil depth significantly af-
                 fecting evapotranspiration was not simulated, ex-
                 cept  in  extremely  shallow  and/or very  coarse-
                 textured soils.
                                    COVER
                                   DENSITY
                  At this point an estimate of evapotranspiration
                which assumes cover density is maximum (Cdmax)
                has been obtained. However, maximum cover den-
                sity may or may not be the case. If it is, the ET es-
                timate is the same as the adjusted ET and the next
                procedural step is the discussion on adjusted ET. If
                the cover  density is less  than maximum, either
                because of existing conditions  or  because  of
                proposed activities, an adjustment in ET must  be
                                               111.87

-------
made to allow for the cover density reduction. In
either case, it is advisable to review the description
of cover density to evaluate the site condition.
  The  estimates  of  baseline  evapotranspiration
presented in figures EI.24 to m.40 represent es-
timates  for  the  full cover  density  (complete
hydrologic utilization). To estimate the impact of a
proposed activity or to adjust baseline conditions
for past silvicultural activity or history that exists,
adjustments must be made to the evapotranspira-
tion values presented in  figures III.24 to III.40.
               COVER DENSITY
  In terms of proposed silvicultural activities or
past history,  the  only significant  site parameter
that is altered is  cover density (item 20). Forest
cover density (Cd) is an index which theoretically
ranges from zero to less than one, it references the
capability of the stand or cover to integrate and
utilize the energy input to transpire water. Cover
density  represents  the efficiency  of the three-
dimensional canopy system  to respond to  the
energy input. It varies according to crown closure,
vertical  foliage distribution, species, season, and
stocking. It is significant in  defining the energy
transmitted to the  ground or the transmissivity
coefficient. The cover density and transmissivity
coefficient do not add up to one. Some estimates of
cover density and transmissivity are listed in table
HI.2.
  Although evapotranspiration is  a function  of
cover density, a silvicultural management plan is
not  expressed in terms of  cover density, but
usually, in terms of some parameter such as basal
area. Before adjustments in evapotranspiration for
the proposed activity can be made, a pre- and post-
silvicultural activity cover density estimate must
be obtained.
  Functions which relate basal areas to forest cover
density are plotted in figures HI.41 to ni.45. These
are generalized curves.  Pre- and post-silvicultural
activity cover density estimates are needed as in-
put to  the methodology. If no more  accurate data
are available, then these figures (EI.41  to KI.45)
may be used as guides in determining the amount
of biomass or cover  density removed using  basal
area as an index to management. A note of caution:
                            inrTmTTTmTiTiT
                100        200        300        4CO
                    BASAL AREA. ft.Vacre
Figure 111.41.—Basal area-cover density relationships for the
  Rocky Mountains/Inland Intermountaln hydrologic region
  (4)—spruce-fir, lodgepole  pine, and ponderosa pine for
  stem diameter > 4 inches  dbh.
The curves represent species with a wide range of
stand conditions with respect to age and vigor.
  The following steps are recommended for use of
figures HI.41 to ffl.45.
  (1) Go to the appropriate basal area-cover den-
sity figure with an estimate of existing stand condi-
tion (basal area) and determine a cover density.
  (2) Then evaluate the morphology of the  stand
— is it at a point of complete hydrologic utilization
for the site? If so, then the cover density estimated
represents the maximum  cover density (Cdmax) for
the site.
  (3) If past history indicates that the site is not
fully occupied, then the cover density determined
(Cd) represents existing conditions only; at this
point,  determine  the maximum potential  basal
area for the  site in  order to determine the max-
imum cover density (Cdmax).
                                                HI.88

-------
      iiini 11 ii HIM i mi minim iiiiiiiii n
      0         100        200        300        400
                   BASAL AREA, ft.Vacre
Figure III.42.—Basal area-cover density relationships (or the
      Continental/Maritime hydrologic province (6).
70 _
8 en""
cf =
1- nn
/ER DENS
i
Illlll
8 30 =
UJ
oc ~
P =
UJ «
z —

o
1






/

y
/
/
/
iniiiiii
10
/


Illllllll
0 2C

/
/
jgepole Pine





Illllllll
0 30

/







Illllllll
0 400
BASAL AREA, ft.Vacre
Figure 111.43.—Basal area-cover density relationships for the
        Central Sierra hydrologic province (7).
   (4) Once the basal area following the proposed
 silvicultural activity is determined, return to the
 figure a second or third  time to obtain  a post-
 silvicultural activity cover density.
   Baseline  conditions  or  complete  hydrologic
 utilization is represented by maximum cover den-
 sity (Cdmax). Subsequent figures presented in the
 handbook  to determine  modifier  coefficients  for
 impact adjustments use the ratio of Cd divided by
 Cdmax-1° most applications, existing or pre-activity
 density equals Cdmax, but since this is not always
 the case, an intermediate analysis  to define ex-
 isting conditions may be required.
             EVAPOTRANSPIRATION
             MODIFIER COEFFICIENT
  Where an estimate of pre- and post-silvicultural
activity cover density for a silvicultural state has
been obtained, the  next step  is  to  adjust the
regional  baseline  evapotranspiration,   given  in
figures 111.26 to 111.40. The pre-activity level is the
baseline  level if past history has not altered the
fully forested condition or if the site is in a state of
complete hydrologic utilization.
  For the Rocky Mountain/Inland Intermountain
region,  figure  III.46  shows modifier coefficients
(item 22) for differing levels of forest cover density
(Cd). The next step involves application of the coef-
ficients to evapotranspiration for  each season to
quantify hydrologic impacts resulting from reduc-
tions in forest cover density.
  Within  the  Continental/Maritime  province,
figures ni.47 to 111.49 represent the modifier coef-
ficients which vary according to forest cover den-
sity. Again, equation HI.14 involves application of
                                                 EI.89

-------
                                                          70
                100        200
                   BASAL AREA, ft.'/acre
                                    300
                                              400
                 100        200
                    BASAL AREA, ft.Vacre
                                                                                           300
                                                                                                     400
Figure III.44.—Basal area-cover density relationships for the
          Northwest hydrologic province (5).
Figure III.45.—Basal area-cover density relationships for the
     New England/Lake States hydrologic region (1).
the coefficients to baseline evapotranspiration for
each of the three seasons to quantify hydrologic im-
pacts resulting from reductions in forest cover den-
sity. Two sets of relationships are given for middle
and high elevations (figs,  ni.47 and  IE.48)  and
another for low elevations (fig. 111.49). The modifier
coefficients in  figure III.49  are used to adjust
baseline  evapotranspiration in  areas of  low
seasonal snowpack accumulation.
  The modifier coefficients in figure El.49 also ap-
ply to montane watersheds in the Rocky Moun-
tain/Inland Intermountain hydrologic  region  (4).
These areas are generally outside the more produc-
tive and commercial subalpine forest zone.
  In the  Central  Sierra  province,  simulations of
silvicultural activities were for a 50-percent reduc-
tion of the mature forest cover density (Cdmax) and
100-percent  reduction.  Modifier  coefficients
derived  from  these simulations  are plotted  in
figures in.50 to HI.53. In this province, the modifier
coefficient for some seasons (primarily late winter)
can exceed 1.0 as the cover density is reduced. This
results from increased exposure of the snowpack,
resulting in increased sublimation and  evapora-
tion.  Two  sets of  relationships  were  derived.
Figures III.54 and III.55 should be used to modify
baseline evapotranspiration  of figure 111.35 in high
snow  accumulation  areas; figures in.52 and in.53
are recommended for use in areas of moderate to
low snow accumulation for figure H[.35.
  Modifier coefficients for the New England/Lake
State region (1) are presented in figure IE.56.
                                                 HI.90

-------
                      FOREST COVER DENSITY
                                                 Cdmax
 Figure  111.46.—Evapotranspiration  modifier coefficients for
  forest cover  density  changes for  the  Rocky  Moun-
  tain/Inland Intermountain hydrologic region (4).
                                                                                     FOREST COVER DENSITY
Figure 111.48.—Evapotranspiration modifier coefficients for
  forest cover density changes for the Continental/Maritime
  hydrologic province  (6)  high and intermediate energy
  aspects—winter season.
                          cdrnax/2

                     FOREST COVER DENSITY
Figure 111.47.—Evapotranspiration modifier coefficients for
  forest cover density changes for the Continental/Maritime
  hydrologic  province (6)  high  and intermediate energy
  aspects—spring, summer and fall seasons.
                            cdmax/2

                      FOREST COVER DENSITY
 Figure  111.49.—Evapotranspiration modifier coefficients for
 forest cover density changes for the Continental/Maritime
 hydrologic province (6) low energy  aspects—all seasons.
                                                           EI.91

-------
                     FOREST COVER DENSITY
Figure 111.50.—Evapotranspiration  modifier coefficients for
  forest  cover density  changes  for the Central  Sierra
  hydrologic  province (7)  intermediate  and  low  energy
  aspects—early and late winter seasons.
         0                  ^dmax/2
                       FOREST COVER DENSITY


Figure 111.52.—Evapotranspiration modifier coefficients  for
  forest  cover  density changes for the  Central Sierra
  hydrologic province (7) high energy aspects—spring, sum-
  mer and fall seasons.
   ffi  .8-
        7
                          cdmax/2
                     FOREST COVER DENSITY
 Figure  111.51.—Evapotranspiration modifier coefficients for
  forest cover density changes for  the Central  Sierra
  hydrologic  province (7) intermediate  and  low energy
  aspects—spring, summer and fall seasons.
                                                                                     FOREST COVER DENSITY
Figure III.53.—Evapotranspiration modifier coefficients for
  forest  cover  density changes for  the Central  Sierra
  hydrologic province (7) high energy aspects—early and late
  winter  seasons.
                                                         m.92

-------
                        cdmax/2
                   FOREST COVER DENSITY

Figure 111.54.—Evapotranspiration  modifier coefficient* for
  forest cover density changes for the Northwest hydrologic
  province (5) all energy aspects—spring, summer, and fall
  seasons.
                 I         T         I
        0                °dma x/2
                   FOREST COVER DENSITY
Figure 111.55.—Evapotranspiration modifier coefficients for
  forest cover density changes for the Northwest hydrologic
  province (5) all  energy aspects—early and late winter
  seasons.
  0.3
                        ^dmax/2
                  FOREST COVER DENSITY
Figure 111.56.—Evapotranspiration modifier coefficients for
  forest cover density changes for the New England/Lake
  States hydrologic region (1)  all energy aspects—all
  seasons.
                                                           ADJUSTED EVAPOTRANSPIRATION
  Adjusted seasonal evapotranspiration (item 23)
for the silvicultural state is obtained by multiply-
ing  evapotranspiration (item  18)  by its cor-
responding modifier coefficient (item 22).


           WATER AVAILABLE FOR
                STREAMFLOW


  Multiplication  of the  treatment  area  (as  a
decimal percentage of the watershed area, item 13)
times the  difference between adjusted precipita-
tion and  adjusted evapotranspiration (item 17-
item 23) is an estimate of area weighted contribu-
tion to  total  watershed flow that will be derived
from the treatment (or state) area by season and is
entered in one of  the  columns  from  24-29.  The
seasonal values for each hydrologic state should be
placed in Separate  columns so that they can later
be  summed and entered  in  columns  30-35, ap-
propriately.
                                                 111.93

-------
                     ALL
               SILVICULTURAL
                   STATES
               CONSIDERED?


  At this point the  contribution of flow from one
treatment area has been calculated and expressed
in inches of flow from the entire watershed for one
season. Only after all treatments for the prescrip-
tion and season are evaluated is a new season con-
sidered.

                     ALL
                  SEASONS
                CONSIDERED?
  Calculations  of evapotranspiration  and water
available for streamflow are  performed for  all
silvicultural states,  seasons, within each  prescrip-
tion.
  A return to the silvicultural prescription step of
the flow chart and  completion of  the subsequent
steps  until all evapotranspiration  and water
available for streamflow for all treatments for a
prescription by season have been calculated is re-
quired.
  Once the seasonal loop has been completed, an-
nual ET, by treatment, can be summed using the
following equation:
       n
T^rri  	 ^   "C^T* 	  t^T^
d 1 A — Zj CjJjlj — € I T-J 1 1
       ,-=1                             (in. H)
  where:
     ETA
                            .( ET
                              n   n
      ET; =
        n  =
annual evapotranspiration
evapotranspiration  modifier  coef-
ficients  (by season) that vary with
forest cover density (item 22)
seasonal evapotranspiration (item
18)
number of seasons
              WATER AVAILABLE
         FOR ANNUAL STREAMFLOW
                  BY STATE
  Since streamflow timing differs by silvicultural
treatment, water available for streamflow for the
entire year must be  sorted by treatment.  Water
available for streamflow for each  treatment  is
summed for each season yielding water available
for  annual  streamflow by season and treatment
(enter  in  col. 30-35).  In  the  next section,
hydrographs will  be  constructed  for each
silvicultural state. A composite hydrograph for the
entire watershed or watershed subunit will be ob-
tained  by  summing  the silvicultural  state
hydrographs.
                     ALL
               SILVICULTURAL
               PRESCRIPTIONS
                CONSIDERED?
  At this point, all calculations for the impacts of a
number of silvicultural states, by season, have been
completed for one prescription. If more than one
silvicultural  prescription  is recommended  per
energy aspect or more energy aspects per condition,
the loop is repeated.
                     ALL
                   ENERGY
          ASPECTS CONSIDERED?
  Once  all the calculations for each prescription
within an energy aspect have been considered, all
energy aspects within each condition need to be
evaluated.
  To obtain an estimate of annual flow, for the con-
dition one first has to sum the contribution from
each state in the prescription using the following
equation:

                     35
             QP=    2     QT         (IE.15)
                  T = 30
 where:
 Qp =
         Contribution  (in area inches) to total
         watershed flow, from the prescription.
  QT =  Flow from treatment area (items 30-35
         from worksheets ni.5 or III.6 depending
         on condition).

To estimate total watershed flow, the prescription
flows can be summed by adding the flows from the
various prescriptions together. If only one prescrip-
tion is defined, it represents  the watershed flow.
                   ALL
               CONDITIONS
              CONSIDERED?
  The flow chart is  constructed  so  that  water
available for annual streamflow is calculated for all
                                             m.94

-------
energy aspects for one condition before the other
conditions  are  considered.  The order  in  which
aspects  and  conditions  are considered may be
changed to fit specific needs. Nonetheless, all con-
ditions (proposed, existing, etc.) and all  energy
aspects (or watershed subunits) for the basin must
be  dealt  with  in  an orderly manner  before
proceeding with hydrograph construction  in the
section,   "Procedural  Description:   Determining
Streamflow Timing and  Volume  Changes As-
sociated With Silvicultural Activities."
                      END
   At this point the  user  has values  of  water
 available for  annual  streamflow  sorted by
 silvicultural state, prescription, and energy aspect
 and condition.  The next step is  construction of
 desired hydrographs for the basin of interest.
     Example: Determining ET And Water
       Available For Annual Streamflow
          (Snow Dominated Regions)


   The following is  an example of how to use the
 methodology. Worksheets  are  not used but  the
 methodology steps are done in order to arrive at the
 information needed for the worksheets. The exam-
 ple  is  Hubbard  Brook  (New  Hampshire),
 watershed 3.
   Step 1. Any watershed under consideration may
 need to be delineated and divided into subunits by
 aspect (item 4).  Also needed in order  to further
 subdivide the watershed  into homogeneous sub-
 units are timber stand data, including the species;
 basal area (item 19) or cover density  (item 20);
 history of cutting; and the  proposed silvicultural
 prescriptions (including the nature of the cut and
 the  size  and spacing of openings if they will be
 created).
   Hubbard Brook watershed can be treated as hav-
 ing one energy aspect with  a southerly exposure.
 The pre-silvicultural condition is fully forested (Cd
 = Cdmax) an(l the example silvicultural prescription
 is a reduction to Cd,= 0 (completely clearcut).
  Step  2.  Determine  the  average  annual  and
seasonal precipitation  (item 14) that can be  ex-
pected for the design year.  This can be obtained
locally from  published  data,  or from a
precipitation/elevation curve  developed for  the
area.
  For Hubbard Brook the precipitation is 47.6 in-
ches per year, with 12.1 inches occurring between
October  1 and January 31,  13.0 inches  occurring
between February 1 and April 30, and 22.5 inches
occurring between May 1  and September 30.
  Given the information available to this point, it
is  possible  to  estimate  the  potential baseline
evapotranspiration (item 18) which might occur on
the site  in the following manner, using figure 111.38
(south aspect).
Season
(item 9)
10/1-1/31
2/1-4/30
5/1-9/30
Total
Precipitation
(item 14)
12.1
13.0
22.5
47.6
Baseline ET
(item 18)
2.45
2.65
16.70
21.80
Of the 47.6 inches of precipitation, approximately
21.8 inches will be used for evapotranspiration and
25.8  inches  is  water  potentially  available  for
streamflow (item 30).
   Step 3.  After establishing baseline conditions,
changes due to the proposed silvicultural prescrip-
tion are determined. In this example, prescription
and state are one. First, evaluate the pattern and
nature of the cut;  use the procedures given to ad-
just  the  precipitation  input  to  reflect  snow
redistribution if it can be expected to occur.
   For Hubbard Brook, no adjustment is made for
redistribution. The  comprehensive  example
presented  for the  Rocky  Mountain/Inland  Inter-
mountain hydrologic region (4)  presented subse-
quently in this  handbook will illustrate the
procedure that should be used to quantify the im-
pacts of silvicultural activities on snow accumula-
tion and redistribution.
   Step 4.  When precipitation has been adjusted to
account for the proposed treatment, evapotran-
spiration must be  adjusted to reflect the expected
change. This is done in the following manner using
input data above and figure 111.56 (assume Cd = 0
after harvest, Cd = Cdmax before harvest).
                                               111.95

-------
Season
(item 9)
10/1-1/31
2/1-4/30
5/1-9/30
Total
Precipitation
(Item 14)
(given)
12.1
13.0
22.5
47.6
Baseline
ET
(Item 18)
(fig. 111.38)
2.45
2.65
16.7
21.8
ET Modifier
(item 22)
(fig. II 1. 56)
1.06
.88
.52
Post-activity
evapotran-
spiration
2.60
2.33
8.68
13.61
  The expected post-activity evapotranspiration is
  13.6  inches  and  the  water  available  for
  streamflow is 34.0  inches  (47.6-13.6). The ex-
  pected increase  in  flow, due  to an evapotran-
  spiration reduction, is 8.2 inches. The observed
  change  in  flow  (Hornbeck and Federer  1975)
  averaged about 11.5 inches.
  In the above example no adjustments were made
for snow redistribution. This, in turn, would adjust
post-silvicultural activity evapotranspiration rates
because precipitation would have  been altered.
Also the basin silvicultural activity was not com-
plicated because the entire basin was treated uni-
formly in pre- and post-silvicultural activity condi-
tions. There was no need to adjust the response for
differing  practices and aspects on  the same
watershed. This will be covered in the complete ex-
ample for Horse Creek (ch. VIII). The methodology
presented in  steps 1-4 is used to evaluate,  for any
silvicultural  activity, the water potentially made
available  by the  evapotranspiration  reduction.
This water is then routed to the soil moisture and
streamflow components of the analysis (see next
section).
                                               m.96

-------
   PROCEDURAL DESCRIPTION: DETERMINING POTENTIAL CHANGES
                IN STREAMFLOW  (STREAMFLOW ESTIMATION)
                          (SNOW DOMINATED REGIONS)
                        NEW ENGLAND/LAKE STATES (REGION 1)
               ROCKY MOUNTAIN/INLAND INTERMOUNTAIN (REGION 4)
       PACIFIC COAST REGION, HIGHER ELEVATION ZONES (PROVINCES 5, 6, 7)
  Unlike the rain dominant regions, the hydrologic
regime in  snow dominated regions allows  water
potentially available for flow to be distributed in a
time dependent hydrograph or distribution graph.
In the snow dominated regions, a significant por-
tion of the annual flow does occur in a predictable
manner as the  result of melting snow.
  A significant impact on the  hydrology of these
areas  is modification of  the  rate of snowmelt
through forest manipulation which not only alters
the quantity of water, but the peak flow rates and
timing as well (Anderson and others 1976, Swanson
and others 1977). Therefore, in order to provide a
useful tool in  evaluating  the impacts  of
silvicultural activities, it is necessary to provide a
means of distributing changes in potential flow and
a means for evaluating when changes would occur.


  Of the two hydrologic regions  (1 and 4) and three
hydrologic provinces (5, 6, and 7) that  are snow
dominated, one is considered an exception. The
New England/Lake States hydrologic region (1),
because of its winter snowpack,  had tcrbe included
in this group for modeling purposes. However, the
snowpack development in this region does not truly
dominate the hydrograph. The rainfall generated
portion of the hydrograph is also quite significant.
For this reason, the techniques for presenting the
effect of silvicultural activities on the water poten-
tially available  for  flow will  be dealt with
separately  at the end of this section in a manner
more closely related to rain dominated techniques.
     HYDROLOGIC REGION OR PROVINCE
  Define the  hydrologic  region characteristics of
the site. (This has already been done for the ET es-
timation.)
                HYDROLOGIC
                 REGION 1?
  Since snow does not dominate the hydrology of
the New England/Lake States region (1) to the ex-
tent it does in hydrologic region 4 and provinces 5,
6, and 7, streamflow procedures are different for
hydrologic region 1. For this region, flow duration
curves  instead of hydrographs are developed. For
the rest of the flow chart for Region 1, review "New
England/Lake States (Region 1)" which is discus-
sed later in  this section.  For Region 4, and the
Pacific Coast hydrologic provinces 5, 6, and 7, con-
tinue with the procedure  described immediately
below.
                 CONDITION
  As  with the ET calculations, perform  the
analysis on each watershed condition.
       PROCEDURAL FLOW CHART


  The  flow  chart  outlining  the  procedure  for
streamflow estimation is given in figure 111.57 and
discussed below. Worksheets HI.7  and ni.8 have
been constructed to facilitate calculations.
              ENERGY ASPECT
  Watershed subdivision into energy aspect units
is the same as for the ET calculations.
                                           m.97

-------
                            (    Hydrologic Region or Province
                             Yes
      New England/Lake States
              Region 1
       Baseline and Open Flow
          Duration Curves

       Cover Density Reduction  j
        Existing and Proposed
        Flow Duration Curves
                                                           No
                                                          Condition
                                              c
              Energy Aspect
    (     Silvicultural Prescription      )4


—K        Silvicultural State         )


1
/
/Open
No / Pres
1
Baseline
Distribution
Hydrograph



Interpolated
Distribution
Hydrograph



                                                                               ings
                                                   Weighted Water Available
                                                     for Annual Streamflow
                                                       Silvicultural State
                                                         Hydrograph
                                                                                            Yes
                                                                                            Open
                                                                                         Distribution
                                                                                         Hydrograph
                                                             All
                                                            Silvi-
                                                           cultural
                                                     States Considered?
                                                                             All
                                                                            Silvi-
                                                                           cultural
                                                                         Prescriptions
                                                                         Considered?
Figure 111.57.—Flow chart of methodology for calculation of composite hydrograph and 7-day flow duration
                                     curve, snow dominated regions.
                                                  m.98

-------
       SILVICULTURAL PRESCRIPTION
  As with  the ET calculations,  the silvicultural
prescription  for  each  energy  aspect  must  be
defined. Each prescription can include one or more
silvicultural states or treatments.
            SILVICULTURAL STATE
  As defined,  silvicultural state relates to the ac-
tual treatment or activity to be  employed  (i.e.,
thinning, clearing, etc.) or describes the vegetative
state in the absence of management.
  The  above  items  (condition,  energy aspect,
silvicultural prescription, and silvicultural state)
define  the  watershed divisions which are used as
components to each analytical loop.
                    COVER
                   DENSITY
                    
-------
                                                                                      WORKSHEET

                                                                  Existing condition  hydrograph

                                                        (1)  Watershed  name
Date
or
Interval
(3)




















Distribution of water
Un impacted

%
(4)




















Inches
(5)




















cfs
(6)





















%
(7)




















Inches
(8)




















cfs
(9)




















Impacted

%
(10)




















Inches
(11)




















cfs
(12)




















Item or
Co I . No.

  (1)

  (2)


  (3)
(4),(7),
(10),(13),
(16),(19)
                                 Notes
Identification of watershed or watershed subunit.

Descriptions of hydro I ogle regions and provinces are given In
text.

Supplied by user.  Either date snowmelt begins or date of
peak snowmelt runoff.

Digitized excess water distribution (?) from tables 111.11 to
I I 1.22 for forested and open condition.  Interpolate between
forested and open for other conditions.
                                   m.ioo

-------
III.7

for snow dominated regions

(2) Hydro logic region 	
available for annual streamflow
Impacted (continued)

%
(13)




















Inches
(14)




















cfs
(15)





















%
(16)




















I nches
(17)




















cfs
(18)





















%
(19)




















1 nches
(20)




















cfs
(21)




















Compos 1 te
hydrograph
cfs
(22)




















                (5),(8),
                (11),(14),
                (17),(20)

                (6),(9),
                (12),(15),
                (18),(21)
                  (22)
Digitized excess water distribution (%) multiplied by water
available for annual streamflow gives flow In Inches.
To convert from area Inches to cfs, the area-Inch hydrograph
Is multIpI led by:
	Total watershed area (In acres)	
 (12 in/ft) (1.98) (Number of days In Interval)

Sum of columns (6), (9), (12), (15), (18), and (21) gives the
composite hydrograph for the entire watershed in cfs.
                                                   III.101

-------
                                                                                     WORKSHEET

                                                                 Proposed condition hydrograph

                                                       (1)  Watershed name    	
Date
or
Interval
(3)




















Distribution of water
Un Impacted

%
(4)




















1 nches
(5)




















cfs
(6)





















%
(7)




















1 nches
(8)




















cfs
(9)




















Impacted

*
(10)




















1 nches
(11)




















cfs
(12)




















Item or
Col. No.

  (1)

  (2)


  (3)
(4),(7),
(10),(13),
(16),(19)
                                 Notes
Identification of watershed or watershed subunit.

Descriptions of hydrologlc regions and provinces are given in
text.

Supplied by user.  Either date snowmelt begins or date of
peak snowmelt runoff.

Digitized excess water distribution (%) from tables 111.11 to
111.22 for forested and open condition.  Interpolate between
forested and open for other conditions.
                                   m.io2

-------
I I I .8

for  snow dominated  regions

(2)  Hydrologic region 	
available for annual streamflow
Impacted (continued)

%
(13)




















Inches
(14)




















cfs
(15)





















%
(16)




















Inches
(17)




















cfs
(18)





















%
(19)




















Inches
(20)




















cfs
(21)




















Compos 1 te
hydrograph
cfs
(22)




















               (5),(8),
               (11),(14),
               (17),(20)

               (6),(9),
               (12),(15),
               (18),(21)
                 (22)
Digitized excess water distribution (?) multiplied by water
available for annual streamflow gives flow in inches.
To convert from area inches to cfs, the area-Inch hydrograph
is multiplled by:
	Total watershed area (In acres)	
 (12 in/ft) (1.98) (Number of days in Interval T

Sum of columns (6), (9), (12), (15),  (18), and (21) gives the
composite hydrograph for the entire watershed in cfs.
                                                   in.ios

-------
ID
Q.
W
UJ
a
x
UJ


-------
0)
0)
Q.

CO
CO
LU
O
X
LU

DC
UJ
                                               I   I   I   I   I   I   I   I   I   I
          Figure 111.59.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
                       tain hydrologic region (4)—treated conditions, low energy aspects.
         Figure 111.60.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
                  tain hydrologic region (4)—treated conditions, intermediate energy aspects.
                                                   ni.ios

-------
Figure 111.61.—Potential water excess distribution graphs for Rocky Mountain/Inland Intermoun-
            tain hydrologic region (4)—treated conditions, high energy aspects.
                                          m.ioe

-------
Table 111.11.—Digitized excess water distribution for the Rocky
  Mountain/Inland   Intermountaln   hydrologic   region
  (4)—low energy aspect.
Percentage In decimals of total annual  flow which will occur
              during 6-day flow intervals
6th day
interval 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0025
0.0100
0.200
0.0475
0.0725
0.0925
0.1050
0.1125
0.1150
0.1150
0.1125
0.0975
0.0550
0.0250
0.0125
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.00
0.0025
0.0100
0.0200
0.0325
0.0525
0.0950
.01425
0.1550
0.1550
0.1400
0.0800
0.0500
0.0325
0.0200
0.0100
0.0025
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Table 111.12.—Digitized excess water distribution for the Rocky
  Mountain/Inland  Intermountaln  hydrologic   region
  (4)—Intermediate energy aspect.
Percentage In decimals of total annual flow which will occur
              during 6-day flow Intervals
6th day
interval1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.0050
0.0150
0.0300
0.0450
0.0650
0.1000
0.1300
0.1375
0.1400
0.1350
0.1150
0.0600
0.0200
0.0025
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.0075
0.0200
0.0350
0.0550
0.0750
0.0950
0.1350
0.1550
0.1600
0.1300
0.0825
0.0325
0.0125
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
  1The intervals are fixed in time with respect to date of peak flow.
The peak data is user specified.
  'The intervals are fixed in time with respect to date of peak flow.
The peak flow is user specified.
  Continental/Maritime  hydrologic province (6):
The baseline  distribution graphs for the  three
energy aspects within the province are plotted  on
figure  HJ.62.  These represent  the  normalized
average  from  simulating many  station  years  of
record.  The same  number  of simulations were
made reducing the baseline cover density by  50
percent and then by 100 percent. Again, reduction
by 50 percent had little, if any, effect on changing
potential streamflow.
  The  relationships between potential flows for
fully forested and open conditions are presented in
figures in.63 to in.65 for each of the energy aspects.
Because of the relative consistency of the simulated
responses, the x or time axis has been dated. Again,
a timing shift of up to 6 weeks and a change in peak
flow rate can be noted.
  The  digitized  excess water  distributions
represented by figures DI.63 to EI.65 are presented
in tables HI. 14 to HI. 16  for  each of the energy
aspects.
  Central Sierras hydrologic province (7): Simula-
tions at a 50-percent reduction in the baseline cover
density did  not indicate a significant change in
flow. Baseline distribution graphs of potential flow
for the three energy aspects are presented in figure
IE. 66. There are two peaks on low and intermediate
energy aspects.  The potential flow distributions for
forested and open conditions are plotted by energy
aspects on figures m.67 to  ITJ.69. Timing of peak
flow rate  changed  by as much as 6 weeks and the
rate itself by 3  percent.
                                                m.io?

-------
Table 111.13.—Digitized excess water distribution for the Rocky
  Mountain/Inland Intermountain hydrologic region
  (4)—high energy aspect.
Percentage In decimals of total annual flow which will occur
              during 6-day flow Intervals
6th day
interval1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Full
Forest
0.00
0.00
0.00
0.0050
0.0150
0.0250
0.0400
0.0600
0.0825
0.1050
0.1400
0.1575
0.1400
0.1050
0.0650
0.0375
0.0175
0.0050
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0025
0.0075
0.0250
0.0425
0.0650
0.0825
0.1075
0.1475
0.1650
0.1450
0.1150
0.0625
0.0250
0.0075
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
  The  digitized  excess  water  distributions  for
baseline and open conditions by energy aspects are
presented in tables HI. 17 to 111.19.
  Northwest hydrologic province (5): Distribution
graphs of excess water potentially available for flow
simulated for  the Northwest hydrologic province
(5) are  presented in figure  111.70  for the three
energy levels.  The   distribution graph  for  this
province is complex with several  rainfall generated
peaks. The effect of simulating a 50-percent reduc-
tion  in  cover density was  negligible.  The  fully
forested and completely open simulations are plot-
ted on figures IH.71 to ffl.73. Note the slight shift in
the snowmelt  peak for the intermediate  and low
energy zones (figs. EI.72 and 111.73).
                                                         Digitized   excess  water  distributions
                                                       presented in tables IE.20 to HI.22.
                                              are
  'The intervals are fixed in time with respect to date of peak flow.
The peak data is user specified.
  Excess water distribution values presented for
both  the Northwest hydrologic province  (5) and
Rocky MountainAnland Intermountain hydrologic
region  (4)  should be  properly interpreted;  they
have limitations. They are simulated distributions
and all the errors inherent in simulation apply (see
app. in.C for a detailed discussion). Because of the
predictability of the snowmelt generated portion of
the hydrograph, this portion of the  distribution
table is  most representative of what  may be ex-
pected and when.
  The rainfall generated portions of the distribu-
tion table are more speculative.  Because of the
variability of rainfall patterns, these portions of the
hydrograph can be normalized only to the extent
                    Oct. 1
                                                                          Aug. 18  Sept. 30
              Figure 111.62.—Potential water excess distribution graphs for Continental/Maritime hydrologic
                               region (6)— baseline conditions, all energy aspects.
                                                 m.ios

-------
  15
» 10
                                                              r i

                                                            •/!
                                                            I   I
                                                                          Baseline
   5-
    Oct. 1
6 days
May8
    DATE
Aug. 18   Sept. 30
     Figure 111.63.—Potential water excess distribution graphs for Continental/Maritime hydrologic
                        region (6)—treated conditions, low energy aspects.
     Oct. 1
6 days
 May8
     DATE
 Aug. 18  Sept. 30
     Figure 111.64.—Potential water excess distribution graphs for Continental/Maritime hydrologic
                    region (6)—treated conditions, Intermediate energy aspects.
                                           m.109

-------

-------
Table 111.14.—Digitized excess water distribution for the Con-
  tinental/Maritime  hydrologic  province  (6)—low energy
  aspects.
Percentage In decimals of total annual flow which will occur
                during 6-day flow Intervals
Table 111.15.—Digitized excess water distribution for the Con-
  tinental/Maritime  hydrologic  province  (6)—intermediate
  energy aspects.
Percentage In decimals  of total annual flow which will occur
                during  6-day flow Intervals
Block
Oct. 1
























Feb. 28





Apr. 11

Apr. 23













Jul. 18



Aug. 12
Aug. 18






Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0061
0.0154
0.0267
0.0395
0.0541
0.0710
0.0922
0.0995
0.1019
0.0995
0.0922
0.0794
0.0669
0.0529
0.0352
0.0219
0.0133
0.0061
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0076
0.0047
0.0036
0.0031
0.0018
0.0010
0.0015
0.0026
0.0010
0.0021
0.0031
0.0026
0.0021
0.0026
0.0031
0.0026
0.0021
0.0010
0.0015
0.0008
0.0031
0.0036
0.0042
0.0026
0.0010
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0053
0.0125
0.0230
0.0356
0.0479
0.0645
0.0869
0.1093
0.1366
0.1237
Q.0946
'0.0634
0.0440
0.0212
0.0133
0.0069
0.0012
0.00
0.00
0.00
0.00
0.0006
0.0026
0.0047
0.0063
0.0070
0.0074
0.0079
0.0082
Block
Oct. 1
























Feb. 28


Mar. 24

Apr. 5

















Jul. 18











Sept. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.00
0.00
0.00
0.00
0.0008
0.0080
0.0184
0.0288
0.0437
0.0581
0.0706
0.0926
0.1115
0.1183
0.1183
0.1014
0.0733
0.0542
0.0372
0.0221
0.0120
0.0053
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0106
0.0068
0.0053
0.0046
0.0027
0.0015
0.0023
0.0038
0.0015
0.0030
0.0046
0.0038
0.0030
0.0038
0.0046
0.0038
0.0030
0.0015
0.0023
0.0011
0.0046
0.0053
0.0061
0.0039
0.0015
0.00
0.00
0.00
0.0008
0.0036
0.0077
0.0164
0.0284
0.0421
0.0605
0.0838
0.1014
0.1091
0.1070
0.0954
0.0694
0.0493
0.0344
0.0213
0.0125
0.0053
0.0016
0.00
0.00
0.00
0.00
0.00
0.00
0.0005
0.0030
0.0050
0.0070
0.0086
0.0096
0.0104
0.0109
                                                        ffl.111

-------
Table 111.16.—Digitized excess water distribution for the Con-
  tinental/Maritime  hydrologic  province (6)—high  energy
  aspects.
Percentage in decimals of total annual flow  which will occur
                during 6-day flow intervals
Table  111.17.—Digitized  excess  water distribution for the
  Central Sierra hydrologic province (7)—low energy aspects.
Percentage in decimals of total annual flow which will occur
                during 6-day flow intervals
Block
Oct. 1
























Mar. 12













Jul. 12













Aug. 18






Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.0028
0.0018
0.0014
0.0012
0.0007
0.0004
0.0006
0.0010
0.0004
0.0008
0.0012
0.0010
0.0008
0.0010
0.0012
0.0010
0.0008
0.0004
0.0006
0.0003
0.0012
0.0014
0.0016
0.0010
0.0004
0.00
0.0004
0.0061
0.0121
0.0194
0.0312
0.0497
0.0783
0.0892
0.1105
0.1247
0.1255
0.1134
0.0722
0.0521
0.0331
0.0223
0.0158
0.0101
0.0061
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.0140
0.0090
0.0070
0.0060
0.0035
0.0020
0.0030
0.0050
0.0020
0.0040
0.0060
0.0050
0.0040
0.0050
0.0060
0.0050
0.0040
0.0020
0.0030
0.0015
0.0060
0.0070
0.0080
0.0050
0.0020
0.00
0.0004
0.0062
0.0175
0.0312
0.0578
0.0887
0.1058
0.1074
0.1016
0.0672
0.0494
0.0385
0.0333
0.0286
0.0229
0.0187
0.0154
0.0104
0.0062
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0020
0.0061
0.0085
0.0101
0.0114
0.0127
0.0138
Block
Oct. 6












Dec. 24










Feb. 28




Mar. 31















Jul. 6








Aug. 24





Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.0004
0.0013
0.0034
0.0058
0.0071
0.0075
0.0071
0.0062
0.0044
0.0030
0.0026
0.0008
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0012
0.0032
0.0057
0.0081
0.0129
0.0201
0.0270
0.0363
0.0443
0.0561
0.0689
0.0762
0.0822
0.0862
0.0862
0.0810
0.0746
0.0621
0.0459
0.0294
0.0186
0.0113
0.0073
0.0040
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.0008
0.0025
0.0039
0.0062
0.0088
0.0102
0.0102
0.0098
0.0088
0.0071
0.0058
0.0043
0.0016
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0012
0.0024
0.0032
0.0057
0.0089
0.0146
0.0210
0.0295
0.0384
0.0505
0.0667
0.0792
0.0916
0.1033
0.1088
0.1081
0.0916
0.0537
0.0291
0.0113
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
                                                        m.ii2

-------
Table  111.18.—Digitized  excess  water  distribution  for the
  Central Sierra hydrologic province (7)—intermediate energy
  aspects.
Percentage In decimals of total annual flow which will occur
                during 6-day flow  Intervals
Table  111.19.—Digitized excess water  distribution  for  the
  Central  Sierra  hydrologic  province  (7)—high  energy
  aspects.
Percentage In decimals of total annual flow which will occur
                during 6-day flow intervals
Block
Oct. 12










Dec. 12








Jan. 31








Mar. 31
















Jul. 12




Aug. 12








Sept. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.0003
0.0005
0.0009
0.0024
0.0048
0.0048
0.0037
0.0025
0.0012
0.0006
0.0003
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0048
0.0125
0.0202
0.0278
0.0374
0.0471
0.0559
0.0663
0.0760
0.0860
0.0936
0.0948
0.0877
0.0743
0.0602
0.0463
0.0350
0.0254
0.0150
0.0069
0.0032
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Ctoarcut)
0.00
0.0004
0.0012
0.0033
0.0055
0.0076
0.0071
0.0063
0.0045
0.0025
0.0012
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0016
0.0028
0.0048
0.0069
0.0101
0.0130
0.0168
0.0208
0.0281
0.0355
0.0437
0.0511
0.0650
0.0818
0.0993
0.1148
0.1131
0.0868
0.0609
0.0453
0.0298
0.0175
0.0073
0.0016
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Block






Nov. 12



Dec. 6





























Mar. 31
Apr. 6


















Sep. 30
6th day
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Full
Forest
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0020
0.0036
0.0053
0.0069
0.0098
0.0109
0.0133
0.0158
0.0186
0.0205
0.0238
0.0278
0.0323
0.0379
0.0451
0.0511
0.0591
0.0717
0.0950
0.0963
0.0865
0.0741
0.0579
0.0439
0.0350
0.0238
0.0170
0.0093
0.0040
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
(Clearcut)
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0020
0.0028
0.0040
0.0057
0.0069
0.0085
0.0093
0.0117
0.0134
0.0150
0.0166
0.0194
0.0215
0.0238
0.0266
0.0294
0.0338
0.0383
0.0443
0.0516
0.0641
0.0807
0.0975
0.1345
0.0758
0.0455
0.0366
0.0290
0.0202
0.0133
0.0089
0.0061
0.0024
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
                                                         m.ii3

-------
01
o
CD
Q.

03
03
LU
O
X
LU

DC
111
z
       Oct.  1
                                               DATE
Sept. 30
       Figure III.67.—Potential water excess distribution graphs for Central Sierra hydrologic region
                              (7)—treated conditions, low energy aspects.
       Oct. 1
                                                                                                 Sept.
                                              DATE
       Figure 111.68.—Potential water excess distribution graphs for Central Sierra hydrologic region
                          (7)—treated conditions, Intermediate energy aspects.
                                                 III.114

-------
     Oct. 1
                                               DATE
                                                                     Sept. 30
       Figure 111.69.—Potential water excess distribution graphs for Central Sierra hydrologic region
                             (7)—treated conditions, high energy aspects.
   15

-------
   15
o>
o
0>
a

CO
CO
LU
O
X
LU

EC
LU



I
10
      Oct. 1
                                               DATE
                                                                                               Sept. 30
         Figure 111.71.—Potential water excess distribution graphs for the Northwest hydrologic region
                                (5)—treated conditions, low energy aspect.
    15
 05

 2
 0}
 Q.

 CO
 CO
 LU
 O
 X
 LU

 cr
 LU
 10
                                                                                 Baseline
      Oct. 1
                                                DATE
                                                                                                Sept. 30
         Figure III.72.—Potential water excess distribution graphs for the Northwest hydrologic region
                            (5)—treated conditions, Intermediate energy aspect.
                                                 m.iie

-------
         15-
         10-
          5-
                                                                       \
                                                                           > Baseline
           Oct. l
Nov. 27
                                             DATE
April 16    June 9  July 15
Sept. 30
             Figure 111.73.—Potential water excess distribution graphs for the Northwest hydrologic region
                                (5)—treated conditions, high energy aspects.
that rainfall can be normalized. They do, however,
represent the nature of the change that may be ex-
pected. The limitations discussed in appendix IHC
apply most directly to these portions of the dis-
tribution table.
  Digitized excess water distributions  provide a
simplified  means of  estimating  the  potential
change in flow distribution which might occur fol-
lowing a proposed silvicultural activity. Using in-
puts  developed  from  the  evapotranspiration
calculations, an adjustment to the  baseline condi-
tion for the proposed activity can be made in the
following manner for each watershed compartment
or energy aspect.
  In region 4, the date  of  peak discharge  from
snowmelt for baseline conditions must be specified.
Once the date for baseline has been established,
the date for the open situation also becomes es-
tablished. Interpolations of distribution graphs for
intermediate vegetal states are also dated.
                  BASELINE
                DISTRIBUTION
                HYDROGRAPH
                              Baseline distribution graphs for the appropriate
                            region can be selected from the previous discussion.
                                              OPENINGS
                                              PRESENT?
                              If cover density is less than maximum, it must be
                            determined if openings are present for the treat-
                            ment or state in question.
                                          OPEN DISTRIBUTION
                                             HYDROGRAPH
                               Distribution hydrographs for open conditions are
                             given by hydrologic region or province and aspect.
                             They can  be found  on  the  corresponding full
                             forested distribution hydrograph figures and tables
                             provided above.
                                              m.117

-------
Table  111.20—Digitized  excess  water  distribution  for the
  Northwest hydrologic province (5)—low energy aspects.
Percentage in decimals of total annual  flow which will occur
                during 6-day flow intervals
Table  111.21—Digitized  excess  water distribution for  the
  Northwest  hydrologic  province  (5)—intermediate energy
  aspects.
Percentage in decimals of total annual flow which will occur
                during 6-day flow intervals
Block
Oct. 1








Nov. 27























Apr. 16


























Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0008
0.0020
0.0028
0.0032
0.0040
0.0048
0.0061
0.0085
0.0116
0.0153
0.0185
0.0204
0.0253
0.0401
0.0293
0.0200
0.0141
0.0104
0.0100
0.0116
0.0128
0.0153
0.0157
0.0149
0.0132
0.0120
0.0120
0.0136
0.0161
0.0192
0.0233
0.0277
0.0313
0.0325
0.0361
0.0382
0.0385
0.0385
0.0393
0.0393
0.0401
0.0397
0.0369
0.0337
0.0281
0.0208
0.0169
0.0121
0.0089
0.0065
0.0040
0.0028
0.0012
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0056
0.0064
0.0068
0.0076
0.0080
0.0092
0.0108
0.0120
0.0136
0.0153
0.0185
0.0204
0.0253
0.0401
0.0293
0.0200
0.0141
0.0104
0.0100
0.0116
0.0128
0.0153
0.0157
0.0149
0.0132
0.0120
0.0120
0.0136
0.0161
0.0192
0.0233
0.0277
0.0313
0.0359
0.0423
0.0470
0.0467
0.0447
0.0423
0.0411
0.0403
0.0395
0.0339
0.0255
0.0179
0.0092
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0008
0.0020
0.0036
0.0048
Block
Oct. 1









Nov. 27























Apr. 16

























Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0004
0.0012
0.0020
0.0028
0.0040
0.0053
0.0065
0.0090
0.0119
0.0153
0.0198
0.0259
0.0354
0.0479
0.0437
0.0306
0.0214
0.0148
0.0139
0.0165
0.0206
0.0247
0.0243
0.0214
0.0198
0.0189
0.0206
0.0231
0.0272
0.0330
0.0330
0.0326
0.0322
0.0330
0.0330
0.0338
Q.0330
0.0322
0.0314
0.0296
0.0272
0.0247
0.0214
0.0165
0.0123
0.0070
0.0040
0.0012
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0044
0.0048
0.0057
0.0065
0.0073
0.0089
0.0105
0.0122
0.0147
0.0171
0.0198
0.0259
0.0354
0.0479
0.0437
0.0306
0.0214
0.0148
0.0139
0.0165
0.0206
0.0247
0.0243
0.0214
0.0198
0.0189
0.0206
0.0231
0.0272
0.0330
0.0330
0.0326
0.0322
0.0330
0.0354
0.0383
0.0392
0.0370
0.0334
0.0293
0.0183
0.0118
0.0065
0.0036
0.0024
0.0012
0.0004
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0008
0.0016
0.0024
0.0032
0.0040
0.0044
                                                         m.iis

-------
Table  111.22—Digitized  excess water  distribution for  the
  Northwest hydrologic province (5)—high energy aspects.
Percentage in decimals of total annual flow which will occur
             during 6-day flow intervals
Block
Oct. 1










Nov. 27






















Apr. 16

























Sept. 30
6th day
interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
Baseline
0.0004
0.0008
0.0012
0.0020
0.0032
0.0050
0.0066
0.0091
0.0127
0.0169
0.0231
0.0322
0.0425
0.0595
0.0540
0.0397
0.0264
0.0202
0.0174
0.0197
0.0314
0.0360
0.0325
0.0292
0.0264
0.0223
0.0210
0.0251
0.0371
0.0392
0.0359
0.0338
0.0322
0.0310
0.0306
0.0305
0.0277
0.0239
0.0206
0.0157
0.0107
0.0074
0.0044
0.0020
0.0008
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Open
0.0051
0.0053
0.0057
0.0065
0.0077
0.0100
0.0114
0.0158
0.0168
0.0237
0.0279
0.0322
0.0425
0.0595
0.0540
0.0397
0.0264
0.0202
0.0174
0.0197
0.0314
0.0360
0.0325
0.0292
0.0264
0.0223
0.0210
0.0251
0.0371
0.0392
0.0359
0.0338
0.0322
0.0310
0.0252
0.0199
0.0142
0.0096
0.0079
0.0063
0.0042
0.0038
0.0029
0.0021
0.0009
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0004
0.0009
0.0017
0.0025
0.0033
0.0041
0.0047
0.0048
INTERPOLATED
 DISTRIBUTION
 HYDROGRAPH
                                                      Distribution hydrographs for partial cuts are in-
                                                    terpolated from full forested  (complete hydrologic
                                                    utilization) and open distribution hydrographs.
                                                      Interpolation   of  distribution graphs  is
                                                    straightforward and linear,  although hydrologic
                                                    response to vegetation change is not linear. For any
                                                    partial reduction in Cd from  Cdmax (baseline), the
                                                    interpolated distribution graph is obtained in the
                                                    following manner.
                                                      For each 6-day  period, calculate the difference
                                                    between the baseline and open percentage of flow,
                                                    multiply the difference by the decimal percentage
                                                    of Cd change from Cdmax. Now add the product to
                                                    the baseline value  to obtain  the  interpolated dis-
                                                    tribution (i.e.,  if Cdmaxis .40 and is reduced to .30,
                                                    this represents a 25-percent reduction in cover den-
                                                    sity).  The intermediate distribution would be a
                                                    point 25 percent of the way between baseline and
                                                    open  values.
                                                           WEIGHTED WATER AVAILABLE
                                                            FOR ANNUAL STREAMFLOW
                                                      Water potentially available for streamflow (P-
                                                    ET) has already been estimated for all conditions
                                                    and treatments in the preceding section on ET es-
                                                    timation. The objective now is to apportion that
                                                    annual flow using the  appropriate  distribution
                                                    graph.
                                                                  SILVICULTURAL
                                                                       STATE
                                                                   HYDROGRAPH
                                                     Potential streamflow hydrographs  for  each
                                                   silvicultural treatment (items 6, 9, 12, 15, 18, 21)
                                                   are obtained by multiplication of the  distribution
                                                   hydrograph value of each 6-day flow increment by
                                                   adjusted water available for annual  streamflow
                                                   (items 30-35 worksheets III.5 or III.6). Area-inch
                                                   values (items 5, 8, 11,14,17, 20) are then converted
                                                   to cubic feet per  second (cfs) using the following
                                                   formula:
                                              m.119

-------
(cfs) =
       (inches) (watershed area in acres)	
     (12 in/ft)  (1.98) (number of days in interval)

                                       (m.16)

                    ALL
               SILVICULTURAL
                  STATES
               CONSIDERED?
                     ALL
                 CONDITIONS
                CONSIDERED?
  The methodology is structured so the hydrograph
for  one  condition must be constructed before the
hydrograph  for a second  condition can  be
calculated.
  The following is the methodology appropriate for
region 1.
  The  hydrograph generated for each treatment
represents  the  weighted  contribution to total
watershed flow. If the actual hydrograph from the
treatment (or prescription)  is desired,  the
hydrograph should be reverse weighted (multiplied
by watershed area/treatment or prescription area).

                    ALL
               SILVICULTURAL
               PRESCRIPTIONS
               CONSIDERED?
  At this point, a distribution of annual flow for
one prescription has been completed. All prescrip-
tions within an energy aspect must be completed
prior to looping an energy aspect.
            NEW ENGLAND/LAKE
                   STATES
                 REGION (1)
  The presentation of flow distribution is different
for  the  New England/Lake  States hydrographic
region (1) than for the other snow dominant regions
and provinces  because rainfall,  as  well  as
snowmelt, plays a dominant role in the hydrologic
cycle there.  For this reason,  the output from the
simulations  is presented  in flow duration curves
rather than  time  dependent distribution graphs.
The reasoning for using  one or the  other is ex-
plained  in appendix HLC.
                     ALL
                   ENERGY
                  ASPECTS
                CONSIDERED?
            BASELINE AND OPEN
          FLOW DURATION CURVES
  One energy aspect has been completed. To com-
 plete analysis for one condition, repeat for  all
 energy aspects.
                WATERSHED
                HYDROGRAPH
  Summation of the 6-day flow increments for each
silvicultural  state or treatment hydrograph  by
prescription and  energy  aspect yields  the com-
posite hydrograph for the condition. Since all  es-
timates of flow were area weighted, the hydrograph
values are additive.
  As in the other regions and provinces discussed
here, simulations for a number of water years were
made under fully forested baseline conditions, un-
der a 50-percent reduction in cover density, under a
60- and 90-percent cover density, and under a fully
open condition. The baseline flow duration curves
for the New  England/Lake States hydrographic
region are presented in figure  111.74. Peak flows
were simulated to be slightly greater on the low
energy (north) aspects due to a  more concentrated
melt period. Simulations were not sensitive to any
aspect differences in potential low flows which
would come in both midwinter and late summer.
  The procedure for modifying the flow duration
curve is a modification of the technique presented
                                             III. 120

-------
for the rain dominant hydrologic regions (2, 3, 5, 6,
and 7). Baseline and open potential streamflow are
determined  with  techniques  presented  in  the
streamflow analysis for rain dominated regions.
  If  the  calculated  potential baseline flow differs
from that presented in figures 111.75 to 111.77, replot
the flow  duration curve. A number of points  along
the flow duration curve should be read and the flow
(y axis)  should be multiplied by  the  ratio of ex-
pected site specific baseline annual flow to annual
flow represented by flow duration curve. The new
flow (y)  is then replotted  at the same  duration.
This will yield a new flow duration curve adjusted
for the difference in potential baseline flow during
the year of silvicultural activity and the normalized
year presented in this  handbook.
  The baseline flow procedure is repeated for open
conditions. Worksheet  El. 3 of the section on rain
dominated regions is helpful for these calculations.
                                                            3.0
      2.5
      2.0
      1.5
    Q
    
-------
                25        50        75
             PERCENT OF TIME FLOW IS EXCEEDED
                                           100
Figure
  the
  (D-
III.77.—Potential excess water flow duration curve for
New England/Lake  States  hydrologic region
treated conditions, high energy aspects.
melt) flows becomes more apparent. Interpolation
between calculated baseline and calculated open
flow duration curves will give the flow duration
curve for the silvicultural activity condition. This
is an arbitrary interpolation. Guidelines for inter-
polation are implied by figure El.77.
                      END
  Watershed hydrographs or flow duration curves
for all conditions have now been calculated.
  Example: Determining Streamflow Timing
          And Volume Changes With
      Silvicultural Activities, Excluding
          "New England/Lake States
                  (Region 1)"


  The following illustration presents a  stepwise
procedure for  application  of the methodology for
Region 4 and Provinces 5, 6, and 7.
  Directly following this procedural discussion are
examples of worksheets DI.7 and III.8. They are il-
lustrative  of the data required for completing the
methodology.
                                                       Step  1.  Using  appropriate  figures  and
                                                       worksheets HI.5 and IE.6 as guides, calculate the
                                                       annual  potential  streamflow  by silvicultural
                                                       state for both existing and proposed conditions.
                                                       Assume the area of the watershed is 100 acres.
                                                       Annual potential  streamflows have  been  area
                                                       weighted.  A typical result is shown below.
Existing condition
Silvicultural
activity
Forested impacted
Forested unimpacted
Clearcut
Partial cut
Excess
water
(in)
12
15
20
0
Watershed
area
represented
(%)
.200
.600
.200
0
Weighted
excess
water
(in)
2.4
9.0
4.0
0
                                                Total flow
                                                from watershed
Forested impacted
Forested unimpacted
Clearcut
Partial cut

 Total flow
 from watershed
                                                                                        15.4
                                                                             Proposed condition
12
15
20
16
.250
.175
.450
.125
3.0
2.6
9.0
2.0
                                                                                       16.6
                                                 Step 2.  This step applies to the Rocky Moun-
                                                 tain/Inland Intermountain hydrographic region
                                                 (4) only. The date on which the peak snowmelt
                                                 flow  will  occur  must  be  known.  Mark  the
                                                 digitized  excess water  distribution  graph
                                                 (baseline only). Peak flow rate is represented by
                                                 the  largest  flow  percentage  in  the baseline
                                                 column of tables III.ll to HI.13. Once the date of
                                                 the expected peak has been established, dates of
                                                 the other components can also be established in
                                                 6-day increments.
                                                 Step 3.  Select the appropriate digitized excess
                                                 water distribution from tables III.ll to III.22.
                                                 Enter baseline  values for forested unimpacted
                                                 and forested impacted silvicultural activities in
                                                 worksheet III.7, columns (4) and (10). Repeat for
                                                 clearcut (open)  values  in column (10). Inter-
                                                 polate between open and  baseline distributions
                                                 to obtain the partial cut digitized distribution.
                                                 Enter the partial cut distribution in column (16).
                                                 Repeat this procedure as necessary until existing
                                                 and proposed conditions are considered. If the
                                                 watershed  has been divided into subunits based
                                                 on energy aspect, repeat the procedure for each
                                                 subunit.
                                                 Step 4. Multiply each silvicultural  state  dis-
                                                 tribution graph value by  its corresponding an-
                                                 nual potential streamflow for that state. Enter
                                               EI.122

-------
  the products in the "inches" column for each
  state.
  Step  5.  Convert "inches" into cubic feet per
  second (cfs) using the formula —

(cfs) =
       (inches) (watershed area in acres)	
     (12 in/ft) (1.98) (number of days in interval)

                                        (in.16)

  Step 6. For each interval on each worksheet add
  (cfs) columns for all silvicultural  states.  Enter
  the  sums  in  column  (19). The  composite
  hydrograph is  given  in  column  (19).  If the
  watershed has been divided into subunits, each
  subunit composite  hydrograph is weighted by
  subunit percent of total watershed area. Existing
  and  proposed  condition hydrographs are
  calculated separately.

  The preceding methodology assumes that the ef-
fect of increasing the  amount  of vegetation
removed is linear. This is not generally true since
only two points were simulated — no response and
full response; it is impossible to make an interpola-
tion other than linear. Any error due to this would
probably result in overestimating the impact of les- '
ser  activities. This has a conservative effect on the
estimations.
                                              m.123

-------
PROCEDURAL DESCRIPTION: DETERMINING SOIL MOISTURE CHANGES
                   AND INDIVIDUAL EVENT  STORM RESPONSE
  Earlier sections of this chapter have emphasized
changes  in  6-  and  7-day intervals  for  either
evapotranspiration, soil moisture,  or  water
available for flow. Responses to individual  events
— primarily storm runoff — were not dealt with.
This section now addresses that issue.
  The methodologies already  developed assume
that water infiltrates into the undisturbed forest
floor, but there are  exceptions. Two factors as-
sociated with stormflow production can be altered
by  silvicultural  activities:  (1)  The infiltration
characteristics of the surface, and (2) alteration by
disturbance  of the  storage capacity in the soil.
(Distribution and melt rate of winter snowpack can
also be affected by tree removal. Changes in both
the amount and melt rate of the pack can cause
either the infiltration rate or storage capacity of the
soil  profile to  be exceeded; this,  in turn,  causes
higher peak flow rates.  This  occurrence  is not
treated  as  storm   runoff, however,   but  was
previously treated as flow change.)
  To address  the first factor,  most conventional
silvicultural practices, excluding site preparation,
do not significantly disturb the soil surface,  except
for the access and decking systems. These systems
have the  potential for changing slope hydrology in
that subsurface  soil  water is intercepted by road
cuts and routed over the surface along with the rain
falling directly on these surfaces. There is a  poten-
tial for altering the timing and delivery route to the
channel of 10 to 15 percent of the precipitation. The
impact of this potential on the storm hydrograph
can  be expected to be variable —  the stormflow
peak and volume may or may not be increased by
water from the access system. This depends on how
the rerouted water enters the system. The net effect
can be to reduce or augment the peak,  depending
upon normal basin response. However, consistent
with best management  practices,  if the  access
system is properly designed, laid out, and drained,
then the  intercepted water should be distributed
back over the  basin  surface and allowed to rein-
filtrate into the soil mantle (provided that storage
is available). This minimizes  the  impact on the
hydrograph.
  To address the second factor, the most signifi-
cant impact that silvicultural  practices can have
on stormflow is their effect on antecedent storage.
As will be shown in the discussions on soil moisture
deficits, as the intensity of cut increases, the deficit
or storage capacity at any point in time decreases.
With less storage capacity, more of the precipita-
tion appears as stormflow.
   Much of the potential for non-point source pollu-
tion associated with silvicultural activities is as-
sociated with individual storm events. The impact
is not only as stream power as a function of volume
and peak flow rates, but also as the opportunity for
sediment  delivery. Therefore,  the  hydrologist or
engineer usually  needs to evaluate the expected
response to some "design" storm.
   The general purpose of the hydrology section is to
present  a  methodology  for estimating   the
hydrologic impact of  silvicultural activities, in-
cluding impacts on storm response. However, the
state-of-the-art in hydrology does  not allow  the
presentation of a  regionalized,  process-oriented
methodology for evaluating the impact, if any, of
site disturbance on the storm hydrograph.

  Instead a qualitative  evaluation will have to be
made based on how, when, and where  the distur-
bance will be made, and how such disturbances
might affect the hill slope hydrology.
  If the pathway water takes to the channel is  not
altered by the silvicultural activity — and there is
little reason  to  believe it will be if best manage-
ment practices are followed — then the only other
impact which can occur will be a reflection of the
change in soil moisture storage capacities.
  The  problem  of flood  forecasting  is twofold.
First, the  impact silvicultural activities can have
on  the soil  water regime  should  be  evaluated;
secondly,   techniques  for  predicting   stormflow
should be discussed. If the primary interest is in
the potential for change, then the soil water evalua-
tion discussed next will define those periods when
significant changes can occur. Subsequent develop-
ment will  allow design storm selection.
  Like the  other procedures,  the  soil water
methodology varies by region, primarily because of
the nature of the model  output. Once the moisture
status has been determined, the applications of the
stormflow prediction procedure would  be similar,
although the relative weight of design criteria may
vary by region.
                                              in. 124

-------
        SOIL MOISTURE CHANGES
HUMID  CLIMATES,  (RAIN DOMINATED
    REGIONS) PACIFIC COAST REGION,
              LOW ELEVATION
             (PROVINCES 5, 6, 7)
     APPALACHIAN MOUNTAIN AND
          HIGHLANDS (REGION 2)
GULF  AND ATLANTIC  COASTAL  PLAIN
              AND PIEDMONT
                 (REGION 3)


  Dealing adequately with soil moisture depletion
rates and deficits is more difficult in a handbook
based  on  regions  than  is  dealing  with either
evapotranspiration  or the  potential  streamflow.
Both evapotranspiration and  streamflow follow
seasonal patterns,   and  they  have  predictable
regional  relationships. Soil moisture follows the
same general  pattern;  however,  soil moisture
deficits  (or differences in deficits between sites of
pre-  or post-silvicultural  activity)  can  be
eliminated in a single storm event at any time
without any obvious reflection in evapotranspira-
tion or flow.
  In this instance,  the technique used to predict
the  soil  moisture  distribution is by simulation;
other researchers have used different techniques.
Troendle (1970), Patric  (1974), and  others have
presented results of studies investigating baseline
and observed changes in soil moisture following
various  cutting practices. Tichendorf  (1969),
Helvey  and  others  (1972),  Kochenderfer  and
Troendle (1971), and others have developed predic-
tion equations to estimate soil moisture as a func-
tion of descriptive parameters such  as position on
slope, aspect, basal area, soil factors,  and antece-
dent rainfall.  These local techniques, if applicable,
may be better for defining a site specific baseline
soil moisture  level than the normalized curve to be
presented. Like  the expected flows, what  is most
important is not necessarily the absolute value, but
the ability to adjust the soil moisture level ap-
propriately to evaluate the  potential  impact of a
proposed activity.
  Seasonal  deficits  in  soil  moisture  (or  soil
moisture storage capacity) for a particular region
should be estimated from figures El.78, HI.79, or
111.80 directly.  Then,  for the proposed activity,
determine the modifier coefficient, by season, from
figure 111.81, 111.82,  or  HI.83.
  Multiplying  the  modifier  coefficient  by the
baseline deficit will give the expected post-activity
 level. The difference between the pre-activity and
 post-activity deficit is the change that can be ex-
 pected as a result of the activity. By the same
 token, the  pre-activity level for any past history
 can be determined by adjusting the baseline curve
 for present stand conditions. Figures 111.78 to 111.80
 represent  the  average  simulated  soil  moisture
 deficit for the  root zone in each of the regions.
 Although  figures  III.78 to  111.80  have  been
 smoothed, the deficit at the end of the four seasons
 has  been plotted.  It should  be kept in  mind,
 however, that these represent average conditions
 which could be modified or eliminated at any time
 by a single storm event.
   Modifier  coefficients  (figs. 111.81 to 111.83) are to
 be applied to the baseline deficit extracted in order
 to adjust for various levels of leaf area index. These
 are representative curves and will give an index to
 the change  in antecedent moisture that can be ex-
 pected  as  a result of  the  proposed activity.
 Although the effect varies with  storm size, soil
 depth, and available storage capacity, antecedent
 rainfall can eliminate the deficit at any time; dis-
 cretion must be used in evaluating whether or not
 conditions may be wetter or drier than "normal."
   Adjustments  in the  baseline  or  existing soil
 moisture deficit can also be made  for  differing
 rooting or soil depth. The changes in  evapotran-
 spiration resulting  from altering rooting depths
 were almost a direct reflection of the changes in soil
 moisture storage. Therefore, the deficits expressed
 in figures in.78 to HI.80 can be adjusted for differ-
 ing depth by multiplying the appropriate deficit by
 the modifier coefficient expressed in figures 111.81
 to m.83.

  In the southern Appalachians, soils are deeper
(in excess of 6-8 feet) than in the rest of the region,
and the soil moisture distribution is more like that
of the Coastal Plain/Piedmont region. Therefore,
figure  III.80 may be substituted for figure ni.79,
and figure m.83 for figure HI.82. This will allow an
estimate of the baseline distribution and  post-
activity relationships for the generally deeper soils
in the southern Appalachians.
  The simulations  indicate (as  did the observa-
tions  reference)  that aspect and, to some extent,
latitude did affect the soil water deficits. However,
the error associated with predicting them is such
that the site  specific effect cannot be isolated.
Basically, simulated deficits appeared greater on
southerly aspects and in more southerly locations
than on northern aspects and locations.
                                              m.125

-------
      +10:
    «.  -5
    O -1
    ui    -
    O -15
    cc
    H -20
    O    =
    w -30
       -35:
       -40 d
                  SPRING
 SUMMER
FALL
WINTER
         Figure 111.78.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the
           Pacific Coast hydrologic provinces—Northwest (5), Continental/Maritime (6), and Central
           Sierra (7).
                                                                                     WINTER
     Figure 111.79.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the Appalachian
                             Mountain and Highlands hydrologic region (2).
u+10.
O
u_
LU

S   °i
LU
CO
               SPRING
SUMMER
  FALL
     WINTER
     Figure 111.80.—Average simulated soil moisture deficit, root zone only (upper 3 feet), for the Eastern Coastal
                               Plain and Piedmont hydrologic region (3).
                                               III.126

-------
1.2 —
•] "1
1.0 -
in
z '9
ai
r o
U_
LU
0
07
oc
UJ
"- e
D '"
O
5
DC
D
ft ,
0 ~
-J o
o -3
CO
2 —







/
.»"
/
/
/
/
/
/
f
/
/
/




.•* *
/
/
/
/









	 1'






















•
















	 4,..








•_












Summer
Fall
Winter & Sp












'ing



                        10
                                   15         20         25
                                        LEAF AREA INDEX
                                                                   30
                                                                              35
                                                                                         40
Figure 111.81 .—Seasonal soil moisture deficit modifier coefficients for the Pacific Coast hydrologic
         provinces—Northwest (5), Continental/Maritime (6), and Central Sierra (7).
-] -\

9

H -8
HI
O 7
uZ
LL.
UJ
° R
0 '°
DC
HI
LL 5
5
0
2 4

0 ,_


c










x'
/y
)








/
/









/
/
r'



;




X
/






-



^/"
'







i


^^







— •


;


^ "^





Winter & Sp
Summer & 1


3








ing
:all


' 8
                                      LEAF AREA INDEX

Figure 111.82.—Seasonal soil moisture deficit modifier coefficients tor the Appalachian Mountains
                           and Highlands hydrologic region (2).
                                        m.127

-------
          z
          LLJ
          g .7-
          LL
          LL
          LLJ
          O 6-
          O
          o:
          HI
          t -5-
          Q
          O
                                                                        Summer
                                                                        Winter & Fall
                                                                        Spring
                                                             5
                                              LEAF AREA INDEX

             Figure 111.83.—Seasonal soil moisture deficit modifier coefficients for the Eastern Coastal Plains
                                   and Piedmont hydrologic region (3).
        SOIL MOISTURE CHANGES
   (SNOWFALL DOMINATED REGIONS)
NEW ENGLAND/LAKE STATES (REGION 1)
ROCKY  MOUNTAIN/INLAND  INTER-
          MOUNTAIN (REGION 4)
PACIFIC  COAST,  HIGHER  ELEVATION
                    ZONES
             (PROVINCES 5, 6, 7)
  In the  Rocky  Mountain/Inland Intermountain
hydrologic region (4), baseline soil water require-
ments for conditions of full hydrologic utilization
are plotted in figure HI .84 for each of the three
seasons discussed. Baseline relationships plotted in
figure  111.84 represent  recharge requirements for
moderate depth  soils (which  have 5.5 inches of
water  holding capacity).  For deeper  soils  (water
holding  capacity greater than 10  inches),  the
recharge requirements  in figure 111.84 should be
multiplied by the following coefficients:
Table 111.23.—Soil moisture adjustment coefficients for the Rocky
Mountain/Inland Intermountain  hydrologic  region  (4)  by
             aspect/elevation and season
Aspect
High north
Intermediate
Low south
Feb. 28
1.0
1.4
1.7
June 30
1.0
1.2
1.3
Sept. 30
1.0
1.2
1.4
Adjustment coefficients for soils  having between
5.5 and 10 inches water holding capacity can be ap-
proximated by interpolation. To adjust the deficit
for deeper soils,  multiply the deficit from figure
m.84 by the coefficient listed above (table HI.23)
(or the interpolated coefficient).
  Figures ni.85 to in.87 depict the baseline as well
as the 50- to 100-percent reduction  soil moisture
levels for the high north (ffl.85), low south (IH.86),
and intermediate  (111.87) positions.
  In  the  Continental/Maritime Province  (6),
baseline soil water recharge requirements for condi-
tions  of full hydrologic utilization are  plotted  in
figure  111.88.
                                                III.128

-------
+1.00
                                                                          High North
                                                                          (Low Energy)
                                                           Low South
                                                           (High Energy)
 -6.00
      Oct. 1
Feb
June 30
 Sept. 30
                                                DATE
        Figure III.84.—Baseline soil water requirement relationships for the Rocky Mountain/Inland Inter-
                               mountain region (moderate soil depth).
  +1.00
  -6.00
       Oct. 1
 Feb. 28
 June 30
                                                    DATE
Sept. 30
        Figure 111.85.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
                    Intermountain hydrologic region (4)—low energy aspects (high north).
                                            m.i29

-------
    +1.00
     0.00
-  -1.00-
H

LLJ
LU
gc
u
o
LU
GC
01
O
CC
<

O
W
DC
    -2.00
-3.00 -
-4.00
    -5.00 -
    -6.00
         Oct.  1
                                       Feb. 28
                                            DATE
 June 30
 Sept. 30
          Figure  111.86.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
                     Intermountain hydrologic region (4)—high energy aspects (low south).
   +1.00
    -6.00
         Oct.  1
                                       Feb. 28
                                                     DATE
June 30
Sept. 30
          Figure 111.87.—Seasonal soil moisture recharge requirements for the Rocky Mountain/Inland
                        Intermountain hydrologic region (4)—intermediate energy aspects.
                                                m.iso

-------
       +1.00
                                                                                 Low Energy
                                                                                 (High  North)
          High Energy
          (Low South)
       -6.00
           Oct. 1
Dec. 31
March 31
DATE
June 30
Sept. 30
             Figure 111.88.—Baseline seasonal soil moisture recharge requirements for the Continental/
                             Maritime hydrologic province (6)—all energy aspects.
  Changes in soil water status due to silvicultural
activities  can  be estimated from figures III.89 to
ni.91. Reductions of maximum forest cover density
(Cdmax)  to Cdmax/2  by  selection  cutting will
not  appreciably alter the  baseline  soil  water
regime. However, recharge requirements should be
decreased uniformly between Cd = Cdmax /2, and Cd
=  0. Figures  ffl.89 to 111.91 should be used for
moderate  soils  (approximately 3.5 and 5.5 inches
field capacity). For deeper soils (approximately 10
inches  field  capacity),  recharge  requirements
should be multiplied by the following coefficients:
Table 111.24.—Soil moisture adjustment coefficients for the
       Continental/Maritime hydrologic province (6)
            by aspect/elevation and season
Aspect
High north
Intermediate
Low south
Feb. 28
1.0
1.4
1.7
June 30
1.0
1.2
1.3
Sept. 1
1.0
1.2
1.4
                        Changes in soil water status due to silvicultural
                      activities can be  estimated from figures 111.93 to
                      111.95. Reductions of maximum forest cover density
                      (Cdmax)  to  Qmax/2 by selection  cutting  did not
                      appreciably alter the baseline  soil water  regime.
                      However,  recharge requirements  should  be
                      decreased uniformly between Cd = Cdmax/2, and Cd
                      = 0. Figures IH93  to 111.95 should be used  for
                      moderate  soils (approximately 5.5  inches field
                      capacity). For deeper soils (approximately 10  in-
                      ches  field  capacity),  recharge requirements  in
                      figures 111.93 to III. 95 should be multiplied by the
                      following coefficients:
                       Table 111.25.—Soil moisture adjustment coefficients for the
                       Central Sierra hydrologic province (7) by aspect/elevation and
                                            season
Adjustment coefficients for soils having between
5.5 and 10 inches water holding capacity can be ap-
proximated by interpolation.
  In the Central Sierra province (7), baseline soil
water recharge requirements for conditions of full
hydrologic utilization are plotted on figure 111.92.
Aspect
High north
Intermediate
Low south
March 29
1.1
1.4
1.0
June 27
1.0
1.2
1.7
Oct. 1
1.0
1.2
1.3
Dec. 30
1.0
1.2
1.4
                      Adjustment coefficients  for soils having between
                      5.5 and 10 inches water holding capacity can be ap-
                      proximated by interpolation.
                        In  the  Northwest  hydrologic  province (5),
                      baseline soil water requirements for conditions of
                                                 m.131

-------
   +1.00
W
o>

o
c
    0.00
 - -1.00—
z
LU
2
LU
DC

D
O
LU

-------
+1.00
 -6.00
      Oct. 1
 Dec. 31
  March 31
DATE
 June 30
Sept. 30
        Figure 111.91.—Seasonal soil moisture recharge requirements for the Continental/Maritime
                            hydrologlc province (6)—high energy aspects.
+1.00
           High North
           (Low Energy)
                               Low South
                               (High Energy)
-6.00
     Oct. 1
Dec. 31
  March 31

    DATE
June 30
 Sept. 30
        Figure 111.92.—Baseline seasonal soil moisture recharge requirements for the Central Sierra
                            hydrologlc province (7)—all energy aspects.
                                            m.133

-------
+1.00
 -6.00
       Oct. 1
  Dec. 31
March 31
 June 30
Sept. 30
       Figure 111.93.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologic
                                 province (7)—low energy aspects.
+1.00
-6.00
    Oct. 1
Dec. 31
March 31
June 30
 Sept. 30
      Figure III.94.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologic
                            province (7)—intermediate energy aspects.
                                             ni.i34

-------
      +1.00
      -6.00
            Oct. 1
Dec. 31
   March 31
DATE
June 30
Sept. 30
             Figure 111.95.—Seasonal soil moisture recharge requirements for the Central Sierra hydrologlc
                                    province (7)—high energy aspects.
full hydrologic  utilization  are  plotted  on figure
in.96.  These curves  are proposed for use in the
high-elevation  coniferous forests  where runoff is
derived primarily from melting snow.
  Changes in soil water status due to silvicultural
activities  can  be estimated from  figures in.97 to
in. 99. Reduction of maximum forest cover density
(Cdmax)  to Cdmax/2 by selection  cutting did  not
appreciably alter the baseline soil  water regime.
However, recharge  requirements  should be
decreased uniformly between Cd = Cdmax/2 and Cd
=  0. Figures  in.97 to in.99 should be  used for
moderate  soils  (approximately 5.5 inches field
capacity). For deeper soils  (approximately 10 in-
ches field  capacity), recharge requirements should
be multiplied by the following coefficients:
Table 111.26.—Soil moisture adjustment  coefficients for the
Northwest hydrologlc  province (5) by aspect/elevation and
                     season
Aspect
High north
Intermediate
Low south
March 29
1.0
1.0
1.0
June 27
1.6
1.8
1.8
Oct. 1
1.8
1.8
1.8
Dec. 30
1.0
1.0
1.0
                        For the New  England/Lake States hydrologic
                      region (1), seasonal trends in soil moisture can be
                      shown by a nearly uniform temporal distribution of
                      precipitation  during the summer periods. Figure
                      HI.100 shows the baseline site specific soil moisture
                      relations. Note that the maximum deficit occurs
                      during the middle of August and is  less than 2 in-
                      ches. This relation generally will not change unless
                      very  shallow  and/or coarse textured soils are en-
                      countered.
                         Figures in. 101 to HI. 103 present the effects of
                      timber harvesting on soil moisture.  No significant
                      differences were  noted between  the  partial cut
                      (Cdmax/2) and the fully forested condition (Cdmax).
                      Reductions in  forest cover  density  of  over  50-
                      percent resulted in significant changes in the soil
                      moisture  deficit which  can be interpolated  from
                      figures m.101 to m.103.             ^
                        The soil moisture deficit patterns  discussed were
                      simulated and represent potential deficits, not ex-
                      act numbers. The relative relationships  between
                      cut and uncut seem reasonable and should give a
                      good  index to the expected change.
                                                m.135

-------
   +1.00-
    0.00-

0)
.c
o

~  -1.00—|
H
Z
LU

Lu  -2.00-
DC
D

2  -3.00 —
DC
LU
I
o
LU
    -4.00-
    -5.00 —
    -6.00.
           Oct.  1
                            Dec. 31
                                                                           High North
                                                                           (Low Energy)
                                                                  Low South
                                                                  (High Energy)
   March 31
DATE
                                                                      June 30
Sept. 30
         Figure  111.96.—Baseline seasonal  soil  moisture recharge  requirements  for the Northwest
                              hydrologic province (5)—all energy aspects.
   +1.00-
    0.00-
 CO
 CD
 O

~-  -1.00-

z
LU

Lu  -2.00
DC
D

2  -3.00 -|

LU
O
<  -4.00
I
O
LU
^  -5.00 H
   -6.00.
        Oct. 1
                                                                             Open
                                                                                  dmx/2
                                                                  (Baseline)
                            Dec. 31
                                                March 31
                                                DATE
                         June 30
Sept. 30
         Figure 111.97.—Seasonal soil moisture recharge requirements for the  Northwest hydrologic
                                  province (5)—low energy aspects.
                                              m.136

-------
  +1.00-
« o.oo.
0)
o
"-1.00 —
I-
LU
w
gc
D
O
   -2.00— •
   -3.00 -I
LL.
LU
O
< -4.00
I
O
LJJ
1 -5.00 —
   -6.00 •
            09'
        Oct. 1
                             Dec. 31
      March 31
   DATE
 June 30
Sept. 30
          Figure 111.98.—Seasonal soil  moisture recharge requirements for the  Northwest hydrologic
                               province (5)—intermediate energy aspects.
  +1.00
  -6.00
                                                                          V
       Oct. 1
                           Dec. 31
    March 31
DATE
June 30
Sept. 30
         Figure 111.99.—Seasonal soil moisture  recharge requirements for the  Northwest hydrologic
                                   province (5)—high energy aspects.
                                               m.137

-------
+1.00-
0 00
CO
o>
o
-E -1.00-
01
^ 9 no
rr
O
UJ -3.00 —
DC
01
CD
5 -400-
O
01
1 -5.00-


^
Cdmx





Oct. 1 Dec







. 31 Marc

^^





h 31 Jun<
Open

Cdmx





5 30 Sept. 30
DATE
            Figure 111.100.—Baseline  seasonal  soil moisture recharge  requirements  for the  New
                         England/Lake States hydrologic region (1)—all energy aspects.
  +1.00'
   0.00—Open
- -1.00-
LU
^
LU
CC
   -2.00-
o
oi -3.00—
cc
oi
  -4.00-
I
O
01
   -5.00—
   -6.00-
            •'dmx
       Oct. 1
                                                                           Open
                                                                                         'dmx
                           Dec. 31
March 31
DATE
June 30
Sept. 30
            Figure 111.101.—Seasonal soil moisture recharge requirements for the New England/Lake states
                                 hydrologic region (1)—low energy aspects.
                                                 III. 138

-------
   +1.00
 w  0.00 -

.c
 o
^c

H- -1.00-

LU

I -2.00-

D
O
LU
DC -3.00-
LLJ

DC
O
OJ
DC
    -4.00
    -5.00 —
    -6.00
              'dmx
         Oct. 1
                             Dec. 31
March 31
 DATE
                                                                                          dmx
June 30
Sept. 30
             Figure 111.102.—Seasonal soil moisture recharge requirements for the New England/Lake States
                              hydrologic region (1)—intermediate energy aspects.
    +1.00
«  0.00~T Open
^
o

(-' -1.00-

u
   -2.00-
O
   -3.00 —
LU
O

< -4.00-
I
O
LU
CC
   -5.00 '
                  'dmx
       Oct. 1
                             Dec. 31
                                                                                     dmx
                                                 March 31
                                                   DATE
                      June 30
                      Sept. 30
            Figure 111.103.—Seasonal soil moisture recharge requirements for the New England/Lake States
                                 hydrologic region (1)—high energy aspects.
                                                 III. 139

-------
     PREDICTING INDIVIDUAL STORM
                 RESPONSES
  It is beyond the scope of this handbook to recom-
mend a stormflow prediction technique for specific
application. There are too many local techniques,
which may be far superior to any generalized ap-
proach,  to   warrant  the  presentation of  a
generalized approach. It is recommended that the
technique best suited to a specific area be used. A
key criterion  for  selection,  however, should  be
whether or not the technique is sensitive to antece-
dent conditions. The whole basis for evaluating the
effect of  silvicultural  activities  on stormflow  is
through the  changes which occur in antecedent
conditions. Any technique not sensitive to antece-
dent conditions would  not reflect the  impact  of
silviculture.
  All  existing  methodologies  have  significant
predictive errors, so the absolute magnitude of the
event will contain  those  errors regardless of the
method. However, a reasonable technique sensitive
to antecedent conditions should give an adequate
estimate of change.
  One method,  although regional  in use,  is the  R
Index method (Hewlett  and others 1977), shown to
work well in the  East.  Another  method,  not
process-oriented but sensitive to antecedent condi-
tions, is the SCS method (Soil Conservation Ser-
vice 1973). Chow (1974) lists several other methods,
while McCuen and others (1977) present an an-
notated  bibliography  of  flood  flow  frequency
techniques.
  The point to remember in the stormflow analysis
is that the change due to silviculture will  equal or
be  less than the change in the soil water balance.
Any time the balance for pre- and post-silvicultural
activity conditions  is similar, so  will be the ex-
pected response  to individual events. By the same
token, response to precipitation events with greater
than a  1-year return period will become less af-
fected by treatment as the return period increases.
Most events capable of causing significant destruc-
tion will be unaffected or at least insignificantly so.
  Following is a very brief discussion of the major
consideration  in predicting individual  storm re-
sponses and in selecting the design event.
   Basis For Evaluating The Design Event
  Dealing with individual events within the con-
text  of this handbook is a twofold consideration.
First, there  is the  problem  of quantifying the
magnitude or frequency of the event; and second,
estimating the expected change  in that design
event due to silvicultural activities.
  From the outset, it should be noted that there are
two levels of flood design; that  is, one can design for
either major or minor projects. Major implies a risk
to human life. Minor implies no risk to life or limb.
From the  standpoint of silvicultural  activities,
design events are restricted to  minor projects only.
  There  are two  basic approaches for evaluating
the design  event.
  (1) An evaluation can be made of the probability
of equalling or exceeding a particular level of flow
or design flood. This can be done by performing a
flood frequency analysis on a historical flow record
for  the site. This involves the ranking  of various
levels of flow and the probability  associated  with
the probability of reoccurrence. Techniques for do-
ing this have been fairly well  documented (Water
Resources Council 1967).
  Two problems arise, however. First, one cannot
expect the historical record to  be  available  and,
second, if it were available, handbooks or empirical
methodologies would not be available for determin-
ing the impact that silvicultural activities have on
a particular event.
  The  alternative approach is  to  determine  the
hydrologic  response  expected  from  a design
precipitation or "input" event. This precipitation
input could be from  rainfall, snowmelt,  or rain on
snow. In doing  this,  the assumption is made  that
the reoccurrence interval for rainfall is the same as
the flood event  it produces. This is not necessarily
true, of  course, because the design precipitation
event may produce a runoff event with a frequency
of occurrence  less  than or greater  than  the
precipitation event causing it. Larson and Reich
(1973)  as well as  others, however, found that the
relationship did average out for small watersheds
in Pennsylvania.  They found  that over the long-
term record  the  average difference in  ranking
between return period for the precipitation event
and the  return  period for the  resulting flow event
was zero. The variability in response to  successive
events on the same basin is largely due to differing
antecedent conditions (Hewlett and others 1977) at
the time of the storm.
  The latter  approach,  or  design  based on
precipitation,  lends   itself well to a  stormflow
analysis  consistent with this  handbook. The soil
moisture distributions presented  provide  an es-
timate of antecedent conditions for both pre- and
post-silvicultural treatment conditions.
                                              III. 140

-------
  As noted, silvicultural activities require design-
ing for  minor projects.  Because of the relatively
small areas involved and the limited downstream
effect of silvicultural activities, the risks from in-
dividual events and the changes in them  due to
silvicultural activities are usually associated with
the likelihood of a local, onsite failure (such as ex-
ceeding a culvert or bridge capacity, washing out
roads or drainage  structures, exceeding channel
capacities, and  other failures due to excessive on-
site water).
Selecting The Return Period For  The  Design
                     Event
  Two factors need to  be considered  in selecting
the return period for the design event. The first is
the risk of failure that the planner is willing to ac-
cept during the life of the project. The second is the
expected life of the project or impact. The com-
bination of the acceptable risk of failure and ex-
pected  life of the  project combine to yield  the
return period for the design storm. Techniques for
doing this are defined in Chow (1964), as well as in
most other hydrology textbooks.
  Usually, the planner can accept a relatively high
risk of failure over a relatively short project life.
The result is  that the concern is usually with the
magnitude of the annual, the 5-, or the 10-year
event. It must be remembered that the impacts of
silvicultural  activities on  a particular  event are
really minimal in light of the variability between
individual events.
  Silvicultural activities can  significantly affect
frequent events of perhaps less than  1-year return
periods. They have minor, if any, effect on the an-
nual event and have an almost insignificant effect
on the 5- or 10-year event. Once  the antecedent
conditions for pre- and  post-silvicultural activity
conditions are equal, then the  potential for a
significant response due to activity is eliminated.
This  would be true  whenever the soil moisture
modifier coefficients presented earlier are unity.
       Selection Of Precipitation Input
  Once the  appropriate  design event  has been
selected, the precipitation input can be used from
onsite  data  by evaluating the return period; or, it
can  be  obtained  from  precipitation frequency
tables  for the region (i.e., USWB 1961).
                                               HI.141

-------
                                       CONCLUSIONS
  The  impacts  of silvicultural  activities  upon
potential streamflow can  be evaluated using
procedures for either the snowpack or  rainfall
regimes;  both procedures will  give an estimate of
the expected  change in flow. The form of the out-
put varies depending upon the methodology used.
This discrepancy presents little problem, however,
since both the distribution graph  and the  flow
duration  curve are acceptable,  useful means of dis-
tributing and interpreting expected potential flow.
  Estimates of potential flow (in area-inches)  may
be converted  to average daily  discharge (in cubic
feet  per second) and  used in  the total potential
sediment analysis (ch. VI).  The  estimate of dis-
charge represents the average discharge  for the
period of time determined by the duration curve in-
terval or by the dated intervals. In either case, the
basic simulation interval upon which all distribu-
tions and duration curves are based is either a 6- or
7-day estimate.
  Estimations of  the potential impacts  of a
proposed  silvicultural  activity  upon   potential
streamflow may be determined through use of the
procedures presented in this chapter. It is impor-
tant to combine such analysis with sound profes-
sional  judgment  and interpretation of the es-
timated impacts according to  inherent errors and
local conditions. Combining analysis with profes-
sional interpretation should result in a reasonable
estimate of the potential impacts of management
alternatives consistent with the current state-of-
the-art in hydrology.
                                              HI.142

-------
                                  LITERATURE CITED
American  Society of  Civil  Engineers.  1975.
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Anderson, E. A. 1976.  Snowpack energy  balance
  model:  National  Oceanographic  and At-
  mospheric Administration technical memoran-
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Anderson, H.  W.,  M.  D. Hoover,  and  K. G.
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Bailey, R. G. 1976. Ecoregions of the United States.
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Barr, A. J., J.  H. Goodnight, J. P. Sail, and J. T.
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Bates,  C.G., and  A. J. Henry. 1928. Forest and
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Baumgartner, A. 1967. Energetic basis for differen-
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Beasley,  R.  S. 1976. Contribution of subsurface
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Bouchet, R. J.  1963. Climatic significance of actual
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Brown, G. W.  1973. Measuring transmitted global
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Buckman, H.  0.,  and N.  C. Brady.  1966. The
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Chow, V. T. 1964. Handbook of applied hydrology.
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Colman, E. A.  1953. Vegetation and watershed
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Douglass, J.E. 1967. Effects of specie arrangement
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  hydrology. W. E. Sopper and  H. E. Lull, eds.
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Douglass, J. E., and W. T. Swank. 1975. Effects of
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  symposium proceedings. USDA For. Serv. Gen.
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  Stn.

Farnes, P. A. 1975. Preliminary report-suspended
  sediment  measurements  in  Montana.  Soil
  Conserv. Serv., Bozeman, Mont.

Federer, C.A. 1972. Solar radiation absorption by
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  20.

Forrester, J. W. 1969. Industrial dynamics. 464 p.
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Frank,  E. C.,  and R. Lee. 1966. Potential solar
  beam irradiation on slopes. Tables for 30° to 50°
  latitude. U.S. For. Serv. Res. Pap. RM-18,116 p.
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  lins,  Colo.

Freeland, F. D. Jr.  1956. The effects of a complete
  cutting of forest  vegetation  and subsequent an-
  nual  cutting off of regrowth upon some pedologic
  and hydrologic characteristics of a watershed in
  the  southern Appalachians.  Ph.D.  thesis.
  Michigan State Univ. 182 p.

Garstka, W. U., L.  D. Love, B. C. Goodell, and F.
  A. Bertie.  1958. Factors affecting snowmelt and
  streamflow. U.S. Dep. Inter. Bur. Reclam. and
  U.S.  Dep. Agric. For. Serv. 189 p.

Gay, L. W., K.  R. Knoerr, and M. 0. Braaten.
  1971.  Solar radiation variability on the floor of a
  pine  plantation.  Agric. Meteorol. (8):39-50.

Godell, B. C. 1967.  Watershed treatment effects on
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  Sopper and H. E. Lull, eds. p. 477-482.
  Pergamon Press,  N.Y.
                                             HI.143

-------
Goldstein, R.  A.,  and J. B.  Mankin.  1972.
  PROSPER:  a model  of  atmosphere-soil-plant
  water flow. p. 1176-1181. Proc. Summer Comput.
  Simul. Conf., San Diego.
Goldstein, R. A., J. B. Mankin,  andR. J. Luxmore.
  1974. Documentation of PROSPER: a model of
  atmosphere-soil-plant  water  flow. Environ. Sci.
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  75 p.
Green, R. E., and  I. C. Corey. 1971. Calculation of
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  some  predictive methods. Proc.  Soil Sci.  Soc.
  Am. 25:3-8.
Haeffner, A. D., C. F. Leaf, G. E.  Brink, and D. E.
  Sturges.   1974.  Hydrologic  model  of
  range/sagebrush lands. File Rep.  USDA  For.
  Serv.,  Laramie, Wyo.
Hamon,  W.R.  1961.   Estimating potential
  evapotranspiration.  Am.  Soc. Civ. Eng.,  J.
  Hydraul. Div. 87(HY3):107-120.
Harr, R.  D. 1976.  Forest practices and streamflow
  in western Oregon. USDA For.  Serv. Gen. Tech.
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  Range Exp.  Stn., Portland, Oreg.

Helvey,  J. D. 1971a.  A  summary  of rainfall in-
  terception by certain conifers of North America.
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                                              m.i47

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    APPENDIX III.A: EFFECT OF LARGE OPENINGS ON EVAPORATION
                       AND TRANSPORT OF BLOWING SNOW
  The technical basis for low snowpack retention in
large openings  is derived from Tabler's ongoing
studies on the evaporation and transport of blowing
snow. Tabler surveyed snow accumulation patterns
in and around numerous large clearcuts in Wyom-
ing (Tabler 1975).  His most  recent results, in-
dicating seasonal snow accumulation patterns as-
sociated with large open areas  (diameters > 15H)
(H = height of surrounding trees in feet) are shown
in figure III.A.I.1

  Figure III.A. 1  shows  a total  of four zones that
must be analyzed to determine impacts from clear-
cutting large blocks:
  Zone I    —A 5 to 7H lee drift on the windward
           margin
  Zone II   —A wind-exposed scour or  fetch area
           of indeterminate length
  Zone HI  —A  IOH  windward drift  on the
           leeward margin
  Zone IV  —A drift on the leeward margin whose
           length is given by the equation:
                LIy » 5H + 3Q/H
  where:
  Q   = Total snow transport off the clearcut area
        (D) in ft3 water equivalent/foot of width
        normal to  the prevailing wind

  H   = Height of surrounding trees
  'Personal communication with Dr. Ronald D. Tabler, Rocky
Mountain Forest and Range  Experiment Station, Laramie,
Wyoming.
           Zone I
     Wind
                               Zone II
                                    8
                                                     Tabler has proposed equations  for quantifying
                                                   seasonal snow accumulation in each of the four
                                                   zones. These equations are summarized in Table
                                                   m.A.i.
                                                     The terms in figure III.A. 1 and table HI.A.I are
                                                   defined as follows:
                                                     H   = Height of surrounding trees
                                                     D   = Clearcut diameter in feet (or width in
                                                           direction of wind)
                                                     Pa   = Precipitation water equivalent in feet
                                                     a)   = A  coefficient which indexes the amount
                                                           of  over  winter  snowpack  ablation
                                                           (perhaps 0.2)
                                                     5    = Roughness (slash or regeneration height,
                                                           etc.) in  feet
                                                     Q   = Total snow transport off the clearcut area
                                                           (D) in ft3  water equivalent/ft of  width
                                                           normal to the prevailing wind

                                                     The total water equivalent  transport off the
                                                   clearcut  block in ft3/ft can be computed by the
                                                   equation:
                                                   Q =  5000/U + 250 —a)| J0.87P;,  - 0.26
                                                                       H  -i *•

                                                         + (0.13P.,  - 0.155) a + (0.355 - 2P3/3)b
                                                         - P3c/3]
                                                   where:        IOH
                                    (EI.A.1)
                                                     a   =  0.14
           10,000
           D-5H

b   =0.14 10'000
            D
                                                                10,000
U-5-7H-J
1
1
f Id — 1fiH --*-* -. . -I
8 -|
I
«-LIVa:5H + 3Q/H-t
            Figure III.A.1.—General pattern of snow accumulation in large clearcut blocks (Tabler 1977).
                                             m.148

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                               Table III.A.1.—Summary of equations for quantifying
                                 snow accumulation In large clearcuts (D > 15H)
              Zone
Parameter
Equation
                           Drift length

                           Max. snow aeptn

                           Precipitation retained
                           Precipitation relocated
                           Snowpack density
                           Effective length
                           Max. snow depth
                           Precipitation retained
                           Precipitation relocated
                           Snowpack density
                           Drift length

                           Max. snow depth
                           Precipitation retained
                           Precipitation relocated
                     L,= 5H

                     DMX| = 3.33P,

                    .Pi = (2/3) Pa

                     fl, = Pa/3

                    TSI ' '35
                     LM = D-15H
                     PII = 0.355

                     flu = O.SPa - 0.356 (assuming w = 0.2)

                     TSII = -35

                     LI,,* 10H

                     DMXIII * 0.3D MX|V= 0.35H

                           + 0.20Hlog1Q
                                   1
                    PHI*   0.07H+0.04Hlog10
                     flu, * Ps - 0.07H + 0.04Hlog10
           UlH«     )

            fQ + pM
            \8.1H2     /
Snowpack density
IV Total drift length
Max. snow depth
Location of max. depth
Deflation distance
(fig. III.A.2)
Snowpack density
Tsui * -40
L|V * 5H + 3Q/H
DMXIV" 1.18H + 0.65Hlog10
1 * 5H
d * 2H
TSIV* -45 '"•
/Q + PaLlv\

   According to Tabler, there is, as yet, no accep-
 table method  for  estimating the contribution of
 Zone IE to the total snow transport Q. Reasonable
 estimates for Q are obtained by assuming no net
 contribution by Zone III (neither + nor —), leaving
 a simplified version of equation HI.A.I:

 Q  *  5000 [(P:, - .356) (a - b) + (P:,/3) (b - c)]
  Ignoring over-winter in-situ ablation (o> = 0.0)
and where terms are defined as above, if w were in-
cluded,

Q  * 5000 [(P3 - wPs - .356) (a  - b) + (1/3)
                       (b  - c)]
                       Evaporation losses are computed from the equa-
                     tion:

                     Q,oss = P.^D  -  1.53Q  -  4.67P3H  -  0.355D
                                        + 3.255H             (III.A.2)
                       Equation III.A.2 can be changed in accordance
                     with the suggested revision of in.A.l, or (assuming
                     w = 0.0):
                     Qlos8~ P3(D - 10H) - Q - .355 (D - 15H)
                            - 10P3H/3                        (m.A.3)
                       Figures  III.A.2  through  III.A.5  by Tabler
                     graphically show the effects of large clearcuts in
                     Wyoming. Undesirable impacts include not only
                     reduced snow accumulation,  but also damage to
                     the residual forest from wind and excessive snow
                     accumulation in Zone IV.
                                                 HI.149

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5
H
g
                                                                                             Figure III.A.2.—Cinnabar Park, Medicine Bow National Forest
                                                                                               (elev. 9,600 ft). Origin  of park  la unknown, but may have
                                                                                               resulted from fire In young stand of lodgepole pine. A. Wind left
                                                                                               to right. Maximum width of park Is about 2,000 ft. B. Wind left
                                                                                               to right.  Corridor  or "snowglade" Is kept  clear of trees by
                                                                                               snowdrift. C. Drift has maximum depth of about 35 ft.

-------
01
                                                                                                Figure  III.A.3.—Snowglades forming  downwind  of  clearcut
                                                                                                  blocks on the Medicine Bow National  Forest. This 45-acre
                                                                                                  block was cut In 1967,  with slash wlndrowed and burned in
                                                                                                  1968. (Elev. = 10,000 ft; width parallel to wind—1,800 ft.) A.
                                                                                                  Very little snow is  retained on the clearcut—about 90% of
                                                                                                  winter precipitation Is blown oft. B. Snowdrift Is 50 ft deep. C.
                                                                                                  Damaged trees result In snow glade.

-------
                                                                                                 .
 Figure Ml.A.4.— Residual limber on downwind side of clearcut shown in fig. III.A.3. Late-lying
  snowdrift keeps soil saturated throughout summer, making trees more vulnerable to windthrow.
  A. Windfall was salvaged in 1974 in a strip 100 to 200 ft wide on downwind side of block.  B.
  Windfall between clearcut and glade accumulated since 1974 salvage. This view looks directly
  into wind.
Figure III. A.5.—Windfall on lee side of 1972-73 clearcut. Wind is channeled into "corner" by forest
                                        margin.
                                        ffl.152

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                    APPENDIX III.B:  HYDROLOGIC MODELING
               PHILOSOPHY
  Because  of  lack of sufficient  data from  ex-
perimental watersheds and the resulting inability
to characterize universal process response from the
experimental data available, process simulation
has been chosen as the  basis for  quantifying the
hydrologic  impact. "Process"  quickly  became  a
keyword in this effort and led to an important deci-
sion in the modeling effort — that physically based
process models were to be used  wherever possible
rather than probalistic or stochastic models.  Ex-
isting physically based mathematical models were
evaluated as part of an earlier Forest Service/EPA
contract EPA-600/3-77-078.
  Mathematical  modeling,  or  the  objective
analysis  of  the  information-feedback
characteristics  of  hydrologic  systems, provides
criteria  for  estimating  system hydrology, since
system  structure,  delay,  and  amplification  are
taken into consideration. This modeling process re-
quires six basic steps as summarized by Jones  and
Leaf (1975):
  (1)  Construction of a dynamic mathematical
      model  in  which   important interactions
      between system components are defined.
  (2)  Programming and  execution  of the model
      over a period of time  on a digital computer.
  (3)  Comparison of model results against all per-
      tinent available data. (The  regional  ap-
      proach can  be effectively used  for model
      validation.)
  (4)  Revision (tuning) of the model until it is ac-
      ceptable as  a  representation  of the actual
      system.
  (5)  Alteration  of certain  model components in
      order to represent changes in the real system.
  (6)  Repeat of step 3 to verify the  "tuning" and/or
      model alteration.
  At each step in the above sequence, the previous
steps often need to  be revised. The whole procedure
is not unlike the  development of an aircraft or
automobile, where repeated design changes  and
testing  ultimately  result in an operational
prototype.
  However, all models are,  in one  way or another,
imperfect and simplified representations of reality;
there are limitations in the modeling approach. Ac-
curacy and validity of any model is  not absolute
and has a meaning only relative to some prescribed
use. Consequently, subjective  judgment is neces-
sary in selection,  use and application; error is in-
herent in both the judgment made and the result
obtained. Errors in simulation may appear great,
but, given the present state-of-the-art, there is no
other way  of quantifying a  universal response
which can be interpolated to site specific applica-
tions.
  Bear in mind that the danger in any quantitative
model-validation  procedure is  that it takes on an
"aura of authenticity"  and may lead the inex-
perienced modeler to forget the underlying subjec-
tive assumptions. Primary confidence in modeling
must depend on:  (1) how acceptable or plausible
the model is in describing natural  processes, and
(2)  the reasonable assumption that  "if all the
necessary components are adequately described
and properly interrelated, the model system cannot
do other than behave as it should" (Forrester 1969).
Because much of the content  of complex natural
system  models is derived from nonquantitative
sources, the defense of  such  models ultimately
must rest in careful subjective evaluation of their
performance by experienced professionals who are
familiar with these systems.
  In practice, the utility of  a model  lies  in its
ability to precisely represent  overall behavior of
natural systems and system response to changes in
one or more system components.
   SELECTION OF THE MODELS USED
  Several criteria  were used  in  selecting  ap-
propriate models.
  An examination and evaluation were completed
on the structure of the models themselves, the
parameters  used,  and the  means  by which
parameters  were  estimated. Models  that  were
process-oriented  were  isolated;  those  that  op-
timized parameter  estimates to the point where
                                              EI.153

-------
 they no longer represented real-world inputs were
 eliminated. In addition, those models having in-
 herent feedback to the calibration phase which,
 much like optimizing, detracted from true process
 response were also eliminated. Adequate documen-
 tation, referenced applications, and contact with
 experienced  users  were  relied upon  heavily.
 Selected models were process-oriented and did not
 violate assumptions when in use. Finally, models
 were selected according to the level of expertise, the
 time frame, and the data base available.
   After model selection, the second phase involved
 testing and fitting the selected models to represen-
 tative  and  experimental  watersheds,  evaluating
 their range of applicability, and evaluating their
 performance with respect to known responses.
   The EPA/FS  Phase  I  study (1976) reviewed
 several  models  developed for forest  hydrology.
 They varied widely in  terms  of complexity  and
 scope,  depending on their application. Most were
 based on a practical engineering approach which
 achieved a balance between theory, available data,
 and operational objectives and  constraints.  The
 successful application of each model depended to
 some extent on empirical derivations of several
 parameters and relationships, some of which were
 unique to geographic areas.
   Based  on all the criteria and assumptions men-
 tioned,  two  models were  selected as the most
 readily  useful:  The  Subalpine Water  Balance
 Model (WATBAL)  developed by Leaf and Brink
 (1973b)  and  PROSPER  (Goldstein  and others
 1974).
   Other  models may have been equally suited,
 however, the two selected models best fit the re-
 quirements  of  this  handbook.  It  should  be
 emphasized that it was  not an object of the selec-
 tion process to promote any specific model.
GENERAL PRINCIPLES FOR APPLICATION
           AND USE OF MODELS
 Subalpine Water Balance Model Description
  The  Subalpine Water Balance Model (WAT-
BAL) was chosen because it had previously been
developed according to the above mentioned con-
cepts and because it was calibrated for the high-
elevation snowpack subalpine zones. This dynamic
 hydrologic model was developed by the U.S. Forest
 Service, and was specifically designed to simulate
 the hydrologic impacts of watershed management
 on snow pack (Leaf and Brink 1973b and 1975).
 Figure III.B.l  is a flow chart of the basic model.
 Documentation for application of this model can be
 found in appendix ni.C.
SET PHASE
INDICATOR TO
ACCUMULATION
PHASE



HO S
* <.

Figure III.B.1.—General  flow chart  of Subalpine Water
Balance Model (from Leaf and Brink 1973b). WATBAL model.
   WATBAL models: (1)  winter snow accumula-
 tion, (2) the energy balance, (3) snowpack condi-
 tion, and (4) resultant melt in time and space un-
 der a variety of conditions. Combinations of aspect,
 slope, elevation, and forest cover composition and
 density are included. Much of the  snowmelt por-
 tion of the computer program was initially written
 by the Watershed Systems Development Unit  at
 the  Pacific Southwest Forest  and Range Experi-
 ment Station (Willen and others 1971). With this
 snowmelt  model,  the probable effects  of forest
 cover manipulation have been simulated.
   The model consists of three parts: (1) the deter-
 mination of the form of precipitation (rain  or
 snow), (2) snowpack condition in terms of energy
 level and  free water  requirements, and (3) the
 melting  process.  Shortwave and longwave radia-
 tion reaching the pack is estimated by means of a
 transmissivity coefficient function, which depends
 on the density and composition of the forest cover.
                                             III. 154

-------
Radiation inputs are adjusted for slope and aspect.
Reflectivity of the snowpack is varied according to
precipitation, the energy balance,  and time.

  The snowpack  is  assumed  to behave as  a
dynamic heat reservoir; thus all elements in the
snowmelt portion of the model are expressed in
units  of heat. The net external  energy balance is
computed at the snow surface. Rain and snow are
converted  from  inches at the  prevailing  air
temperature  to  equivalent  gram-calories.  Each
precipitation  event is added algebraically as  a
caloric-heat event to develop the heat reservoir or
snowpack. Temperatures within the snowpack are
computed using unsteady heat  flow  theory. The
snowpack will yield melt water only when it  has
reached a  zero  energy deficit  (snowpack
temperature  =  0°C)  and its free water holding
capacity is satisfied. Snowmelt rates after the pack
is primed are governed primarily by the longwave
and shortwave energy balances at the snow surface.
Input Requirements For WATBAL

  Data  requirements  for  the Subalpine  Water
Balance Model (WATBAL) are conventional. In-
formation, routinely available from such agencies
as the Soil Conservation Service, NASA,  Forest
Service, Geological Survey, and National Weather
Service, is adequate for  most applications.  The
data  requirements can  be  ranked  in  three
categories as follow:
  1. Watershed characteristics
        a. USGS topographic maps
        b. USFS vegetation type maps
        c. SCS soil survey data
  2. Snowpack and snow cover extent
        a. Conventional SCS snowcourse network
        b. SCS SNOTEL network
        c. NASA LANDSAT, etc.
  3. Climatological data
        a. Daily  maximum  and  minimum
          temperatures
        b. Daily precipitation
  The  density  of the  available  observation
networks will vary; however, as a rule of thumb, it
can be assumed that the snowcourse systems such
as SNOTEL will be adequate. Moreover, the den-
sity  of the   National  Weather  Service
Climatological  Data network in the subalpine zone
also appears adequate for most purposes.
              PROSPER Model


  PROSPER is  an atmosphere-soil-plant water
flow model that has been well documented (Golds-
tein and Manken 1972, Goldstein and others 1974)
and recently  evaluated  in  the southern  Ap-
palachians (Swift and others 1975). A schematic of
PROSPER is shown in figure m.B.2. The version
used has been operational on a daily basis, and a
description of the  computational procedures for
each day follows (from Goldstein and others 1974):
  (1)  Precipitation for the day enters the system.
      If there is no precipitation, the  simulation
      proceeds to  step 2. Precipitation initially
      enters the interception storage compartment
      which has a maximum storage  capacity as a
      function of leaf area index. When  the in-
      terception  compartment  is full, any  ad-
      ditional precipitation becomes  throughfall.
  (2)  If the  intercept storage compartment does
      not contain any water, i.e., if 60  = 0, then the
      simulation proceeds to step 3.

      If Bo >  0, then Fv(rx= 0) is calculated. Since
      ra is the only resistance to evaporation of in-
      tercepted water, rxis set to zero. If 9o>Fv(rx
      = 0), then an amount of water equal to Fv(rx
      = 0) is  evaporated  from  the  interception
      storage compartment, Fw is set to zero, and
      the simulation proceeds to step 3. If Fv(rx =
      0) >9o then all of 9o is evaporated and an
      amount of energy equal toLv9o (where Ly is
      the latent heat of vaporization  for water) is
      subtracted from the total  net radiation for
      the day, RN.  The adjusted value of RN will
      be used instead of the total net radiation in
      step 3.

  (3) At this point,  the simulation enters a loop to
     calculate soil water  transferred  to the at-
     mosphere  by  evapotranspiration and  soil
     water redistribution  and  drainage.  In  the
     original  implementation  of  PROSPER
     (Goldstein and Mankin 1972a), the looping
     structure was  not incorporated into the com-
     puter program. The saturated soil water con-
     ductivities used in the original  implementa-
     tion were based on data for agricultural soils
     (Miller and Klute 1967). For these values (on
     the order of 1  cm/day) a single calculation of
     soil water movement in a day using total
     daily throughfall  and solar radiation  was
                                             ni.155

-------
     EVAPORATION
       PRECIPITATION
EVAPOTRANSPIRATION
                                                          SURFACE 2
                       INTERCEPTION
                          STORAGE
EVAPOTRANSPIRATION SURFACE
                                                ra+rx
                              THROUGHFALL
                                 SURFACE 1
  LATERAL FLOW
                                     rs1
                        SOIL LAYER 1
                                           -Wr
                                            rrs1
                                rs12
SOIL LAYER 2
                                            rrs2
                               rs23
                                rs,n-1,n
                        SOIL LAYER n
                                                       rp+rr1
                              VEGETATION
                             ^  rr1+rr2
                                DRAINAGE
             Figure III.B.2.—Schematic ol PROSPER (from Goldstein and others 1974).
                                m.i56

-------
      adequate. However, saturated soil water con-
      ductivities have been found to be two to
      three orders  of magnitude greater for forest
      soils  than for agricultural soils  (Freeland
      1956, Longwell and others 1963, Peters and
      bthers 1969). For these  high values of soil
      water conductivity, single daily calculations
      produce  numerical instabilities.  This neces-
      sitates the inclusion of  the loop structure
      which makes N iterations in calculating the
      daily  water   movement.  The  number of
      passes through the  loop,  N, is  dependent
      upon throughfall, layer thickness, maximum
      saturated soil water conductivity,  and N for
      the previous  day.
  (4)  Upon entering the loop, soil water potentials,
      conductivities and resistances are calculated
      for the  soil  layers.  One Nth of  the  daily
      throughfall  and net  radiation are used to
      calculate Fv  [fx = gi(9x)] by the procedure
      outlined in the previous section, unless Fx =
      Fv [rx = gi(6 x )] has been set to zero in step
      2, in which case the depletion of soil water by
      evapotranspiration is zero. Also calculated
      are 9X and Gj for all i.  The volumetric soil
      moisture content of each level, 9X , is read-
      justed by 01  . If the moisture in any level ex-
      ceeds saturation, the excess is removed by
      lateral flow. The amount of water in the bot-
      tom layer exceeding field  capacity drains at a
      rate equal to the hydraulic conductivity.
  (5)  If the program has not passed through the
      loop  N times at this point, the simulation
      returns to step 3 and goes through the loop
      again. If the simulation has gone through the
      loop  N  times,  then the daily  total of
      evapotranspiration, lateral flow  from  each
      soil layer,  and drainage are calculated by
      summing the amounts calculated in each of
      the N passes through the loop.
  (6)  The simulation proceeds  to the next day and
      returns to step 1.
Input Requirements For PROSPER

  In general, daily precipitation,  solar radiation,
temperature, vapor pressure,  and average wind
speed are the climatic inputs. Vegetative inputs in-
clude the number of days from January 1 until the
vegetation is 50 percent leafed out and the number
of days from January  1 until 50 percent of the
leaves are off. An estimated, maximum (summer)
and minimum (winter), interception storage is also
needed, as are estimates of the leaf area index in
 both summer and  winter. Input requirements for
 soil properties consist of moisture  release curve
 data for the upper two soil horizons (i.e.,  rooting
 zone)  and field capacity estimates  for the other
 three lower horizons. Also needed for input are the
 saturated conductivity of the upper two horizons
 and the moisture release-conductivity curves which
 are  generated internally  using the  techniques of
 Millington  and  Quirk  (1959) via the  Green and
 Corey (1971)  program. Initial  soil moisture con-
 tents as well as field capacities for each of the five
 layers are also needed.
   Other parameters and coefficients  are needed to
 describe energy transfer rates and these were taken
 from the  PROSPER  sensitivity analysis by Lux-
 moore and others (1976) as there was little basis or
 expertise for modifying them.
   One constraint exists in the use of the PROSPER
 model: The leaf area index-ET relationships  were
 developed  for conditions that existed at Coweeta
 Hydrologic Laboratory  in  North  Carolina.
 Although the universality of this function has not
 been previously established, the model did perform
 well when  used elsewhere.
                Model Output


  By definition, neither PROSPER or WATBAL
are streamflow simulation models. PROSPER is
basically an evapotranspiration model with no sub-
surface  routing  components.  WATBAL  is  a
snowmelt model and, like  PROSPER,  has no sub-
surface routing.  Neither  model  is  capable  of
delivering water to  a stream channel.  The lateral
outflow and drainage simulated by these models
represents water which is on site and potentially
available for streamflow and may or may not repre-
sent routed streamflow.
  The two  models  were  each used for  different
climatic  regimes and there  were differences  in
modeling  objectives and  interpretation  of  each.
PROSPER was used  primarily in humid, non-
snowpack areas; the rationale was to first  simulate
evapotranspirational  loss  and  then  compare
seasonal  and annual outflow with observed out-
flow.  This comparison was  usually  acceptable.
Again the outflow simulated represented unrouted
water excess. However, the agreement between this
excess and  observed streamflow improved as a
function  of  basin  storage. Those shallow-soiled
basins with short resonance times or short "times
of concentration"  had a  fairly  good correlation
between simulated excess water and observed flow.
                                              III. 157

-------
Deep-soiled, slow  responding watersheds like
Coweeta had poor correlations.
  WATBAL was  used primarily in regions where
significant snow packs develop, and where there
was  need for  a snowmelt routine.  The same
problem of routing exists in WATBAL that exists
in PROSPER.  However, the actual hydrograph
from  the  basins where  WATBAL was  used is
dominated  by  a seasonal snowpack  and  melt
runoff. This flow is more predictable,  more con-
centrated,  and  the  translation of  melt  to
streamflow is more direct.  As a result, in those
hydrographs which are snowmelt-derived, there is
more  direct  correlation between simulated excess
water and actual streamflow. It was possible to pre-
sent  this  simulated  flow  as  a  time-serial
hydrograph.  For those simulations that were rain-
fall driven, the timing of "simulated  flows" was
distorted and delayed. It was unacceptable to pre-
sent these  values  as streamflow in  any serial
presentation.
  Since the magnitudes  of  simulated flow  and
observed flow using PROSPER had  similar fre-
quency distributions,  the simulated outflow could
be presented in a frequency distribution (not time
dependent)  as a representation of actual flow.
  Again, both  models  adequately simulate the
evapotranspiration losses,  and the  simulated  out-
flow is presented as water potentially available for
streamflow.  No existing model actually simulates
an  unbiased acceptable estimate  of  streamflow.
Existing models must be  acceptable until better
models are developed.
  In order to simulate treatment effect, after the
models were calibrated  cover density parameters
affecting the intercepting and transpiring surfaces
were modified  to  estimate the response due to
treatment.
                                             HI. 158

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                APPENDIX III. C: CALIBRATION OF SUBALPINE
                                WATER BALANCE MODEL
  The Subalpine Water Balance Model (Leaf and
Brink 1973b) was developed for, and has been suc-
cessfully applied  to a number  of representative
watersheds  throughout  the Rocky  Mountain
region. For lack of a better tool, this model was also
used  to simulate  the  snow pack hydrology  of
representative watersheds  in  each hydrologic
region. This section illustrates application of the
model to a number of index watersheds.
           INDEX WATERSHEDS


  Each index watershed was divided into several
hydrologic subunits that vary according to slope,
elevation, aspect, and forest  cover. The water
balance  was simulated  on each  subunit;  area-
weighted responses were computed and summed to
obtain the overall response for the  entire basin.
Both time and spatial variations were thus taken
into account.
  Daily temperature extremes in each of the sub-
units were estimated by extrapolating  published
            temperatures  at  nearby base stations, generally
            cooperative  stations  operated by  the National
            Weather Service. Because reliable long-term radia-
            tion data  were  not available  for most areas,
            shortwave  radiation  input  to  the  model  was
            generated from potential solar beam radiation in-
            put at the appropriate latitude, and then it was ad-
            justed  for the slope/aspect characteristics of each
            subunit. These values were further adjusted by em-
            pirically derived thermal factors to obtain an index
            of incident  shortwave radiation  each day.  Peak
            seasonal snow accumulation was  generally  es-
            timated from snow courses observed by the USDA
            Soil Conservation Service.
            Rocky  Mountain/Intermountain Hydrologic
                              Region (4)
              Mean annual water balances for representative
            watersheds  in  the Rocky  Mountain/Inland
            hydrologic region (4) are summarized  in  table
            IE.C.I. The Subalpine Water Balance Model was
            calibrated and validated on each. The simulation
                    Table III.C.1.—Mean annual water balances (in Inches) for typical subalpine
                        watersheds in the Rocky Mountain/Inland Intermountain Region
            Watershed
 Seasonal
snowpack,
  water
equivalent
 Pre-
 cipi-
tation
Evapo-
 tran-
 spira-
 tion
                                                                            Runoff
            Colorado:
              Soda Creek,
                Routt NF
              Fraser River,
                Arapaho NF
            Wolf Creek,
                San Juan NF
              Trinchera Creek,
                SangredeCristo
                Mountains

            Wyoming:
              South Tongue River
                Bighorn NF

            Montana:
              W. Ford Stillwater
                River, Custer NF

            Idaho:
              Diamond Creek,
                Caribou NF
  42.6

  15.0

  26.2

   9.5




  15.5



  30.1



  15.2
 55.2

 30.3

 48.0

 19.6




 29.6



 49.1



 23.6
 16.7

 16.9

 21.0

 14.5




 15.8



 17.0



 14.7
38.5

13.4

27.0

 5.1




13.8



32.1



 8.9
                                              m.i59

-------
analysis for Wolf Creek, located in the San Juan
National Forest, Colorado is summarized below.
  Leaf (1975)  has  previously summarized
hydrologic simulation analyses on Wolf Creek. The
watershed  (fig.  III.C.I)  was  divided  into 11
hydrologic  subunits that vary according to slope,
elevation, aspect, and forest cover (table III.C.2).
The water balance was simulated on each subunit;
area-weighted  responses were  computed  and
summed to obtain the overall response for the en-
tire basin.  Both time and spatial variations were
thus taken  into account. Further division of forest
and open areas resulted in a total of 20 subunits
used for the simulation analysis (fig. III.C.2).
  Daily temperature extremes in each of the sub-
units were  estimated by extrapolating published
temperatures at Wolf Creek Pass IE, a cooperative
station operated by the National Weather Service.
Because reliable long-term radiation data were not
available in the Wolf Creek area, shortwave radia-
tion input to the model was generated from poten-
tial solar beam radiation at 38° N latitude and ad-
justed for the slope/aspect characteristics  of each
subunit. These values were further adjusted by em-
pirically derived thermal factors to obtain an index
of incident shortwave radiation each day. Peak
snowpack  accumulation on  Wolf Creek  was es-
timated  from snowcourse transect data  collected
by the USDA Soil Conservation  Service and by
private contractors in the pilot project area. To in-
sure proper snowpack accumulation, the base sta-
tion  daily precipitation was adjusted until the
specified  water equivalent on each subunit was
reached  to correct for errors in the spacially ex-
trapolated precipitation data.


Model Calibration

  Eleven water years (1958-1968)  were simulated
during  calibration  studies  on  Wolf  Creek.
Published streamflow data during five subsequent
years (1969-1973)  were then  used  to validate the
simulated output for  the  same period.  This
analysis  is shown in  table III.C.3 on  a  monthly
residual volume basis to obtain a direct comparison
between  potential excess water and the observed
snowmelt hydrograph. Streamflow  data were ad-
justed  to account for diversions from Wolf Creek
via the Treasure  Pass  Ditch (U.S. Dep.  Inter.,
Geol. Surv. 1969-1973).
                                                  WOLF  CREEK
     12,000
     11,000
          9,000
                                                                        SCALE - Mi.
          Figure III.C.1.—Base map for Wolf Creek Watershed, San Juan National Forest, hydrologic subunits.
                                              in. 160

-------
Table III.C.2.—Geographic description of the drainage basin, Wolf Creek watershed, Colorado (see figure III.C.1.).
Hydrologic    Area
  subunit
            (sq. mi.)
Percent     Sub-
of total     unit
  area       code
Percent    Percent   Average   Average   Average   Remarks
   of         of      elevation    aspect     slope
division     basin       (ft)                   (%)
1 1.4
2 1.8
3 1.5
4 1.4
5 2.1
6 0.4
7 0.4
8 1.6
9 1.5
10 1.3
11 0.6
Total 14.0
10.3
12.6
11.0
9.8
14.8
2.6
3.1
11.2
10.8
9.5
4.3
100.0
1FW-0
10W-0
2FW-0
20W-0
3FW-121
30W-121
4FW-160
40 W- 160
5FW-192
50W-192
6FW-196
60W-196
7FW-9
70W-9
8FW-9
80W-9
9FW-45
10FW-45
11FW-76
110W-76

64.5
35.5
35.4
64.6
51.3
48.7
54.6
45.5
56.2
43.8
50.0
50.0
73.4
26.6
86.0
14.0
100.0
100.0
68.6
31.4

6.6
3.7
4.5
8.1
5.6
5.4
5.4
4.4
8.3
6.5
1.3
1.3
2.3
0.8
9.7
1.5
10.8
9.5
2.9
1.4
100.0
10,000
10,500
10,000
11,500
10,750
11,500
10,750
11,000
10,750
11,250
11,100
11,100
10,900
11,000
10,750
11,000
10,500
10,000
9,250
9,000

SE
SE
SE
SE
E
SE
S
SW
S
S
SW
SW
N
N
N
N
NW
NW
NW
W

40
40
30
40
20
40
20
45
35
40
30
20
15
15
10
10
20
15
45
50

Forest
Open
F
0
F
0
F
0
F
0
F
0
F
0
F
0
F
F
F
0


                                                                 I F | FORESTED

                                                                     ALPINE and OPEN

                                                                     CLEAR CUT
                                            SCALE - Mi.

                         Figure III.C.2.—Extent of forest cover on Wolf Creek Watershed.
                                                  m.161

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             Table III.C.3.—Streamflow data (1969-1973) on a monthly residual volume basis, (inches) adjusted
                                 to account for diversions from Wolf Creek.
Year
1969
1970
1971
1972
1973
May
0.08
0.05
0.04
0.19
0.02
June
0.25
0.32
0.33
0.17
0.56
July
0.07
0.07
0.03
0.00
0.36
Aug.
0
0
0
0
0.01
Total
0.40
0.44
0.40
0.36
0.95
Continental/Maritime Hydrologic Province (6)

  In order to  simulate  the  impacts of vegetative
manipulation  in  the Continental/Maritime
hydrologic  province (6),  an  8.1  square  mile
watershed  at  the  Corps  of  Engineers'  Upper
Columbia Snow Lab (UCSL) was used as a study
area (U.S.  Army 1956).  The watershed is Skyland
Creek, a headwaters stream  that  supplies  Bear
Creek, a  tributary  of  the Middle  fork  of the
Flathead River in  northwest Montana. Skyland
Creek is representative of most  of the mountain
                  watersheds in  Montana west  of  the  Continental
                  Divide, with the possible exception of the Kootenai
                  drainage.
                    Skyland Creek watershed  was  divided  for
                  analysis into seven subunits, with the objectives of
                  homogeneity with respect  to  slope, aspect, and
                  elevation, and proximity to a channel to reduce the
                  impact of routing (table ni.C.4). Several energy
                  slopes are represented. Skyland  Creek is in an
                  elevation zone  (5,000 to 7,500 ft.)  that can be con-
                  sidered "high"  in the northern Rockies. Low eleva-
                  tion zones (2,500 to 5,000 ft.) were also simulated.
                             Table III.C.4.—UCSL substation description
Sub
Unit

1
Area
(relative
to total)
percent
4
Slope Aspect
percent
40 W
Cover-
Type1 Density
percent
S-F 20
Eleva- General description
tion
x iooft
65-75 High steep breaklands;
               10        25        NE       S-F
               21         20        NE       LPP
               11         25
               15       45
               31        30
 Composite    100       30
           (8.1 sq. mi.)
SW       LPP
 N        LPP
          LPP
                        30        SW
          S-F
40


60



40


60



20




20
        23% S-F     39
          High energy

55-69  High moderate slope ridge;
          Low Energy

49-58  Middle-high gentle slope
           to stream;
          Low energy

52-64  High ridge;
          High energy

52-65  Middle-high steep ridge
           to stream;
          Very low energy

53-75  Middle to high moderate
           slope
           ridge to streamside;
          Very high energy

59-69  High ridge;
          Very high energy

49-75
   'Vegetation types: LPP = Lodgepole pine; S-F = Spruce-fir
                                                m.i62

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The technique will be outlined later in this report.
"Middle"  elevation zones  in  this region are
probably not significantly different with respect to
commercial timber harvests; therefore, only two
zones were simulated.
  Data for the calibration  and validation phases
were derived from  Snow Hydrology (U.S. Army
1956) and the associated logs. Water years (WY)
1947  through  1949 were  used  for  calibration.
Calibration consisted of manipulation of several
parameters to enable the model to reproduce the
observed water balance and distribution of runoff
in the three years. Validation consisted of running
the calibrated  model on three subsequent years
(WY 50-52) to  compare the resulting output with
the observed hydrograph (table in.C.5).
  Potential solar radiation was derived from Frank
and  Lee (1966).  Cover densities  and vegetation
types were estimated from aerial photos and the
text (U.S.  Army  1956). Potential evapotranspira-
tion by  month  was  derived by  Thornwaite's
method  and  modified  by observed  data.  Soil
moisture holding capacities were developed from
comments  in the text, and modified  by  energy-
elevation-vegetation  observations.   Transmis-
sivities (T) used are generally higher by .10 than
those suggested by the relationship T  = .19 Cd^6
developed by Leaf and Brink (1973 b) in the central
Rockies.  Transmissivity in  the model controls the
incoming direct solar  radiation  to the snowpack
surface only. The model is very sensitive to T with
respect to the ripening of the snowpack. The higher
T's were  necessary in the northern Rockies to make
the pack isothermal at an early date. Increases in
the corresponding cover  densities  (C d ) increases
                              the  sublimation/evaporation  losses  beyond
                              reasonable limits. Note that C d used in the model
                              is highly subjective.

                                Reflectivity  and melt thresholds  were initially
                              set at suggested values valid in the central Rockies
                              and then were adjusted to help calibrate the model
                              for Skyland  Creek.
                                Climatic  data consisting  of  maximum  and
                              minimum daily temperatures and daily precipita-
                              tion amounts for the base  station at UCSL were
                              derived from laboratory logs for WY 47-52 and from
                              Climatological Data for Montana (Natl. Weather
                              Serv. 1953-1963) for WY 53-63. Some of the data for
                              the last 10 years were taken from stations at Sum-
                              mit, Montana, in which case the temperatures were
                              modified by monthly regression equations to the
                              base UCSL station, and precipitation was modified
                              by  the   long-term  annual precipitation ratio
                              between the two stations.
                                Temperatures from the base station to the sub-
                              stations   were  modified by regression  equations
                              derived from several onsite meteorological stations.
                                Snowpack  data were  derived from  Snow
                              Hydrology for  WY 47-49 and from Water Supply
                              Outlook in Montana (USDA Soil Conserv. Serv.
                              1950-1963). Peak dates correspond to reported peak
                              dates. Peak amounts, however, were adjusted to fit
                              the water balance on that date. They do, in fact,
                              approach  the observed snow data in most cases.
                              The distribution of snow on each substation was by
                              regression of onsite and nearby snow  sites with
                              elevation.
                                For the years when no observed discharge infor-
                              mation was  available (WY  53-63), the peak water
                             Table III.C.5.—UCSL calibration and validation
    Water year
Annual precipitation—
 Ob*.         Pred.
  Annual runoff—
Obs.         Pred.
 Runoff efficiency—
Obs.         Pred.
inrhes
47
48
49
Calibration
47-49
50
51
52
Validation
50-52
All years
47-52
46
45
37

43
53
56
35

48

46
46
45
37

43
52
56
35

48

46
30
34
22

29
24
42
27

31

30
29
29
22

27
36
36
23

32

30
— percent —
65 63
76
59

67
45
76
78

66

67
64
60

62
69
63
65

66

64
                                               m.i63

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equivalent  was  adjusted  to  force  the  total
precipitation in the  model to  approximate the
observed precipitation.
  The  model simulated annual hydrographs with
accuracy  during the six calibration-validation
years of WY 47-52 (table IH.C.5).  Balances and
runoff efficiencies were excellent, while timing and
general distribution  tended to be slightly  higher
than observed. The  average  year  technique  for
analyzing response and changes due to treatments
tends to smooth annual deviations. However, the
deviations themselves will not affect the objectives
of this  handbook. The model underestimated early
and late season runoff, which is probably due to the
lack of subsurface routing. This runoff is not very
significant with respect to the snowmelt portion of
the hydrograph.
  The  analysis for high elevations  was  by direct
evaluation of the subunits. For low elevations the
Skyland Creek watershed was assumed to be 2,000
feet lower.
  All temperature intercepts  were increased  by
4°F. Although all vegetation might be assumed to
be ponderosa pine and lodgepole pine, forest cover
densities were not changed. The major adjustment
for elevation was the reduction of all peak water
equivalents to 1/3 the value used in the high eleva-
tion simulation. This adjustment is based on a
recommendation  by  Phil  Fames, Montana  State
Snow Survey Supervisor.1


UCSL Simulation Validity


  The annual simulated precipitation, runoff, and
resulting  runoff  efficiencies  are given in  table
m.C.5.  Water  balance predictions are  excellent
with the exception of WY  1948. Annual deviations
are  not evident when the six years are averaged.
  The  model  consistently underestimates  early
and  late season base  flow which is observed  in
several of the individual years and is evident still in
average year simulation. The volume of water  in
those periods  is very  small with respect to the
snowmelt portion of the  hydrograph.  Peaks are
simulated slightly higher than those observed and
delayed to 6 to 12 days in several years.  These
deviations are less but still evident in the average
year simulation.
  Overall confidence in the UCSL simulations is
good. Evapotranspiration and soil moisture closely
'SCS, personnal communication, 1977.
match those observed onsite. Extended data (WY
53-63) is primarily from Summit, Montana. The
UCSL station is very similar to Summit. Little er-
ror is expected from using Summit data.
  Less confidence can be placed on the low eleva-
tion modification. Although the changes are based
on process and observations, the elevation  change
is much more  complex than the modifications sug-
gest.


    Central Sierra Hydrologic Province (7)


  In order to  simulate the  impacts of vegetative
manipulation  in the Central Sierra region, a 3.96
square mile watershed at the Corps of Engineers'
Central Sierra Snow Lab (CSSL) was used as a
study area (U.S. Army 1956). The watersheds in
north central California.
  The Castle Creek watershed was divided for
analysis into seven hydrologic units, with the ob-
jectives of homogeneity  with  respect to slope,
aspect, elevation, and  proximity  to a channel to
reduce  the  impact of  routing  (table III.C.6).
Several energy slopes are represented. Castle Creek
is in an elevation zone (6,900-9,100 ft) that can be
considered "high" in the Sierras. Low elevation
zones (3,000-5,000 ft) and middle elevations (5,000-
7,000 ft) were  simulated with the same watershed.
The technique will be outlined later in this section.
  Data for the calibration and validation  phases
were  derived  from Snow Hydrology (U.S. Army
1956) and the associated logs. Data supplied by Dr.
Jim Smith, (USDA For. Serv., Berkeley, Calif.),
were  also used in the analyses. Water years 1947
through 1949, used for calibration,  are discussed
here. Calibration consisted of manipulation of
several parameters  to   enable  the model to
reproduce the observed water balance and distribu-
tion of runoff in the three years. Validation con-
sisted of running the calibrated  model on two sub-
sequent years  (WY 50-51) to compare the resulting
output with  the observed hydrograph  (table
in.C.7).
  Potential solar radiation was derived from Frank
and Lee (1966). Cover densities and vegetation
types were estimated from aerial  photos and text
(U.S. Army 1956). Potential evapotranspiration by
month was derived by Thornwaite's method and
modified by observed data.  Soil moisture holding
capacities were developed from comments in the
text, and modified by energy-elevation-vegetation
                                              m.164

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                                Table III.C.6.—CSSL substation description
   Sub
   Unit
  Area
(relative
to total)
Slope     Aspect
    Cover—          Eleva-
Type1     Density      tion
General description
              11
              15
              10
              26
             %                              %       X 100 ft

             45        SW       Bare        0       79-91   High steep barren tallus;
                                                               Very high energy

             15        SW       S-F         15       74-79   Middle elevation gentle valleys
                                                                 and hills;
                                                               High energy

             25          E       S-F         15       73-82   Middle elevation moderate slope;
                                                               Low Energy

             15        SE       S-F         25       72-82   Middle elevation gentle slope;
                                                               Moderate energy

             20          N       Bare        0       73-77   Middle elevation gentle slope
                                                                 tallus;
                                                               Low energy

             20        NE       S-F         25       69-72   Middle elevation moderate
                                                                 slope
                                                               Low energy
              0       horiz.      S-F         20      73 (river)  Moderate meadows;
                                                               Moderate energy

             30                25% bare      17       68-91
                               75% S-F
              13
              18
Composite    100
'Vegetation type: S-F = Spruce-fir
                               Table III.C.7.—CSSL calibration and validation
Water year
Annual precipitation—
Obs. Pred.
Annual runoff—
Obs. Pred.

47
48
49
Calibration
47-49
50
51
Validation
50-51
All years
47-51
48
63
52
54
69
81
75
62
48 30
64 44
51 33
54
69
81
75
62
36
54
70
62
46
33
44
35
37
49
62
56
45
Runoff efficiency—
Obs. Pred.
	 pert
63
70
63
65
79
85
82
72

69
70
68
69
71
77
74
71
                                                 m.165

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observations.  Some  transmissivities  used are
somewhat  higher  than those  suggested  by the
relationship T = 0.19 Cdmax "06 developed  by Leaf
and Brink  (1973b) in the  central Rockies. Trans-
missivity  in the  model  controls the  incoming
direct solar radiation to the snowpack surface only.
The model is very sensitive to T with respect to the
ripening of the  snowpack. The higher T's were
necessary in the  Sierras to make the pack  isother-
mal at an early date.
  Reflectivity  and melt thresholds were initially
set at suggested values valid in the central Rockies
and subsequently adjusted in calibrating the model
to Castle Creek.
  Climatic  data  consisting  of  maximum  and
minimum daily temperatures and daily precipita-
tion amounts for the base station at CSSL were
derived from laboratory logs  for WY 47-51, from
data  furnished  by  Dr.  Smith,  and from
Climatological Data for California (Natl. Weather
Serv. 1951-1962) for WY 51-62. Some of the data for
the last 9  years  were taken  at  Soda Springs,
California,  in  which case the temperatures were
modified by monthly regression equations to the
CSSL station, and precipitation was modified by
the long-term  annual precipitation ratio between
the two stations.
  Temperatures  from the base station to the sub-
stations were modified by regression equations on
onsite meteorological stations.
  Snowpack  data  were  derived  from  Snow
Hydrology for WY  47-51. Peak dates correspond to
reported peak dates. Peak  amounts, however, were
adjusted to fit the water balance on that date. They
approached the observed snow data observations in
most cases. The  distribution of snow on each sub-
station was by regression of onsite and nearby snow
sites with elevation.
  For the years when no observed discharge infor-
mation  was available, (WY 51-56, WY 60-62) the
peak water equivalent was adjusted so that total
model  precipitation  approximated  the observed
precipitation.  Acceptable  annual  deviation  of
predicted to observed precipitation was considered
at less than one  inch.
  The model simulated annual hydrographs during
the five calibration-validation years of WY 47-51
(table  III.C.7). Balances  and runoff efficiencies
were good, while timing and  general distribution
tended  to be slightly delayed.  The average year
technique for analyzing response to changes due to
treatments tends  to smooth  annual deviations.
 However, the deviations themselves did not affect
 the objectives of this handbook.
   The analysis  for high elevations was by  direct
 evaluation of the subunits.  For  low and middle
 elevations a similar watershed was assumed 4,000
 and 2,000 feet  lower,  respectively, than  Castle
 Creek. The calibrated model was modified to ac-
 comodate the lower  elevations by changing two
 basic parameters. Temperature intercepts were in-
 creased by 8° F. and 4° F., respectively. The major
 adjustment for elevation is the reduction of all peak
 water equivalents to 0.67 and 0.20 of the value used
 in the  high  elevation simulation. These adjust-
 ments are based on snow wedge curves (U.S. Army
 1956, plate 3-3).


 CSSL Simulation Validity.


  The validation and calibration  years WY 1947
 through 1951 water balances are  in table III.C.7.
 The hydrographs of the simulations for these five
 years are compared with the observed hydrographs
 on both annual and average bases to offer a level of
 confidence.
  On a  year-by-year basis  the  model had a
 tendency to underestimate early season runoff dur-
 ing years when  these events occur.  The model
 simulated these  events with accuracy with respect
 to timing, but underestimated the magnitudes. An-
 nual  peak  flows  were  closely simulated in
 magnitude; however, there was a  consistent delay
 in the model of perhaps one to six  days. This delay
was considered to be insignificant since handbook
 procedures were developed on a seasonal basis. The
model  tended to be more  responsive to inputs
yielding more abrupt changes  in discharge  than
those observed. This can be attributed to the lack
of subsurface routing of the model.
  When all five  years were averaged, most of the
annual  deviations  were not  evident.  Water
balances and efficiencies were within one inch (2
percent)  of the  average  observed annual runoff.
 Simulations  of  the  snowmelt  portion  of the
hydrograph including the spring recession were ex-
 cellent.  Early season (October-November) yields
still were underestimated. The 19-inch average an-
nual  evapotranspiration  and the soil moisture
predicted  were  consistent with those reported in
the literature (U.S. Army 1956).
  Based on these observations, the simulations of
response on Castle Creek are good, especially  when
                                              ni.166

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considered  on  an  average  basis.  The  annual
variability probably closely simulated the actual
system. Less confidence, however, can be placed on
a single year prediction. (Individual year  predic-
tions are not the objectives of the model or its in-
tended  use).  When forest  cover  densities  are
changed in  the calibrated  model to  simulate
silvicultural  activities,  the  resulting  response
should follow the real system. Less confidence can
be placed on simulations where the elevations have
been assumed lower than  Castle  Creek. These
modifications  were based   on processes  and
observed   physical  phenomena and  were  ex-
trapolated to reflect watershed conditions at some
distance to the south, and at lower elevations.
Alternate Simulations (CSSL)


  The Castle Creek watershed as simulated had a
relatively low cover density (Camax = 17%) overall.
Two subunits were assumed to be void of signifi-
cant forest cover. The greatest cover on the remain-
ing five subunits  was  25  percent. Therefore, in
order to simulate the greater changes in cover den-
sity on various energy slopes, the  model calibrated
for the observed inventory was rerun with all sub-
units assumed to have  an old-growth forest cover
density of 0.40, and  again  at  Cdmax =  .55. This
value of Cdmax represents a stocking of perhaps 150
square feet per acre. The corresponding values for
                               T were adjusted  slightly  upward from Lear's
                               relationship  of T  =  f(Cd)  consistent  with the
                               adjustments made in calibration. The model with
                               this  modified  Cdmax  was run with all the other
                               parameters consistent with the original simulation
                               to simulate  old-growth commercial forest condi-
                               tions.
                                     Northwest Hydrologic Province (5)


                                 Vegetation  manipulation  impacts  were
                               simulated  for the  higher elevation zones of the
                               coastal  Pacific Northwest region using data from
                               the Willamette  Basin Snow Lab  (WBSL)  (table
                               m.C.8). The specific watershed is Wolf Creek, a
                               2.07 square mile mountain  headwaters stream in
                               the Willamette River system of west central Oregon
                               (U.S. Army 1956).
                                 Wolf  Creek is representative of the commercial
                               timberlands of the region at elevations that ac-
                               cumulate snow and produce a significant snowmelt
                               hydrograph. Simulations of the rain forests at lower
                               elevations in this province are discussed later. The
                               region is under a strong maritime influence. Runoff
                               is in response to both rain and snow, with rain oc-
                               curring  throughout  most of the year, except in late
                               summer.
                                 The data base from the Corps of Engineers is in-
                               consistent (Table III.C.9). Reported runoff efficien-
                               cies ranged from 94 to 106 percent in the three years
                              Table III.C.8.—WBSL substation description
Sub
unit

Area Slope
(relative
to total)
Aspect Cover-
Type

Density

1 18
2 37
3 38
4 7
Composite 100
(2.07 sq. mi.)
20
20
35
0
24

NE
NE
SE
horiz.


S-F
S-F
S-F
S-F


60
60
55
10
55

                             Table III.C.9.—WBSL calibration and validation
Water year
Annual precipitation—
 Obs.         Pred.
  Annual runoff—
Obs.         Pred.
—Runoff efficiency—
Obs.         Pred.

49
50
51
47-51


831
1111
1061
100

106
130
116
117

88
108
100
99

88
109
98
98
	 percent 	
1061
971
94'
99
83
84
84
84
'Model calibrated on runoff only. Precipitation data appears to be in error during calibration years.
                                               m.i67

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of record. The precipitation amounts appear to be
in error—since they  are  20-30  inches below the
long-term average. Therefore, calibration consisted
of comparing the annual hydrographs with the
observed hydrographs for WY 49-51. Precipitation
was not a calibration parameter in this case, reduc-
ing confidence in the  water balance. However,
predicted evapotranspiration, soil  moisture, and
annual runoff were close to the  observed values.

  Temperature coefficients  were regressed when
possible against the few onsite stations. Due to the
nature of the  hydrologic  regimen, temperature
coefficients were  then raised 3°  to calibrate the
model.

  The extended  data base from WY 52-60 was
derived from Leaburg, Oregon — a nearby station
that receives considerably less precipitation and is
consistently 4-10° F.  warmer. The variability  at
WBSL was assumed to be represented by that at
Leaburg. Precipitation records were modified on an
annual  basis,  while  maximum and  minimum
temperatures  were regressed individually  on a
monthly basis.
   The Wolf Creek watershed was divided into four
subunits (table III.C.8). Simulations were run on
12 years of climatic record.
WBSL Simulation Validity


  Confidence in the WBSL simulation analysis is
less than at CSSL or UCSL for four reasons:
  (1)  The poor data base for precipitation during
      the  calibration years made  it difficult to
      completely verify the water balance.
  (2)  The maritime influence on snow accumula-
      tion causes several different  accumulation-
      depletion events each year with almost con-
      stant melt. This is difficult to simulate with
      the Subalpine Water Balance Model in its
      present configuration.
  (3)  Although the average year simulation during
      the calibration period closely approximates
      the observed hydrograph, the individual year
      simulations are more variable in timing and
      peaks than those observed. This response is
      masked in the average year output.
  (4)  The lack of data for validation prohibited as-
      sessment of the level of confidence on in-
      dependent data not used in calibration.
  In conclusion,  the WBSL  simulations reflect
regional  water  balances  as  reported  in the
literature, but confidence is difficult to establish to
a degree due to lack of long-term small watershed
data at high elevations.
                                               ni.168

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       APPENDIX III.D: CALIBRATION AND VALIDATION SUMMARY
                       FOR SITES MODELED WITH PROSPER
  Since PROSPER is primarily an evapotranspira-
tion  model  without  a routing component,  and
because the results were being reported in terms of
flow duration curves, not hydrographs, calibration
efforts were concentrated on simulating annual and
seasonal evapotranspiration and in reproducing the
observed  distribution  of flows. Therefore, timing
was not a critical design criteria in the calibration
scheme. The  needs of this handbook dictated ac-
curacy in terms of the distribution of weekly flows.
  There are calibration techniques the modeler can
employ to  improve  response, but  use  of  these
methods  depends on one's philosophy. In terms of
PROSPER there are  essentially no  calibration
variables, i.e., variables that do not have a physical
basis and/or that cannot be measured. If the user
wants the model to represent the physical system,
then the  variable should not vary from one's best
estimate  of them. This philosophy was followed in
the development of this chapter with two excep-
tions: Parameters were altered within the expected
range of their measured value, and in certain situa-
tions, the value of a parameter was altered from its
true value if such alteration could compensate for a
weakness in the model. In this respect, if storm
response  was  dampened  excessively  because  of
routing deficiencies in the model, increases in con-
ductivity of the soil or decreases in its depth might
be made  to compensate. These adjustments were
primarily made to the lower three soil  horizons
since they did  not directly affect the evapotran-
spiration  draft and were, in a sense,  dead storage.
  A rigorous sensitivity analysis has been done by
Luxmoore and others (1976)  on PROSPER.  In
calibration, the water balance is adjusted primarily
by changing leaf on/leaf off dates, rooting depth,
interception   storage,  and leaf  area  index.  No
changes were made in initial estimates of leaf area
index.  Interception storage was adjusted to corres-
pond with estimates of interception loss using local
equations, and leaf on/leaf off dates were varied
over  a two-week span. Very little  was  done  to
calibrate  PROSPER.  Initial  estimates  of the
parameters were made.
  The following is a description of the application
of PROSPER to various  representatives and ex-
perimental watersheds by region.
  THE APPALACHIAN HIGHLANDS AND
          MOUNTAIN REGION (2)


  Watersheds from four areas were used to repre-
sent the  region. The Leading Ridge  Watershed
Number  2  in central Pennsylvania, The Fernow
Forest Watershed Number 4 in northcentral West
Virginia,  the Walker Branch Watershed near Oak
Ridge, Tennessee,  and  Coweeta  Watershed
Number  18 near Franklin, North  Carolina were
used.

         Leading  Ridge,  Pennsylvania


   Leading Ridge Watershed Number 2, operated
 by Pennsylvania State University, is located in the
 ridge and valley province in central Pennsylvania.
 The vegetation  on the 106-acre (43ha) watershed
 consists of mixed  hardwoods,  primarily  oak-
 hickory,  with little understory.
   Initial parameter  estimates and the  necessary
 data base were provided by James Lynch from the
 watershed  files at  Pennsylvania State University.
 The  hydrologic characteristics of the  dominant
 soils were not available, and since the soil series at
 Leading  Ridge was the same as data available at
 the Fernow Experimental Forest for their soils, the
 model was run  using  Fernow  soil  hydrologic
 parameters. Because evapotranspiration from the
 initial calibration  run was considered  high, the
 summer  interception capacity was lowered from 0.3
 cm to 0.25 cm to reduce the simulated evapotran-
 spiration and match the interception loss with that
 estimated  using a  local equation.
   Four years of climatic data were provided, and
 the first two  years were  used  for  calibration.
 Calibration results  were  confounded because of
 significant rain on snow events, i.e., runoff efficien-
 cies greater than one. The remaining two years of
 data used to test the calibration also had snowmelt
 events. Since a significant snowpack generally does
 not accumulate, and since available snowpack in-
 formation was deemed unreliable, it was concluded
 that  using the snowpack  model,  rather  than
 PROSPER, would be unsuccessful. Further at-
 tempts at  calibration were deemed unnecessary.
                                             m.169

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  An October to September water year was chosen
and, with close examination of actual precipitation
versus observed  streamflow, it can be noted that
there is a lag in annual response. Years of high
precipitation do  not correspond with high levels of
flow and vice versa. For the data set as a whole, the
simulated streamflow comes within 0.8 percent of
the  total  observed  flow.  Average  predicted
evapotranspiration during the 4-year period is 22.3
inches — this compares favorably with the poten-
tial evapotranspiration estimated at 22 to 24  in-
ches.  Because of  snowmelt  runoff events,  in-
dividual observed versus predicted hydrographs
ranged from good to poor. Since Hydrologic Region
2 has been characterized as an area where response
is not dominated by snowpack accumulation and
ablation, and  given Leading Ridge's proximity to
the border between Hydrologic Regions 2 and 3, it
was felt that the simulation would more than ade-
quately represent the hydrologic response with
respect to the  distribution of flows. A summary of
the simulation is represented in table III.D.l.
             Table III.D.1—Calibration and validation summary for sites modeled by PROSPER
Water
Year

1961
1962
1963
1964

1964
1965
1968
1969

1966
1967
1968
1969
1970
1971

1966
1967
1968

1973
1974
1975

1971
1972

1972
1973
1974
#1
Actual
precip.

101.3
93.7
81.0
91.5

141.2
109.7
129.8
138.3

109.0
133.0
129.0
107.0
121.0
132.0

121.0
132.0
159.0

167.6
303.0
232.8

125.1
139.2

236.3
229.4
221.4
#2
Trans-
piration

39.2
30.1
33.1
29.3

34.2
33.3
33.4
40.4

61.1
68.9
65.9
63.2
60.0
73.1

57.6
57.5
56.4

52.1
45.1
47.9

30.4
25.2

53.1
50.2
50.3
#3
Inter-
ception

16.8
14.4
14.8
13.3

22.7
26.1
27.0
31.0

12.1
13.9
13.8
12.4
12.3
15.5

21.0
24.8
24.9

38.2
28.0
41.4

13.1
13.1

26.5
23.4
24.0
#4
Total
ET

65.2
53.5
57.1
51.0

64.4
67.1
67.2
78.9

78.9
88.6
85.3
81.0
78.0
94.7

83.2
86.9
85.8

94.0
80.0
92.8

53.2
46.7

87.3
81.7
82.3
Observed versus predicted response
#5 #6 #7 18 #9
Flow Changes in (Q + ASM) Actual Percent
Q soil moisture measured deviation
ASM OBSQ
Leading Ridge
41.6
41.8
29.0
43.5
Fernow
76.2
35.3
62.9
58.8
White Hall
25.1
37.5
40.6
25.5
37.2
37.1
Oxford
38.6
43.9
72.3
H.J. Andrews
82.8
251.0
162.1
Hubbard Brook
70.3
89.4
Coweeta
134.9
144.5
141.2

-5.4
-1.6
-5.1
-3.1

0.5
7.2
-0.3
0.7

5.5
6.5
2.7
0.6
6.0
0.5

-0.4
0.7
0.9

- 9.2
-24.0
-22.1

1.4
2.5

14.1
3.1
-2.3

36.2
40.2
24.9
40.4

76.7
42.5
62.6
59.5

30.6
44.0
43.3
26.1
43.2
37.6

38.2
44.6
73.2

73.6
227.0
140.0

71.7
91.9

149.0
147.6
138.9

44.0
41.4
22.1
33.0

56.4
35.3
51.6
60.8

26.8
36.0
37.7
31.9
33.1
41.1

13.4
15.2
46.8

72.9
213.0
151.2

66.7
104.5

135.8
150.3
135.9

-12.0
- 2.8
-12.7
+22.0

+26.0
+ 17.0
+ 17.6
+ 2.1

14.0
22.0
15.0
18.0
14.0
8.0

185.0
193.0
156.0

+ 1.0
+ 6.6
- 7.4

+ 7.5
-12.1

- 9.7
- 1.8
+ 2.2
                                              ffl.170

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            Fernow, West Virginia


  The  Fernow  Experimental Watersheds  are
operated by the U.S. Forest Service, Northeastern
Forest  Experiment Station.  Fernow  Watershed
Number 4 was used. This 95-acre (38  ha), mixed
hardwood forest was chosen to represent the central
Appalachians, particularly  the Allegheny Moun-
tains, and is located near Parsons, West Virginia.
  The  data set  and initial  parameter estimates
were provided from the files at the Fernow Ex-
perimental Forest by Northeastern Forest Experi-
ment Station. Numerous changes were made in the
parameter  set before PROSPER  was  considered
calibrated  on  the  watershed.  However,  most of
these changes entailed  a sensitivity  analysis to
become familiar  with  PROSPER.  The final
parameter set differed from the initial  one only in
that the first two soil layers (of five) were decreased
slightly in depth to enable PROSPER to execute
more efficiently. A slight adjustment  was also
made in the distribution of roots between the  two
upper horizons. The dates at which the  canopy was
50 percent on and 50 percent off were increased and
decreased  slightly  to  decrease ET and  increase
early summer and  fall storm response.
  Four  years  of climatic  data were available.
Calibration was done on the first two years of data.
The water year  selected  started May 1, and in-
dividual  hydrograph simulation  was  considered
good, although, as was frequently the case, timing
was slightly offset  to the  right of the observed
hydrograph because of routing deficiencies. Annual
potential evapotranspiration, estimated  by clas-
sical methods, ranged from 23 to 25 inches. Average
annual simulated evapotranspiration was 27.3 in-
ches. Thus, PROSPER  slightly  overestimated
evapotranspiration. A direct comparison  between
observed and predicted flows  is shown on table
m.D.l. Watershed Number 4 has a poor precipita-
tion runoff relationship,  and we expected  to
simulate more  streamflow  than was observed.
Leakage in Fernow Watershed ranges from 1 to 10
or more inches.
          Walker Branch, Tennessee


  The normal calibration and validation procedure
was unnecessary in this case since PROSPER was
developed and  tested  on  Walker Branch.  A
calibrated parameter and data set was provided by
Dale Huff at the Oak Ridge National Laboratories.
Walker  Branch is located in eastern  Tennessee,
and  vegetation consists  of  mixed hardwoods,
primarily oak, hickory, and yellow poplar. A more
thorough description of the calibration and sen-
sitivity  analyses can be found in the  PROSPER
Documentation (Goldstein and others 1974).

           Coweeta, North Carolina
  The  Coweeta  Experimental  Watersheds  are
operated by the U.S.  Forest Service and Coweeta
Hydrologic Laboratory. Watershed Number 18 was
used  in  this  study.  This watershed  is
predominantly occupied by mixed hardwoods.
  An initial parameter set was provided by Lloyd
Swift  of  the  Coweeta  Hydrologic  Laboratory.
Calibration of PROSPER at this site proved to be
the most  difficult calibration effort encountered,
due  to some  unique hydrologic features of the
watershed. The hydrologically active soil-regolith
varies from 30 to 100 feet. This gives a strong
baseflow component with a long resonance time.
However,  the watershed also exhibits relatively
strong storm response during the dormant season.
Thus, the watershed is able to route water through
the system via several pathways. PROSPER is un-
able to simulate such a system, especially where it
is as strongly defined as at Coweeta. Numerous
changes were made in the initial parameter set in
order to achieve a parameter set which represented
an  acceptable  compromise between baseflow
simulation and storm response. Since the initial
parameter set  produced  outflow response which
was  considerably more "flashy" than  the actual,
soil depths were  increased and soil conductivity
values were decreased in an effort to dampen storm
response.
  Three years of climatic data were provided. One
year was used in model calibration. The water year
started May  1. Hydrograph simulation was con-
sidered fair; however, timing was offset to the right.
Simulated annual water balance was very good.
Mean total evapotranspiration was 33 inches. Con-
sidering this is a north-facing watershed, it com-
pared favorably with an average pan evaporation of
35 inches.
  The 1973 water year was used  as the base for the
simulation runs. This year had the most represen-
tative  lower  end of the resulting  flow duration
curve. Since the effects of timber harvesting in this
                                             HI.171

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area are most pronounced at low flow periods, the
1973 year was chosen as being the most represen-
tative.
  The comparison of simulated or observed flow is
shown in table HI.D.I.
   THE GULF AND ATLANTIC COASTAL
        PLAIN/PIEDMONT REGION


  This region was  characterized by  simulations
using data sets from two experimental watersheds:
The White Hall Watershed on the Georgia Pied-
mont near Athens, Georgia, and Oxford Watershed
Number 2 on the Gulf Coastal Plain  near Oxford,
Mississippi.


             White Hall,  Georgia


  White  Hall  is a  small  60-acre  experimental
watershed located on the Piedmont near Athens,
Georgia,  and  is  operated  by  the University  of
Georgia.  Vegetation  consists  of  mixed pine-
hardwoods typical of the revegetated cottonlands
common in the region. Initial parameter estimates
and the climatic data set were provided by Dr.
John D. Hewlett  of the University of Georgia.
  Only minor adjustments were made in the initial
parameter set. Initial estimates of soil depth were
cut in half to remove a considerable delay in storm
response. Saturated conductivity rates for the soil
profile were revised when more specific onsite infor-
mation became available to Dr. Hewlett.
  Six years of data were provided. Calibration was
carried out  on the first three years. Very  little
calibration on the data set was needed  once the
revised soils data were provided.
  For convenience, May 1 was used as the start of
the water year because the date generally occurred
just after the seasonal peak and antecedent condi-
tions were  similar from year to year. PROSPER
predicted 225 area inches of outflow for the 6-year
period; 207 area inches were observed, resulting in
an  average error  of 9 percent. Average estimated
evapotranspiration during the period was 33.2 in-
ches.1 Given this  average and the total  predicted
outflow  (assuming  some watershed  or  weir
leakage), the results can be considered very good.
The individual yearly values are  shown in table
m.D.i.
  The year starting May 1, 1971,  was selected as
the basis for the simulation runs.  This year most
closely resembled the average simulated flow dura-
tion curve. It was three inches above normal in
terms of total annual precipitation.


              Oxford, Mississippi


  The  Oxford  Experimental  Watersheds  are
located on the Coastal Plain in northern Missis-
sippi. They are operated by the U.S. Forest Ser-
vice, Forest  Hydrology Laboratory,  Southern
Forest Experiment Station. Watershed Number 2
was selected for use here. Watershed Number 2 is a
small, 4.6-acre pine-hardwood watershed. Initial
parameter estimates and data set were provided by
Mr.  Stan  Ursic at  the  Forest  Hydrology
Laboratory.
  The only deviation from the original parameter
given us was  a slight  adjustment in  interception
capacities of the vegetation.
  Three years of data were reduced to a form re-
quired by PROSPER. Normal evaluation of model
response cannot be  made because a substantial
portion of basin outflow  (approximately 10 inches
per year) is lost2 to deep seepage or does not appear
in  the  channel  at the  weir  site; therefore,  the
calibration goal was to simulate the estimated an-
nual evapotranspiration and to simulate the occur-
rence of the observed  storm response in terms of
timing, not  peaks.  Relative  to  these  goals  the
results of calibration were very good. The estimate
of  evapotranspiration losses had been  derived
earlier from soil moisture studies. As expected, the
simulations overpredicted the storm  response as
measured at the weir site. Calibration was carried
out on  the first two years of the  data set and  a
validation made on the third year.
  If the observed outflow is adjusted by the average
10 inches of seepage loss, then the predicted (shown
in table III.D.l) versus adjusted observed outflow
gives deviations of 1.4 percent, 9.8  percent, and 1.6
percent respectively for three years. Based on an
unpublished  study by Ursic, annual evapotran-
spiration averages between 33 and 36 inches per
  'Persona/ Communication, John D. Hewlett,  University of
(! corgi a
  2Personal  Communication, Stan Ursic, Forest Hydrology
Laboratory.
                                               III.172

-------
year.  Annual  evapotranspiration predicted  by
PROSPER averages 33.6 inches.
  The 1967 year was chosen as the base for the
simulation runs. It had the smallest deviations
from normal in total annual precipitation and total
annual runoff. It also had the most representative
simulated flow duration curve.
      PACIFIC COAST HYDROLOGIC
     PROVINCES — NORTHWEST (5),
      CONTINENTAL MARITIME (6),
        AND CENTRAL  SIERRA (7)
             LOW ELEVATION
  Data sets for this region were readily available.
The H. J. Andrews Experimental Watersheds were
the only ones that had data sets conducive to run-
ning  PROSPER. Watershed  Number 2  was
selected.
  Where available for the PROSPER simulations
on Hubbard  Brook,  the results of simulation,
although not  used directly,  are shown in table
ffl.D.l.

           H. J. Andrews,  Oregon


  The H. J. Andrews Experimental Watersheds are
operated by  the U.S.  Forest  Service, Pacific
Northwest Experiment Station. They are located
in the rain-predominant lower elevations  of  the
Willamette Basin in  the Oregon Cascades.  The
watershed used in this study was Number 2, a 149-
acre  (60  ha) watershed  supporting a  heavy
Douglas-fir forest.
  Information for initial parameter estimates and
climatic data was provided by Dr.  Dennis Harr,
Pacific Northwest Forest and Range Experiment
Station. There were no changes from the initial
parameter set with the exception of adjusting the
interception losses. Three years of climatic data
were available.
  Both hydrograph simulation and  annual water
balance were very good. Timing was  slightly offset
to the right. Average annual evapotranspiration as
computed by PROSPER was 47.3 inches,  mostly
interception.
  The 1975 water year was chosen as the basis for
the simulation runs. The 1973 water year was very
dry in comparison  to long-term climatic records.
The 1974 water year was unusually wet.
  In addition, PROSPER was calibrated  to two
watersheds in the Lake  States, New England
region. Marcell Watershed Number 2 near  Grand
Rapids,   Minnesota,  and  Hubbard   Brook
Watershed Number 3  were  used.  The  annual
balance for both was fairly good, but since a winter
snowpack  is  significant  throughout the  region,
PROSPER simulations  distorted  the dormant
season flows. A  decision was made to base the
methodology for this region on the Leaf and Brink
(1973b) snowmelt model simulations.  PROSPER
did well in estimating annual evapotranspiration
and streamflow, however. Only two years of records
were available for the PROSPER simulations on
Hubbard  Brook.  The results of simulation,
although  not used directly,  are shown in table
III.D.1.
                                            m.173

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              Chapter IV

     SURFACE EROSION
this chapter was prepared by the following individuals:
          Gordon E. Warrington
               Coordinator

        with major contributions from:
             Kerry L. Knapp
             Glen 0. Klock
            George R. Foster
            R. Scott Beasley

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                               CONTENTS
                                                                     Page

INTRODUCTION	  IV.l
DISCUSSION: SURFACE SOIL LOSS  	  IV.2
  GENERAL CONCEPTS OF SURFACE SOIL LOSS	  IV.2
      Detachment By Raindrop Impact	  IV.2
      Detachment By Surface Runoff	  IV.3
      Environmental Changes Created By Silvicultural Activities Which Affect
       Surface Soil Loss Potential	  IV.3
  PROCEDURAL CONCEPTS: ESTIMATING SURFACE SOIL LOSS	  IV.4
    The Rainfall Factor, R	  IV.5
      Energy-Intensity Values, El	  IV.5
      Determining The Rainfall Factor  	  IV.5
      R Values For  Thaw And Snowmelt	  IV.10
    The Soil Erodibility Factor, K 	  IV.10
      Determining The Soil Erodibility Factor 	  IV.11
    The Topographic Factor For Slope Length And Gradient, LS	  IV.14
      Slope Length  Factor, A 	  IV.14
      Slope Gradient Factor, S 	  IV.14
      Determining The Topographic Factor	  IV.15
      Irregular Slopes	  IV.15
    The Vegetation-Management Factor, VM 	  IV.21
      Effects Of Canopy Cover, Type I	  W.21
      Effects Of Mulch And Close Growing Vegetation, Type II 	  IV.22
      Residual Effects Of Land Use, Type in	  IV.23
      Sediment Filter Strips	  IV.23
      Determining The Vegetation-Management Factor	  IV.23
      Seasonal Adjustments for VM	  IV.24
    Estimated Soil Loss Per Unit Area  	  IV.24
      Converting MSLE To Metric	  IV.24
    Erosion Response Units	  IV.29
      Delineating Erosion Response Units	  TV.29
    Summary	  IV.47
CONSIDERATIONS FOR REDUCING EROSION	  IV.47
APPLICATIONS, LIMITATIONS AND PRECAUTIONS:  SURFACE SOIL
  LOSS 	  IV.49
DISCUSSION: SEDIMENT DELIVERY	  IV.52
  GENERAL CONCEPTS OF SEDIMENT DELIVERY 	  IV.52
    Factors Influencing Sediment Delivery	  IV.52
      Sediment Sources	  IV.52
      Amount Of Sediment	  IV.52
      Proximity Of  Sediment Source  	  IV.52
      Transport Agents	  IV.52
      Texture Of Eroded Material	  IV.52
                                   rv.ii

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     Deposition Areas	   IV.53
     Watershed Topography 	   IV.53
   Sediment Delivery Model	   IV.53
  PROCEDURAL CONCEPTS: ESTIMATING SEDIMENT DELIVERY ...   IV.54
   The Sediment Delivery Index	   IV.54
     Evaluation Factors	   TV.54
     Determining The Sediment Delivery Index 	   IV.55
   Estimating Sediment Delivery By Activity 	   IV.60
  CONSIDERATIONS FOR REDUCING SEDIMENT DELIVERY	   IV.60
APPLICATIONS,  LIMITATIONS  AND PRECAUTIONS: SEDIMENT
  DELIVERY	   IV.62
THE  PROCEDURE	:	   IV.63
  ESTIMATING SEDIMENT DELIVERY FROM SURFACE EROSION
   SOURCES	   IV.63
LITERATURE  CITED 	   IV.64
APPENDIX IV.A: GULLY EROSION 	   IV.67
APPENDIX IV.B: EROSION OVER TIME 	   IV.68
APPENDIX IV.C: CONTROLLING DITCH EROSION	   IV.69
                               IV.iii

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                            LIST OF EQUATIONS
Equation


I V.I


IV.2.
                                                                          Page
IV.3.
   5
IV.8.
        A = RKLSVM  	  IV.4


                    	  IV.5
R= EL  	
     100

E = 916 + 331 logioi   	  IV.10
IV.4.    K=  (2.1 X 10-6)  (12-Om) (M114)  + 0.0325(8-2) + 0.025(P-3)  ..  IV.ll
           _(KWMW  + KdMd)
                Mw + Md


IV.6.    L = (A/72.6)m   ..


IV.7.
                                                                  IV.12




                                                                  IV.14
        s =  (0.43 + 0.30s  + 0.043s2)                                        IV 14

                       6.613
                      0.43 +0.30s + 0.043s2
IV.9.    LS  = — •  S
                                         V  10,000  \

                                         Aio,000+s2/
                                                 10,000
                                               10,000 + s2
IV.9a.   .    -,„„„„,,  10!0(X)


IV. 10.   Cinn =  0.169V  - 0.356


IV.ll.
        VM =
                         M
IV. 12.   F = CRL
             ,1.49
IV.C.l.  V  = (— )  (R0.66)  (go.5)
                                                                   IV.15




                                                                   IV.15





                                                                   IV.17



                                                                   IV.22







                                                                   IV.55



                                                                   IV.69
                                      IV.iv

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                              LIST OF FIGURES
Number                                                                   Page
IV. 1.  —Flow chart of the procedural concepts involved in estimating sediment
          delivery from surface erosion sources  	  IV.6
IV.2.  —Iso-erodent  map illustrating average annual values of the rainfall
          factor, R	  IV .8
IV.3.  —Nomograph for determining the soil erodibility factor, K	  IV.13
FV.4.  —Nomograph  for  determining  the topographic factor, LS,  on simple
          slopes	  IV.16
IV.5.  —Values of n  for use  with irregular slopes with appropriate values
          of m	  IV.18
IV.6.  —Values of n for use with irregular slopes where m = 0.6	  IV.19
IV.7.  —Generalized cross-section of outsloped road	  IV.20
IV.8.  —Influence of vegetal canopy on effective El	  IV.22
IV.9.  —Effect of plant residues or close-growing stems at the soil surface on the
          VM factor	  IV.22
IV.10.—Effects of fine roots in topsoil on the VM factor	  IV.23
IV.ll.—Relationship between grass density and the VM factor	  IV.27
IV.12.—Relationship between forb density and the VM factor	  IV.28
IV.13.—The Horse Creek watershed boundary 	  IV.30
IV.14.—Drainage net of the Horse Creek watershed 	  IV.31
IV.15.—Individual hydrographic areas of the Horse Creek watershed	  IV.32
IV. 16.—Soil mapping unit boundaries for the Horse Creek watershed	  IV.33
IV.17.—Proposed transportation system (roads and log landings) for the Horse
          Creek watershed	  IV.34
IV.18.—Proposed cutting units for the Horse Creek watershed	  IV.35
IV.19.—Composite map of all topographic and management treatments for the
          Horse Creek watershed,  hydrographic area 3 	  IV.36
IV.20.—Effect of individual parameters on the K factor when other parameters
          are maintained at a low, moderate, or high influence on K	  IV.51
IV.21.—Potential sediment transport paths for different parts of a slope 	  IV.53
IV.22.—Stiff diagram for estimating sediment delivery 	  IV.56
IV.23.—Relationship  between polygon  area on stiff diagram  and  sediment
          delivery index  	  IV.57
IV.24.—Example of graphic sediment delivery model for road R3.1	  IV.58
IV.C.l—Nomograph  for Manning formula	  IV.70
                                      IV.v

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                               LIST OF TABLES
Number                                                                   Page
IV.1.   —Example of data tabulation when using graphs for obtaining LS values
          for irregular slopes	   IV.17
IV.2.   —Velocities of falling waterdrops of different sizes falling from various
          heights in  still  air	   IV.21
IV.3.   —"VM" factor values  for construction sites	   IV.24
IV.4.   —"C" factors for permanent pasture,  rangeland, idle land, and grazed
          woodland	   IV.25
IV.5.   —"C" factors for undisturbed woodland  	   IV.25
IV.6.   —"C" factors for mechanically prepared woodland sites	   IV.26
IV.7.   —Values  of organic matter,  fine sand   -f-  silt, clay,  structure, and
          permeability used  as constants when  calculating K factor	   IV.50
IV.8.   —Water availability values for given source area  	   IV.59
IV.C.I.—Values for Manning's n and maximum permissible velocity of flow in
          open channels	   IV.71
IV.C.2.—Hydraulic radius (R)  and  area   (A)  of  symmetrical  triangular
          channels	   IV.73
IV.C.3.—Hydraulic radius (R)  and  area (A)  of  nonsymmetrical  triangular
          channels 	   IV.74
IV.C.4.—Hydraulic radius (R)  and  area  (A)  of symmetrical trapezoidal
          channels 	   IV.75
IV.C.5.—Hydraulic radius (R)  and area (A) of nonsymmetrical trapezoidal
          channels	   IV.80
                                     IV.vi

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                          LIST OF WORKSHEETS
Number                                                                Page
IV.1.—Soil characteristics	IV. 37
IV.2.—Watershed erosion response unit management data	IV. 38
IV.3.—Estimates of soil loss and delivered sediment	IV. 41
IV.4.—Estimated VM factors	IV.42
IV.5.—Estimated monthly change in VM factors	IV. 43
IV.6.—Weighting of VM values for roads	IV.44
IV.7.—Factors for sediment delivery index	IV. 45
IV.8.—Estimated tons of sediment delivered to a channel	IV. 46
                                    IV.vii

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                                     INTRODUCTION
  Over the past 50 years, many attempts have been
made to identify soil and site characteristics that
can be used as parameters to quantify the amount
of accelerated soil erosion on agricultural and forest
lands. Most  of  the models  that  have  been
developed are unique to the areas where they were
tested and may not  be  applicable to other loca-
tions. Models  which estimate the movement of
eroded material through a forest environment to a
stream channel have not been extensively tested.
  The most  acceptable  model that is used  to es-
timate surface soil erosion on agricultural lands is
the  Universal  Soil Loss Equation  (USLE)
developed by Wischmeier and Smith (1965). Since
this equation is not universally applicable to forest
environmental conditions,  attempts have been
made to develop  a Modified Soil Loss Equation
(MSLE). To adapt the USLE to forest conditions,
the cropping management factor (C) and the ero-
sion control practice factor (P) have been replaced
by  a vegetation-management factor (VM)  in  the
MSLE.  Although  this approach  for quantifying
surface soil loss on forest lands  appears to  be  the
best method at this  time, it has not been  exten-
sively tested  or validated  on forest  lands
throughout the United States.
  The MSLE  does not quantify the amount of
material that may come from gully erosion or  soil
mass movement.   A  suggested  method  for
evaluating gully erosion is presented in appendix
IV.A.
  The MSLE model is one of several tools to be
used when attempting to understand the effects of
different management practices on a given piece of
land. This erosion model provides only a long term
estimate or an index of the amount of soil loss from
a given site (Wischmeier 1976).  It is only an es-
timate because: (1) A model, no matter how  com-
plex, is a representation of reality and should never
be  confused  with reality (Bekey 1977),  and (2)
planning creates a model of the future, and hence is
an  estimate of something that has not yet occur-
red. However, th^s model can still be an effective
tool for guiding management decisions by testing
different approaches against an objective (such as
minimizing  the amount  of  sediment  that  is
delivered to a stream) and evaluating the relative
magnitudes of the answers.

  This  chapter also  presents a simple  graphic
model for estimating the quantity of sheet and rill
eroded soil material delivered from the source area
to a stream channel. Although this model appears
feasible for application on all forest lands, it has
not been extensively tested. With additional  field
testing and experience, the range and nature of this
model's sediment delivery factors will be modified.

  Many of the techniques used to evaluate surface
erosion and sediment delivery are based on subjec-
tive evaluations of land characteristics. Persons
who have the responsibility for evaluating erosion
and sediment  delivery  need a general  technical
background in soil science and hydrology, as well as
field experience  in  forest management.  This
chapter presents charts, tables, and formulas that
are needed to use the MSLE and sediment delivery
index procedures. Examples are  provided in both
this chapter and  chapter  VHI  to illustrate  a
systematic approach  to quantifying surface soil
erosion on forest lands.
                                              IV.l

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                         DISCUSSION: SURFACE SOIL LOSS
GENERAL  CONCEPTS  OF SURFACE SOIL
                    LOSS


  Surface erosion is the wearing away of the land
surface by water,  wind,  ice, or other geological
agents. In this chapter, surface soil loss  is dealt
with specifically as the mechanical detachment by
water of mineral soil particles and organic material
from the soil surface. Other forms of erosion such as
soil mass movement, piping,  and gully  are not
covered.
  The energy for soil particle detachment by water
may be provided by  rainfall impact and/or shear
from  flowing water (e.g., runoff). The impact of
raindrops on an exposed soil surface breaks down
the surface  structure and detaches  soil particles
and individual aggregates from the soil. Unless the
soil surface  is  protected  in  some way by a low
vegetative canopy and a mineral or organic surface
mulch, this raindrop and runoff energy can detach
tremendous quantities of mineral and organic soil.
  Detachment  by  raindrop  impact  removes soil
uniformly over  a broad area  of exposed soil. Such
soil  loss may  be almost imperceptible and is
usually referred to as sheet or rill erosion. Raindrop
splash enables thin,  sheet flow to  transport
detached particles a short distance to areas of more
concentrated water flow.
  Detachment  by overland  flow usually occurs
with small concentrations of flowing water in rills.
Enough  flow  energy must  be available so the
hydraulic forces  exceed  the soil's resistance to
detachment.  Consequently, little soil detachment
by water flow will occur on  areas with thin sheet
flow,  near ridge tops, on very flat slopes, or where
surface runoff rates are low.
  The separation of surface erosion into  rill and
sheet components is conceptually useful. Sheet ero-
sion is a product of either raindrop impact or sheet
flow and  is relatively uniform over the surface. This
distinction is important in determining the type of
control strategy that  might be used (see "Chapter
II,  Control Opportunities"). If  it  can be
demonstrated that rill erosion is the primary con-
tributor to the surface erosion total, then  the con-
trol strategy would be directed toward dealing with
overland flow as an eroding agent. Such a strategy
would vary somewhat both in scope and in general
approach from one designed to deal with erosion
from raindrop impact or sheet flow.
  Further discussion on surface erosion concepts
may be found in articles by Bennett (1934), Ben-
nett (1974),  Cruse  and  Larson (1977),  Ellison
(1947),  Foster and  Meyer (1975),  Guy  (1970),
Horton  (1945), Meyer and others (1975 and 1976),
and Smith and Wischmeier (1962).
       Detachment By Raindrop Impact


  Three principal factors affect the amount of soil
detached by raindrop impact. The first factor is the
interception of rainfall by the overstory or tree
canopy. Dohrenwend (1977) reports that overstory
canopies are not likely to protect the forest floor
from the erosive impact of raindrops. In some cases
raindrop energy is amplified by the canopy when
the  intercepted  water  falls  as  larger  drops
(Chapman 1948,  Trimble and Weitzman  1954).
The second factor is  interception by the under-
story. The rainfall energy transmitted through the
overstory canopy may be intercepted by an under-
story canopy — of shrubs, herbs or grass — growing
near the surface. The amount of energy reduction,
if any, depends upon drop size and fall distance
(Dohrenwend 1977). In a natural forest the surface
is protected by a third factor, a mat of litter con-
sisting of leaves, needles, and other organic debris
accumulated from the overstory  and understory
canopies. This litter mat absorbs a great deal of the
energy reaching the soil surface. If the depth of the
litter  mat  exceeds the penetration depth of the
raindrops, it is assumed that no mineral soil will be
detached (Simons and others 1975). The net effect
of the three layer screen — overstory canopy, un-
derstory canopy, and litter — can be a reduction of
rainfall impact energy to very near zero at the soil
surface.
  The litter layer and organic material in contact
with the soil will contribute  the greatest erosion
protection. Reduction of precipitation energy  by
the overstory canopy is not generally considered to
be  significant. The overstory plays a  greater,
though less direct, role by replenishing the  litter.
                                              IV.2

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        Detachment By Surface Runoff


  Any surface runoff that may occur in the natural
forested environment generally moves over the soil
below the litter layer. The rate of energy expended
for this flow is low because water moves through lit-
ter at a lower velocity than it would over the sur-
face of bare ground. Consequently, the detachment
energy of the  water flow and thus the quantity of
soil that is detached, both become very low where
good litter cover is present.
  Where the litter layer is removed or the soil is
compacted, the infiltration rate is decreased. This
allows a  given volume of rainfall to produce  a
greater proportion of overland flow than  would
otherwise  occur,  and more  runoff energy is
available to be expended on the soil surface.
      Environmental Changes Created By
            Silvicultural Activities
   Which Affect Surface Soil Loss Potential
  In the natural forest environment, soil loss from
sheet and rill erosion is usually small. Only when
the natural environment is disturbed by logging,
road building, fires, or unusual activities, does soil
loss increase (Fredriksen 1972) and become a major
source of non-point pollution. The environmental
changes due to silvicultural activities that are dis-
cussed  on the following pages often  result  in in-
creased soil loss due to destruction of the natural
protective soil cover, exposure and disturbance of
the soil surface, and/or increased runoff.
  Reduction of the  overstory canopy. — The
primary silvicultural activity is felling and logging.
Reduction of the overstory canopy decreases rain-
fall interception and may either cause an increase
or decrease in rainfall  energy reaching the ground
surface, depending on the nature of the storm and
characteristics of the canopy. There is some indica-
tion that rainfall energy under hardwood canopies
may be greater than under conifer canopies (Swank
and  others 1972, Trimble and Weitzman 1954). If
particular canopies intercept and  coalesce  water
droplets, then removal of these canopies  could
result in lower rainfall energy at the ground sur-
face.

  Removal or  alteration  of understory. —
Silvicultural  activities often remove  or seriously
alter the understory vegetation when the objective
is to eliminate vegetative competition to promote
the regrowth of timber. The result of brush removal
is a net reduction in the effectiveness of the under-
story  to intercept precipitation.  When this in-
terception value is lost, the rainfall energy moves
closer to the ground surface.

  Disturbance of the litter layer.  — The litter
layer, probably the most important factor in the
forest environment for absorbing rainfall energy, is
subject to  damage by  forest  management  ac-
tivities, such  as logging.  In cases where logs are
dragged repeatedly over the same area, the litter
layer may be  destroyed and bare mineral soil ex-
posed. Where the litter layer is shallow, the amount
of exposed mineral soil may be great. Furthermore,
planting and site preparation, designed to favor the
establishment of trees, may involve destruction of
the protective  litter layer. Burning for site prepara-
tion may consume  the litter layer  and  expose
mineral soil, especially if the fuel is heavy and/or
the site is dry. Other activities, such as raking or
piling slash, also tend to destroy the litter layer and
expose large quantities of mineral soil. The  overall
effects of these activities are elimination of protec-
tive material  covering the mineral soil, and  soil
compaction, which  affects  the  infiltration  and
erodibility properties of the  soil surface.
  Creation  of bare soil areas. — In addition to
the possible changes within  felling  and logging
units, machine-construction of areas such as roads
(required to access and remove the  timber) and
landings can expose extensive areas of mineral soil.
These constructed areas usually have few rainfall
intercepting surfaces above the soil  and are  fre-
quently the  major source of erosion produced sedi-
ment.
  Creation  of channels. — Using heavy  equip-
ment  and  skidding logs  across  the  soil surface
creates ruts, gouges, or channels. When water is
collected and concentrated in these channels, flow
energy and erosion potential are greater than if an
equal amount  of water were dispersed over the en-
tire slope area.
  Creation  of hydrophobic conditions from fire.
An extremely hot fire will consume essentially
all  of the overstory foliage, understory vegetation,
and surface  litter layer leaving the soil surface ex-
posed to the rainfall energy of future storms. If the
soil is coarse textured, it may become hydrophobic
following intense burning, i.e., shedding water as
runoff rather than allowing infiltration to occur. A
hydrophobic soil condition frequently occurs when
                                               IV.3

-------
volatile organic compounds  condense on  cooler
subsurface  soil particles  during burning and,
thereby, leave a thin waxy surface that resists wet-
ting. Since soil non-wettability can increase surface
runoff, greater  flow energies are available for soil
particle detachment and transport.
  Creation of other situations. — Soil mineralogy
can promote non-wettability in some cases. For ex-
ample, soils  with  high  amounts of  volcanic ash
become hydrophobic if they become very dry. Soil
microorganisms often  create barriers to water in-
filtration  during  dry  periods.  Although   these
organisms,  such as lichens, may protect the soil
against erosion, the additional runoff may con-
tribute to soil loss elsewhere on the slope.
 PROCEDURAL CONCEPTS: ESTIMATING
            SURFACE SOIL LOSS
  This section discusses the concepts necessary for
estimating surface soil loss and for evaluating the
individual parameters involved. It is organized ac-
cording to  a  conceptual understanding of surface
soil loss and corresponds to the flow chart  (fig.
IV.l).
  An outline of the overall procedure for estimating
sediment delivery to a stream from surface erosion
sources is presented in "The Procedure" section of
this chapter. A detailed example for estimating
surface soil  loss is  provided in "Chapter VIII:
Procedural Examples." All concepts discussed here
are necessary for using the overall procedure.
  Two  different approaches  are  recognized by
agricultural and forest scientists for estimating sur-
face soil loss. The first of these is an empirical ap-
proach  —  predictive  equations  developed from
analyses of data. The second is the use of process
models — models developed through an analysis of
cause and  effect relationships. Although process
models may  ultimately  be a more flexible  tool
producing  more accurate answers  over  a wider
range of conditions that can be obtained from em-
pirical models, they are  still in the  development
stage.  In addition,  process  models often require
more data than  are generally available. For these
reasons,  process models are not recommended as
tools for predicting soil loss within the forest en-
vironment.
  This  chapter  presents an  empirical procedure
for estimating soil loss and adapts it to specific
silvicultural problems. The  Universal Soil Loss
Equation  (USLE),  originally developed  by
Wischmeier and Smith (1965) for use on midwest
agricultural soils,  has been  modified for use  in
forest environments.  The cropping  management
(C) factor and the erosion control practice factor
(P) used in the USLE have been replaced by a
vegetation-management (VM) factor to form the
Modified Soil Loss Equation (MSLE). The follow-
ing discussion of MSLE and  its various factors is
based on  discussions  in "Agricultural Handbook
282" (Wischmeier  and Smith 1965)  and "Upslope
Erosion Analysis"  (Wischmeier 1972).

  The modified soil loss model (MSLE) is:
                A =  R K L S VM         (IV.l)

where:
  A  = the estimated average soil loss per unit
         area  in  tons/acre  for the time period
         selected for  R (usually 1 year.) It is not
         intended to reflect climatic extremes of a
         given year.
  R  = the rainfall  factor, usually expressed  in
         units of the rainfall-erosivity index, El,
         and evaluated from the iso-erodent map,
         figure IV.2  (U.S.  Department   of
         Agriculture,  Soil Conservation Service
         1977).
  K  = the soil-erodibility factor,  is usually ex-
         pressed in tons/acre/EI units for a specific
         soil in cultivated continuous fallow tilled
         up and down the slope.
  L  = the slope length factor is the ratio of soil
         loss from the field slope length to that
         from  a 72.6-foot (22.1 m)  length on the
         same soil, gradient  cover, and  manage-
         ment.
  S  = the slope gradient factor,  is the ratio  of
         soil loss  from a  given field gradient  to
         that from a 9-percent slope with the same
         soil,  cover, and management.
  VM = the vegetation-management factor,  is the
         ratio of soil  loss from land managed un-
         der specified conditions to that from the
         fallow condition on which the factor K is
         evaluated.

  Numerical values for each  of the factors have
been determined from research data. These values
may differ somewhat  from one field or locality to
another; however,  approximate numerical values
for any site may be  estimated using figures and
tables present in this  chapter or in the example in
chapter VIE.
                                              IV.4

-------
  The MSLE procedure can be used as a guide for
quantification of potential erosion of different land
management strategies only if the principle  in-
teractions on  which  the equation is based  are
thoroughly understood. Failure to understand the
equation and its  background will lead  to misuse
and/or invalid interpretation. Each MSLE factor is
discussed on the following pages to clarify the as-
sumptions of the model. If the assumptions do not
represent the actual processes in the forest environ-
ment, then predicted erosion values will not be the
same as actual  erosion. The MSLE model may be
used to compare  effects  of different land  uses on
soil loss if the assumptions used for evaluating each
factor in the MSLE do not  change with changing
land uses.
            The Rainfall Factor, R


  Wischmeier and Smith (in press) reports that the
function of the rainfall factor, R, is to quantify the
interrelated erosive forces of rainfall  and runoff
that are a direct and immediate consequence of
rainstorms.  It reflects all erosive rains occurring
throughout the year in addition to annual maxima.
  Since  the  rainfall  factor, R, represents  an
average annual value,  the MSLE estimates average
annual soil loss. Soil  loss estimates should  not be
made for specific storms or specific time periods
without modifying the R factor to include a runoff
variable and using other MSLE values appropriate
for  the  specific  events. Even then, soil loss  es-
timates for  specific events  are subject to much
greater error than estimates  of average annual soil
loss.
Energy-Intensity Values, El

  Factor R is based on a rainfall energy-intensity,
El, parameter which is linearly proportional to soil
loss when all  other  factors  are  held constant
(Wischmeier 1972).
  The iso-erodent map (fig. IV.2) presents average
annual El values for the contiguous United States.
The lines on the  map join points  with the same
erosion-index value  (which implies  equally erosive
average annual rainfall) and are called iso-erodent
lines. The value of R in erosion units per year along
each iso-erodent is  the value of R in the  erosion
equation.
  The average and the maximum storm values at a
particular location will vary widely from year to
year. An analysis of rainfall records at 181 stations
indicated that maximum storm values tend to fol-
low log-normal  frequency  distributions  that  are
usually well defined by continuous records of from
20 to 25 years (Wischmeier and Smith in press).
  El is an interaction term that reflects the com-
bination of raindrop splash erosion and  runoff
detachment of soil particles from bare soil. The
sum of computed storm El values for a given time
period is a numerical measure of the erosivity of all
the rainfall within that period. The rainfall erosion
index  at a  particular location  is the longtime-
average yearly total of the storm El  values. The
storm El values reflect the interrelations of signifi-
cant rainstorm  characteristics. Summing  these
values to compute the erosion index adds the effect
of the frequency of erosive storms within the year.
  Increases in rainfall energy due to driving winds
were   not  included  in  the  rainfall  factor
(Wischmeier  and  Smith  1958,  1965). Megahan
(1978)  suggests that wind can increase rainstorm
erosion by as much as one order  of magnitude
because the force vector of wind increases with the
sin  of  the slope angle. Therefore, on  steep slopes
wind becomes an important factor.
Determining The Rainfall Factor

  R is the number of erosion index units occurring
in an average year's rainfall for a site and may
either be computed or taken from a prepared map
(fig. IV.2).
It is defined as:
where:
                                                                     R= EL
                                                                          100
                                         (IV.2)
  E   = the total kinetic energy in foot-tons/acre
         inch of rain for each storm. For a storm to
         be included, it must be greater than 0.5
         inches (12.7mm) and be separated from
         other storms by  more than 6 hours.
  I   = the maximum 30-minute intensity in in-
         ches/hour for  the  area, over the same
         time period used for estimating soil loss.
  The El value for any particular rainstorm can be
computed from recording  rain gage data with  the
help  of a  rainfall  energy  table   published  by
Wischmeier and Smith  (1958).
                                              IV.5

-------
  LOCATION
R - INDEX MAP
% SILT & VERY FINE SAND
% SAND
% ORGANIC MATTER
SOIL STRUCTURE
SOIL PERMEABILITY
 SLOPE LENGTH
SLOPE GRADIENT
' GROUND COVER %
 SURFACE
L UNDERSTORY CANOPYl
      TOPO MAP
'DELINEATED TO SHOWN
  CUTTING BLOCKS
  ROADS & LANDINGS
  WATERSHED DIVIDES/
  SOIL TYPE
  .STREAMS
  RAINFALL
   FACTOR
  SOIL ERODABILITY
       FACTOR
SLOPE LENGTH
   FACTOR
     VEGETATIVE
     MECHANICAL
       FACTOR
        AREA
                                                 ESTIMATED
                                      POTENTIAL SOIL LOSS PER UNIT AREA
                                                                    ESTIMATED SURFACE EROSION
                                                                       SEDIMENT DELIVERED
                                                                            TO STREAM
                   Figure IV. 1.—Flowchart of the procedural concepts involved in estimating
                             sediment delivery from surface erosion sources.

-------
/SOIL PERMEABILITY\
/ MAX 15 MIN STORM \
  DISTANCE ACROSS
\   DISTURBANCE   /
\   TO STREAM   /
/%
 %
\%
VERY FINE SAND)
SILT
CLAY
    TRANSPORT
       AGENT
% SOIL SURFACE
IN CONTACT WITH
VEGETATION OR
  VEGETATIVE
    RESIDUE
f SLOPE }I
\ SHAPE y y
 SURFACE
ROUGHNESS;
    TEXTURE OF
 ERODED MATERIAL
DISTANCE FROM
  LOWER EDGE
OF DISTURBANCE
  TO STREAM
 OPTIONAL
SITE FACTOR-
    USER
 SELECTED
                                      SEDIMENT DELIVERY INDEX
                                                                                 PROCEDURAL STEP.
                                                                                 COMPUTATION OR
                                                                                   EVALUATION
                        Figure IV.1.—Flow chart of the procedural concepts involved in estimating sediment delivery from surface
                                                  erosion sources — continued.

-------
                   W.H. Wischrrteier, ARS, 1977
Figure IV.2.—Iso-erodent map illustrating average annual values of the rainfall factor, R.
                                       IV.8

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Figure IV.2.—Iso-erodent map Illustrating average annual values of the rainfall factor, R — continued.
                                             IV.9

-------
  Research exploring the drop size and terminal
velocity of various storm events (Gunn and Kinzer
1949, Laws and Parsons  1943) led to derivation of
an equation for E in terms of the intensity of the
storm in foot-tons/acre inch as  (Wischmeier and
Smith  1958):
               E = 916 +  331  logioi      (IV.3)
where:
  E   = storm kinetic  energy  in  foot-tons/acre
         inch
  i   = the intensity of the storm in inches/hour
  An optional method of determining R requires
rain gage data from sites which have  30-minute
rainfall records available. Using equation IV.3 and
rainfall data, calculate the E value for each storm.
Using equation IV.2 and rainfall data, calculate R.
  The more commonly used method for determin-
ing R is to take locational values of the rainfall fac-
tor, R,  directly from the iso-erodent map (fig. IV.2)
(USDA, Soil Conservation Service 1977). The iso-
erodent map shows R values ranging  from <20 to
550. The erosion index measures only the effect of
rainfall when separated from all other factors that
influence  erosion. Points lying between the in-
dicated iso-erodents  may  be approximated by
linear interpolation.
  If all soil and topography factors were exactly the
same everywhere, average annual soil losses  from
plots maintained in continuous  fallow,  tilled up
and down the slope,  would differ in direct propor-
tion to the erosion-index values. This potential dif-
ference  is, however, partially offset by differences
in soil,  topography, vegetal cover, and surface lit-
ter. On fertile soils in the high rainfall areas of the
United  States, good vegetal  cover protects the soil
surface  throughout most of  the year;  heavy plant
residues, where present, provide  excellent ground
cover during the dormant season. In the regions
where  the  erosion index is  extremely  low,  good
ground  cover is often limited to a relatively short
period of time. Natural soil erosion may occur both
in semiarid regions because of poor ground cover,
and in humid regions (with good ground cover) due
to high precipitation.
R Values For Thaw And Snowmelt

  Wischmeier and Smith (in press) have observed
that, in the Pacific Northwest, up to 90 percent of
the erosion on the deep loess agricultural soils has
been associated  with surface thaws and snowmelt
runoff. This type of erosion is not accounted for by
the rainfall erosion index, but it occurs frequently
both in the northwest and in portions of the central
western  states.  With  this  erosion,  the  linear
precipitation relationship  would not  account  for
peak  losses in early spring since as the winter
progresses, the soil  becomes  increasingly  more
erodible. As the  soil moisture  profile  is filled  by
winter precipitation,  the surface soil  structure
breaks down by  repeated freezing and thawing,
resulting in puddling, surface sealing and a reduc-
tion in infiltration. Additional research on the ero-
sion processes and means of erosion control during
snowmelt runoff is needed.
  Until research designs a more acceptable method
of calculating  erosion  indices, Wischmeier and
Smith (in press) suggest that the early spring ero-
sion by runoff from snowmelt, thaw or light rain on
frozen soil may be used in the soil loss computa-
tions by adding a subfactor, Rg, to the erosion index
to obtain the R  factor.  Investigations with only
limited data indicate that the best estimate of Rs
may be obtained by taking 1.5  times the local,
December through March, precipitation, measured
as inches  of water. For example, a location in the
northwest that has an erosion index of 20 (fig. IV.2)
and averages 12 inches (304.8mm) of precipitation
between December 1 and March 31 would have an
estimated average annual R factor of [1.5(12) + 20]
or 38.
  Snowmelt runoff erosion may also  be a  signifi-
cant factor in the northcentral  and eastern states,
particularly on loessal soils. Where experience in-
dicates that this type of runoff exists, it should be
included in factor R evaluation.
        The Soil Erodibility Factor, K


  The term "soil credibility" is distinctly different
from  "soil  erosion."  The  rate of soil erosion,
designated by A  in the soil loss equation, may be
influenced  more by land  slope,  rainstorm
characteristics, cover, and  management than by
inherent properties of the soil. This difference in
soil erosion, due only to soil properties, is referred
to as  soil credibility.
  The physical properties of the soil, as they relate
to the inherent susceptibility of that soil to erode,
are discussed in soil science literature (Barnett and
Rogers 1966, Browning and others 1947, Lillard and
others 1941, Middleton and  others 1932, Olsen and
Wischmeier  1963,  Peele and  others  1945,
Wischmeier and Mannering 1967). Wischmeier and
                                               IV.10

-------
Mannering (1969) developed an empirical expres-
sion of soil  erodibility  as  a function of 15 soil
properties and their interrelationships. Their equa-
tion,  however, appeared to be too complex and
demanding for general use, and the soil erodibility
factor was later redefined in terms  of  five soil
properties.
  Soil characteristics that influence soil erodibility
by water are: (1) those that affect the infiltration
rate,   permeability,  and  total  water-holding
capacity, and (2) those that resist the dispersion,
splashing, abrasion,  and transporting forces of the
rainfall and  runoff  (Adams and  others 1958).  A
number of attempts have been made to determine
criteria  for  characterizing  soils  according  to
erodibility (Lillard and others 1941, Middleton and
others 1932,  Peele  and others 1945,  Smith and
Wischmeier  1962).  Generally, however, soil clas-
sifications used for  erosion prediction have been
largely subjective and have  led  only to  relative
rankings.

  The relative erosion hazard (erodibility) of dif-
ferent soils is difficult to judge from field observa-
tions.  Even soils with a relatively low erodibility
factor may show signs of serious erosion under cer-
tain conditions, such as on long or steep slopes or in
localities  having numerous  high-intensity  rain-
storms. A soil with a  high natural erodibility factor,
on the other  hand, may show little evidence of ac-
tual erosion under gentle rainfall when it occurs on
short and gentle slopes or when the best possible
management is practiced. The effects of rainfall,
length and degree of slope,  and vegetative  cover
management are accounted for in the MSLE equa-
tion by the symbols R, L, S,  and VM. The soil-
erodibility factor, K, is evaluated independently of
the effects  of the  other  factors and will vary
depending on the intrinsic properties  of the soil.

  Original values of the soil-erodibility factor, K,
in the MSLE were determined experimentally for
agricultural lands. A standard plot for determining
K experimentally is  72.6 feet (22.1m)  long with a
uniform  lengthwise  slope  of 9 percent, in con-
tinuous fallow, tilled up and down the slope. Con-
tinuous fallow, in this case, is land  that has been
tilled and kept free of vegetation for a  period of at
least  2 years or until prior  crop residues  have
decomposed.  During the  period  of  soil loss
measurements, the  plot  is plowed and placed in
conventional  corn seedbed condition each spring
and is tilled as needed to prevent vegetal growth or
serious surface crusting. This provides a reproduci-
ble soil surface condition.
  When all of these conditions are met, each of the
factors, L, S, and VM, has a value of 1.0 and  K
equals A/EI,  where A is the soil loss per unit area
(tons/yr) and El is the erosion index.
  For a particular soil, K is the rate of erosion per
unit of erosion index from standard plots on that
soil. Conditions  selected as  unit  values  in the
USLE represent the predominant slope length and
the  median  gradient  on  which  past erosion
measurements in the United States were made.  It
is not known if a K factor determined in this man-
ner is completely appropriate for use on forest soils.
Until research clarifies this point, K will have to be
used on the basis  of its original derivation.
  Direct measurements of K on replicated stan-
dard plots reflect  the combined effects of all the
variables that significantly influence the ease with
which a soil  is eroded by rainfall and  runoff. To
evaluate K for soils that do not usually occur on a
9-percent slope, soil loss data from plots that meet
all other specified conditions should be adjusted to
a 9-percent slope by means of the slope factor in the
Universal Soil Loss  Equation (Wischmeier 1972).
Determining The Soil Erodibility Factor

  Both the equation and nomograph (fig. IV.3)
(Wischmeier and others 1971) for determining K
values are discussed. The nomograph can be used
for all soils; however, the given equation is limited
as described below.
  Soil erodibility equation. — Solution of the soil
erodibility equation is possible with data normally
available  from standard  soil profile descriptions
and routine laboratory analysis.  The  equation
should not be used with soils having more than 70
percent silt and very fine sand or with soils having
a low clay content  because  beyond 70 percent,
equation IV.4 no longer fits the nomograph curve.
The equation for soil erodibility is:
  K =  (2.1  X 10-6) (12-Om) (M1-14)
        + 0.0325(8-2) + 0.025(P-3)
(IV.4)
where:
  K  = soil erodibility factor used in the MSLE.
  Om = percent organic matter; if organic matter
         is >4%, use 4%.
  M  = particle  size  parameter:  [percent  silt
         (100 - %  clay)] where  very fine sand
         (0.05-0.1  mm) is included in the silt frac-
         tion.
  S  = code for  soil structure:
                                               IV.ll

-------
    Soil Structure Class

    very fine granular
    fine granular
    medium or coarse granular
    blocky, plately, or massive
          MSLE
          Code

            1
            2
            3
            4
      =  Code  for  Soil  Conservation Service
         permeability classes.
         These are for the soil profile as a whole
         (Wischmeier and others 1971), based on
         estimated  water  flow  in inches/hour
         through saturated,  undisturbed cores un-
         der ' j-inch head of water (U.S. Depart-
         ment  of Agriculture,  Soil Conservation
         Service  1974):
      Permeability class
               MSLE
Permeability rates Code
    in/hr
very slow
slow
slow to moderate
moderate
moderate to rapid
rapid
<0.06
0.06-0.2
0.2 -0.6
0.6 -2.0
2.0 -6.0
>6.0-20.0
6
5
4
3
2
1
  General permeability classification guides and
discussion from the USDA Soil Survey Manual are
presented  to  help  determine  the  appropriate
permeability  classification.  Soil  permeability is
that quality of the soil that enables it to transmit
water or  air. It can be measured quantitatively in
terms of  rate of flow of water through a unit cross
section  of saturated soil  in unit  time,  under
specified temperature  and hydraulic conditions.
Percolation under gravity with a '/2-inch head and
drainage  through cores can be measured by a stan-
dard procedure involving presaturation of samples.
Rates of percolation are expressed in inches  per
hour.
  In the absence  of precise  measurements, soils
may be placed into relative  permeability classes
through  studies of  structure,  texture, porosity,
cracking, and other characteristics of the horizons
in the soil profile in relation to local use experience.
The observer must learn to evaluate the changes in
cracking  and in aggregate stability with moisten-
ing. If predictions are to be made of the respon-
siveness of soils to drainage or irrigation, it may be
necessary to determine the  permeability  of each
horizon and the relationship of the soil horizons to
one another and to the soil profile as a whole. Com-
monly, however, the percolation rate of a soil is set
by that of the least permeable horizon in the solum
or in the immediate substratum.
  The  infiltration rate, or entrance of water into
surface horizons, or even into the whole solum, may
be rapid; yet permeability may be slow because of a
slowly  permeable layer directly beneath the solum
that influences water movement within the solum
itself. The rate of infiltration and the permeability
of the plow layer may fluctuate widely from time to
time because of differences in soil management
practices, kinds of crops, and similar factors (U.S.
Department  of Agriculture,  Soil  Survey Staff
1951).

  Some  guides for using the permeabililty codes
are: (1) fragipan soils fall into category 6; (2) soils
with surface permeability  underlain  by massive
clays or silty clays should be coded 5; (3) silty clay
or silty clay loam soils having a weak angular or
subangular blocky structure and moderate surface
permeability should be coded 4; (4) if the subsoil
structure remains moderate or strong, or texture is
coarser than silty clay loam, the code should be 3;
and (5) if the soil remains open, does not form sur-
face seals, and the profile does not restrict intake,
the code should be 1 or 2.
  Soil credibility nomograph for factor K.  —
Equation IV.4 is based on the nomograph with one
exception — the  relationship for K changes when
the silt-very fine sand fraction exceeds 70 percent.
This change is not included in the equation, but is
incorporated  into the  nomograph (fig.  IV.3).
Instructions for use of the nomograph are included
in the  figure.
  In certain situations, improved K values may be
obtained by using the following suggestions:
  1. For  claypans  and  fragipans, it may  be
     desirable to use separate credibility factors for
     dry  and  wet  seasons by using  different
     permeability  ratings in  the  nomograph.
     Permeabilities  should  be  reduced  in wet
     seasons, but not for thunderstorms during the
     dry  season  (Wischmeier  and others 1971).
     Weighted annual mean erodibility factors for
     wet and dry seasons can be computed as fol-
     lows:
                                         R _(KWMW + KdMd)
                                                 Mw + Md
                              where:
                                K   = weighted mean erodibility,
                                Kw  = soil erodibility during wet season,
                                          (IV.5)
                                              IV. 12

-------
Figure IV.3.—Nomograph lor determining the soil credibility factor, K.

-------
  Mw =  number of wet months with erosive rain-
         fall and/or snowmelt runoff,
  Kd  =  soil credibility during dry season,
  Md =  number of dry months with erosive rain-
         fall and/or snowmelt runoff,

  2.  Large surface material, such as gravel, is not
     included  in  K  value determinations,  but
     rather is a part of the vegetation-management
     factor (VM) as it relates to mulch or ground
     cover.
  3.  High clay subsoils  containing iron  and
     aluminum oxides react differently than sur-
     face soils containing those oxides (Roth and
     others 1974). In this situation the nomograph
     solution for K may not  apply  (Wischmeier
     1976).
  The Soil Conservation Service has determined K
factor values  for some soils. Information about
these tables should be obtained from Soil Conser-
vation Service soil  scientists who are familiar with
the soils  in a given area.
The Topograhic Factor For  Slope Length and
                 Gradient, LS
  The rate of soil erosion by water is affected by
both  slope  length  and  slope  gradient  (percent
slope). The two effects are represented in the ero-
sion equation by L and S, respectively. In field ap-
plication of the equation, however, it is convenient
to consider the two  as a single topographic factor,
LS, because of the  interactions between the two
parameters.
  Numerous plot studies (Wischmeier 1966) have
shown that soil loss in  tons/unit area  is propor-
tional to some power of slope length. Since the fac-
tor L is the ratio of soil loss from the slope length of
interest to that from a standard 72.6-foot(22.1m)
slope, the value of L may be expressed as:
               L = (X 772.6)'
                               (IV.6)
where:
  X    = slope length in feet, and
  m   = 0.2 for slope gradients that are <1.0%
  m   = 0.3 for slope gradients >1.0 but<3.0%
  m   = 0.4 for slope gradients >3.0 but <5.0%
  m   = 0.5 for slope gradients that are >5.0%
  m   =0.6 for slope  gradients over 12% with a
         natural permeability code of 5 or 6 where
         infiltration is very low, such as on con-
         struction  sites and  roads  (Wischmeier
         and  Smith in press).
  The effect  of slope  length on soil loss is due
primarily to a greater accumulation of runoff on
longer slopes.  Runoff velocity  increases  as water
volumes increase, and both detachment and tran-
sport  capacity  increase geometrically  with  in-
creased velocity  (Wischmeier 1972).
  The exponent m is significantly influenced by
the interaction of slope length and gradient, but it
may also be influenced by soil characteristics, type
of  vegetation,   and  management  practices.
Generally, increases in slope gradient, slope length,
or increases in runoff (due to reduced infiltration
caused  by either soil type  or  vegetation-
management  practices) create  a need for a larger
slope length exponent (m) in equation IV.6 (Foster
and others 1977).
Slope Length Factor, X

  Slope length is defined as the distance from the
point of origin of overland flow to: (1)  the  point
where the slope decreases to the extent that deposi-
tion  begins; (2)  the point where runoff enters a
well-defined channel that may  be part  of a
drainage network or a constructed channel such as
a terrace  or diversion  (Wischmeier  and Smith
1965); or (3) the downslope boundary of a distur-
bance. A change in land use on a slope does not
change the effective slope  length unless the runoff
from the upper slope is diverted off of the area in
some manner.
Slope Gradient Factor, S

  A. W. Zingg (1940) concluded that soil loss varies
as the 1.4 power of percent slope. Musgrave (1947)
recommended use of the 1.35  power of percent
slope. Based on analyses of the data, Smith and
Wischmeier (1957) proposed the relationship:
= (0.43 + 0.30s + 0.043s2)
                                             «
                        6.613
where:
  s   = slope gradient expressed as percent slope,
         and
  S   = slope gradient factor.
                                              IV.14

-------
  The  data  adequately  support  this slope
relationship up to a 20 percent slope. Since the
equation is parabolic, slope relationships cannot be
extrapolated  indefinitely  beyond gradients of 20
percent and still obtain accurate estimates of soil
loss from the MSLE. However, the MSLE may be
used on slopes over 20 percent to compare the soil
loss effects of several  different  management ac-
tivities.
Determining The Topographic Factor

  The LS factor is the expected ratio of soil loss/
unit area (tons/yr) on a slope as compared to a cor-
responding soil  loss from  the standard plot  (9-
percent slope, 72.6 feet (22.1 m) long). For specific
combinations of slope  length  and slope gradient,
this ratio may be taken directly from a length-slope
nomograph (fig. IV.4). For example, a 10-percent
slope that is 360 feet (109.7 m) long would have an
LS ratio of 2.6.
  Values of LS for slope gradients and lengths not
shown on the nomograph may be computed using
the following equation. A correction factor has been
added to equation  IV .7 to avoid  using sines of
angles.
   LS
=(
  \72.
  / 10,
  \10,0
).43 + 0.30s + 0.043s2>
        6.613       J
            000+sV
                                         (IV.8)
  s    = slope gradient in percent, and
  m   = an exponent based on slope gradient from
         equation IV.6.
  The use of equation IV.8 or figure IV.4 assumes
that the slopes are uniform from top to bottom.


Irregular Slopes

  Slopes are usually convex or concave. Use of an
average gradient for the entire slope  length sub-
stantially underestimates soil loss from the convex
slopes and overestimates the loss from concave
slopes (Foster and Wischmeier 1973). If equation
IV.8 or the nomograph (fig. IV. 4) is used on convex
slopes, the gradient of the steeper segment should
be used as the overall slope gradient for estimating
the LS factor. On a concave slope, where deposition
may occur on the lower end of the slope, the  ap-
propriate length and gradient to use is the  point
                                             where the slope flattens enough for deposition to
                                             occur.
                                               In  cases where the slope  characteristics change
                                             from top  to bottom,  averaging  the  slope
                                             characteristics and applying one LS factor will not
                                             accurately estimate soil loss. The calculations for
                                             irregular slopes (Foster and Wischmeier 1973) are
                                             recommended  on areas where several  slopes are
                                             combined. This  equation accounts for situations
                                             where runoff comes from one slope segment and
                                             flows to the next. However, if substantial sediment
                                             deposition will occur due to a change in vegetative
                                             cover or diversion of water, this procedure cannot
                                             be used because  it does not account for sediment
                                             deposition.
                                               Foster  and  Wischmeier's  (1973)  equation is
                                             presented here, and an example of its use may be
                                             found in chapter VIII.
LS
1
Xe
n
• 2
j-l
/„ xm + l
/ Vi
\(72.6)m
                                                                          (72.6)'
                                                      10,000
                                                           10,000
                                                                                      (IV.9)
                                 in which:
                                   Xe   =
                                   j
                                   *j   =

                                   XJ4  =
                                   s    =
                                   m   =
overall slope length in feet,
slope segment index,
the length in  feet from  the top  to the
lower end of any segment j,
total slope length above segment  j,
slope in percent,
an exponent based on slope gradient from
equation IV.6, and
slope factor    °-43  +  °'30s + °-043s2
                     6.613
            for s2 segment j (Eq. IV.7)
                                               Foster and  Wischmeier (1973) developed  an
                                             alternative procedure for performing several steps
                                             in the solution of equation IV.9 for irregular slopes.
                                             The set of graphs (figs. IV.5 and IV.6) eliminates
                                             the need for logarithms, a  slide rule,  or  an
                                             electronic calculator to raise the slope length values
                                             to needed powers. These figures  are  a family of
                                             curves for specific slopes  ranging from 0.5 percent
                                             to 140 percent. Each figure uses  the  appropriate
                                             value  for m as previously discussed.
                                             IV.15

-------
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Figure  IV.4.—Nomograph for  determining the topographic
              factor, LS, on simple slopes.
                        IV. 16

-------
  The graphs (figs. IV.5 and IV.6) are based on the
following equation which is a portion of equation
IV.9.
M =
              72.6
 10.000
10,000+
                                         (IV.9a)
where:
  M   = derived factor for simplifying calculation
         of LS on irregular slopes,
  S   = slope steepness factor from equation IV. 7,
  s   = slope gradient in percent,
  X   = slope length in feet, and
  m  = an exponent based on slope gradient from
         equation IV.6.
  The symbol M is plotted on log-log graph paper
against  values of slope  length  with curves  for
specific slopes within the body of the graphs.
  To illustrate the graphic procedure for obtaining
the LS factor for irregular slopes, a road with cut-
and-fill  slopes (fig. IV.7) has been divided into seg-
ments representing the cut slope, the roadbed sur-
face, and the fill slope. It has been assumed that
sediment will not accumulate on the roadbed. The
first segment (cut slope) has a slope length of  4.8
feet  (1.46 m) at 66.7 percent gradient, the second
segment (roadbed surface) has a slope length of 12
feet  (3.66 m) at 0.5 percent gradient, and the third
segment (fill slope) has a slope length of 4.8 feet
(1.46 m) at 66.7 percent. The values are Xi = 4.8, X2
= 16.8, and X3 = 21.6 = Xe. Data for this procedure
are tabulated into table IV. 1.

  For the first segment, enter figure IV.6 at 4.8 on
the horizontal axis, move upward to the curve for
70  percent slope (for greater accuracy,  values
between can  be interpolated) and read MZ = 29 on
the vertical scale. The upper end of this segment is
at zero length so Ma - Mi = 29.
  For  the second segment, use the graph for 0.5
percent slope entering the graph with lengths of
16.8 feet and 4.8 feet. For those, M2 = 1, MI =  0.25
and M2 - MI = 0.75. Repeat this procedure for seg-
ment 3.
  The effective LS for any segment is obtained by
dividing (MS - MI) by the length of the segment as il-
lustrated. The overall LS value of 5.8 shown in the
last column was obtained by dividing the  sum of
the (M2 - MI) by the total length (124.7/21.6 = 5.8).
The detail provided by the last two columns of the
tabulation may  be helpful  in  designing effective
erosion control practices for each segment.
  These values  for  LS,  using this  graphic ap-
proach,  are   not exactly  the  same  as  those
calculated from equation IV.9, as shown in chapter
VIII. This is due to errors inherent in using graphs.
Although  these  small  errors exist,  the numbers
determined with the graphs  are  sufficiently ac-
curate for general use.
            Table IV.1.—Example of data tabulation when using graphs for obtaining LS value for irregular
              Segment   Slope
                                                M2
                                                       Ml
                                             Segment   Segment
                                             Length      LS
                                               (ft)
1
2
3

66.7
0.5
66.7

4.8
16.8
21.6

0.0
4.8
16.8

29
1
270

0.0
0.25
175

29
0.7
95
124.7
4.8
12.0
4.8
21.6
6.0
0.1
19.8
5.8
                                               IV. 17

-------
1QOOO
 1,000
   .10
                                                                100
1,000
                                         X = Slope Length (ft.)
Figure IV.5.—Values of n for use with irregular slopes (0.5 -100%) with appropriate values of m (0.2, 0.3, 0.4,
                                              and 0.5).
                                               IV. 18

-------
 10,000
  1,000
/t  100
    10
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                                10.000
                               10,000+S
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                                                    77777.
                                                      77/77
                                                     f / //
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                             10
                                         100
                                  X= Slope Length (ft)
              Figure IV.6.—Values of M tor use with irregular slopes (10-140%) where m = 0.6.
                                                             Wi
                                                                         7
                                                 1,000
                                      IV.19

-------
Figure IV.7.—Generalized cross section of outsloped road.
                       IV.20

-------
   The Vegetation-Management Factor, VM


  The effects of vegetative  cover  and  forest
silvicultural activities on soil detachment by rain-
fall and  runoff are numerous and varied.  Forest
residues from silvicultural  activities  may  be
removed, left on the surface, incorporated near the
surface, plowed under, or burned. When left on the
surface, they may be chopped or they can remain
as left by the harvesting operation. Seedbeds may
be left rough with the capacity for surface storage
of rainfall and sediment,  or they  can  be left
smooth. Different combinations of these variables
and possibly other conditions will have different ef-
fects on  a soil's susceptibility to erosion. In addi-
tion, the effectiveness of residue management will
depend on the volume and distribution of remain-
ing residues. This in turn depends on rainfall dis-
tribution, on the soil fertility level, and  on other
management decisions  that affect the amount of
vegetative productivity  on a given site.
  The VM factor in the Modified Soil Loss Equa-
tion is the ratio of soil loss from land managed un-
der specified conditions to the corresponding loss
from  tilled, continuously  fallow  conditions of a
standard plot. This factor measures the combined
effect of all the interrelated cover and management
variables discussed above.
  Soil loss that would occur on a particular site if it
were in a continuous fallow condition is computed
by a product,  R K L S, in the MSLE. Actual loss
from an  area is usually much less than  the com-
puted amount; just how much less depends on the
particular stage of growth and development of the
vegetal cover,  and the condition of the soil surface
at the time when rain or snowmelt occurs.
  The VM factor of the MSLE attempts to com-
bine vegetative  cover and soil surface  conditions
into one numerical factor. Use of the VM factor is
facilitated by separating it into three distinct kinds
of effects and evaluating each type as a subfactor:
Type I — effects of canopy cover, Type n — effects
of mulch or close growing vegetation in direct con-
tact with the soil surface, and Type El — residual
effects of land use (Wischmeier 1975).
Effects Of Canopy Cover, Type I

  Leaves and branches that do not directly contact
the soil surface are effective only as canopy cover.
Canopies close to the surface have some influence
on  the  impact  energy  of  falling  raindrops.
Waterdrops falling from a canopy may have ap-
preciable force at the soil surface depending on
canopy height and drop  size (Dohrenwend 1977).
  Figure IV.8, taken from Wischmeier (1975) shows
canopy effects of water drops for different amounts
of canopy ground cover and canopy heights. If pos-
sible, increase in drop size because of canopy in-
terception is ignored,  or is assumed to be offset by
the fact that some of the intercepted water moves
down the stems to the ground. The canopy factors
for various percentages of cover at heights of 0.5, 1,
2, and 4 m  may be obtained directly from figure
IV.8. For a 60 percent canopy cover at a height of
1m, for example,  the canopy  factor is  0.58. This
means that the effective El with the canopy is only
58 percent of the actual El of the rainfall, and the
expected erosion would also be only 58  percent of
that predicted by the El obtained from the iso-
erodent map.
                    Table IV.2—Velocities (m/sec) of falling waterdrops of different sizes (mm)
                                 falling from various heights (m) in still air
Median
drop diam.

2.00'
2.251
2.501
3.001
3.502







Drop fall height
0.5
2.89
2.93
2.96
3.00
3.04
1.0
3.83
3.91
3.98
4.09
4.19
2.0
4.92
5.07
5.19
5.37
5.55
3.0
5.55
5.74
5.89
6.14
6.37
4.0
5.91
6.14
6.34
6.68
6.98
6.0
6.30
6.63
6.92
7.37
7.79
20.03
6.58
7.02
7.41
8.06
8.63
            1Laws J.O. 1941. Measurement of fall-velocity of water drops and rain drops. Transactions of the
            American Geophysical Union 22:709-721. From Wischmeier 1975.
            'Extrapolation of values given by Laws (1941).
            'Values in the last column are considered terminal velocities.
                                              IV.21

-------
  Figure IV.8 is based on a medium drop size of 2.5
mm for both the rain and droplets formed on the
canopy. If the  3.35  mm droplets  measured  by
Chapman (1948) on a red pine plantation are as-
sumed to  be characteristic for most tree canopies
(Trimble and Witzman 1954), figure IV.8 should be
modified.  When modifying, subfactor  values for
complete canopy cover can be computed from the
data in table IV. 2 below for a given diameter using
equation IV.10:
              Cioo = 0.169V   0.356      (IV.10)
where:
  Cioo = factor  for canopy  effect at 100 percent
         ground cover, and
  V    = velocity, in meters/second, for  a water
         drop of a given diameter, falling a given
         distance.
  Values for less than complete canopy cover can
be found by drawing a line on figure IV.8, from the
point calculated for 100 percent cover to the upper
left corner where other lines are converging.
FACTOR FOR CANOPY EFFECT
8 6 g g I
^fe






*Av
• dr<

^
X





erac
jps

* ^ ^
N.
^




e fa
rom


s^
N
s



Ihe
can


"* **
^
V



ght
opy


~».
^
N
\


of



.^

^
XXN
\







^

X
\





""• .



s '
\
0.


im*
2m*
K
1m*
X
X
s
5m*

       0     20     40     60     80    100
       PERCENT GROUND COVER BY CANOPY
Effects Of Mulch And Close Growing Vegeta-
tion, Type II

  A mulch on the soil surface is much more effec-
tive than an equivalent percentage of canopy cover.
There  are  two reasons  for this: (1) raindrops in-
tercepted by  the mulch have very little remaining
fall height  to the ground, and their impact on the
soil surface is essentially eliminated;  and (2) a
mulch that makes good contact with the ground
also reduces  the velocity of runoff. This, in turn,
greatly reduces the runoffs potential to detach soil
material.
  Effectiveness of type II cover can be expressed on
the basis  of percent  surface  cover  using  the
relationship in figure IV.9 (Wischmeier 1975).  If
FACTOR FOR MULCH AND
CLOSE GROWING VEGETATION
3 8 S g g I
\
\










\
\










\
N









\










X










s.









x










X









^^
^*s









^
Figure IV.8.—Influence of vegetal canopy on effective El, as-
  suming bare soil beneath the canopy, and based on the
  velocities of free-falling waterdrops 2.5 mm in diameter
  (Wischmeier 1975).
                                                        PERCENT OF SOIL SURFACE COVERED BY MULCH
                                                     Figure IV.9—Effect of plant residues or close-growing stems
                                                      at the soil surface on the VM factor (does not Include sub-
                                                      surface root effects) (Wischmeler 1975).
the cover includes both canopy and surface mulch,
the canopy and mulch factors  overlap  and the
canopy factor can not be fully  credited. Impact
energy  of a raindrop striking the mulch is dis-
sipated at that point regardless of effects of canopy
interception on its fall energy. The mulch factor is
always taken at full value, and the canopy factor is
reduced so that it applies only to the percentage of
the soil surface not covered by mulch.
                                               IV.22

-------
  To illustrate  this, assume a 30 percent mulch
cover  combined with a  60 percent canopy  at  a
height of  1  m. From figure IV.9,  the  factor for
mulch cover effect is 0.47.  Because of the 30 per-
cent mulch cover, the effective canopy cover is only
0.70 of the overall 60 percent cover, or 42 percent.
Entering figure  IV.8  with a  42  percent canopy
cover, we obtain a factor of 0.70 for canopy effect.
The factor for  this combination of canopy and
mulch cover is  the product of the two subfactors
(0.47 times 0.70), which equals 0.33.
 Residual Effects Of Land Use, Type III

   This category includes residual  effects  of  the
 land use on soil structure, organic matter content,
 and soil density; effects of site preparation or lack
 of preparation on surface roughness and porosity;
 roots and subsurface stems; biological effects; and
 any other factors affected by land use.
   Figure IV. 10  (Wischmeier 1975) was developed
 for Type HI effects on undisturbed pasture, range,
 forest, and idle land. The initial point (0.45) for the
 curves is an estimate of the long-term effect of no
 tillage and no vegetation. It was obtained from 10-
 year soil loss  records on a 12 percent slope of silt
 loam soil that was not tilled after the first year but
 was kept free  of vegetation and traffic. The rate of
        0     20     40    60     80    100
     PERCENT OF BARE GROUND WITH FINE ROOTS
Figure IV.10.—Effects of fine roots in topsoil on the VM factor.
  These values do not apply to cropland and construction
  sites (Wischmeier 1975).
soil loss per unit of El declined annually until it
leveled off at about 45 percent of the rate for the
first 2 years of the study. The curvature and end-
points of the curves were based on comparisons of
soil losses from meadow with those from plots hav-
ing equivalent percentages of surface cover in the
form of applied straw mulch.
  If an area has been cultivated or totally scalped
so that all of the fine roots from trees, grass, and
weeds are destroyed, then the Type HI  effect as
described does not exist.
Sediment Filter Strips

   Sediment  filter strips  are  areas  of residue  or
other kinds of effective sediment traps. If surface
areas that are completely open (having minimal
amounts of residue and soil mixed with residue) are
separated from each other by small  filter strips, a
factor of 0.5 should be included in the calculations
(Wischmeier  1972).  If the  open areas are not
separated by sediment filter strips, use a factor of
1.0 (see example in Chapter VIII).
Determining The Vegetation-Management
Factor

  Use either previously published  values  or  es-
timate the VM factor using Type I, n and El sub-
factors.
  Previously published tables (tables IV.3, IV.4,
IV.5, and IV.6) and graphs (figs. IV.11 and IV.12)
are reproduced in this chapter with specific VM
values for use under some conditions. Table IV.3
applies only to  construction sites  (e.g., roads).
Tables from  other literature are usually expressed
in terms of the C factor for the Universal Soil Loss
Equation. The  C factor is considered appropriate
only  if  the  forest situation and the  situation
represented in the  published  tables have the fol-
lowing  in common:   the  management  practice
described  in the  table   must have the  same
characteristics as the one to be used, the vegetative
recovery rates must be the same, and all assump-
tions must be the same in practice as presented in
the tables. In addition there will be significant  er-
rors if terminology used in  the tables does not mean
exactly the same thing from one part of the country
to another.
  Type I, II, and in values determined from figures
IV.8, IV.9, and IV. 10 are multiplied to obtain a VM
value for use in equation IV. 1. An example of this
procedure is  given in  chapter VIE.
  This  estimation  procedure  for  VM does  not
recognize the effects of time on fine root-density. It
is  recognized   that  some  changes  in soil
characteristics which influence erodibility will  oc-
cur due to various silvicultural activities. If these
soil changes are for a short time (only a few years),
                                               IV.23

-------
Table IV.3.—VM factor values for construction sites
                (Clyde et al. 1976 ).
Condition
1.


















2.





3.


Bare soil conditions
freshly disked to 6-8 inches
after one rain
loose to 1 2 inches smooth
loose to 12 inches rough
compacted buldozer scraped up and down
same except root raked
compacted bulldozer scraped across slope
same except root raked across
rough irregular tracked all directions
seed and fertilize, fresh
same after six months
seed, fertilize, and 12 months chemical
not tilled algae crusted
tilled algae crusted
compacted fill
undisturbed except scraped
scarified only
sawdust 2 inches deep, disked in
Asphalt emulsion
1 ,250 gallons/acre
1,210 gallons/acre
605 gallons/acre
302 gallons/acre
151 gallons/acre
Dust binder
605 gallons/acre
1,210 gallons/acre
VM factor

1.00
0.89
0.90
0.80
1.30
1.20
1.20
0.90
0.90
0.64
0.54
0.38
0.01
0.02
1.24
0.66-1 .30
0.76-1.31
0.61

0.02
0.01-0.019
0.14-0.57
0.28-0.60
0.65-0.70

1.05
0.29-0.78
4. Other chemicals
   1,0001 b fi ber glass roving with
       60-150 gallons/ acre
   Aquatain
   Aerospray 70,10 percent cover
   Curasol AE
   Petroset SB
   PVA
   Terra-Tack

5. Seedlings
   temporary, 0 to 60 days
   temporary, after 60 days
   permanent, 0 to 60 days
   permanent, 2 to 12 months
   permanent, after 12 months

6. Brush

7. Excelsior blanket with plastic net
0.01-0.05
  0.68
  0.94
0.30-0.48
0.40-0.66
0.71-0.90
  0.66
  0.40
  0.05
  0.40
  0.05
  0.01

  0.35

0.04-0.10
they are accounted for  by the VM  factor. Long-
term changes in soil credibility, as a result of ac-
tivities changing soil structure and  permeability,
should be evaluated by  changing the K factor.
  Adjustments for surface microrelief or roughness
and adjustments for different contouring practices
are also  lacking  from  this presentation. More
research needs  to  be directed toward these  ad-
ditional VM subfactors.
               Seasonal Adjustments For VM

                 If necessary, the VM factor can be adjusted for
               seasonal changes using equation IV. 11 to obtain an
               average annual VM value.


                             = (VMgMg + VMdMd)      dv.n)
                                    Mg +  Md
               where:
                 VM =  weighted  mean vegetation-management
                        factor,
                 VM =  VM  factor for growing season,
                  M =  number of growing season months with
                        erosive rainfall,
                VM d=  VM  factor for dormant season,
                  Md=  number of dormant months with erosive
                        rainfall and/or snowmelt runoff.
      Estimated Soil Loss Per Unit Area


  When all of the parameters of the MSLE (equa-
tion IV. 1)  have been assigned the proper values,
the factors are multiplied to obtain an estimate of
soil  loss for  a  specific  unit  area.  The  answer
generally  will  be expressed  in tons/acre/year. If
other units of area and time are chosen for use in
the  MSLE, they  must  be applied  consistently
throughout the equation.


Converting MSLE To Metric1


  The  rainfall intensity-energy equation in  the
metric system is: E = 210.3 + 89 logioi where E is
kinetic  energy in  metric-ton  meters/hectare/cen-
timeter of rain, and i is  rainfall intensity in cen-
timeter/hour. A logical counterpart to the English-
system  El  is the  product: storm energy in metric-
ton meters/hectare times the maximum 30-minute
intensity  in centimeter/hour.  The magnitude of
this product would be 1.735 times that of the El as
defined in English units. The factor for  direct con-
version  of K to metric-tons/hectare/metric El units
is 0.2572.
                'The equations used in this chapter usually require data to be
              in the English system (inches, feet, Ibs., etc.) with the exception
              of equation IV.10. Substitution of metric data without making
              appropriate changes in equation coefficients will result in er-
              roneous answers.
                                                IV.24

-------
  Table IV.4.—"C" factors for permanent pasture, rangeland, idle land, and grazed woodland1
                              (Soil Conservation Service 1977)
           Vegetal canopy
    Type and height       Canopy
    of raised canopy2      cover3
Type4
Cover that contacts the surface

        Percent ground cover

No appreciable
canopy
Canopy of tall
weeds or short
brush
(0.5 m fall ht.)


Appreciable brush
or bushes
(2 m fall ht.)



Trees but no appre-
ciable low brush
(4 m fall ht.)



%


25

50

75

25

50

75

25

50

75


G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
G
W
0
.45
.45
.36
.36
.26
.26
.17
.17
.40
.40
.34
.34
.28
.28
.42
.42
.39
.39
.36
.36
20
.20
.24
.17
.20
.13
.16
.10
.12
.18
.22
.16
.19
.14
.17
.19
.23
.18
.21
.17
.20
40
.10
.15
.09
.13
.07
.11
.06
.09
.09
.14
.085
.13
.08
.12
.10
.14
.09
.14
.09
.13
60
.042
.090
.038
.082
.035
.075
.031
.067
.040
.085
.038
.081
.036
.077
.041
.087
.040
.085
.039
.083
80
.013
.043
.012
.041
.012
.039
.011
.038
.013
.042
.012
.041
.012
.040
.013
.042
.013
.042
.012
.041
95-100
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
.003
.011
  1AII values shown assume (1) random distribution of mulch or vegetation, and (2) mulch of ap-
preciable depth where it exists. Idle land refers to land with undisturbed profiles for at least a period of
three consecutive years. Also to be used for burned forest land and forest land that has been harvested
less than 3 years ago.
  2Average fall height of water drops from canopy to soil surface.
  'Portion of total-area surface that would be hidden from view by canopy in a vertical projection (a
bird's-eye view).
  4G: Cover at surface is grass, grasslike plants, decaying compacted duff, or litter at least 2 inches
deep. W: Cover at surface is mostly broadleaf herbaceous plants (as weeds with little lateral-root network
near the surface), and/or undecayed  residue.
                      Table IV.5.—"C" factors for undisturbed woodland
                              (Soil Conservation Service 1977)
Effective canopy1
% of area
100-75
70-40
35-20
Forest litter2
% of area
100-90
85-75
70-40
"C"3
factor
.0001 -.001
.002-. 004
.003-.009
                   'When effective canopy is less than 20 percent, the area will be
                 considered  as grassland or idle land for  estimating  soil  loss.
                 Where woodlands are being harvested or grazed, use table IV.4.
                   2Forest litter is assumed to be at least 2 inches deep over the
                 percent ground  surface area covered.
                   3The range in "C" values is due in part to the range in the per-
                 cent area covered. In addition, the percent of effective canopy and
                 its height has an effect.  Low canopy is effective in reducing
                 raindrop impact  and in lowering the "C" factor. High canopy, over
                 13 m, is not effective in reducing raindrop impact and will have no
                 effect on the "C" value.
                                          IV.25

-------
Table IV.6.—"C" factors for mechanically prepared woodland sites
     (U.S. Department of Agriculture Soil Cons. Serv. 1977.)
Percent of soil covered with residue





in contact with soil surface Soil Condition and Weed Cover"
Excellent Good
NCS WC5 NIC
None
A. Disked, raked or bedded1 2 .52 .20 .72
B. Burned3 .25 .10 .26
C. Drum chopped3 .16 .07 .17
1 0% Cover
A. Disked, raked or bedded1 2 .33 .15 .46
B. Burned3 .23 .10 .24
C. Drum chopped3 .15 .07 .16
20% Cover
A. Disked, raked or bedded1 2 .24 .12 .34
B. Burned3 .19 .10 .19
C. Drum choppd3 .12 .06 .12
40% Cover
A. Disked, raked or bedded1 2 .17 .11 .23
B. Burned3 .14 .09 .14
C. Drum chopped3 .09 .06 .09
60% Cover
A. Disked, raked or bedded1 2 .11 .08 .15
B. Burned3 .08 .06 .09
C. Drum chopped3 .06 .05 .06
80% Cover
A. Disked, raked or bedded1 2 .05 .04 .07
B. Burned3 .04 .04 .05
C. Drum chopped3 .03 .03 .03
1 Multiply A. values by following values to account for surface
roughness:
Very rough, major effect on runoff and sediment storage,
depressions greater than 6" 0 40
Moderate 	 0.65
Smooth, minor surface sediment storage,
depressions less than 2" 0 90
2The "C" values for A. are for the first year following treatment. For
A. type sites 1 to 4 years old, multiply "C" value by 0.7 to account for
aging. For sites 4 to 8 years old, use table IV. 4. For sites more than 8
years old, use table IV.5.
3The "C" values for B. and C. areas are for the first 3 years following
treatment. For sites treated 3 to 8 years ago, use table IV. 4. For sites
treated more than 8 years ago, use table IV.5.
'Soil condition and weed cover descriptors.
Excellent— Highly stable soil aggregates in topsoil with litter and
fine tree roots mixed in.
Good— Moderately stable soil aggregates in topsoil or highly stable
soil aggregates in subsoil (topsoil removed during raking), only traces
of litter mixed in.
Fair— Highly unstable soil aggregates in topsoil or moderately
stable soil aggregates in subsoil, no litter mixed in.
Poor— No topsoil, highly erodible soil aggregates in subsoil, no lit-
ter mixed in.
5For each of the soil conditions, "C" factors are provided for no live
vegetation (NC column) and for 75% cover of grass and weeds hav-
ing about 0.5 meter fall height (WC column). For weed and grass
cover other than 0% and 75%, "C" values may be interpolated.
WC

.27
.10
.07

.20
.10
.07

.17
.10
.06

.14
.09
.06

.11
.07
.05

.06
.04
.03




























Fair
NC

.85
.31
.20

.54
.26
.17

.40
.21
.14

.27
.15
.10

.18
.10
.07

.09
.05
.03




























WC

.32
.12
.08

.24
.11
.08

.20
.11
.07

.17
.09
.06

.14
.08
.05

.08
.04
.03




























Poor
NC

.94
.45
.29

.60
.36
.23

.44
.27
.18

.30
.17
.11

.20
.11
.07

.10
.06
.04




























WC

.36
.17
.11

.26
.16
.10

.22
.14
.09

.19
.11
.07

.15
.08
.05

.09
.05
.04




























                          IV.26

-------
55
to
                       0.50
                       0.40
                       0.30
                    o
                    (0
                       0.20-
                       0.10-
,0% Canopy of
    Forbs and
-   Weeds
                                             ,2556 Canopy of Forbs and
                                                 Weeds
                                                           s 50% Canopy of Forbs and
                                                          '     Weeds
                                   75% Canopy of Forbs and Weeds
                                     10        20       30       40        50       60       70

                                                          Percent Ground Cover of Forbs
                                                                80       90       100
                                     Figure IV.11—Relationship between grass density and the VM factor (Clyde and others 1976).

-------
    0.50
    0.40'
            \
 O  0.30
•*->
 o
 (0
          \
>  0.20-
    0.10-
               -0% Canopy of Tall(0.5m)
                   Grass and Weeds
   ,25% Canopy of Tall Grass
       and Weeds
                                    , 50% Canopy of Tall Grass and
                                         Weeds
                 75% Canopy of Tall(0.5m)Grass and
                     Weeds
10
20
                                     30       40       50        60        70

                                       Percent Ground  Cover of Grass
80
100
                Figure IV.12—Relationship between forb density and the VM factor (Clyde and others 1976).

-------
  For practical purposes, it would be expedient to
redefine the  unit-plot as having a length of 25
meters and a slope of 10 percent, to derive K on the
basis  of those dimensions, and to recompute the
slope-effect chart. The translated  values would be:
L   =
LS =
         Xo.5/5 where X is slope length in meters;
         and  S  = (0.43 +  0.30s  + 0.043s2)7.73
         where, s = percent slope. Combining the
         two,
              . 00111s2 + 0.00776s  + 0.0111).
          (Wischmeier 1972).
            Erosion Response Units

  Potential  sources  of non-point pollution  con-
stitute site specific problems within an individual
watershed. To estimate the magnitude of a specific
onsite soil  loss  and  to  identify the  particular
drainageway  where  this  erosion  occurs,  the
watershed  must be divided into  homogeneous
areas. Delineating erosion response units requires
identification of individual activities such as roads,
landings,  cutting blocks, or skid trails, and the
relative contribution of each activity to potential
sediment yield.
Delineating Erosion Response Units
  The following information needs to be shown on
a series of maps or overlays in order to identify and
delineate erosion response units:
  1.  Topographic  information   showing
     hydrographic areas and channel network.
  2. Soil and vegetative resource information used
     for the quantification of surface erosion.
  3. Project proposal showing  the location  of
     roads,  trails, landings, cutting units, etc.
  The procedure for compiling these data  is ex-
plained by steps:
  Step 1. — Obtain a topographic map (fig. IV.13)
to show spatial relationships of the factors needed
in the quantification process. The amount of detail
desired and the amount that can be produced  by
the analysis will depend upon the scale and ac-
curacy of the base map.
  Step  2. — Extend the stream detail  shown  on
the topographic  base (fig.  IV. 14).   Perennial
streams, and in some cases intermittent streams,
will be  printed on the original topographic  base;
however,  this  does  not  completely define the
stream channel network within that watershed. It
is important that the displayed stream network be
extended to include all intermittent channels that
are definable on the basis of the contour lines. Each
channel should be extended toward the watershed
divide from channels originally identified on the
base map.  Field information, if available, should
be used to verify the final channel network.
  Step 3.  —  Delineate individual hydrographic
areas  (fig.  IV.15).  Draw the interior  watershed
boundaries or hydrographic divides separating the
extended channel  network that was identified in
step 2. At this point, a series of sub-watersheds or
hydrographic  areas  will  have  been  delineated
within the  watershed of interest.
  Step 4. — Since soils information is required for
the evaluation of onsite erosion,  soil mapping unit
boundaries should be drawn (fig. IV. 16). These soil
units may come from a standard soil survey, a soil
resource inventory, or  a land systems  inventory.
The soils may be  grouped so that the delineated
map units represent soils that are homogenous with
respect to texture (percent sand, silt, clay), organic
matter, permeability,  and  structure.  Vegetative
cover information, if available, should be mapped
to show the percent  surface area occupied by
vegetation,  mulch, rock, litter, and debris. Sedi-
ment delivery, as well as surface erosion, is greatly
influenced  by these factors; having them mapped
prior  to initiating  quantification of  erosion is
beneficial to the analysis.
  For the purpose of bookkeeping, it is necessary to
number these erosion response units consecutively.
Begin  near the  mouth of  the  watershed with
number "1" and proceed clockwise toward the head
of the watershed and back around the mouth on the
opposite side.
  Step 5.  — Stratify the problem as it relates to
the  proposed  silvicultural  activity by drawing
roads, cutting blocks, log landings, skid trails, and
other activities on an overlay for the topographic
base (fig.  IV. 17). Placing this information on an
overlay will make the maps more readable and will
also  facilitate  making  changes  in  a  proposal
without destroying the entire topographic base.
  Delineate the transportation  system first,  in-
cluding all existing and proposed roads, skid trails,
and aircraft landing areas. Then delineate the cut-
ting blocks as  precisely as possible relative to the
topographic base (fig. IV. 18). Other items, such as
decking areas and log  landings,  should  also be
shown on the topographic base whenever possible.
Once again, the detail that is shown will partially
determine the detail of the analysis.
                                              IV.29

-------
            Contour Interval  =  40 feet
Figure IV.13.—The Horse Creek watershed boundary.
                    IV.30

-------
      Contour Interval  =  40 feet
Figure IV.14.—Drainage net of the Horse Creek watershed.
                       IV.31

-------
                  Contour Interval =  40 feet
Figure IV.15.—Individual hydrographic areas of the Horse Creek watershed.
                                 IV.32

-------
                        Contour Interval =  40 feet
Figure IV.16.—Soil mapping unit boundaries for the Horse Creek watershed.
                               IV.33

-------
                          Contour Interval  =  40 feet
Figure IV.17.—Proposed transportation system (roads and log landings) for the Horse Creek watershed
                                          IV. 34

-------
                          1 mile =  5280 feet
                      Contour Interval = 40 feet
Figure IV.18.—Proposed cutting units for the Horse Creek watershed
                                       IV.35

-------
  Step  6.  — All  of  the  preceding information
should he incorporated onto a single map base or
preferably  onto  overlays using the  previous map
scale  (fig. IV. 19). The information in its overlaid
form  should  include the hydrographic areas,  the
soil and vegetation resources, and the proposed ac-
tivities within each erosion response unit.
  Step 7. — Further subdivisions of the proposed
activities are possible  to identify specific sources
contributing eroded materials to the drainageway
via  separate  delivery  routes  within  each
hydrographic  area.  The  degree  to which  the
silvicultural activities are subdivided is important
to the final  quantification process  and may be
useful  in  ultimately  applying  controls to specific
parts of an area. The more detailed the subdivision
of activities  the  more  complex  the accounting
procedure and the more detailed the answer.

  Step 8. — List the  potential sediment  source
areas on worksheets  (IV.1-IV.8) by activity types
for each erosion response unit identified in step 4.
                                                                       Hydrographic Area
                                                                           Boundary
        Figure IV.19.—Composite map of all topographic and management treatments for the Horse Creek
                                    watershed, hydrographic area 3.
                                              IV.36

-------
                                             WORKSHEET I V.I

                      Soil  characteristics for the
watershed

Soi 1 group
Top so i 1
1
Subsoi 1
Top so i 1
9
Subsoi 1
Top so i 1
•*,
Subsoi 1

E
+- —
c
 CM






T3
ID E
W E
CD m
c o
-i- — •
C M- O
-O
I- 1_ «—
0) 0) •
Q. > O






_^J
Percent
"coarse silt'
0.062-0.05 mn







CM
o
0
+-
C O
Q) 1
o -t- in
1- — O
0 ._ .
DL in o







E
C CN
0 0
U 5-O
1_ (D •

-------
WORKSHEET IV.2
watershed erosion response unit management data for use in the MSLE and
sediment delivery index, hydrographic area

Erosion
response
un it
1 .
2.
5.
4.
5.
D.
7.
8.
9.
10.
1 1 .
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Slope
length of
disturbed
area (ft)


























Slope
gradient of
disturbed
area (%)

























Length of
road
section
(ft)


























Average
width of
disturbance
(ft)

























Area
(sq.ft.)

























Area
(acres)


























-------
                                                                                                            2 of  3
                                                        WORKSHEET  IV.2—continued
Area with surface residues
Percent
of total
area
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Percent
of surface
with mulch

























Percent of
area with
fine roots

























Open area
Percent
of total
area

























Percent
of surface
with mulch
















\








Percent of
area with
fine roots

























Are open areas
separated by
f i Iter strips?

























Percent of
tot a 1 area
with canopy


























00
to

-------
                                                  3 of 3
WORKSHEET I V. 2—continued
Average
min imum
height of
canopy
(m)
1 .
2.
3.
4.
5.
6.
7.
8.
9.
10.
11 .
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Time for
recovery
(mo)

























Average
dist. from
disturbance
to stream
channel (ft)

























Overal I
slope shape
between
d i sturbance
and channel

























Percent
ground
cover in
f i I ten
str ip

























Surface
roughness
(qua I i -
tat i ve )

























Texture of
eroded
mater ial
(% si It +
clay)

























Percent
slope
between
disturbance
and channel


























-------
                            WORKSHEET IV.3
Estimates of soil  loss
for hydrographic area
and
delivered
     of
sediment by erosion
response unit
    watershed
Erosion response
un it










Soi 1
un it










R










K










LS










VM










Area
(acres)










Surface
soi 1 loss
(tons/yr )










SO,










Del i vered
sediment
(tons/yr)











-------
                                                             WORKSHEET IV.4
                                      Estimated VM factors for si IvicuIturaI  erosion response
                                      	 watershed,  hydrographic area 	
un its
Logging residue area
Erosion
response
unit
















Fraction
of
total
area
















Mulch
(duff &
residue)
















Canopy
















Roots
















Sub
VM
















Open area
Fraction
percent
of total
area
















Mulch
(duff &
res idue)
















Canopy
















Roots
















Fi Iter
str ip
















Sub
VM
















Total
VM
















fe

-------
                              WORKSHEET  IV.5



        Example of estimated monthly change  in VM  factor  following



  construction for road cuts and fills in	watershed,



                    hydrographic area	
Month
Sep.l/
OctJ/
Nov.
DecJ/
Jan.?/
Feb.2/
?/
March-'
Apr! if/
Mayf/
June^/
July^/
Aug.
Percent cover and VM subfactors
Mulch
Percent












VM












Canopy
Percent 1 VM
























Roots
Percent












VM












Monthly
VM












-' Begin seeding, enough rain  is assumed to ensure seed germination.


21
-  Snow cover with no erosive  precipitation.



-  Significant canopy effect developing.


4/
-  Snowmelt runoff occurs, some protective vegetative cover  lost  during

    winter.



-  Significant root network developing  from seeded grass.
                                   IV.43

-------
          WORKSHEET  IV.6
Weighting of VM values for roads  in
          watershed, hydrographic area
Eros ion
response
un it






























Cut or fill
Fract ion
of total VM
w i dth






























Roadbed
Fract ion
of total VM
w i dth






























Fi 1 1
Fract ion
of total VM
wi dth






























Weighted
VM






























               IV.44

-------
                                                                      WORKSHEET  IV.7




                                            Factors for  sediment  delivery  index  from  erosion response units  in




                                                                        watershed,  hydrographic area 	
Erosion
response
unit









Water
avai 1 abi 1 ity









Texture
of eroded
material









Percent
ground
cover
between
disturbance
and channel









Slope
shape
code









Distance
(edge of
disturbance
to channel )
(ft)









Surface
roughness
code









Slope
gradient
<»









Specific
site
factor









Percent
of total
area for •
polygon









SD|









fe

-------
                                WORKSHEET  IV.8

          Estimated tons of  sediment delivered to a channel  for  each
hydrographic area and  type of  disturbance  for  	 watershed

Hydro-
graphic
area



























Col umn
total
Distur-
bance
total
Percent
Cutting units
CC]




























CC2




























CC3




























CC4




























CC5































Land ings
LI




























L2




























L3






























Roads
Rl




























«2




























"3




























K4




























"5






























Total
tons/yr






























Per-
cent





























                                    IV.46

-------
                   Summary

  Once the data are accumulated,  a  specific es-
timate of surface soil loss can be made. To compute
an estimate of total soil loss for a unit area (one
acre), the MSLE must be applied to each activity
within the area. The unit area soil loss is multiplied
by the actual area that is disturbed by an activity
to obtain  an estimate of surface soil loss per ac-
tivity. Soil  loss for each activity is then added
together to  obtain  estimated total soil loss.  This
overall  procedure is further explained  in "The
Procedure"  section of this chapter.
    CONSIDERATIONS FOR REDUCING
                   EROSION

  Theoretically, it is possible to reduce soil loss by
making appropriate changes in any of the MSLE
factors. In actual practice, some factors are easier
to change than others. The following tabulation
describes the  basic  concepts  underlying  the
variable changes brought about by controls for sur-
face erosion. This conceptual presentation is to aid
in understanding controls and determining which
control practice to  use. Details of specific control
practices may be found in "Chapter II: Control Op-
portunities."
                                              IV.47

-------
MSLE
Factor
                          Preventive
      Mitigative
    R         Where soils have high credibility factors, plan
            silvicultural activities so that snowmelt rates are not
            increased over natural conditions. Use management
            techniques which will not create significant increases
            in the amount of solar energy reaching the forest floor.
                                                                 Reduce  snowmelt  runoff rates
                                                                 by intercepting the solar energy
                                                                 above the snow surface.
R
K
     LS
             Control over the rainfall portion of the R factor is not likely to occur because it is a
             function of overall weather patterns.
             Use management practices that do not reduce long-
             term soil permeability, structure, or organic matter
             content. For example, avoid soil compaction or crea-
             tion of conditions that destroy organic matter.
Increase long-term organic mat-
tor  ^r.K,fQi-it  i'n Łne  SOll  by
                   vegetative
                                                                ter  content  in
                                                                promoting   good
                                                                growth.  This  can  lead  to
                                                                desirable soil  structure  and
                                                                permeability.  Obtaining
                                                                desirable  soil texture changes
                                                                would be very difficult at best.

         Usually slope length and slope gradient effects must be considered together because a
         change in one also causes a change in the other.
L       Control  location and design of various types of con-
         struction to avoid creating long cut and/or fill slopes,
         large landings, and extensive activity areas.
                                                                     Locate various types of diver-
                                                                     sions, such as terraces, to reduce
                                                                     the distance water  can move
                                                                     over land.
             Control location and design of various types of construc-
             tion and  other activities on steep slopes.
                                                                 Reduce steep slopes, created by
                                                                 construction activities, by plac-
                                                                 ing soil and rock at the base of a
                                                                 cut slope and removing it from a
                                                                 fill slope.
    VM     Control and design forest activities to minimize forest
             floor destruction. Maintain adequate amounts of low un-
             derstory canopy. This is important where surface  resi-
             dues are few or lacking. A high overstory canopy may ac-
             celerate raindrop splash erosion from storms  in areas
             where the forest floor has  been destroyed. An  example
             might be a campground with little or no surface residue
             or understory canopy. Control the  use and intensity of
             fire on coarse-textured soils to prevent hydrophobic  con-
             ditions from developing.
                                                                 Add  mulch,   or  chemical
                                                                 binders, establish vegetation, or
                                                                 use other practices to change
                                                                 VM so that acceptable levels of
                                                                 soil  loss are  achieved.  Use
                                                                 various  mechanical methods of
                                                                 creating surface roughness  or
                                                                 small diversions, e.g., perform
                                                                 final  site preparation  on  the
                                                                 contour  rather than up  and
                                                                 down slope. Use wetting agents
                                                                 to reduce or reverse hydrophobic
                                                                 conditions    enough    to
                                                                 significantly  reduce soil  loss
                                                                 (Osborn and others  1964).
                                               IV.48

-------
APPLICATIONS, LIMITATIONS AND PRECAUTIONS:  SURFACE SOIL LOSS
  The  confidence limits  on predictions  by the
Universal Soil  Loss  Equation are the narrowest
(predictions are most accurate) for silt, silt loam,
and loam textures on uniform slopes of 5 to 12 per-
cent, and with  slope lengths of less than 400 feet
(122m) (Wischmeier 1972). Beyond these limits,
significant  extrapolation errors become more
likely. However,  the MSLE appears to have suf-
ficient accuracy for comparing estimated soil loss
from different silvicultural management practices
on a given  site over  a  wider range  of forest en-
vironmental conditions. Predicting long-term (5- to
50-year)  average  soil  loss  for a given situation is
limited  by  lack  of  available  data needed to
evaluate  the individual  terms  rather than the
overall model.  The prediction accuracy for forest
land may improve as research provides a more ac-
curate evaluation of the critical site factors over a
wider range  of conditions within the forest environ-
ment.

  Specific limitations of the MSLE are as follows:
   1. The MSLE is empirical; it indexes the quan-
     tity of soil loss  under various forest condi-
     tions and  does not always show the factors in
     correct relationships  with  actual  erosion
     processes. There are limitations due to the
     use  of empirical coefficients  and  fitted
     curves.
  2. The MSLE only estimates an amount of soil
     loss, but does not deal with the probability or
     chance of soil loss  occurring.
  3. The MSLE was developed to predict soil loss
     on an average annual basis. Soil loss predic-
     tions on a  storm-by-storm basis often are er-
     roneous because of the complicated interac-
     tion between forces governing soil loss rates
     that are not accounted for by the MSLE. On
     any given  site, these interactions may tend
     to average out over long periods of time so
     that their effect on long-term soil loss may be
     minimal.  The soil loss equation has been
     rewritten  in  several  attempts  to develop
     techniques to handle storm-by-storm losses
     (Foster and others  1977,  Williams  1975c,
     Williams and LaSeur 1976). The accuracy
     and reliability  of  such techniques  is
     questionable, and  it  is not recommended
     that they  be used for quantification.
4.  It is assumed in the MSLE that the K factor
   is a constant,  average value throughout a
   given  analysis  time period.  However,
   changes in surface particle size distribution
   (texture) due to freeze-thaw or ongoing ero-
   sion processes  will  affect  the value of  K.
   Some of these effects, if they are short-term,
   are  provided for by the VM factor. Long-
   term changes in the K factor due to soil com-
   paction which occurs on roads, from equip-
   ment operations, or  by animal traffic needs
   further study.
5.  The LS factor has a low level of sensitivity to
   potential errors in  the estimation  of slope
   length  because  it is raised to a fractional
   power.  However, an  error in slope gradient,
   particularly on steep slopes, can result in a
   large error in LS because of the parabolic
   form of the equation.
6.  The MSLE is most  accurate for VM values
   above 0.2.  As  VM  approaches 0.01 and
   below, the errors in the absolute estimate of
   soil  loss increase greatly;  the smaller VM
   becomes, the larger the potential absolute  er-
   ror.
7.  The rainfall erosion index (R) measures only
   the  erosive force of  rainfall and  associated
   runoff.  The equation  does not predict soil
   loss that is due solely to thaw, snowmelt, or
   wind.

8.  Relationships of a given MSLE parameter to
   soil  loss are often appreciably influenced  by
   the  levels of  all other MSLE  parameters
   (Wischmeier 1976). Graphs in figure IV.20 il-
   lustrate one example of this interrelationship
   for the K factor. Table IV.7 shows values
   used as constants in  this example. Using
   figure  IV.20 and table IV.7  together it  is
   shown how changing one parameter, while
   holding all others constant (either at high,
   moderate, or low levels), affects erodibility,
   the K factor. For example, Figure IV.20a il-
   lustrates the effects  upon the K factor when
   organic matter is varied from 0 to 6 percent
   and all other parameters are held constant.
   When  all  other  parameters  are  at low  or
   moderate levels,  changes  in organic matter
   do not appreciably affect erodibility.
   However, when all other parameters are held
                                             IV.49

-------
Table IV.7.—Values of organic matter, fine sand + silt, clay,
  structure,  and  permeability  used as constants when
  calculating K factor over a range of each parameter for low,
  moderate, and high values of K.
Relative Level of K

% organic matter
% fine sand + silt
% clay
structure
permeability
Low
6
10
90
4
1
Moderate
3
35
65
3
3
High
0
70
30
1
6
      at high levels,  changes in organic matter do
      have an appreciable influence on the K fac-
      tor. There is a similar graph for each of the K
      factor parameters showing the changes in K
      due to a change in a parameter.
   9.  There are additional  erosion processes  not
      accounted for in the MSLE that are  impor-
      tant  in making accurate predictions of  soil
      loss.  On steep slopes  wind is an important
      erosion factor  and may increase rainstorm
      erosion by up to one order of magnitude. Fall
      freeze-thaw processes  cause a change in  the
      median  particle  size  of eroded  material
      (Megahan 1978).
  10.  No adjustments are made for timing of rain-
      fall relative to vegetative growth periods. In-
      tuitively, the  amount of soil  loss would be
      different if most of the rainfall occurred dur-
      ing a vegetative dormant season rather than
      a growing period.
  11.  The  MSLE does not  separate  runoff and
      rainfall components of erosion. If this could
      be done, the accuracy of estimated soil losses
      might be improved in situations where  one
      factor is more  important than the other.
  12.  There does not appear to be any acceptable
      method to account for the influence of rock
      and stone on the soil surface. A suggestion is
      to view the rock or stone as a non-erodible
      part of the surface; however, because of the
      runoff from the surface of a rock, there might
      be more soil loss than would  occur without
      any rock.
  13.  Coarse-textured soils that are exposed to an
      intense fire may become hydrophobic, thus
      promoting more surface runoff after  a  fire
    than might have occurred  under natural
    vegetation. It is not known if adjusting the K
    factor  for  a change in permeability  will
    provide a satisfactory estimate of this effect
    on runoff-induced erosion.
14.  The equation does not account for sediment
    deposition that occurs in depressions within
    a field, at  the toe of a slope, along distur-
    bance boundaries, or in terrace channels on a
    slope (Wischmeier 1976).
15.  Gully erosion cannot be accounted for by the
    Modified Soil Loss Equation. (See appendix
    IV.A).  The  use of the soil loss  equation  is
    confined to sheet and rill erosion.
16.  The relationships of factors influencing ero-
    sion on soils that  are high in organic matter,
    that  have developed from  volcanic ash, or
    that  have  permafrost are  not well  under-
    stood. Use of the  soil loss equation for these
    soils  may  result in significant errors in the
    amount of predicted soil loss.
17.  The MSLE estimates average soil loss for 1
    year only.  Using MSLE for periods of over a
    year is briefly discussed in appendix IV.B.
18.  Accurate  soil loss estimates from roads and
    skid trails may not be obtained  where they
    intercept  surface  and subsurface  runoff in
    addition to  precipitation. The MSLE does
    not estimate soil loss by concentrated water
    flow, such as in a  road ditch.  (See Appendix
    IV.C: Controlling Ditch Erosion).
19.  In forest  areas  with a  dense overstory
    canopy, there is  a limit to map accuracy.
    When a topographic map is  prepared  from
    aerial photographs,  the technician making
    the map cannot see  the actual ground sur-
    face on the photograph —  only  the canopy
    top.  The  map maker  is  usually not ac-
    quainted  with the area,  but must still es-
    timate  the  canopy  height. Anything that
    would cause some trees to  grow taller than
    others  will  cause  errors in  delineating con-
    tour lines. For example,  a  small first-order
    stream channel with its additional moisture
    may cause trees to grow so  that the tops are
    level with tree tops on the drier interflueves
    between channels, and thus be mapped as a
    uniform ground surface.
                                               IV.50

-------
  "-
.7


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 0
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       10   20    30   40    50    60   70
      PERCENT SILT AND FINE SAND
Figure IV.20a.—Effect of organic matter content on K factor
  when other parameters are at  low, moderate, or high
  values.
Figure IV.20b.—Effect of silt and fine sand on K factor when   Q-
  other parameters are at low, .moderate, or high values.     O

                                                      O
                                                      <
Figure  I V.ZOc.—Effect  of  clay on K  factor when  other   "-  3
    parameters are  at low, moderate, or high values.
Figure IV.20d.—Effect of soil structure on K factor when other
    parameters are at low, moderate, or high values.
Figure IV.20e.—Effect of soil permeability on the K factor
when other parameters are at low, moderate, or high values.
.(
.6
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.3
.2
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                                                   IV.51

-------
                         DISCUSSION:  SEDIMENT DELIVERY
   GENERAL CONCEPTS OF SEDIMENT
                 DELIVERY
  To evaluate the  effects of  surface  erosion on
water  quality, it  is  necessary  to estimate the
amount of eroded material that might be moved
from the eroding site into a receiving stream chan-
nel system. Unfortunately, the processes  which
describe the delivery  of eroded materials are less
well understood than those for erosion, and data for
sediment delivery are scarce.
  Historically, the determination of the amount of
sediment that reached a stream channel revolved
around  the concept of delivery ratios (Gottschalk
and  Brune 1950, Maner 1958,  Maner and Barnes
1953, Roehl 1962, Williams and Berndt  1972). A
delivery ratio is the volume of material delivered to
a point  in the  watershed, divided by the gross ero-
sion estimated for  the slopes in  the  watershed
above that point. Values range from zero to one.
  Apparently, a characteristic  relationship of sedi-
ment yield to erosion  does not  exist. Many factors
influence a sediment delivery ratio; if these factors
are not uniform from one watershed to another, the
relationship between  sediment yield and erosion
shows considerable variation (Renfro 1975).
    Factors Influencing Sediment Delivery


  Sediment delivery from  a disturbed  site to a
stream channel is influenced to varying degrees by
the following  factors  (Foster and Meyer  1977,
Megahan 1974, Renfro  1975). (There may be other
factors, not listed here, that are also important in
given  situations.)


Sediment Sources

  In terms of effects upon a sediment delivery in-
dex, there are at least three ways to describe sedi-
ment  sources:
  1. Type of disturbance — Materials originating
    from logging areas, skid trails, landings, and
    roads seem to have a range of delivery ratios
    that  are  characteristic of each disturbance
    type.
  2. Type of erosion — Sheet, rill, gully, and soil
    mass movement have  one or more  sediment
     delivery parameters that are unique to that
     particular form of erosion.
  3. Mineralogy  of  the source  area  — Delivery
     ratios  are  influenced  by  various  physical
     characteristics  of sediment materials. Size,
     shape, and density of individual particles and
     their tendency  to form stable aggregates are
     usually reflected  by  their mineralogy. Wet-
     tability of particles  may be a  function  of
     mineralogy or  of unique biological systems
     both of which influence the efficiency of sedi-
     ment delivery.


Amount Of Sediment

  When the amount of potential sediment exceeds
the runoff delivery  capability, deposition  occurs
and the amount of sediment delivered to a stream
channel  is  closely  controlled by the amount  of
runoff energy. If  the amount of sediment  is less
than the runoff delivery capability, then no deposi-
tion will occur between the disturbed area and a
stream channel.
Proximity Of Sediment Source

  The distance that sediment must move and the
shape and surface area of the transport path all af-
fect the amount of material  that may be lost from
the transport system.
Transport Agents

  Surface runoff from rainfall and snowmelt is the
main agent for transporting eroded material. Sedi-
ment transport is dependent on the volume and
velocity of water as well  as  the character  and
amount of material to be transported.
Texture Of Eroded Material

  Individual particles of fine-textured material can
be moved easier than particles of coarse-textured
material because the finer  the particle, the less
transport  energy required. If  a  watershed  is
dominated by fine-textured material, it is likely to
have more material delivered to a stream channel
by surface runoff than an equivalent situation with
                                              IV.52

-------
coarse-textured material — assuming that soil ag-
gregates are not involved.
Deposition Areas

  Microrelief that results in surface depressions or
other irregularities will deliver less sediment than a
smooth, flat surface. Decreases in  slope gradient
also promote deposition of large size fractions of
transported material.
Watershed Topography

  Size of the drainage area, overall shape of the
land surface, (concave to convex), slope gradient,
slope length,  and stream channel density all affect
the sediment delivery ratio by varying amounts.
           Sediment Delivery Model


  From the previous discussion concerning factors
that influence sediment delivery over an area of
land, it can  be seen that the amount of eroded
material deposited between a disturbed site and a
drainage channel is due to a variety of interacting
factors. To aid understanding overland sediment
transport, the process can be divided conceptually
into two parts.
  The first requirement is a transporting agent
with sufficient energy to move the sediment. In this
case,  surface runoff is the  transporting agent.  Its
energy is a function of the  amount and velocity of
waterflow passing over a given area in a given time
period.
  The second part deals with factors which tend to
stop  or  slow the  movement of sediment and
waterflow over a slope. Microrelief, slope gradient,
slope length, slope shape, vegetation, and  surface
residues all play a part in reducing the amount of
sediment that will actually reach a delivery point
(Neibling and Foster 1977, Zingg 1940).
  The shape of the area over which sediment is
transported (fig. IV.21) also influences the amount
actually delivered to a drainage channel. In one
case, sediment entering delivery area A is funneled
so that a  given amount passes over progressively
less surface during transit. This reduces the oppor-
tunities for deposition and also increases the energy
of the transporting agent,  thus resulting in  in-
creased sediment delivery efficiency. At the other
extreme,  delivery  area C  spreads material and
water over progressively more area thus reducing
the  transporting energy  and increasing  oppor-
tunities for in-transit deposition. Delivery area B
represents  an intermediate situation between A
and C. A  relative comparison of the three areas
would have A delivering more sediment than  B,
which delivers more than C.
                          Figure IV.21.—Potential sediment transport paths (A,B, and
                                     C) for different parts of a slope.
                                              IV.53

-------
  Any working sediment delivery model must have
clearly defined factors which represent the amount
of surface runoff available for transporting sedi-
ment, the length of the transport path, the gradient
of the path,  the shape and changes in surface area
of the path, a measure of surface microrelief, and a
measure of ground cover. All of these factors should
have  measurable  parameters and be combined
together with the proper coefficients. To date, there
is no accurate way to estimate the amount of sur-
face runoff that might be  available for sediment
delivery  in  the forest  environment, the  actual
shape and location  of sediment delivery  paths,
degree of surface roughness,  or characteristics  of
slope shape. An understanding of how to combine
these factors or what coefficients  to use  is not
known for most situations.
        PROCEDURAL CONCEPTS:
   ESTIMATING SEDIMENT DELIVERY


  This section discusses the concepts necessary for
estimating sediment delivery and for evaluating
the individual parameters involved. It is organized
according to  a conceptual perception  of sediment
delivery and corresponds with the flow  chart of
figure IV.l. An outline of the overall procedure for
estimating sediment delivery to a stream from sur-
face  erosion sources is  presented in "The
Procedure" section of this chapter. A  detailed ex-
ample for using  the  procedure  is  provided  in
"Chapter  VIII:  Procedural  Examples."  All  con-
cepts discussed  here are necessary for using the
overall procedure.
         The Sediment Delivery Index


  An index approach is recommended to help
bridge the gap between the need to estimate how
much sediment reaches a stream channel and the
lack of a working sediment delivery  model to
provide such estimates. This approach provides a
relative evaluation of seven generally accepted en-
vironmental factors and one site specific factor that
are considered important in the sediment delivery
process. These eight factors are not necessarily the
only ones that may be needed in all situations. This
indexing procedure has not  been validated  by
research. Therefore, the computed  quantities may
be different from measured quantities of sediment
delivered to a stream channel. Use of the index is
only an aid in evaluating the relative effects of dif-
ferent management practices on sediment delivery
from a given forest area.
Evaluation Factors

  For this  discussion, each of the following eight
factors  is   considered  as  though it acts  in-
dependently of any other factor.  In reality, these
factors interact with each other in complex ways.
  1.  Transport agent (e.g., water availability).
     — Surface runoff from rainfall and snowmelt
     is an  important factor in the movement of
     eroded material. It is estimated that overland
     flow rates from sheet and rill erosion rarely ex-
     ceed 1 cfs on agricultural land and generally
     are less than 0.1 cfs on  forest lands in  the
     United States.
  2.  Texture of  eroded material. — Assuming
     that aggregates do not form, individual parti-
     cles of fine-textured soil material require less
     energy for delivery than  particles of coarse-
     textured material. Sediment delivery efficien-
     cies are higher on an area dominated  by fine-
     textured material than on an area dominated
     by coarse-textured materials if the other fac-
     tors influencing sediment delivery are equal.
  3.  Ground cover. — Ground cover (forest floor
     litter,  vegetation, and  rocks)  creates a tor-
     tuous  pathway for eroded particles to travel
     which allows time for the eroded material to
     settle  from surface runoff water (Tollner and
     others  1976). Protective  ground  cover may
     also prevent raindrop  impact energy from
     creating  increased  flow  turbulance which
     would  increase the  carrying capacity of  the
     runoff flow.
  4.  Slope shape. — Concave slopes between  the
     source area and the stream channel promote
     deposition of the larger size fraction of  the
     transported  material  (Neibling  and Foster
     1977).  Convex slopes create more favorable
     conditions for increasing the material carrying
     capacity  of  the transporting agent.  Slope
     shape is a difficult factor to quantify, but it
     seems to play  an important  role in sediment
     delivery.
  5.  Slope gradient. — Slope gradient, along with
     the volume  of water available for sediment
     delivery,  provides  the necessary energy to
     deliver the eroded material. The efficiency of
                                              IV.54

-------
     the sediment delivery process increases with
     increasing slope gradient.
  6.  Delivery distance. — Increasing the distance
     from a sediment source to a stream channel or
     diversion ditch increases the effect that other
     factors have on the amount of sediment ac-
     tually delivered. On the other hand, if a sedi-
     ment source is very close to a stream channel,
     the other factors affecting sediment delivery
     have proportionally less opportunity to reduce
     the amount of sediment delivered.
  7.  Surface roughness. — Roughness of the soil
     surface affects sediment delivery similarly to
     that of ground cover. Rougher surfaces create
     more tortuous pathways for eroded particles
     to  pass over and more surface area for water
     infiltration than smooth surfaces for a given
     area (Meeuwig 1970).
  8. Site specific factors.  — In many parts of the
     United  States, unique  forest  environments
     and/or soil factors influence the sediment
     delivery  efficiency. For  example, soil  non-
     wettability  (DeBano  and  Rice  1975),
     mineralogy such  as the Idaho batholith
     described by Megahan (1974),  biological ac-
     tivity, or  fire can change  the sediment
     delivery  efficiency of  some  forest  lands.
     Within forested areas of the southeast United
     States, microrelief adjacent to stream chan-
     nels may cause concentrated water flows, thus
     having a large effect on sediment delivery ef-
     ficiency.  Some soils have a greater tendency
     than others to form stable aggregates, hence
     reducing the sediment delivery efficiency.
Determining The Sediment Delivery Index

  The stiff diagram shown in figure IV.22 uses vec-
tors to display the magnitude and scale of each ma-
jor factor identified as  influencing  sediment
delivery. The area of the  polygon created by con-
necting the  observed, anticipated,  or  measured
value for each factor is determined and related to
the total possible area (the polygon formed by con-
necting the  outer limits  of each vector) of the
graph. The percentage of area inside the polygon is
coupled to the delivery index through the use of
skewed probit transformations (Bliss 1935). Small
polygonal areas surrounding the midpoint indicate
a low probability of efficient sediment delivery, or,
in other words, a very low  sediment delivery index.
Sediment delivery  indexes will  be  low  in most
forest ecosystems managed by the best forest prac-
tices. Polygons approaching the outer limits of the
stiff diagram indicate a high probability of efficient
sediment  delivery. The fraction of the  total stiff
diagram area formed by a given polygon is adjusted
using figure IV.23, to give the sediment delivery in-
dex.
  The scale and magnitude of the vectors in figure
IV.22 have been defined as follows:
  1. The magnitude of the transport agent is deter-
     mined by the equation:
                   F = CRL            (IV. 12)
   where:
    F = water availability,
                    ft- 2 !•>
    C = 2.31  x 10"5 • •   * (a conversion constant)
                    lil OCC
    R = maximum anticipated precipitation and/
         or snowmelt  rate minus infiltration  in
         units of in/hr from local records, and
    L = slope length in feet of the sediment source
         area  (perpendicular to contours).
   Values of F for given values of R and L are  in
   table IV.8.
   The maximum scale value in figure IV.22 is 0.1
   cfs. If the flow is calculated to exceed 0.1 cfs,
   use the scale factor of 0.1 for water availability.
   This model assumes that the precipitation in-
   put exceeds the site infiltration capacity caus-
   ing overland flow  conditions at the lower boun-
   dary of the eroded material source area. If no
   water is available then the sediment delivery in-
   dex is zero (0.0).
  2.  Texture of eroded material  is  expressed  as
     percent of eroded  material that is finer than
     0.05 mm  (silt size). A particle diameter less
     than 0.05 mm was shown to be  highly trans-
     portable  for sediment movement  (Neibling
     and Foster 1977). A  scale factor of zero in-
     dicates that the eroded material contains no
     material less than 0.05 mm diameter, and a
     factor of 100 percent indicates that all of the
     eroded material  is   0.05  mm or less  in
     diameter.
  3. Ground cover that is in actual  contact  with
     the soil surface, is expressed in percent cover
     between 0 (bare soil surface) and 100 (mineral
     soil surface completely covered). This factor is
     scaled based on unpublished  data by Diss-
     meyer2 which  relates relative  ground cover
   'Personal communication of unpublished material from G.
Dissmeyer, USDA  Forest Service,  State and Private Forestry,
Atlanta, Ga.
                                               IV.55

-------
Percent Ground
Cover
Slope (
Shape
(
\


\











)














),„


V
^^

\










1











2
10 >
>^
fl
(

k-






\

10
\




















\5
\






2




200,,
100 */

4
30
^

^







^







Texture of Available
Eroded Material Water
|






20
s


^
4







500 v*
*Ł•









Delivery Distance
feet















30



3
400
3000J
2000X
x
^































3— 	
N,"

P
/



























•75




-50




•25


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SsJ

-3


_ n



• 1


n

- -





















/
f



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25












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).02





Sc25










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^








N
















I

/









/
/

/^o.oso




50





\












.5C
s














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).07








75







\









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5



/













-
1C
-










N










in
Surface Slope
Roughness Gradien
0.10
0 Site
Specific
0
t
                     Figure IV.22—Stiff diagram for estimating sediment delivery.
density influence to overland water flow.
Slope shape is scaled in magnitude between 0
and 4, with 4 being a slope that is convex from
the boundary of the source area to the stream
channel. A scale factor of 0  describes a slope
concave from the boundary of the source area
to the stream  channel,  while  a  factor  of 2
shows  that  one-half of the  slope is concave
and the other half is convex  or that the entire
slope is uniformly straight.  A factor of 3 in-
dicates that a larger percentage of the slope is
convex in shape.
5.  The slope gradient is  the vertical elevation
   difference between the lower boundary of the
   source  area and the stream channel divided
   by the  horizontal distance and expressed as a
   percent between 0 and 100.
6.  The distance factor is the login of the distance
   in feet from the boundary of the source area to
   a stream channel or ditch. Distances greater
   than 10,000 feet (3,050 m) are considered in-
   finite. The distance vector is marked using a
   login scale so  that distances  are entered
   directly onto the vector in figure IV.22.
                                          IV.56

-------
   1.0
  0.9
  OB
  07
X
LLJ
Q
UJ
7
   05
til

O
  0.4
   0.3
   02
   0.1
              10       20        30        40        50       60       70
                                   PERCENT AREA FROM STIFF DIAGRAM

                         Figure IV.23.—Relationship between polygon area on stiff
                                  diagram and sediment delivery index.
                                                                              80
                                    90
                                             100
7. The roughness factor is scaled in magnitude
   between 0 and 4 with 0 being an extremely
   smooth forest floor surface condition and 4 be-
   ing a very rough surface. This is a subjective
   evaluation of soil surface conditions.
8. The  site specific factor influencing delivery
   ratios is scaled between 0 and 100 and must be
   assigned  its effective magnitude  by a user
   familiar with the unique condition of the site.
  Appropriate factor values  are  plotted on each
vector of the graphic sediment delivery model (fig.
IV.24). Lines  are  drawn  to  connect  all plotted
points to form an enclosed, irregular polygon. If a
site specific factor is not used, draw a line directly
between plotted points on the slope gradient and
available water vectors. Determine the area inside
the polygon by: measuring with a planimeter, es-
timating with a dot grid, or calculating and sum-
ming the areas of the individual triangles. Deter-
mine the percent of the total graph area that is
                                              IV.57

-------
         Percent Ground
             Cover
  Texture of
Eroded Material
Available
 Water
Slope
Shape
                                                                                          0.10
                                                   Site
                                                 Specific
        Delivery Distance
               feet
   Surface
  Roughness
                                                                                        100
   Slope
  Gradient
                           Figure IV.24.—Example of graphic sediment delivery model
                                             lor road R3.1.
within the polygon. Using the S-shaped probit     delivery index by  using the percent area of the
curve in  figure IV.23, determine  the sediment     polygon from figure IV.24.
                                              IV.58

-------
                    Table IV.8.—Water availability values for given source area slope length (ft) and runoff (in/hr)1
3
bi
Surface
slope
length

10
20
30
40
50
75
100
150
200
250
300
350
400
450
500
1000

.025
.00006
.00012
.00017
.00023
.00029
.00043
.00058
.00087
.0012
.0014
.0017
.0020
.0023
.0026
.0029
.0058

.05
.00012
.00023
.00035
.00046
.00058
.00087
.0012
.0017
.0023
.0029
.0035
.0040
.0046
.0052
.0058
.012

0.75
.00017
.00035
.00052
.00069
.00087
.0013
.0017
.0026
.0035
.0043
.0052
.0061
.0069
.0078
.0087
.017

1.0
.00023
.00046
.00069
.00092
.0012
.0017
.0023
.0035
.0046
.0058
.0069
.0081
.0092
.010
.012
.023
Runoff
1.25
.00029
.00058
.00087
.0012
.0014
.0022
.0029
.0043
.0058
.0072
.0087
.010
.012
.013
.014
.029

1.5
.00035
.00069
.0010
.0014
.0017
.0026
.0035
.0052
.0069
.0087
.010
.012
.014
.016
.017
.035

1.75
.00040
.00081
.0012
.0016
.0020
.0030
.0040
.0061
.0081
.010
.012
.014
.016
.018
.020
.040

2.0
.00046
.00092
.0014
.0018
.0023
.0035
.0046
.0069
.0092
.012
.014
.016
.018
.021
.023
.046

2.25
.00052
.0010
.0016
.0021
.0026
.0039
.0052
.0078
.010
.013
.016
.018
.021
.023
.026
.052

2.5
.00058
.0012
.0017
.0023
.0029
.0043
.0058
.0087
.012
.014
.017
.020
.023
.026
.029
.058

2.75
.00064
.0013
.0019
.0025
.0032
.0048
.0064
.0095
.013
.016
.019
.022
.025
.029
.032
.064

3.0
.00069
.0014
.0021
.0028
.0035
.0052
.0069
.010
.014
.017
.021
.024
.028
.031
.035
.069

3.25
.00075
.0015
.0023
.0030
.0038
.0056
.0075
.011
.015
.019
.023
.026
.030
.034
.038
.075

3.5
.00081
.0016
.0024
.0032
.0040
.0061
.0081
.012
.016
.020
.024
.028
.032
.036
.040
.081

3.75
.00087
.0017
.0026
.0035
.0043
.0065
.0087
.013
.017
.022
.026
.030
.035
.039
.043
.087

4.0
.00092
.0018
.0028
.0037
.0046
.0069
.0092
.014
.018
.023
.028
.032
.037
.042
.046
.092
          1The table values were obtained by the formula:
                                                           := (2 31x10-*  "2hr \(Rnnnff  in/hr \ (slope length ft.)

                                                              V           in sec./V             /

-------
  Estimating Sediment Delivery By Activity


  Each land-disturbing activity should have an es-
timate of soil loss for the location where it occurs
and a delivery index based on site characteristics.
An  estimate of the amount  of sediment which
might reach a stream channel can be obtained by
multiplying the surface soil loss (tons/year) by the
sediment delivery index for each erosion response
unit.
  All of  the procedures  used to arrive at an es-
timate of surface soil loss and sediment delivered to
a stream channel only provide a way to evaluate
alternative  management practices. Only  on-the-
ground monitoring can verify if the objectives have
been met by the management strategy.
                                CONSIDERATIONS FOR REDUCING
                                SEDIMENT DELIVERY
                                  Theoretically it is possible to reduce sediment
                                delivered to a stream channel  by  making  ap-
                                propriate changes in any of the index factors. In ac-
                                tual practice,  some factors  are easier to change
                                than others. The following tabulation describes the
                                basic concepts underlying  each factor  and  the
                                changes  brought about by  controls for sediment
                                delivery. This conceptual presentation is to aid un-
                                derstanding  of controls and determining which
                                control practice to use. Details of specific control
                                practices may be found in "Chapter II: Control Op-
                                portunities."
  Sediment delivery
       factors
Water
   availability
                   Preventive
                               Mitigative
Control over the rainfall rate is not likely to occur because it is a function of overall
weather patterns.
                    Use management practices  that  maintain high in-
                    filtration rates. Avoid such things as soil compaction
                    which  changes  soil  structure  and  permeability.
                    Control of soil moisture content by high consumptive
                    use promotes infiltration.
                                                      Increase infiltration rates
                                                      by breaking surface crusts,
                                                      and incorporating organic
                                                      matter or  other  soil
                                                      amendments  to improve
                                                      aggregation of soil  parti-
                                                      cles.  Promote  vegetative
                                                      growth  for high consump-
                                                      tive  water  use and
                                                      desirable  soil  structure
                                                      development.
                    Where snowmelt is influential, use management prac-
                    tices which will not create significant increases in the
                    amount of solar energy reaching the snow pack.
                                                      Reduce  snowmelt  runoff
                                                      rates by increasing the in-
                                                      terception of solar energy
                                                      above the snow surface.
Texture of
  eroded material
Soil  texture  is  controlled by
mineralogy and weathering.

Maintain natural, stable soil aggregates which will act
as a coarse-textured material in response to sediment
delivery forces.
soil-forming factors  that are generally  related  to
                                                                         Use  soil   amendments
                                                                         which promote floculation
                                                                         and  development  of  ag-
                                                                         gregates.
                                              IV.60

-------
Sediment delivery
      factors
                   Preventive
       Mitigative
Ground cover       Control  and design forest management activities to
                    minimize forest floor disturbance.
                                                      Add  mulch,  establish
                                                      vegetation,  distribute
                                                      residues, or use other prac-
                                                      tices  to create long tor-
                                                      tuous pathways for water
                                                      flow   and   sediment
                                                      delivery.
Slope shape         Control location and design of various types of con-
                    struction  and  other  activities  that would  create
                    adverse slope shapes.
                                                      Design concave slope seg-
                                                      ments for  sediment
                                                      delivery control on  con-
                                                      struction  sites or with
                                                      other activities.
Slope gradient
Control location and design of various types of con-
struction activities to minimize the ci eation of steep
slopes.
Reduce  slope  gradients
created  by  construction
and  other  activities
wherever possible.
Delivery distance
Locate activities well away from stream channels to
maintain long delivery paths.
Relocate activity sites  to
increase  overall  delivery
distance to a stream chan-
nel.
Surface roughness
Design  activities  to  maintain  natural  surface
roughness. Avoid creating channels that  shortcut
natural tortuous pathways.
Create ridges and depres-
sions on the surface to trap
sediment  and  increase
water infiltration.
Site specific
  factors
This will depend upon the characteristics of the chosen site factor.
                                              IV.61

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              APPLICATIONS, LIMITATIONS AND PRECAUTIONS:
                                 SEDIMENT DELIVERY
  Very few attempts have been made to verify the
reliability of sediment delivery models due to the
difficulty of obtaining sufficient data for testing.
The following limitations attributed to this model
are not based on actual data but are deduced as be-
ing important.  Future research  may  add to or
change ideas about these limitations.
  1.  Only sheet flow surface  runoff is addressed
     with the sediment delivery  index. If chan-
     neled flow develops, other approaches must
     be used to describe sediment delivery.
  2.  The choice of factors used to describe sedi-
     ment delivery is thought to apply in all cases;
     however, these may vary with future research.
  3.  The scaling of each factor on the stiff diagram
     is based on the best  available information;
     however,  new  research information will
     probably show a need for some changes.
  4.  Many factors work together in various ways to
     influence  sediment delivery.  These interac-
     tions have not been studied extensively and
     may not be expressed correctly by the model.
5. The model assumes that the only water used
   to move the sediment is generated on the sedi-
   ment delivery path. It does not consider the
   potential  for additional  water from  other
   sources on the slope. Solution of this problem
   depends on the development of a satisfactory
   water routing model.

6. Individual sediment  delivery routes  have
   various shapes  and  overall  surface  areas
   which are not accounted for by the model.

7. Infiltration rates  may be different  on dis-
   turbed  areas than in sediment  filter strips.
   Only the infiltration rate for the disturbed site
   is used.

8. Antecedent soil  moisture  conditions are not
   incorporated  into the  model. If sediment
   delivery is most likely to occur during certain
   time  periods  with particular soil moisture
   characteristics, then some adjustments could
   be made in the infiltration rate.
                                            IV.62

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                                    THE PROCEDURE
   ESTIMATING SEDIMENT DELIVERY
   FROM SURFACE EROSION SOURCES
  The following steps outline the overall procedure
for estimating sediment delivery to a stream from
surface erosion sources. Steps 1 through 11 repre-
sent the procedure for estimating surface soil loss,
and steps 12 through 15 represent the procedure for
estimating sediment delivery. A complete example
for using the procedure is provided in "Chapter
VIII: Procedural Examples." Most of the steps are
self explanatory;  however, the specific concepts,
parameters and  computations involved in the
procedure were discussed earlier in this chapter un-
der "Procedural Concepts: Estimating Soil Surface
Loss" and "Procedural Concepts: Estimating Sedi-
ment Delivery."
  Step 1.   — Identify the  watershed  of interest
             and obtain the necessary materials
             and information.
  Step 2.   — Delineate the drainage  network in
             as  much detail  as the topographic
             base will allow.
  Step 3.   — Delineate the hydrographic divides
             relative  to  the drainage network
             identified in Step  2 above.
  Step 4.  — Delineate  soil and vegetative
             ground cover units  based on ap-
             propriate data.
  Step 5.   — Show  the proposed land  use ac-
             tivity in detail, delineating cutting
             units,  roads,  landings   and skid
             trails,  etc.
Step 6.  — Using overlays,  incorporate all
            map-related  information  onto a
            single map base.

Step 7.  — Show the direction of water flow for
            each hydrographic source area.

Step 8.  — Set up worksheets for estimating
            potential sediment  load (wkshts.
            IV.l—IV.8).

Step 9.  — List  each source  area that  is
            delineated, and number by erosion
            response unit.

Step 10. —Working   in  individual  hydro-
            graphic areas, determine for each
            erosion response unit the values for
            the variables R, K, LS, and VM.

Step 11. — Using the  values from step  10,
            calculate the estimated surface soil
            loss (tons/year).

Step 12. — Working by erosion response units,
            determine for each treatment
            source the sediment delivery index
            (SDj).

Step 13. — Calculate  the  estimated tons  per
            year of sediment input  to  the
            stream system by  each  erosion
            response unit.
Step 14. — Arrange erosion response unit sedi-
            ment values in matrix by treatment
            type.
Step 15. — Evaluate  results.
                                             IV .63

-------
                                   LITERATURE CITED
Adams, G. E., D. Kirkham, and W. H. Scholtes.
  1958. Soil erodibility and other physical proper-
  ties of some Iowa soils. J. Sci., Iowa State Coll.
  32:485-540.

Barnett, A. P., and J. S. Rogers. 1966. Soil physical
  properties related to runoff and erosion from ar-
  tificial rainfall.  Trans.  Am. Soc. Agric. Eng.
  9:123-125.

Bekey, G. A. 1977. Models and reality: Some reflec-
  tions on  the  art and  science  of  simulation.
  Simulation 29(5):161-164.

Bennett, H. H.  1934. Dynamic action of rains in
  relation to erosion in the humid region. Trans.
  Am. Geophys. Union, Fifteenth meeting, p. 474-
  488.

Bennett, J. P.  1974. Concepts of  mathematical
  modeling of sediment yield.  Water Resour. Res.
  10(3):485-492.

Bliss, C. 1.1935.  The calculation of the dosage mor-
  tality curve. Ann. Appl. Biol. 22(1):134-167.

Browning,  G.  M.,  C.  L. Parish, and J.  A. Glass.
  1947. A  method  for determining the use and
  limitation of rotation and conservation practices
  in control of soil erosion in Iowa. J.  Am.  Soc.
  Agron. 39:65-73.

Chapman,  Gordon. 1948. Size of raindrops and
  their striking  force at the soil surface in  a red
  pine  plantation.  Trans.  Am.  Geophys.  Union
  29:664-670.

Clyde, Calvin F., C.  Earl Israelsen, and Paul E.
  Packer.  1976.  Erosion  control during highway
  construction, Vol. II. Manual of erosion control
  principles and practices. Utah Water Res. Lab.,
  Utah State Univ., Logan.

Cruse, R. M., and W. E. Larson. 1977. Effect of soil
  shear  strength  on soil  detachment  due to
  raindrop  impact.  Soil  Sci. Soc.  of Am. J.
  41(4) :777-781.

DeBano, L. F., and R.  M. Rice.  1975.  Water-
  repellant soils: Their implications in forestry. J.
  For. 71(4):222-223.

Dohrenwend, R. E. 1977. Raindrop  erosion in the
  forest. Res.  Note No. 4, Mich. Technol. Univ.,
  Ford For. Cent., Lanse, Mich. 49946.  19 p.
Ellison, W. D. 1947. Soil erosion studies — part I.
  Agric. Eng. 28(4): 145-146.

Foster,  G.  R.,  and  W.  H.  Wischmeier.  1973.
  Evaluating irregular slopes for soil loss predic-
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  Eng., St. Joseph, Mich.

Foster, G. R., L. D. Meyer, and C. A. Onstad. 1977.
  A  runoff  erosivity  factor  and  variable  slope
  length exponent for soil loss estimates. Trans.
  Am. Soc. Agric. Eng. 20(4):683-687.

Foster, G. R., and L. D. Meyer. 1977. Soil erosion
  and sedimentation by water — an overiew. In:
  Proc.  Natl. Symp. on Soil Erosion and Sedimen-
  tation by  Water. ASAE, publ. 4-77,  Am.  Soc.
  Agric. Eng., St. Joseph, Mich. p. 1-13.

Fredrikson,  R. L.  1972.  Nutrient  budget of  a
  Douglas-fir forest on an experimental watershed
  in  western Oregon.  In: Proc. res. on coniferous
  for. ecosyst,  p.  115-131. J.  F.  Franklin, L. P.
  Dempster,  and  R.  H.  Waring, eds. US/ffiP,
  USDA,  For.  Serv.,  Pac. Northwest  For.  and
  Range Exp.  Stn., Portland, Ore.

Gottschalk, L.  C., and G.  M. Brune. 1950.  Sedi-
  ment design criteria for the Missouri Basin loess
  hills.  USDA Soil Conserv. Serv. Tech. Pap. No.
  97.

Gunn,  R., and  G. D.  Kinzer.  1949. The terminal
  velocity of fall  for water droplets.  J.  Meteorol.
  6:243-248.

Horton, R.  E. 1975.  Erosional  development of
  streams and their drainage basins, hydrophysical
  approach to quantitative morphology. Geol. Soc.
  Am. Bull. 56:275-370.

Laws, J. 0.  1941. Measurement of fall-velocity of
  water drops  and  rain drops. Trans.,  Am.
  Geophys. Union 22:709-721.

Laws, J. 0., and  D. A. Parsons. 1943. Relation of
  raindrop size to intensity. Trans., Am. Geophys.
  Union 24:452-460.

Lillard, J. H., H. T. Rogers, and J. Elson. 1941. Ef-
  fects of slope, character of soil, rainfall, and crop-
  ping treatments on erosion losses from dunmore
  silt loam. Va. Agric. Exp. Stn. Tech. Bull. 72. 32
  P-
                                              IV.64

-------
Maner, S.B. 1958. Factors  affecting sediment
  delivery rates in the Red Hills  physiographic
  area. Trans. Am. Geophys. Union 39:669-675.

Maner,  S.B. and  L.H. Barnes. 1953. Suggested
  criteria for estimating gross  sheet erosion and
  sediment  delivery rates for the Blackland Prai-
  ries problem area in soil conservation. U.S. Dep.
  Agric.,    Soil Conserv.  Serv.,   Western Gulf
  Region, Fort Worth, Texas. Mimeograph.
Meeuwig, R. D. 1970. Infiltration and soil erosion
  as influenced by vegetation and soil in northern
  Utah. J. Range Manage. 23(3): 185-188.

Megahan,  W. F.  1974.  Erosion  over time on
  severely disturbed granitic  soil: A model. USDA
  For. Serv. Res. Pap. INT-156. 14 p. Intermt. For.
  and Range Exp. Stn., Ogden, Utah.

Megahan, W. F. 1978. Erosion processes on steep
  granitic roadfills in Central Idaho. Soil Sci. Soc.
  Am. J. 42(2):350-357.

Meyer,  L. D., G. R. Foster, and M. J. M. Romkens.
  1975. Origin of eroded soil from upland slopes.
  In: Present and Prospective Tech. for Predict.
  Sediment Yields and  Sour.  U.S. Dep.  Agric.,
  Agric. Res. Serv. Rep. ARS-S-40:177-189.

Meyer,  L. D., D. G. DeCoursey,  and M. J. M.
  Romkens. 1976. Soil erosion  concepts and  mis-
  conceptions. Proc.  Third Fed.  Inter-agency
  Sedimentation Conf.

Middleton,  H. E., C.  S. Slater, and H. G. Byers.
  1932. Physical and chemical characteristics of
  the soils from the erosion  experiment stations.
  U.S.  Dep. Agric. Tech. Bull. 316.  51 p.

Musgrave, G. W.  1947. The  quantitative  evalua-
  tion of factors in water erosion, a first  approx-
  imation. J. Soil and Water Conserv. 2:133-138.

Neibling,  W. H.,  and  G. R.  Foster. 1977.
  Estimating deposition and sediment yield from
  overland flow processes. Proc. of Int. Symp. on
  Urban Hydrol., Hydraul., and Sediment Contr.,
  Univ. Kentucky, Lexington, Ky. p. 75-86.

Olson, T. C.,  and W. H. Wischmeier.  1963. Soil-
  erodibility evaluations for soils on the runoff and
  erosion stations. Soil Sci. Soc. Am. Proc. 27:590-
  592.

Osborn, J. F., R. E. Pelishek, and J.  S. Krammes.
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 Peele, T. C., E. E. Latham, and 0. W. Beale. 1945.
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   soil types to erodibility. S.  C. Agric.  Exp. Stn.
   Bull. 357.

 Renfro, G. W.  1975. Use of erosion equations and
   sediment delivery ratios for predicting sediment
   yield. In: Proc. Sedimentation Yield Workshop,
   Oxord, Miss. U.S. Dep. Agric., Agric. Res. Serv.
   Rep. ARS-S-40.-33-45.

 Roehl, J. W. 1962. Sediment source areas, delivery
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 Roth, C. B., D. W. Nelson, and M. J. M.  Romkens.
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   chemical,  mineralogical  and  physical
   parameters. U.S. Environ. Protect. Agency Rep.
   EPA-660/2-74-043. USGPO, Washington  D.C
   111 p.
 Simons,  D. B., R. M. Li, and M. A. Stevens 1975.
   Development of models for predicting water and
   sediment routing and yield from storms on small
   watersheds. Colo. State Univ. Rep. CER 74-75-
   DBS-RML-MAS24.
Smith, D. D., and W. H. Wischmeier. 1957. Factors
  affecting sheet and  rill erosion.  Trans.  Am.
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Smith, D. D., and W. H. Wischmeier. 1962. Rain-
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Swank, W. T., N. B. Goebel, and J. D. Helvey.
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Tollner, E. W.,  B. J. Barfield,  C. T. Haan, and T.
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Trimble,  G. R., Jr.,  and S. Weitzman. 1954. Effect
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U.S. Army Engineer School. 1973. Open channel
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U.S. Department of Agriculture, Soil Conservation
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  17 p.
                                             IV.65

-------
U.S. Department of Agriculture, Soil Survey Staff.
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Williams, J.  R, H.  D. Berndt. 1972. Sediment
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Williams, J. R., and W. V. LaSeur.  1976. Water
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Wischmeier, W. H. 1972. Upslope erosion analysis.
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Wischmeier, W. H. 1975. Estimating the soil loss
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  disturbed  areas, p.  118-124. In: Present and
  prospective technology for predicting sediment
  yields  and  sources.  Proc.  Sediment-Yield
  Workshop, U.S. Dep. Agric. Sediment Lab., Ox-
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Wischmeier, W.H. 1976. Use  and  misuse  of the
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Wischmeier, W. H., and D. D. Smith. 1958. Rain-
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Wischmeier,  W. H.,  and D. D.  Smith. 1965.
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Wischmeier, W. H. and D. D. Smith. 1968. A un-
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Wischmeier, W. H.,  and J. V. Mannering. 1969.
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Wischmeier, W. H.,  C. B. Johnson,  and B.  V.
  Cross.  1971.  A soil  erodibility nomograph for
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Wischmeier, W. H., and D. D. Smith. Predicting
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Zingg, A. W. 1940. Degree and length of land slope
  as it affects soil loss in runoff. Agric. Eng. 21:59-
  64.
                                            IV.66

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                                     APPENDIX IV.A.:
                                       GULLY EROSION
  A gully is a channel created by concentrated but
intermittent flow of water, usually during and im-
mediately following heavy rains;  however,  con-
centration of snowmelt runoff may also be a factor.
Gullies  are deep enough  to interfere  with,  and
usually  are not  obliterated by, normal tillage or
silvicultural activities.
  Quantitative estimates of soil loss and sediment
produced by gully erosion must be based on profes-
sional judgment  about  the  overall  erosional
processes in a particular location. Changes in the
geometry of a gully can provide an estimate of the
amount  of  material  being  eroded.   Rates of
headward cutting, final  average width,  and depth
of each cycle of cutting can be used to compute the
volume  of soil material removed from the gully.
The mass of soil material is calculated by multiply-
ing the volume by an appropriate bulk density fac-
tor for the particular soil.
  Bulk density is usually expressed in grams per
cubic centimeter or pounds per cubic foot. Conver-
sion factors are:

            g/cm3 =  (0.016) (lb/ft3)
            lb/ft3 = (62.43) (g/cm3)

  An estimate of the proportion of eroded material
actually delivered to a stream  channel may  be
needed  if the gully does not connect directly to a
stream system.
                                              IV.67

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                                    APPENDIX IV.B.:
                                    EROSION OVER TIME
  To predict long-term, onsite soil losses, changes
in the various parameters in the soil loss equation
must be estimated and redefined for each year. The
most important is the VM factor. The K factor
needs to be changed if management causes long-
term  changes  in  soil characteristics to  occur.
Future changes in  VM and K factors become, at
best, an educated guess about what might happen
in any given year.  Time trend analysis should be
based on both  best condition and worst condition
parameters in order to show a range of possible out-
comes.
  The part of the equation which is most likely to
change with time is the VM factor. The effects of
roughness and vegetation change with time either
as the surface roughness is broken down or as the
vegetation becomes healthier  and covers more of
the surface. Estimates of VM changes must be
made relative to the time period of interest.
  Fine  materials in the surface soil tend to erode
away, leaving the heavier material, which is less
erosive to protect the surface (Clyde and others
1976, Megahan 1974, Wischmeier and Mannering
1969). Other long-term changes due to manage-
ment must also be evaluated.
                                             IV.68

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                                      APPENDIX IV.C.:
                                CONTROLLING DITCH EROSION
   The simulation procedures in Chapter IV, "Sur-
 face Erosion" do not consider  road ditch erosion.
 There is no technique to estimate the  amount of
 sediment  delivered to the  stream  from  road
 ditches. Because some controls are designed to af-
 fect road ditch erosion, the Manning formula (U.S.
 Army Engineering School 1973) is used to estimate
 the effect of various controls on  road ditch stability
 and water velocity. Manning's  formula  is:

           V  = (M9) (R0.66)  (S0.6)    (IV.C.l)
   where:
   V = velocity of flow in ft/sec,
   R = hydraulic radius,  =
                 cross-section  area of the channel
                      wetted  perimeter (ft)
        (from  tables IV.C.2  through IV.C.5)
  S = slope of the channel  in ft/ft, and

  n = friction  factor which  depends on  the
       material comprising the  channel  from
       Table IV.C.l
  Manning formula limitations:  (1) It will not
predict  amounts of sediment  delivered  to the
stream from a road ditch. (2) The formula is based
on the amount of energy necessary to move parti-
cles of given size, and does not account for detach-
ment. Soils with strong structure are likely to be
more resistant than soils  with weak structure. (3)
The maximum recommended velocity figures are
based on energy/particle size relationships.

An Example For Use Of The
Manning Formula
 Problem —   Determine  whether the  water
              velocity for a  given road ditch will
              be below critical levels for erosion.
              If velocities are too high, make and
              evaluate changes.
 Solution
     1.  Obtain hydraulic radius for channel. As-
        sume that the road ditch is a symmetrical,
        triangular channel  1.3 feet deep  with
       21/2:1  slopes.  Check  table  IV.C.2  for
        hydraulic radius which is 0.60 feet for
        this size channel.
     2. Obtain slope of channel. (Slope of the road
       ditch is  measured and  found to be 0.003
       feet per  feet.)
 3. Obtain roughness coefficient  from table
   IV.C.I.(The channel sides, in this case, are
   sand  and  have a  friction factor  (n)  of
   0.020.)
 4. Obtain maximum allowable velocity. (For
   a sandy channel, the maximum velocity is
   1-2 feet per second (table IV.C.l).)
 5. Obtain V (velocity) for the specified chan-
   nel by using the nomograph (fig. IV.C.l).
   (Velocity for the specified ditch is 2.9 feet
   per second.)

 6. Compare the  predicted  velocity  for the
   specified ditch with the maximum  recom-
   mended velocity for sandy channels.
     specified ditch
        2.9 ft/sec
maximum velocity
    1-2 ft/sec
   If the  specified  ditch  has too  great  a
   velocity, it will erode. Therefore,  controls
   must be chosen that will reduce the water
   velocity in the road ditch.

 7. Water velocities in ditches can be reduced
   by protecting the channel with vegetation,
   rock,  or by changing the channel shape.
   (With vegetative  protection,  the  friction
   factor (n)  becomes 0.030-0.050  and the
   maximum recommended velocity becomes
   3-4 feet per second.)

 8. Obtain  velocity  for specified  ditch with
   vegetative  protection  by referring to the
   nomograph (fig. IV.C.l).  Velocity is  1.9
   feet per second.

 9. Compare  the predicted  velocity  for the
   specified ditch with the maximum recom-
   mended velocity for vegetation protected
   channels (average turf) with easily eroded
   soil.
      specified ditch
         1.9 ft/sec
maximum velocity
     3-4 ft/sec
10.  If the specified ditch has a lower velocity
    than  the  recommended  maximum
    velocities, it should be stable as long as the
    vegetation remains intact.
                                               IV.69

-------
f.3 .2















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o
o
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-.0006
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EQUATION:

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:\^
..8
L.9
.1.0



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:
-6
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-7
-8
-9
-10
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^^ Z
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\ W
\ , Ł
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'^ LU
NZ
^
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EXAMPLE (SEE DASHED LINE) O
— I
GIVEN: R =0.6 LU
S = 0.003 >
n = 0.02
FIND: V
LINE FROM S VALUE TO n VALUE
INTERSECTS TURNING LINE, ESTAB -
LISHING TURNING POINT, LINE FROM
R VALUE THROUGH TURNING POINT
INTERSECTS VELOCITY SCALE AT
V = 2.9 FPS.







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*f
-8
c
-7
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''• .8
i .7
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                                                         r.01
                                                         -.02
                                                         -.03
                                                          .04
                                                          ^.05

                                                          :.oe

                                                          -.07
                                                          ..08
                                                          -.09
                                                          i.10
                                                          -.2
                                                          -.3
Figure IV.C.1 Nomograph for Manning formula.
                 IV.70

-------
Table IV.C.1—Values for Manning's n and maximum permissible velocity of flow In open channels
                        Ditch lining
Manning's n
,fps'
1. Natural ec
a. Without
(1) Roc
(a) S
i
(b) Ji
(2) Soil:
TJ
0>
C
s
O)
O
Finegrained
»rth
t vegetation
k
mooth and
jnlform 	
igged & Irregul
s
>,
1
««
Gravel anc
soi
Sand and sandy
soils
o
io
Ł -j
0 -1
0
•o
t
a
2. o
55 -0
_i
_i
Highly Organic

ar 	

Unified
GW
GP
GM
GC
SW
SP
SM
SC
CL
ML
OL
CH
MH
OH
PT



USDA
Gravel
Gravel
Loamy
u
Gravelly Loam
Gravelly Clay
Sand
Sand
d
Loamy
QgnH 	 	
U
Sandy Loam
Clay Loam
Sandy Clay Loam
Silty Clay
Silt Loam
Very Fine Sand
Silt
Mucky Loam
Clay
Silty Clay
Mucky Clay
Peat
0.035 -
0.040-
0.022
C.023 -
0.023 -
0.022 -
0.024 -
0.020 -
0.022 -
0.020 -
0.021 -
0.023 -
0.022
0.023 -
0.022 -
0.022
0.023 -
0.022 -
0.022
0.040
0.045
0.024
0.026
0.025
0.020
0.026
0.024
0.024
0.023
0.023
0.025
0.024
0.024
0.024
0.023
0.024
0.024
0.025
20
15-18
6-7
7-8
3-5
2-4
5-7
1-2
1-2
2-3
2-3
3-4
2-3
3-4
2-3
2-3
3-5
2-3
2-3
'Maximum recommended velocities
                                        IV.71

-------
                                Table IV.C.1—Continued
      Ditch  lining
Manning's n   Vmax fps1
  b. With vegetation
    (1)  Average turf
      (a) Erosion resistant
           soil 	   0.050   0.070        4 - 5
      (b) Easily eroded soil 	   0.030   0.050        3 - 4
    (2)  Dense turf
      (a) Erosion resistant
           soil 	   0.070   0.090        6-8
      (b) Easily eroded soil 	   0.040 -  0.050        5 - 6
    (3)  Clean bottom with
         bushes on sides	   0.050   0.080        4-5
    (4)  Channel with tree
         stumps
      (a) No sprouts  	   0.040   0.050        5 - 7
      (b) With sprouts	   0.060   0.080        6 - 8
    (5)  Dense weeds  	   0.080   0.120        5-6
    (6)  Dense brush	   0.100   0.140        4-5
    (7)  Dense willows	   0.150   0.200        8-9

2.  Paved                                                       (Construction)
  a. Concrete, w/all surfaces:                                     Good   Poor
    (1)  Trowel finish	   0.012   0.014         20
    (2)  Float finish	   0.013   0.015         20
    (3)  Formed, no finish	   0.014   0.016         20
  b. Concrete bottom, float
         finished, w/sides of:
    (1)  Dressed stone in mortar	   0.015 -  0.017      18-20
    (2)  Random stone in mortar 	   0.017 -  0.020      17 -19
    (3)  Dressed stone or smooth
         concrete rubble (riprap)	   0.020   0.025         15
    (4)  Rubble or random stone (riprap)	   0.025   0.030         15
  c. Gravel bottom, sides of:
    (1)  Formed concrete	   0.017 -  0.020         10
    (2)  Random stone in mortar 	   0.020 -  0.023      8-10
    (3)  Random stone or rubble (riprap)	   0.023   0.033      8-10
  d. Brick	   0.014   0.017         10
  e. Asphalt	   0.013   0.016      18-20
'Maximum recommended velocities
                                        IV.72

-------
Table IV.C.2. Hydraulic radius (R) and area (A) of symmetrical triangular channels.

               	WP
                                 -9-
                                              d     R  =  A/WP
                                              1

Depth,
d
(leet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
3.5
4.0
Slope ratio
1:
A
0.25
0.36
0.49
0.64
0.81
1.00
1.21
1.44
1.69
1.96
2.25
2.56
2.89
3.24
3.61
4.00
6.25
9.00
12.25
16.00
1
R
0.18
0.21
0.25
0.28
0.32
0.35
0.39
0.42
0.46
0.50
0.53
0.57
0.60
0.64
0.67
0.71
0.88
1.06
1.24
1.41
W.
A
0.38
0.54
0.74
0.96
1.21
1.50
1.82
2.16
2.54
2.94
3.38
3.84
4.34
4.86
5.42
6.00
9.38
13.50
18.38
24.00
;:1
R
0.21
0.25
0.29
0.33
0.37
0.42
0.46
0.50
0.54
0.58
0.62
0.67
0.71
0.75
0.79
0.83
1.04
1.25
1.45
1.66
2
A
0.50
0.72
0.98
1.28
1.62
2.00
2.42
2.88
3.38
3.92
4.50
5.12
5.78
6.48
7.22
8.00
12.50
18.00
24.50
32.00
:1 2
-------
Table IV.C.3.  Hydraulic radius (R) and area (A) of nonsymmetrical triangular channels.
               	WP


Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0


V

\

A
V^



X

'• 1
d
\

\
R
r

= A/WP




Slope ratio
1:1
A
0.50
0.72
0.98
1.28
1.62
2.00
2.42
2.88
3.38
3.92
4.50
5.12
5.78
6.48
7.22
8.00
8.82
9.68
10,58
11.52
12.50
13.52
14.58
15.68
16.82
18.00
-3:1
R
0.22
0.26
0.31
0.35
0.39
0.44
0.48
0.52
0.57
0.61
0.66
0.70
0.74
0.79
0.83
0.87
0.92
0.96
1.01
1.05
1.09
1.14
1.18
1.22
1.27
1.31
1V4:1
A
0.56
0.81
1.10
1.44
1.82
2.25
2.72
3.24
3.80
4.41
5.06
5.76
6.50
7.29
8.12
9.00
9.92
10.89
11.90
12.96
14.06
15.21
16.40
17.64
18.92
20.25
-3:1
R
0.23
0.27
0.32
0.36
0.41
0.45
0.50
0.54
0.59
0.63
0.68
0.73
0.77
0.82
0.86
0.91
0.95
1.00
1.04
1.09
1.13
1.18
1.22
1.27
1.31
1.36
2:1 -
A
0.63
0.90
1.23
1.60
2.03
2.50
3.03
3.60
4.23
4.90
5.63
6.40
7.23
8.10
9.03
10.00
11.03
12.10
13.23
14.40
15.63
16.90
18.23
19.60
21.03
22.50
3:1
R
0.23
0.28
0.32
0.37
0.42
0.46
0.51
0.56
0.60
0.65
0.69
0.74
0.79
0.83
0.88
0.93
0.97
1.02
.07
.11
.16
.20
.25
1.30
1.34
1.39
2'/*:1
A
0.69
0.99
1.35
1.76
2.23
2.75
3.33
3.96
4.65
5.39
6.19
7.04
7.95
8.91
9.93
11.00
12.13
13.31
14.55
15.84
17.19
18.59
20.05
21.56
23.13
24.75
-3:1
R
0.23
0.28
0.33
0.38
0.42
0.47
0.52
0.56
0.61
0.66
0.70
0.75
0.80
0.85
0.89
0.94
0.99
1.03
1.08
1.13
1.17
1.22
1.27
1.32
1.36
1.41
4:1-
A
0.88
1.26
1.72
2.24
2.84
3.50
4.24
5.04
5.92
6.86
7.88
8.96
10.12
11.34
12.64
14.00
15.44
16.94
18.52
21.16
21.87
23.66
25.52
27.44
29.44
31.50
3:1
R
0.24
0.29
0.34
0.38
0.43
0.48
0.53
0.58
0.63
0.67
0.72
0.77
0.82
0.86
0.91
0.96
1.00
1.06
1.10
1.15
1.20
1.25
1.30
1.35
1.39
1.44
5:1-
A
1.00
1.44
1.96
2.56
3.24
4.00
4.84
5.76
6.76
7.84
9.00
10.24
11.56
12.96
14.44
16.00
17.64
19.36
21.16
23.04
25.00
27.04
27.16
31.36
33.64
36.00
3:1
R
0.24
0.29
0.34
0.39
0.44
0.48
0.53
0.58
0.63
0.68
0.73
0.77
0.82
0.87
0.92
0.97
1.02
1.07
1.11
1.16
1.21
1.26
1.31
1.36
1.40
1.45
                                      IV.74

-------
Table IV.C.4. Hydraulic radius (R) and area (A) of symmetrical trapezoidal channels
                              [2' bottom width].

                  	WP



Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0



t
d



\
«-xd »U


A
- 2' —



-J


/
A =
WP =
R =
1
• xd2-*
2dV
•2d
1 + x2

+ 2




A/WP
Slope ratio
1:1
A
1.25
1.56
1.89
2.24
2.61
3.00
3.41
3.84
4.29
4.76
5.25
5.76
6.29
6.84
7.41
8.00
11.25
15.00

R
0.37
0.42
0.47
0.53
0.51
0.62
0.67
0.71
0.76
0.80
0.84
0.88
0.92
0.96
1.00
1.04
1.24
1.43
1'/2:1
A R
1.38 0.36
1.74 0.42
2.14 0.47
2.56 0.52
3.01 0.57
3.50 0.62
4.02 0.67
4.56 0.72
5.14 0.77
5.74 0.81
6.38 0.86
7.04 0.91
7.74 0.95
8.46 1.00
9.22 1.04
10.00 1.09
14.38 1.30
19.50 1.52
2:1
A
1.50
1.92
2.28
2.88
3.42
4.00
4.63
5.28
5.98
6.72
7.50
8.32
9.18
10.08
11.02
12.00
17.50
24.00

R
0.35
0.41
0.44
0.52
0.57
0.62
0.67
0.72
0.77
0.81
0.86
0.91
0.96
1.00
1.05
1.10
1.33
1.56
21/2
A
1.63
2.10
2.63
3.20
3.83
4.50
5.23
6.00
6.83
7.70
8.63
9.60
10.63
11.70
12.83
14.00
20.63
28.30
1
R
0.35
0.40
0.46
0.51
0.56
0.61
0.66
0.71
0.76
0.81
0.86
0.90
0.95
1.00
1.05
1.10
1.33
1.57
3:1
A
1.75
2.28
2.87
3.52
4.23
5.00
5.84
6.72
7.67
8.68
9.75
10.88
12.07
13.32
14.63
16.00
23.75
33.00

R
0.34
0.39
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.04
1.09
1.33
1.57
4:1
A
2.00
2.64
3.36
4.16
5.04
6.00
7.05
8.16
9.36
10.64
12.00
13.44
14.96
16.56
18.24
20.00
30.00
42.00

R
0.33
0.38
0.43
0.48
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.88
0.93
0.98
1.03
1.08
1.33
1.57


0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5:
A
2.25
3.00
3.85
4.80
5.85
7.00
8.25
9.60
11.05
12.60
14.25
16.00
17.85
19.80
21.85
24.00
36.25
51.00
1
R
0.32
0.37
0.42
0.47
0.52
0.51
0.62
0.67
0.72
0.77
0.82
0.87
0.92
0.97
1.02
1.07
1.32
1.56
6:1
A R
2.50 0.31
3.36 0.36
4.34 0.41
5.44 0.46
6.66 0.51
8.00 0.56
9.47 0.62
11.04 0.67
12.74 0.72
14.50 0.77
16.50 0.81
18.56 0.86
20.74 0.91
23.04 0.96
25.46 1.01
28.00 1.06
42.50 1.31
60.00 1.56
7:
A
2.75
3.72
4.83
6.08
7.47
9.00
10.68
12.48
14.43
16.52
18.75
21.12
23.63
26.28
29.07
32.00
48.75
69.00
1
R
0.30
0.35
0.41
0.46
0.51
0.56
0.61
0.66
0.71
0.76
0.81
0.86
0.91
0.96
1.01
1.06
1.30
1.55
8
A
3.00
4.08
5.32
6.72
8.28
10.00
11.89
13.92
16.12
18.48
21.00
23.68
26.52
29.52
32.68
36.00
55.00
78.00
:1
R
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.30
1.55
9:
A
3.25
4.44
5.81
7.36
9.09
11.00
13.10
15.36
17.81
20.44
23.25
26.24
29.41
32.76
36.29
40.00
61.25
87.00
1
R
0.29
0.34
0.39
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.30
1.54
10
A
3.50
4.80
6.30
8.00
9.90
12.00
14.31
16.80
19.50
22.40
25.50
28.80
32.30
36.00
39.90
44.00
67.50
96.00
1
R
0.29
0.34
0.39
0.44
0.49
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.89
0.94
0.99
1.04
1.29
1.54
                                   IV.75

-------
         Table IV.C.4.—Continued
	WP



Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0




1
A
2.25
2.76
3.29
3.84
4.41
5.00
5.61
6.24
6.89
7.56
8.25
8.96
9.69
10.44
11.21
12.00
16.25
21.00

t
d
4




1
R
0.41
0.48
0.55
0.61
0.67
0.73
0.79
0.84
0.90
0.95
1.00
1.05
1.10
1.15
1.20
1.24
1.47
1.68
"X
\
+-X



1 '/
A
2.38
2.94
3.54
4.16
4.82
5.50
6.22
6.96
7.74
8.54
9.38
10.24
11.14
12.06
13.02
14.00
19.38
25.50

\
d-J*



4:1
R
0.41
0.48
0.54
0.60
0.66
0.72
0.78
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.20
1.25
1.48
1.72

A
	 4'



2
A
2.50
3.12
3.78
4.48
5.22
6.00
6.82
7.68
8.58
9.52
10.50
11.52
12.58
13.68
14.82
16.00
22.50
30.00
V

jf x
— J *•
WP =
R =
Slope ratio
1 2V4:1
R A
/-
1
xd2
2d>
+ 4d
^ 1 + x

2 + 4




A/WP


R
0.40 2.63 0.39
0.47 3.30 0.46
0.53 4.03 0.52
0.59 4.80 0.53
0.65 5.63 0.64
0.71 6.50 0.69
0.76 7.43 0.75
0.82 8.40 0.80
0.87 9.43 0.86
0.93 10.50 0.91
0.98 11.63 0.96
1.03 12.80 1.01
1.08 14.03 1
1.14 15.30 1
1.19 16.63 1
1.24 18.00 1
1.48 25.63 1
1.72 34.50 1
.07
.12
.17
.22
.47
.71

3
A
2.75
3.48
4.27
5.12
6.03
7.00
8.03
9.12
10.27
11.48
12.75
14.08
15.47
16.92
18.43
20.00
28.75
39.00

1
R
0.39
0.45
0.50
0.57
0.62
0.68
0.73
0.79
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.20
1.45
1.70

4:
A
3.00
3.84
4.76
5.76
6.84
8.00
9.24
10.56
11.96
13.44
15.00
16.64
18.36
20.16
22.04
24.00
35.00
48.00

1
R
0.37
0.43
0.49
0.54
0.60
0.65
0.71
0.76
0.81
0.86
0.92
0.97
1.02
1.02
1.12
1.17
1.42
1.67


0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5
A
3.25
4.20
5.25
6.40
7.65
9.00
10.45
12.00
13.65
15.40
17.25
19.20
21.25
23.40
25.65
28.00
41.25
57.00
1
R
0.36
0.42
0.47
0.53
0.58
0.64
0.69
0.74
0.79
0.84
0.89
0.94
1.00
1.05
1.10
1.15
1.40
1.65
6
A
3.50
4.56
5.74
7.04
8.46
10.00
11.66
13.44
15.34
17.36
19.50
21.76
24.14
26.64
29.26
32.00
47.50
66.00
1
R
0.35
0.40
0.46
0.51
0.56
0.62
0.67
0.72
0.77
0.83
0.88
0.93
0.98
1.03
1.08
1.14
1.38
1.64
7
A
3.75
4.92
6.23
7.68
9.27
11.00
12.87
14.88
17.03
19.32
21.75
24.32
27.03
29.88
32.87
36.00
53.75
75.00
1 8:1
R A

R
0.34 4.00 0.33
0.39 5.28 0.38
0.45 6.72 0.44
0.50 8.32 0.49
0.55 10.08 0.55
0.61 12.00 0.60
0.66 14.08 0.65
0.71 16.32 0.70
0.76 18.72 0.75
0.81 21 .28 0.80
0.86 24.00 0.85
0.91 26.88 0.90
0.96 29.92 0.95
1.01 33.12 1.00
1.06 36.48 1.05
1.12 40.00 1
1.37 60.00 1
1.63 84.00 1
.10
.35
.62
9
A
4.25
5.64
7.21
8.96
10.89
13.00
15.29
17.76
20.41
23.24
26.25
29.44
32.81
36.36
40.09
44.00
66.25
93.00
1
R
0.32
0.38
0.43
0.49
0.54
0.59
0.64
0.69
0.74
0.79
0.84
0.89
0.94
0.99
1.04
1.09
1.34
1.62
10
A
4.50
6.00
7.70
9.60
11.70
14.00
16.50
19.20
22.10
25.20
28.50
32.00
35.70
39.60
43.70
48.00
72.50
102.00
•1
R
0.32
0.37
0.43
0.48
0.53
0.58
0.63
0.68
0.73
0.78
0.83
0.89
0.94
0.99
1.04
1.09
1.34
1.61
                IV.76

-------
           Table IV.C.4. —Continued
   	WP
t
d
4
      •xd
6'
  A = xd2 + 6d
WP = 2d Vl +x2 + 6
  R = A/WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
Slope ratio
1
A
3.25
3.96
4.69
5.44
6.21
7.00
7.81
8.64
9.49
10.36
11.25
12.16
13.09
14.04
15.01
16.00
21.25
27.00
1
R
0.44
0.51
0.59
0.66
0.73
0.79
0.86
0.92
0.98
1.04
1.10
1.16
1.22
1.27
1.32
1.37
1.61
1.86
1V4
A
3.38
4.14
4.94
5.76
6.62
7.50
8.42
9.36
10.34
11.34
12.38
13.44
14.54
15.66
16.82
18.00
24.38
31.50
1
R
0.43
0.51
0.58
0.65
0.72
0.78
0.85
0.91
0.97
1.03
1.08
1.14
1.20
1.25
1.30
1.36
1.61
1.87
2:
A
3.50
4.32
5.18
6.08
7.02
8.00
9.02
10.08
11.18
12.32
13.50
14.72
15.98
17.28
18.62
20.00
27.50
36.00
1
R
0.42
0.50
0.57
0.63
0.70
0.76
0.83
0.89
0.95
1.00
1.06
1.12
1.17
1.23
1.28
1.34
1.60
1.85
2V4
A
3.63
4.50
5.43
6.40
7.43
8.50
9.63
10.80
12.03
13.30
14.63
16.00
17.43
18.90
20.43
22.00
30.63
40.50
1
R
0.42
0.49
0.56
0.62
0.68
0.75
0.80
0.87
0.93
0.98
1.04
1.09
1.15
1.20
1.25
1.31
1.58
1.83
3
A
3.50
4.68
5.67
6.72
7.83
9.00
10.23
11.52
12.87
14.28
15.75
17.28
18.87
20.52
22.23
24.00
33.75
45.00
1
R
0.41
0.48
0.54
0.61
0.67
0.73
0.79
0.85
0.91
0.96
1.01
1.07
1.13
.18
.24
.29
.55
.80
4:1
A R
4.00 0.40
5.04 0.46
6.16 0.52
7.36 0.58
8.64 0.64
10.00 0.70
11.44 0.76
12.96 0.82
14.56 0.87
16.24 0.93
18.00 0.98
19.84 1.03
21.76 1.09
23.76 1.14
25.84 1.19
28.00 1.24
40.00 1.50
54.00 1.76


0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5
A
4.25
5.90
6.65
8.00
9.45
11.00
12.65
14.40
16.25
18.20
20.25
22.40
24.45
27.00
29.45
32.00
46.25
63.00
1
R
0.38
0.45
0.51
0.56
0.62
0.68
0.73
0.79
0.85
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.47
1.72
6:1
A
4.50
5.76
7.14
8.64
10.26
12.00
13.86
15.84
17.94
20.16
22.50
24.96
27.54
30.24
33.06
36.00
52.50
72.00

R
0.37
0.43
0.49
0.55
0.61
0.66
0.72
0.77
0.82
0.87
0.92
0.98
1.03
1.08
1.14
1.19
1.45
1.70
7:
A
4.75
6.12
7.63
9.28
11.07
13.00
15.07
17.28
19.63
22.12
24.75
27.52
30.43
33.48
36.67
40.00
58.75
81.00
1
R
0.36
0.42
0.48
0.54
0.59
0.65
0.70
0.75
0.80
0.85
0.91
0.96
1.01
1.06
1.12
1.17
1.46
1.71
8:1
A
5.00
6.48
8.12
9.92
11.88
14.00
16.28
18.72
21.32
24.08
27.00
30.08
33.32
36.72
40.28
44.00
65.00
90.00

R
0.36
0.41
0.47
0.53
0.58
0.63
0.69
0.74
0.79
0.84
0.90
0.95
1.00
1.08
1.10
1.15
1.40
1.65
9
A
5.25
6.84
8.61
10.56
12.69
15.00
17.49
20.16
23.01
26.04
29.25
32.64
36.21
39.96
43.89
48.00
71.25
99.00
1
R
0.35
0.41
0.46
0.49
0.57
0.62
0.67
0.75
0.78
0.83
0.88
0.93
0.97
1.04
1.09
1.13
1.39
1.66
10:1
A R
5.50 0.34
7.20 0.40
9.10 0.45
11.20 0.51
13.50 0.55
16.00 0.61
18.70 0.67
21.60 0.72
24.70 0.77
28.00 0.82
31.50 0.87
35.20 0.92
39.10 0.97
43.20 1.02
47.50 1.07
52.00 1.12
77.50 1.38
108.00 1.65
                IV.77

-------
         Table IV.C.4.—Continued
	WP





t
d
|


^ *7 > 	
\
«-x

\
d-frl«

A
I 	 8

~^/1

	 1

S X
J A xd2
WP 2di
+ 8d
/1 + X

2 + 8




R = A/WP
Depth,
d
(feet)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
Slope ratio
1:1
A
4.25
5.16
6.09
7.04
8.01
9.00
10.01
11.04
12.09
13.16
14.25
15.36
16.49
17.64
18.81
20.00
26.25
33.00

R
0.45
0.53
0.61
0.69
0.76
0.83
0.90
0.97
1.04
1.10
1.16
1.23
1.29
1.35
1.41
1.46
1.76
2.00
1V4
A
4.38
5.34
6.34
7.36
8.42
9.50
10.62
11.76
12.94
14.14
15.38
16.64
17.44
19.26
20.63
22.00
29.38
37.50
1
R
0.45
0.53
0.60
0.68
0.75
0.82
0.89
0.95
1.02
1.08
1.14
1.21
1.27
1.33
1.40
1.45
1.72
1.99
2:
A
4.50
5.52
6.58
7.68
8.82
10.00
11.22
12.48
13.78
15.12
16.50
17.92
19.38
20.88
22.42
24.00
32.50
42,00
1
R
0.44
0.52
0.59
0.66
0.73
0.80
0.87
0.93
1.00
1.06
1.12
1.18
1.24
1.30
1.36
1.42
1.69
1.96
2Vz:1
A R
4.63 0.43
5.70 0.51
6.83 0.58
8.00 0.65
9.22 0.72
10.50 0.78
11.83 0.85
13.20 0.91
14.63 0.98
16.10 1.04
17.63 1.10
19.20 1.16
20.83 1 .22
22.50 1.27
24.23 1.33
26.00 1 .39
35.63 1.66
46.50 1 .93
3:1
A
4.75
5.88
7.07
8.32
9.63
11.00
12.43
13.92
15.97
17.08
18.75
20.48
22.27
29.12
26.03
28.00
38.75
51.00

R
0.43
0.50
0.57
0.64
0.70
0.77
0.83
0.89
0.95
1.01
1.07
1.13
1.19
1.24
1.30
1.36
1.63
1.89
4:1
A
5.00
6.24
7.56
8.96
10.44
12.00
13.64
15.36
17.16
19.04
21.00
23.04
25.16
27.36
29.64
32.00
45.00
60.00

R
0.41:
0.48.
0.55
0.61
0.68
0.74
0.80
0.86
0.92
0.97
1.03
1.09
1.14
1.20
1.25
1.31
1.57
1.83


0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.5
3.0
5:
A
5.25
6.00
8.05
9.60
11.25
13.00
14.85
16.80
•i8.85
21.00
23.25
25.60
28.25
30.60
33.25
36.00
57.25
69.00
1 6:1
R
0.40
0.47
0.53
0.59
0.65
0.71
0.77
0.83
0.88
0.92
1.00
1.05
1.11
1.16
1.22
1.28
1.54
1.80
A
5.50
6.96
8.54
10.24
12.06
14.00
16.06
18.24
20.54
22.96
25.50
28.16
30.94
33.84
36.86
40.00
57.50
78.00
R
0.39
0.44
0.52
0.58
0.64
0.70
0.75
0.81
0.86
0.91
0.97
1.03
1.08
1.13
1.18
1.24
1.50
1.77
7
A
5.75
7.32
9.03
10.88
12.87
15.00
17.27
19.68
22.23
24.92
27.75
30.72
33.85
37.08
40.47
44.00
63.75
87.00
:1
R
0.38
0.44
0.50
0.56
0.63
0.68
0.73
0.79
0.84
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.48
1.74
8:1
A R
6.00 0.37
7.68 0.43
9.52 0.49
11.20 0.54
13.68 0.61
16.00 0.66
18.48 0.72
21.12 0.77
23.92 0.83
26.88 0.88
30.00 0.93
33.28 0.98
36.72 1.04
40.32 1.08
44.08 1.14
48.00 1.19
70.00 1.45
96.00 1 .70
9:
A
6.25
8.04
10.01
12.16
14.49
17.00
16.96
22.56
25.61
28.84
32.25
35.84
39.61
43.56
47.69
52.00
76.25
105.00

R
0.36
0.43
0.48
0.54
0.60
0.65
0.71
0.76
0.81
0.86
0.92
0.97
1.02
1.07
1.12
1.18
1.43
1.70
10
A
6.50
8.40
10.50
12.80
15.30
18.00
20.90
24.00
27.30
30.80
34.50
38.40
42.50
46.80
51.30
56.00
82.50
114.00
1
R
0.36
0.42
0.48
0.53
0.59
0.64
0.69
0.74
0.79
0.84
0.90
0.96
1.01
1.06
1.11
1.16
1.42
1.69
                 IV.78

-------
           Table IV.C.4.-Continued
	WP
                           A = xd2 + 10d
                         WP = 2d V1 + x2 + 10
                           R = A/WP
Depth,
d

-------
Table IV.C.5. Hydraulic radius (R) and area (A) of nonsymmetrical trapezoidal channels
                                [2' bottom width].


\
I 1
	 WP
l\
y
%
A
Y ^

X
1



A = 1/2d2(x+y) + 2d
WP = d( Vl+y2 + Vl+x2) + 2
R = A/WP
Depth,
d
(feet)
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.2
2.4
2.6
2.8
3.0
3.5
4.0
Slope ratio
1:1
A
4.00
4.62
5.28
5.98
6.72
7.50
8.32
9.18
10.08
11.02
12.00
14.08
16.32
18.72
21.28
24.00
31.50
40.00
-3:1
R
1V2:1
A
0.61 4.25
0.66 4.92
0.70 5.64
0.75 6.40
0.80 7.21
0.85 8.06
0.89 8.96
0.94 9.90
0.99 10.89
1.03 11.92
1.07 13.00
1.17 15.29
1.26 17.76
1.35 20.41
1.43 23.24
1.52 26.25
1.76 34.57
1.97 44.00
-3:1
R
0.61
0.66
0.71
0.76
0.80
0.85
0.91
0.95
1.00
1.04
1.09
1.19
1.28
1.37
1.46
1.54
1.78
2.00
2:1 -
A
4.50
5.23
6.00
6.83
7.70
8.63
9.60
10.63
11.90
12.83
14.00
16.50
19.20
22.10
25.20
28.50
37.63
48.00
3:1
R
0.61
0.66
0.71
0.76
0.81
0.85
0.91
0.95
1.01
1.05
1.10
1.19
1.28
1.37
1.48
1.57
1.80
2.02
2Vz:1
A
4.75
5.53
6.36
7.25
8.19
9.19
10.24
11.35
12.51
13.73
15.00
17.71
20.64
23.79
27.16
30.75
40.70
52.00
-3:1
R
0.61
0.66
0.70
0.75
0.81
0.85
0.90
0.95
1.00
1.05
1.10
1.19
1.29
1.38
1.48
1.57
1.81
2.03
4:1
A
5.50
6.44
7.44
8.52
9.66
10.88
12.16
13.52
14.94
16.44
18.00
21.34
24.96
28.86
33.04
37.50
49.88
64.00
-3:1
R
0.59
0.64
0.68
0.73
0.79
0.84
0.90
0.94
0.98
1.03
1.09
1.19
1.28
1.38
1.48
1.57
1.81
2.04
5:1 -
A
6.00
7.04
8.16
9.36
10.64
12.00
13.44
14.96
16.56
18.24
20.00
23.76
27.84
32.24
36.76
42.00
56.01
72.00
3:1
R
0.58
0.63
0.68
0.74
0.79
0.84
0.88
0.93
0.98
1.03
1.08
1.18
1.27
1.37
1.48
1.57
1.81
2.04
                                      IV.80

-------
             Table IV.C.5. —Continued
	WP


n
1
[\
y
A

^ 	 „
u,
Depth,
d
(feet)
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.2
2.4
2.6
2.8
3.0
3.5
4.0
_^
*f
V




r x
J A = 1/2d2(x+y) + 4d
WP = d(/1+y2 + y 1+x2)
R = A/WP
+ 4

Slope ratio
1:1-
A
6.00
6.82
7.68
8.58
9.52
10.50
11.52
12.58
13.38
14.82
16.00
18.48
21.12
23.92
26.88
30.00
38.50
48.00
3:1
R
0.70
0.75
0.80
0.86
0.91
0.97
1.02
1.06
1.10
1.17
1.22
1.31
1.41
1.51
1.60
1.69
1.93
2.15
1 Vz:1
A
6.25
7.12
8.04
9.00
10.01
11.06
12.16
13.30
14.49
15.72
17.00
19.69
22.56
25.61
28.84
32.25
41.57
52.00
-3:1
R
0.69
0.75
0.80
0.86
0.91
0.97
1.02
1.07
1.12
1.17
1.22
1.32
1.42
1.51
1.61
1.71
1.94
2.17
2:1
A
6.50
7.43
8.40
9.43
10.59
11.63
12.80
14.03
15.50
16.63
18.00
20.90
24.00
27.30
30.80
34.50
44.63
56.00
-3:1
R
0.69
0.75
0.81
0.85
0.92
0.96
1.01
1.07
1.13
1.17
1.22
1.32
1.41
1.51
1.62
1.71
1.95
2.18
2V4:1
A
6.75
7.73
8.76
9.85
10.99
12.19
13.44
14.75
16.11
17.53
19.00
22.11
25.44
28.99
32.76
36.75
47.70
60.00
-3:1
R
0.68
0.74
0.79
0.85
0.90
0.95
1.00
1.06
1.11
1.16
1.21
1.31
1.41
1.51
1.61
1.71
1.95
2.18
4:1 -
A
7.50
8.64
9.84
11.12
12.46
13.88
15.36
16.92
18.54
20.24
22.00
25.74
29.76
34.06
38.64
43.50
56.88
72.00
3:1
R
0.66
0.72
0.78
0.81
0.88
0.93
0.98
1.04
1.08
1.13
1.18
1.29
1.38
1.49
1.59
1.68
1.93
2.16
5:1-
A
8.00
9.24
10.56
11.96
13.44
15.00
16.64
18.36
20.16
22.04
24.00
28.16
32.64
37.44
42.36
48.00
63.07
80.00
3:1
R
0.65
0.70
0.76
0.81
0.87
0.92
0.96
1.01
1.07
1.12
1.17
1.27
1.37
1.47
1.57
1.66
1.92
2.15
                        IV.81

-------
              Chapter V

 SOIL MASS MOVEMENT

this chapter was prepared by the following individuals:
            Douglas Swanston
           Frederick  Swanson

        with major contributions from:
             David Rosgen
                 V.i

-------
                            CONTENTS
                                                             Page

INTRODUCTION	  V.I
DISCUSSION 	  V.3
   REVIEW OF RELEVANT WORK	  V.3
   ASSUMPTIONS	  V.4
   PRINCIPLES AND INTERPRETATIONS OF SOIL MASS
     MOVEMENT PROCESSES 	  V.5
     Principle Soil Mass Movement Processes	  V.5
       Slump-Earthflows	  V.6
       Debris Avalanches-Debris Flows	  V.8
       Soil Creep	  V.10
       Debris Torrents	  V.14
     Mechanics Of Movement 	  V.15
     Controlling And Contributing Factors	  V.17
   CHARACTERIZING UNSTABLE SLOPES IN
     FORESTED WATERSHEDS 	  V.18
THE PROCEDURE	  V.22
   ESTIMATING SOIL MASS MOVEMENT HAZARD AND
     SEDIMENT DELIVERED TO CHANNELS 	  V.22
   PROCEDURAL DESCRIPTION  	  V.22
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS	  V.46
CONCLUSIONS	  V.46
LITERATURE CITED  	  V.47
                               V.ii

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                              LIST OF FIGURES
Number                                                                   Page

V.I. —General flow chart of the soil mass movement procedure	    V.2
V.2. —Illustration of various types of soil mass movement processes	    V.6
V.3. —Slump and earthflow in deeply weathered sandstones and siltstones in
         the Oregon Coast Ranges	    V.7
V.4. —Debris avalanche and debris  torrent development on steep forested
         watersheds in northwestern North America 	    V.9
V.5. —An example of soil creep and slump-earthflow processes on forest lands in
         northern California	    V.ll
V.6. —Deformation of inclinometer tubes at two sites in the southern Cascade
         and Coast Ranges  of Oregon	    V.13
V.7. —Simplified diagram of forces acting on a mass of soil on a slope	    V.16
V.8. —Detailed flow chart of the soil  mass  movement procedure	    V.24
V.9. —Dimensions  of  debris  avalanche-debris  flow failures  for  determining
         potential volumes	    V.38
V.10.—Dimensions  of slump-earthflow  failures  for  determining potential
         volumes  	    V.38
V.ll.—Delivery potential of debris avalanche-debris flow material to  closest
         stream	    V.43
V.12.—Delivery potential of slump-earthflow material to closest stream	    V.44
                                     V.iii

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                               LIST OF TABLES
Number                                                                    Page
V.I.—Observations of movement rates of four active earthflows	   V.8
V.2.—Debris avalanche erosion in forest, clearcut, and roaded areas	   V.10
V.3.—Examples of measured rates  of natural creep on forested slopes in the
        Pacific Northwest	   V.12
V.4.—Characteristics of debris  torrents with respect to  debris avalanches and
        land use status of initiations  	   V.14
V.5.—Weighting factors for determination of natural hazard of debris avalanche-
        debris flow failures  	   V.26
V.6.—Weighting factors for determination of management-induced  hazard of
        debris avalanche-debris flow failures 	   V.29
V.7.—Weighting factors for determination of natural hazard of slump-earthflow
        failures  	   V.32
V.8.—Weighting factors for determination  of management-induced hazard  of
        slump-earthflow failures	   V.35
V.9.—Unit weight  of typical soils in the natural state	   V.42
                                      V.iv

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                           LIST OF WORKSHEETS


Number                                                                 Page
V.I    Debris avalanche-debris flow natural factor evaluation form  	   V.28
V.2    Debris avalanche-debris  flow management related  factor evaluation
         form 	   V.30
V.3    Slump-earthflow natural factor evaluation form	   V.34
V.4    Slump-earthflow management related factor evaluation form	   V.36
V.5    Estimation of volume per failure 	   V.39
V.6    Estimation of soil mass movement delivered to the stream channel. ..   V.40
                                     V.v

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                                      INTRODUCTION
  Accurate models and the data needed to predict
soil mass movement hazard  and  magnitude  of
delivery to stream courses over broad areas are cur-
rently lacking. Existing techniques for site specific
stability analyses (based on the Mohr -Coulomb
Theory of Earth Failure) are quite accurate in as-
sessing the strength-stress relationships in a small
area. These techniques,  however, require accurate
measurement of the  engineering properties of the
soils involved and specific knowledge of the geology
and ground water hydrology at the site. Such data
are costly to obtain and vary greatly among sites,
even under the same geologic and climatic settings,
making this mechanistic approach impractical for
broad area hazard assessment.
  A more practical approach is to combine:
  1. A  subjective evaluation  of  the  relative
    stability  of an  area using soils,  geologic,
    topographic,  climatic,  and vegetative in-
    dicators obtained from aerial photos,  maps,
    and field observations.
  2. A limited strength-stress analysis of the un-
    stable sites using available or easily generated
    field data.
  3. Estimates of sediment delivery to streams
    based  on  failure type,  distance  from  the
    stream  channel, and certain  site variables
    such as slope gradient and slope irregularity.
This information can be integrated to provide a
measure of mass movement hazard and the level  of
sediment contributed to adjacent stream channels.
  Such an approach is developed in this chapter  to
provide  a uniform framework for slope stability as-
sessment and estimation of sediment delivery  to
channels by soil mass movement. A flow chart  of
this procedure is presented in figure V.I.
   The primary objectives of the procedure are to
 determine: (1) natural stability of the site, (2) the
 sensitivity of the site to natural and man-induced
 soil mass movement events  (the hazard index of
 soil mass movement generation or  acceleration),
 (3) the probable volume of material released by soil
 mass movement, and (4) the amount of soil mass
 movement  material  delivered to the  nearest
 drainageway.

   Several common site and climatic factors which
 vary greatly  over a wide region are related to soil
 mass movements. To provide for continuity  over
 multiple geographic areas,  the major factors  con-
 trolling slope stability  are  summarized here by
 dominant failure  types and placed in a framework
 of hazard index analysis.

  If the  user does not  have experience in
 delineating potential soil mass movement sites, ad-
 ditional assistance will be required from specialists
 in  the  allied  fields  of  geology,   geotechnical
 engineering, and soil science. Users are strongly ad-
 vised to seek assistance  from  these  specialists
 whenever possible.

  This chapter examines two groups  of  erosion
processes: (1) rapid, shallow soil mass movements,
collectively  termed "debris avalanches-debris
flows", but including a broad range of processes
such as  debris slides and rapid mudflows (Varnes
 1958); and (2) slow, deep-seated soil mass move-
ments, termed "slumps" and "earthflows" or col-
 lectively "slump-earthflows." These mass move-
 ment processes are described further in the section,
 "Principals and Interpretations of Soil Mass Move-
 ment Processes."
                                              V.I

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                                 SOIL MASS
                                 MOVEMENT
                     BROAD DELINEATION OF POTENTIALLY
                             UNSTABLE TERRAIN
  SLUMP-EARTHFLOW

                          SOIL MASS MOVEMENT TYPE
                               DEBRIS SLIDE-
                             DEBRIS AVALANCHE
     HAZARD INDEX
                               HAZARD INDEX
   QUANTITY OF SOIL
       INVOLVED
 DELIVERY OF INORGANIC
  MATERIAL TO CLOSEST
STREAM (SLOPE POSITION)
     PROCEDURAL STEP
     COMPUTATION OB
       EVALUATION
<3    > 'o-o
                             QUANTITY OF SOIL
                                 INVOLVED
      POTENTIAL
SEDIMENT DELIVERED TO
   CHANNEL SYSTEM
                          DELIVERY OF INORGANIC
                           MATERIAL TO CLOSEST
                              STREAM (SLOPE
                          GRADIENT & SLOPE SHAPE)
               Figure V.1.—General flow chart of the soil mass movement procedure.
                                   V.2

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                                        DISCUSSION
      REVIEW OF RELEVANT WORK
  Although quantitative assessment of all factors
contributing to mass movement is complex and dif-
ficult,  a consistent analysis  of the  major  con-
tributing factors  can benefit  the  land  manager,
whose  activities may affect slope  stability. Bur-
roughs and  others  (1976)  discuss  the  effects  of
geology and structure in northern  California and
western Oregon on landslides generated by road
construction;   Swanston and  Swanson (1976)
describe the effects of geomorphology, climate, and
forest management activities on debris avalanche
and slump-earthflow  activity in the western
Cascades; Greswel,  and others (in  press) have as-
sessed the effects  of clearcut logging and road con-
struction on accelerated debris avalanche activity
during a single high intensity storm in the Oregon
Coast Range; Burroughs and Thomas (1977) have
analyzed the declining root strength in Douglas-fir,
after felling,  as a  factor in slope  stability; and
Flaccus (1958), Hack and Goodlet (1969), and Wil-
liams and Guy (1973) discuss the effects of hur-
ricane  and cloudburst triggered soil  mass move-
ment in the eastern United States.
  Some interesting and successful techniques also
have  been  developed  for  predicting  unstable
ground and  identifying controlling  and  con-
tributing factors. Pillsbury (1976), for example,
using a linear discriminant functions  analysis, at-
tributed 90.5 percent of the debris avalanches  in
clearcut areas of a northern California watershed to
the factors of slope percent and percent cover by
dominant and understory vegetation. Both of these
factors  were  determined   by  photogrammetric
techniques with no ground control. An additional
1.5 percent of debris avalanche occurrences was
determined by adding  in the site factors of soil
weathering and percent quartz in  bedrock. Using
photogrammetric  procedures,  Kojan,  Foggin, and
Rice (1972) were able to predict 84.4 percent of the
debris slides following major storms in the Santa-
Ynez-San Rafael  Mountains, California, based on
past landslide activity.
  The factor of safety is commonly used  as a quan-
titative expression  of the hazard  index of a soil
mass movement. In soil mechanics, it is customary
to express the balance of forces acting on a simple
slope as:
                                                    Factor of safety (F) =
                      Resistance of the soil to
                          failure (shear strength)
                      Forces promoting  failure
                      (shear stress)
  A safety factor of one (F=l) would indicate im-
minent failure. For broad land use planning pur-
poses, this technique is valid only for rapid, shallow
soil mass movements, such as debris avalanches
and debris flows. Quantitative models utilizing this
approach have  been outlined in Swanson and
others  (1973), Brown and Sheu (1975), Bell and
Swanston (1972), and Simons  and Ward (1976).
The difficulty in determining some of the factors
(such as  tensile strength of roots,  location  of the
failure surface, and water table position for various
storm intensities) has until recently, restricted the
use of such  models to highly instrumented sites
where  expensive investigations were  warranted.
New data and techniques are being developed,
however,   which are making  these models more
practical  as land management tools.
  Swanston (1972, 1973) has employed a factor of
safety technique using a simplified infinite slope
model to predict slope stability hazard and stratify
lands  according  to  management  impact  in
southeast Alaska.  This technique  uses slope
gradient  as a prime hazard index. Bell and Keener
(1977) have  developed a  method of predicting
stable cut-slope heights based on the factor  of
safety analysis of  natural slopes.  Burroughs  and
Thomas  (1977)  have analyzed the effects  of soil
shear strength, slope gradient,  soil depth, ground
water rise, and root strength on stability hazard in
the central Coast Range of Oregon. Prellwitz (1977)
has made substantial progress in utilization of the
factor  of safety approach without the need  for ex-
pensive site investigation. The equations account
for buoyant density, fluctuating water tables, and
moisture density.
  Soil mass movements can yield substantial sedi-
ment.  Megahan (1972) and  Megahan and Kidd
(1972a, 1972b) evaluated the effects of logging and
road construction on high erosion  hazard land  in
the Idaho Batholith. They report sediment yields
1.6 times greater from jammer logged sites than
from undisturbed areas (they did not differentiate
between  surface erosion and soil mass movement).
Soil  mass movements from logging roads  in the
same area average 550 times greater than control
                                              V.3

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areas. Swanston and Swanson (1976) report debris
avalanche erosion rates 2 to 4 times greater from
clearcuts and  25 to 344 times greater from roads
than from undisturbed sites in selected areas of the
Coast Range and Cascade Mountains of Oregon,
Washington, and British Columbia.
  Prediction of sediment yield from individual soil
mass movement processes is not well documented.
Individual failure release volumes are available for
a few areas, but there is little information on how
much of the  total  volume initially reaches  the
stream versus how much remains on the slope for
slow release over  time. A  summary of average
debris avalanche volume  from  six studies in the
Pacific Northwest reveals a broad range in average
volumes  from area  to area (Swanson and others
1977).  For  example,  in  the  Mapleton  Ranger
District of the  Oregon Coast Range, an  area of
steep, intricately dissected terrain with very shal-
low soil,  average debris avalanche volume is  less
than 100 yd3(76 m3),  whereas steep areas of lower
drainage density and deeper soils have had debris
avalanches averaging more than 1,000 yd3(765 m3).
In the Mapleton area, Swanson and others (1977)
estimated that 65 percent of the material moved by
debris avalanches in forests entered  streams.
  Since sediment yield values  for individual  soil
mass movements are  very limited, a series of con-
ceptual  delivery curves were developed for this
handbook to approximate the sediment transport
potential  of  dominant  soil  mass movement
processes. These curves are presented as first ap-
proximations  only,  and it may  be  necessary to
develop specific delivery curves  to more accurately
represent local conditions. Delivery relations are
needed to  estimate  sediment supply to streams
where  it  will be  routed through  the  channel
network. The delivery curves in the analysis section
were developed  from  studies of recent failures in
the western Cascades and Coast Range of Oregon,
and  were based on estimates  of the percent of
material released during the initial failure that ac-
tually entered a stream. The site variables which
appeared particularly sensitive to the amount of
soil delivered to a drainageway were: slope gradient
and slope irregularity for  debris avalanche-debris
flows, and slope position with respect to the closest
drainageway  for  slump-earthflows.1  Slump-
earthflow failures not adjacent to streams, are not
considered  principal contributors to  channel
loading in this analysis since their potential impact
on  short-term  sediment  loading is  negligible
          and Swanson, unpublished data.
because of their low delivery efficiencies. Most of
the sediment from mid- and upper-slope failures of
this type remain on  the  slope  following initial
failure and  is delivered to the channel over ex-
tended  periods,  mainly by  surface  erosion and
creep.
               ASSUMPTIONS


  The procedures in this chapter are presented as a
guide for assessing  the stability of natural slopes,
the potential impacts of silvicultural activities  on
slope stability, and predicting sediment contribu-
tions to drainageways from soil mass movements.
In the absence of proven  local techniques, these
procedures  will provide  the best  available es-
timates of soil mass movement.  The procedures are
not rigid. They are a frame of  reference within
which local  data and variables may  be applied to
provide better estimates of relative soil stability
and contributions by soil mass movement to non-
point source pollution.
  Because of the complex  nature of processes and
variables and the need to present the procedures in
a format usable on an inter-regional basis, the fol-
lowing simplifying  assumptions are necessary:

  1. The  determination of hazard index will be
     based on the assumption of a maximum 10-
     year  return  period,  24-hour  rainfall
      (precipitation intensity/duration)  as  a
     potential storm event triggering mass move-
     ment.  If slides in  a particular region occur
     frequently, with storms less than a  10-year
     return  period, the hazard evaluation should
     reflect  this (i.e., a 10-year  event is not neces-
     sary for a high hazard index).
  2.  A three-part hazard index will  be used. The
      numerical ratings are subjective and depend
      on what  is considered to be acceptable for a
      particular land management  activity. For
      purposes of this analysis:
      a. "High hazard" means a greater than 66
        percent chance for a soil mass movement
        within the area evaluated for a  10-year
        return period  storm event.
      b. "Medium  hazard" means a greater than
        33  and less than 66  percent chance for a
        soil mass movement  within  the  area
        evaluated  for  a  10-year return  period
        storm event.
                                               V.4

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     c. "Low hazard" means a less than 33 per-
       cent chance  for a soil mass movement
       within the area evaluated  for a 10-year
       return period storm event.
 3. Large  organic  debris  contributions  to
    drainageways, resulting from  soil  mass
    movement are not considered in estimates of
    sediment delivery.  Although large quantities
    of organic debris are incorporated in the total
    volume of material released to the channel
    by soil mass movement, much of it remains
    in the  channel near the point  of entry.

 4. Sediment delivery to the stream can be es-
    timated from  relationships  between failure
    type and slope gradient, slope position (point
    of origin of failure), and morphology of the
    surface.
 5. Volume of sediment delivered to the channel
    per unit area is a more realistic  measure of
    soil mass movement impact  than is number
    of events.
 6. The  instructions provided  for quantifying
    volumes  can  be readily  applied  by field
    scientists.
 7. Processes  of soil mass movement described
    at this broad  planning level can be readily
    identified and characterized  regardless  of
    geographic location.
 8. Only  slump-earthflows  and debris
    avalanches-debris  flows  will  be  used  to
    evaluate direct, short-term contributions of
    sediment to streams.
    Each of these two categories have been iden-
    tified and described on the basis of material
    characteristics,  failure geometry,  and
    mechanism of movement. These categories
    are most affected by silvicultural activities
    and  have  the greatest potential for  short-
    term water quality degradation.
 9. Surface erosion of landslide material remain-
    ing  on  the  slope  will  be  determined  in
    another section which deals with surface ero-
    sion delivery to stream channels.
10. Debris  torrents  will  not  be  evaluated
    directly. It is assumed that when the hazard
    is high  for debris avalanches-debris flows, it
    will also be high for debris torrents.
11. Sediment  delivered to streams from erosion
    caused  by  creep  will  not  be directly
    evaluated because of  the close inter-
    relationships  of  the  variables involved in
    both  creep and slump-earthflow processes.
      Sediment contributions  from creep will be
      indirectly assessed using the channel erosion
      processes evaluated in "Chapter VI: Total
      Potential Sediment".
  PRINCIPLES AND INTERPRETATIONS
                      OF
   SOIL MASS MOVEMENT PROCESSES


  Silvicultural activities in mountainous regions,
particularly forest harvest  and road construction,
can have a major impact on site erosion and can ac-
celerate transport of soil materials downslope by
soil  mass movement. The resultant downstream
damage from aggradation and degradation of the
channel may cause bank erosion, disrupt aquatic
habitat,  and produce undesirable changes in es-
tuarine configuration and habitat by siltation and
channel alterations. This is particularly true for
areas with steep  slopes subject to  high intensity
rain  and/or rapid snowmelt.
  Where heavy forest vegetation covers the slope,
the high infiltration capacity of the forest soils and
covering  organic  materials generally  protect  the
slopes  from surface erosion. Under these  condi-
tions, soil mass movement  processes are generally
the dominant natural mechanisms of soil transport
from mountain slopes to  stream channels. Only
where bare mineral soil is exposed by disturbance
of the vegetative and organic litter cover, either by
natural processes  or silvicultural activities, does
surface erosion significantly contribute to this slope
transport process.
   Principal Soil Mass Movement Processes


  Downslope soil mass movements result primarily
from gravitational stress. It may take the form of:
(1) failure, both along planar and concave surfaces,
of finite masses of soil and forest debris which move
rapidly  (debris avalanches-debris flows) or slowly
(slump-earthflows) (fig. V.2); (2) pure rheological
flow with minor mechanical  shifting  of  mantle
materials (creep); and (3) rapid  movement  of
water-charged organic and inorganic matter down
stream channels (debris torrents).
  Slope gradient, soil depth,  soil  water content,
and physical soil properties, such as cohesion and
coefficient of friction, control  the mechanics and
rates of soil mass movement.  Geological,
                                             V.5

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                                weathered
                                bedrock,
                                soil, etc.

                                   bedrock
    Slump
                                            Debris  Avalanche
                           very  rapid to
                           extremely rapid
              Earthflow
Figure V.2.—Illustration of various types of soil mass move-
                 ment processes.
       Debris  Slide
                                  very rapid
hydrological, and vegetative factors determine oc-
currence and relative importance of such processes
in a particular area.
Slump-Earthflows

  Where  creep  displacement has  exceeded  the
shear strength of soil, discrete failure occurs and
slump-earthflow features are  formed  (Varnes
1958). Simple slumping takes place as a rotational
movement of a block of earth over a broadly con-
cave slip surface and involves little breakup of the
moving material. Where the moving material slips
downslope and is broken up and transported either
by a flowage mechanism or by gliding displacement
of a series of blocks, the movement is termed slow
earthflow  (Varnes  1958)  (fig. V.3). Geologic,
vegetative, and hydrologic  factors  have  primary
control over  slump-earthflow occurrence.  Deep,
cohesive soils and clay-rich bedrock are especially
prone  to   slump-earthflow   failure,  particularly
where these materials are overlain by hard, compe-
tent rock (Wilson 1970, Swanson and James 1975).
Earthflow movement also appears to be sensitive to
long-term  fluctuations in  soil water  content
(Wilson 1970, Swanston 1976).
                                             V.6

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        Figure V.3.—Slump and earthflow in deeply weathered sandstones and siltstones in the Oregon Coast
         Ranges. The slump occurred almost instantaneously. The resulting earthflow, over a period of several
         hours, dammed a perennial stream and produced the lake in the lower foreground.
  Because earthflows  are  slowly  moving, deep-
seated, poorly drained features, individual storms
probably have much less influence on their move-
ment than on the likelihood of occurrence of debris
avalanches-debris flows. Where planes of slump-
earthflow are more  than  several  meters deep,
weight of vegetation and vertical root anchoring ef-
fects are insignificant.
  Earthflows can move imperceptibly  slowly to
more than 1 m/day in extreme cases. In parts of
northwest North  America, many slump-earthflow
areas appear to be inactive (Colman 1973, Swanson
and James 1975). Where slump-earthflows are ac-
tive, rates of movements  have been monitored
directly by repeated surveying of marked  points
and inclinometers and by measuring deflection of
roadways and other inadvertent reference systems.
These methods have  been used to estimate the
rates of earthflow movement shown in  table V.I
(Swanston and Swanson 1976, Kelsey 1977).
  The area  of occurrence of slump-earthflows  is
mainly determined by bedrock geology. For exam-
ple, in the Redwood Creek basin, northern Califor-
nia, Colman (1973) observed that of the 27.4 per-
cent of the drainage which is in slumps, earthflows,
and older or questionable soil mass movements, a
very high percentage of the  unstable  areas are
located  in  clay-rich and pervasively sheared
sedimentary rocks. Areas underlain by schists and
other more highly metamorphosed rock are much
less prone to deep-seated soil mass movement. The
area of occurrence of slump-earthflows in volcanic
                                               V.7

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                   Table V.1.—Observations of movement rates of active earthflows in the western
                  Cascade Range, Oregon (Swanston and Swanson 1976) and Van Duzen River Basin,
                                      northern California (Kelsey 1977)
Location


Landes Creek1
(Sec.21 T.22S, R.4E.)
Boone Creek1
(Sec.17T.17S, R.5E.)
Cougar Reservoir1
(Sec.29T.17S, R.5E.)
Lookout Creek1
(Sec.30T.15S, R.6E.)

Donaker Earthflow2
(Sec.10T.1N, R.3E.)
Chimney Rock Earthflow2
(Sec.30T.2N,R.4E.)
Halloween Earthflow2
(Sec.6T.1N,R.5E.)
'Swanston and Swanson 1976.
'Kelsey 1977.
Period of
record
years
15

2

2

1


1

1

3



Movement
rate
cm/yr
12

25

2.5

7


60

530

2,720



Method of
observation

Deflection of
road
Deflection of
road
Deflection of
road
Strain rhombus
Measurements across
active ground breaks
Resurvey of stake
line
Resurvey of stake
line
Resurvey of stake
line


terrains  has also been closely linked to bedrock
(Swanston  and  Swanson  1976).   There  are
numerous examples of accelerated or reactivated
slump-earthflow movement after forest road con-
struction in the western United  States (Wilson
1970). Undercutting the toes of earthflows and pil-
ing rock  and soil debris on slump blocks are com-
mon  practices which influence  slump-earthflow
movement.  Stability of such areas is also affected
by  modification of  drainage systems, particularly
where road  drainage systems route additional
water into the slump-earthflow areas. These distur-
bances may increase  movement rates from a  few
millimeters  per year  to  many centimeters. Once
such  areas have been destabilized, they may con-
tinue to move at accelerated rates for several years.

  Although  the impact of deforestation  alone on
slump-earthflow  movement  has  not  been
demonstrated   quantitatively,  evidence  suggests
that it may be significant. In massive, deep-seated
failures, lateral and vertical anchoring by tree root
systems  is  negligible.  Hydrologic  impacts of
deforestation,  however, appear to be  important.
Reduced   evapotranspiration  will  increase   soil
moisture availability.  This water is, therefore,  free
to pass through the rooting zone to deeper levels of
the  earthflow.
Debris Avalanches-Debris Flows

  Debris avalanches-debris flows are rapid, shal-
low soil mass movements from hillslope areas. Here
the term "debris avalanche-debris flow" is used in
a  general  sense  encompassing debris  slides,
avalanches,  and  flows which  have been dis-
tinguished by Varnes (1958) (fig. V.  4) and others
on the basis of increasing water content and type of
included  material.  From  a  land  management
standpoint, there is little purpose to differentiating
among the types of shallow hillslope failures, since
the mechanics and the controlling and contributing
factors are  the same.  Areas  prone  to  debris
avalanches-debris  flows  are typified by shallow,
noncohesive soils on  steep slopes where subsurface
water may be concentrated by subtle topography
on bedrock or glacial till surfaces. Because debris
avalanches-debris  flows are shallow failures, fac-
tors such as  root strength, anchoring effects, and
the transfer of wind stress to the-jsoil mantle are
potentially important influence. Factors which in-
fluence antecedent soil moisture conditions and the
rate of water supply to the soil during snowmelt
and rainfall also have significant control over the
time and place of debris avalanches-debris flows.
  The rate of occurrence of debris avalanches-
debris flows  is controlled by the  stability of the
                                               V.8

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Figure V.4.—Debris avalanche  and  debris  torrent development on steep  forested watersheds In
  northwestern North America, (a.) Debris avalanche developed in shallow cohesionleas soils on a steep,
  forested slope In coastal Alaska, (b.) Debris torrent developed in a steep gully, probably caused by failure
  of a natural debris dam above trees in foreground.
                                              V.9

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landscape and the frequency of storm events severe
enough to trigger them. Therefore, the rates of ero-
sion by debris avalanches-debris flows will  vary
from one  geomorphic-climatic setting to another.
Table  V.2 (Swanston and  Swanson 1976) shows
that annual rates of debris avalanche erosion  from
forested study sites  in Oregon and Washington in
the  United  States, and  British  Columbia  in
Canada, range from 11  to 72 m3/km2/yr. These es-
timates are based on surveys and measurements of
debris  avalanche erosion during a particular  time
period  (15 to over 32 years) over a  large area (12
km2 or larger).
  An analysis of harvesting  impacts in the western
United States (Swanston and Swanson 1976) (table
V.2) reveals that  timber  harvesting  commonly
results in an acceleration of soil mass movement
activity by  a factor of 2 to 4 times  relative  to
forested areas. In the  four study  areas  listed  in
table V.2, road-related debris avalanche erosion
was increased by factors ranging from 25 to 340
times  the rate  of  debris  avalanche erosion in
forested areas. The great variability in the impact
of roads reflects not only differences in the natural
stability of the landscape, but also, and more im-
portantly from   an  engineering standpoint,  dif-
ferences in site location, design, and  construction
of roads.

Soil Creep

  Soil creep  is  defined as  the slow, downslope
movement of soil mantle materials as the result of
long-term application of gravitational stress. The
mechanics of soil creep have been investigated ex-
perimentally  and  theoretically (Terzaghi  1953,
Goldstein  and  Ter-Stepanian  1957,  Saito and
Uezawa 1961,  Culling 1963, Haefeli 1965, Bjerrum
1967,  Carson  and  Kirkby  1972).  Movement is
quasi-viscous; it occurs under shear  stresses suf-
ficient to produce permanent deformation, but too
small to result in discrete failure. Mobilization of
   Table V.2.—Debris avalanche erosion in forest, clearcut, and roaded areas (Swanston and Swanson 1976)
Site

Period of
record
years
	 Area
percent
	
km2
Number
of
slides

Debris
avalanche
erosion
mVkmVyr
Rate of debris avalanche
erosion relative
to forested areas

Stequaleho Creek, Olympic Peninsula, Washington, U.S.A. (Fiksdal 1974):
   Forest          84          79.0          9.3           25          71.8
   Clearcut         6          18.0          4.4            0           0.0
   Road            6           3.0          0.7           83      11,825.0
                                          24.4
  108
Alder Creek, Western Cascade Range, Oregon, U.S.A. (Morrison 1975):
   Forest          25          70.5         12.3            7          45.3
   Clearcut        15          26.0          4.5           18         117.1
   Road           15           3.5          0.6           75      15,565.0
                                          17.4
  100
 Selected drainages, Coast Mountains, S.W. British Columbia, Canada:1
   Forest          32          83.9        246.1           29
   Clearcut        32           9.5         26.4           18
   Road           32           1.5          4.2           11
               11.2
               24.5
             '282.5
                                         276.7
   58
 H. J. Andrews Experimental Forest, western Cascade Range, Oregon, U.S.A.
 (Swanson and Dyrness 1975):
   Forest          25          77.5          49.8          31          35.9
   Clearcut        25          19.3          12.4          30         132.2
   Road           25           3.2           2.0          69       1,772.0
                                           64.2
  130
                                  1.0
                                  0.0
                                165.0
                                  1.0
                                  2.6
                                344.0
 1.0
 2.2
25.2
                                  1.0
                                  3.7
                                 49.0
   'Calculated from O'Loughlin (1972, and personal communication), assuming that area involving road construction in and
outside clearcuts is 16 percent of area clearcut. Colin L. O'Loughlin, is now at Forest Research Institute, New Zealand Forest
Service, Rangiora, New Zealand.
                                                V.10

-------
the soil mass is primarily by deformation at grain
boundaries and within  clay mineral  structures.
Both interstitial and absorbed water appear to con-
tribute to creep movement by opening the struc-
ture within and between mineral grains, thereby
reducing friction within the soil mass. Creeping ter-
rain can be recognized by  characteristic rolling,
hummocky topography with frequent  sag ponds,
springs,  and  occasional benching due  to local
rotational slumping. Local discrete failures, such
as debris avalanches and slump-earthflows, may be
present within the creeping mass (fig.  V.5).
  Natural  creep  rates  monitored in  different
geological materials in the  western Cascade and
Coast Ranges of Oregon and northern California in-
dicate rates of movement between 7.1 and 15.2
mm/yr,  with the  average  about  10  mm/yr
(Swanston and  Swanson 1976)  (table V.3). The
most rapid movement usually occurs at or near the
surface, although the significant displacement may
extend to variable depths associated with incipient
failure planes or zones of ground water  movement.
Active creep depth varies greatly and  largely de-
pends on parent material origin, degree and depth
of weathering, subsurface structure, and soil water
content. Most movement appears  to  take place
during rainy season maximum soil water levels (fig.
V.6 a), although  creep may remain constant
throughout the year in areas where the  water table
does not undergo significant seasonal fluctuation
(fig.  V.6 b).  This  is  consistent  with  Ter-
Stepanian's  (1963)  theoretical  analysis  which
shows that the downslope creep rate of an inclined
soil layer is exponentially related to piezometric
level in the slope.
  There have been no direct measurements of the
impact of deforestation on creep rates in the forest
environment, mainly because of the long periods of
records needed both before and after a disturbance.
There are,  however, a number of indications  that
creep rates are accelerated by harvesting and  road
construction.
  In the United States, Wilson (1970) and others
have used inclinometers to monitor accelerated
creep following modification of slope angle, com-
paction of fill  materials, and distribution of soil
mass at construction sites.  The common occur-
rence of shallow soil mass movements in these dis-
turbed areas and open tension cracks in fills along
roadways suggests that similar features along forest
roads  indicate significantly  accelerated  creep
movement.
  On open slopes where deforestation is the  prin-
cipal influence, impact on creep rates may be more
subtle,  involving modifications of hydrology and
root strength. Where  creep is a  shallow
phenomenon (less than several meters), the loss of
Figure V.5.—An example of soil creep
  and  slump-earthflow processes  on
  forest lands in northern California.
  The entire slope is undergoing creep
  deformation, but note the discrete
  failure (slump-earthflow) marked by
  the  steep  headwall scarp at top
  center and the many small slumps
  and  debris avalanches triggered by
  surface springs and road construc-
  tion.
                                               V.ll

-------
        Table V.3—Examples of measured rates of natural creep on forested slopes in the Pacific Northwest
                                         (Swanston and Swanson 1976)
Location
Coyote Creek,
South Umpqua
River drainage,
Cascade Range
of Oregon,
SiteC-1
Blue River
drainage -
Lookout Creek,
H. J. Andrews Exp,
Forest,
Central Cascades
of Oregon,
Site A- 1
Blue River
drainage, IBP
Experimental
Watershed 10,
Site No. 4
Baker Creek
Coquille River
Coast Range,
Oregon
Site B-3
Bear Creek
Nestucca River
Coast Range,
Oregon
Site N-1
Data Parent material Depth of Maximum downslope Representative
source significant Creep rate creep profile
movement Surface Zone of
accelerated
movement
m mm/yr mm/yr
Swanston1 Little Butte
volcanic series;
deeply weathered, 7.3 13.97 10.9
clay-rich, andesitic
dacitic, volcani-
clastic rocks
Little Butte
Swanston1 volcanic series
5.6 7.9 7.1
Same as above


UPSLOPE DOWNSLOPE
I
P '
j
5 Ł
0-
Ul
a
-IO.O 0 IO.O
DEFLECTION (mm)
UPSLOPE DOWNSLOPE
I
I
/
I
-IO.O 0 IO.O
DEFLECTION (mm)
0
~Ł
15 i
UJ
o
SO
McCorison2 Little Butte
and Glenn volcanic series 0.5 9.0
SJmaflor?1 UPSLOPE °™"SWE
Swanston1 highly sheared 7.3 10.4 10.7
and altered clay-
rich argillite and
mudstone
Nestucca
Swanston1 formation
deeply weathered
pyroclastic rocks 15.2 14.9 11.7
and interbedded,
shaley siltstones
and claystones
i
I
•/ -
-IO.O 0 IO.O
DEFLECTION (mm)
JPSLOPE DOWNSLOPE
I
I
y -
\
-IO.O 0 IO.O
DEFLECTION (mm)
0 _
1
5 Ł
a.
Ul
o
10
0 „
E
5 f.
a.
LJ
a
10
  1Douglas N.  Swanston, unpublished data on  file at Forestry Sciences Laboratory, USDA Forest Service, Pacific Northwest
Forest and Range Experiment Station, Corvallis, Oreg.
  2F Michael McCorison and L. F Glenn, data on file at Forestry Sciences Laboratory, USDA Forest Service, Pacific Northwest
Forest and Range Experiment Station, Corvallis, Oreg.
                                                    V.12

-------
  Table V.3—Examples of measured rates of natural creep on forested slopes in the Pacific Northwest (continued)
Redwood Creek

Coast Range
Northern California
Site3-B
           Kerr Ranch
Swanston1  schist
                              sheared, deeply
                              weathered clayey
                              schist
                 UPSLOPE   DOWNSLOPE
                                  2.6
15.2
10.4
                                                                                   -10.0   o   10.0
                                                                                  DEFLECTION (mm)
                                                                                 0 „
                                                                                 10
  Figure V.6.—Deformation of inclinometer tubes at
    two  sites in the southern  Cascade and Coast
    Ranges  of  Oregon  (Swanston  and  Swanson
    1976). (a ) Coyote  Creek  in  the  southern
    Cascade  Range showing seasonal variation in
    movement rate as the result of changing soil
    water levels. Note that the difference in readings
    between spring and fall of each year (dry months)
    is very small, (b) Baker Creek, Coquille River,
    Oregon Coast  Ranges, showing constant rate of
    creep as a result of continual high water levels.
                                  UPSLOPE
              DOWNSLOPE
                             (b)
                                      • SPRING
                                  -   D FALL
                                                                         0
                                                                                              CL
                                                                                              LU
                                                                                              Q
                                                    5.0


                                                UPSLOPE
                                          2.5        0       2.5
                                          DEFLECTION   (mm)
                          5.0


                    DOWNSLOPE
                                           (a)
                                                     • SPRING

                                                     DFALL



                                                     i     i    i
                                                                                                 0
                                                                              3  Ł

                                                                                 x
                                                                                 I-
                                                                              „  Q.
                                                    9.0      5.0       0       5.0
                                                             DEFLECTION   (mm)
                                                                       9,0
                                                 V.13

-------
root strength caused by deforestation is likely to be
significant. Reduced evapotranspiration  after
clearcutting (Gray 1970,  Rothacher  1971)  may
result in longer duration of the annual period of
creep activity and, thereby, increase  the  annual
creep rate.
Debris Torrents

  Debris torrents involve the rapid movement of
water-charged  soil, rock, and organic  material
down steep stream channels. They typically occur
in steep, intermittent, and first- and second-order
channels. They are triggered during extreme dis-
charge  by debris avalanches from  adjacent  hill-
slopes which enter  a channel and  move directly
downstream or by the breakup and mobilization of
debris accumulations in the  channel (fig.  V.4b).
The initial slurry of water and associated  debris
commonly entrains large quantities of additional
inorganic and organic material from the streambed
and banks. Some torrents are triggered by  debris
avalanches of  less than  100 yd3  (76 m3),  but
ultimately  involve  1,000 yd3 (760  m3) of  debris
entrained along the track of the torrent. As the tor-
rent  moves downstream, hundreds of meters  of
channel may be scoured to bedrock. When a torrent
loses momentum, there is deposition of a tangled
mass of large organic debris in a matrix of sediment
and fine organic material covering areas of up to
several hectares.
     The main factors controlling the occurrence of
   debris torrents  are  the quantity  and stability of
   debris in channels, steepness of channel, stability
   of adjacent hillslopes,  and peak  discharge
   characteristics of the  channel. The concentration
   and stability of  debris  in channels reflect  the
   history of stream flushing and the health and stage
   of development of the surrounding timber stand
   (Froehlich 1973).  The stability of adjacent slopes
   depends on factors described in previous sections.
   The history of  storm  flows has  a controlling in-
   fluence over the stability of both soils on hillslopes
   and debris in stream channels.
     Although  debris  torrents pose significant  en-
   vironmental hazards   in  mountainous  areas  of
   northwestern North America, they  have received
   little study  (Fredriksen 1963, 1965; Morrison 1975;
   Swanson and others 1976). Velocities of debris tor-
   rents,  estimated  to  be up to  several tens  of
   meters/second, are known only from a few verbal
   and written  accounts.  Torrents have  been
   systematically documented in only two small areas
   of the  Pacific  Northwest,  both  in the western
   Cascade Range  of  Oregon (Morrison  1975,
   Swanston and Swanson 1976). In  these studies,
   rates of debris torrent  occurrence were observed to
   be 0.005 and 0.008 events/kmVyr for forested areas
   (table V.4). Torrent tracks initiated  in forest areas
   ranged in length from  328 to 7,480 ft (100 to 2,280
   m) and averaged 2,000 ft (610 m) of channel length.
   Debris avalanches have played a dominant role in
   triggering  83  percent of  inventoried  torrents
Table V.4—Characteristics of debris torrents with respect to debris avalanches1 and land use status of initiation in the
               H. J. Andrews Experimental Forest1 and Alder Creek Drainage (Morrison 1975)
Site          Area of   Period of   Debris torrents
             watershed   record     triggered by
                                debris avalanches
   Debris torrents
 with no associated
  debris avalanche
         Rate of debris
Total  torrent occurrence
          relative to
         forested areas
                km2
number •
H. J. Andrews Experimental Forest, western Cascades, Oregon
   Forest         49.8       25             9
   Clearcut        12.4       25             5
   Road           2.0       25           _17_
                 64.2                    ~31~

Alder Creek drainage, western Cascade Range, Oregon
                      10
                      11
                      17
                      38
 kmVyr
  0.008
  0.036
  0.340
 1.0
 4.5
42.0
Forest
Clearcut
Road

12.3
4.5
0.6
17.4
90
15
15

5
2
6
13
1
1
-
2
6
3
6
15
0.005
0.044
0.667

1.0
8.8
133.4

  'Frederick  J. Swanson, unpublished data, on file at Forestry Sciences Laboratory, USDA Forest Service, Pacific
Northwest Forest and Range Experiment Station, Corvallis, Oreg.
                                               V.14

-------
 (Swanston  and  Swanson 1976).  Mobilization of
 stream debris not immediately related to debris
 avalanches has been a minor factor in initiating
 debris torrents in headwater streams.
  Deforestation appears to dramatically accelerate
 the occurrence of debris torrents by increasing the
 frequency of debris avalanches. Although it has not
 been demonstrated,  it is also possible  that in-
 creased concentrations of unstable debris in chan-
 nels  during forest  harvesting (Rothacher 1959,
 Froehlich 1973, Swanson and others 1976) and pos-
 sible increased peak discharges (Rothacher 1973,
 Harr and  others 1975)  may  accelerate the  fre-
 quency of debris torrents.
  The impact of clearcutting and road construction
 on  frequency of debris  torrents  (events/kmVyr)
 may be compared to debris torrent occurrence un-
 der natural conditions. In the H.  J. Andrews  Ex-
 perimental Forest and the Alder Creek study sites
 in Oregon, timber harvesting appeared to increase
 occurrence of debris torrents by 4.5 and 8.8 times;
 and roads were responsible for increases of 42.5  and
 133 times relative to forested areas.
  Although the quantitative reliability of these es-
timates of harvesting impacts is limited by  the
small number of events  analyzed,  there is clear
evidence of marked acceleration in the frequency of
debris avalanches-debris flows as a result of forest
harvesting  and road building. The histories  of
debris avalanches-debris  flows in the  two study
areas clearly indicate that increased debris torrent
occurrence is primarily  a  result of two conditions:
debris avalanches  trigger  most  debris  torrents
(table  V.4)  and   the  occurrence of  debris
avalanches-debris flows is temporarily accelerated
by deforestation and road construction (table V.2).
           Mechanics of Movement


  Direct application  of soil  mechanics theory to
analysis of soil  mass movement processes is dif-
ficult because of the  heterogeneous nature of soil
materials, the extreme variability of soil water con-
ditions, and the related variations  in stress-strain
relationships with time.  However,   the  theory
provides a convenient framework for discussing the
general  mechanism  and  the  complex  inter-
relationships of the  various  factors  active  in
development of soil mass movements on mountain
slopes.
  In terms of factor of safety analysis, the stability
of soils on a slope can be expressed as a  ratio
between shear strength, or resistance of the soil to
sliding,  and  the downslope pull of  gravity  or
gravitational stress. As long as  shear strength ex-
ceeds the pull of gravity, the soil will remain in a
stable state  (Terzaghi 1950, Zaruba and  Mencl
1969).

  It is important to remember that soil mass move-
ments  result from  changes in  the  soil  shear
strength-gravitational stress relationship in the
vicinity of failure. This may involve a mechanical
readjustment among individual particles or a more
complex interaction between both internal and ex-
ternal factors acting on the slope.

  Figure V.7 shows the geometrical relationship  of
factors acting on a small portion of the soil mass.
Any increases in gravitational stress  will increase
the tendency for the soil to  move downslope.
Increases in  gravitational stress result from in-
creasing inclination of the  sliding surface  or in-
creasing unit  weight  of the soil mass. Stress can
also be augmented by: (1) the presence of zones  of
weaknesses in  the  soil  or underlying  bedrock
produced by bedding planes and fractures, (2) ap-
plication of wind stresses transferred to the soil
through  the stems and root systems  of trees, (3)
strain  or deformation in  the  soil produced by
progressive creep, (4) frictional "drag" produced by
seepage pressure,  (5)  horizontal accelerations due
to earthquakes and blasting, and (6) removal  of
downslope  support by undercutting.

  Shear strength is governed by a more complex in-
terrelationship  between  the soil  and  slope
characteristics. Two principal forces are active in
resisting downslope  movement. These  are:  (1)
cohesion or the capacity of the soil particles to
adhere  together,  a  soil  property produced by
cementation, capillary tension, or weak electrical
bonding  of organic colloids and clay particles; and
(2) the frictional resistance between individual par-
ticles  and between the soil mass and the sliding
surface. Frictional resistance is  controlled by the
angle of internal friction of the soil —  the degree  of
interlocking of individual grains — and the effec-
tive weight of the soil which  includes both the
weight of the soil mass and any surface loading plus
the effect of slope gradient and  excess soil water.

  Pore water pressure — pressure produced by the
head of water in saturated soil and transferred  to
the base of the soil through the pore water — acts
to reduce the frictional  resistance  of the soil by
reducing its effective weight. In effect, its  action
causes the soil to "float" above the sliding surface.
                                               V.15

-------
Figure V.7.—Simplified diagram of forces acting on a mass of soil on a slope (Swanston  1974a).
                                     V.16

-------
     Controlling And Contributing Factors
   Particle size distribution or "texture"  (which
 governs cohesion), angle of internal friction,  soil
 moisture content, and angle of sliding surface are
 the controlling factors in determining stability of a
 steepland soil. For example, shallow coarse-grained
 soils low in clay-size particles have little or no cohe-
 sion,   and  frictional  resistance  determines  the
 strength of the soil mass. Frictional resistance is, in
 turn, strongly dependent on the angle of internal
 friction of the soil and pore water pressure. A low
 angle of internal friction relative to slope angle or
 high  pore water pressure can reduce  soil shear
 strength to negligible values.

   Slope angle is a major indicator of the stability of
 low cohesion soils. Slopes at or above the angle of
 internal friction of the  soil indicate a highly  un-
 stable natural state.

   Soils of moderate to  high clay content exhibit
 more  complex  behavior  because  resistance to
 sliding is determined by both cohesion  and fric-
 tional  resistance. These  factors are controlled to a
 large extent by clay mineralogy and soil moisture.
 In a  dry state,  clayey  soils have a high shear
 strength with the internal angle of friction quite
 high (>30°).  Increasing water content mobilizes
 the clay through absorption of water onto the clay
 structure. The angle of internal friction is reduced
 by the addition of water to the clay lattices (in ef-
 fect reducing "intragranular" friction) and may ap-
 proach zero in  saturated conditions. In  addition,
 water  between grains — interstitial water — may
 open the structure of the soil mass. This permits a
 "remolding" of the clay fraction, transforming it
 into a  slurry,  which then lubricates the remaining
 soil mass. Some clays are more susceptible to defor-
 mation than others, making clay mineralogy an im-
 portant  consideration in areas characterized by
 quasi-viscous  flow deformation  of "creep." Swell-
 ing clays of the smectite group (montmorillenite)
 are particularly unstable because of their tendency
 to absorb large quantities of water and  to  ex-
 perience alternate expansion and contraction dur-
 ing periods of  wetting and drying which may result
 in progressive failure of a slope.  Thus,  clay-rich
 soils have a high potential for failure given excess
 soil moisture  content.  Under  these conditions,
 failures are not  directly  dependent on sliding sur-
 face  gradient  as in  cohesionless soils,  but may
 develop on slopes with gradients as low as 2° or 3°.

  Parent material type  has a major effect on  the
particle size distribution, depth of weathering, and
relative  cohesiveness  of  a steepland soil. It  fre-
quently  can be  used as an indicator of relative
stability or potential stability problems. In humid
regions where chemical weathering predominates,
transformation  of  easily  weathered  primary
minerals to clays and clay-size particles may be ex-
tensive. Siltstones, clay stones, shales, nonsiliceous
sandstones, pyroclastics,  and serpentine-rich rocks
are the  most easily altered and are prime can-
didates for soil  mass movement of the creep and
slump-earthflow types.  Conversely,  in  arid  or
semiarid regions, slopes underlain by these rocks
may  remain stable for  many years due  to slow
chemical weathering processes and lack of enough
soil moisture to mobilize existing clay minerals. On
steep lands underlain by resistant rocks, especially
where mechanical weathering prevails, soils  are
usually coarse and low in clay-size  particles. Such
areas are more likely  to  develop soil mass move-
ments of the debris avalanche-debris flow type.

   Parent material  structure is a critical factor in
stability of many shallow soils.  Highly  jointed
bedrock slopes with principal joint planes  parallel
to the slope provide little mechanical  support to
the slope and create avenues for concentrated sub-
surface  flow and  active  pore water pressure
development, as well as  ready-made zones  of
weakness  and  potential  failure surfaces  for  the
overlying material.  Sedimentary rocks with bed-
ding planes parallel to the slope, function in essen-
tially the same way, with the uppermost bedding
plane forming an impermeable boundary  to sub-
surface water movement, a layer  restricting the
penetration and  development of tree roots, and a
potential failure  surface.
  Vegetation  cover generally  helps control the
amount of water reaching the soil and the  amount
held  as stored  water  against  gravity,  largely
through a  combination  of  interception and
evapotranspiration.  The direct effect of intercep-
tion on the soil water budget is probably not large,
especially  in areas  of high total rainfall or during
large  storms, when most soil mass  movements  oc-
cur. Small storms,  where interception is effective,
probably have  little influence  on total soil water
available for activating mass movements.
  In areas  of low rainfall, the effect of evapotran-
spiration is much more pronounced, but it is par-
ticularly dependent on region and rainfall. In areas
characterized by warm, dry summers, evapotran-
spiration significantly reduces the degree of satura-
tion  resulting from the  first  storms of the fall
recharge period. This  effect  diminishes  as  soil
                                                V.17

-------
water deficit is satisfied. Once the soil is recharged,
the effects of previous evapotranspirational losses
become negligible. Conversely, in areas of con-
tinuous high rainfall  or  those with  an arid or
semiarid climate,  evapotranspirational effects are
probably negligible. Depth of evapotranspirational
withdrawals is  important also. Deep withdrawals
may require substantial recharge to satisfy the soil
water deficit, delaying or reducing the possibility of
saturated soil conditions necessary for major slide-
producing events. Shallow soils, however, recharge
rapidly, possibly becoming saturated and most un-
stable during the first major storm.
  Root systems of trees and other vegetation may
increase  shear strength  in  unstable  soils  by
anchoring through the soil mass into fractures in
bedrock,  providing  continuous  long  fiberous
binders within  the soil  mass,  and tying  the slope
together across zones of weakness or instability.
  In shallow soils, all three effects may be impor-
tant.  In  deep soils,  the anchoring effect of roots
becomes negligible, but the other parameters will
remain important. In some extremely steep areas
in western North America, root anchoring may be
the  dominant factor  in  maintaining  slope
equilibrium of  an  otherwise  unstable  area
(Swanston and Swanson 1976).
  Snow cover increases soil unit weight by surface
loading and affects delivery of water to the soil by
retaining  rainfall  and delaying release  of  much
water. Delayed release of melt water, coupled with
unusually  heavy storms  during a midwinter or
early spring warming trend, has been identified as
the  principal  initiating  factor in  recent  major
landslide  activity  on forest  lands  in central
Washington (Klock and Helvey 1976).
  CHARACTERIZING UNSTABLE SLOPES
       IN FORESTED WATERSHEDS
  The following guidelines  are  designed to help
delineate the hazards of unstable slopes on forested
lands.
  There  are  six  environmental  qualities  that
should  be  carefully  considered  when  judging
stability of natural slopes in terms of surface ero-
sion and soil mass movement. They are:
    A. landform features
    B. soil characteristics
    C. bedrock lithology and structure
    D. vegetative cover
    E. hydrologic characteristics of site
    F. climate
  Each of these qualities encompasses a group of
factors which control  stability conditions on the
slope and  determine  or identify  the  type of
processes and movements which are  most likely to
occur.
  Key  factors  identifying potentially unstable
slopes on any mountainous terrain  include slope
gradient (a landform quality) and concentration of
precipitation (both intensity  and duration).  Soil
properties,  including  soil depth  and such
diagnostic characteristics as texture, permeability,
angle of  internal friction, and cohesion determine
the types of processes that will dominate and, to
some degree, determine the stable slope gradient
within a  particular soil type. Bedrock structure, es-
pecially attitude of beds and degree of fracturing or
jointing,  are important  contributing factors con-
trolling local stability conditions. Many  of these
factors are identifiable on the ground or in readily
available support documentation (climatological
records,  etc.).
  The following outline  discusses the  six  en-
vironmental  qualities  important  for  judging
stability of natural slopes and the key factors as-
sociated  with each.
A.  Landform features
  1. Landforms on which subject area occurs.
     — A qualitative indicator of potentially un-
     stable  landform types. Obtainable from  air
     photos and topographic maps. For example,
     alpine  glaciated terrain characteristically  ex-
     hibits U-shaped valleys with extensive areas
     of very steep slope. Fracturing parallel to the
     slope is common, and soils, either of colluvial
     or glacial  origin,  are usually shallow and
     cohesionless. The  underlying impermeable
     surface may be either bedrock or compact
     glacial till. Such terrain is frequently subject
     to debris  avalanche-debris  flow  processes.
       Areas  formed  by  continental  glaciation
     commonly exhibit rolling terrain consisting of
     low hills and  ridges  composed of bedrock,
     glacial  till, and stratified drift separated  by
     areas of ground moraine and glacial outwash.
     Glaciolacustrine deposits  may be present
     locally, consisting of thick deposits of silt and
     clay  which may  be particularly subject to
     slump-earthflow  processes  if  disturbed.
                                               V.18

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     Fluvially formed landscapes underlain by
   bedded sedimentary and meta-sedimentary
   rocks may have slope steepness controlled by
   jointing, fracturing, and faulting; by orienta-
   tion of bedding; and by differential resistance
   of alternating rock layers. Debris avalanche-
   debris  flow failures frequently occur in shal-
   low colluvial soils  along these structurally
   controlled surfaces. Slump-earthflow failures
   may  occur in clay-rich or deeply weathered
   units, in deeply weathered soils and colluvial
   debris on the lower slopes, and in valley  fills
   adjacent to active stream channels.
     Volcanic terrain consisting of units of easily
   weathered  volcaniclastic  rocks  and  hard,
   resistant flow rock commonly exhibit slump-
   earthflow  failures  in   deeply  weathered
   volcaniclastic materials. Such failures usually
   occur just below a capping flow or just above
   an underlying flow due to concentration of
   ground water. Debris avalanche-debris flow
   failures are common in shallow residual or col-
   luvial soils developed on the resistant flow
   rock  units.
     Because of the large variability in landform
   processes  and  the modifying influence of
   climatic conditions on weathering rates  and
   products, geologists with some knowledge of
   the area should be consulted.
2.  Slope configuration. — Shape of the slope in
   the area  of consideration. A qualitative  in-
   dicator of location  and extent of most highly
   unstable areas on a slope. Obtainable from air
   photos and topographic maps. On both con-
   cave  and convex slopes, usually the steepest
   portions have the  greatest stability hazard.
   Convex slopes may have oversteep gradients
   in lower portions of the slope. Concave slopes
   have  oversteep gradients in their upper eleva-
   tions.
3.  Slope gradient. — A key factor controlling
   soil stability  in steep mountain watersheds.
   Slope gradient  may  be  quantified on  the
   ground or from topographic maps. It deter-
   mines effectiveness of gravity acting to move a
   soil mass  downslope.  For debris avalanche-
   debris flow failures, this is a major indicator of
   the natural soil mass movement hazard.  For
   slump-earthflow failures, this is not as  im-
   portant since, given the right conditions of soil
   moisture  content,   soil  texture,  and  clay
   mineral content, failures can occur on slope
   gradients as low as 2°  or 3°. Slope gradient
     also has  a  major effect on subsurface water
     flow in terms of drainage rate and subsequent
     susceptibility  to temporary  water  table
     buildup during high  intensity storms.

B. Soil Characteristics
  1.  Present soil mass movement type and rate.
     — Obtainable from air  photos  and  field
     checks. This is a qualitative indicator of size
     and location of potential stability  problems,
     type of recent landsliding,  and kinds of soil
     mass movement processes  operative on the
     slope.  These, in turn,  suggest probable soil
     depth  and  certain dominant  soil
     characteristics.  For example,  debris
     avalanches-debris flows  most frequently
     develop in shallow, coarse-grained soils which
     have a low clay content and low internal cohe-
     sion. Soil creep, massive slumping, and large-
     scale  earthflows  usually develop  in deep,
     cohesive soils high in clay content or in deeply
     weathered  pelitic sediments,  serpentinite,
     and volcanic ash and breccia.

  2.  Parent material. — A qualitative indicator
     of probable shape of  soil particles,  bulk  den-
     sity (or  weight), degree of cohesion or  clay
     mineral content, soil depth, permeability, and
     presence or absence of impermeable layers in
     the soil. These, in turn, suggest types of soil
     mass movement processes operative within an
     area. This information is obtainable from ex-
     isting geologic and soil survey maps, by air
     photo interpretation, and by field check.
       Soils developed from colluvial or residual
     materials and some tills  and  pumice  soils
     commonly  possess  little  or  no  cohesion.
     Failures in such soils are usually of the debris
     avalanche-debris flow type.
       Soils  developed  from  weathered  fine
     grained  sedimentary  rocks  (mudstones,
     claystones,  nonsiliceous sandstones,  shales),
     volcaniclastics, and  glacio-lacustrine  clays
     and silts possess a high degree of cohesion and
     characteristically  develop  failures  of the
     slump-earthflow type.
       The mica content also has a major influence
     on soil  strength. Ten to twenty percent  mica
     will produce results similar to high clay con-
     tent.
  3.  Occurrence of compacted, cemented,  or
     impermeable  layer. — A  qualitative in-
     dicator of the depth of potentially unstable
     soil and probable principal planes of failure
                                             V.19

-------
   on the slope. This information is obtainable
   from borings, soil pits, and inspection of slope
   failure scars in the field.

4. Evidence of concentrated subsurface
   drainage (including evidence of seasonal
   saturation).  — A qualitative indicator  of
   local zones of periodic high soil moisture con-
   tent including saturation and potentially ac-
   tive pore water pressures during high rainfall
   periods.  These  identify potential areas  of
   slope failure. This information is obtainable
   by air photo interpretation and ground obser-
   vation.  Diagnostic features  include  broad
   linear depressions perpendicular to slope con-
   tour,  representing  old  landslide  sites  and
   areas of concentrated  subsurface  drainage,
   and  damp areas on the slope, representing
   springs  and  areas  of  concentrated  ground
   water movement.

5.  Diagnostic soil characteristics. — Key fac-
   tors in determining dominant types  of soil
   mass movement process  mechanics of motion
   and probable  maximum  and minimum stable
   slope  gradients for a particular soil. This is
   identifiable through field  testing,  sampling,
   and laboratory analysis. Data on benchmark
   soils  also may be obtained from soil surveys
   and engineering analyses for road construc-
   tion  in  or  adjacent  to the  proposed
   silvicultural activity.
   a. Soil depth. — Principal component of the
      weight of the soil mass and an important
      factor in  determining  soil  strength and
      gravitational stress acting on an unstable
      soil.
   b. Texture.  — (Particle  size distribution)
      the relative proportions of sand (2.0 - 0.5
      mm), silt (.05 - .002 mm), and clay  (<.002
      mm)  in a soil. Texture, along with clay
      mineral content, are  important factors in
      controlling cohesion,  angle of internal fric-
      tion, and hydraulic conductivity of an un-
      stable soil.
   c. Clay mineralogy. — An indicator of sen-
      sitivity  to  deformation.  Some clays  are
      more  susceptible  to deformation than
      others, making clay mineralogy an impor-
      tant consideration in  areas where creep oc-
      curs.  "Swelling"  clays  of  the  smectite
      group (montmorillonite) are particularly
      unstable.
     d. Angle of internal  friction. —  An  in-
        dicator of the internal frictional resistance
        of a soil caused by intergranular  friction
        and interlocking of individual grains, an
        important factor in determining soil shear
        strength or  resistance  to  gravitational
        stress. The tangent of the angle of internal
        friction times the weight of the soil con-
        stitute a mathematical expression of fric-
        tional resistance. For shallow, cohesionless
        soils, a slope gradient at or above the angle
        of internal friction is a good indicator of a
        highly unstable  site.
     e. Cohesion. — The capacity of soil particles
        to stick or adhere together. This is a  dis-
        tinct soil property produced by cementa-
        tion, capillary tension,  and weak electrical
        bonding of organic colloids and clay parti-
        cles. Cohesion is usually the  direct result
        of high (20 percent or greater)  clay particle
        content and is an important contributor to
        shear strength of a fine grained soil.
C. Bedrock Lithology and Structure
  1.  Rock type. —  A  qualitative indicator of
     overlying soil texture,  clay mineral content,
     and  relative  cohesiveness.  It  provides  a
     regional guide to probable areas of soil mass
     movement problems and dominant processes.
     For example,  in the  Cascades  and  Coast
     Range of Oregon and Washington, areas un-
     derlain by volcanic ash and breccias and silty
     sandstone  are  particularly  susceptible  to
     slump-earthflows.  Where  hard, resistant
     volcanic flow rock is present, shallow planar
     failures  dominate.  Slopes underlain by
     granites and diorites are also more susceptible
     to shallow planar failures, although where ex-
     tensive  chemical weathering  has occurred,
     such  rocks may exhibit  slump-earthflow
     features. The slope stability characteristics of
     a particular rock type or formation largely de-
     pend on mineralogy, climate, and degree of
     weathering, and must be determined for each
     particular area.
  2.  Degree  of  weathering. — A qualitative in-
     dicator  of soil depth  and type of soil mass
     movement activities. In some rock types, it is
     also an indicator of degree of clay mineral for-
     mation.

  3.  Attitude of beds.  — Quantifiable on the
     ground,  from geologic maps, and occasionally
                                             V.20

-------
     from air photos.  This is an  important con-
     tributing factor to unstable slopes, especially
     where attitude of bedding parallels or dips in
     the same direction as the slope. Under these
     conditions, the bedding planes form  zones of
     weakness along which slope failures can occur
     due  to high pore  water pressures and
     decreases in frictional resistance. Conversely,
     bedding planes dipping into the  slope  fre-
     quently produce  natural buttresses  and in-
     crease slope stability. Care must be taken in
     assessing the stabilizing influence of horizon-
     tal or in-dipping bedding planes particularly
     where well-developed jointing is present (see
     no. 4).
  4.  Degree of jointing and fracturing. — Quan-
     tifiable on the ground  and  occasionally from
     geologic maps as dip and strike of faults, frac-
     tures, and joint systems. Joints in particular
     are important contributing factors to slope in-
     stability, especially on slopes underlain by ig-
     neous materials. Joints parallel to or dipping
     in the same direction as the slope, create local
     zones of weakness along which failures occur.
     Jointing also provides avenues for deep
     penetration  of groundwater with subsequent
     active pore water  pressure development along
     downslope dipping joint planes.
       Valleys developed along high angle faults in
     mountainous terrain may have  exceptionally
     steep slopes. Deep  penetration of  ground
     water into uneroded fault and shear zones can
     result in extensive weathering and alteration
     of zone materials, resulting in generation of
     slump-earthflow failures. Such zones  can also
     form  barriers to ground  water movement
     causing redirection  and  concentration  of
     water into adjacent potentially unstable sites.

D. Vegetative Characteristics
  1.  Root distribution  and  degree  of  root
     anchoring in the subsoil. — An indicator of
     effectiveness of tree roots as a stabilizing fac-
     tor in shallow steep slope soils. Quantifiable
     on the ground  by observing the degree of
     penetration of roots through the soil and into
     a more resistant substratum and by  measur-
     ing the biomass of the roots contained in  a
     potentially unstable soil.  High biomass of
     contained roots is  an expression of the binding
     capacity or "reinforcing" effect of roots to the
     soil  mass.
  2.  Vegetation type and distribution. — Cover
     density, vegetation type, and stand age are
     qualitative indicators of the history of soil
     mass movement on a site and soil and ground
     water conditions.  This  information is  ob-
     tainable  by  air  photo  interpretation and
     ground checking.

E. Hydrologic Characteristics
  1.  Hydraulic conductivity. — A measure of
     water movement in and through soil material.
     This is quantifiable in  the field and in the
     laboratory  using  pumping  tests  and
     permeameters.  Low hydraulic conductivities
     mean rapid storm generated saturation and a
     high probability of active pore water pressure,
     which produces highly unstable conditions in
     steep slope soils.
  2.  Pore water pressure. — A  measure of the
     pressure produced  by the head of water in a
     saturated soil and  transferred to the base of
     the soil through the pore water. This is quan-
     tifiable in the field through measurement of
     free water surface level in the  soil. Pore water
     pressure is a  key factor in failure of a steep
     slope soil, and operates primarily by reducing
     the weight component of soil  shear strength.

F. Climate
  1.  Precipitation occurrence and distribution.
     — A key factor in  predicting regional  soil
     mass movement occurrences.  Most soil mass
     movements are triggered by  soil saturation
     and active pore water pressures produced by
     rainfall of high intensity and long duration.
     Isohyetal maps of rainfall occurrences and
     distribution, constructed  from  data ob-
     tainable from local  monitoring stations  or
     from the Weather Bureau, can be used to pin-
     point local areas of high rainfall concentra-
     tion. It is advisable to develop  a simple
     relationship  between  rainfall intensity and
     pore water pressure development for a par-
     ticular  soil type or area of interest so that
     magnitude  and return  period of  damaging
     storms  can be identified. This  can be done
     simply  by locating a rain gage at the site or
     using nearby rainfall data and correlating this
     with piezometric data obtained from  open-
     ended tubes installed to the probable depths
     of failure at the site. Each storm should be
     monitored.
                                               V.21

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                                     THE PROCEDURE
  ESTIMATING SOIL MASS MOVEMENT
         HAZARD AND SEDIMENT
        DELIVERED TO CHANNELS
  This section delineates a procedure to be used on
potentially unstable areas to analyze the hazard of
soil mass movement associated with silvicultural
activities  and to  determine the potential volume
and delivery of inorganic  material  to the closest
drainageway.  This  is  a  broad level  analysis
designed to determine where specific controls or
management  treatment variations  are  required
because of possible water quality changes resulting
from soil mass movement.  This procedure will not
substitute for site specific  analysis of road design,
maintenance, and rehabilitation  as may be  re-
quired under current management procedures.
  To  assess  soil  mass  movement  hazards that
might  deliver inorganic  material  to  a stream
course, a basic qualitative evaluation is undertaken
based on the following information:

  1.  A delineation of hazard areas and dominant
     soil mass movement types using aerial photo
     and  topographic  map  interpretation  with
     minimum ground reconnaissance.
  2.  An  estimate  of the likelihood of failure or
     "sensitivity"  of an  area caused  by  both
     natural  and  man-induced events, using sub-
     jective  analysis  of  controlling  and  con-
     tributing factors within defined hazard  areas.
  3.  An  estimate  of  the  volume  of  material
     released  by   soil  mass movements during
     storm events with a 10-year return  interval or
     less.
  4.  An  estimate of  the  volume  of  sediment
     released by soil mass movements which ac-
     tually reach a water course  based on slope
     position, gradient,  and shape and type of
     movement.

  Although soil mass movements are  too  infre-
quent  for  effective direct annual evaluation,
delivery volumes can be expressed on an average
annual basis  for purposes of comparison  between
pre- and  post-silvicultural  activity conditions.
  A broad delineation of potentially unstable ter-
rain by slope characteristics and soil mass move-
ment  types is an essential part of the hazard
analysis. A detailed flow chart (fig. V.8) shows the
sequence of analysis once the delineation of un-
stable terrain is accomplished.
  The  limits placed on variable ranges for high,
medium  and low hazard indices  are  approxima-
tions based on the collective experience of practic-
ing professionals. The weighted values for hazard
indices are guides only, and they were determined
from consultation with practicing professionals as
well as a limited analysis of several unstable areas
in Colorado and western Oregon. However, they do
reflect  the relative  importance of the individual
factors and their effects on likelihood of failure by
the major  soil mass movement  types. These
weightings and the  ranges of hazard index should
be  adjusted to reflect  the  conditions prevalent
within  a  given area.
       PROCEDURAL DESCRIPTION

   The following information describes each step of
 the procedural flow chart, fig V.8. Data from the
 Horse Creek example are used to illustrate the fol-
 lowing procedure.  This  complete  example  is
 presented in "Chapter VIE: Procedural Example."

          BROAD DELINEATION OF
      POTENTIALLY UNSTABLE AREAS
   Guidelines have been  presented that provide a
 qualitative characterization of'unstable or poten-
 tially unstable slopes on forested lands. Using these
 guidelines,  evaluate  the  area  of  the proposed
 silvicultural activity to  ascertain the stability of
 the site.
        IDENTIFY AND MAP AREAS BY
        SOIL MASS MOVEMENT TYPE
  If the  area is generally unstable or potentially
unstable, delineate the hazard areas and dominant
soil  mass  movement  types  (debris  avalanches-
debris flows and slump-earthflows)  using aerial
photos and topographic map interpretation. Poten-
tially unstable areas are those that may become
unstable due to the proposed silvicultural activity.
Unstable areas are those that have or presently are
undergoing a soil mass movement.
                                              V.22

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               CHARACTERIZE
                 SOIL MASS
              MOVEMENT TYPE
   Soil mass movements have been classified into
 two major types: debris avalanches-debris flows
 and slump-earthflows. Several site parameters and
 management activities can be used to evaluate the
 possibility of soil mass movement. Although both
 movement types have similar factors that can be
 used to evaluate the hazard of a failure, the relative
 importance of  these  factors  may be  different
 between the two movement types. In addition,
 each kind of soil mass movement has some site or
 management activity parameters that are specific
 for  that movement.  Therefore,  to  evaluate  the
 hazard of a soil mass movement, each type must be
 evaluated  separately using the factors  that have
 been found to be significant in characterizing that
 particular  kind  of failure.
             DEBRIS AVALANCHE-
                 DEBRIS FLOW
   Areas prone to debris avalanches-debris flows are
 typified by  shallow, noncohesive soils  on steep
 slopes where subsurface water may be concentrated
 by subtle topography on bedrock or glacial till sur-
 faces.

'           NATURAL HAZARD SITE           ^
              CHARACTERISTICS
   For debris avalanches-debris flows, the following
 site characteristics have been found to be critical in
 evaluating the potential hazard of a natural soil
 mass movement: slope gradient, soil depth, subsur-
 face drainage characteristics, soil texture, bedding
 structure and  orientation, surface slope configura-
 tion, and precipitation input. This information can
 be obtained from geologic and soils maps, pertinent
 literature, field knowledge of local experts, etc. The
 relative importance of each site characteristic is in-
 dicated  in table  V.5 and worksheet V.I by the
 weighting value assigned.
                                                             MANAGEMENT INDUCED
                                                            HAZARD CHARACTERISTICS
  For debris avalanches-debris flows, the following
management activities  have been found  to  be
critical in evaluating the potential hazard for in-
itiation or acceleration of a soil mass movement:
vegetative cover removal, roads and skidways, and
harvest systems. This information can be obtained
from past records  of silvicultural activities or from
proposed silvicultural activity plans. The relative
importance  of  each management  activity  is in-
dicated  in  table  V.6 and worksheet V.2 by the
weighting value assigned.
               HAZARD INDEX
  The  hazard  index  analysis  procedure  places
weighted values on the factors affecting different
types of soil mass movement. A three-part hazard
index  is  used:  high,  medium,  and  low.  The
numerical ratings  are subjective and depend on
what is  considered acceptable for a  particular
silvicultural activity. Assumptions  1 and 2 in the
procedure detail and define a high, medium, and
low hazard.
  The natural hazard index for debris avalanches-
debris  flows is determined  by  summing  the
weighted values from worksheet V.I  and comparing
this value to the ranges of values for high, medium,
and low hazard  indices. For example, if the sum of
the weighted values for the natural hazard index
(worksheet V.I) was 31, the hazard index would be
medium. The value 31 falls within the range of
values  (21-44) for the medium  hazard.
  The relative hazard for debris avalanches-debris
flows caused by silvicultural activities is deter-
mined  by  summing the  weighted values from
worksheet V.2. The overall hazard index caused by
natural plus existing or proposed silvicultural ac-
tivities is determined by adding the total weighted
value for the natural hazard. This overall weighted
value is compared with the range of values given for
a high, medium, or low hazard index. For example,
if  the  silvicultural activities resulted  in a total
weighted value of 31, the overall weighted value of
both the natural (31) plus the silvicultural activity
(31) would be equal to 62 and the overall hazard in-
dex would be high.
                                              V.23

-------
                  BROAD DELINEATION OF POTENTIALLY
                          UNSTABLE AREAS
            c
IDENTIFY AND MAP AREAS BY
SOIL MASS MOVEMENT TYPE

CHA
/ Cf
DEBRIS AVALANCHE ^ /MOV
DEBRIS FLOW
,
,
HAZARD
INDEX


4
^



^

NATURAL HAZARD
SITE
CHARACTERISTICS
SLOPE GRADIENT
SOIL DEPTH
SUBSURFACE
DRAINAGE
CHARACTERISTICS
SOIL TEXTURE
BEDDING STRUCTURE
AND ORIENTATION
SURFACE SLOPE
CONFIGURATION
PRECIPITATION INPUT

' MANAGEMENT \
INDUCED HAZARD
CHARACTERISTICS
VEGETATIVE
COVER REMOVAL
ROADS AND SKIDWAYS
i HARVEST SYSTEMS /

RACTERIZE
DILMASS \
EMENTTYPE X ^

w

SLUMP-EARTHFLOW

NATURAL HAZARD \
SITE
CHARACTERISTICS
SLOPE GRADIENT
VEGETATIVE
INDICATORS
SUBSURFACE
DRAINAGE
CHARACTERISTICS
SOIL TEXTURE
BEDDING STRUCTURE
AND ORIENTATION
SURFACE SLOPE
CONFIGURATION
PRECIPITATION INPUT

' MANAGEMENT
INDUCED HAZARD
CHARACTERISTICS
VEGETATIVE
COVER REMOVAL
ROADS AND SKIDWA'l
i HARVEST SYSTEMS

\
rs
/




r+
i

HAZARD
INDEX


                 FOR THE TWO SOIL MASS MOVEMENTTYPES,
            EVALUATE NATURAL VS. MAN INDUCED MASS MOVEMENT
SITE OF PROPOSED
 SILVICULTURAL
ACTIVITY HISTORY
        HISTORY
          PAST
     SILVICULTURAL
       ACTIVITIES
 SITE OF PAST
SILVICULTURAL
   ACTIVITY
*
ESTIMATE TOTAL
AND AVERAGE
VOLUME PER SOIL
MASS MOVEMENT



/ VOLUME OF EACH FAILURE \
LENGTH
WIDTH
DEPTH
NUMBER OF FAILURES BY
MOVEMENT TYPE AND CAUSE
t 1
fe.

*
ESTIMATE TOTAL
AND AVERAGE
VOLUME PER SOIL
MASS MOVEMENT
1
                                V.24

-------
        TOTAL
  VOLUME RELEASED
  BY SLOPE CLASS OR
  POSITION CATEGORY
         I
COMPUTE TOTAL WEIGHT
 RELEASED PER SLOPE
 CLASS OR CATEGORY
     NUMBER OF SOIL MASS
   MOVEMENTS BY SLOPE CLASS
   ,  OR POSITION CATEGORY  ,
   ESTIMATED DRY UNIT WEIGHT
   OF SOIL IN MASS MOVEMENT
       TOTAL
  VOLUME RELEASED
  BY SLOPE CLASS OR
  POSITION CATEGORY
COMPUTE TOTAL WEIGHT
 RELEASED PER SLOPE
 CLASS OR CATEGORY
      ESTIMATE
      DELIVERY
      POTENTIAL
/SLOPE IRREGULARITY BY SLOPE \
\ CLASS OR POSITION CATEGORY /
fc
V
ESTIMATE
DELIVERY
POTENTIAL
            ESTIMATE
      TOTAL QUANTITY OF SOIL
    DELIVERED PER SLOPE CLASS
      OR POSITION CATEGORY
        AND TOTAL AMOUNT
                                ESTIMATE
                         TOTAL QUANTITY OF SOIL
                        DELIVERED PER SLOPE CLASS
                          OR POSITION CATEGORY
                           AND TOTAL AMOUNT
                                                        I
                                              ESTIMATE AN ACCELERATION
                                             FACTOR TO ACCOUNT FOR THE
                                                 INCREASED DELIVERY
                                              DUE TO THE SILVICULTURAL
                                                ACTIVITY (MAN-INDUCED)
                          1
                                                         J
                          ESTIMATE INCREASED SOIL
                            DELIVERY DUE TO THE
                          PROPOSED SILVICULTURAL
                                 ACTIVITY
               Figure V.8.—Detailed flow chart of the soli mass movement procedure.
                                   V.25

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   Table V.5.—Weighting factors for determination of natural hazard of debris avalanche-debris flow failures
Factor
Slope gradient




Hazard index and range
High
>34°
Medium
29° -34°
Low
<29°
Weight
30
15

5

Soil depth
Subsurface drainage
  characteristics
Soil texture
 Bedding structure
   and orientation
High
  Shallow soils, <5ft
Medium
  Moderately deep soils, 5-10 ft
Low
  Deep soils, >10ft

High
  High density, closely spaced incipient drainage depressions
  Presence of bedrock or  impervious material at shallow depth which
  restricts vertical water movement and concentrates subsurface flow
  Presence of permeable low density zones above the restricting layer
  indicative of saturated flow parallel to the slope
  Evidence  of springs on the slope
Medium
  Presence of incipient drainage depressions, but widely spaced
  Presence of impervious material at shallow depths, but no low density
  zones present
  Springs are absent

Low
  Incipient drainage depressions rare to absent
  No shallow restricting layers present
  No indications of  near-surface flow

High
  Unconsolidated, non-cohesive soils and  colluvial  debris  including
  sands and gravels, rock  fragments, weathered granites, pumice and
  noncompacted  glacial tills with low silt content (<10%) and no clay
Medium
  Unconsolidated, non-cohesive soils and colluvial debris with  moderate
  silt content (10-20%) and minor clay (<10%)
Low
  Fine grained, cohesive soils with greater than 20% clay sized particles
  or mica

 High
   Extensive jointing and fracturing parallel  to the  slope
   Bedding  planes parallel  to the slope
   Faulting or shearing parallel to the slope (the stability influence of bed-
   ding planes horizontal or dipping into the slope  is offset by extensive
   parallel jointing and fracturing)
 Medium
   Bedding  planes are horizontal or dipping into the slope with minor
   jointing at angles less than the natural slope gradient
   Minor surface fracturing — no faulting or shearing evident
 Low
   Bedding  planes are horizontal or  dipping into the slope
   Jointing and fracturing is minor — no faulting or shearing evident
3

2

1
                                                  V.26

-------
                 Table V.5.—Weighting factors for determination of natural hazard of debris
                                avalanche-debris flow failures — continued
Factor
Hazard index and range
Weight
Surface slope
  configuration
Precipitation input
High
  Smooth, continuous slopes unbroken by benches or rock outcrops
  Intermittent steep channels occur frequently with lateral spacing of 500
  ft (152 m) or less
  Perennial channels frequently deeply incised with steep walls of rock
  or colluvial debris
  Numerous breaks in canopy due to blow-downs — frequent linear or
  tear-drop shaped  even-age stands  beginning at small scarps or
  spoon-shaped depressions indicative of old debris avalanche-debris
  flow activity
Medium
  Smooth, continuous slopes broken by occasional benches and rock
  outcrops
  Intermittent, steep gradient channels occur  less frequently with a
  lateral spacing of 500-800 ft (152-244 m)
  Infrequent evidence of blow-down or past landslide activity
Low
  Slope  broken by  rock benches and  outcrops intermittent, steep
  gradient channels spaced 900 ft (275 m)  or more apart

High
  Area characterized by rainfall greater than 80 in/yr (203 cm/yr) dis-
  tributed throughout the year or greater than 40 in/yr (102 cm/yr) dis-
  tributed over a clearly definable rainy season
  Locale  is subjected to frequent high intensity  storms capable of
  generating saturated  soil conditions  on the slope leading to active
  pore-water pressure development and high stream flow — area has a
  high potential for  mid-winter  or early spring rainfall-on-snowpack
  events
  Storm intensities may exceed 6 in/24 hr at 10 yr recurrence intervals or
  less
Medium
  Area characterized by moderate rainfall of 20 to 40 in/yr (51 to 102
  cm/yr)
  Storms of moderate intensity and duration are common
  High intensity storms  are infrequent,  but do occasionally occur
  Moderate snowpack, but rain-on-snow events very rare
  Storm intensities may exceed 6 in/24 hr (15 cm/24 hr) at recurrence in-
  tervals greater than 10 yrs.
Low
  Rainfall in area is low (less than 20 in/yr)
  Storms infrequent and of low intensity
  Stored water content in snowpack, when present, is low and only rarely
  subject to rapid  melting
                                                                                                  12
                                                 V.27

-------
                                                     WORKSHEET  V.1



                              Debris avalanche-debri?  flow  natural  factor  evaluation  form

Index
High
vied ium
.ow

Slope
gradient
30
0
5

Soi 1
depth
3
(D
1

Subsurface
drainage
character i sties
G
2
1

Soi 1
texture
3
©
C
Bedd i nq
structure
and
or ientat ion
3
©
1

Slope
conf igurat ion
3
(P
1

Preci p i -
tat ion
input
12
©
3
to
oo
                                                Factor  summation  table
Gross hazard index
High
Medium
Low
Factor ranae
Greater than 44
21 - 44
Less than 21
Natural

31


-------
   Table V.6.—Weighting factors for determination of management-induced  hazard of debris avalanche-debris
                                               flow failures
Factor
                          Hazard index and range
                                                                        Weight
Vegetation cover
  removal
Roads and
  skidways
Harvest systems
High                                                                      8
   Total removal of cover — large clearcuts with openings continuous
   downslope — such removal is sufficient to increase soil moisture levels
   and reduce strength
   Broadcast burning of slash
Medium                                                                  5
   Cover partially removed with slope sections >34° left undisturbed —
   clearcuts in small patches or strips less than 20 ac (8 ha) and discon-
   tinuous on slopes
Low                                                                      2
   Cover density altered through partial cutting — no clearcutting — no
   broadcast burning of sites with >34°  slope

High                                                                      20
   High density (>15% of area in roads) on potentially unstable slopes
   (>28°) — cut and fill construction
   Roads and skidways located on steep, unstable portions of the slope
   Uncontrolled fills with poor compaction produced by side-casting over
   organic debris
   Inadequate cross  drainage (poor location; improper  spacing and
   maintenance, size  too small'for 10 yr storm flow)
   Lack of fill slope protection of drainage outlets
   Concentrations of  drainage water directed  into identifiable unstable
   areas
Medium
   Mixed road types, both fully benched and  cut-and-fill (balanced) —
   moderate road density (8-15% of area)
   Areas with slopes >34° or with identifiable landslide activity have been
   avoided or fully benched
   On potentially unstable slopes  >29° skidways and  cut-and-fill type
   construction  are limited
   Ridgetop  roads have large fills in saddles
   Fills,  where  present, are constructed  by sidecasting over organic
   debris with little controlled compaction
   Roads generally have adequate cross drains for normal runoff condi-
   tions (number and location) but are undersized for the 10 yr storm flow
   Fill slopes below culvert outfalls protected by rip-rap dissipation struc-
   tures at potentially unstable sites
   Major concentrations of water into identifiable unstable areas avoided
Low
   Very few roads on slopes above 28° — low road density (less than 8%
   of area) with roads on potentially unstable terrain (slopes between 29°
   and 34°) predominantly of full  bench type — most road locations or
   construction  limited  to ridgetops with minimum fills in  saddles and
   lower slopes  — adequate  cross drains with  major water courses
   bridged and  culverts designed for 10 yr storm  flow or larger

High
   Operation of tractor  yarding, jammer yarding and other ground lead
   systems on slopes >29°  (53%)
Medium
   No tractor logging — high lead with partial suspension on slopes >29°
   (53%)
Low
   Helicopter and balloon yarding —  full  suspension  of logs by any
   method — yarding by any method on slopes <29° (53%)
                                                 V.29

-------
                                 WORKSHEET V.2
                    Debris avalanche-debris flow management
                        related factor evaluation form
1 ndex
High
Medium
_ow
Vegetation
cover remova 1
<Ł>
5
2
Roads and
skidways
<§)
8
2
Harvest
methods

2
0
                            Factor summation table
Gross hazard index
Range
Natural +
management
High

Medium

_ow
Greater than 44

21 - 44

Less than 21
                                      V.30

-------
             SLUMP-EARTH FLOW
                                                                  HAZARD INDEX
   Slump-earthflow  prone areas are typified  by
 deep, cohesive soils and clay-rich bedrock overlying
 hard, competent rock. Slump-earthflow soil mass
 movement also appears to be sensitive to long-term
 fluctuations.

           NATURAL HAZARD SITE
              CHARACTERISTICS

   For slump-earthflows,  the  following site
 characteristics have been found to be critical in
 evaluating the potential hazard of a natural soil
 mass  movement:  slope gradient, sub-surface
 drainage characteristics, soil texture, surface slope
 configuration, vegetative indicators, bedding struc-
 ture and orientation, and precipitation input. This
 information  can  be obtained  from soils  maps,
 vegetative cover maps,  pertinent literature, field
 knowledge of local experts, etc. The relative impor-
 tance  of each site  characteristic is indicated in
 table V.7 and worksheet V.3 by the weighting value
 assigned.

           MANAGEMENT INDUCED
         HAZARD CHARACTERISTICS

  The hazard  index analysis  procedure places
weighted values on the factors affecting different
types of soil mass movement. A three-part hazard
index  is  used:  high,  medium,  and  low.  The
numerical ratings  are subjective and depend on
what is  considered  acceptable for a  particular
silvicultural activity. Assumptions  1 and  2 in the
procedure detail and define a high, medium, and
low hazard.
  The natural hazard index for slump-earthflows is
determined by summing the weighted values from
worksheet V.3 and comparing this value to  the
ranges of values for high, medium, and low hazard
index. For example, if the sum of the weighted
values for the natural hazard index (wksht. V.3)
was 38, the hazard index would be medium.  The
value 38 falls within the range of values (22-44) for
the medium hazard.
  The relative hazard for slump-earthflows caused
by silvicultural activities is  determined by sum-
ming the weighted values from worksheet V.4. The
overall hazard index resulting from natural plus ex-
isting or  proposed  silvicultural activities is deter-
mined by adding the total weighted value from
silvicultural activities to the total weighted value
for the natural hazard. This overall weighted value
is compared with the range of values given for a
high, medium, or low hazard index. For example, if
the silvicultural  activities resulted  in  a  total
weighted value of 8, the overall weighted value of
both the natural (38) plus the silvicultural activity
(8) would be equal  to 46, and the overall hazard in-
dex would be high.
  For  slump-earthflows, the  following manage-
ment activities have been found to be critical in
evaluating the potential hazard for initiation or ac-
celeration of a soil  mass movement:  vegetative
cover removal, roads and skidways, and harvest
systems. This information can be  obtained from
past records of silvicultural  activities or from
proposed silvicultural activity  plans. The relative
importance  of each  management  activity  is in-
dicated in table V.8 and worksheet V.4 by the
weighting value assigned.
          FOR THE TWO TYPES OF
          SOIL MASS MOVEMENTS,
   EVALUATE NATURAL VS. MAN-INDUCED
              MASS MOVEMENT
  Determine the quantity of material delivered to a
stream channel for each soil mass movement type
and evaluate any man-induced increase in mass
movement over that naturally occurring.
                                              V.31

-------
          Table V.7.—Weighting factors for determination of natural hazard of slump-earthflow failures
Factor
Hazard index and range
Weight
Slope gradient
Subsurface drainage
  characteristics
Soil texture
Slope configuration
High                                                                   6
  greater than 30° (58%)
Medium                                                                4
  15-30°(27%-58%)
Low                                                                   2
  under 15° (27%)

High                                                                   6
  Area exhibits abundant evidence of impaired groundwater movement
  resulting in local zones of saturation within the soil mass — short, ir-
  regular surface drainages which begin and end on the slope
  Impaired drainage, indicated at the surface by numerous sag ponds
  with standing water, springs and  patches of wet ground
  Impaired drainage involves more than 20% of the area
Medium                                                                4
  Some indications of impaired drainage, but generally involving less
  than 10% of the area
  Active springs are uncommon, infrequent, or  contain no  standing
  water
Low                                                                   2
  No evidence of impaired drainage

High                                                                  15
  Predominantly fine grained cohesive soils derived from weathered
  sedimentary rocks,  volcanics,   aeolian  and  alluvial silts  and
  glaciolacustrine silts and clays
  Clay sized particle content generally greater than 20%
  Clay minerals predominantly of the smectite group (montmorillonite),
  exhibiting swelling characteristics upon wetting
Medium                                                               10
  Soils of variable texture including both fine and coarse grained compo-
  nents in layers and lenses
  The fine grained, cohesive component may contain a clay sized parti-
  cle content greater than 20%,  but clay minerals  are predominantly of
  the illite and kaolinite groups, exhibiting lower sensitivity to changes in
  stress
Low                                                                   5
  Soils of variable texture
  Some clayey soils present but widely dispersed in small layers or
  lenses

High                                                                   5
  40% or more of the area is characterized  by hummocky topography
  consisting of rolling, bumpy ground, frequent benches and depres-
  sions locally enclosing sag ponds
  Tension  cracks  and  headwall scarps indicating slumping are  un-
  vegetated and clearly visible
  Slopes are irregular and may be slightly concave in the upper 1/2 and
  convex in the lower 1/2 as a result of the downslope redistribution of
  soil materials
  Zones of active movement are abundant
Medium                                                                2
  5% to 40% of the area is characterized by hummocky topography
  Occasional sag ponds occur, but slump depressions are generally dry
  Headwall scarps are revegetated and no open tension cracks are visi-
  ble
  Active slump-earthflow features are absent
                                                 V.32

-------
       Table V.7.—Weighting factors for determination of natrual hazard of slump-earthflow — continued
Factor
Hazard index and range
Weight
Vegetative
  indicators
Precipitation
  input
Low
  Less than 5% of the area is characterized by hummocky topography
  Old slump-earthflow features are absent or subdued by weathering
  and erosion
  No active slump earthflow features present, slopes are generally
  smooth and continuous from ridge to valley floor

High
  Phreatophytic (wet site) vegetation widespread
  Tipped (jackstrawed) and split trees  are common
  Pistol-butted trees occur in areas of  obvious hummocky topography
  (note: pistol-butted trees should be used as indicators of active slump-
  earthflow activity only  in the presence of other indicators — pistol-
  butting can also occur in areas of high snowfall and is often the result
  of snow creep and glide)
Medium
  Phreatophytic vegetation limited to occasional moist areas on the open
  slope and within sag ponds
  Tipped trees absent
Low
  Phreatophytic vegetation absent

High
  Area characterized by high rainfall of greater than 80 in/yr (203 cm/yr)
  distributed throughout  the year or greater than 40 in/yr (102 cm/yr)
  distributed over a clearly definable rainy  season
  Locale is subjected to  frequent  high intensity, long  duration storms
  capable of generating continuing saturated conditions within the soil
  mass leading to active pore water pressure development and mobiliza-
  tion of the clay fraction
  Area has a high potential for rain-on-snow events
Medium
  Area characterized by moderate rainfall of 20 to 40 in/yr (51  cm/yr to
  102 cm/yr)
  Storms of moderate  intensity and duration  are common
  Snowpack is moderate, but rain-on-snow events are rare
Low
  Rainfall in the area is low (less than 20 in/yr) storms are infrequent and
  of low  intensity and duration
  Stored water content in the snowpack, when present, is low throughout
  the winter with no mid-winter or  early  spring  releases  due  to
  climatological events
                                                                                                   1
  0


 18
                                                                                                 10
                                                V.33

-------
                 WORKSHEET V.3




SIump-earthflow natural  factor evaluation form

1 ndex
High
Medium
Low

Slope
grad ient
©
4
2
Subsurface
drainage
characteristics
6
(Ł>
2

Soil
texture
15
©
5

Slope
conf igurat ion
©
2
1

Vegetat i ve
i nd icators
5
©
0

Preci p i tat ion
input
18
(To)
2
            Factor summation table
Gross hazard index
High
Medium
Low
Range
Greater than 44
21 - 44
Less than 21
Natural

2,8


-------
   Table V.8.—Weighting factors for determination of management induced hazard of slump-earthflow failures
Factor
Hazard index and range
Weight
Vegetation
  cover removal
Roads and
  skidways
Harvest systems
High                                                                    3
  Total removal of cover or large clearcuts with openings continuous
  downslope —  such removal  would be  sufficient to increase soil
  moisture levels and reduce root strength
Medium                                                                 2
  Cover  partially  removed — clearcuts in small patches or strips less
  than 20 acres (8 ha) is size and discontinuous downslope
Low                                                                    1
  Cover  density altered through  partial cutting, no clearcutting evident

High                                                                    7
  High density (>15% of area in roads) cut-and-fill type (balanced) con-
  struction
  Roads and skidways located or planned across identifiable unstable
  ground
  Roads crossing active or dormant slump-earthflow features
  Massive fills or spoil piles on slump benches
  Inadequate drainage creating concentrations of water at the surface
  with diversion of surface drainage into  unstable areas
Medium                                                                 4
  Mixed  road types, both fully benched and cut-and-fill (balanced) —
  moderate road  density (8-15% of  area  in roads),  unstable areas
  features avoided
  Roads generally have adequate cross drains for normal runoff condi-
  tions but are  undersized for 10 yr storm flows
  Diversions of concentrations of water into unstable sites avoided
Low                                                                    2
  No  roads present — if present, predominantly fully benched
  Road density less than 8%
  Most road location and construction on ridgetops or  in alluvial valley
  floors
  Adequate cross drainage with dispersal  rather than heavily  con-
  centrated surface flow

High                                                                    3
  Operation of  tractor yarding, jammer yarding or other ground lead
  systems causing excessive ground disturbance
Medium                                                                 2
  High lead yarding with  partial suspension and skyline with partial
  suspension
  No tractor yarding
Low                                                                    1
  Helicopter and balloon yarding
  Full suspension of logs by any method
                                                 V.35

-------
                                 WORKSHEET V.4
                          SIump-earthflow management
                        related factor evaluation  form
Index
High
Medium
Low
Vegetation
cover remova 1
©
2
1
Roads and
skidways
7
4


-------
     HISTORY OF PAST SILVICULTURAL
           /    ACTIVITIES   \
  To  estimate the man-induced increase in the
amount of soil  delivered to a  stream  channel
caused by silvicultural activities, it is necessary to
compare soil mass movement in an area that has
not been subjected to silvicultural activities with
soil mass movement in an area that has been sub-
jected to silvicultural activities. It is essential that
the area selected for its previous silvicultural ac-
tivities  be identical  or very similar  to  the  un-
disturbed area, not only in physical site conditions,
but also in proposed silvicultural activities. The
proposed site of the silvicultural activity may or
may not have existing soil mass movement which
could  be measured and quantified. The other area
should have a  history, if possible, of soil mass
movements from both natural  and man-induced
causes.
       VOLUME OF EACH FAILURE AND
          NUMBER OF FAILURES BY
          MOVEMENT TYPE & CAUSE
  The site is inventoried using aerial photos and
possibly a limited field reconnaissance and a record
is made of each soil mass movement (the length,
width, and depth), (figs. V.9 and V.10). The cause
of each mass movement, either natural or in the
case of areas  that have been subjected  to past
silvicultural activity, man-induced, and the type of
mass movement  are noted. The number of soil
mass movements by  cause (natural  vs.  man-
induced) and type is computed.
             SITE OF PROPOSED
          SILVICULTURAL ACTIVITY
        ESTIMATE TOTAL & AVERAGE
    VOLUME PER SOIL MASS MOVEMENT
  If the proposed silvicultural activity is to be con-
ducted in a previously undisturbed  area, the in-
herent natural instability of the site can be es-
timated  based  upon  existing failures or upon
failures occurring on a similarly undisturbed site.
        SITE OF PAST SILVICULTURAL
                  ACTIVITY
  Select an area adjacent to the proposed site of
the  silvicultural  activity,  with similar  site
characteristics and a history of similar silvicultural
activities. The inherent natural instability of the
area can be estimated based upon existing failures.
Failures caused or accelerated by the silvicultural
activity can also be measured.
  The volume of individual soil mass movements
(V) is computed on worksheet V.5 by multiplying
the length (L), width (W), and depth (D) to obtain
cubic feet of soil moved. The total soil mass move-
ment by type (debris avalanche-debris flow and
slump-earthflow)  is computed by summing the
volumes  of the individual failures (wksht.  V.5).
These  values  are  summed  and recorded  on
worksheet V.6, step 1. The total  number (N) of
failures by soil mass movement type is recorded on
worksheet V.6, step 2. The average volume per soil
mass movement  (VA)  by  movement  type is
computed by dividing the total volume (Vt) by the
number of failures (N) or VA  = Vt/N and is recorded
on worksheet V.6, step 3. For example, if the total
volume (Vt) for debris avalanches-debris flows was
17,205  ft3 (487 m3)  and the  number of debris
avalanche-debris  flow  (N)  was 5, the  average
volume per debris avalanche-debris flow (VA) would
equal 3,441 ft3 (162 m3) or VA =  17,205 ft3/5 = 3,441
ft3.
                                             V.37

-------
Figure V.9.—Dimensions of debris avalanche-debris flow failures for determining potential volumes. W
  width; L = length; D = depth.
  Figure V.10—Dimensions of slump-earthflow failures for determining potential volumes. W = width; L
    length; D = depth.
                                              V.38

-------
                                                            WORKSHEET  V.5


                                                 Estimation of  volume per  failure
CO
ID

SI ide
Number
4erse
/

Wale
/
Z
3
V
S"

/



Debris avalanche-debr s flow
Natural
Creek
X

Ct-eek






X



Man-
induced




X
X
X
X
X





Length
(ft)

SĄ


so
u?
Ul
113
7s-

IIS



Width
(ft)

48


*1
^
17
19
53

19



Depth
(ft)

AS"


AS"
AST
AST
AS"
AS"

/.s



Vol ume
(ft3)

3,sra*


3,580
S-,031
3,0«G
3,041
3,a7X

3,3*0



Slump earthflow
Natural














Man-
induced














Length
(ft)














Width
(ft)














Depth
(ft)














Vo 1 ume
(ft3)















-------
                                           WORKSHEET  V.6

                  Estimation of soil mass movement  delivered to the stream channel
(1)   Watershed name
                      Male
               Factor
                 (2)
                                                               Soi 1  mass movement type
                                                 Debris avalanche-
                                                 Debris flow
                                                  Natura 1
                                                    (3)
                                                          Man-induced
                                                              (4)
                      Slump flow
                 Natural
                   (5)
Man-inducec
    (6)
1   Total  volume  (Vt)  in ft
                                                 saso
17^05
2  Total  number  of  failures (N)
3  Average volume  per failure (VAMft
4  Number of  failures per slope
   cl ass
5  Number of  failures per slope
   position category
                                       b1
                                       d1
6  Total  volume  per slope class or
   position  category
          (V)  in  ft5
     V = VA x  N
                                                 3^80

7  Unit weight of dry soil
   material  (Yd)  (Ib/ft3)
                                               V.40

-------
WORKSHEET V.6—continued
B Total weight per slope class
or position category (W)
in tons
~ 2,00(5
Wa
Wa'
Wb
Wbi
We
Wc,
wd,
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S = W x D
Da
Da-
Db
°b'
DC
DC-
Dd'
sa
Sa-
sb
sb-
t
Sdi
12 Total quantity of sediment delivered to
the stream channel in tons
3 Acceleration factor (f)
f = Tssilvicultural actlvlty/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed sllvi-
cultural activity (TS) In tons
Tssilvlcultural activity = TSnatural x f
/fc3
—
—
/
smooth
O.tl
—
—
/
lol
—
—
/
lol
CK
3
-------
    NUMBER OF SOIL MASS MOVEMENTS
             BY SLOPE CLASS OR
             POSITION CATEGORY
   The soil mass movement recorded previously by
 type and cause must be differentiated  by slope
 class or category. Debris avalanches-debris flows
 are  differentiated by slope class which  is based
 upon slope steepness. There are three classes: a is
 greater than 35° (70%),  b is less than 35° (70%),
 and greater than 28° (53%), and c is less  than 28°
 (53rc).  Slump-earthflows  are  differentiated  by
 position on  the slope.  There  are  four  position
 categories: a' is adjacent to the stream,  b' is the
 lower 1/3 of  the slope, c' is the middle 1/3 of the
 slope, and d' is the upper 1/3 of the  slope. This in-
 formation is  recorded on worksheet  V.6, step 4 for
 slope  classes  and  step  5 for slope  position
 categories.
        TOTAL VOLUME RELEASED BY
   SLOPE CLASS OR POSITION CATEGORY
  For both the proposed silvicultural activity area
 and the area previously subjected to a silvicultural
 activity, the total volume of soil mass movement
 (Vt)  by type and slope class (a,b,c) or position
 category (a',b',c',d')  is computed. The average
 volume  per  failure (VA)  is  multiplied by the
 number  of failures in each slope class  (a,b,c) or
 position  category  (a',b',c',d')  and  recorded  on
 worksheet V.6,  step 6. For example, if the average
 volume per failure (VA) was equal to 3,441 ft3 (162
 m3)  and there  were two debris avalanches-debris
 flows in  the 28°  to 35° slope class (b), the total
 volume for that soil mass movement type and slope
 class (b) would equal 6,882 ft3 (324 m3) or 3,441 ft3
 X 2 = 6,882 ft3.
sessed area  for  this  determination  if  possible.
Otherwise, use the values for typical soils provided
in table V.9. For example, the soil was measured,
the dry unit weight was 99 lb/ft3 (1.57 g/cm3). The
dry unit weight  of soil material  is recorded on
worksheet V.6, step 7.

  Table V.9—Unit weight of typical soils in the natural state
                  (Terzaghi 1953)
Unit weight
Description
Uniform sand, loose
Uniform sand, dense
Mixed-grained sand, loose
Mixed-grained sand, dense
Glacial till
V
lb/ft3
90
109
99
116
132
Td
g/cm3
1.43
1.75
1.59
1.86
2.12
      = unit weight in dry state.
                                                       COMPUTE TOTAL WEIGHT RELEASED
                                                         PER SLOPE CLASS OR CATEGORY
  Estimate the  total  weight of  material  (W)
released  per slope  class  (a,b,c)  or  category
(a',b',c',d'). For the previously disturbed site (that
area subjected to a past silvicultural activity), dif-
ferentiate between natural  and  man-induced
failures. For example, if the dry unit weight was 99
lb/ft3 and the total  volume  released by debris
avalanche-debris flow with a slope class  of 28° to
35° was 6,882 ft3, the total weight released for this
slope class would be 681,318 Ib or 6,882 ft3 X 99
lb/ft3 = 681,318 Ib. This is converted to tons by
dividing by 2,000 Ib/ton or 681,318 Ib divided by
2,000 Ib/ton  = 341  tons (309 metric tons). These
values are recorded on  worksheet V.6, step 8, by
slope class (a,b,c) or position category (a',b',c',d'),
type of  mass movement, and for the previously dis-
turbed  site, natural vs.  man-induced  failures.
            ESTIMATED DRY UNIT
     WEIGHT OF SOIL MASS MOVEMENT
          SLOPE IRREGULARITY BY
   SLOPE CLASS OR POSITION CATEGORY
  Estimate the dry unit weight (7d) of the soil
materials included in the failures (V), expressed in
pounds/cubic foot. Use soil samples from the as
  Estimate,  by slope class (a,b,c)  or  position
category (a',b',c',d'), the gross irregularity of the
slope within the area of the proposed silvicultural
                                              V.42

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activity and the area of the past silvicultural ac-
tivity. Two general classifications are used: smooth
and irregular. Smooth slopes generally have a uni-
form profile with a few major breaks or benches
which  may  serve  to  trap  and collect  soil  mass
movement material.  Incipient drainage  depres-
sions and intermittent drainages  have a constant
grade and lead directly to main drainage channels.
Irregular slopes generally have an uneven profile
with frequent benching or  breaks, which tend to
trap and collect soil mass movement material. In-
cipient  drainage  depressions  and  intermittent
drainageways have an uneven grade with frequent
grade flattening and changes in direction. The clas-
sification is  recorded on worksheet V.6,  step 9.
       ESTIMATE DELIVERY POTENTIAL
  Determine the percentage of soil mass movement
material delivered (D) to the stream channel. An
estimated  delivery relationship  is  presented  in
figure V.ll, for debris avalanches-debris flows, and
is  based  upon  the slope class (a,b,c)  and  ir-
regularity. An estimated delivery relationship is
presented in figure V.12  for slump-earthflows and
is  based  upon  the  slope position category
(a',b',c',d'). Delivery in  percent,  is  recorded  on
worksheet V.6, step 10. For example, the  delivery
potential of a debris avalanche-debris flow  on a
smooth 29° (55%) slope is 30%.
                                            I       I        I
                                           20     25    28 30
                                           DEGREES
                 35
 I
40
 I
45
             Figure V.11—Delivery potential of debris avalanche-debris flow material to closest stream.
                                               V.43

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            g
            H
            CO
            LU
            CL
            O
            _l
            co
                  Ridgetop
                d' upper 1/3 —
               c' middle Vz —
                 b' lower 1/3 —i
         a' Stream adjacent
           slope
                                                                          80   90  100
                                               PERCENT DELIVERY
                  Figure V.12—Delivery potential of slump-earthflow material to closest stream.
    ESTIMATE TOTAL QUANTITY OF SOIL
DELIVERED PER SLOPE CLASS OR POSITION
      CATEGORY AND TOTAL AMOUNT
  Determine the estimated quantity of soil mass
movement material delivered to the stream chan-
nel (S) for each slope  class (a,b,c) or position
category (a',b',c',d'). For the area subjected to the
past silvicultural activity,  separate by natural vs.
man-induced. The quantity of soil mass movement
material delivered to a stream (S) is computed by
multiplying the estimated  total weight of released
soil material (W) by the delivery potential (D) ex-
pressed as a decimal percent. This should be done
for each slope class or position category. For exam-
ple,  if the  total  weight  of a released  debris
avalanche-debris flow  with a slope class  of 28° to
35° class(6) was 341 tons,  and the delivery poten-
tial  was  30  percent,  the  amount of  material
delivered to a stream channel would be 102 tons or
 341 tons X  0.3 decimal percent. These values are
 recorded in  worksheet V.6, step 11. The total quan-
tity of soil mass movement material (TS) delivered
 to the stream channel is computed by summing the
 material delivered by each slope class (a,b,c) or
 position category  (a',b',c',d'). The  total quantity
 delivered is  recorded on worksheet V.6, step 12. For
 example, if the  slope classes (a,b,c) for debris
 avalanche-debris flow had the following values: Sa
 = 171 tons, Sb =  102  tons,  and Sc = 26 tons, the
 total quantity of material delivered to the stream
 channel by  debris avalanche-debris  flows would be
 equal to 299 tons. If slump-earthflows were present
 or possible,  these values (a',b',c',d') would also be
 summed and added to the debris avalanche-debris
 flow value  to get the quantity  of total sediment
 delivered to the stream (TS).
  The  computation provides an estimate of the
 average total volume of material delivered to the
 stream channel  (TS)  in the area of proposed
 silvicultural activities  under natural conditions
 and can be used  directly in "Chapter VI: Total
 Potential Sediment."
                                             V.44

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        ESTIMATE AN ACCELERATION
       FACTOR TO ACCOUNT FOR THE
        INCREASED DELIVERY DUE TO
        THE SILVICULTURAL ACTIVITY
              (MAN-INDUCED)
  Estimate the change in sediment delivery to the
stream channel on the previously disturbed area as
a result of all silvicultural activities by comparing
quantities and delivery rates for both natural and
man-induced failures. The acceleration factor (f) is
estimated by dividing the total quantity of soil
delivered to the stream channel due to silvicultural
activities (man-induced) (TS silvicultural activity)
by that due to natural causes (TS natural), record
on worksheet V.6, step 13. For example, if the
quantity  of soil  delivered  due to silvicultural ac-
tivities was  299  tons  and that  delivered  due to
natural cause was 101 tons, the acceleration factor
(f) would be 3.0. The acceleration factor is recorded
on worksheet V.6, step 13. Note total from both
natural and  man-induced  failures would be equal
to 299 tons  (silvicultural  activity)  plus 101 tons
(natural) or 400 tons.
         ESTIMATE INCREASED SOIL
     DELIVERY DUE TO THE PROPOSED
          SILVICULTURAL ACTIVITY
  Estimate the increase in amount of soil mass
movement material that would be delivered from
the  area  being  considered for the  proposed
silvicultural activity.  The total  quantity  of soil
mass movement material  (TS) delivered  to the
stream channel (natural conditions)  is multiplied
by the acceleration factor (f) estimated from a site
previously  subjected to similar  silvicultural ac-
tivity, record on worksheet V.6, step 14. For exam-
ple,  if the  existing  natural condition delivered a
total quantity  of soil mass movement material to
the stream channel of 64 tons and the acceleration
factor estimated from a similar site subjected to a
similar silvicultural activity was 3.0, the estimated
potential soil mass movement material delivered to
the stream channel would be equal to 192 tons.
This completes the  procedure for determining in-
creased  soil delivery.
                                            V.45

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             APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
  Relating magnitude of management impact to
hazard index ranking has  the shortcoming that
once a site is  ranked as high hazard, alternate
management practices do not change the estimate
of management impact. Where data permit, quan-
tification of hazard index should be set up so that
management-caused  changes in hazard index are
directly proportional to degree of accelerated ero-
sion. Such a system would permit realistic assess-
ment of various management alternatives on the
mass erosion rate. However, additional studies are
needed to quantify the impact of  numerous
silvicultural activities.
                                     CONCLUSIONS
  This procedure is designed to quantify the poten-
tial volume of soil mass movement material that is
delivered to the closest drainageway as a result of a
proposed silvicultural activity. The analysis is con-
ducted  on areas that  have  previously  been
delineated as unstable. It should be reemphasized
that if  the  user  does not have  experience in
delineating unstable or potentially unstable areas,
additional assistance  from qualified specialists
should be obtained.
                                           V.46

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                                   LITERATURE CITED
Bailey, R.G. 1971. Land hazards related to land-
  use planning in Teton National Forest, Wyom-
  ing. USDA For. Serv. Rep., Intermt. Reg., 131 p.

Bailey, R.G. 1974. Land-capacity classification of
  the Lake Tahoe  Basin,  California-Nevada: A
  guide for planning. USDA  For. Serv., S. Lake
  Tahoe, Calif. 32 p.

Bell, J.R. and Q.R. Keener. 1977. An investigation
  of the feasibility of a cutbank slope design based
  on the analysis of natural slopes. Rep. to USDA
  For. Serv., Pac. Northwest For. and Range Exp.
  Stn., Portland, Oreg. 113 p.

Bell, J.R.  and  D.N. Swanston. 1972. A broad
  perspective to investigate the marked increases
  in occurrence of debris  avalanches  and debris
  torrents on recently clearcut slopes of igneous in-
  trusive  bodies in the  Coastal Mountains of
  northern California and southern Oregon. Report
  on file with USDA For. Serv., Pac. Northwest
  For. and Range Exp. Stn., Portland,  Oreg. 20 p.

Bjerrum, L. 1967. Progressive failure in slopes of
  overconsolidated plastic  clay and clay shales. J.
  Soil Mech. and Found. Eng. Div., ASCE., Vol.
  93, p. 1-49.

Brown,  C.B. and M.S.  Sheu. 1975.  Effects of
  deforestation on slopes.  J.  Geotech. Eng.  Div.
  ASCE  GTZ:  147-165.

Burroughs, E.R., G.R. Chalfant, and M.A. Town-
  send. 1976. Slope stability in road construction.
  USDIBur. Land Manage., Portland, Oreg. 102 p.

Burroughs, E.R. and B.R. Thomas. 1977. Declining
  root strength in Douglas-fir after felling as a fac-
  tor in  slope  stability. USDA  For.  Serv.  Res.
  Pap.INT-190.  27  p.  Intermt. For.  and  Range
  Exp. Stn., Ogden, Utah.

Carson, M.A. and J.J. Kirkby. 1972. Hillslope form
  and process. Cambridge  Press, London. 475 p.

Colman, S.M. 1973. The history of mass movement
  processes in the Redwood Creek basin, Hum-
  boldt  County,  Calif.  M.S.  thesis,  University
  Park, Penn.  State Univ., 151 p.

Culling, W.E.H. 1963. Soil creep and the develop-
  ment of hillside slopes. J. Geol., 71:  127-161.
Fiksdal, A.J. 1974. A landslide survey of the Ste-
  qualeho Creek watershed. Supplement to Final
  Report FRI-UW-7404, Fish.  Res. Inst., Univ. of
  Wash., Seattle, 8 p.

Flaccus, E. 1958. White Mountain landslides. Ap-
  palachia. 32: 175-191.

Fredriksen, R.L. 1963. A case history of a mud and
  rock slide on an experimental watershed. U.S.
  For. Serv. Res. NotePNW-1, 4 p. Pac. Northwest
  For. and Range Exp. Stn., Portland, Oreg.

Fredriksen, R.L. 1965. Christmas storm damage on
  the H.J. Andrews Experimental Forest. U.S. For.
  Serv. Res. Note PNW-29, 11 p. Pac. Northwest
  For. and Range Exp. Stn., Portland, Oreg.

Froehlich, H.A. 1973. Natural and  man-caused
  slash in headwater streams.  Loggers Handbk.,
  Vol. 33, 8 p.

Greswell, S., D. Heller and D.N. Swanston. 1978.
  (In press) Mass movement response  to  forest
  management in the central Oregon Coast Range,
  USDA  For.  Serv.  Gen.  Tech.  Rep.,  Pac.
  Northwest For. and Range Exp. Stn., Portland,
  Oreg.

Goldstein, M. and G. Ter-Stepanian. 1957. The
  long-term strength of clays  and deep creep  of
  slopes.  Proc.  4th Int. Conf.  of Soil Mech. and
  Found. Eng., 2: 311-314.

Gray, D. H. 1970. Effects of forest clearcutting on
  the stability of natural slopes. Assoc. Eng. Geol.
  Bull., 7:45-67.

Hack, J. T. and J.  C.  Goodlett. 1969.  Geomor-
  phology and forest  ecology of a mountain region
  in the central Appalachians. U.S. Geol.  Surv.
  Prof. Pap. 347. 66  p.

Haefeli,  R. 1965. Creep and progressive failure in
  snow, soil, rock and ice.  6th Int. Conf. on Soil
  Mech. and Found.  Eng.,  3:134-148.

Harr, R. Dennis, Warren  C.  Harper,  James T.
  Krygier, and Frederic S. Hsieh. 1975. Changes in
  storm hydrographs  after roadbuilding and clear-
  cutting  in the Oregon  Coast Range. Water
  Resour. Res. ll(3):436-444.
                                              V.47

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Kelsey, H. M. 1977. Landsliding, channel changes,
  sediment yield, and land use in the Van Duzen
  River  Basin,  North  Coastal  California,  1941-
  1975.  Ph.D. thesis, Univ.  Calif.  Santa  Cruz.
  370 p.

Klock, G. 0. and J. D. Helvey, 1976. Debris flows
  following wildfire in north 'central Washington.
  In Proc.  Third  Inter-Agency  Sediment  Conf.
  Symp.  1, Sediment Yields and Sources. Water
  Com. p. 91-98.

Kojan, E. P. 1973. Fox unit study area, Six Rivers
  National Forest. Del Norte County, Calif. Report
  on file, USDA For. Serv., Geotech and Mat. Eng.
  Pleasant Hill, Calif. 50 p.

Kojan, E.,  G.  T. Foggin,  and R. M. Rice. 1972.
  Prediction and analysis of debris slide incidence
  by  photogrammetry,  Santa Ynez-San  Rafael
  Mountains, Calif., Proc. 24th Int. Geol. Cong.
  Sect. 13,  p. 124-131.

Megahan, W.  F.  1972.  Logging,  erosion,
  sedimentation-are they dirty words? J. For. 70:
  403-407.

Megahan, W. F. and W. J. Kidd. 1972a. Effect of
  logging roads on sediment production rates in the
  Idaho Batholith. USDA For.   Serv. Res. Pap.
  INT-123. 14 p. Intermt. For.  and Range Exp.
  Sta., Ogden, Utah.

Megahan, W. F. and W. J. Kidd.  1972b. Effects of
  logging and logging roads  on erosion  and sedi-
  ment  deposition from steep   terrain.  J.  For.
  70:136-141.

Morrison,  P.  H.  1975.  Ecological  and  geo-
  morphological consequences of mass movements
  in the Alder Creek watershed  and implications
  for forest land management. B.A. thesis, Univ. of
  Oreg., Eugene, 102 p.

O'Loughlin, C.  L. 1972. An investigation of the
  stability of the steepland forest soils in the Coast
  Mountains, southwest British  Columbia. Ph.D.
  thesis, Univ. Vancouver, 147 p.

Pillsbury,  N. H.  1976.  A system for  landslide
  evaluation on igneous terrain. Ph.D. thesis, Colo.
  State Univ., Fort Collins, 109 p.

Prellwitz, R. W. 1977. Simplified slope  design for
  low standard roads in mountainous areas. Report
  on  file, USDA  For.  Serv., Reg.  1,  Missoula,
  Mont. 20 p.
Rothacher, Jack. 1959. How much debris down the
  drainage. Timberman. 60: 75-76.

Rothacher, Jack. 1971. Regimes of streamflow and
  their modification by logging, In Forest land uses
  and the stream environment. J. T. Krygier and
  J. D.  Hall, eds. Oreg.  State Univ., Corvallis, p.
  40-54.

Rothacher, Jack. 1973. Does harvest in west slope
  Douglas-fir  increase  peak discharge in small
  forest  streams?  USDA For.  Serv.  Res.  Pap.
  PNW-163, 13 p. Pac. Northwest For.  and Range
  Exp. Sta., Portland, Oreg.

Saito, M. and  H. Uezawa. 1961. Failure of soil due
  to creep. Proc. 5th Int. Conf. on Soil Mech. and
  Found. Eng. 1: 315-318.

Simons,  D. B. and T.  J. Ward.  1976. Landslide
  potential  delineation.  Report  CER75-76DBS-
  TJW23. Eng. Res. Cent., Colo. State Univ., Fort
  Collins. 188  p.

Swanson, F.J., D. N. Swanston, C.T. Dryness, and
  others. 1973. A conceptual  model  of soil  mass
  movement,  surface soil  erosion,  and  stream
  channel erosion processes. US/Int. Bio. Program.
  Conif. For.  Biome, Univ.  of  Wash.,  Seattle.
  Intern. Rep. 72.  19p.

Swanson, Frederick J. and Michael E. James. 1975.
  Geology and geomorphology of the H. J. Andrews
  Experimental Forest, western Cascades, Oregon.
  USDA For. Serv. Res. Pap. PNW-188. 14 p. Pac.
  Northwest For. and Range Exp. Sta., Portland,
  Oreg.

Swanson, Frederick J., George W. Lienkaemper,
  and James R. Sedell. 1976. History, physical ef-
  fects,  and  management  implications of large
  organic debris in western Oregon streams. USDA
  For. Serv. Gen. Tech.  Rep. PNW-56. 15 p. Pac.
  Northwest For. and Range Exp. Stn., Portland,
  Oreg.

Swanson, Frederick J., M. M. Swanson, and C.
  Woods. 1977. Inventory of mass erosion in the
  Mapleton Ranger Dist. Siuslaw National Forest.
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  Northwest For. and Range Exp. Stn., Corvallis,
  Oreg.  61  p.
                                             V.48

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Swanston, Douglas N. 1972. Results of mass ero-
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Swanston, Douglas N.  1973.  Judging landslide
  potential in  glaciated  valleys of  southeastern
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Swanston,  Douglas  N.   1974b. Slope  stability
  problems associated with timber harvesting in
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  States. USDA For. Ser. Gen. Tech. Rep. PNW-
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Swanston, Douglas N. and Frederick J. Swanson.
  1976. Timber harvesting, mass erosion and steep
  land geomorphology in the Pacific Northwest. In
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  of slopes. Norwegian Geotech. Inst., Publ. 52, p.
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  Application of geology for Engineering Practice.
  Geo. Soc. Am.  Berkey Vol. p.  83-123.

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  creep.  Proc.  3rd  Int. Conf.  Soil  Mech.  and
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  in engineering  practice. John  Wiley and Sons,
  Inc. N.Y. 566 p.

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  depositional  aspects  of  hurricane  Camille in
  Virginia, 1969. U.S. Geol. Surv. Prof. Pap. 804.
  80 p.

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  movements related to slope stability. J. Soil
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  205 p.
                                             V.49

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                Chapter VI
TOTAL POTENTIAL SEDIMENT
            this chapter was prepared by:
              David L. Rosgen

           with major contributions from:
               Kerry L. Knapp
              Walter F. Megahan
                    VLi

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                              CONTENTS
                                                                  Page

INTRODUCTION	  VI. 1
DISCUSSION  	  VI.3
  STREAM CHANNEL MORPHOLOGY AND WATER QUALITY	  VI.3
     Suspended Sediment 	  VI.4
       Interpretations Of Sediment Rating Curves	  VI.7
       Time Series Analysis-Recovery 	  VI.7
     Turbidity	  VI.9
     Bedload Determination 	  VI.9
       Evaluation Of Bedload Discharge Using Bedload Rating Curves	  VI.9
       Effects Of Bedload Changes On Stream Channels And Sediment
           Discharge	  VI.9
       Effects Of Direct Channel Impacts On Bedload Sediment Discharge .  VI.11
       Effects Of Sediment Supply Changes And Stream Power Reductions On
           Stream Channels 	  VI.11
THE PROCEDURE	  VI.13
  DETAILED ANALYSIS PROCEDURE 	  VI.13
    Suspended Sediment 	  VI.17
    Bedload Calculation	  VI.21
    Total Sediment 	  VI.26
LITERATURE CITED 	  VI.31
APPENDIX VI.A: EXAMPLES OF CHANNEL STABILITY RATINGS ....  VI.33
APPENDIX VLB: RELATIONSHIPS  BETWEEN  SEDIMENT  RATING
  CURVES AND CHANNEL STABILITY	  VI.39
APPENDIX VI.C: TIME SERIES ANALYSIS-RECOVERY PROCEDURE  ..  VI.43
                                  VLii

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                            LIST OF EQUATIONS

Equation                                                                  Page
VI. 1.    log Y = b + n log Q    	  VI. 17
VI.2.    Spre=  (Qpre) (C) (K) (T)    	  VI.18
VI.3.    Sp0it=  (Qpo.,) (C) (K) (T)    	  VI.18
VI.4.    SMX=  (CMX)  (Qpre) (T) (K)    	  VI.21
VI.5.    logBs= b + nlogQ    	  VI.22
VI.6.    Bpre=  (ibpre) (T) (K)    	  VI.22
VI.7.    Bpost=  (ibpos() (T) (K)   	  VI.26
VI.8.    logi^a + blog,,   	  VI.27
VI.9.    log Q = 0.366  + 1.33 log A +  0.005 log S - 0.056 (log S)2   	  VI.30
VI.C.l.  Y* = (b*e-Yt) (Q) 
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                              LIST OF FIGURES
Number                                                                   Pase
VI. 1.   —Diagrammatic relationship of a stable channel balance	  VI.2
VI.2.   —Relationships of sediment rate  and size to supply rate and transport
           capability	  VI.3
VI.3.   —Sediment rating curves for streams in western Wyoming	  VI.5
VI.4.   —Sediment rating  curve  for Needle Branch Creek, Oregon, 1964-1965
           water year	  VI.6
VI.5.   —Change in the sediment rating  curve  for the Eel River  	   VI.7
VI.6.   —Change in sediment rating curves of Needle Branch Creek 	  VI.8
VI.7.   —Bedload rating curve, central Idaho stream  	  VI. 10
VI.8.   —Relationship of bedload transport and stream  power	  VI. 12
VI.9.   —Procedural flow chart for estimating  potential changes in total sedi-
           ment discharge  	  VI. 14
Vl.lOa.—Typical hydrograph	  VI.17
Vl.lOb.—Flow duration curve  	  VI.17
VI.11.  —Representative sediment sampling distribution 	  VI.17
VI.12.  —Sediment rating curve	  VI.17
VI.13.  —Sediment rating curve for H.J. Andrews Stream 1	  VI.19
VI.14.  —Use of a constant maximum limit for sediment concentration compared
           to sediment rating curve	  VI.21
VI. 15.  —Relationship of sediment rating  curves to stream channel stability
           ratings, Region 1, USFS	  VI.22
VI.A.l. —Stream channels indicative of a stable channel due to resistant bed
            and bank materials	  VI.33
VI.A.2. —Stream channels indicative of a stable channel due to resistant bed
            and bank materials	  VI.33
VI.A.3.-VI.A.5.—Stream channels indicative of stable channel due to resistant
                  bed and bank materials	  VI.34
VI.A.6.-VI.A.8.—Highly unstable channels or  channels having poor stability
                  ratings are generally  associated  with easily detached  bank
                  and bed material  where channel erosion is significant	  VI.35
VI.A.9. —Stability and associated sediment supply affected by organic
            debris	  VI.36
VI.A.10.—Stability and associated sediment supply affected by organic
            debris	  VI.36
VI.A.ll.—Changes in stability due to increases in  sediment supply from road
            crossings	  VI.37
VI.A.12.—Soil mass movement, due to debris avalanche processes, deliver exces-
            sive amounts of sediment to the stream  	  VI 37
VI.A.13.—Soil mass movement, due to slump-earthflow processes, deliver exces-
            sive amounts of sediment to the stream  	  VI.38
                                     VLiv

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VI.B.l.  —Relationship of sediment rating curves to stream channel stability
           ratings, Region 1, USFS	  VI.39
VLB.2.  —Relationship of channel stability ratings to sediment rating curves in
           the Redwood Creek drainage	  VI.40
VI.B.3.  —Relationship of channel stability ratings to sediment rating curves for
           streams in the central Rocky  Mountain region  	  VI.41
                                      VI.v

-------
                          LIST OF WORKSHEETS
Number                                                                 Page
VI. 1.—Suspended sediment quantification	  VI.20
VI.2.—Bedload sediment quantification 	  VI.23
VI.3.—Sediment prediction worksheet summary	  VI.24
VI.4.—Bedload transport-stream power relationship  	  VT.28
VI.5.—Computations for step 21	  VI.29
                                    Vl.vi

-------
                                      INTRODUCTION
  One of the most significant and frequent water
quality changes resulting  from silvicultural  ac-
tivities is  accelerated, inorganic  sediment  dis-
charge. Land and  stream systems are constantly
adjusting to changes in the erosional rates of slopes
and  the  transport  capabilities  of  the  stream
systems draining those slopes.  Silvicultural  ac-
tivities can  exponentially  affect the rate of sedi-
ment discharge, depending upon the sensitivity of
the slopes and the affected stream reaches and the
degree and duration of impact.
  It is difficult to predict absolute changes because
of the  time-space variability  inherent in stream
systems; however,  several  consistent analytical
relationships involving the prediction of sediment
supply and transport  are  available. These
relationships can  be  used  to estimate relative
amounts of change in potential sediment discharge
resulting from proposed silvicultural activities.
                                               VI.l

-------
                                    _mm
                                    .01 FINE
         Feet per ml.
              FLAT .
                                                                                                               STEEP
                                                                                                    STREAM SLOPE
to
                                            •               •      •                 •
                                             /0oNXt            I             v»V&0
                                            •   ^<^  • 4-  •  ,^^    -
                                                    3n~^L_   T  \^^*^
                                             OEGRAOATION
AGGRADATION
             (Sediment Load)  x  (Sediment  Size)
                           Cxr
             (Stream Slope) x  (Stream Discharge)
                                     Figure VI.1.—Diagrammatic relationship of a stable channel balance (Lane 1955).

-------
                                         DISCUSSION
  In most cases, sediment objectives are stated in
terms  of acceptable increases in suspended sedi-
ment based on state and federal laws and physical
site conditions. The analysis procedure estimates
the amount of potential change in suspended sedi-
ment discharge and bedload sediment discharge as
well as qualitative effects on channel stability.
  Evaluation  of  potential sediment  changes re-
quires use of analytical procedures to make a con-
sistent comparative analysis of baseline and ac-
celerated levels. The procedures outlined in this
handbook  are not  designed to predict absolute
values  obtained  for any given year. They  do
however relate to  the  potential changes in  the
physical processes,  as affected by silvicultural ac-
tivities. The interpretation made from the results
of theses  analyses requires  a great deal of profes-
sional judgment.
    STREAM CHANNEL MORPHOLOGY
           AND WATER QUALITY


  Streams are dynamic systems where configura-
tions are adjusted in response to eight interrelated
variables  —  width, depth,  gradient,  velocity,
roughness of bed and bank materials, discharge,
concentration of sediment, and size of sediment
debris (Leopold  and others 1964). A change in one
or more of the  eight noted  variables produces
changes in channel processes with a net effect of
either  aggradation  or degradation. However, a
counteractive change occurs over time in the other
variables to prevent continued stream aggradation
or degradation (Shen 1976).
  When a stream system  is in a state of dynamic
equilibrium, the eroded material  supplied to and
stored  in the stream is balanced  with the energy
available to transport the material. As changes af-
fect sediment supply and stream energy, the chan-
nel system undergoes a series of adjustments and is
in disequilibrium. Under wildland watershed con-
ditions, dynamic equilibrium is not a steady state
from year to year, and annual variations in scour or
deposition may occur. These channel adjustments
not only affect  channel  stability,  but  generally
result in significant changes in sediment discharge.
   Lane  (1955)  diagrams a  stability relationship
 between sediment supply and stream energy (fig.
 VI.1),  indicating  stream  slope and  discharge
 (energy) are  proportional to sediment  load and
 sediment size (supply). Process changes which af-
 fect stream slope, stream discharge, sediment size
 and concentration may create unstable conditions
 which can result in  stream channel aggradation
 and/or degradation.
   Shen and Li (1976) describe a relationship where
 sediment discharge is a function of the supply rate
 and transport capability of various sized particles
 under a  particular flow  regime  (fig.  VI.2).
 "Washload" is that portion of the suspended load
 which is 0.0625 mm or smaller  (silts and clays).
   (FOR A PARTICULAR RIVER AND A
    PARTICULAR FLOW CONDITION ONLY)
                               TOTAL
                               SEDIMENT
                               TRANSPORT
    WASH
    LOAD
             dx
              SEDIMENT SIZE (dx = 0.0625mm)

 Figure VI.2.—Relationships of sediment rate and size to sup-
   ply rate and transport capability (Shen and Li 1976).
  Man-caused changes in channel process include
increased  debris,  constrictions  due to road  fill
encroachments,  stream  crossings,  alterations  in
streamflow amounts and timing through vegeta-
tion  modifications,  introduced sediment,  and
direct channel  alterations. These impacts affect
the rate and magnitude  of channel adjustments
and may  affect channel erosion through lateral
channel migration, change in bed form, and other
morphological  changes.  Such  changes  are
                                               VI.3

-------
ultimately expressed as differences in sediment
concentration per unit discharge and as changes in
bedload transport.

  The ability of streams to  adjust to imposed
changes varies with the type of bed  and bank
materials, the stability of the landform in which
the stream is incised, the amount and size of sedi-
ment in the channel, the hydraulic geometry of the
channel,  and the  runoff characteristics  of  the
watershed.
  Stream channels reflect the current  watershed
condition. The stability of natural channels varies
by geomorphic province and by  reach  within the
same watershed.  The ability to interpret  this
variance in stability is important when assessing
sediment  discharge  influenced  by channel
processes. A stability evaluation provides a consis-
tent  analytical comparison  of stability between
stream  reaches  within a  given  region and  is  a
reproducible method  of  assessing channel
characteristics.  Stability  evaluations  (Pfankuch
1975) examine primarily: (1) detachability of bank
and  bed materials,  (2)  availability or supply of
sediment as a function of degree  of entrenchment,
stored sediment, and landform  adjacent to  the
stream, (3) direct impacts on the channel, and (4)
energy forces available. Examples of streams with
various stability ratings are provided in appendix
VI. A.
             Suspended Sediment


  Suspended sediment is defined as that portion of
the total sediment load in transit under varying
flow  regimes that  is  measured using  depth-
integrated  samplers  (DH-48,  DS-49,  59)  as
described  by Guy  and  Norman  (1970).  This
procedure,  utilizing the equal transit rate method,
requires a continuous sample taken from the water
surface to within 3 inches of the stream bed. Sedi-
ment size generally includes sands or smaller, but a
specified size is  not  always predictable  due to
changes in  stream velocities.
  Suspended sediment from stream channel ero-
sion is the  major contributor to total annual sedi-
ment discharge in some streams draining forested
watersheds (Anderson 1975, Striffler 1963, Rosgen
1973,  Flaxman 1975, and Piest and others 1975).
The sediment rating curve has been developed and
used for analyzing sediment discharge for the past
40 years. A sediment rating curve is derived from
values of measured suspended sediment,  in  mil-
ligrams/liter,  correlated  with  stream  discharge
(cfs). Sediment rating curves represent changes in
sediment supply and stream channel adjustments
associated with the accelerated sediment introduc-
tion.
  Recent applications and interpretations of the
sediment rating curve approach have been used in
management  applications  (Flaxman  1975  and
Rosgen  1975a). This latter  interpretation  of the
sediment rating curve technique is presented for
use in this chapter. The sediment rating curve ap-
proach  involves  depth-integrated  sampling  for
suspended sediment over a wide range of climatic
situations and  representative flows. Examples  of
typical sediment rating curves are shown in figures
VI.3 and VI.4.

  Most of the  annual sediment discharge results
from streamflow that generally occurs less than  10
percent  of  the time.  Since  streamflow  is  the
primary  variable associated with stream  energy,
changes  in  flow amounts or timing directly in-
fluence  sediment discharge. Although  flows vary
from year to year, time-dependent plots generally
are not evaluated because long-term records are re-
quired. However, flow-dependent analysis can be
made based on representative flows monitored  over
a water year (October 1  through September  30),
where variables affecting sediment concentrations
are  determined concurrently  with  stream  dis-
charge.  Sampling "representative flows" involves
collection of suspended sediment  during various
flow  and  seasonal  conditions  to  detect  any
variability in concentration for the same flow dur-
ing a water year.  Significant  variability  can be
analyzed separately.  Sampling intensity depends
on flow variation and anticipated supply changes.
Minimum sampling stratification for the develop-
ment of sediment rating curves is shown in step 3 of
the procedure.
  If the representative flows  cannot be sampled to
establish  a sediment rating   curve,  continued
monitoring into the next  water year may be re-
quired. The reliability of the  procedure may be
reduced if representative flows, as defined,  are not
sampled.
  The many research efforts utilizing the sediment
rating curve approach  are  summarized  in  the
USFS-EPA  "Non-Point Water Quality Modeling,
Wildland Management"  (1977). Flaxman  (1975)
used this approach to determine the amount  of
channel erosion attributable to man's activities.
Applications by Fames (1975) were designed to
                                              VI.4

-------
identify changes in sediment discharge as a result
of upstream  changes in  land use on  selected
watersheds in Montana. The technique is presently
used as  a portion  of the analytical  prediction
techniques  for determining potential  changes  in
sediment due to timber harvest on some national
forests in Montana and Idaho (USDA  Forest Ser-
vice 1975).
10000
                                                              100.0    200.0
                                   STREAM DISCHARGE, (cfsj
              Figure VI.3—Sediment rating curves for stream* In western Wyoming (Holstrom 1976).
                                             VI.5

-------







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 Interpretations Of Sediment Rating Curves

   Shifts in the sediment rating curve reflect both
 natural and  man-induced changes that alter the
 slope  and intercept of the regression  equation.
 These shifts indicate the dynamic nature of stream
 channels.
   Examples  of changes in sediment rating curves
 have occurred following  a major  flood in 1964,
 which shifted the sediment rating curve a full order
 of magnitude on the Eel River in northern Califor-
 nia  (Flaxman 1975). Thus, an increase in stream
 channel sediment supply that aggraded many river
 reaches resulted in major channel adjustments and
 associated increased sediment discharge (fig. VI.5).
 10.000-
I.
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g
n
S
Q
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0.
(0
    10-
     100
                 /-
 uobo          ioOoo
STREAM DISCHARGE, (cfs)
                                           100)000
 Figure VI.5.—Change in the sediment rating curve for the Eel
  River, Scotia, Calif., showing increases in sediment con-
  centration per unit discharge when flood caused a change
  in sediment deposition (Flaxman 1975).
For any given flow on the Eel River following the
flood, the sediment  concentration  was exponen-
tially higher. Suspended sediment discharge under
post flood condition is very sensitive to flow in-
creases. Flaxman (1975) cited similar results from
channel restoration measures  applied to streams
where channel erosion was a predominant source of
the total annual suspended sediment discharge.

  An analysis of the effects of clearcutting on sedi-
ment rating curves was recently conducted on the
Needle  Branch  drainage, near the  Oregon coast
 (Sundeen 1977). This analysis indicated a shift of
 the  regression constants of the sediment rating
 curve following the first year of harvest (fig. VI.6).
 Even though the  highest  flood  peaks occurred
 before harvest (due to the 1964 flood), the major
 shift in the sediment rating curve occurred follow-
 ing timber removal. The recovery of Needle Branch
 has  been fairly rapid; in the second year following
 clearcutting, the sediment rating curve (1967-68)
 returned nearer the pre-flood condition. Under the
 post-flood condition, any further change in dura-
 tion of bankful stage or in magnitude of peak flows
 due to  timber harvesting will produce exponen-
 tially  higher sediment  discharge.  These
 relationships agree closely with those suggested by
 Flaxman (1975).
  The sediment rating  curve technique has been
 used to evaluate timber  sale impacts in Montana
 and Idaho (Rosgen  1975a). Changes  in sediment
 supply were  linked to individual  sources when a
 surveillance monitoring program was initiated to
 show these "shifts"  in sediment rating curves. In
 many instances, the major cause for the shifts and
 change  in stability was associated with sediment
 supply increases  by roads,  debris slides and in-
 creases  in stream discharge. Stream  channel im-
 pacts  can  be evaluated  through  relationships
 developed  between measured  sediment  rating
 curves and stream channel stability as explained in
 appendix VLB.
Time Series Analysis-Recovery

  Conceptually, it is desirable to predict not only
the magnitude and direction of change  in  sedi-
ment rating curves,  but also the time required for
the sediment rating curve to return  to  its pre-
disturbance position. However, it  is beyond the
state-of-the-art  to  actually predict  a  post-
silvicultural  activity  sediment  rating  curve.
Despite this, it is of value to qualitatively evaluate
recovery to help interpret analysis  results.
  A qualitative  procedure  for  determining the
recovery potential  of streams by  morphological
descriptions was  developed and used in northern
Idaho (Rosgen 1975c). It evaluates recovery poten-
tial based on depth of channel to bedrock, gradient,
material size, and  channel stability ratings. The
recovery period is based on the type and dates of
impact from historical records on various streams,
differing channel materials, gradients, etc. Tested
quantitative techniques for  determining recovery
periods and  rates at which the sediment  rating
                                                VI.7

-------
1000.0
    1.0
                                       1.0        2.0                   10.0
                                           STREAM FLOW, (c.f.s.)
1000
            Figure VI.6.—Change In sediment rating curvet for Needle Branch Creek, Oregon, showing the
              shift in rating curves due to 1964 flood and silviculture! operations (Sundeen 1977).
                                                  VI.8

-------
curves return to pre-silvicultural activity  condi-
tions have not been developed. A technique that
may have potential application is presented in ap-
pendix VI.C.  Any  recovery technique should be
developed locally, because  great variation can be
expected  in  regional  relationships of recovery
response.
                  Turbidity

  Turbidity is  an optical characteristic of water
 quality, whereas suspended and bedload sediment
 are related to the actual rate and weight of trans-
 ported inorganic soil particles. It is often possible to
 establish  a correlation  between  turbidity  and
 suspended sediment concentration. A relationship
 can be established using regression analysis based
 on local data if the analysis is: (1) conducted on the
 same stream reach under a wide range of flow con-
 ditions, and (2) conducted so that the turbidity
 sample is also depth integrated. If significant cor-
 relations can be established between the two water
 quality characteristics, one may be inferred from
 the other. Turbidity will not be directly analyzed in
 this chapter.
            Bedload Determination

  Bedload is inorganic soil particles of various sizes
which are transported in contact with or near the
streambed. Bedload transport becomes a predomi-
nant factor during major runoff events, where suf-
ficient energy is available to dislodge and transport
the larger sized particles generally  armored in the
streambed or supplied to the stream from the chan-
nel sides and slopes. Studies of mountain streams
in northern  Idaho have shown bedload to be less
than 5 percent of mean annual total sediment dis-
charge   when  measured concurrently with
suspended sediment on first to third order streams
(Rosgen  1974).  Emmett (1975) determined that
bedload transport for gravel bed streams in the up-
per Salmon  River area was approximately 1 to 10
percent  of  the  suspended sediment load tran-
sported. However, evaluation of the  basic processes
involved in bedload transport  is valuable to deter-
mine  the potential changes  in stream channel
stability and in  associated suspended  sediment
concentrations.
  Numerous empirical  bedload transport  equa-
tions are described in the EPA-USFS  "Non-Point
Water Quality Modeling Wildland  Management"
 (1977). However, data for validation of natural
 channels  and for testing these bedload  transport
 equations  are limited; therefore, it is difficult to
 convert them to  quantitative expressions of water
 quality.
Evaluation Of Bedload Discharge
Using Bedload Rating Curves

  The procedure presented in this chapter requires
bedload sampling concurrent with suspended sedi-
ment sampling. The method for establishment of
bedload rating curves is similar to the procedure for
developing  suspended  sediment  rating curves.
Bedload is measured from the bed surface to 3 in-
ches above the bed using a pressure differential
type  sampler (Helley  and Smith  1971) during
representative flows in 1 water year. An example of
a bedload rating curve is shown in figure VI.7.
  The calculations utilizing the  bedload rating
curve procedure are designed to:
  1. Predict a quantitative change in bedload sedi-
     ment discharge by comparing changes  in
     amounts and seasonal distribution  of excess
     water;
  2. Determine the  relative  contributions  of
     suspended and bedload sediment;
  3. Provide data to develop local bedload-stream
     power relationships to assess potential stream
     channel changes and resulting changes  in
     bedload sediment discharge.
Effects Of Bedload Changes On Stream
Channels And Sediment Discharge

  The potential impact on stream channels due to
introduced  sediment and/or changes in stream
power is  calculated using procedures similar to
those presented by Leopold and Emmett (1976).
This requires the development of regional or local
bedload stream power relationships expressed as a
function  of the size of material being transported
(fig. VI.8). At high flows, transport rates become
directly proportional to stream power,  as suggested
by  Bagnold (1966). This is shown in figure VI.8,
where the ratio of transport rate (ib) to unit stream
power (w)  is represented as ib/w = 100%. Stream
power, as used in the proposed method, is defined
as the unit weight of water (1,000 kg/m3) times the
discharge of water (m3) per meter width over the
total  stream width (m) times the gradient of the
                                               VI.9

-------
  1.0-
 5
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                                   2.09
                                                                             X


                                                                             X
  .01
.001
      .1
         1
                                      T
                             1.0

                    STREAM FLOW, (cfs)
1
1
T
                                                                                               10
                      Figure VI.7.—Bedload rating curve, central Idaho stream (Megahan 1978).




                                                 VI. 10

-------
stream (m/m) (Leopold and Emmett 1976). The in-
tegration of cross-sectional area and velocities as-
sumes rectangular banks  for the calculation. To
develop this relationship, it is necessary to measure
particle size of transported material, water surface
slope, stream discharge, and stream width.
  The locally derived stream power-bedload trans-
port rate relationship should be calculated using
the  same  principles  as in  the  regression
relationships of suspended sediment and bedload
transport to streamflow.
  The objective is  to  estimate the potential for
stream channel scour and/or deposition caused by
direct  impacts  that change  the  stream  power
variables (surface water slope and bankful width).
Introduced potential sediment volume and particle
size  from soil mass movement  are qualitatively
evaluated,  based on the available stream  power
and related sediment transport rates under bankful
discharge.

Effects Of Direct Channel Impacts On
Bedload Sediment Discharge

  Effects of silvicultural activities  on  the stream
power variables and associated sediment transport
can be calculated. Activities that change local sur-
face  water  slope, discharge, and bankful stream
width can be affected by stream channel encroach-
ment of road fills, logging debris, and stream cross-
ings. Potential changes in  bedload transport are
obtained  through  calculations  involving
relationships similar to those  depicted in  figure
VI.8.
  Field evaluations of channel alterations resulting
from certain silvicultural activities will provide in-
formation on changes in stream width and surface
water slope as measured above versus below chan-
nel impact  areas. A  change in stream power  (as-
suming no change in sediment supply) would result
in a direct change in bedload discharge.
 Effects Of Sediment Supply  Changes  And
 Stream Power Reductions On Stream Channels

   Channel effects caused by introduced sediment
 from soil mass movement may be evaluated using
 the  bedload transport  rate-stream  power
 relationship on the stream reach directly below the
 source. A calculation involving bankful discharge,
 bankful width and surface slope determines the in-
 stantaneous maximum bedload  transport  rate.
 Sediment deposition in the channel may result if
 the potential delivered soil mass movement volume
 and change in particle size exceeds the maximum
 potential transport  rate under  a given stream
 power.

   A  calculation  involving  bankful discharge  is
 needed if extrapolation of the bedload transport
 rate-stream power relationship is needed above the
 third order reach. Riggs (1976)  presents a
 procedure for determining bankful discharge. This
 approach involves a relationship between stream
 slope  and velocity,  eliminating the  need  to es-
 timate a roughness coefficient to obtain velocity.
 The bankful stage determination uses procedures
 documented by Williams (1977), where a channel
 configuration indicating a bankful stage is obser-
 vable on the upper limit of the "active floodplain."
  A reduction in stream power caused by a debris
dam would yield lower transport rates. Assuming
no reduction  in sediment availability,  the  dif-
ferences  in  sediment yield may result  in local
deposition or stream aggradation. The potential for
deposition  or aggradation is evaluated  in  the
detailed procedures recommended in this chapter.
Until such benchmark references or long-term data
can be  collected and analyzed,  only qualitative
predictions  of stream channel  changes can  be
made.
                                             VI. 11

-------
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                               I                     I                     I

                              10'1                  1                    10

                               UNIT STREAM POWER, a. ,  in kg/m-s
           Figure VI.8.—Relationship of bedload transport and stream power for the East Fork River, Wyom-
             ing (Leopold and Emmett 1976).
                                            VI.12

-------
                                     THE PROCEDURE
  The analysis procedure for determining potential
changes in total sediment discharge is sequentially
diagrammed in the procedural flow chart, figure
VI.9. The following stepwise procedural description
and discussion correspond with the procedural flow
chart and provide directions for completing the
analysis. Worksheets provided for the analysis are
referenced where applicable. Table VI. 1 provides a
summary of all data input required to use the total
sediment discharge procedure.

  The following assumptions  are inherent in this
analysis procedure:
  1.  No distinction will be made between material
     detached from the channel banks  and that
     previously  deposited on  the streambed and
     channel bars which is available for redistribu-
     tion under varying flow regimes.
  2.  Increases in  stream discharge exponentially
     increase  suspended sediment and  bedload
     sediment.  Statistical  relationships can  be
     established for sediment rating curves.
  3.  Suspended sediment rating curves  represent
     the existing  relationship between  sediment
     availability and stream discharge for a par-
     ticular  stream  reach  and watershed area.
     Temporal  and spatial distribution of  sedi-
     ment is not addressed in this procedure. For
     the purpose  of  this analysis, temporal and
     spatial distribution of sediment is assumed to
     be constant.
  4.  The procedure  is  applicable to watershed
     basins of third order size.
  5.  The size of material delivered to streams from
     surface erosion is assumed to be silt and clay
     (washload) or smaller than .0625 mm.
  6.  All of the  introduced  washload sediment is
     transported  through individual stream
     reaches (i.e.,  no storage is calculated, and the
     stream has sufficient energy to transport this
     sediment size).
  7. A relationship can be developed between sedi-
    ment  transport rate and  stream  power
    through measurements of stream slope, dis-
    charge, bedload transport rate, and particle
    size (Dso = particle size for which 50 percent
    of the sediment  mixture  is finer).
  8. Water surface slope  does not change  with
    water surface elevation (stage).
  The  prediction  techniques  presented in  the
analysis section are not recommended to replace
local data or transport prediction capability, when
they are available. The analysis provides the basic
process relationships needed for evaluation until
local data become available. A monitoring program
to measure pre- and post-silvicultural activity sedi-
ment concentrations for the various flow regimes
would  help verify the sediment discharge predic-
tions. Baseline channel geometry surveys should
also be  conducted to determine changes in stream
aggradation or degradation, lateral migration, or
other channel adjustments.
  It is important to notice that all the calculations
through  step  20  are designed  to relate  quan-
titatively to the potential sediment discharge  at
the third order reach. Step 21 is a qualitative in-
terpretation for various reaches in the subdrainage
as  affected by stream  channel  response to  in-
troduced sediment from soil mass movement, and
channel encroachments.
    DETAILED ANALYSIS PROCEDURE

Step  1. Subdrainage  and  Stream  Reach
          Characterization
  Procedure: Select a representative third order
stream reach where data collection is required.
  Discussion: For quantitative evaluations (steps
1-20) this stream reach will be used. For qualitative
evaluation (step 21), individual first through third
order streams will be selected.

Step 2. Determination  of  Pre-  and  Post-
          Silvicultural  Activity Hydrographs  or
          Flow Duration Curves
  Procedure:  Obtain  the  output  from the
hydrologic analysis for the selected third  order
drainage as outlined in chapter El. Outputs re-
quired are:
  a. Potential  increase in total  annual  water
     production;
  b. Seasonal distribution of water (based on 6- or
     7-day  averages)   (figs.  Vl.lOa or  Vl.lOb)
     represented as either hydrographs  or flow
     duration curves for:
                                             VI.13

-------
                 PROCEDURAL STEP
                 COMPUTATION OR
                   EVALUATION
                     DATA
                     INPUT
                    ANALYSIS
                    OUTPUT
                                          PRE-SILV. ACT!
                                          HYDROGRAPHS
                                    OR FLOW DURATION CURVES
                                          POST-SILV. ACT.
                                          HYDROGRAPHS
                                    OR FLOW DURATION CURVES
                    SEDIMENT RATING
                      CURVES AND
                   CHANNEL STABILITY
                                          BEDLOAD
                                        RATING CURVE
              POST-SILV.
             ACT. POTENTIAL
              SUSPENDED
               SEDIMENT
              DISCHARGE
   CONVERT
  SUSPENDED
SEDIMENT LIMITS
   IN mg/1 TO
  TONS/YEAR
   PRE-SILV.
ACT. POTENTIAL
  SUSPENDED
  SEDIMENT
  DISCHARGE
   PRE-SILV.
ACT. POTENTIAL
   BEDLOAD
  DISCHARGE
  POST-SILV.
ACT. POTENTIAL
   BEDLOAD
  DISCHARGE
                                      TOTAL PRE-SILV. ACT. POTENTIAL
                                           SEDIMENT DISCHARGE
                                              (BEDLOAD AND
                                      	SUSPENDED LOAD)
              INCREASE IN TOTAL
        POTENTIAL SEDIMENT DISCHARGE
                                      POST-SILV. ACT. TOTAL POTENTIAL
                                           SEDIMENT DISCHARGE
                                              — ALL SOURCES
             Figure VI.9-Procedural (low chart for estimating potential changes in total sediment discharge.
                                            VI.14

-------
                m
           SUBDRAINAGEAND
     STREAM REACH CHARACTERIZATION
        MB]
                                     INTRODUCED SEDIMEN
                                            FROM
                                     SOIL MASS MOVEMENT
                                            TOTAL INTRODUCED
                                             SEDIMENT  FROM
                                             SURFACE EROSION
 CHANNEL GEOMETRY>
     DATA FOR
THIRD ORDER STREAM;
      fl9l
 POST-SILV. ACT.
CHANNEL IMPACTS
     JM.
    TOTAL
 COARSE-SIZE
SEDIMENT FROM
  SOIL MASS
  MOVEMENT
           BEDLOAD SEDIMENT
            TRANSPORT RATE
      —STREAM POWER RELATIONSHIP
       QUALITATIVE DETERMINATION
     |OF CHANNEL CHANGE POTENTIAL
               BASED ON
          INTRODUCED SEDIMENT
       FROM SOIL MASS MOVEMENT
          AND CHANNEL IMPACTS
         COMPARE POST-SILV. ACT. TOTAL POTENTIAL
         SUSPENDED SEDIMENT TO SELECTED LIMITS
                                                          'Silvicultural Activity
                             Figure Vl.9—continued
                                     VI. 15

-------
              Table VI.1.—Summary of input required to use the total sediment discharge procedure.
          Data requirements
                                   1234567
                    Procedural steps
                 8  9  10 11 12  13 14  15 16  17 18  19  20 21
   Aerial photography
     and stream reach
     selection
   Pre-silvicultural activity
     hydrographs
   Post-silvicultural activity
     hydrographs
   Measured suspended
     sediment (mg/l)
X  X   X  X
   Measured stream
     discharge (cfs)
X  X   X  X   X  X
   Measured bedload sediment
     (tons/day)
              x  x
   Allowable maximum sediment
     concentration (from water quality
     objective) (mg/l)
   Fine particle size from soil mass
     movement source (ch. V) (tons)
   Coarse particle size from soil mass
     movement source (ch. V) (tons)
   Measured width from measured
     third order stream discharge (ft)
                           x   x
Surface erosion (ch. IV) (tons)
Bankful stream width (ft)
Bankful surface water slope (ft/ft)
Bankful depth (ft)
Bankful discharge (cfs)
x
x
X
X
X
   Measured depth from measured
     third order stream discharge (ft)
   Measured surface water slope from
     measured third order stream
     discharge (ft/ft)
                                                                                             x      x
   Predicted change in width with
     post-silvicultural activity
   Predicted change in surface water
     slope with post-silvicultural
     activity
     (1) baseline condition (pre-silvicultural  ac-
         tivity)
     (2) existing condition (pre-silvicultural  ac-
         tivity)
     (3) proposed condition (post-silvicultural ac-
         tivity).
  Discussion:  Distribution  estimates  of  excess
water both  before and after silvicultural activity
are  required  to determine   changes  in  both
suspended sediment and  bedload discharge. If a
particular  short  duration  stormflow response is
             responsible for the majority of the sediment dis-
             charge  in  a particular reach,  a shorter duration
             (less  than 7-day)  analysis  will increase the sen-
             sitivity for flow related sediment transport calcula-
             tions. Thus, the user may specify a local hydrologic
             evaluation,  which is  more  accurate than the
             procedures recommended.
               It may be necessary to determine the hydrologic
             effect of various activities on the rising and reces-
             sion limbs of the hydrograph. If a hysteresis effect
             is prevalent, separate analyses may be made using
             the relationships established in step 3.
                                                 VI.16

-------
   100-
 I
 DC
    50-
    25-
                                                                   100-
                                                              Ł
                                                              o


                                                              I
                                                              LL
                                                              5
                                                              LU
                                                              IT
                                                              CO
                    TIME
           (SELECTED INCREMENTS)

      Figure VI.10a—Typical hydrograph.
                                            Pre-silvicultural activity
                                            Post-silvicultural activity
                                                                    50-
                                                                   25-
                                                                         5         50         1W)
                                                                           PERCENT OF TIME a Q
                                                                         IS EQUALED OR EXCEEDED
                                                                  Figure VI.10b.—Flow duration curve.
 Note: If silvicultural activity  does not increase
 flow, the calculations involving post-activity flow
 related suspended and bedload increases would not
 be needed for the evaluation.
              Suspended Sediment

 Step 3. Establish Sediment Rating Curves and
   Determine Stream Channel Stability
   Procedure: (a) Concurrently measure suspended
 sediment, and  associated stream discharge over
 wide variations in flow conditions for a water year
 (fig.  VI.11).  After the data have  been collected a
 regression analysis should be employed to calculate
 coefficient of  determination and the  log trans-
 formed regression equation of:
                                                                 log Y  = b + n log Q        (VI.l)
                                                  where:
                                                    log Y  = logarithm of suspended sediment con-
                                                             centration (mg/1)
                                                        b  = constant representing intercept of the
                                                             regression line
                                                        n  = constant  representing  slope  of  the
                                                             regression line
                                                    log Q  = logarithm  of stream  discharge (cfs  or
                                                             m3/sec)
                                                    The actual data points are plotted on log-log
                                                  paper with suspended sediment  in mg/1 on the Y
                                                  axis and stream discharge in cfs on the X axis. Us-
                                                  ing this data, coefficients for a regression equation
                                                  of  the   form  indicated  in  equation  VI.l  are
                                                  calculated. The regression line is then drawn on the
                                                  figure (fig VI.12).
•2 100-

O
i  50H
   ill
   DC
      25-
                             SAMPLE
                                 POINTS
            I   I   I   I   I   I   I   I   I  I  I
                  TIME (MONTHS)

Figure VI.11.—Representative sediment sampling distribu-
  tion.
                                                      LJJ
                                                           100-
Q
LU
w -
Q 0) 10-
LU
G
Z
LU
O.
W
D
                                                          1-
                                                                    'I
                          I
                                                                    1       10       100    100r
                                                                      STREAMFLOW (cfs)

                                                            Figure VI.12.—Sediment rating curve.
                                               VI.17

-------
  (b) Calculate the coefficient  of  determination
(r2) for the relationship and  identify variability
(such as hysteresis  effect).
  (c)  Determine  stream channel stability rating
for the reach being evaluated  (Pfankuch 1975).
  Discussion:  Sampling should obtain sediment
concentration  for representative flows, as well as
seasons where  these concentrations expect  to be
varied. Sampling as a minimum for representative
flow should reflect concentrations for the following
conditions:
  1.  Early and/or low elevation  snowmelt runoff;
  2.  Early versus late season stormflow runoff;
  3.  Rising stage for both stormflow and snowmelt
     runoff;
  4.  Recession  stage  for both stormflow and
     snowmelt  runoff;
  5.  Bankful stage  on higher peaks;
  6.  High  elevation  releases   and/or  snowmelt
     peaks;
  7.  Base flow;
  8.  Events which may affect  the sediment rating
     curve,  such as rain on  snow events,  short
     duration-high  intensity storms, or long dura-
     tion storms  producing sustained high flows;
  9.  Disturbance  factors  influencing  sediment
     supply, such as debris jams, changes in chan-
     nel stability (sampled concurrently above and
     below to determine influence  of stored  sedi-
     ment, etc.),  road crossings or encroachments,
     and large  areas of subdrainage hydrologically
     altered by vegetative modifications.
  If significant differences in sediment concentra-
tion  result from the rising versus falling limbs of
the  hydrograph  or earlier storm   peaks,  these
relationships should be  kept separate and used in
the calculation of both  pre- and post-silvicultural
activity  streamflow effects to  more accurately
portray  existing conditions.  A more  detailed
hydrologic evaluation would increase the curve sen-
sitivity  for these conditions. Separate regression
lines  may  be  established  and  used for  the ap-
propriate flows when calculating pre- and post-
silvicultural activity sediment discharge (steps 4
and 5) caused by increased flow only. This requires
additional data on water yield  to reflect the poten-
tial runoff response to a particular activity  on
various  stormflow periods and  rising versus falling
limbs of the hydrograph  (fig. VI. 13) (Fredriksen
1977). The two sediment rating curves then can be
applied to those  respective  portions of the post-
silvicultural activity hydrograph (fig. VLlOa).
Step • 4.  Calculate  Pre-Silvicultural  Activity
          Potential   Suspended   Sediment
          Discharge
  Procedure:  From  the pre-silvicultural activity
hydrograph (baseline  +  existing  condition, fig.
Vl.lOa) and the sediment rating curve (fig. VI. 12),
determine sediment concentration for each 7-day
average flow condition. Worksheet VI. 1 is provided
for this calculation. The formula used in worksheet
VI.l is:

           Spre=  (Qpre) (C) (K) (T)        (VI.2)
where:
  S    = pre-silvicultural activity suspended sedi-
         ment discharge  (tons/yr)
    C  = concentration  of  suspended  sediment
         (mg/1)
  Q    = pre-silvicultural activity streamflow (cfs
         or m3/sec)
    K= conversion factor  0.0027 (.0864  if
         streamflow is  in  mVsec)  (Guy  and
         Norman 1970)
    T  = duration (days)
  Calculation format  is  provided in worksheet
VI.l, columns 2 to 4. Summarized sediment dis-
charge increments (col. 4, wksht.  VI.l) is  trans-
ferred to worksheet VI.3, item A. To obtain values
of C, use the pre-silvicultural activity 6- or 7-day
average flow  (fig. Vl.lOa); then utilizing  figure
VI. 12, sediment rating curve, read vertically to the
regression line, then horizontally where the Y axis
indicates corresponding values of suspended sedi-
ment concentrations (C). This is done for each flow
value of pre-activity discharge given a specified (6-
or 7-day) duration. Worksheet VI.l provides an ac-
counting format for these calculations.

Step  5. Calculate  Post-Silvicultural  Activity
          Potential  Suspended   Sediment
          Discharge
  Procedure: From the post-activity hydrograph or
 post-activity flow duration curve (fig. VI. 10 a or b)
and the sediment rating curve (fig. VI. 12), deter-
mine  the sediment concentration for  each  7-day
average flow condition. Worksheet VI.l is provided
for this calculation. The  formula that is used in
worksheet VI.l is the same as that in step 4, except
that post-activity values for flow are  used.
       Spost =  (Qpost) (0   (T)        (VI-3)
where:
  S   t  = post-activity  suspended  sediment  dis-
         charge due to flow increase
                                               VI.18

-------

•n
=r.<5'
5 c
§<
Q. Ik
» u
" 1
» j?
Si
< 3
I|
P'
3 O
i|

-------
                                                                               WORKSHEET VI.1

                                                      Suspended sed imerit quant i f icat ion for
8
(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days




















(b)
Number
of
days
pre-
si Ivi-
cultural
act i v i ty




















(c)
Number
of
days
post-
si Ivi-
cu Itural
activity




















(21
Pre-
si Ivi-
cultural
act i v i ty
flow
(cfs)




















(3)
Sus-
pended
sediment
concen-
trat ion
(mg/l )




















(4)
Total increment
suspended
sed iment
cols. (2) x (3)
x (1 .b) x .0027
(tons)




















(5)
Post-
si Ivi-
cu Itural
activity
flow
(cfs)




















(6)
Sus-
pended
sediment
concen-
trat ion
(mg/l)




















(7)
Total increment
post-si Iv leu Itural
activity suspended
sediment
cols. (5) x (6) x
(l.c) x .0027
(tons)




















(8)
Maximum
concentra-
tions from
selected
water qua 1 Ity
object I ve
(mg/l )




















(9)
Maximum
sediment
discharge
cols. (2) x
(8) x (l.b)
x .0027
(tons)




















                     (Totals are rounded to nearest tenth)
                                                                          Total
                                                                                                                 Total
                                                                                                                                                    Total
                                                                                                                        tons/yr
                                           Sumnary:  Total pre-siIvicuItural activity suspended sediment discharge
                                                     TotaI post-si IvicuIturaI  act ivity suspended sed iment d i scharge
                                                     Total maximum sediment discharge

-------
 Qpost
    c =

    K =
    T =
         post-activity discharge (cfs)
         concentration  of suspended  sediment
         (mg/1)
         conversion factor  0.0027 (.0864  if
         streamflow  is  in mVsec)   (Guy  and
         Norman 1970)
         duration (days)
  Summarize sediment discharge increments (col.
7, wksht. VI. 1) and transfer total to worksheet VI.3,
item B.
  Discussion: The accuracy of this calculation is
highly dependent on the hydrologic evaluation and
on the  observed variability in the sediment rating
curves. A variability range may be presented as an
option  for tons/year of  suspended sediment  dis-
charge.  However, for comparative purposes, pre-
activity values should be calculated similarly.

Step 6. Convert Suspended Sediment Limits in
         mgA to tons/yr
  Procedure:  This calculation involves the same
procedure used in step  4,  except  the suspended
sediment concentrations  (CMX) are derived from
various water quality objectives, expressed in mgA.
A conversion to  comparable units  in  tons/year is
needed to compare potentials for  prescribed con-
trols. Thus:
                                                    class lines using locally derived relationships (fig.
                                                    VI. 15). The major divisions above existing condi-
                                                    tions of channel stability should be used. A conver-
                                                    sion for pre-silvicultural activity flows from mg/1 to
                                                    tons provides an interpretation of the effects of in-
                                                    troduced sediment (in tons) on channel stability.
                                                      O)
                                                      E
                                                     LLJ
                                                     2
                                                     O
                                                     ill
                                                     CO
                                                     Q
                                                     HI
                                                     O

                                                     LU
                                                     Q.
                                                     CO

                                                     CO
                                                        100.0-
                                                          10.0-
                                                           1.0
                                                                           \           \
                                                                         10.0       100.0
                                                                  STREAM DISCHARGE (cfs)
                                                   Figure VI.14—Use of a constant maximum limit for sediment
                                                     concentration compared to sediment rating curve.
where:
        SMX=  (CMX) (Qpre) (T) (K)
                                        (VI.4)
  SMX = maximurn suspended sediment discharge
         (tons/yr)
  CMX= selected maximum suspended sediment
         concentrations (mgA)
    K= conversion  factor 0.0027 (.0864 (metric
         tons) if streamflow is in m3/sec) (Guy and
         Normal 1970)
    T = duration (days)
  Discussion: The pre-silvicultural activity sedi-
ment rating curve is used to compare analysis out-
put (tons/yr) to state standards which  have al-
lowable departures  for suspended sediment  con-
centration increases. Concentration values for the
particular state standard are added to the existing
concentrations for each 6- or 7-day flow increment
(fig. VI.14).
  If the water quality  objective is  to maintain
equilibrium or  stability  of a stream system,  a
typical  conversion  would  use  stream  channel
stability ratings versus sediment rating curves. Ex-
ceedance levels may be inferred from the stability
                                                     The calculation converts water quality objectives
                                                   in mgA to tons/year for comparative purposes only.
                                                   It does not set objectives, but only provides a basis
                                                   for  comparison once water quality objectives are
                                                   set: This allows comparison of suspended sediment
                                                   discharge amount with these objections to deter-
                                                   mine when controls or mitigative measures may be
                                                   applied.  Columns 8 and  9 in worksheet VI. 1 are
                                                   provided for this analysis.
                                                                 Bedload Calculation
                                                   Step 7. Establish Bedload Rating Curve
                                                     Procedure: Measure bedload transport (Ib/sec or
                                                   kg/sec)  using the Helley-Smith bedload  sampler
                                                   concurrent with stream discharge (mVsec or cfs) for
                                                   representative flows.
                                                     The values of measured bedload transport in lb/
                                                   sec or tons/day are evaluated against stream dis-
                                                   charge  in  cfs in the log transformed  regression
                                                   equation:
                                              VI.21

-------
                                1000.0
                              u>
                              E  100.0
                              S   10.0
                              o
                              z
                              o
                              o
                              I-
                              LJJ
                              I    .0
                              til
 Figure VI.15.—Relationship of  sedi-
  ment rating curves to stream chan-
  nel stability ratings, Region 1, USFS
  (Rosgen 1975b).
                                         DATA: 1972, 73, 74
                                         IDAHO PANHANDLE N.F.
                                         LO LO N.F.
                                         CLEARWATER, N.F
                                                          (54)  CHANNEL STABILITY RATING NUMBER
                                                                           I
                                                                                       I
1.0          10.0         100.0
        STREAM DISCHARGE, (cfs)
                                                                      1000.0
            log Bs = b + n log Q            (VI.5)
where:
  log  Bs = logarithm  of bedload transport (Ib/sec
           or tons/day)
      b  = constant representing intercept of the
           regression  line
      n  = constant  representing slope  of the
           regression  line
  log Q  = logarithm of stream discharge (cfs)
  Regression analysis should be used to obtain the
coefficient of determination (r2) and the regression
equation for the bedload rating curve.
  Discussion:  The same variables affecting the
sampling design and representative flow monitor-
ing apply to the bedload rating curves.

Step  8.  Calculate  Pre-Silvicultural  Activity
          Potential Bedload Discharge
  Procedure: Using bedload rating curve (step 7)
and pre-activity excess water distribution (step 2)
for  6- or 7-day time  intervals, calculate  annual
bedload discharge using worksheet VI.2.
'=  S^
                                          (VI.6)
    where:
      Bpre =  pre-silvicultural activity  bedload  dis-
              charge (tons/year)
      1bpre =  measured  bedload  transport  rate
              (Ib/sec) for pre-activity excess water
        T =  duration (days)
        K =  constant to convert  Ib/sec to tons/day
      Discussion:  The procedures  used  here are  the
    same  as in step 4, with the exception that bedload
    is used instead of suspended sediment. Enter the
    total  of  the  pre-silvicultural  activity  potential
    hedload discharge as item E on worksheet VI.3.

    Step 9.  Calculate Total Pre-Silvicultural Activity
              Potential Sediment Discharge (Bedload
              and Suspended Load)
      Add total pre-activity suspended  sediment dis-
    charge (tons/year) (step 4) and total bedload sedi-
    ment  discharge  (step  8), and enter on worksheet
    VI.3 as item K.

    Step  10.  Calculate   Post-Silvicultural  Activity
               Potential Bedload Discharge
      Use worksheet VI.2, columns 1, 5, 6, and 7.
      Procedure:  Compute  rates  using  post-
    silvicultural activity  excess water  (step  2)  and
    bedload rating curves (step 7)  using equation:
                                                VI.22

-------
                                                         WORKSHEET VI.2

                               Bedload sediment quantification for 	
(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days




















(b)
Number
of
days
pre-
si Ivi-
cu 1 tura 1
act i v i ty




















< (c)
Number
of
days
post-
si Ivi-
cu Itural
act i v i ty




















(2)
Pre-
si 1 vicultural
act i v i ty f low
Ve
(cfs)




















(3)
Bedload
transport
rate
'bpre
(tons/day)




















(4)
Total pre-
sl 1 vlcu Itural
activity bed-
load discharge
cols. (3)"
x (1 .b)
n
°pre




















(5)
Post-
si 1 v leu I tural
activity flow
Qpost
(cfs)




















(6)
Bed 1 oad
transport
rate
'bpost
(tons/day)




















(7)
Post-si 1 vicultural
activity bedload
discharge
cols. (6) x (1 .c)
"post




















(Totals are rounded to nearest tenth)
                                                               Total
                                                                                                                   Total
                                                                                                                            tons/yr
Summary:
                               Total pre-si I vicu I tural  activity bedload discharge
                               Total post-si I vicultural  activity bedload discharge
                                                           VI.23

-------
                                WORKSHEET VI.3

                     Sediment prediction worksheet summary

Subdrainage name	 Date of ana|ysis.
     Suspended Sediment Discharge

A.  Pre-siIv[cultural  activity total  potential  suspended sediment
    discharge (total  col. (4), wksht. VI.1) (tons/yr)

B.  Post-si Ivicultural  activity total potential  suspended sediment
    discharge (total  col. (7), wksht. VI.1) (due to streamflow
    increases) (tons/yr)

C.  Maximum allowable potential suspended sediment discharge (total
    col. (9), wksht.  VI.1)  (tons/yr)

D.  Potential introduced sediment sources:   (delivered)

    1.  Surface erosion (tons/yr)               	

    2.  Soil  mass movement  (coarse) (tons/yr)    	

    3.  Median particle size (mm)               	•
    4.  SoiI  mass movement—
          washload (silts and clays)  (tons/yr)
    Bed load Discharge (Due to increased streamflow)

E.  Pre-siIvicuItural  activity potential  bedload discharge (tons/yr)
F.  Post-si IvicuItural  activity potential  bedload discharge (due
    to increased streamflow) (tons/yr)
    Total  Sediment and Stream Channel  Changes

G.  Sum of post-si Ivicultural  activity suspended sediment + bedload
    discharge (other than introduced sources) (tons/yr)
                                                                   (sum B + F)
H.  Sum of total  introduced sediment (D)
       = (D.I  + D.2 + D.4) (tons/yr)

I.  Total increases in potential  suspended sediment discharge

    1.  (B + D.I  + D.4) - (A) (tons/yr)

    2.  Comparison to selected suspended sediment limits
        (1.1)  - (C) (tons/yr)
                                    VI.24

-------
                           WORKSHEET VI .3~conti nued
J.  Changes in sediment transport and/or channel change potential
    (from introduced sources and direct channel impacts)

    1.  Total  post-si IvicuItural activity soil mass movement
        sources (coarse size only) (tons/yr)
    2.  Total  post-si IvicuItural  soil mass movement sources (fine
        or washload only) (tons/yr)

    3.  Particle size (median size of coarse portion) (mm)

    4.  Post-si IvicuItural activity bedload transport (F) (tons/yr)

    Potential  for change (check appropriate blank below)

        Stream deposition 	

        Stream scour      	

        No change         	

K.  Total  pre-siIvicuItural  activity potential  sediment discharge
    (bedload + suspended load) (tons/yr)
L.  Total  post-si IvicuItural  activity potential sediment discharge
    (all  sources + bedload and suspended load) (tons/yr)
M.  Potential  increase in total sediment discharge due to proposed
    activity (tons/yr)
                                                                   (sum A + E)
                                                                   (sum G + H)
                                                              (subtract L - K)
                                      VI.25

-------
            Bpost= (ibpJ(T)(K)
  where:
 Bpost = post-silvicultural activity bedload dis-
         charge (tons/year)
 'bpost = bedload transport rate (Ib/sec)  for post-
         activity excess water
  T   = duration (days)
  K   = constant to convert Ib/sec to tons/day
  Discussion:  The  increase in  bedload sediment
discharge is a function  of increased streamflow
through vegetative  alterations.


                Total Sediment

Step  11. Obtain Introduced  Sediment from Soil
           Mass Movement
  Obtain total potential sediment delivered by soil
mass  movement processes in tons/year (ch. V). Add
to total sediment  discharge,  all sources, step 16.
Record on worksheet VI.3, lines D.2 and D.4.

Step  12. Obtain Total Coarse-Size Sediment from
           Soil Mass Movement
  Obtain total potential  introduced coarse-sized
sediment  delivered  by  soil  mass  movement
processes. Record on worksheet  VI.3, lines D.2 and
J.I.
  Procedure: Subtract the percentage of fines (silts
and clays) from total delivered sediment to obtain
the coarse fragment size  (sands and larger)  (Data
input for step 20).
  Discussion:  This  indicates only the potential of
increased sediment available to a  stream.  Since
sediment  routing  is  not attempted  with  these
procedures,  it is not  possible  to  determine the
amount  of coarse-sized soil  mass  movement
material that would be available to the third order
drainageway  over various  periods. A  certain
amount will go   into  temporary storage.  A
qualitative evaluation in step 21 may provide ad-
ditional interpretations on stream channel impacts
due to the change  in  sediment supply from this
source.

Step  13. Determine Fine Size  Volume from Soil
          Mass Movement
  Procedure: Calculate percent by volume of soil
mass  movement material that is composed of the
fine soil fraction, .0625 mm or smaller — silts and
clays  (washload). Compare output at step  16 —
post-activity total suspended sediment discharge
at the third order stream reach (step 15).
 Step  14. Obtain  Total  Introduced  Suspended
           Sediment (tons/yr) from Surface Ero-
           sion, Chapter IV
   Procedure: Self-explanatory.
   Discussion: Since the assumption is made that
 the  delivered  sediment  from surface erosion  is
 washload (silts and clays),  then  the total volume
 delivered would  be evaluated at the  third order
 reach. These data are used to compare introduced
 sediment to selected limits  (step 15).

 Step  15. Compare Post-Silvicultural Activity
           Total Potential  Suspended Sediment
           (in Tons) to Selected Limits
   Procedure: Add total of suspended sediment in-
 creases from:
   1. Flow related increases  (step 5)
   2. Surface erosion source  (step 14)
   3. Soil mass movement, washload (step 13).
   Subtract  total  of post-activity  tons  from al-
 lowable maximum sediment discharge (S^jx)-
  Discussion: Individual  processes  (surface ero-
sion, soil mass movement, and streamflow) can be
analyzed independent of each other to determine
respective contributions. In this manner, controls
which  relate to specific processes may be properly
recommended where applicable  (tables II.2 to 14,
ch. II).

Step 16. Post-Silvicultural  Activity Total Poten-
           tial Sediment Discharge—All Sources
  Procedure: Total Sediment = 2 [output steps (5)
(10) (11) and (14)] Add total of sediment discharge
(in tons/yr) from:
  1. Suspended  sediment  post-activity  flow
     related  increases  (step 5)
  2. Bedload post-activity  flow related increases
     (step 10)
  3. Soil mass movement volumes (step 11)
  4. Surface erosion source (step 14).
  Discussion:  This  calculation  only  evaluates
potential changes in sediment availability within a
third order watershed. It does not assume that all
eroded material is routed to the  third order reach.

Step   17.  Increase  in  Total  Potential  Sediment
           Discharge From Silvicultural Activities
  Procedure: Subtract total volume  (tons/year) of
pre-activity sediment discharge (step 9) from total
post-activity sediment discharge (step 16).
                                              VI.26

-------
  Discussion: Although the data output represents
a combined total  of all  sources, individual  con-
tributions may be evaluated where needed when
considering  management controls  or mitigative
measures.

Step 18.  Collect Channel Geometry Data for Third
          Order Stream
  Procedure: Measure surface water slope (ft/ft) on
the stream reach where bedload data  is collected.
Also measure stream width for the various flows as
measured in the  establishment  of the bedload
rating curve.
  Discussion: This information is necessary to es-
tablish a sediment transport rate-stream power
relationship  (step 20) for the third order watershed.
It is also required to obtain changes  in sediment
transport rate on first to  third order stream chan-
nels caused by activities which affect either surface
water slope  or bankful stream width (step  19).

Step 19. Evaluate  Post-Silvicultural  Activity
          Channel Impacts
  Procedure: Determine post-activity  changes in-
fluencing stream power  calculations  by surface
water slope  or bankful stream width.  Using post-
activity bankful width  and/or surface  water slope,
revised stream  power  calculations  and resultant
revised  bedload transport rates  for  impacted
stream reaches  (step 20)  may be obtained.
  Discussion: Changes in stream width and/or sur-
face water slope can be  obtained by  field deter-
minations based on the results of similar activities
on  stream   reaches  (i.e.,  upstream  versus
downstream  measured  surface  water  slope  as-
sociated with debris jams indicates relative change
anticipated with similar activities).

Step 20.  Establish Bedload Sediment Transport
          Rate-Stream  Power  Relationship  for
          Third Order Stream Reach
  Procedure: Using width (step 2),  water surface
slope and actual bedload transport  data (step 7),
establish  the relationship:

            log ib = a + b logw            (VI.8)
where:
log ib =  logarithm of measured bedload transport
         rate (Ib/sec/ft)
    a =  intercept of regression line
    b =slope representing regression line
 logo, =  logarithm stream  power (Ib/sec/ft)
  stream power = (62.4 Ibs ft3  X surface water
                  slope  (ft/ft)  X  stream dis-
                  charge (cfs)| -T- stream width
  Use worksheet VI.4 for this calculation.
  Determine the median sediment size in transport
from seiving the bedload sampler catch (Dso). If the
sizes in transport vary as stream power increases,
analyze data separately to develop various particle
size stream power requirements as shown in figure
VI.8 (Leopold and Emmett 1976).
  Discussion: The  purpose  of this calculation is to
develop a local relationship of bedload transport
rate-stream  power to  predict  potential  stream
channel adjustments. If it  is desired to complete
the  same  analysis  on  first and  second order
streams, it will be  necessary to obtain site specific
information  for the respective reaches. This is re-
quired because a flow evaluation is not provided for
the first and second order streams.
  The data  required are:
  1.  Measure  surface water slope (from riffle to
     riffle).
  2.  Measure  bankful stage width (using bankful
     stage as described  by  Williams (1977)).
  3.  Measure  bankful stage depth.
  The reliability of the data will be reduced by ex-
trapolating bedload transport rate data to the first
and  second  order  streams. Extrapolation  is less
reliable because actual changes in bedload particle
size in transport and corresponding stream  powers
are not measured. The processes affecting trans-
port rate, however, are the same;  therefore,  the
reduced reliability may be acceptable. If it is not
acceptable,  measurement of the  first and  second
order reaches is recommended to more accurately
develop the bedload transport rate-stream power
relationships.

Step 21. Qualitative  Determinations of Channel
          Change Potential Based on Introduced
          Sediment  from  Soil Mass Movement
          and Channel Impacts (wksht. VI.5)
  Procedure:
  a.  Determine change  in surface water slope.
  b.  Determine change in bankful stream  width.
  c.  Determine change  in bankful stream  depth.
  d.  Obtain volume of  introduced sediment from
     soil mass movement source  (step 12).
                                              VI.27

-------
                                               WORKSHEET VI.4

                   Bed load transport-stream power relationship for
(1)
Water
surface
slope
S
(ft/ft)





















(2)
Constant
(62.4)
K
(Ib/ft3)





















(3)
Measured
stream
discharge
0
(cfs)





















(4)
Stream
wi dth
W
(ft)





















(5)
Stream
power
cols. (1) x (2) x (3)
col . (4)
(ft/lb/sec)





















(6)
Measured
bed load
transport
rate
'b
(tons/day)





















(7)
Convert bedloac
transport from
tons /day to
ft/lb/sec, [col .
(6) x 2,000]
486,400 x col. (4)
ib
(ft/lb/sec)





















Complete the following analysis:
  a.  Plot value of stream power (u), column (5) on X-axis and values of bed load transport rate
      Pb» column (7)], on double log graph paper.
  b.  Calculate regression equation and coefficient of determination (r^).

-------
                                WORKSHEET VI.5


               Computations for step 21 	
                                             (stream name)



Changes in bed load transport-stream power due to channel  impacts


1.  Potential  changes in channel  dimensions


    a.  Bankful  stage width  (Wpre) 	   (wpost} 	


    b.  Bankful  stage depth  (Dpre) 	   (
    c.  Water surface slope  (Spre)


    d.  Bankful  discharge
where:  QBpre = °-366 + 1-33 log Apre + 0.05 log Spre - 0.056 (log Spre):


        where:  A = cross-sectional  area (a) x (b)  	


                S = water surface slope (c)         	


        Calculate 33 '°9 Apost +0.05 log Spost

                    - 0.056 (log Sposf)2


2.a.  Pre-siIvicuItural activity stream power calculation (wpre)


                  Spre     62*4     QBpre
           u      n.c)  x  (K)  x  (l7d)
            pre
                           d.a)
2.b.  Post-si IvicuItural  activity stream power calculation


                   spost    62-4    QBpost
                   (l.c)   x  (K)  x  (l.d) _
            post	55
                            fpost
                            (l .a)
3.   Calculate post-si IvicuItural  activity bedload transport rate at bankful
    discharge, using post-si IvicuItural activity stream power
                                        VI.29

-------
   e.  Determine  median particle  size  (mm) of
      delivered soil mass movement material.
   f.  Calculate  bankful discharge  on  impacted
      stream reach.

    Procedure for determining bankful discharge:
       (1)  Determine upper limits of the active
           floodplain (Williams 1977).
       (2)  Measure bankful stream width.
       (3)  Measure bankful stream depth.
       (4)  Calculate area (width  X depth).
       (5)  Measure water surface slope.
       (6)  Solve for bankful discharge, Q in equa-
           tion.
log Q =  0.366 + 1.33 log A + 0.005 log S
         - 0.056 (log S)2
                      (Riggs 1976)
(VI.9)
where:
      Q  = discharge (cfs)
      A  = area (ft2)
      S  = water surface slope (dimensionless)
     Extrapolate  bedload transport rate-stream
     power relationships established on third order
     reach to the reach being evaluated.
  h. Calculate maximum bedload transport rate
     using bankful discharge stream power. Com-
     pare to total introduced sediment from  soil
     mass movement source. If introduced sedi-
     ment exceeds transport rate at bankful dis-
     charge, sediment deposition may be expected
     in the stream reach.
   i. Calculate changes in sediment transport rate
     caused by a reduction in surface water slope
     from  debris jams. If revised  stream power
     calculation creates a reduction in sediment
     transport rate, sediment deposition  in  the
     channel may be expected. This assumes there
     is  no reduction  in  sediment  availability
     within the watershed upstream of the reach
     being evaluated.
  Discussion:  These qualitative  evaluations  in-
dicate   relative  potential  for channel  change,
namely deposition or stream  channel aggradation
(longer than 1 year of influence). A numerical in-
dicator is used for this potential change. Long-term
monitoring is necessary  to  provide quantitative
prediction and time series recovery of stream chan-
nels in the interim. These calculations  are recom-
mended when considering management controls
and/or mitigative measures.
                                               VI.30

-------
                                  LITERATURE CITED
Anderson, H. A.  1975. Relative contributions of
  sediment from source areas and transport. Proc.
  Sediment-Yield Workshop, Oxford, Miss. U.S.
  Dep. Agric., Agric. Res. Serv. Rep. ARS-S-40.
  285 p.

Bagnold, R. A. 1966. An approach to the sediment
  transport problem  from general  physics.  U.S.
  Geol.  Surv. Prof. Pap.  No. 422-1. Washington,
  D.C. 37 p.

Bernath, S. A.  1977. Co-variance analysis of the
  channel stability/sediment rating curves. Un-
  publ.   Rep.,  U.S.  Dep.  Agric.  For. Serv.,
  Arapaho/Roosevelt Natl. For., Fort Collins, Colo.

Emmett, W. W. 1974. Sediment measurements in
  the Sawtooth Range, Idaho. U.S. Geol. Surv.
  personal communication.

Emmett, W. W. 1975. The channels and waters of
  the upper Salmon River area, Idaho. U.S. Geol.
  Surv.  Prof.  Pap. 70-A.

Fames,  P. A.  1975. Preliminary report  —
  suspended sediment measurements in Montana.
  U.S. Dep. Agric., Soil Conserv. Serv., Bozeman,
  Mont.

Flaxman, E. M. 1975. The use of suspended sedi-
  ment  load  measurements and  equations for
  evaluation of sediment  yield in the west. Proc.
  Sediment-Yield Workshop, Oxford, Miss.  U.S.
  Dep. Agric., Agric. Res. Serv. Rep. ARS-S-40.
  285 p.

Fredriksen, R. 1977.  Sediment data from H. J.
  Andrews  experimental  watershed.  U.S. Dep.
  Agric. For. Serv., Pac. Northwest For. and Range
  Exp. Stn., Corvallis,  Oreg. Unpubl. data.

Guy, H., and V. Norman. 1970. Field methods for
  measurements of fluvial sediment. Appl.
  Hydraul., Book 3, Chapter 2.  59  p. U.S. Geol.
  Surv.

Helley, E. J., and W. Smith. 1971. Development
  and calibration of a pressure-difference bedload
  sampler. U.S. Geol. Surv.  Surv. Open-File Rep.
  18 p.

Holstrom, T.  1976.  Sediment rating curves for
  western Wyoming.  Unpubl. Rep. Utah State
  Univ., Logan.
 Lane,  E.  W.  1955.  The  importance  of fluvial
   morphology in hydraulic engineering. Proc. Am.
   Soc. Civ. Eng. 8(745).

 Laven, R. A. 1977. Sediment rating curves related
   to channel  stability. Unpubl. Rep. U.S. Dep.
   Agric.  For Serv., Six Rivers Natl.  For., Eureka,
   Calif.

 Leaf, C. F. 1974. A model for predicting erosion and
   sediment yield from secondary forest road con-
   struction. U.S. Dep. Agric. For. Serv. Res. Note
   RM-74. 4 p. Rocky Mt.  For.  and Range Exp.
   Stn., Fort Collins, Colo.

 Leopold, L. B., and W. Emmett. 1976.  Bed load
   measurements, East Fork River, Wyoming. Proc.
   Natl. Acad. Sci. USA, Vol. 74, No. 7. p. 2644-
   2648.

Leopold,  L. B., M. G. Wolman, and J. P. Miller.
   1964. Fluvial processes in geomorphology. 522 p.
   W. H.  Freeman and Co.,  San Francisco.

Megahan,  W.  F.  1974.  Erosion over  time  on
   severely disturbed  granitic soils: a model. U.S.
   Dep. Agric. For. Serv. Res. Pap. INT-156. 14 p.
   Intermt.  For.  and  Range Exp.  Stn., Ogden,
   Utah.
Megahan, W.  F. 1978. Bedload transport rates.
  Central Idaho Streams. U.S.  Dep. Agric. For.
  Serv., Intermt. For and Range Exp. Stn., Boise,
  Idaho.

Pfankuch, D. J. 1975. Stream reach inventory and
  channel stability evaluation.  U.S. Dep. Agric.
  For. Serv., Reg. 1,  Missoula, Mont. 26 p.

Piest, R.  F., J. M. Bradford, and R. G.  Spomer.
   1975.  Mechanisms  of  erosion  and  sediment
  movement from  gullies. Proc. Sediment-Yield
  Workshop,  Oxford, Miss.,  U.S.  Dep. Agric.,
  Agric. Res. Serv. Rep. ARS-S-40. 285 p.

Platts,  W.  S., and W. F.  Megahan. 1975. Time
  trends  in riverbed sediment  composition in
  salmon  and steelhead spawning areas.  South
  Fork River, Idaho. In North Am. Wildl. Manage.
  Inst., Washington,  D.C. p. 229-239.

Riggs, H. C. 1976. A simplified slope-area method
  for estimating flood discharge in natural chan-
  nels. J. Res.  U.S. Geol. Surv. Vol. 4. p. 285-291.
                                             VI.31

-------
Rosgen, D. L. 1973.  The  use  of  color infra-red
  photography for the determination of sediment
  production, fluvial  processes  in  sedimentation.
  Proc. Hydrol. Symp. Natl. Res. Counc.,  Ed-
  monton, Alberta, Can.

Rosgen, D. L. 1974. Bedload transport data.  Un-
  publ. U.S. Dep. Agric. For. Serv., Idaho Panhan-
  dle Nat. For., Coeur d'Alene, Idaho.

Rosgen,  D.  L. 1975a.  Preliminary  report —
  procedures for quantifying sediment production.
  U.S. Dep. Agric. For. Serv., Sandpoint,  Idaho.

Rosgen, D. L. 1975b. Suspended sediment data and
  analysis  80 streams. 1972-1975  unpubl. data.
  U.S. Dep.  Agric. For. Serv., Idaho Panhandle
  Nat. For., Coeur d'Alene, Idaho.

Rosgen, D. L.  1975c. Watershed response rating
  system. Forest hydrology, part II. Reg. 1,  U.S.
  Dep. Agric. For. Serv., Missoula, Mont.

Rosgen, D. L. 1977a. Water quality data. Unpubl.
  U.S. Dep. Agric. For. Serv., Arapaho/Roosevelt
  Natl. For., Fort Collins, Colo.

Rosgen, D. L. 1977b. Validation of sediment rating
  curves and channel stability analysis procedures.
  Unpublished data for EPA contract #EPA-IAG-
  D5-0660. U.S. Dep.  Agric.  For.  Serv.-EPA.
  Washington, D.C.
 Shen. H. W. 1976. Some notes on alluvial channels.
   Short course on the fluvial system, Colo. State
   Univ.,  Fort Collins.

Shen, H. W., and R. M. Li. 1976. Water sediment
  yield. Stochastic approaches to water response.
  H. W. Shen, ed., Fort Collins, Colo.

Striffler, D. A.  1963. Suspended  sediment con-
  centrations in a Michigan trout stream as related
  to watershed characteristics. Proc. Fed. Inter-
  Agency Sediment Conf., U.S. Dep. Agric., Agric.
  Res. Serv., Misc. Publ.  No. 970. 933 p.

Sundeen, K. D. 1977. Estimating channel sediment
  yields from a disturbed watershed. Unpubl. Rep.
  U.S. Dep. Agric. For. Serv., Fort Collins, Colo.

U.S. Department of Agriculture, Forest  Service.
  1975. Forest  hydrology, part II. Reg. 1, Missoula,
  Mont.

U.S. Department of Agriculture, Forest  Service.
  1977. Non-point water quality modeling wildlife
  management.  A  state-of-the-art  assessment.
  EPA-IAG-D5-0660. Washington, D.C.

Williams,  G. P. 1977. Bankful discharge of rivers.
  U.S. Geol. Surv., Open  File Rep., Denver.
                                              VI.32

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                                       APPENDIX VI.A
                           EXAMPLES  OF  CHANNEL STABILITY
                                              RATINGS
Figure VI.A. 1.—Stream channels in-
  dicative of a stable channel due to
  resistant bed and bank materials.
Figure VI.A.2,—Stream channels in-
  dicative of a stable channel due to
  resistant bed and bank materials.
                                               VI.33

-------
Figures  VI.A.3.  -  VI.A.5.—Stream
  channels indicative of stable chan-
  nel due to resistant bed and bank
  materials.

                                                       VI.34

-------
                                         ,*"
                         Figures VI.A.6. - VI.A.8.—Highly un-
                           stable channels or channels having
                           poor stability ratings are generally
                           associated  with  easily detached
                           bank and bed material where chan-
                           nel erosion is significant.
VI.35

-------
       Figure VI.A.9,—Stability and associated sediment supply af-
        fected by organic debris which increase sediment storage
        with resultant channel changes and bank erosion.
       Figure VI.A.10.—Stability and associated sediment  supply
         affected by organic debris. Excessive deposition and as-
         sociated increased sediment storage occurs with resultant
         channel changes, bank erosion and other changes.
VI.36

-------
Figure VI.A.11.—Change* in stability
  due to increases in sediment supply
  from road crossing*.  Such  In-
  troduced sediment sources can ex-
  ceed the carrying capacity of  the
  stream.
             Figure VI.A.12.—Soil mas* movement, due to debris avalanche processes, deliver excessive
               amounts of sediment to the stream. This will often change the stream stability and associated
               supply-energy relationship.
                                                     VI.37

-------
Figure  VI,A.13.—Soil ma*» movement, due to slump-earthflow processes,
  deliver excessive amounts of sediment to the stream. This will often change
  the stream stability and associated supply-energy relationships.
                            VI.38

-------
                                      APPENDIX VLB
  RELATIONSHIPS BETWEEN SEDIMENT RATING CURVES AND CHANNEL STABILITY
  To  provide  a link between the morphological
characteristics of stream channels, as determined
by  the  channel stability  rating  procedure
(Pfankuch  1975),  and  sediment  rating curves,
regression analyses were made on over 80 streams
in northern  and central Idaho and northwestern
Montana  involving sediment rating curves and
channel stability ratings. The relationship is shown
in figure VI.B.l (Rosgen 1975b).  Correlation coef-
ficients (R2)  were 0.94 for the "good and excellent"
(38 to 76), 0.91 for the "fair channel stability" (77
to 114), and 0.94 for the "poor or unstable" chan-
nels (115 to  132). A covariance analysis was con-
ducted (Bernath 1977) indicating  highly significant
correlations  when comparing  stability ratings for
various populations.  The  F  values  were highly
significant at the 0.01 level.
  Since then,  work conducted in California has
shown widespread application of  this  technique
where 27 streams with sediment rating curves were
evaluated using the same stability procedures (fig.
VI.B.2). Concentrations for the same flows are con-
siderably higher in the California streams, but the
stability  evaluation provides a comparison  of the
different regression constants and stability ratings
within a given locale using the  same procedures
(Laven 1977). Similar relationships are indicated
in figure VI.B.3 where sediment rating curves were
related to  stability ratings in Colorado  (Rosgen
1977b).
  Additional validation of this  procedure has been
conducted  in Wyoming,  Oregon,  New  Mexico,
North Carolina, New  Hampshire,  Vermont,  and
Virginia;  tentative results  indicate that  this
procedure applies to many areas other than  where
it  was developed  (Rosgen 1977a). This success  is
due to the application of the procedures  (process
related) rather than extrapolation of actual curves
or regression  equations from region to region. The
use of this procedure demands  the development  of
                 1000.0
                  100.0
               o
               s
               LU
               O
               o
               O
               I-
               LU
              LU
              CO
                  10.0
                          DATA: 1972, 73, 74
                          IDAHO PANHANDLE N.F
                          LO LO N.F.
                          CLEARWATER, N.F.
                                         (54)  CHANNEL STABILITY RATING NUMBER
                                                          I
                                                                      I
                                 1.0          10.0        100.0
                                         STREAM DISCHARGE, (cfs)
                  1000.0
                Figure VI.B.L—Relationship of sediment rating curves to stream channel stability
                 ratings, Region 1, USFS (Rosgen 1975b).
                                            VI.39

-------
1,000,000-
 100,000—


^3>
z
o
r; 10000—
DC
I-
z
LU
o
z
o
o
    uooo—
 h-
 z
 LU
 Q
 LU
 

 Q
 LU
 Q
 Z
 LU
 Q.
 C/)
 D
     100—
      10-
            Numerical
            Stability
            Ratings
         01
                        I              I              I
                       1.0             10            100
                             STREAM DISCHARGE, (CSM)
1,000
10,000
       Figure VI.B.2.—Relationship of channel stability ratings to sediment rating curves in the Redwood Creek
        drainage, California (Laven  1977).
                                         VI.40

-------
1000.0
             i  1 JTJIfflo     i   i
                          STREAM DISCHARGE, (cfs)
I  I  I 11
567 89100.0
  Figure VI.B.3.—Relationship of channel stability ratings to sediment rating curves for streams in the central
    Rocky Mountain region. (Rosgen 1977a).
                                    VI.41

-------
local curves based on actual sediment rating curve
data. Once this step has been completed, informa-
tion can be obtained  from many miles of stream
reach upstream or adjacent to where sediment data
have  been collected. Thus, the channel stability
procedure, if  used in a  consistent  comparative
analysis over a wide range of stream types, can be
used to infer the regression constants of the sedi-
ment rating curves. This would not be as accurate
as  actual measurements  on 100  percent of the
stream reaches being evaluated in a  subdrainage;
however,  time and  financial constraints  might
justify this approach once local validation has been
accomplished. Potential shifts in stability as a
result of direct sediment introduction may be infer-
red through the use of channel  stability — sedi-
ment rating curve relationships in a  given locale.
  The "stability threshold" of streams can be in-
terpreted as the lines between the major stability
classes as shown in figure VI.B.l. This interpreta-
tion would be used where either actual or proposed
potential sediment  discharge,  as calculated, could
be compared to that sediment discharge using the
maximum concentrations for the stability class and
pre-activity  seasonal distribution of excess water.
These are based on measured data in the develop-
ment of these relationships. If potential introduced
sediment is anticipated during periods  of lower
flow,  a comparison may  be made,  utilizing less
than bankful stage discharge. If the increased sup-
ply is higher  than the maximum  sediment dis-
charge for that flow condition, a stability change or
associated shift in  sediment rating curve  may
occur.
                                             VI.42

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                                      APPENDIX VI.C
                     TIME SERIES ANALYSIS-RECOVERY PROCEDURE
  It is often desirable to determine the duration of
sediment impacts in a stream system. Little work
is available which sets time series recovery for sedi-
ment rating curves, although observations indicate
relative  rates of recovery which vary considerably
between streams. It is not possible to predict this
recovery at this time; however, a procedure can be
applied  once  channel morphological data  are col-
lected and pre- and post-sediment rating curves are
measured.
  Time  recovery  for streams using the sediment
rating curve approach may be shown as:
  A. Pre-silvicultural  activity  sediment  rating
     curve  or  baseline  characterization
     relationship.
             log Y = b + n log Q        (VI.l)
where:
  log Y =  logarithm  of pre-silvicultural  activity
           suspended  sediment  concentration
           (mg/1)
      b =  pre-silvicultural  activity  regression
           constant  expressing  intercept of the
           regression line
  log Q =  logarithm of pre-silvicultural  activity
           instantaneous  stream  discharge in
           cubic feet per second
      n  =  pre-silvicultural activity regression ex-
           ponent expressing slope of the regres-
           sion line
  B. Post-silvicultural  activity  relationship ex-
     pressing the time series recovery.


        Y* = (b*e-Yt) (Q) <•>•»-«)       (VI.C.l)
where:
  Yt* = post-silvicultural activity  sediment con-
         centration (mg/1) for a specified time fol-
         lowing activity
    b  = post-silvicultural activity regression con-
         stant expressing  intercept  of the regres-
         sion line
    e  = base of natural logarithms
   -Y = negative  exponent  expressing
         relationship of recovery of  intercept
    Q  = post-silvicultural activity instantaneous
         stream discharge (ft3 per section)
    n* = post-silvicultural activity regression ex-
         ponent expressing slope of the regression
         line
   -z  = negative exponent  expressing  recovery
         relationship of slope
    t   = time (years) since initial disturbance
   The relationships  can be used to determine the
rate of decline of the sediment rating curve follow-
ing  disturbance.  Data  requirements include  the
availability of measured pre- and post-silvicultural
activity  rating curves  on  streams  to calculated
values of Yt and zt for similar stream systems for
various years.
   Models  which determine  potential  "time-
trends" in erosion and sedimentation  are published
and have been used in the central  and northern
Rocky Mountains (Megahan 1974  and Leaf 1974).
Sediment  reduction  resulting from roads  was
primarily  addressed where  vegetative  recovery
greatly reduced delivery to a stream.
   Before this stream  channel-time  recovery  ap-
proach can be applied, stream morphological data
will be needed prior to and following  treatments of
various streams to determine what  variables  are
responsible for the shift  in  the  sediment rating
curve. Before adjusted values of Yt and zt  are
available,  qualitative   broad  interpretations  of
recovery are presently all that can be applied.
                                              VI.43

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             Chapter VII
       TEMPERATURE
this chapter was prepared by the following individuals:
             John B. Currier
        with major contributions from:
             Dallas Hughes
                  vn.i

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                             CONTENTS
                                                                Page

INTRODUCTION	  VE.l
THE PROCEDURE	  VH.2
  SOURCES OF ENERGY INFLUX CONTRIBUTING TO INCREASED
   WATER TEMPERATURE	  VH.2
    Net Radiation, NR	  VU.2
    Advective Energy Flux, Ad 	  VH.2
    Conductive Energy Exchange Between Streambed Material And Water, Cd .  VII.2
    Evaporation And Condensation, E	  VH.3
    Convective Energy Exchange, Cv	  VII.3
  BROWN'S MODEL: ESTIMATING MAXIMUM POTENTIAL
   TEMPERATURE INCREASE	  VE.3
  PROCEDURAL DESCRIPTION	  VLL3
    Determination Of Incident Heat Load, H 	  VIf.3
    Determination Of Discharge, Q	  VEL14
    Determination Of Exposed Surface Area Of Flowing Water, A 	  VII. 14
    Determination Of Maximum Potential Daily Temperature Increase, AT  .  VII.16
    Evaluation Of Downstream Temperature Increases	  VII.18
     Total Increase In Water Temperature	  VII.18
     Reduction In Water Temperature Due To Groundwater Inflow	  VII.18
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS	  VH.20
LITERATURE CITED 	  VH.21
APPENDIX VH.A: VALIDATION OF BROWN'S MODEL 	  VH.22
APPENDIX VII.B: STREAMSIDE SHADING	  VH.24
  TOPOGRAPHIC SHADING 	  VH.24
  VEGETATIVE SHADING	  VH.24
APPENDIX VII.C: WATERSIDE AREAS	  VH.27
  COMMERCIAL TIMBER 	  VDL27
  STRIP WIDTH	  Vn.27
APPENDIX VH.D: GENERAL RELATIONSHIPS BETWEEN LIGHT
  INTENSITY OR TRANSMISSION OF SOLAR RADIATION
  AND VEGETATIVE COVER	      VE.29
                                VH.ii

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                             LIST OF EQUATIONS


Equation                                                                    Page

VII.l   AH = NR±Ad±Cd±E±Cv   	   VII.2
\7TT rt     	   T"\ rfl  i  TA rp
Vll.^   ATfl = Uili+Uzlz     	   vn 2


VH-3   AT =  — 0.000267   	   VJJ.3

VII.3a        A adjustedH adjusted
        AT =  —'	  0.000267   	   VII.16
                     Q
VII.4             measured average stream width
               sine  | azimuth stream  azimuth sun |
VIJ.5         height vegetation
             tangent  solar angle
VH.6   H adjusted  = [% WH] + [%B (1.00-C) H]  	   VII.14
VII.7a  Atotal=LW    	   VII.15
VII.7b  Ashadebrush = LW(% stream shaded by brush only)  •	   VII.15
VII.7c  Apresentiyexp0sed= (Atotai_ Agj,adebrush)
                        (% transmission through existing vegetation)   	   VII.16
VII.7d  Aadjusted = Atotai — A exposed pre-silvicultural activity   	   VII.16
VII 8        D T  -I- TO T
        Trj=_M_M	—    	   VH.18


VH.9        DGTG+DTTT
        TD	—   	   Vn.19
                                     VJJ.iii

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                              LIST OF FIGURES
Number                                                                   Page

VII.l    Flow  diagram showing the sequence  of steps and data required for
          evaluating the maximum potential daily temperature increase in °F.   VII.4
VII.2    Solar ephemeris for 35° N latitude	  VII.6
VH.3    Solar ephemeris for 40° N latitude	  VII.7
VII.4    Solar ephemeris for 45° N latitude	  VII.8
VII.5    Solar ephemeris for 50° N latitude	  VII.9
VII.6    Use of a solar ephemeris	  VII.10
VII.7    Hourly values (BTU/ft2-min) for net solar radiation above water sur-
          faces on clear days between latitudes 30° N and 50° N for several solar
          paths	  VII.13
VII.8    Determination of net hourly solar radiation using noon angle of 72° .  VII. 13
VII.9    Correction factor for the heat-sink effect of bedrock streambeds	  VII. 14
VII. 10  Transmission of solar radiation as a function of stem density and crown
          closure 	  VII. 17
VII.l 1  Components of the mixing formula for evaluating the downstream im-
          pact of increased water temperature caused by silvicultural activities
          upstream	  VII.18
VII.12  Components of the mixing formula for evaluating the impact of ground
          water temperature and inflow on reducing temperature increases due
          to silvicultural activities upstream	  VII. 19
Vn.B.l  Low-growing shrubs and brush adjacent to water a course may provide
          adequate shade, while taller vegetation is necessary further from the
          stream  	  VH.25
VII.B.2  Position of the sun in relation to the riparian vegetation determines the
          time and  extent of vegetative shading	  VII.25
VII .B .3  Orientation of the sun with the stream determines the length of shadows
          necessary  to completely shade the water surface 	  VII.26
VII.C.l  The relation between waterside area width and angular canopy density   VII.27
VII.C.2  The relation between angular canopy density  (ACD) and heat blocked
          (AH)	  Vn.28
VII.D.1  Transmission of solar radiation as a function of stem density and crown
          closure 	  VH.30
                                      VH.iv

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                               LIST OF TABLES
Number                                                                   Page
VII.l    Variation of solar angle and azimuth with time of day 	   VII.5
VII.2    Computation of stream's effective width (EW) and vegetative shadow
          length (S) based upon stream azimuth, solar azimuth, and solar angle   VII.12
VTI.A.l  Summation of  validation test using data from Fernow Experimental
          Watershed, Parsons, West Virginia  	   VII.22
VII.D.l  Effects of stand density removal on light intensity	   VII.29
VII.D.2  Effects of tree spacing on light intensities	   VII.29
VII.D.3  Percent light intensity through small- and large-crown trees 	   VII.29
VII.D.4  Percent light intensity through eastern conifers	   VII.29
VII.D.5  Percent light intensity through conifer plantations 	   VII.29
VII.D.6  Stand basal area  and equivalent solar loading beneath the canopy ..   VII.29
                                     vn.v

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                                     INTRODUCTION
  The temperature of small headwater streams of
forested areas is an important determinant of
overall water quality. Temperature acts not only to
control  the metabolic  rates  and  functions of
aquatic  biota but  also serves  to maintain com-
munity structure. Change in temperature affects
species composition. Microorganisms at the base of
the food chain may be directly affected which even-
tually will affect all higher organisms in the food
pyramid.
  Water temperature  changes  may be  either
beneficial or detrimental. A moderate temperature
increase in  streams that are cooler than optimum
could increase productivity and have a beneficial
effect on  the aquatic environment.  However
streams having  temperatures  that approach
critical threshold limits during the summer months
may exceed these limits and have a detrimental ef-
fect  on  aquatic  organisms.  In addition, winter
stream temperatures may be decreased by canopy
removal. Exposure  of  the water  surfaces could
result in greater convectional heat loss from the
water to the atmosphere.
  Increased stream temperature affects fish pop-
ulations  in several  ways, many  of which are
detrimental. High temperature  kills fish directly,
decreases the  dissolved oxygen  (DO) concentra-
tion, increases the susceptibility of fish to disease
by  increasing  bacteriological  activity, affects
availability of food, and alters feeding activities of
fish.  Increased  stream temperatures  indirectly
alter  community  composition   by  providing a
habitat favorable to warm water species.
  There are numerous publications that relate the
impacts  of  timber  harvesting  to stream
temperature and subsequent effects on fish popula-
tions  (Eschner  and Larmoyeux  1963, Brown and
others 1971). Their studies show that removal of
shading vegetation as a result of  harvesting can in-
crease stream  temperatures because  of increased
exposure  to solar radiation. The magnitude of the
impact is  a function of the amount of critical
canopy removed, duration of exposure, streambed
material, area exposed, stream  discharge, initial
water temperature, and groundwater influx (Stone
1973).  Cloud cover is not considered since  max-
imum potential daily temperature increase is being
evaluated.
                                             VH.l

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                                    THE PROCEDURE
      SOURCES OF ENERGY INFLUX
            CONTRIBUTING TO
   INCREASED WATER TEMPERATURE
  Removal of stream side vegetation that provides
shade to the water surface can cause significant
stream temperature increases.  Several sources of
energy influx interact and contribute to the net
change  in  temperature  of  a  stream. This
relationship may be expressed in the  following
energy budget  equation  (Brown  1969  and  Lee
1977):
           = NR±Ad±Cd±E±C,
(VH.l)
 where:
   AH = energy manifested by a change in water
         temperature,
   NR = net radiation (incoming-outgoing all
         wave radiation),
   Ad = advective  energy  exchange  due  to
         precipitation, ground water, or tributary
         flows,
   Cd = conductive  energy  exchange between
         streambed material and water,
   E  = evaporation and condensation, and
   Cv = convective energy exchange at water sur-
         face, atmosphere interface.
             Net Radiation, NR
  Brown (1969, 1972) has shown that 95 percent of
the energy influx of small,  completely exposed
streams can be accounted for by net radiation. Net
solar radiation is defined as the algebraic sum of in-
cident and reflected sun and sky shortwave radia-
tion, incident and reflected atmospheric longwave
radiation,  and longwave radiation emitted by  the
water body. It is the principal energy influx con-
trolling the maximum temperature increase in ex-
posed streams. Solar radiation itself is not control-
lable, but the  amount of water surface exposed can
be controlled. Shading by vegetation limits  the
amount of solar radiation received  by the water
course (Reifsnyder and Lull 1965).
          Advective Energy Flux, Aa


  Advective energy flux is the transmission of heat
by horizontal currents through a fluid such as the
atmosphere or water.  In specific situations these
significantly modify temperature increases; for ex-
ample, advective inputs by groundwater normally
decrease  maximum  summer  temperatures.
Groundwater temperatures generally approach the
average  annual air  temperature,  and  so  are
generally cooler than surface water during the sum-
mer months. The magnitude  of this reduction will
depend upon the temperature difference between
the surface and the groundwater, and upon the
volume of groundwater entering the stream as com-
pared to  the volume of streamflow in the surface
water.
  Advective inputs by tributaries  may either in-
crease  or decrease  maximum receiving  stream
temperature depending upon whether the tributary
stream contains warmer or cooler  water.  Like
groundwater, the magnitude of the change in water
temperature of a receiving stream will be deter-
mined  by the temperature  and volume  of  the
tributary flow  compared to the temperature and
volume  of the receiving  stream.  Temperature
changes associated with ground water or tributary
flows can be expressed mathematically by a simple
proportion:
                                                                         D2T
                                                                           22
                                                                                        (vn.2)
                             Di + D2
           where:
             ATa = change in water temperature, receiving
                   stream,
             Di   = discharge, receiving stream,
             Ti   = temperature, receiving stream,
             D2   = discharge, tributary stream, and
             T2   = temperature, tributary stream.
               Conductive Energy Exchange Between
                 Streambed Material And Water, Cd
            In a conductive energy exchange heat is trans-
           ferred through matter by kinetic energy (energy of
           motion)  from  particle  to particle. Stream
                                            VH.2

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 temperatures will vary with streambed  composi-
 tion. Generally, bedrock streambeds will act  as
 heat sinks  with resulting conductive  losses  of
 energy from the water body to the rock (Brown
 1972). Gravel, sand, and fine materials comprising
 streambeds  have  interparticulate  voids  that
 minimize conductive heat losses. The color of the
 rock also influences the magnitude of the conduc-
 tive heat loss. Darker rock will absorb more energy
 than lighter rock.
       Evaporation And Condensation, E


   Evaporation is the principal  process by which
 heat is  lost from the  water  surface. It occurs
 whenever the saturation  vapor pressure of  the
 water is greater than the ambient vapor pressure.
 This happens during  the summer when the water is
 cooler than  the air and, in particular, during  the
 midday  period.  Heat loss  from the  water  via
 evaporation is only a  fraction of the radiant energy
 influx and does not  significantly alter the max-
 imum temperature increases in most small streams
 where  silvicultural   activities  are  conducted.
 However, as the  water  temperature  increases to
 equilibrium, evaporation increases and heat loss
 from the water due to evaporation may exceed  the
 heat influx from net  radiation.
 of a section of stream channel to direct solar radia-
 tion  using  the energy budget  approach. Field
 measurements  showed that net thermal radiation
 accounted for over 95 percent of the energy influx
 to exposed water courses (Brown 1969). (Validation
 of Brown's model is discussed in appendix VILA.)
 The energy term in the initial  model was simplified
 based upon the assumption that net solar radiation
 is the only source of energy to an exposed stream.
 The simplified  model is:
                   AH
             AT = — 0.000267
                    Q
                                     (vn.3)
where:
      AT  =
           maximum   potential  daily
           temperature  increases  expected
           from exposing a section of stream to
           direct  solar  radiation,  in  degrees
           Fahrenheit.
           surface area in square feet of stream
           exposed to direct solar radiation,
           discharge of the stream, in  ftVsec
           incident  heat  load  (net  solar
           radiation) received by the exposed
           water surface in BTU/ft2—min, and
0.000267  = constant required for  unit  conver-
           sion  converts  flow from  ft3/sec to
           Ib/min.
        A =

        Q
        H
        Convective Energy Exchange, Cv
                                                         PROCEDURAL DESCRIPTION
   Convective energy  exchange occurs whenever
 there is a temperature gradient between the water
 mass and air mass. The energy exchange may be
 positive or negative depending upon whether the
 air is warmer or cooler than the water. During
 critical  periods of maximum water  temperature,
 the air mass will usually be warmer than the water
 and will reinforce the radiant energy influx to in-
 crease water temperature.
  Brown's procedure  for determining the  max-
imum  potential daily temperature  increase  in
terms of incident heat load (H), discharge (Q), and
exposed surface area of flowing water (A) follows.
These descriptive paragraphs correspond with the
procedural flow chart organization in figure VII. 1.
   Determination Of Incident Heat Load, H
     BROWN'S MODEL: ESTIMATING
          MAXIMUM POTENTIAL
        TEMPERATURE INCREASE
  Brown (1970,  1972) developed  a  model  for
predicting the maximum potential daily change in
temperature resulting from the complete exposure
  The incident heat load (net solar radiation), H,
received by a water surface is determined by (1) the
maximum solar angle of the sun; (2) the length of
time a given  volume of water will be exposed  to
solar radiation; (3) the amount  of bedrock in the
stream;  and  (4)  the  amount of vegetative and
topographic shading of the water surface. The fol-
lowing steps are involved in computing the incident
heat load.
                                             VH.3

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           LATITUDE SITE
   SELECTION OF SOLAR EPHEMERIS
                                          LENGTH OF STREAM EXPOSED
                                         AVERAGE WIDTH FLOWING WATER
                                          IN EXPOSED STREAM SECTION
       CRITICAL TIME OF YEAR
          -MONTH AND DAY
                                                TOTAL SURFACE
                                            AREA OF FLOWING WATER
          DETERMINATION
         OF SOLAR ANGLE
           AND AZIMUTH
                                        PERCENT FLOWING WATER SURFACE
                                               SHADED BY BRUSH
c
HEIGHT OF ADJACENT VEGETATION
    ORIENTATION OF STREAM
FLOWING WATER SURFACE AREA
      SHADED BY BRUSH
 DETERMINATION OF EFFECTIVE STREAM
     WIDTH AND SHADOW LENGTH
      OF ADJACENT VEGETATION
                                         TRANSMISSION SOLAR RADIATION
                                         THROUGH EXISTING VEGETATION
       MAXIMUM SOLAR ANGLE
                                         SURFACE AREA FLOWING WATER
                                          EXPOSED TO SOLAR RADIATION
C
      PERCENT SLOPE OF
    ADJACENT TOPOGRAPHY
   EVALUATE TOPOGRAPHIC SHADING
    TOTAL SURFACE AREA
  FLOWING WATER EXPOSED
     BY REMOVAL OF ALL
    SHADING VEGETATION
        INCIDENT HEAT LOAD
        NET SOLAR RADIATION)
        PERCENTSTREAMBED
      COMPRISED OF BEDROCK
   ADJUSTED NET SOLAR RADIATION
      FOR BEDROCK STREAMBEDS
                                   C
                                    DISCHARGE




4<

-4

L.
C

                                                                PROCEDURAL STEP
                                                                COMPUTATION OB
                                                                 EVALUATION
                                                              A   fe. ANALYSIS
                                                              ^	W OUTPUT
               MAXIMUM POTENTIAL DAILY TEMPERATURE INCREASE
     Figure VII.1. Flow diagram showing the sequence of steps and data required for evaluating the maximum
                   potential daily temperature Increase in degrees Fahrenheit.
                                   VII.4

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                LATITUDE SITE
   The latitude of the site must be known.  Exact
 latitudinal location to the nearest minute or second
 is not required, as the difference in net radiation
 over two to three degrees of latitude is not signifi-
 cant for this analysis procedure.
      SELECTION OF SOLAR EPHEMERIS
   A solar ephemeris is defined as a table or figure
 that gives the sun's location, angle and azimuth,
 for  each  day.  Four solar  emphemerides  are
 provided (figs.  VII.2   VII.5),  representing four
 latitudes — 35°  N, 40° N, 45° N, and 50° N. Select
 one solar ephemeris  most  appropriate  for  the
 latitude of the site of the silvicultural activity. For
 example, if the latitude of the site is 40- Vz ° N, the
 solar ephemeris for 40° N would be utilized.
      c
CRITICAL TIME OF YEAR —
     MONTH AND DAY
  Select the time of year when stream temperature
 increases are critical. This normally occurs during
 the summer months when the stream is lowest and
 heat influx is greatest.
  Using the previous example, locate the declina-
 tion in the solar ephemeris for 40° N latitude (fig.
 VII.3) that corresponds to the date when maximum
 water temperature increase  is anticipated. If the
 critical  period  is the  second week in July, the
 declination would be +21-l/2°. Interpolate between
 given declination lines for dates other  than  those
 given. For the  declination of the second week  in
 July, interpolate between declinations +23°27' and
 +20°  (June  22  and July 24,  respectively).
         DETERMINATION OF SOLAR
            ANGLE AND AZIMUTH
                                          the stream depends  on the  solar  angle and
                                          azimuth. As the solar angle increases, more radiant
                                          energy  reaches  the water surface and there is a
                                          reduction  of  reflected radiation.  Brown (1970)
                                          developed curves for net incoming (shortwave and
                                          diffuse) solar radiation (BTU/ft2-min) based upon
                                          solar angle and reflectivity. He determined that
                                          heat might be  added  to a  stream by  incoming
                                          longwave radiation; however, back radiation from
                                          the water was  about  the same  magnitude.
                                          Therefore,  the net change in  stream  heat from
                                          longwave radiation is assumed  to be zero. Solar
                                          angle and azimuth, of course, depend upon season,
                                          time of day, and latitude.
                                            Continuing with  the same  example, with  a
                                          declination +21-1/2°,  determine the azimuth and
                                          solar angle  for various times during the day from
                                          the solar ephemeris  (fig.  VII.6)  and record  the
                                          values as shown in table VII. 1.  Azimuth readings
                                          are found along the outside of the circle (fig. VII.6)
                                          and are given for every 10 degrees. Solar angle (i.e.,
                                          degrees above the horizon) is indicated by the con-
                                          centric  circles. The time is indicated above  the
                                          +23°27' declination line and is given in hours, solar
                                          time.
                                                   Table VI 1.1.—Variation of solar angle and azimuth with time of
                                                                         day1
Daylight savings
time
12:30
1:00 (solar noon)
1:30
2:10 (oriented with stream)
2:30
2:45
3:10
angle
70
72
70
68
65
60
55
Solar
azimuth
155
180
205
225
235
240
245
  Maximum radiation will occur during the mid-
day hours on clear days. The heat load received by
                                           1See "Chapter VIII: Procedural Examples" for worksheets cor-
                                          responding to data appearing in this chapter's tables and figures.
                                            To determine the solar angle  and azimuth that
                                          would occur at 12:30 p.m. daylight savings time:
                                          follow along the +21- Vz° declination line that is in-
                                          terpolated between the +20°  and  +23°27' line.
                                          Locate the point that is equal distance between the
                                          11:00 a.m. (12:00 a.m. daylight  savings time) and
                                          noon (1:00 p.m. daylight savings time) time inter-
                                          val. This point represents 12:30 daylight savings
                                          time.
                                              VII.5

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35°  N.
                                 350
NORTH
                                                            30
           NW
                                                                40
                              NE
                                                                         120
           SW
               220
                              SE
                    210
                                                           150
                           200
                                       SOUTH  '70
              160
                                                         Decli-
                                                        nation         Approx. dates
                                                        + 23° 27'    Tune  22
                                                        + 20°        May 21. July 24
                                                        + 15°        May 1, Aug. 12
                                                        + 10°        Apr. 16, Aug. 28
                                                        +  5°        Apr. 3. Sept. 10
                                                           0'        Mar. 21,  Sept. 23

                                                        -  5°        Mar. 8. Oct. 6
                                                        -10°        I.'eb. 23, Oct. 20
                                                        -15°        Feb. 9, Nov. 3
                                                        -20'        Jan. 21, Nov. 22
                                                        -23'27'    Dec. 22
                        Figure VII.2.—Solar ephemerk for 35° N latitude.
                                       vn.e

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40°  N.
       a50   NORTH   |0
340. —~r	5
                    330
           NW
                   210
                          200
                                 190   SdUTH  170
                                                        Decli-
                                                        nation         Approx. dates
                                                       +23° 27'    Tune  22
                                                       + 20°        May 21, July 24
                                                       + 15°        May 1, Aug. 12
                                                       +10°        Apr. 16, Aug. 28
                                                       +  5"        Apr. 3,  Sept. 10
                                                          0°        Mar.  21, Sept. 23

                                                       — 5"        Mar.  8,  Oct. 6
                                                       -10°        Feb. 23, Oct. 20
                                                       —15°        Feb. 9, Nov. 3
                                                       —20'        Tan. 21, Nov. 22
                                                       -23' 27'    Dec. 22
                        Figure VII.3.—Solar ephemeris for 40° N latitude.
                                      vn.?

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45°  N.
                          340
                                350
                         NORTH
                                        20
                    330
                                             30
           NW
              320
                                                  40
                                                       NE

                                                       50
                                                                        60
         230

           SW
/
 220
  \
140
 130

SE
                   210
                                                          150
                          200
                                 190  SOUTH  170
                                       160
                                                        Decli-
                                                        nation
                                                        + 23' 27'
                                                        r .W
                                                        H5-
                                                        + 10*
                                                        +  5"
                                                           0°

                                                        -  5°
                                                        -10*
                                                        -15°
                                                        —20°
                                                        —23° 27'
                                                         Approx. dates
                                                        June 22
                                                        lay  21.  Tuly  J4
                                                       May  1, AUJJ.  U
                                                       Apr.  16, Aug.  28
                                                       Apr.  3,  Sept.  10
                                                       Mar. 21, Sept. 23

                                                       Mar. 8,  Oct.  6
                                                       Feb.  23, Oct. 20
                                                       Feb.  9, Nov. 3
                                                       Tan.  21, Nov.  22
                                                       Dec.  22
                        Figure VII.4.—Solar •prwiMfi* for 45° N latitude.
                                       vn.s

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50"  N.
                          340
                       350
                             NORTH
                                            20
                     330
                                                 30
 NW

310
 320
\
                                                                      NC
       300
            sw
          210
                                                            150
                200
                                  190   SOUTH  170
                                                      160
                                                           Decli-
                                                          nation
                                                          4 23* 27'
                                                          •r .!<)"
                                                          -MS"
                                                          4-10*
                                                          4- 5"
                                                            0°

                                                          — 5°
                                                          -10'
                                                          -15°
                                                          —20°
                                                          —23' 27'
                                                              Apprux. dates
                                                           June  22
                                                           May 21, July J4
                                                           M.iy 1, Aug.  1.!
                                                           Apr. 16, Aug. 28
                                                           Apr. j, Sept. 10
                                                           Mar. 21,  Sept. 23

                                                           Mar. 8, Oct. 6
                                                           Feb. 23, Oct. 20
                                                           Feb. 9, Nov. 3
                                                           Jan. 21, Nov. 22
                                                           Dec. 22
                         Figure VII.5.—Solar ephemerb for 50° N latitude.
                                         VH.9

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40°  N.
        350   NORTH
340^	r-~f~~
                                                          20
                                                                30
                                                                                      14 July
                                              14 July
                                 Decli-
                                 nation
                                + 23' 27'
                                + 20°
                                + 15°
                                + 10°
                                +  5°
                                   0"
                                                            — 10°
                                                            -15°
                                                            —20"
                                                            -23* 27'
   Approx. dates
Tune  22
May  21. July 24
May  1,  Aug.  12
Apr.  16, Aug. 28
Apr.  3,  Sept. 10
Mar.  21,  Sept.  23

Mar.  8,  Oct.  6
Feb.  23,  Oct.  20
Feb.  9,  Nov.  3
Jan.  21,  Nov. 22
Dec.  22
     Figure VII.6.—Use of the solar ephemeris given the following illustrative data: latitude of 40-1/2° N, second
      week in July, and 12:30 p.m. daylight savings time.
                                         VII.10

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  The solar angle is determined by noting where
the point established above  (12:30 p.m. with  a
declination of +21-Va0) occurs  in respect to  the
solar angle lines present on figure VII.6. The solar
angle lines are represented as concentric circles and
range from 90° at the center to 0° at the periphery.
The point established above falls on the 70° line;
therefore, the solar angle is equal to 70°.
  The solar azimuth is determined by noting where
the point established above occurs in respect to the
solar azimuth lines that radiate out from the center
of the circle. The  point falls midway between the
150° and 160° lines;  therefore, the solar azimuth
equals 155°.
  More points should be selected about the midday
period when solar radiation is at the greatest inten-
sity as opposed to the early morning and/or late
afternoon when solar radiation is less.
     HEIGHT OF ADJACENT VEGETATION
          ORIENTATION OF STREAM
  The height of vegetation adjacent to the stream
 effects the shading of the stream. Taller vegetation
 casts longer shadows and so can be further from the
 stream and still provide shade. The orientation of
 the stream azimuth in respect to the sun also deter-
 mines  the length of shadow. For a more detailed
 discussion of these relationships, refer to  appendix
 VH.B.
        DETERMINATION OF STREAM
  EFFECTIVE WIDTH AND SHADOW LENGTH
         OF ADJACENT VEGETATION
  Evaluate the orientation of the sun (i.e., solar
angle and azimuth determined previously, table
VII.l), with the stream and determine what vegeta-
tion exists that shades the stream. To do this, com-
pare stream effective width with  shadow length.
Determine the maximum solar angle (i.e., max-
imum radiation influx to stream) that will occur
when the stream is exposed due to the silvicultural
activity.
  Assuming a stream azimuth of 225° and a height
of 70 feet for vegetation adjacent to the stream, the
following numerical  computations  illustrate  how
stream effective width and shadow length can be
evaluated.
  The direction the shadows fall across the stream
will determine effective width of the stream (for a
discussion of effective width, see appendix VII.B,
"Streamside Shading").
  Effective width is computed using the following
formula:
  EW =
   measured average stream width
sine I  azimuth stream   azimuth sun
                                        (VH.4)
  The azimuth of the particular stream used for
this illustration is 225°. This value (EW) varies
depending on the time of day. For example, at
12:30 p.m. (table VII.1), EW would be equal to:
                                                       EW =
                                                                       1.5 ft
                                                                sine I  225°  - 155°
                                 = 1.6 ft
  The absolute value of azimuth of the stream less
azimuth of the sun must be less than a 90° angle.
Should the difference exceed 90°, subtract this ab-
solute value from 180° to obtain the correct acute
angle. The sine is then  taken of this computed
acute angle.
  Shadow length (S)  is  computed using the for-
mula:
         S =
      height vegetation
      tangent solar angle
                                        (VH.5)
  For example, at 12:30 p.m., S would be equal to:
                                                           S =
                                                                     70 ft
                            = 25.5 ft
              tangent (70°)
  Note, the only periods of the day that should be
considered are those times when existing vegeta-
tion that will be eliminated by the silvicultural
operation effectively shades the stream; i.e., when
the shadow length extends onto some portion of the
stream.
  In the illustration used previously, the existing
trees scheduled to be cut do provide shade to the
stream. The only time of the day when the existing
trees do not shade the  stream occurs about 2:10
p.m. when the stream's effective width is infinity
                                             vn.n

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                          Table VII.2.—Computation of stream's effective width (EW) and
                            vegetative shadow length (S) based upon stream azimuth,
                                      solar azimuth, and solar angle

Daylight savings
time

12:30
1:00
1:30
2:10
2:30
2:45
3:10


Solar
angle

70
72
70
68
65
60
55
azimuth
(°)
155
180
205
225
235
240
245
Effective width
(EW = 1.5/sine
225-Solar azimuth)
(ft)
1.6
2.1
4.4
(infinity)
8.6
5.8
4.4
Shadow length
(S=70/tangent
Solar angle)
(ft)
25.4
22.7
25.5
28.2
32.6
40.4
49.0
(sun is oriented with the stream) and the shadow
length is only  28.2 feet  (table VII.2). Therefore,
removal of this  vegetation would result in exposure
of the water surface to increased solar radiation.
  The proposed silvicultural operation would have
the maximum impact on water temperature at 1:00
p.m.  (solar noon) when the solar angle and radia-
tion  are greatest  and when  existing  vegetation
presently providing shade is removed. Therefore,
the maximum solar angle would be 72°.
not  possible due  to  the angle of the sun and
relatively gentle topographic relief.
             PERCENT SLOPE OF
          ADJACENT TOPOGRAPHY
  The percent  slope of the adjacent topography
must be measured or estimated.
                  EVALUATE
                TOPOGRAPHIC
                  SHADING
  Topographic  shading should be  evaluated to
determine if the water course would be shaded by
topographic features.  For topographic shading to
be present, the percent slope of the ground must
exceed the percent slope of the solar angle  (i.e.,
tangent solar angle).
  If the slope of the  topography adjacent to the
stream is 30 percent and table VH.2 gives the solar
angle as 72° or 308 percent, topographic shading is
            INCIDENT HEAT LOAD
           (NET SOLAR RADIATION)
  Given a specific site, the rate of incoming radia-
tion is constantly changing. To determine the ap-
proximate heat load for the model, the length of
time a given volume of water will be exposed to
direct  solar radiation  also must be determined.
Travel time of the stream can be found by measur-
ing any of the following: average stream velocity
using  a  current   meter  (ft/sec);   empirical
relationships using channel slope data; and/or dye
tracing. The net solar radiation must be averaged
for the time that the water will be exposed. This is
accomplished  by identifying  or interpolating the
appropriate midday solar angle curve and locating
on the time axis the  period of day that the stream
will be exposed (fig.  VTJ.7).
  The radiation value occurring at the midpoint of
the proposed period  can normally be used as the
average net radiation  value.  However, when the
travel time is several hours and the exposed period
goes from midmorning to early afternoon  (for ex-
ample, 9 a.m. to 1 p.m.), it may be necessary to
consider the change in slope of the curve  and to
select a net radiation value more representative for
the period  rather than the midpoint. However, it
should be  noted that this  model is for stream
reaches less than 2,000 feet in length; travel time
will normally not exceed 2 hours and generally will
be less than 1 hour, thereby eliminating the need to
determine an average net radiation value.
                                              VII.12

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  Estimate the incident heat load for the site (fig.
VII.7). Continuing with the previous  example:

  1. Use  the maximum solar angle determined
     previously (72°).

  2. In figure VII.8, interpolate  between the 70°
     and 80° curve  to obtain the 72° values.

  3. Determine the critical time period (1:00 p.m.
     in this example).
                  Find  the  average  H  value.  Travel  time
                  through the exposed section of stream channel
                  is only 0.3 hour; therefore, it is not necessary
                  to find an average H value. From figure VII.8,
                  with a 72° midday angle, the H value for 1:00
                  p.m. is approximately 4.7 BTU/ft2-min; if we
                  had used  the  solar ephemeris for  45°  N
                  latitude, the H value would have  been 4.5
                  BTU/ft2-min.  Figure  VII.8  illustrates  the
                  procedure used to obtain H in this example.
                                       c
                                       I
                                       m
5 —
 Figure VII.7.—Hourly values (BTU/ft2-
  min)  for net solar radiation above
  water surfaces on  clear  days
  between latitudes 30°  N and 50° N
  for several solar paths (Brown 1970).
                                       5
                                       Q 4
                                       CC
                                       §
o 	
                          Solar Angle
                        (At Solar Noon)
                                                                  12   1    2   3
                                                                   TIME of DAY

                                                                (Daylight Savings Time)
                                      1
                          Solar Angle
                         (At Solar Noon)
                                      55-
                                      m
                                      -4.7
                                       Q
                                       <
                                       DC
                                       8
                                       UJ
                                         3 —
Figure VII.8.—Determination  of  net
  hourly  solar  radiation using noon
  angle of 72°. H Is 4.7 BTU/ft2-mln.
                                         2 —
                                                8    9   10   11
                         12   1    2   3
                          TIME of DAY
                      (Daylight Savings Time)
                                               vn.i3

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            PERCENT STREAMBED
               COMPRISED OF
                   BEDROCK
  The  percentage  of  streambed  comprised of
 bedrock must be measured or estimated.
            ADJUSTED NET SOLAR
                RADIATION FOR
           BEDROCK STREAMBEDS
   Bedrock in the streambed acts as a heat sink,
 and conductive loss of energy from the water to the
 rock may occur.  Brown (1972)  recorded a 20-
 percent reduction  of the incident  heat  load  in a
 streambed entirely composed of bedrock.  Assum-
 ing  a linear  relationship for lesser exposure of
 bedrock, use figure VII.9  to adjust H when bedrock
 is exposed in the streambed.


   H adjusted = [% WH] + [%B (1.00-C) H]  (VII.6)
 100

  90-

  80-

  70-
O
2 60-
O
HI
10 50-
UJ40-
DC
111
Q- 30-
  20-

  10-
              0.05        0.10        0.15
                 CORRECTION FACTOR
0.20
        where:
          W  = percent streambed  without bedrock1
                (e.g., 0.10),
          H   = unadjusted heat load (e.g.,  4.7 BTU/ft2-
                min with  a solar ephemeris for 40° N
                latitude),
          B   = percent streambed with rock1 (e.g., 0.90),
                and
          C   = correction factor1 (e.g., 0.18).

          C is obtained from figure VTI.9. In the example,
        bedrock comprises 90 percent of the streambed;
        therefore H should be reduced by 18  percent.

        Hadjusted = 0.10(4.7) + 0.90 (1.00 - 0.18) 4.7 = 3.94

               Determination Of Discharge, Q
                     C
                 DISCHARGE
 Figure VII.9.—Correction factor for the heat-sink effect of
  bedrock streambeds.
         Discharge, that takes place during the critical
       summer period following silvicultural  activities,
       when maximum  water temperature may be an-
       ticipated, represents the flowing portion  of the
       stream. This value should reflect any changes  in
       discharge  quantity  and  timing  due  to the
       silvicultural operation. "Chapter III: Hydrology"
       presents a discussion of a   procedure  and
       methodology for deriving these values.  Discharge
       should  be measured during the  critical summer
       period prior to the proposed silvicultural activity.
       Any  adjustments  in  discharge  due  to the
       silvicultural activity can then be made  on this
       previously measured value.
                                                      Determination Of Exposed Surface Area
                                                                Of Flowing Water, A
  The exposed surface area of a stream is that por-
tion  of  the  flowing water affected  by  the
silvicultural operation. Large pools with little or no
flow do not significantly influence temperature in-
crease of the flowing water. Brown (1972) found no
temperature gradient in small pools in the direc-
tion of flow  and only a small (0.2° C) gradient in
large pools.  The  lack of complete mixing  in the

  1AU percent  values used in equation  VII.6 should be in
decimal form.
                                              vn.i4

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pools limits the transfer of heat (i.e., absorbed solar
radiation) from  the stagnant water in the pool to
the flowing water. If the total surface area of pools
is  considered in determining stream surface area
exposed,  the predicted potential temperature in-
crease will be inaccurate; and if more than one pool
is present in the reach, the magnitude of error is in-
creased even more. Dye can be used, if necessary,
to determine the surface area of a pool that should
be used in predicting temperature change.
  Furthermore,  the surface area of flowing water
exposed by removal of vegetation must be adjusted
to account for the surface exposure prior to the
removal of the vegetation. Riparian vegetation and
timber do not normally  shade a  stream so  com-
pletely as to preclude the transmission of all solar
radiation to the  water surface. For example,  a
western coniferous stand with 400 square feet of
basal area/acre  may allow 5 to 15 percent of the
solar radiation to penetrate (Reifsnyder and Lull
1965).
  The following steps are  involved in computing
the exposed surface area, A.
       LENGTH OF STREAM EXPOSED
     AVERAGE WIDTH FLOWING WATER
       IN EXPOSED STREAM SECTION
  The length of stream that will be exposed by the
silvicultural activity is measured or estimated. The
average width of flowing water in this exposed sec-
tion of stream is measured or estimated during the
time of year when stream temperature is critical.
Accuracy of these measurements or estimates  is
critical as the accuracy of the analysis is dependent
upon this information (see app. VILA, "Validation
of Brown's Model").
    Atotal  = LW
          = 530 ft X 1.5 ft
          = 795 ft2
                           (VH.Va)
    PERCENT FLOWING WATER SURFACE
             SHADED BY  BRUSH
  The percent shade provided by riparian brush
and  shrubs is  estimated by  field observation.
Again, this estimate should be made  during the
time of year when stream temperature is critical.
For the example discussed here, it was estimated
that 15 percent of the  flowing water surface was
shaded.
         FLOWING WATER SURFACE
          AREA SHADED BY BRUSH
  The combination of shade provided by brush and
tree canopy will generally prevent most of the net
solar  radiation from reaching the water surface.
The  surface  area  shaded by brush  is therefore
determined.
  In this example, with 15 percent of the flowing
water shaded during the critical period,  surface
area shaded by brush would be estimated at 120
square feet.
  ^ shade brush
  LW (% stream
  shaded by brush only)
= 530 ft X 1.5 ft X  15%
= 120 ft2
                                      (Vll.Vb)
           TOTAL SURFACE AREA
            OF FLOWING WATER
           TRANSMISSION SOLAR
            RADIATION THROUGH
           EXISTING VEGETATION
  The length of stream exposed, multiplied by the
average width of flowing water, gives surface area.
  For example, a stream with a length of 530 feet
and an average width of flowing water of  1.5 feet
has a total surface area of flowing water of 795
square feet.
  The solar radiation passing through the existing
crown canopy must  be measured  or estimated.
Refer to appendix VII.B for a discussion of how this
might be measured and appendix VII .D for tabular
displays of the relationship between stand density
and transmission of solar radiation.
                                             VII.15

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           SURFACE AREA FLOWING
             WATER EXPOSED TO
              SOLAR RADIATION
   Using  surface  area  exposed  under  current
 vegetative canopy cover, correct for transmission of
 light thr-ough the existing stand that has a percent
 crown closure. Whenever possible, use only angular
 canopy density values (see "Angular Canopy Den-
 sity" in app. VII.C). If only vertical crown closure
 values are available, estimate percent transmission
 of solar radiation.  Values for these estimates  may
 be obtained from  Technical Bulletin  1334, pages
 72-76  (Reifsnyder  and Lull 1965).  Assuming a
 crown closure of 65 percent, figure VII. 10 shows
 that approximately 8 percent of the solar radiation
 will be transmitted through the canopy and reach
 the stream.


 "presently exposed ~~ '"total  ^shadebrush/
                (% transmission through existing
                vegetation)             (VII. 7c)
              = (795 ft2 - 120 ft2) X  8%
              = 54 ft2
   The flowing water, therefore, has approximately
 54 square feet exposed to solar radiation.
   Assuming that all vegetation is removed, the ex-
 posed surface area of flowing water would be 741
 square feet in the example. If some of the current
 vegetative cover were to remain, the surface area
 shaded by the remaining  vegetative cover would
 also be subtracted from Atota] .
     Determination of Maximum Potential
       Daily Temperature Increase, AT


  Determine  the maximum  potential  daily
temperature increase in degrees Fahrenheit using
H, Q, and A values as derived through the previous
steps. Compute the maximum potential change in
daily temperature assuming all riparian vegetation
is removed using Brown's model:
             AT = 	0.000267
                    Q
                                  (vn.3)
where:
  AT  =

   A  =
   Q  =


   H  =
   maximum potential  daily  temperature
   increase in degrees Fahrenheit
   adjusted surface  area
   mean discharge that will occur within the
   exposed reach  during critical period fol-
   lowing silvicultural operation
   adjusted heat load BTU/ft2-min
            TOTAL SURFACE AREA
         FLOWING WATER EXPOSED
 BY REMOVAL OF ALL SHADING VEGETATION
  The surface area required is the additional sur-
face area of flowing water that would be exposed
due to the silvicultural activity. The total surface
area of flowing water cannot be used because part
of the stream (in the example, 54 ft2)  is exposed un-
der the existing pre-silvicultural activity vegetative
conditions.
                                                   Equation VH3 becomes:
AT =
                     adjusted
                   Q
                             0.000267   (VII.3a)
(The use of subscripts indicates that the variables
in Brown's original model,  equation  VII.3,  have
been refined in this handbook.)
In the example:

     Aadjusted  = 741 ft2
     Hadjusted  = 3.94 BTU/ft2-min
           Q  =  0.4 cfs
"adjusted  "total
         ~ "exposed pre-silvicultural activity      (VH.7d)

       =  795 ft2 - 54 ft2
       =  741 ft2
so that:

   AT  =  741 ft2 X 3.94 BTU/ft2 - min
                     0.4 cfs

         0.000267  = 1.9° F
                                              VII. 16

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      100
       90
       80
          0     10
                     CROWN CLOSURE, percent
                    20      30      40      50
60
70
    
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         Evaluation Of Downstream
            Temperature Increases


  To  evaluate downstream impacts  of  increased
water temperatures  caused by silvicultural ac-
tivity, a mixing formula is used (fig. VH.11):
           Tn =
                                        (VII.8)
where:
  T
   I)

  DM
  TM
  D-
      =  temperature  downstream  after  the
         treated stream enters the main stream,
      =  discharge main stream,
      =  temperature  main  stream  above  the
         treated tributary,
      =  discharge stream draining treated area,
  T-r =  temperature stream below treated area
         equals temperature above plus computed
         temperature   increase  (i.e.,  Brown's
         model) or (TA  +  AT) = TT ,
  TA =  temperature stream above treated
         area (measured in  field),  and
  AT =  temperature  increase  computed
         using Brown's model.
The mixing ratio formula merely weights the resul-
tant  temperature (TD)  by discharge. (It should be
noted that small streams with large temperature
increases will be diluted if the stream flows into a
larger water course.)
                              Site Proposed
                          Silvicultural Operation
      T
        D
Figure VII.11.—Components  of  the mixing  formula for
  evaluating  the downstream  impact of increased water
  temperature caused by silvicultural activities upstream.
  Please note,  there  are two factors to consider
when   estimating  the  total  downstream
temperature increase due to upstream silvicultural
activities.  First,  the  total  increase  in water
temperature caused by the operation itself must be
determined  (i.e.,  Brown's model).  Second,  the
reduction of water temperature due to groundwater
inflow must be  determined. These factors must be
estimated, and  these  estimates are generally sub-
ject to considerable error.

Total Increase In Water Temperature

  Water temperature  increases due to silvicultural
activities have  already  been  discussed.  These in-
creases will not  normally be reduced by subsequent
passage through undisturbed stands if the distance
is short. The air temperature  over a stream during
the critical summer period  is  usually warmer than
the water, even in undisturbed areas; furthermore,
the net radiation input will  continue to be positive.
Therefore, it  will generally be impossible for the
water temperature  to be reduced by convective,
evaporative, or radiative energy loss to  the at-
mosphere.
  It follows that up to  some limit, known as the
equilibrium  temperature, successive silvicultural
activities on one stream will  have a compounding
effect  on  water   temperature  increases:  water
temperature  increases  due  to  downstream  ac-
tivities will be added onto increases caused by up-
stream operations. This compounding effect may
be eliminated or minimized, however, if the travel
time between activities is  of such duration as to
preclude arrival of water from  an upstream activity
to  a lower activity before evening when cooler air
temperatures and  back radiation can  lower  the
water temperatures, or  when  there are  inflows of
cooler  groundwater  of  sufficient  magnitude to
dilute warmer surface water.


Reduction In Water  Temperature Due To
Groundwater Inflow

  Groundwater is  cooler  than  summer  surface
water,  and it  can reduce  water temperature in-
creases  caused  by silvicultural operations.  Since
groundwater  temperature  is  fairly  constant for
wide areas, well and/or  spring water temperatures
can be  used  as  a  measure  of groundwater
temperature.  A rough rule  to be applied, if neces-
sary, is that the groundwater temperature is ap-
proximately equal to  the  average  annual  air
temperature.
                                              VII. 18

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  Groundwater discharge can be measured in the
field. Increasing discharge downstream can be as-
sumed to be groundwater inflow only if there are no
inflowing tributary streams and if there has been
no recent precipitation event which might still be
entering the stream as quick flow rather than base
flow.
  In trying to estimate groundwater discharges on
small streams, the error of measurement is likely to
be high and the potential for groundwater cooling
the stream is  quite large. This combination  can
lead to significant error in predicting temperature
change below an exposed reach.
  Once groundwater temperature and inflow have
been measured, or estimated, the mixing ratio  for-
mula can be used to evaluate its impact on reduc-
ing temperature increases caused by  silvicultural
operations upstream.  Groundwater that  becomes
surface flow is subject to radiation and convection
heat influxes resulting in temperature increases.
  The formula is the same mixing ratio as the  one
previously presented in equations V.2. and V.8.
          Tn =
                DGTG+DTTT
                                       (VH.9)
Figure  VII.12.—Components of the  mixing formula for
 evaluating the impact of ground water temperature and in-
 flow on reducing temperature increases due to silvicultural
 activities upstream.
These variables are represented on figure YE. 12
where:
  TD  =  temperature  downstream  at some point
         of interest, degrees Fahrenheit,
  DG  =  discharge of  the groundwater,  cfs;  it is
         equal to the discharge at the point of in-
         terest  less the discharge immediately
         below the silvicultural operation,
  TG  =  temperature  groundwater,  degrees
         Fahrenheit,
  DT  =  discharge  immediately  below  the
         silvicultural operation, cfs, and
  TT  =  stream  temperature  below  the
         silvicultural operation which is equal to
         the  temperature above plus computed
         temperature increase or TA + AT = TT  ,
         and where:
  TA  =  temperature  stream above the  treated
         area (measured in field), and
  AT  =  temperature  increase  computed using
         Brown's model.
                                                         Temperature Above
                                                                 Cut

                                                             Site Proposed
                                                           Silvicultural
                                                         Operation
                                                                (Cut)
                                                                           DT  TT  Discharge
                                                                          and Temperature
                                                                          Below Cut
                                                                       TA +  increase
                    Discharge and
                    Temperature Groundwater
                    At Some Point of Interest
                                             VH.19

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               APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
1.  Application of the model should be limited to
   stream sections of less than 2,000 feet in length.
   Beyond this distance, evaporative and convec-
   tive energy losses, assumed to be negligible in
   the simplified model, become important sources
   of dissipation.
2.  Accurate measurement of data is critical.
   a.  It is essential to measure the  average width
      of flowing water when stream temperature is
      critical (i.e., during the summer months).
      Streambed or water surface width should not
      be used for computing average width of flow-
      ing water if any exposed rocks, gravel bars,
      or pools are present in the cross section; to do
      so  would  result in  computed  maximum
      temperatures in excess of  actual  values.
   b.  Discharge  should be  measured  whenever
      possible and should represent the mean dis-
      charge through the exposed reach of stream.
      If there will be no increase in discharge dur-
      ing the critical summer period following the
      silvicultural activity,  the  discharge
      measured before  the activity may be  used.
      However,  if the  silvicultural activity will
      result in increased  discharges during the
      summer,  all  calculations must  be  based
      upon  the post-silvicultural  activity  dis-
      charge. ("Chapter HI:  Hydrology"  can be
      used to estimate the discharge  during the
      critical summer period.)
    c. Shading, both vegetative  and topographic,
      must be determined as accurately as possi-
      ble.  Angular canopy density measurements
      should  be  taken  to  estimate  vegetative
      shading. All shading is important.  Under-
      story noncommercial trees, brush, and low
      shrubs may be more significant for shading
      purposes than commercial timber. Assuming
      the stream is completely shaded at all times
      is probably erroneous and will result in es-
      timated temperature increases far above ac-
      tual  increases.
    d. The  proportion  of the exposed  streambed
      composed of bedrock must be estimated in
      order to account accurately for the heat sink.

3. Small streams with  braided flows require more
   accurate field measurements  of  stream width
   than larger, single channel streams.

4. The capacity of a stream for absorbing  heat is
   limited.  As stream temperature approaches air
   temperature, equilibrium will be reached.

5.  The model does not  consider inflowing  cool
   ground  water.  Such  a  consideration  could
   significantly reduce the maximum temperature
   increase  predicted by  the  model. If inflowing
   ground water could  alter the  temperature in-
   crease, its impact can  be evaluated by using a
   mixing formula (eq. VII.9).
                                            VE.20

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                                  LITERATURE CITED
Brazier, Jon R., and George W. Brown. 1973. Buffer
  strips for stream temperature control. Res. Pap.
  15. For. Res. Lab. Sch. For., Oreg. State Univ.,
  Corvallis. 9 p.

Brown, George W. 1969. Predicting temperatures of
  small streams.  Water Resour. Res. 5(l):68-75.

Brown, George W. 1970.  Predicting the effect of
  clearcutting on stream temperature. J. Soil and
  Water Conserv. 25:11-13.

Brown, George W.  1971. Water temperature in
  small streams  as  influenced by environmental
  factors  and logging. Proc. Symp. For. Land Uses
  and Stream  Environ. [Oreg. State Univ., Oct.
  19-21, 1970] p.  175-181.

Brown, George W. 1972. An improved temperature
  prediction  model  for  small  streams.  Water
  Resour. Res. Inst.  WRRI-16. Oreg. State Univ.,
  Corvallis. 20 p.

Brown, George W., and James T. Krygier. 1970. Ef-
  fects of clear-cutting  on stream temperature.
  Water Resour. Res. 6(4):1133-1139.

Brown, George  W.,  G. W. Swank  and  Jack
  Rothacher. 1971.  Water temperature  in the
  Steamboat drainage. USDA For. Serv. Res. Pap.
  PNW-119. Pac. Northwest For. and Range Exp.
  Stn., Portland, Oreg.

Eschner,  Arthur R., and  Jack Larmoyeux.  1963.
  Logging and trout: Four  experimental forest
  practices and their effect on water quality. Prog. -
  Fish  Cult. April 1963. p. 59-67.
Hughes, Dallas R. 1976. Personal communication.
  Reg.  Hydrologist,  USDA,  For. Serv., Pac.
  Northwest Reg., Portland, Oreg.

Lanty, Richard L. 1971.  Guidelines  for stream
  protection in logging operations. Res. Div. Rep.
  Oreg. State  Game Comm. Portland, Oreg.

Lee,  Richard.  [In  preparation.]  Forest
  Microclimatology. Columbia Univ. Press.

Meehan, W. R., W. A. Farr, D. M. Bishop, and J.
  H. Patric. 1969.  Some effects of clearcutting on
  salmon habitat of two southeast Alaska streams.
  USDA For.  Serv.  Res.  Pap. PNW-82. Pac.
  Northwest For. and Range Exp. Stn., Portland,
  Oreg.

Reifsnyder and Lull. 1965. Radiant energy in rela-
  tion  to forests.  USDA For.  Serv. Tech. Bull.
  1334. Ill p.

Smithsonian   Institute.   1968.   Smithsonian
  meteorological tables. 6th  ed. Smithson. Misc.
  Collect. Vol. 114. Smithson.  Inst. Press, Wash.
  D.C. 527  p.

Stone, Earl. 1973. The impact of timber harvesting
  on soils and water. President's Advis. Panel on
  Timber and  Environ. Rep. Senate Hearings, p.
  427-467.

Swift,  Lloyd W.,  and James  B. Messer. 1971.
  Forest  cuttings  raise temperatures  of small
  streams in the  southern Appalachians. J. Soil
  and Water Conserv. (May-June 1971.)

U.S. Department of Agriculture, Forest Service.
  [n.d.1 Water temperature  control. Pac. North-
  west Reg., Portland, Oreg.  GPO 797-425. p. 27.
                                             VH.21

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                                     APPENDIX VILA:

                             VALIDATION OF BROWN'S MODEL
  Brown developed and verified his model  in the
West, and utilization by western forest hydrologists
has had good results.
  To  determine its national applicability, a very
limited  validation of the model was conducted in
the East using two treated, clear-cut watersheds
(Watersheds 3 and 7) and a control (Watershed 4)
on the Fernow Experimental Watershed, Parsons,
West  Virginia.
  The field data collected from Watersheds 3 and 7
consisted  of the length and width of the exposed
stream  reach following treatment, discharge,  and
percent bedrock in streambed. In addition, the ac-
tual water temperature was recorded so that the es-
timated water temperature increase, computed us-
ing Brown's model, could be compared with the ac-
tual increase. Water  temperature of the control
watershed was also measured and was used to ap-
proximate the water  temperature of the treated
watersheds before treatment.
   Using Brown's model, initial estimations of the
water temperature increases following treatment
were  +6° F to  +10°  F  higher than  the  actual
measured  values.  It  was determined that the
average stream width, not the average  width of
flowing water, was measured.  When the average
width of flowing water  was measured  Brown's
model estimated within +1° F to +3° F of the ac-
tual water temperature increase, table VE.A.l. No
data  were available to estimate  the  amount of
streamside vegetative  shading and, therefore, the
estimated values would tend to be high.
 Table VILA.1.—Summation of validation test using data (°F)
                      from
  Fernow Experimental Watershed, Parsons, West Virginia


Watershed/
treatment


3/clearcut
7/clearcut
4/control
Estimated
temperature
using
procedure
presented
°F
64
63
—


Measured
temperature

°F
63
60
58


Difference



+ 1
+3
—
  This validation not only indicates that Brown's
model is applicable for use  in the East, but also
reaffirms  the  importance of obtaining  accurate
field measurements. The model is only as accurate
as the data that are used.
  Actual  computations for  the two  treated
watersheds follow:
            Watershed 3, Clearcut
  L    = 2,336 ft
  W   = 1.35  ft (average width flowing water)
    [Initial width used was 3.30 ft but this was the
    average width of the stream.]
  A    = LW  = 2,336 ft X 1.35 ft = 3,154 ft2
  Latitude =  39°
    Maximum  water  temperature  occurs on
    August 28
  Maximum Solar Angle = 60° on August 28
  Bedrock  = 20%       Correction Factor =  0.95
  H        =  4BTU/ft2-min
  H adjusted  =  H X Bedrock Correction Factor
           =  4 BTU/ft2 X 0.95
           =  3.8 BTU/ft2-min
  Q        =  0.53 ft3/s

  AT  _ A Hadjusted  0.000267
           Q

       = 3,154ft2 (3.8 BTU/ft2 - min) 0.000267
                  0.53  ft3/s

       = 6° F

  Water temperature  = 58° F  for  Control
                        Watershed 4 (not cut)
  Control temperature  + AT  =  Estimated water
                                temperature of
                                clearcut
  58°  F +  6° F  =  64° F
  Estimated temperature = 64° F1
  Measured temperature = 63° F  for Watershed 3
                                                     'No information on shading brush; therefore estimated in-
                                                   crease may be high.
                                              VII.22

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          Watershed 7, Clearcut
L   = 2,380ft
W  = 1.80 ft (average width flowing water)
  [Initial width used was 2.60 ft, but this was the
  average width of the stream.]
A       = LW = 2,380  ft = 2,380 ft (1.80 ft)
        = 4,284 ft2
Latitude = 39°
  Maximum  water  temperature  occurs  on
  August 28.
Maximum Solar Angle =  60° on August 28
Bedrock = 25%       Correction Factor = 0.95
H       = 4BTU/ft2-min
H adjusted = H(Bedrock Correction Factor)
        = 4  (0.95) =  3.8  BTU/ft2-min
Q       = 0.83 ftVs
         A Hadjusted   0.000267
            Q

          4,284ft2 (3.8 BTU/ft2 - min)   0_000267
                  0.83 ftVs
      =  5° F

  Water temperature  =  58°  F  for  Control
                        Watershed 4 (not cut)
  Control temperature + AT =  Estimated water
                                temperature of
                                clearcut
  58° F + 5° F = 63° F
  Estimated temperature = 63°  F2
  Measured temperature = 60° F for Watershed 7

  Wo information of shading brush; therefore, estimated in-
crease may be high.
                                           VH.23

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                                     APPENDIX VII.B:

                                    STREAMSIDE  SHADING
  Research conducted throughout the country has
demonstrated  that removal  of commercial  and
noncommercial streamside vegetation will result in
increased water temperatures due to increased ex-
posure of the water surface to direct radiation. Us-
ing  Brown's  model,  the magnitude  of  the
temperature increase varies with the proportion of
stream exposed.
  Maximum increases are  associated with clear-
cutting in  the  streamside  area.  The  increases
reported range  from a few degrees to  28° F,
depending  upon  the  area  and  discharge of the
streams affected  (Eschner  and Larmoyeux 1963,
Meehan and others 1969, Brown and Krygier 1970,
Brown 1971, and Swift  and Messer 1971). Water
temperature can be maintained, however, if there
is  adequate shading of the water surface during
periods of maximum solar radiation. Shading may
be topographic, vegetative, or  a combination of
both.
         TOPOGRAPHIC SHADING


  Shading  by topographic features  includes not
only the major  land forms, but also the minor
changes in relief associated with streambanks. The
potential for topographic shading is determined
partly by orientation of the stream with the  sun,
and partly  by latitudinal location.
  Orientation of topographic features in relation to
stream and sun  is crucial. Streams oriented east-
west may be shaded in the morning by topographic
features to the south. North-south oriented streams
may be shaded in the morning by  topographic
features situated to the east, and to the west in the
afternoon.
  Latitudinal position of the stream influences the
extent to which topography or surrounding vegeta-
tion may be effective because latitude determines
solar angle. The path of the sun varies during the
year from 23- Ą1° N latitude (June 21) to 23-V^0 S
latitude (December 22). When the solar angle is
vertical, directly overhead, there is no possibility
for  topographic  shading;  as the angle  decreases
from the vertical, the probability and effectiveness
of topographic shading are increased.
          VEGETATIVE SHADING


  Vegetative shading normally will be the domi-
nant onsite factor controlling the amount of solar
radiation  directly  striking  the  water   surface.
Shading is not limited to dominant and codomi-
nant tree  species, but encompasses all vegetation
to include brush, shrubs, and other  low-growing
species.
1. The effectiveness of the shade created  will vary
   with vegetation type. The effect of type includes
   not  only species differences but also age class.
   The proportion of tree bole in a live crown in-
   fluences the extent of shade provided. Mature
   coniferous stands, with much of the lower bole
   free of limbs, may offer only partial shade;
   whereas younger stands, with most of the bole in
   live crown,  will  provide adequate shade  for
   small headwater streams.
2. The density or spacing of vegetation also deter-
   mines  the amount  of  radiation  the water
   receives. In poorly stocked stands with low den-
   sity and  crown closure,  the  trees may be  so
   widely spaced as to preclude effective shading of
   the  water course.
3. For a stream  of a given width, the height of
   vegetation necessary to effectively shade a water
   course  will vary  with  the distance from  the
   stream and the solar  angle and  orientation.
   There is a direct relationship between distance
   from the stream and height of vegetation neces-
   sary to provide adequate shade (fig. VII.B.I).
4. For a stream of a given  width, there  is also a
   relationship between solar angle and height of
   vegetation needed to provide stream  shading.
   When the solar angle is perpendicular to  the
   stream surface (i.e., directly overhead), the only
   shading is that from vegetation overhanging the
   water; the height of riparian vegetation becomes
   irrelevant (fig. VH.B.2).
5. Orientation of the sun with respect to the stream
   determines the "effective" width of the stream
   versus the actual stream width. Effective width
   is the length of shadow required to reach com-
   pletely across the stream. The actual width
   would equal the effective width only when the
   sun was oriented  at right angles to the stream
                                              VH.24

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    Figure VII.B.1.—Low growing shrubs and brush adjacent to a water course may provide adequate shade,
                        while taller vegetation is necessary further from the stream.
Figure VII.B.2.—Position of the sun in relation to the
  riparian vegetation determines the time and extent of
  vegetative shading.
                                               VH.25

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(e.g., due east of a north-south flowing stream,
fig. VII.B.3). At  all other times the effective
width would be greater than the actual stream
width and would reach a maximum value (in-
finity) when  the sun  was  directly  above the
stream.
   Figure VII.B.3.—Orientation of the sun with the stream determines the length of shadows necessary to com-
     pletely shade the water surface.
                                             VII.26

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                                     APPENDIX VII.C:

                                     WATERSIDE AREAS
  Designation of waterside areas by land managers
can  be used  to  prevent  or  minimize water
temperature increases. It is not feasible to establish
general  standards  for waterside areas;  however,
Brazier and Brown (1973) have evaluated some of
the factors that determine the effectiveness of such
areas.


     COMMERCIAL TIMBER VOLUME
  Commercial timber volume is not a significant
parameter for determining shading of the stream
by the vegetation in the waterside area. Due to the
relatively narrow width of the headwater (1st, 2nd,
and 3rd order) streams, the effectiveness of the
shade produced by noncommercial tree  species,
shrubs and low growing vegetation can be as great
as that produced by commercial species. In addi-
tion, there is a great  variability between volume
(board feet)  and crown closure (density) which is
manifested in the spacing and number of trees per
unit of area.  A few large trees with a large commer-
cial volume  may have little protective capability
                                               because of wide spacing, or because crowns may be
                                               too high or sparse to shade the streams. Many pole-
                                               sized trees with a smaller commercial volume may
                                               effectively shade the stream due to their close spac-
                                               ing and dense canopy.
                                                               STRIP WIDTH


                                                 In  the past,  land managers have arbitrarily
                                               designated waterside areas according to such fac-
                                               tors as width (which has ranged from less than 50
                                               feet to several hundred feet),  topography, or per-
                                               cent slope. Strip width alone  is not an important
                                               factor in determining effectiveness of the vegeta-
                                               tion in shading the stream. Strip width is critical
                                               for stream protection only as it is related to canopy
                                               density,  canopy  height and  stream width  (fig.
                                               VII.C.l).
                                                 Canopy densities of less than about 15 percent
                                               angular canopy density (ACD) do not provide suf-
                                               ficient shade for  a measurable reduction  in heat
                                               load. Above this value, however, there should be a
   100^
 I
s.
80—
~    -i
in
I  60-
 o
O 40-
 3
 O)
 < 20-
    T
                      I
                     40
I
                         T
                         60
I
20      40      60     80
    Waterside Area (feet)
 I
100
                                                Figure VII.C.L—The relation between waterside area width
                                                  and angular canopy density (Brazier and Brown 1973)
                                             VII. 27

-------
direct  relationship  between  heat reduction and
angular  canopy  density  until  the canopy ap-
proaches 100  percent ACD.  As  the density ap-
proaches 100  percent,  additional increments  in
density  should  block  less  radiation  than the
previous increment. Therefore, with greater canopy
density,  the relationship between the  amount  of
heat blocked  and  the  angular  canopy  density
should approach some maximum value at a level
less than complete blockage of all incidental radia-
tion (fig. Vn.C.2).
  When the angular canopy density is not known or
cannot  be measured,  stream shading may be es-
timated using  a clinometer or abney level to iden-
tify those crowns which contribute shade  to the
stream. Vertical crown closure values can be used
to obtain a rough estimate of stream shading, but it
should be noted that angular canopy density and
vertical crown closure are normally significantly
different. The importance of obtaining accurate
measurements  of  stream shading  cannot  be
overemphasized; it is the basis for establishing ef-
fective waterside area widths to protect the stream
from excessive temperature increases.
c

i   3
m
o
o
CD

|
         I    I   I    I   I    I   I    I   I   I
         10                              100
              Angular Canopy Density, %
Figure VII.C.2.—The relation between angular canopy density
  (ACD) and heat blocked (AH) (Brazier and Brown 1973).
                                             VH.28

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                                          APPENDIX VII.D:

                 GENERAL RELATIONSHIPS BETWEEN  LIGHT INTENSITY OR
             TRANSMISSION OF SOLAR RADIATION AND VEGETATIVE COVER
  Table VII.D.1.—Effects of stand density removal on light
             Intensity (%) (USDA For. Serv.)
Percent
Quantity Fully stocked
removed stand removed
Stem density



Canopy closure



Basal area



0
25
50
'75
0
25
50
75
0
25
50
75
Light intensity
8
14
26
'55
4
6
16
43
10
15
27
52
Table VII.D.4.—Percent light Intensity through eastern conifers
               (Reifsnyder and Lull 1965)

                             Basal area   Light intensity
         Species              (ftVac)
White pine, balsam fir 209
White pine, white spruce, balsam fir 171
White pine, red pine 103
White, red, jack pine, white spruce,
balsam fir 103
7
9
27

25
                                                             Table VII.D.5.—Percent light intensity through conifer
                                                                    plantations (Reifsnyder and Lull 1965)
                                                                   Spacing
                                  Light in open
  'Example: Removing 75 percent of the stems would increase
the light intensity from 8 percent to 55 percent.
2X2
4X4
6X6
8X8
15.9
36.0
46.6
55.4
     Table VII.D.2.—Effects of tree spacing (ft) on light
            intensities (%) (USDA, For. Serv.)
Spacing
(«)
4X4
6X6
7X7
9X9
Trees
(number/ac)
2,721
'1,210
889
538
Light Intensity
15
'16
36
60
Table VII.D.6.—Stand basal area (ft2/a) and equivalent solar
        loading (BTU/ft2-min) beneath the canopy
         (Hughes 1976, personal communication)
  'Example: By removing slightly less than half the trees (538)
from a 6 X 6 foot spacing (1,210) increases the light intensity from
16 percent to 60 percent.
 Table VII.D.3.—Percent light Intensity through small-1 and
      large-2 crown trees (Reifsnyder and Lull 1965)
Stem density
(in/ac)
200
700
1,200
1,900
3,700
Basal area
(ft/ac)
20
60
100
180
400
Percent of small-crowned trees
0-33 34-67 68-100
Percent light Intensity
87
57
34
13
7
90
70
50
30
10
94
78
63
43
12
Solar load ing
% of open
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
Total stand basal area
Dense crown1 Moderate crown2
255
200
160
135
120
105
90
80
70
60
55
45
35
30
25
20
10
5
0
400
305
245
210
180
160
140
120
105
90
80
70
55
45
35
30
20
10
0
  'Small—western white pine, western larch, and Douglas-fir.
  2Large—grand fir, western hemlock, and western red cedar.
  'Dense crown includes  normally stocked  stands of western
hemlock, western redcedar, Sitka spruce, Pacific silver fir, and un-
even aged mixed stands. Also overstocked hardwood stands.
  2Moderate crown includes even aged Douglas-fir stands, and
normally stocked red alder or black cottonwood.
                                                   VH.29

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100
    0      10
CROWN CLOSURE, percent
20     30      40      50
                                                 60
                            POINTS FROM PUBLISHED STUDIES
                          O IN WHICH CROWN CLOSURE WAS
                            REPORTED OR COULD BE ESTIMATED
                            POINTS FROM STUDIES IN WHICH
                            STEM DENSITY WAS REPORTED OR
                            COULD BE ESTIMATED.
                              CROWN CLOSURE
                              (UPPER SCALE)
        STEM DENSITY
        (LOWER SCALE)
   0      1000   2000    3000   4000   5000    6000  7000
                 STEM DENSITY, inches per acre
 Figure VII.D.1. Transmission of solar radiation as a function of stem density and crown
                   closure (Reifsnyder and Lull 1965).
                            VH.30

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          Chapter VIII

PROCEDURAL EXAMPLES
   this chapter has been prepared by the coordinators
           for chapters III-VII
              vrn.i

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                              CONTENTS
                                                                     Page

INTRODUCTION	  Vffi.1
PROCEDURAL EXAMPLE FOR GRITS CREEK—A RAIN DOMINATED
 HYDROLOGIC REGION  	  VIE.2
  DESCRIPTION OF AREA AND PROPOSED SILVICULTURAL ACTIVITY  VIII.2
    Water Quality Objectives	  VIII.2
  DATA BASE 	  VIII.5

  HYDROLOGY ANALYSIS	  VDI.5
    Water Available For Streamflow—Existing Conditions	  VIE.5
    Water Available For Streamflow—After Proposed
      Silvicultural Activity  	  VIE.13
    Flow Duration Curve Development—Existing Conditions 	  VIII.13
    Flow Duration Curve Development—After Proposed
      Silvicultural Activity  	  Vffl.14

  SURFACE EROSION ANALYSIS	  VIE.16
    Erosion Response Unit Delineation  	  VIII. 16
    Using the Modified Soil Loss Equation (MSLE) 	  VIII.22
      Rainfall Factor	  VIII.22
      Soil Erodibility Factor	  VIII.22
      Length-Slope Factor	  VIII.22
      Vegetation-Management Factor	  Vin.24
      Surface Area Of Response Unit	  VIII.25
    Sediment Delivery	  VIII.25
    Differences Between Management Alternatives	  VIE.26

  TOTAL POTENTIAL SEDIMENT ANALYSIS 	  VHI.26
    Suspended Sediment Calculation	  VIE.26
    Bedload Calculation	  VIII.30
    Total Potential Sediment Calculation	  VIII.30
    Channel Impacts	  VIE.31

  TEMPERATURE ANALYSIS	  VEI.31
    Lower Reach	  VIE.31
      Computing H, Adjusted Incident  Heat  Load	  VIE.31
      Computing Q, Stream Discharge  	  VIE.34
      Computing A, Adjusted  Surface Area	  VEI.34
    Middle Reach	  VIE.35
      Computing H, Adjusted Incident  Heat  Load	  VIE.35
      Computing Q, Stream Discharge  	  VIE.35
      Computing A, Adjusted  Surface Area	  VIE.35
    Upper Reach	  VIE.36
      Computing H, Adjusted Incident  Heat  Load	  VIE.36
      Computing Q, Stream Discharge  	  VIE.36
      Computing A, Adjusted  Surface Area	  VIII.36
                                   vm.ii

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                                                                     Page


    The Mixing Ratio Formula	  VIII.37

  ANALYSIS REVIEW	  VIII.38
    Worksheets For Grits Creek, Alternatives A and B	  Vffl.41
PROCEDURAL EXAMPLE FOR HORSE CREEK—A SNOW DOMINATED
 HYDROLOGIC REGION  	  VIII.72
  DESCRIPTION OF AREA AND PROPOSED SILVICULTURAL ACTIVITY.  VIII.72
    Water Quality Objectives	  VHI.72
  DATA BASE 	  Vffl.72

  HYDROLOGY ANALYSIS	  VHI.72
    Water Available For Streamflow—Existing Conditions	  VHI.72
    Water Available For Streamflow—After Proposed
      Silvicultural Activity	  VEI.81
    Streamflow Discharge And Timing—Existing Conditions	  VIII.82
    Streamflow Discharge And Timing—After Proposed
      Silvicultural Activity	  VEI.83

  SURFACE EROSION ANALYSIS	VHI.83
    Erosion Response  Unit Delineation  	VIII.83
    Using The  Modified Soil Loss Equation (MSLE)	Vffl.85
      Rainfall  Factor	VHI.85
      Soil Erodibility Factor	VHI.85
      Length-Slope Factor	VHI.86
      Vegetation-Management Factor	VIII.87
      Surface Area Of Response Unit	Vm.88
    Sediment Delivery	VEI.89

  SOIL MASS MOVEMENT ANALYSIS	VHI.91

  TOTAL POTENTIAL SEDIMENT ANALYSIS 	  VHI.91
    Suspended Sediment Calculation	  VIII.91
    Bedload  Calculation	  VHI.95
    Total Potential Sediment  Calculation	  VHI.95
    Channel  Impacts	  VEI.97

  TEMPERATURE ANALYSIS	VIII.100
    Computing H, Adjusted Incident Heat Load  	VIII.100
    Computing Q, Stream Discharge 	VIII.102
    Computing A, Adjusted Surface Area	VIII.102
    The Mixing Ratio Formula	VIII.102

  ANALYSIS REVIEW	VIII.103
    Interpretation Of The Analysis Outputs	VIII.103
    Comparing Analysis Outputs To Water Quality  Objectives	VIII. 104
    Control Opportunities For Soil Mass Movement	VIII. 104
    Control Opportunities For Surface Erosion  	VIII. 105
    Control Opportunities For Temperature	VIII. 105
    Revised Silvicultural Plan	VIII.108
    Worksheets For Horse Creek, Proposed And Revised Plans	  VIII. 109
LITERATURE  CITED 	  VEI.160
                                  Vffl.iii

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                            LIST OF FIGURES
Number                                                                  Page
Vm.l. —Timber compartments for Grits Creek watershed	  VIE.3
Vm.2. —Road constructed for Alternative B, Grits Creek watershed	  Vffl.4
VIII.3. —Annual flow  duration  curves  for existing  and alternative A or B
           conditions,  Grits Creek watershed  	  VIE.15
VItI.4. —Drainage  net, Grits Creek watershed	  VIII.17
Vin.5. —Hydrographic areas, Grits Creek watershed	  VIE.18
VIII.6. —Soil groups, Grits Creek watershed	  Vffl.19
Vm.7. —Silvicultural treatments, Grits creek watershed 	  VIE.20
VIII.8. —Enlargement  of example hydrographic area showing individual ero-
           sion response units 	  VIE.21
VIE.9. —Stiff diagram for alternative A CC3.1, Grits Creek watershed	  VIE.27
VIII.IO.—Sediment rating curve,  Grits Creek watershed 	  VIE.28
VIII.ll.—Channel stability threshold  limits in relationship  to  the sediment
           rating curve, Grits Creek watershed	  VIE.29
VIII.12.—Water temperature evaluation,  Grits Creek watershed  	  VIE.32
VIII. 13.—Pre- and post-silvicultural activities annual hydrograph, Horse Creek
           watershed	  VIE.84
VEI.14.—Stiff diagram for CC3.1 of proposed plan, Horse Creek watershed ..  VIE.90
VEI.15.—Horse Creek drainage showing potential areas  of mass  movement...  VIE.93
VIII.16.—Sediment rating curve,  Horse Creek watershed	  VIE.94
VEI.17.—Bedload rating curve, Horse  Creek watershed  	  VIII.96
VIII.18.—Bedload   transport-stream power  relationship,   Horse  Creek
           Watershed	  VIE.99
                                     Vin.iv

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                            LIST OF TABLES


Number                                                                 Page

VIII.l.—A summary of information required for the analysis procedures, Grits
          Creek watershed   	  Vni.6
VHI.2.—Summary of quantitative outputs for Alternative  A, Grits Creek
          watershed	  VHI.39
Vin.3.—Summary of quantitative outputs for Alternative  B, Grits Creek
          watershed	  VHI.40
VIII.4.—A summary of information required for the analysis procedures, Horse
          Creek watershed 	  VEI.73
Vin.5.—Summary of quantitative outputs for proposed plan, Horse Creek
          watershed	  VEI.92
Vin.6.—Summary of  quantitative outputs for revised  plan,  Horse Creek
          watershed	  VHI.107
                                     vm.v

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                                      INTRODUCTION
  This chapter provides examples of silvicultural
activities on two hypothetical watersheds—one in a
rain dominated hydrologic region (Grits Creek) and
one in a snow dominated region (Horse Creek). It
demonstrates the procedural analyses that would
be conducted to evaluate the potential non-point
source pollution associated with each  example.
Where such potential non-point source  pollution
would exceed established water quality objectives,
the procedure for considering control opportunities,
thereby revising the original silvicultural plan, is
explained.
  All figures,  tables, and  worksheets  mentioned
within this chapter are referenced  according  to
their original chapter number. Only figures unique
to chapter VIE have been given "VIE" numbers.
                                              VEI.l

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    PROCEDURAL EXAMPLE FOR GRITS CREEK—A RAIN DOMINATED
                                 HYDROLOGIC REGION
       DESCRIPTION OF AREA AND
 PROPOSED SILVICULTURAL ACTIVITY
  Foresters  from  the Appalachian Hardwood
Products Company1 inventoried a 356-acre tract of
hardwoods (fig. VIII. 1) owned by the company in
the southern Appalachians. The watershed is at a
latitude of 35°N.  The baseline  leaf area  index
(LAI) is 6. Dominant aspect is southwest, and the
average rooting depth for the watershed is 4 feet.
The tract was divided into timber compartments
A, B, and C (fig. VIII.1) based upon stand composi-
tion; management prescriptions were proposed  for
each.  A description of each timber compartment
and the prescribed management options follows.
  Compartment A is an 84-acre stand along the
ridgetop of the watershed. It is composed of low
quality  northern  red oak and  a  dense laurel-
rhododendron  understory. Trees  are  short and
branchy because of repeated ice damage, and the
growth potential is low in these steep, rocky, shal-
low soils. Because  of high recreation use and the
poor site condition for timber production, the com-
pany  forester recommended that no silvicultural
activity be conducted.
  Poor oak-hickory stands are present on the lower
slopes in compartment B, producing little timber;
but soils are  deep, well  watered, and capable of
timber production. The proposed residual leaf area
index is estimated to be 2.  The forester recom-
mended  that the  180-acre  timber  stand  be
regenerated by clearcutting all woody  vegetation
after harvesting mechantable timber.
  Compartment C,  92 acres, contains a 40-year-old
stand of excellent yellow poplar mixed with over-
mature remnants of other cove hardwoods. It was
originally estimated that the yellow poplar would
be from 85 to 120 feet high at age 50, but the growth
rate of the overcrowded  stand has slowed during
  lThis is intended to be a fictitious company name; any
similarity to an actual company is entirely coincidental.
the last 7 years. A thinning has been recommended
by the company forester to increase growing space
for  crop trees. Additional cuts will be required at
20-year intervals.  The proposed residual leaf area
index is estimated to be 3. Compartment C would
be reevaluated for a possible clearcut in 40 years, in
accordance with the company's policy of even-aged
management. Then the site would be regenerated
to yellow poplar or other desirable species.
  Based  upon  these  management prescriptions,
engineering and harvesting system analyses were
made. Two alternatives were developed for analysis
using the  basic steps outlined  in  "Chapter II:
Control Opportunities," Appendix n.A, example
two. The significant resource  impacts were  "bare
soil" and "compaction." Based on a knowledge of
the site and professional judgment,  the following
control opportunities were selected.
  1. Prescribe yarding and skidding layout.
  2. Revegetate treated areas promptly, as local
conditions  dictate.
  The two engineering and harvesting alternatives
were based on different yarding systems, road loca-
tions, and revegetation prescription. Alternative A
was based  on tractor  yarding with road locations
shown in figure VIE.2. Alternative B was based on
cable yarding systems and required an  additional
road (fig. Vffl.2) to achieve reasonable yarding dis-
tances. Revegetation of all roads, including run-
ning surfaces, was planned in Alternative B. Both
alternatives were  analyzed and the  results com-
pared to water  quality objectives.

           Water Quality Objectives
  Water quality objectives were established for the
Grits Creek  area by the Regional Planning Com-
mission in conjunction with State 208 planners.
The established objectives required that channel
stability be maintained, that total potential sedi-
ment discharge be limited to 25.5 tons/yr and that
water temperature increases be  no greater than
3° F.
                                             VIH.2

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                        1 mile
Figure VIII.1.—Timber compartments (or Grlto Creek watershed.
                       vm.3

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                                                  Road for Alternative B
                              1 mile
Figure VIII.2.—Road constructed for Alternative B, Grits Creek watershed.
                             vra.4

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                 DATA BASE
  The collected data are presented in table Vffl. 1
and  worksheets  IV.l,  IV.2,  V.I,  and  VII.2.
(Proposed and revised worksheets are located  at
the end of section "Procedural  Example for Grits
Creek—. . .")  Soils  were  mapped  by  the  Soil
Conservation Service. All data presented are re-
quired, unless otherwise  specified, for a complete
water resource evaluation of Grits Creek, the major
drainage in the tract. The complete evaluation re-
quires analyses within  the  following categories
(numbers for  the  corresponding chapters in this
handbook appear in parentheses):
  Hydrology (HI)
  Surface Erosion (IV)
  Total Potential Sediment (VI)
  Temperature (VH)

          HYDROLOGY ANALYSIS
   The hydrology analysis serves as a guide to es-
 timate change  in potential streamflow associated
 with silvicultural activities in rainfall dominated
 regions.  The   methodology  and  procedures
 presented in this document are only guidelines to
 complement professional judgment for a particular
 situation.
      Water Available For Streamflow—
              Existing Conditions

  Step 1. — The first step in the hydrologic evalua-
tion of  Grits  Creek  is to  estimate  the water
available for streamflow under existing conditions
using worksheet ELI. The necessary procedures are
outlined below. (Numbers in parentheses  refer to
items or columns on the worksheet.)
   (1) Watershed name. — Grits Creek  may be
treated  as  a single watershed unit for hydrologic
evaluation  (see "Chapter HI: Hydrology").
   (2)  Hydrologic region.  —  Grits  Creek  is
located in hydrologic region 2, Appalachian Moun-
tains and Highlands. The region is also described
in chapter HI.
   (3) Total watershed area. — Drainage size is
356 acres.
   (4) Latitude. — The latitude of Grits Creek is
35°N. This is necessary input since evapotranspira-
tion was found to be a partial function of latitude in
region 2.
    (5)  Season.  — The  seasons  for  rainfall
 dominated regions are: fall (September, October,
 November);  winter  (December,  January,
 February); spring (March, April, May); and sum-
 mer (June, July, August).
    (6) Compartment. — The entire watershed is
 considered to be unimpacted under existing condi-
 tions  (i.e.,  no  areas  affected  by previous
 silvicultural  activities).

    (7) Silvicultural state. — Watershed areas are
 grouped into zones of similar hydrologic response
 as identified  by silvicultural or vegetational state.
 For Grits  Creek,  the only silvicultural state is
 "forested." There is a single silvicultural prescrip-
 tion for the existing condition consisting of a single
 silvicultural state  — forested.
    (8) Area, acres. — The silvicultural zone is
 "forested," and this forested area is 356 acres.
    (9) Area,  %. — This refers to the percentage of
 the prescription area in each silvicultural state. In
 this case, the forested area is 100 percent (1.00 as a
 decimal percent) of the prescription area.
  (10) Precipitation. — Enter estimates  of
 seasonal  precipitation to the nearest 0.1 cm.  For
 Grits Creek, precipitation averaged 23.3, 75.2, 60.5,
 and 27.0 cm  for fall, winter, spring,  and summer,
 respectively.  Analysis requires precipitation and
 evapotranspiration to be entered in centimeters.
  (11) Baseline ET. — Baseline evapotranspira-
 tion (ET) for  a latitude of 35°N is taken from figure
 III. 11.  Respective  values  for fall,  winter,
 spring, and summer are 20.1, 8.9, 13.0, and 39.1
 cm.
  (12) Basal area. — Since the leaf area index is
 known, basal area is not needed.
  (13) Leaf area index. — The leaf area index has
 been estimated as 6 for Grits Creek. Leaf area in-
 dex does not  change with seasons since leaf fall is
 taken into account when ET estimates are deter-
 mined.
  (14) ET modifier coefficient.  — Evapotran-
 spiration modifier coefficients, as functions of leaf
 area index and season, are obtained from figure
 ffi.16.  For undisturbed  forested  areas,  the  ET
 modifier coefficent is 1.0 for all seasons.
  (15) Rooting depth  modifier  coefficient.   —
Rooting depth modifier coefficients are taken from
figure in. 19 for an average soil depth. In this exam-
ple,  all rooting depth modifier coefficients  are
equal to 1.0.
                                              vm.5

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                        Table VI I 1.1.—A summary of information  required for  the  analysis  procedures.  Grits Creek watershed
Description of the
information
required
n format i on
requirements
by chapter!/
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology
Flow — hydrograph or flow
duration curve
Bankful
Basef low
Representative flows to be used to
establish suspended and bed load
rating curves
Width stream
Bankful
Baseflow (average width flowing
water)
Depth stream (bankful)
Water surface slope
Suspended sediment for representative
f lows
Bed load sediment for representative
flows
Channel stability rating
Orientation stream — azimuth
Low flow period (date)
Percent streambed in bedrock
Bedrock adjustment factor
Length reach exposed
Travel time through reach
0






















































X,P

X

X

X
X
X
X
X








X,P



X





X
X
X
p
X
X

N/fl
Uow«*- KacK . O.Sefe ; Middle. »-€ack •. o.Scfe -} (Lpptr beack ; 0.1 cfe
Ra.w« 3znt .10
0

N//I
Uowev reack : S.O ft ^ Middle veack '• 3.S ft. j u.ppcv rftitU. : 2.0 ft
N/fl
M/fl
Fujuve. ~3SL • I0
M//I
Faiv-
35°
Last coe«k of flugust
15%
Figure int.? J 0.15
Lower r«ick : 3,ooo ft 3 middle v«ack : 1,900 ft • u^per Knack •. l^ooo tt
Lower v-eaek : feSmiKi j wiicUf*. KacK ; so wiin ; Uf pev- >-eaok •• AS wm
-  P - Data provided  in this handbook
   0 - Optional data, not  required  for  analysis
   X - Usei—provided  data

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Table VI11.1.--continued
Description of the
Information
requ I red
Information
requ 1 rements
by chapter
III
IV
V
VI
VII
Information for watershed
Information on hydrology — continued
Normalized hydrographs
of potential excess water
Normalized flow duration curves
Date of peak snowmelt discharge
Map of drainage net
Presence of springs or seeps
Change stream geometry
Water surface slope
Bankful width
Bankful depth
P
P
0
X








X








X
X







X


X
X
X



X





M/fl
Rgure.Jt.a.a,
w/fl
Figure. 3fflL.f
M/fl

N/fl
N/fl
M/fl
Information on climate
Precipitation
Form
Annual average
Seasonal distribution
Storm intensity and frequency
Extreme event
1 yr, 15-minute storm intensity
Drop size
Precipitation — ET relationship
Wind direction

X
X
X




P
X

0

0
0

X
0



X


X


























Rain
ISC..O cm
7/1 i »/30 •• 33.3awt • u/ 1, »/AS , IS.SLc*. ', 3/t i. %, • <#.Sc«\ ; '/ -fe %, • 3?.oc^
N/fl

3.5 m/hr
M/fl
tt/fl
N/fl

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                                                                                 Table VIII .1.—continued
Description of the
information
required
1 nf ormat ion
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on climate — continued
Snow retention coefficient
Date snowmelt begins
Maximum snowmelt rate
Radiation
Solar ephemeris
Heat influx
Iso-erodent map for "R" factor
X,P
0
0










p


















p
p

M/fl
N/A
N/fl

Fi<,u.teJZlE.i
Ffguv-e3lL7
figure. IHE.lj 3oo
Information on vegetation
Species
Height
Overstory
Understory
Riparian vegetation
Presence phreatophytes
Crown closure (%)
Cover density
Leaf area index (pre)
Basal area
Basal area — Crimv relationship
Ground cover
X

X




p
X
0
p



X
X



X



X





X


















X

X
X
X

X





SotttWv ovd Cove tardtoood

80%
10 ft 4* 60#
aft 4 |a.tt
N/fl
Uoiuer >-e«c.K: J«% werslovy ,5°% iuiy , SS% anJevstery j
uppev >-eack: SO&wrsUy , so% u«dt«tvy
M/ft
C,
N//I
N/fl
Wo-ks^^t JC-l
3
t—I
(-H
00

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Table VI I I .1.— continued
Description of the
information
required

Percent transmission solar radiation
through canopy
Percent stream shaded by brush
Base line ET
ET modifier coefficient
Rooting depth
Rooting depth modifier coefficient
Information
requirements
by chapter
1 1 1
IV
V I VI
VI 1
Information for watershed
Information on vegetation — continued


X,P
P
X
P


















X,P
X




Tobi«s 301.0.1 *TJ3nL.o.tJfi3Ure3ar.o.i;ioui»- reacU. 57. p--« ,'S7. post j vn'iJJIc. Katk : 5% ore. ,
lo?o post j upp€r 1-eo.tk •' S % prt. , la% past
Lowev v«ack : 3-S % j widdk, wact.:^o% -} «fy«v- «ack <*>Ł%
Rgare. 3E- »
Fi9u.ve.3IL Ife
Average
Figav<. HL \9
Information on soils and geology
Depth soi 1
Percent sand (0.1-2.0 mm)
Percent silt and very fine sand
Percent clay
Percent organic matter
Soi 1 texture
Soi 1 structure
Permeab i 1 i ty/ 1 n f i 1 trat i on
Presence of hardpan
Nomograph for "K" factor
Baseline soil-water relationships
Soil -water modifier coefficients
Jointing and bedding planes
X









X,P
P


X
X
X
X
X
X
X
X
P



X


X



X
X



X


























Worksheet JE.l
Wov-lcsWei; 35C.1
Wovksln-ett OZ.-l
WorlcsWi HL.l
U)8»-lcsl»€€t m . 1
UJwIcskee"!: T3C . i
tOahlcsli€€"t 15T-1
llUovlts^ 3L .1 a«d tuo^slicet 3E .?
Wo
F,-^^. IE. 3
N/fl
W/fl
M/A

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Table VI I 1.1.—continued
Description of the
i nf ormat ion
required
Information
requ i rements
by chapter
1 1
IV
V
VI
VI 1
Information for watershed
Information on soils and geology — continued
Soi 1 s map
Previous mass movements
Number
Location
Unit weight dry soil
Del i very potential
Percent silt and clay delivered
Median size coarse material
0







X







X
X
X
X
X
F
X
X
















B^urelSniL.fi
M/fl
M/fl
M/fl
N/fl
M/fl
N/ A
N/A
Information on topography
Map (hydrologlc region)
Latitude
Size watershed
Elevation
Aspect
Slope
Length
Gradient
Dissection
Shape/ Irregu larity
Nomograph for "LS" factor
X
X
X
X
X






X





X
X

X
p
X






X
X
X

X










X
X





X



(Z.S&S map, fiau^TTTr.*/ s hydwiosic v^gioK A.
35°
356 acres
Ranges WA 3750 ib WO ft
SoJkiaest
East 53% -y w
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Table VII I .1.—continued
Description of the
i n format i on
requ ired
nformation
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on topography — continued
Surface roughness

X



fYlo
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Table VII I .1.—continued
Description of the
Information
required
Information
requirements
by chapter
1 1 1
IV 1 V
VI
VI 1
Information for watershed
Information on si 1 vlcu Itural activity — continued
Transportation system
Area disturbed
Location
Cut slopes (location and slope)
Fill slopes (location and slope)
Cut and fill vs. ful 1 bench
Ins lope vs. outs lope
Surface
Width
Gradient
Surfacing (amount and kind)
Road density
Harvesting system
Landings
Location
Size
Gradient
Ground cover
Time for vegetative recovery of
disturbed surfaces

X
X











X
X




X
X
X
X
X
X

X
X
X

X

X
X
X
X
X





X





X
X













































Figuve. uniL . i -lcsli«<,t or. a.
Figure. 3ZflL. 2. o*d tuifrtstaei H .1*
tofrUe^tlT.a.jlttatk'affft-aoft • slope • I7<# - /€.

U ft tr J3ft
0% fe 1%
Bore, eairtk.
N/A
TvticW yawlin^
' VJ
Rauire. "OTTT . 2- avid to«4slve«t 31 . 2. -} along wxuls
\jOo4cskeet UC.2- ; vat-iclok
WovUheel JE.a j v/ariotJt
Wov4cstieetl!r. X
M/fl

-------
   (16) Weighted adjusted ET. — The weighted
 adjusted ET is calculated by multiplying baseline
 ET [col. (11)], ET modifier coefficient [col. (14)],
 rooting depth modifer coefficient  [col. (15)], and
 area as a decimal percent [col. (9)]. Weighted ad-
 justed ET values for fall, winter, spring, and sum-
 mer are calculated as 20.1, 8.9, 13.0, and 39.1 cm,
 respectively.

   (17) Weighted adjusted seasonal ET.  — The
 sum of weighted adjusted ET values [col. (16)] for a
 season equals the weighted  adjusted evapotran-
 spiration for that season. Values are in centimeters
 rounded off to one decimal place.
                Weighted adjusted seasonal ET
Season
Fall
Winter
Spring
Summer
                              20.1cm
                               8.9cm
                              13.0 cm
                              39.1cm
   (18) Water available for seasonal streamflow.
 — The difference  between  weighted  adjusted
 seasonal ET [col. (17)] and seasonal precipitation
 [col.  (10)]  is the water potentially available for
 seasonal streamflow. For Grits Creek, fall, winter,
 summer, and spring potential streamflows were
 3.2, 66.3, 47.5, and -12.1 cm, respectively.
   (19)  Annual  ET. — The  sum  of  adjusted
 seasonal ET values [col. (17)] is annual ET. This is
 81.1 cm for Grits Creek.
   (20) Water available for annual streamflow.
 — The sum of water available  for  seasonal
 streamflow values [col. (18)] is the water available
 for annual streamflow. This is  104.9 cm for Grits
 Creek.
   Water Available For Streamflow—After
        Proposed Silvicultural Activity


  Step  2. — The second step in the hydrologic
evaluation of Grits Creek is to estimate the water
available  for  streamflow  if the  proposed
silvicultural activity is implemented. The neces-
sary  steps in worksheet  ffi.2 are detailed below.
(Numbers in parentheses refer to items or columns
in the worksheet.) Since  the acreage cut does not
change for the two management alternatives, the
analysis is the same.
   (l)-(5). — Same as worksheet ELI.
   (6) Compartment. — For the proposed condi-
tion of Grits Creek, there are two compartments:
impacted and unimpacted.  The impacted  com-
 partment includes those areas affected directly or
 indirectly by the proposed silvicultural activities,
 while the unimpacted compartment includes areas
 unaffected by the proposed silvicultural activities.
    (7) Silvicultural state. — Watershed areas are
 grouped into zones of similar hydrologic responses
 as identified by silvicultural or vegetational state.
 For the proposed condition of Grits Creek, the un-
 impacted compartment  has  one  silvicultural
 state—forested. For the impacted  zone, there are
 two—clearcut and thinned. As with the existing
 condition, there is  one silvicultural prescription.
 However, this  prescription  consists  of three
 silvicultural   states  — forested,  clearcut,  and
 thinned.
    (8) Area, acres. — For the proposed condition,
 the silvicultural  states are forested, clearcut, and
 thinned with respective areas of 84, 180,  and 92
 acres.
    (9) Area, %. — The area of each silvicultural
 state in column  (8) is divided by  item (3), total
 watershed area, and rounded off to  the third
 decimal place. In this example, decimal percentage
 for forested,  clearcut, and thinned zones and are
 0.236, 0.506,  and 0.258, respectively.
   (10) Precipitation.  — Seasonal precipitation to
 the nearest 0.1 cm is entered by the user. For Grits
 Creek, mean seasonal precipitation was 23.3, 75.2,
 60.5, and 27.0 cm for fall, winter, spring, and sum-
 mer, respectively.
   (11) Baseline ET. — Baseline ET is the same for
 each silvicultural state within a season. The values
 taken from figure HI. 11 for a latitude of 35°N are
 20.1, 8.9,  13.0, and 39.1 cm for fall,  winter, spring,
 and summer seasons,  respectively.
   (12) Basal area. — Since the leaf area index
 (LAI)  has been estimated,  basal area data are un-
 necessary.
   (13) Leaf area index. — Leaf area index (LAI)
 values  have   been  estimated  by  a professional
 forester as 2  and 3 for clearcut and thinned areas,
 respectively.

  (14)  ET modifier coefficient. — Evapotrans-
piration modifier coefficients, as functions of  leaf
area index and season, are obtained from figure
in.16.  In  this example,  the modifier coefficients
are:
Season
Fall
Winter
Spring
Summer
Forested
1.00
1.00
1.00
1.00
Clearcut
0.81
0.65
0.60
0.69
Thinned
0.90
0.76
0.72
0.84
                                             VIII.13

-------
  (15)  Rooting  depth  modifier coefficient. —
Rooting depth modifier coefficients are taken from
figure ni.19 for  an average soil depth. Here, all
rooting depth modifier coefficients are equal to 1.0.
  (16) Weighted adjusted ET. — Multiplication
of baseline ET,  ET  modifier coefficient,  rooting
depth modifier coefficient, and area as a decimal
percent  yields adjusted  ET values as  follows:
Season       Forested   Clearcut     Thinned
Fall           4.74cm       8.23cm     4.67cm
Winter         2.10cm       2.93cm     1.75cm
Spring         3.07cm       3.95cm     2.41cm
Summer       9.23cm      13.65cm     8.47cm
  (17) Weighted adjusted seasonal ET.  — Sum-
mation  of adjusted ET  values  by activity  yields
weighted adjusted seasonal ET for the watershed.
Fall, winter, spring,  and summer values are 17.6,
6.8, 9.4, and 31.4 cm, respectively.
  (18) Water available  for seasonal streamflow.
—  The  difference  between  weighted  adjusted
seasonal ET  and  seasonal precipitation  is water
available for  seasonal streamflow. The respective
values are  5.7, 68.4, 51.1, and -4.4  cm for  fall,
winter, spring, and summer,  respectively.
  (19) Annual ET. — The sum  of weighted ad-
justed seasonal ET values [col.(17)] is annual ET.
This is 65.2 cm.
  (20)  Water available for annual streamflow.
— The sum of column (18), seasonal streamflow, is
equal to water  available for annual  streamflow.
This is 120.8 cm.
Flow Duration Curve  Development—Existing
                  Conditions
  Step  3.  — The  third  step  in  the  hydrologic
evaluation  is to estimate the flow duration curve
for the existing condition. The necessary steps out-
lined in  worksheet  III.3  are  detailed below.
(Numbers  in  parentheses  refer to the  items  or
columns on the worksheet.)
   (1),  (2). —  Same as worksheet III.l.
   (3) Water available for annual streamflow —
existing condition.   —  This  value  has  been
calculated in worksheet III.l, item (20), to be 104.9
cm.
   (4)  Annual  flow   from duration  curve  for
hydrologic region.  — Figure III.22 gives the  an-
nual flow for watersheds in hydrologic region 2 as
72.0  cm using 11  points  to calculate the area
beneath the curve.
    (5)  Adjustment  ratio.  —  Estimated  water
 available for annual streamflow divided by flow,
 represented by the flow duration curve, equals the
 adjustment ratio. The adjustment ratio is rounded
 to the third decimal place and used to correct the
 given flow  duration  curve  to  equal the expected
 yield. For Grits Creek, it is:
                104.9
                 72.0
=  1.457
    (6)  Point number. — This  is the numerical
 order of points used to define the flow  duration
 curve.
    (7)  Percent of time  flow is equaled or ex-
 ceeded. — These values are read at equidistant in-
 tervals  along the X-axis of figure III.22. The inter-
 val is a function of the number of desired points
 [i.e.,  if 11  points are used, the interval is 100/(11-
 1)].
    (8)  Regional flow. —  These are the Y-axis
 values of figure III.22 corresponding to the X-axis
 values in column (7). This column is not necessary
 if a flow duration curve for the existing condition is
 available.
    (9) Existing potential flow.  — Regional flow
 [col.  (8)] is multiplied by the  adjustment  ratio
 [item (5)] to give the existing potential streamflow.
 If a flow duration curve for the existing condition is
 available, no correction is necessary. Column (9) is
 plotted versus column (2) to yield the flow duration
 curve for the existing condition (fig. VIII.3).
    (10) Existing potential flow  (cfs). — Conver-
 sion of  cm/7 days to  cubic feet per second (cfs)  is
 accomplished by  multiplying  column (7) x area
 (acres)  x 0.002363 for 7-day intervals.
     Flow  Duration  Curve Development-
     After Proposed Silvicultural Activity
  Step  4.  — The  final step  in the hydrologic
evaluation of Grits Creek is  to estimate the 7-day
flow duration  curve for  conditions after the
proposed silvicultural activity has been conducted.
The necessary steps outlined in worksheet III.4 are
detailed as  follows. (Numbers in parentheses refer
to the items or columns on the worksheet.)
   (1), (2). — Same as worksheet UI.2.
   (3) Watershed aspect code. — The dominant
aspect of Grits Creek  is southwest.  Hydrologic
characteristics dictate that, for the purposes of flow
duration curve calculation, an aspect of west be as-
signed a code  of zero for the  watershed (this
eliminates the aspect adjustment).
   (4) Existing condition LAI.  — Existing LAI
has already been given  as 6.
                                              VIII.14

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I
i—'
01
                                                           Alternative A or B
                                     20        30         40         50         60        70        80



                                        PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED
90
100
                           Figure VIII.3.—Annual How duration curves for existing and alternative A or B conditions, Grits Creek watershed.

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   (5) Proposed condition LAI. — Proposed con-
dition leaf area index is an area weighted index for
the silvicultural states which for this example are
forested, clearcut, and thinned areas. Leaf area in-
dex values are  from worksheet  III.2, column  (13).
  The  weighted  post-activity index can be
calculated as:
weighted  forest + weighted clearcut
                + weighted thinned
                = weighted average
  or
 (6 X 0.236) + (2 X 0.506) + (3 X 0.258) = 3.2
   (6) Change in LAI. — The  difference between
existing and proposed condition leaf area indices
yields the change in leaf area index. In this case, it
is 6 - 3.2 = 2.8.
   (7) Rooting depth modifier  coefficient. — For
Grits  Creek, the rooting depth modifier coefficient
is 1.
   (8)-(12). — The least squares equation  coef-
ficients for the example are found in table in.4.
  (13)-(15). — Same as columns (6), (7), (9), and
(10) of  worksheet III.3, respectively.
  (16) b0 . — This is item (8) found in table III.4.
  (17) biQj. — Item (9)  X column (15).
  (18) b2CD. — Item (10) X item (6).
  (19) bsAS. — Item (11) X  item (3).
  (20) b4RD. — Item  (12) X item (7).
  (21) AQj. — Sum of columns (16), (17),  (18),
(19),  and (20).
  (22) Qi + AQj. — Column (15) + column (21).
  (23) Q; +  AQi (cfs). — Column (22)  x area
(acreas) x 0.002363 for 7-day intervals. This is the
predicted flow  duration  curve  for  the  proposed
silvicultural activity when plotted against column
(14) (fig. VII.3).

      SURFACE EROSION ANALYSIS

  The  quantity of surface  eroded  material
delivered to stream channels from sites  disturbed
by the proposed silvicultural activities is estimated
in two stages. First, the quantity of material that
may be  made available from a disturbed site is es-
timated using  the  Modified  Soil  Loss  Equation
(MSLE).  Second,  a  sediment  delivery  index
(SD i  ) is estimated. When this is applied to the es-
timated quantity  of  surface  eroded  material
available, an estimate of the quantity of material
that may  enter a stream channel is obtained.
       Erosion Response Unit Delineation

  Topographic maps (figs. VIII.4 to VIII.7) have
been prepared for the Grits Creek watershed, fol-
lowing steps 1 through 7 as discussed in chapter IV.
These  maps show the drainage net, hydrographic
areas, soil groups, and silvicultural activities. Road
locations for management alternatives A and B are
shown in  figure  VIII. 1.  An  enlarged map of
hydrographic area 13 (fig. VIII.8) shows the com-
posite of cutting units, roads, stream channels, and
soil groups used for the soil erosion and sediment
delivery example problem.

  Steps 1-7. — Prepare topographic maps (ch. IV).
   Step 8. —  Set  up  worksheets for  estimating
 potential sediment load from surface erosion.
   Worksheets IV.1 and IV.2, have been prepared
 with field data for Grits Creek management alter-
 native  A. Individual  soils  in the  Grits  Creek
 watershed have  been grouped  where there exist
 similar texture,  organic matter, structure,  and
 permeability characteristics. Worksheet IV.1 shows
 the  three soil  groups  used  for  surface  erosion
 evaluation. Data on worksheet IV.l  should not
 change when different  management alternatives
 are evaluated for the watershed.
   Worksheet IV.2 displays various types of data
 needed for evaluating the effects of management
 alternative  A  for  Grits  Creek watershed,
 hydrographic area 13. Individual erosion response
 units are identified and listed. A different erosion
 response unit is created for each change in manage-
 ment activity, each design change for a given ac-
 tivity (e.g., a road change from a cut-and-fill design
 to a complete  fill for a stream crossing), or each
 change in environmental parameters affecting ero-
 sion (e.g., an change in soil characteristics).
   Worksheet IV.3 is a summary of the values used
 in the MSLE and sediment delivery index for ero-
 sion response units in hydrographic area 13 of the
 Grits  Creek  watershed.  The values for  both
 management  alternatives  are obtained using the
 steps and discussions which follow. Only values for
'alternative A are used  to illustrate methods for
 solving the equations,  however, values for alter-
 native B  are similarly determined.
   Step 9. — List each erosion source area and
 number by erosion response unit.
   For the Grits Creek watershed, the response
 units have been  coded as follows. The treatment
 types are selection cuts (SC), clearcuts (CC), and
                                             VHI.16

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                      1 mile
Figure VIII.4.—Drainage n«t, GrIU Creek watershed.
                      VIII. 17

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     ~—Si ;_1.;  -•!';.,--jT^sg?
                    1 mile
Figure VIII.5.—Hydrographlc areas, Grito Creek watershed.
                    VIII.18

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                   1 mile
Figure VIII.6.—Soil groups, Grits Creek watershed.
                   VIII.19

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                                          [    ] Clearcut
                                                Selective Cut
                      1 mile
Figure VIII.7.—Silviculture! treatments, Grits Creek watershed.
                       vm.2o

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   Uncut UC13.1' CC132
                                                              UC = Uncut
                                                              CC = Clearcut
                                                              SC = Selective cut
                                                                R =Road
Figure VIII.8.—Enlargement of example hydrographlc area showing Individual erosion response unMs.
                                     vin.2i

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roads (R). There are no landings, because logs will
be yarded to various locations along the side of the
road  and onto  the road surface.  The  example
hydrographic area is number 13. The disturbance
types are numbered (e.g., clearcut CC13.1, clearcut
CC13.2) to identify them in the following evalua-
tions  for soil loss and sediment delivery.
Using The Modified Soil Loss Equation (MSLE)


  Step 10. — Working with each erosion response
unit individually, determine for each source  area
(silvicultural activities and roads) the values to be
used for each of the following variables:
  R    — Rainfall factor
  K    — Soil erodibility factor
  LS   — Length-slope factor
  VM   — Vegetation-management factor
  Area — Surface area of response unit
  Values for these factors are entered on worksheet
IV.3 using the following procedures.


Rainfall Factor

  For  the Grits Creek area, R = 300  (fig. IV.2.)
This R value is the same over the entire Grits Creek
area and will be used for all erosion  response units
and both  management alternatives.
Soil Erodibility Factor

  The K  value can  be  estimated  using the
nomograph in figure IV.3, or by using equation
IV.4. The data for soil group 2 needed to compute
the  K value using equation  IV.4  are found on
worksheet IV. 1.  K must be determined for both
topsoil and subsoil. For disturbances which enter
the subsoil, such as roads, the subsoil value of K
must be  used.
  Application of the equation to determine the K
factor is shown in the following example for topsoil
in soil group 2. Because of inflections in the family
of curves on the  nomograph (fig. IV.3) for percent
sand, the equation cannot be used when silt plus
very fine sand exceeds 70  percent.
  K  =  (2.1 X  10-6) (12-Om) M1-14
         + 0.0325 (S-2)  + 0.025 (P-3)   (IV.4)
 where:
   Om  = % organic matter
   M   = (% silt + % very fine sand) (100 - % clay)
   S    = structure code
   P    = permeability code
   Substituting values for topsoil (soil group 2) from
 worksheet IV. 1 into equation IV.4:
   K    = (2.1  X 10-6)  (12-4) [40 (100-20)]1-14
           + 0.0325 (2-2) + 0.025 (2-3)
   K    = 0.14
Length-Slope Factor

  The  length-slope factor, LS, is a combination
factor which incorporates the slope  gradient and
the length of the  eroding surface into a single fac-
tor. The LS factor must be estimated for each ero-
sion response unit.
  Two methods may  be used to estimate the LS
factor on straight slopes. One is to  use equation
IV.8 to derive the estimated LS value. The second
method utilizes a nomograph (fig. IV.4) to estimate
the LS  value.
  The cutting units (SC13.1, SC13.2, CC13.1, and
CC13.2) are each different  in regard to  slope
gradient and length. Therefore, LS for each cutting
unit must be evaluated separately. Using equation
IV.8 and data from worksheet IV.2,  the LS value
for CC13.1 is calculated as follows for.slope length X
=  132 feet  and slope gradient s = 12 percent.
                                                   T e _ / x  Y  A>-43 + °-30s + 0.043s2\
                                                   AJO — I 	1   I 	1
                                                        \72.6y   \        6.613      /
           10,000
        10,000 + s2,
                                         (IV.8)
where:
  X    = slope length, in feet
  s    = slope gradient, in percent
  m   = an exponent based on slope gradient from
         equation IV.6
Using data from worksheet IV.2:
LS  =
         72.6
              °'5 /0.43  + 0.30(12)  + 0.043(12)2
                              6.613
         10,000
LS = 2.05
        /    10,000    \
        \10,000 +  (12)2/
                                              VHI.22

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Similar calculations are made for erosion response
units SC13.1,  SC13.2, and CC13.2.
  To compute the length-slope value for the road
sections (R13.1, R13.2, and R13.3), the equation for
irregular slopes is used in  this example. An alter-
native method using graphs (figs. IV.5 and IV.6) is
discussed in chapter IV. The LS equation for roads
is:
LS
                                  72.6
                                          (IV.9)
  The number of calculations can be reduced by
simplifying equation IV.9 to:
LS
      1
                                         (IV.9.1)
      =  entire length of a slope, in feet
      =  length of slope to lower edge of j^h seg-
         ment, in feet
      =  slope segment
      =  slope gradient, in percent
      =  dimensionless slope steepness factor for
         segment j  defined by

      S.  = (0.043s2 + 0.30s. + 0.43)76.613
  m  =  an exponent based on slope gradient
  n   =  total number of slope segments
  For the road R13.1, using values in worksheet
IV.2 and assuming that no sediment is deposited on
the road surface,  the computations are as follow:

Slope segment 1  (cut)
  A,   =3.5 feet
  A i -i =  0.0 feet (there are no preceding slope seg-
         ments, hence length is 0.0 ft)
  s   =  1707r
  m   = 0.6 (for  slopes on construction sites; see
        eq. IV.6)
         S,  =
               0.043s2  + 0.30s +  0.43
                       6.613
                                                      substituting for s:
                                                      c     0.043(170)2 + 0.30(170)  + 0.43
                                                      &i =
                                                                        6.613
                                                     Substituting S, A, and m values for j = l into equa-
                                                     tion IV.9.1 to the right side of the summation sign
                                                     gives:
                                                       196
                                                            (3.5)1-6 - (0)
                                                                         1.6'
                                                                                     10,000
                                                                 (72.6)
                                                                       0.6
                                                                                   10,000  + (170)2/
                                                       = 28.59
                                                     Slope segment 2 (roadbed)
                                                       A2   = 3.5 +  12.0 =  15.5 feet
                                                       A2_i = 3.5 feet
                                                       s    = 1%
                                                       m   = 0.6 (for slopes on construction sites)
                                                              S2  =
                                                                   0.043s2 + 0.30s + 0.43
                                                                            6.613
                                                     substituting for s:
                                                              0.043(1)2  + 0.30(1)  + 0.43
                                                         S2	—	—	 =  0.117
                                                                         6.613
                                                     Substituting S, A, and m values for j=2 into equa-
                                                     tion IV.9.1 to the right side of the summation sign
                                                     gives:
                                                    0.117

                                                     = 0.65
'(15.5) L6  - (3.5) l*
v    (72.6) °-6
                                                                                  10,000
                                                                                       -I-
                                                     Slope segment 3 (fill)
                                                       A3  = 3.5 + 12.0 + 4.5 = 20.0 feet
                                                       A3_t = 3.5 + 12.0 = 15.5 feet
                                                       s   = 100%
                                                       m  = 0.6 (for slopes on construction sites)

                                                                   0.043s2 +  0.30s  + 0.43
                                                                             6.613
                                                    substituting for s:
   0.043(100)2 +  0.30(100) + 0.43
=  - =
             6.613
                                               VIII.23

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Substituting S, X, and m values for j=3 into equa-
tion IV.9.1 to the right of the summation sign gives:
gives:
  69.6
       /(20.0)16 -  (15.5)u
             (72.6)
                           10,000
                      10,000 4- (100)2
   =  107.54
Solving  the  entire  equation  IV.9.1, using  the
calculated values where:
        X =  3.5 +  12.0 + 4.5 =  20 feet
then:
  LS =
 1
    (slope seg. 1  + slope seg. 2

+  slope seg. 3)
      = — (28.59  + 0.65  + 107.54)
          20

       = 6.84
  A similar LS calculation is made for road R13.5.
Road R13.2, however, is a fill across a stream chan-
nel and becomes two problems, each with two seg-
ments.  Each segment starts at the middle of the
road surface, and the second segment includes one
of the fill slopes. An average LS value from both
halves of the road is used  as the final LS value
(1.81) to be entered on worksheet IV.3.

Vegetation-Management Factor

  The vegetation-management factor (VM) is used
to evaluate effects of cover and land management
practices on  surface erosion over the entire slope
length used for the LS factor. VM factors are deter-
mined for all cutting units and roads.
  (1)  Cutting units. — Worksheet IV.2 has the
field data used for calculating a VM factor for the
clearcut units (CC13.1 and CC13.2) and the selec-
tive cut units (SC13.1 and SC13.2).  Example
calculations are shown for  clearcut CC13.1.  The
cutting  unit is divided into two areas based on the
presence or absence  of logging residues. A ground
cover  of slash and other surface residues covers 55
percent of the unit (wksht. IV.2). The remaining 45
percent is scattered with open areas of bare soil and
soil duff mixtures averaging 15 feet in diameter.2

  "^Information about the amount of residue is often expressed in
tons per acre. Maxwell and Ward (1976) have published photos
and tables for parts of Oregon and Washington which relate
visual appearance of a site with the volume  of residue and
amount of ground cover.
  In the 55 percent of the area (CC13.1) covered by
slash and other surface residues, fine tree roots are
uniformly distributed  over 99 percent of the area.
In the 45 percent of clearcut area CC13.1 that is
open, fine tree roots are uniformly distributed over
80 percent of the open area. All of the overstory and
understory canopy has been removed.
  Using worksheet IV.4, first, enter percent area as
0.55 and 0.45 for area covered by residues and open
area, respectively. Separate calculations are made
for the logging residue areas and open areas.
  Second, the logging slash  represents the mulch
and close growing vegetation. Because slash varies
in density, assume that small openings a few inches
in diameter exist over 40 percent of the surface.
from figure IV. 9, the  60 percent cover provides a
mulch factor of 0.25. The 45 percent of CC13.1  that
is open is assumed to have 45 percent of the surface
protected  by widely scattered slash. Using figure
IV.9, a mulch factor of 0.35 is found for this situa-
tion.

  Third, zero canopy cover gives a canopy factor of
1.0 for both areas (fig. IV.8).
  Fourth, evaluate the role  of fine roots that are
remaining in the soil. The slash area has fine roots
uniformly distributed over 99 percent of its surface
area and figure IV.  10 shows a corresponding fine
root factor of 0.10. The open area has fine roots un-
iformly distributed  over 80 percent  of its area;
figure IV.10 gives a  corresponding value of 0.12.
  Fifth, determine if the open areas are connected
with each other such that water can flow downslope
from one to another (ch. IV). In this example, the
open areas are isolated from each other by bands of
logging residue,  requiring the use of a sediment
filter strip  factor  of  0.5  (see  "Sediment Filter
Strips" section of "Chapter IV: Surface Erosion").
If these sediment filter strips did not exist, a factor
of 1.0 would be  used.

  Sixth, using worksheet IV.4, multiply the  VM
subfactors for logging residue (0.55)  (0.25) (1.0)
(0.10) = 0.0138.  Similarly for the open area: (0.45)
(0.35) (0.12) (0.5) =  0.0095. The overall VM factor
for CC13.1 is the sum of the two factors: (0.0138) +
(0.0095) = 0.023.
  Similar  calculations  are  made for  CC.13.2,
SC13.1,  and  SC13.2.  Values  are  shown on
worksheet IV.4.
                                             (2) Landings. — No landings are planned for
                                           Grits Creek.
                                              VIII.24

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  (3) Roads. — The VM factor must represent two
conditions on the road areas: (1) the road running
surface,  and (2)  the cut-and-fill  banks that are
needed (fig. IV.7).
  The average width of disturbed  surface for road
R.13.1 is 1.8 + 12.0 + 3.1 = 16.9  ft
  Running surface  12-° ft = 0.7101 = fraction of
                   16.9 ft            total width

  Cut  slope  1-8 ft  = 0.1065 = fraction of total
            16.9 ft
                               width
  Fill slope
     3-1 ft  = 0.1834  = fraction of total
    16.9 ft              width
   The weighted VM factor for the road R13.1 is
 calculated and shown on worksheet IV.6. Similar
 calculations have been made for roads R13.1 and
 R13.5.
 Surface Area Of Response Unit

  Total surface area within each  treatment
 unit—clearcuts, selective cuts, and roads—is given
 in worksheet IV.2 and is entered on worksheet IV.3.
 All other  MSLE  factors  are also  entered into
 worksheet IV.3. Total potential onsite soil loss is
 computed by multiplying all the MSLE factors on
 worksheet IV.3.
  The infiltration rate used in determining the R
factor is the maximum rate at which water could
enter a soil. In actual situations, the water entry
rate will usually be somewhat lower than the in-
filtration  rate and  can be  based  on  the  soil
permeability  with  consideration  for  effects  of
various management practices.
  Using data from worksheet IV.2 and footnotes
from worksheet IV.7, the calculations for CC13.1
are:

F = (2.31  X  10-5 ft2 hr )  (2.5 in/hr - 2.0 in/hr)
     \            m sec/

      (132 ft + 0 ft)
                                           F   = 0.0015 ftVsec

                                              2.  Texture of eroded material  is based on the
                                                 amount of very fine sand, silt, and clay shown
                                                 on worksheet IV. 1. For this case, it has been
                                                 assumed  that one-half of the clay will form
                                                 stable aggregates,  with the remaining clay in-
                                                 fluencing the sediment delivery index. For soil
                                                 group 3  topsoil,  the  following calculations
                                                 were made:
                                                  texture of
                                                  eroded material
                                                                                     + % silt
              Sediment Delivery
  Step 12. — The computed potential sediment is
delivered  to the  closest stream channel  using a
sediment delivery index (SDj). Worksheet IV. 7 is
used to organize the data for each erosion response
unit for each factor shown on the stiff diagram (fig.
vm.9).
  1. Water availability for sediment delivery is
     calculated using equation IV.12 for each ero-
     sion response unit:
                   F = CRL
                                (IV.12)
where:
  F   =
  R   =

  L   =
available water (ftVsec)
[1 year, 15 minute storm (in/hr)]  - [soil
infiltration rate (in/hr)]
[slope length distance of disturbance (ft)]
+ [slope  length  from  disturbance  to
stream (ft)]
   C  = 231 X  10-B
             ft2 hr
             in sec
                                                                    + % very fine sand

                                                                   = f  +  26 +  19

                                                                   = 57
  3. Ground cover is the percentage of the soil sur-
     face with vegetative  residues and stems in
     direct contact with the soil. The ground cover
     on  the  area  between a disturbance and  a
     stream  channel  is  determined  from  field
     observations and  used  for the sediment
     delivery  index.  For  CC13.1,  53  percent  is
     shown on worksheet IV.2 for ground cover.
  4. Slope shape  is  a  subjective  evaluation of
     shapes between  convex and concave. From
     worksheet IV.2, for CC13.1 the slope shape is
     concave.
  5. Distance is the slope length from the edge of a
     disturbance to a stream channel. For CC13.1
     (wksht.  IV.2) the distance is 0.0, because the
     disturbance extends to the channel.
                                              VIII.25

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  6. Surface roughness is a subjective evaluation
     of soil  surface  microrelief ranging  from
     smooth to moderately rough. Worksheet IV.2
     shows  a moderate  surface  roughness for
     CC13.1.
  7. Slope gradient  is the percent slope between
     the lower boundary of the disturbed area and
     the stream channel. Worksheet IV.2 shows a
     gradient of 12 percent for the disturbed area.
  8. Site specific is an optional factor that was not
     used in this example. See chapter IV for more
     discussion of this factor.
  The tabulated factors for CC13.1  (wksht IV.7)
are plotted on the appropriate vectors of the stiff
diagram (fig. VIII.9) as discussed in chapter IV.
Use any one of several methods to determine the
area bounded  by the  irregular polygon that is
created when points on the stiff diagram are joined.
The area  of the polygon for this example is 107.9
square  units.  The stiff diagram has 784 square
units. The percentage of the total area enclosed by
the polygon is:
            /107.9
            \  784
(100)  = 13.8%
  Entering the  X-axis  of  the  probit curve  (fig.
IV.23) with 13.8 results  in a sediment delivery in-
dex (SDX) of 0.02. This is the estimated fraction of
eroded material that could be delivered from this
disturbance to the stream channel.
  Step 13. — Find the estimated quantity of sedi-
ment (tons/yr)  delivered to a stream channel by
multiplying  surface soil  loss  by  the  sediment
delivery  index  (wksht.  IV.3)  for each  erosion
response unit.
  Step 14. — Using worksheet IV.8, tabulate quan-
tities of  delivered sediment (tons/yr)  for  each
hydrographic area  by  the  erosion  source. When
completed, this table provides a summary of sur-
face  erosion sources and estimated quantities  of
sediment production from each hydrographic area.
  Step 15. — Totals and percentages are shown on
worksheets IV.8. The total quantity of delivered
material is entered on table Vin.2.
Differences Between Management Alternatives


  A second set of worksheets IV.2 to IV.8 show data
and results of calculations for Grits Creek alter-
native B. Specific differences between alternatives
                              A and B can  be seen by comparing values in the
                              two sets of worksheets. For example, alternative B
                              results  in more of the total surface area covered
                              with residues  and mulch and more fine roots. The
                              results of these effects are shown on worksheet IV.3
                              as the VM factor. For alternative A, CC13.1, VM =
                              0.023 as compared to VM = 0.003 for alternative B,
                              CC13.1. The lower VM for alternative B indicates
                              that vegetative  materials on the ground are more
                              effective in reducing erosion than they  are in alter-
                              native A. There are similar differences in the VM
                              factor for other cutting units and roads. The net ef-
                              fect is a total  of 34.2 tons/yr for alternative A and
                              6.7 tons/yr for alternative B  (wksht. IV.8).
TOTAL POTENTIAL SEDIMENT ANALYSIS


  The following steps are diagrammatically shown
in figure IV.9.

  Step 1. —The stream reach characterization will
be obtained on the lower reaches of the third-order
stream channel on main  Grits Creek.
  Step 2. — See figure VIII.3, flow duration curve
for Grits Creek.
                                     Suspended Sediment Calculation

                                Step 3. — Establish suspended sediment rating
                              curve.
                                a.  Obtain  sediment rating  curve from the
                                   measured  depth integrated suspended sedi-
                                   ment  sampling and  concurrent stream dis-
                                   charge measurements. A plot of these figures
                                   is shown in figure VIII. 10.
                                b.  log  Y = 0.61 + 0.96 log Q
                                       r2 = 0.98
                                c.  Channel stability rating:  fair. The analysis
                                   outlined by Pfankuch (1975) was used to ob-
                                   tain this value. A  correlation  between the
                                   various ranges in stream channel stability and
                                   sediment rating curves as explained in appen-
                                   dix  VLB was  obtained for the  Grits Creek
                                   watershed. Figure Vni.ll indicates the chan-
                                   nel stability threshold limit which is the up-
                                   per  limit for a fair rating.
                                              VHI.26

-------
         Percent Ground
             Cover
   Texture of
Eroded Material
                                                   100-
Available
  Water
Slope
Shape
                                                                                           0.10
                                                    Site
                                                  Specific
        Delivery Distance
              feet
   Surface
  Roughness
   Slope
  Gradient
                  Figure VIII.9.—Stiff diagram for alternative A CC3.1, Grits Creek watershed.
                                              VIII.27

-------
SUSPENDED SEDIMENT (mg/l)
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0.1
0.2    0.3  0.4 0.5
                                 1          2345         10
                                    STREAM DISCHARGE (cfs)
                                                                 20    30  40 50
100
                     Figure VIII.10.—Sediment rating curve, Grit* Creek watershed.
                                             VIH.28

-------
300
200
100
SUSPENDED SEDIMENT (mg/
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0.1
0.2    0.3 0.4 0.5
1          2345         10
    STREAM DISCHARGE  (cfs)
20    30  40  50
                                                                                                        100
     Figure VIII.11.—Channel •lability threshold limit* In relationship to the eedlment rating curve, Qrlte Creek
                                               watershed.
                                               VIII.29

-------
  Step  4.  — Calculate pre-silvicultural  activity
potential suspended sediment discharge.
  a. Using worksheet  VI. 1, columns (1)  through
     (4). Use sediment rating curve (fig.  VIII.10)
     for concentration values in column 3.
  b. Record  the total of 11.6 tons/yr on worksheet
     VI.3, line A.
  Step  5. — Calculate post-silvicultural  activity
potential  suspended sediment discharge  (due to
streamflow increases).
  a. Using worksheet VI.1, columns (1),  (5),  (6),
     and (7).
  b. Record  the  total  of 19.6  tons/yr due only to
     flow increase on worksheet VI.3, line B.
  Step  6. — Convert selected limits (mg/1) into
units compatible with the analysis (tons/yr).
  Maximum limits were set using the stream chan-
nel stability-sediment rating curve relationship for
the watershed. Since the channel  stability rating
was fair, the threshold limit between the fair and
poor stability classes was used (fig. VIII.ll). For ex-
ample, using 20 cfs, a value of 70 mgA from the poor
curve and 190  mg/1  from the  channel stability
threshold limit curve are obtained, resulting in a
120 mgA increase. The  concentrations from  the
threshold line  between fair and poor were used in
worksheet IV. 1, column (8). Using columns (2), (8),
and (9)  of worksheet VI.1, a total of 25.5 tons/yr is
obtained and recorded on worksheet VI.3, line  C.


             Bedload Calculation
  Step  7. — Bedload measurements were taken,
but because of  the heavily armored  channel,  no
bedload  was caught in a Helley-Smith sampler.
Bedload rates appear to be negligible except in the
event of a flood.
  Step  8. — Not applicable because no bedload
material was caught in sampler.
  Step  9. —  Calculate  pre-silvicultural activity
potential  sediment   discharge  (suspended  and
bedload).
  a.  From step  4, (suspended sediment) = 11.6
     tons/yr.
  b.  Record on  worksheet VI.3,  line K.
  Step   10. —  Not  applicable—no bedload
material.
     Total Potential Sediment Calculation


  Step 11. — The proposed activity contributed no
sediment from soil mass movement processes.
  Step  12.  —  Not  applicable—no  bedload
material.
  Step  13.  —  Not  applicable—no  bedload
material.
  Step 14. — Determine  total delivered tons of
suspended sediment from surface erosion.
  a. Surface erosion source fc  34.2 tons/yr
  b. Record  on worksheet  VI.3, line D.I.
  Step  15.   —  Compare  total  potential  post-
silvicultural activity suspended sediment (mg/1) to
selected  limits (tons/yr). On  worksheet VI.3:
  Add totals of:
    Surface erosion (line D.I)        34.2 tons/yr
    Total post-silvicultural activity
       suspended sediment discharge due
       to flow related increases
       (line B)                       19.6 tons/yr
    Soil mass movement (washload)
       (line D.4)                      0.0 tons/vr
             Total                   53.8 tons/yr
  Subtract the total pre-silvicultural
    activity suspended sediment discharge
    (line A)  from the previously
    determined figure               11.6 tons/yr
  The remainder is the total increase  in
    potential suspended sediment
    discharge (line I.I)              42.2 tons/yr
  Subtract the maximum allowable increase in
    suspended sediment discharge (line C)
    from the total increase in potential
    suspended sediment discharge (line  I.I)
                                    25.5 tons/vr
  The remainder is the net change (this
    may be either a positive or negative
    number)                      +16.7 tons/yr

  Step 16. — Total potential post-silvicultural ac-
tivity sediment discharge—all sources:
  Summation of  steps 5, 10,  11, and 14.
  a. Post-silvicultural  activity suspended  sedi-
     ment (flow
     related increases)
     (step 5,  wksht. VI.3, line B)  =  19.6 tons/yr
  b. Bedload—not  applicable.
                                              VIII.30

-------
  c. Soil mass movement volume
      —not applicable.
  d. Surface erosion (step 11,
      wksht. VI.3, line D.I =       34.2 tons/yr
                            Total  53.8 tons/yr
  Record on line L, worksheet VI.3.

  Step  17. — Total potential sediment discharge
increase resulting from silvicultural activity:
  a. Subtract total potential pre-silvicultural ac-
     tivity sediment discharge (step 9) from total
     potential post-silvicultural activity sediment
     discharge (step 16)
   Total post-worksheet IV.3,
   line  L                          53.8 tons/yr
   Total pre-worksheet  VI.3,
   line  K                          11.6 tons/yr
   Total potential sediment
   increase                        42.2 tons/yr
  b. Record on worksheet VI.3, line M.
  The total  potential sediment  increase is also
recorded  in  table VIII.2 for  management  alter-
native A  and table Vin.3  for management alter-
native B.


               Channel Impacts

  Step  18. —  Not  applicable  to Grits  Creek
because direct channel impacts from debris,  width
constrictions,  or gradient  changes  are  not  an-
ticipated with the proposed action.
  Step  19. — Not applicable.
  Step 20. — Not applicable.
  Step 21. — Not applicable.
        TEMPERATURE ANALYSIS


  Grits Creek was segmented into four reaches for
temperature evaluation purposes (wksht. VII.2 and
fig. VIII.12). This was  necessary because  of the
variety of  silvicultural  activities—partial  and
clearcut—and  length of  stream involved—more
than 1 mile from headwater to mouth. The first
reach consists  of an  open meadow, 600 feet long,
with no vegetative shade. The trees to be cut near
the mouth are distant enough from the stream that
they provide no  shade. Therefore, the proposed
silvicultural activity will not directly impact water
temperature near the mouth. The partial cut area
is approximately 3,800 feet along the center portion
of the watershed. Since the evaluation procedure is
valid for reaches up to 2,000  feet, this section  of
stream was divided into two reaches—a lower reach
2,000 feet  long,  and a middle reach of 1,800 feet.
The headwater portion of the stream is in a clear-
cut; the upper reach is 1,000 feet long.
  Following is the evaluation for each stream reach
and an integration of the individual reaches to ar-
rive at an estimated  maximum daily  potential
temperature increase at the mouth. The analysis is
the same for both management alternatives since
the exposure to  the stream has not changed.


                 Lower Reach
Computing H, Adjusted Incident Heat Load

  Step 1. — Determine H (i.e., incident heat load)
based upon latitude of site,  critical time of year
(month and day), and orientation of stream.
  Step 1.1. — Select the solar ephemeris that most
closely approaches the latitude  of the site, 35°N
(fig. VII.2).
  Step 1.2. — Locate  the declination in the solar
ephemeris (fig. VII.2) that corresponds to the date
when maximum water  temperature increase is an-
ticipated: last week August;  therefore, a declina-
tion of +10°.
  Step  1.3.  —  Once  the  declination,  +10°, is
known, determine the azimuth and solar angle for
various  times  during the  day  from  the solar
ephemeris  (fig.  VII.2)  and  record the values in
worksheet VII. 1. Azimuth readings are found along
the outside of the circle and are given for every 10°.
Solar angle (i.e.,  degrees above the horizon) is in-
dicated  by the concentric circles and  ranges from
0° at the outermost circle to 90° at the center of the
circle. The time is indicated above the +23°27'
declination line  and is given  in hours, solar time.
Note that the time of day shown on worksheet VH.l
is given as daylight savings time (DST).
  Step 1.4. — Evaluate the orientation of the sun
(i.e., azimuth and angle determined in step 1.3
above)  with  the  stream,  and  determine what
vegetative shading effectively shades  the stream.
To  do this,  compare stream  effective width  with
shadow  length.  Determine the maximum solar
angle (i.e., maximum  radiation  influx to stream)
                                              VIII.31

-------
                  WATER TEMPERATURE PRIOR
                TO SILVICULTURAL ACTIVITY 63°F
              GROUND WATER TEMPERATURE 48°F
 o
 CD
 DC Ł
    o
 CD .2

 D
AT = 5.1°F
Qy = 0.2 cfs

Ty = 63
                                                5.1°F = 68.1°F
                            = 68.1°F
.
O *i
  .
— p oo
"      "
QM = 0.3 cfs (of this 0.05 cfs is groundwater)

TM = (0.05 cfs) (48° F) + (0.25 cfs) (68.7° F)
                                                  (0.05 cfs) + (0.25 cfs)
                                       = 65.3°F
                         TM=65.3°F
"5
f 
-------
that will occur when the stream is exposed follow-
ing the silvicultural activity. Height of the existing
vegetation immediately adjacent to the stream is
80 feet.

  Step 1.4.1. — The direction the shadows fall
across the stream will determine effective width of
the stream.
  Effective width is computed using the following
formula:
            measured average stream width
  K\V  =
         sine
               azimuth stream
                  azimuth sun |
                           (VII.4)
  Azimuth of the particular stream is 35°. For ex-
ample, at  12 p.m.  (wksht.  VII. 1) EW would be
equal to:
      KVV =
                    4 ft
            sine I 35° -  148°
                  = 4.4 ft
The absolute value of azimuth of the stream sub-
tracted from  the azimuth of the sun must be less
than a 90°-angle. Should the difference exceed 90°,
subtract this absolute value from 180° to obtain the
correct acute angle. Then the sine is taken of this
computed acute angle.
  Step 1.4.2.
the formula:


         S =
  Shadow length is computed using
 height vegetation
tangent solar angle
(VII.5)
For example, at 12 noon,  S would be equal to:
        S = 80 ft/tangent 62° = 42.5 ft
  Summary of steps 1.4.1 and 1.4.2: The existing
trees that  are scheduled to be cut provide shade to
the streams. The only time when trees might not
shade the stream is 2:15 p.m., when the stream's
effective width is infinity (sun is oriented with the
stream) and the shadow length  is only 46.2 feet.
Therefore, removal of the  vegetation would  result
in exposure of the water surface to increased solar
radiation.
  The  proposed  silvicultural activity would have
the maximum impact on  water temperature at 1
p.m. (solar noon) when  the solar angle (65°) and
radiation are greatest.
                                         Step  1.5.  —  Topographic  shading should  be
                                       evaluated to determine if the water course would be
                                       shaded  by  topographic features. For topographic
                                       shading, the percent slope of the ground must ex-
                                       ceed the percent slope of the  solar angle,  (i.e.,
                                       tangent of the solar angle). In this  case,
                                         side slope east = 53%
                                         side slope west = 50%
                                         Solar  angle expressed as percent  for:
                   8a.m. DST
                   9 a.m.
                   1 p.m.
                   5p.m.
                   6 p.m.
                       32%
                       58%
                       214%
                       58%
                       32%
                                         Therefore, topographic shading is possible before
                                       9 a.m. and after 5 p.m. There is no topographic
                                       shading the rest of the day.
  Step 1.6. — Calculate the incident heat load for
the site.  This is obtained from reading the values
shown on figure VII.7. The following is done to read
values from this figure:
  Step 1.6.1. — Select the correct curve (shown in
fig.  VII.7)  obtained  from  the  correct  solar
ephemeris  (fig.  VII.2):  in  this example,  35°N
latitude, given a declination of +10° results in a
solar angle of 65°. Note that the midday value will
always have  an  orientation, i.e., azimuth, of due
south.
  Step  1.6.2.  — In figure  VII.7,  interpolate
between  the 70° and  60° curves to obtain the 65°
value.
  Step 1.6.3. — Determine the critical period,
which in step 1.4 was found to be 1 p.m. DST.
  Step 1.6.4. — Find the average H value. In this
example, the travel time through the reach is es-
timated to be 1 hour,  so it is not necessary to find
an average value. From figure  VII.7,  with  a 65°
midday angle, the H value for  1 p.m. is approx-
imately 4.3 BTU/ft2-min.
  Step 1.7. — Because bedrock acts as a heat sink,
reducing the  heat load absorbed by the water, the
H value  must be corrected for this  heat  loss.
  C is obtained from figure VII.9. In the  example,
bedrock  comprises 75 percent  of the  streambed;
therefore, H should be reduced by 15 percent.
                                              VIII.33

-------
Hadjusted = t% WH1 + t%B d-00 - C) H]    (VII.6)
where for Grits Creek:
  W   = percent streambed without bedrock
       = 25%
  H   = unadjusted heat load = 4.3 BTU/ft2 - min
  B   = percent streambed with rock =  75%
  C   = correction factor from figure VII.9 = 0.15
  Therefore,
  H       =  [0.25 X 4.3 BTU/ft2-min]
    adjusted    + [Q ?5(1 00 _  Q 15) x 4 3 BTU/ft2
              — min]
  Hadjusted =  3.82 BTU/ft2-min
Computing Q, Stream Discharge

  Step 2. — Determine stream discharge following
the  proposed  silvicultural  activity  during  the
critical summer  low-flow period when  maximum
temperatures  are anticipated. In this example, a
pre-activity  baseflow  measurement  during  the
critical summer period was taken. Discharge dur-
ing the critical period was 0.5 cfs.
Computing A, Adjusted Surface Area

  Step 3. — Determine the adjusted surface area of
flowing water  exposed  by  the  proposed
silvicultural activity.
  Step 3.1. — Total surface area  of flowing water
                  Va, =  LW           (VH.7a)
where:
  L   = length of reach exposed
  W   = width of flowing water
  A,,,ta|  =  2,000ft X5ft
         =  10,000 ft2
  Step 3.2. — Total surface area shaded by brush
Ashade brush =LW (9? shaded by brush only) (VII.7b)
           =  2,000 ft X  5 ft  X 25%
           =  2,500 ft2
  Step 3.3. — Surface area exposed under current
vegetative canopy cover: correct for transmission of
light through the  existing  stand that has a 90-
percent overstory crown closure and a 50-percent
understory crown closure. Since only vertical crown
closure values are available, estimate the percent-
age transmission  of solar radiation through the
 canopy. In using figure VII.D.l for crown closures
 greater than 70 percent, assume a 5-percent trans-
 mission of solar radiation.
   "presently exposed  ~~ '•"total    shade brush'
                     X % transmission through
                     existing vegetation   (VII.7c)
                  = (10,000 ft2 - 2,500 ft2)  X 5%
                  = 375 ft2
   Step 3.4. — The adjusted surface area that will
 be exposed to increased solar radiation if all vegeta-
 tion is removed is:
   "adjusted = "total ~~ A presently exposed
           =  10,000 ft2 - 375 ft2
           =  9,625 ft2

   Step 4. — Estimate AT, maximum potential
 daily temperature increase in °F if all vegetation is
 removed from lower reach. Solve equation VII.3a.
AT
      A       H
    	  adjusted  adjusted
                Q
                            X 0.000267   (VII.3a)
  Aadjusted = 9,625 ft2
  Had]Us»ed =3.82 BTU/ft2- min
         Q =  0.5  cfs
           =  19.6°F
 AT = (9'625
                                                                             BTU/ft.2-min)
                    0.5 cfs
  The  proposed  silvicultural  activity  will  only
result in  a  partial cut of the overstory, leaving a
vertical crown closure of 50 percent.  The under-
story will not be cut; however, some loss is to be ex-
pected during removal of the overstory. Understory
vertical  crown  closure  remaining  after the
silvicultural activity is expected to be 45 percent. It
is estimated that the percent transmission of solar
radiation through the canopy will be 15 percent.
The brush shading  the  stream  will remain.
Therefore,
 A total           =  2,000ft X 5ft
                 =  10,000ft2
Ashade brush       =  2,000 ft X 5 ft X 25%
                 =  2,500ft2
                 =  (10,000ft2 - 2,500 ft2) X 85%
                 =  6,375ft2
^ shade remaining
  canopies
 'adjusted
                = A    —  (A
                    total    v  presently exposed
                  ~*~ " shade brush
                           remaining canopies
                 =  10,000 ft2 - (375 ft2 + 2,500 ft2
                    h 6,375 ft2)
                 =  750ft2
                                                VIII. 34

-------
  Step  4.  — Estimate  AT, maximum potential
daily temperature increase in  °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VII.3a.
  AT =
"adjusted " adjusted
       Q
X 0.000267
(VII.3a)
             Aadjusted   = 750 ft2
             Halted   = 3.82BTU/ft2-min
             Q         = 0.5 cfs
AT =
     (750 ft2) (3.82 BTU/ft2-min)
              0.5 cfs
                             X 0.000267
    =  1.5°F
                Middle Reach
Computing H, Adjusted Incident Heat Load

  Step 1. — The only difference between the lower
reach and the middle reach, when estimating H, is
that the average width of flowing water is reduced
from 5 feet to  3.5 feet. Thus, the effective stream
width values would  change,  but the final H ad-
justed value  would  remain  unchanged—3.82
BTU/ft2-min.
                                               Step 3.2. — Total surface area shaded by brush
                                                                                     (VE.7b)
A u _,      =  LW (% stream shaded by
  shade brush    ,        ,  .
             brush only)
           =  1,800 ft X 3.5 ft X 40%
           =  2,520ft2
  Step 3.3. — Surface area exposed under current
vegetative canopy cover: correct for transmission of
light through the existing stand that has a 90-
percent overstory crown closure and a 55-percent
understory crown closure. Since only vertical crown
closure values are available,  estimate the percen-
tage of solar radiation through the canopy. Again it
is estimated that only 5-percent transmission  of
solar radiation is allowed through the canopies (fig.
VH.D.1)

A presently exposed = (Atotal ~~ Ashade brush / '° trans-
                mission through existing
                vegetation              (VTI.7c)
              = (6,300 ft2  - 2,520 ft2) X  5%
              = 189ft2

  Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion  is removed  is:
                    = "total ~ A presently exposed
                    = 6,300 ft2 - 189 ft2
                    = 6,111ft2
  Step 4.  — Estimate AT,  maximum  potential
daily temperature increase in °F if all vegetation is
removed from middle reach. Solve equation VII.3a
                                                        ^adjusted
Computing Q, Stream Discharge

  Step 2. — A pre-silvicultural activity baseflow
measurement  during the critical  summer period
was taken for  this  reach. Discharge  during the
critical period was 0.3 cfs.
Computing A, Adjusted Surface Area

  Step 3. — Determine the adjusted surface area of
flowing  water  exposed  by  the  proposed
silvicultural activity.
  Step 3.1. — Total surface area of flowing water
               total
            =  LW
            =  1,800 ft X 3.5 ft
            =  6,300ft2
                                        (VII.7a)
                                               AT =
                     ^adjusted *~* adjusted
                           Q
                                                    X  0.000267
                                                                                            (VII.3a)
                                                             Aadjusted = 6,111ft2
                                                             H adjusted = 3.82BTU/ft'-min
                                                             Q       = 0.3 cfs
                                                    AT =
                                                           (6,111 ft2) (3.82 BTU/ft2-min)
                                                             0.3 cfs
                                                                                  X  0.000267
                                                 = 29.7°F
                               The  proposed  silvicultural activity  will  only
                             result in a partial cut of the overstory, leaving a
                             crown closure of  50 percent. The understory will
                             not be cut; however, some loss is expected during
                             removal of the overstory. Understory vertical crown
                             closure is expected to be 50 percent. It is estimated
                                               VIII.35

-------
that the percent transmission of solar radiation
though  the canopy will be 10 percent.  The brush
shading the stream will remain.
Therefore,
Atotal
As
  hade brush
         canop.es
        'adjusted
                    = 1, 800 ft X 3.5 ft
                    = 6,300ft2
                    = 1,800 ft X 3.5 ft X 40%
                    = 2,520ft2
                    = (6,300 ft - 2,520 ft) X 90%
              — Atotal   ( "presently exposed
                '  Asna(je brush
                '  "shade remaining canopies/
              = 6,300 ft2-(189 ft2
                + 2,520 ft2+ 2,402 ft2)
              = 189ft2
   Step 4. — Estimate AT,  maximum potential
 daily temperature increase in °F if the proposed
 silvicultural activity is implemented.  Solve equa-
 tion VII. 3a.
    AT =
           ^adjusted **adjusted
                   X  0.00027
(VH.3a)
             "adjusted ~  189 ft
             Hadjusted =  3.82BTU/ft2-min
             Q       =  0.3 cfs

         (189 ft2) (3.82 BTU/ft2-min)
       = 0.6°F
                   0.3 cfs
                  Upper Reach
Computing H, Adjusted Incident Heat Load

   Step 1. — The only difference between the lower
and middle reaches and the upper reach, when es-
timating  H, is that the average width of flowing
water is reduced to 2.5 feet. Because of this, the ef-
fective  stream width values would change, but the
final  H  adjusted  value  would remain un-
changed—3.82 BTU/ft2-min.
 Computing Q, Stream Discharge

   Step 2.  — A pre-silvicultural activity baseflow
 measurement was taken for this reach during the
 critical summer period, resulting in a value of 0.2
 cfs.
            Computing A, Adjusted Surface Area

              Step 3. — Determine the adjusted surface area of
            flowing  water  exposed  by  the  proposed
            silvicultural activity.
              Step 3.1. — Total surface area  of flowing water

                 Atotal =  LW                       (VII.7a)
           =  1,000 ft X 3.0 ft
           =  3,000ft2
   Step 3.2. — Total surface area shaded by brush
 Ashade brush = LW (% stream shade by brush only)
           = 1,000 ft X 3.0 ft X 65%      (VH.Tb)
           = 1,950ft2
   Step 3.3. — Surface area exposed under current
 vegetative canopy cover; correct for transmission of
 light through the existing stand that has  an 80-
 percent overstory crown  closure and  a 60-percent
 understory crown closure. Since only vertical crown
 closure values are available, estimate the percent-
 age of solar radiation through the canopy. It is es-
 timated that only 5-percent  transmission of solar
 radiation  is  allowed  through the canopies (fig.
 VII.D.1).

A presently exposed  = (Atotal ~ "shade brush  ) % trans-
                mission through existing vegetation
               = (3,000 ft2-1,950 ft2) X 5%
               = 53ft2

  Step 3.4. — The adjusted surface area  that will
be exposed to increased solar radiation if all vegeta-
tion is removed is:
         A adjusted   =  Atotal  ~ A presently exposed
                    = 3,000 ft2 - 53 ft2
                    = 2,947 ft2

  Step 4.  — Estimate AT,  maximum potential
daily temperature increase in  °F if all vegetation is
removed from the upper reach. Solve  equation
VH.Sa.
                                                AT =
                    A       T-f
                    "adjusted n adjusted

                           Q
                         X 0.000267
                                         (VH.Sa)
                                                          Aadjusted = 2,947ft2
                                                          Hadjusted = 3.82BTU/ft2-min
                                                                Q = 0.2 cfs
                                              AT =
                                                     (2,947 ft2) (3.82 BTU/ft2-min)
                                                               0.2 cfs
                                                 X 0.000267
                                                  = 15.0°F
                                               VHI.36

-------
  The proposed silvicultural activity will be a com-
mercial clearcut resulting in the complete removal
of the overstory  and understory  canopies. The
dense laurel and  rhododendron brush along  the
stream will not be removed.
Therefore,

        Atotal   =  1,000 ft X  3 ft
               =  3,000ft2
    Ashade brush   =  1,000 ft X  3 ft X 65%
               =  1,950ft2
                  Atotal  ~ (A presently exposed
                 + A shade brush )
               =  3,000ft2 - (53ft2 + 1,950ft2)
               =  997ft2

  Step 4. — Estimate  AT,  maximum potential
daily temperature  increase in  °F if the proposed
silvicultural activity is implemented. Solve equa-
tion VII.3a.
      "adjusted
        A       H
        • .uljuMed ** adjusted
        - - -
              Q
                                        .__
                      X 0.000267      (VII.3a)
           Aadjusted = 997ft2
           Hadju,«ed = 3.82BTU/ft2-min
                Q = 0.2 cfs

       (997 ft2) (3.82 BTU/ft2-min)
 AT =  - - - x 0.000267
                  0.2 cfs
    =  5.2°F
          The Mixing Ratio Formula


  The lower reach of Grits Creek is to be partially
cut, with a potential temperature increase of 1.5°F.
The middle reach will also be partially cut, with a
potential temperature increase of 0.6°F. The upper
reach is to  be  clearcut,  with  a  potential
temperature increase of 5.1°F.
  An  estimate  of the integrated impact on the
water temperature  is necessary so that a com-
parison can be made with the water quality objec-
tive—allowing a maximum temperature increase of
3°F.
  A mixing ratio formula will be used to estimate
the downstream temperature impacts. The water
temperature before  the  silvicultural  activity was
63°F,  and the groundwater temperature measured
at a spring was 48°F.
  For the upper reach,  the  estimated water
temperature increase, 5.1°F, is added to the pre-
silvicultural activity water temperature 63°F, to
estimate the temperature of the water as it leaves
the proposed clearcut area, 5.1°F + 63°F = 68.1°F.
  The water temperature  entering the middle
reach will  be  68.1°F. The  estimated  water
temperature increase in the middle reach is 0.6°F.
However, the two values should not be added to get
an estimate of the water temperature leaving the
middle reach because groundwater influxes within
this reach will mitigate the water temperature in-
crease caused by  the proposed silvicultural ac-
tivity. The following mixing ratio formula should
be used:
                                                           Tn =
                                        (VH.9)
where:
  TD =  temperature downstream where the mid-
         dle and lower reaches are separated
  DG =  discharge of groundwater, 0.05 cfs
  D   =  discharge immediately below partial cut,
         0.30 cfs
  TG =  temperature groundwater, 48°F
  TT =  stream temperature below  silvicultural
         activity which is  equal to  the
         temperature   above  plus  computed
         temperature increase, 68.7°F
                  T_ — T -I- AT
                  T — I AI L\ i
  TA =  temperature streams above treated (par-
         tial cut) area, 68.1°F
  AT =  temperature increase, 0.6°F
Therefore,
         (0.05 cfs)  (48°F) + (0.25 cfs) (68.7°F)
     D          (0.05 cfs)  + (0.25 cfs)

      =  65.3°F
  The water temperature entering the lower reach
will  be 65.3°F. The estimated water  temperature
increase in the lower reach is 1.5°F. Again, the two
values should  not  be added as explained above.
The  following mixing ratio formula should be used:
                   DGT(; + DTTT
              TI>  =   D  +D—         (vn.9)
where:
  TD =  temperature downstream where  lower
         reach ends
  DG =  discharge of groundwater, 0.05 cfs
  DT =  discharge immediately below partial cut,
         0.50 cfs
  TG =  temperature of groundwater, 48°F
                                             Vin.37

-------
  TT  = stream temperature below silvicultural
         activity  which  is  equal  to  the
         temperature  above plus computed
         temperature increase, 66.8°F
                TT = TA + AT
  TA = temperature stream above treated (par-
         tial cut) area, 65.3°F
  AT = temperature increase, 1.5°F
Therefore,
       (0.05 cfs) (48°F)  +  (0.45 cfs)  (66.8°F)
   °           (0.05 cfs)  + (0.45 cfs)
     =  64.9°F
  The estimated overall water  temperature  in-
crease at the mouth would be 1.9°F (64.9°F - 63°F
= 1.9°F). This value is entered in the tables Vffl.2
and VIII.3 for both management alternatives.

             ANALYSIS REVIEW


  The estimated outputs are summarized in tables
VHI.2 and VIII.3 for Grits Creek alternatives A and
B, respectively. These estimates must be compared
to the water quality objectives to determine if one
or both of the alternatives  are acceptable.
  In determining acceptability of the alternatives,
accuracy of the estimations must be considered.
The two major  sources of variation affecting ac-
curacy of outputs are: (1) models, which by their
very nature,  cannot completely represent all fac-
tors affecting the estimated output, and (2) quality
of input data —  there is a decrease in the accuracy
of the estimated output as the quality of the input
data decreases. Establishing an acceptable level of
accuracy for  the estimated outputs is left to the
professional judgment of a user who understands
the strengths and weaknesses of the  models and
data sets used.
  The  computed outputs for total potential sedi-
ment  from  all sources  and  the  potential
temperature changes are compared to the water
quality objective at  the mouth of the watershed.
The water quality objective for Grits Creek was to
maintain  channel stability, limit total potential
sediment discharge to 25.5 tons/yr,  and limit the
maximum temperature increase to 3°F. The post-
silvicultural activity total suspended sediment dis-
charge from all sources was 26.3 tons/yr for alter-
native B and 53.8 tons/yr for alternative A (tables
VIII.2 and VHI.3). Although alternative B resulted
in 0.8 tons/yr in excess of the allowable maximum,
it was judged to be within the accuracy range for
the data and  models used. Since both alternatives
were consistent  with temperature objectives, the
mix of controls in alternative B was considered ac-
ceptable from a  water quality standpoint.
                                             Vin.38

-------
                         Table  VIII.2



Summary of quantitative outputs for:  Pffo-nflJU/fc fl  (yl-'its
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soi 1 Mass
Movement :
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19


Output description
Water ava liable for
streamf low
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration
curve
Surface soi I loss
Sediment del i vered
Hazard index
Weight of sediment

Acceleration factor
Sediment discharge
due to flow
change
Total suspended sed
from a I I sources
to stream channel

Coarse >0.062 mm
Fine <0.062 mm
Total

Bed load
Suspended
Total
iment discharge
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
activlty
/0O cm
^^^_
/3./C»r,
A/.fl.
A/./)
$Łflf..-3
/M.
M.fl.
\^
\
CNo*.


0.0-W/Yr
It. t> ha/fi-
ll, (o W/yr
(U Uu/yr
\
""\^
Post-
activity
/ao.ffdn
/S.?cw
/3./crv»
A/-/).
W.fl.
fi3.3DL.3
3300 -U»/yr
3il (Ylass ^
^N

dO -fen^/r
/f.t-Us/yr
/?.t ^ns//r
sayW/xv
fQ.SL^HS/yr
AS'F
Chapter
reference
(worksheets)
JL/,2t2
JUJjUC.a
31,3^.*


HT.SjJT.V
jm.3
or.*


o>/ei«€iCtj
^^
"\^
1ZH.3 ];«e E
2T.3 CneF
XL. 3 ltn« A
2E.3 line 6
3Zt. 3 line 1C
TILS IW G.
3C.3 n«e A
hW Z.I +A
30Iv5 Ut W
anr.^
                            VHI.39

-------
                         Table  VI11.3



Summary of quantitative outputs for: fllternoenVC BJGvt'fc
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soil Mass
Movement :
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19


Output description
Water aval lable for
streamf low
annua
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration curve
Surface soi 1 loss
Sediment delivered
Hazard index
Weight of sediment
to stream channel

Coarse >0.062 mm
Fine <0.062 mm
Total
Acceleration factor
Sediment discharge
due to flow
change
Bed load
Suspended
Total
Total suspended sediment d scharge
from al 1 sources
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
activity
lotf cm
^\^_
/3.I cwt
A). A.
/U.fl
•ftjian:..*
w.fl.
N.fl.
\^
\
(Mo Ł.',(


0.0 4wtf/yf
//.fe kvu/yv
l/.t -fenj/yr
luWyr
\^
^\_
Post-
activity
fto.Łc»i
/s.?c»n
/3.1cm
N.fl.
M.fl.
XfanL.3
wo WKV
6.7 Jwts/^v

•^
Dloss IHsver
"**•

0.0 4ms/yr
/JltU^r
1WW/JV
36.3 ^Hi/yr
«7^«^r
/.SflF
Chapter
reference
(worksheets)
jc.i.JC.a.
ac.ijU.^
at 3^.^


xs/H-f
JSC.3
3JT.?


ieni:)

^\
3L.3 line *
tt.-8 lm«F
3lC..3lii%. A
5L.3hVitfi
3ZL.3 l|n«K
JBT^ f.^, A.
3E.3 'Ate A
IlM *.l* «
3ZL.3 U« m
3ff!.a-
                              vin.40

-------
                  Worksheets for Grits Creek
                     alternatives A and B
 Worksheets are  presented in numerical order with  all III.1-III.4
alternative A, followed by III. 1-III.4 alternative B; IV.1-IV.8 alternative
A, followed  by IV.1-IV.8 alternative B,  etc.
                              VIII.41

-------
                                                                   WORKSHEET I I I.1



                               Water available for streamflow for the existing condition in rainfall dominated regions
         (1)  Watershed name GnTs  Creek.
(2)  Hydrologic region
(3)  Total  watershed  area (acres)   oS(o    (4)  Latitude  3S
Season
name/
dates
(5)
Fal I
I ' '/3,
Winter
iv-y
vi fyt
Spring
r,-%
Summer
(,/ 8/
/ - /S|

Si 1 vicu 1 tural prescription
Compartment
(6)
Un impacted
Impacted
Total for se
Un impacted
Impacted
Si Ivicultural
state
(7)
Forested





ason
roi"Ł8TW





Total for season
Un impacted
Impacted
Fbr«4«
-------
Item or
Col. No.                              Notes
  (1)     Identification ot watershed or watershed subunit.

  (2)     Descriptions of hydrologic regions and provinces are given in text.

(3),(4)   Supplied by user.

  (5)     Seasons for rainfall dominated regions are fall  (September, October,
          November), winter (December, January, February), spring (March,
          April, May), and summer (June, July, August).

  (6)     The unimpacted compartment includes areas not affected by the
          si Iv[cultural prescription.  The  impacted compartment includes areas
          affected by the si IvicuItural prescription.

  (7)     Areas of similar hydrologic response as  identified and delineated by
          vegetation or si IvicuItural state.

  (8)     Supplied by user.

  (9)     Column  (8) 4  item (3).

  (10)    Measured or estimated by  the user.

  (11)    From  figures  111.10 to  111.12; or user supplied.

  (12)    Supplied by user.   Unnecessary  if leaf area  index  is known.

  (13)    From  figures  111.13 and 111.14; or  user  supplied.

  (14)    From  figures  111.15 to  111.17.

  (15)    From  figures  111.18 to  I I 1.20.

  (16)    Calculated  as  (11)  x  (14)  x  (15)  x  (9);  or user supplied.

  (17)    Seasonal sum  of  column  (16).

  (18)    Column  (10)  - column  (17).

  (19)    Sum of  column  (17).

  (20)    Sum of  column  (18).

-------
                                                                   WORKSHEET I I I.2




                               Water  available for streamflow for the proposed condition in rainfall dominated regions
(1)  Watershed name  GrviTs
                                                         (2)  Hydrologic region
(3)  Total  watershed area (acres)  3S"fe    (4) Latitude   35"
Season
name/
dates
(5)
Fal 1
fl-%
Winter
'*f-&
Spri ng
%-y*

Summer
tf-%1

Si I vicu Itural prescription
Compartment
(6)
Un Impacted
Impacted
Total for se
Un impacted
Impacted
Si Ivicultural
state
(7)
Posited

Clearcut
Th'mnfia


ason

Fovcsttd

Clear-cu;
Thinne*


t



Total for season
Un impacted
Impacted
PbresW

Clearwt
TKmneJ




Total for season



Impacted


Rvested

^QarCAi
Thinner






Total for season
Area
Acres
(8)
*4

180
93,


35fc
84

ISO
?3L


3S
-------
         Item or
         Col. No.                              Notes
           (1)     Identification of watershed or watershed subunit.

           (2)     Descriptions of hydrologic regions and provinces are given in text.

         (3),(4)   Supplied by user.

           (5)     Seasons for rainfall dominated regions are fall (September, October,
                   November), winter (December, January, February), spring (March,
                   April, May), and summer (June, July, August).

           (6)     The unimpacted compartment includes areas not affected by the
                   siIvicultural prescription.  The  impacted compartment includes areas
                   affected by the siIvicultural prescription.

           (7)     Areas of similar hydrologic response as  identified and delineated by
                   vegetation or siIvicultural state.

^         (8)     Supplied by user.

j^         (9)     Column  (8) T  item (3).
01
           (10)    Measured or estimated by the user.

           (11)    From  figures  111.10 to  I I 1.12; or user supplied.

           (12)    Supplied by user.   Unnecessary if leaf area  index  is known.

           (13)    From  figures  I I 1.13 and  111.14; or  user  supplied.

           (14)    From  figures  III.15 to  111.17.

           (15)    From  figures  111.18 to  I I 1.20.

           (16)    Calculated as  (11)  x  (14) x  (15)  x  (9);  or user supplied.

           (17)    Seasonal sum  of  column  (16).

           (18)    Column  (10) - column  (17).

           (19)    Sum of  column  (17).

           (20)    Sum of  column  (18).

-------
                                WORKSHEET  I I I.3

                  Flow  duration  curve  for  existing  condition
                            rain dominated  regions
(1 )  Watershed name
rifs  Creek
(2)  Hydrologic region
(3)  Water  available for  annual  streamflow  existing  condition  (cm)_

(4)  Annual  flow from duration  curve for  hydrologic  region  (cm)	

(5)  Adjustment ratio (3)/(4)  /VS7	
                                              7A.O
Point
number
i
(6)
/
X
3
1
S
(*
7
8
9
10
//

Percent of
time flow
is equaled
or exceeded
(7)
0
10
50
30

-------
                                                          WORKSHEET  I I I.4
                                            Flow duration  curve for  proposed  condition
                                       rain  dominated  regions—annual  hydrograph  unavailable
(1)  Watershed name  Gn-ils   C>r€e\C.

(4)  Existing condition  LAI   (e. 0
                  (2)  Hydrologic  region
           (5)  Proposed  condition  LAI
    3.2,
  (3)  Watershed aspect code (AS)_

(6)  Change in LAI  (CD)   3-8
(7)  Rooting depth modifier coefficient (RD)   /     (8)  bp -.03    (9)  bj  ".Q3    (10)  b?  -/3     (11)  b^  -03-    (12)  64,
                                                                                                                          .03
Point
number
i
(13)
1
2
3
*
5"
4,
7
8
9
10
II

Percent of
time flow is
equaled or
exceeded
(14)
O
10
20
30
*o
so
feo
70
80
JO
10V

Existing
potential
flow Qj
(15)
13.1
a?
J.S
9.O
/.8
(.0
.7
.fe
.Ą
.3
0

bQ
(16)
-.03
-.03
-.03
- .03
- 03
-.03
-.03
-.03
-.03
-.03
-.03

bl
.34,
.36
.34,
.34,
.3fe
.34.
.3fc

b3AS
(19)
0
0
0
0
0
0
0
0
0
0
0

b4RD
(20)
.03
.03
.03
.03
.03
.03
03
.03
.03
.03
.03

AQi
(cm)
(21)
-.03
.A4
AB
.30
.31
.33
.3+
.3*
•3T
.3S
.36


-------
                                                       WORKSHEET  IV.1

                                Soil  characteristics  for  the  6-rjTS
watershed
Soi 1 group
Top so i 1
1
Subsoi 1
Top so i 1
0
Subsoi 1
Topsoi 1
•*
Subsoi 1
E
-t- '-
c
CD O
U TJ 1
l_ C 0
CD ro •
CL U) CM
10
S"S"
-0
I- L. —
CD Q> •
CL > O
17
1(0
IS
17
1?
17
f. _ i
+- E
— to
in o
-t- 0) O
c in 1
 O
I?
H
ax
13
A(o
as
E
-t-
C CM
CD O
O >-O
U (D •
d> — O
CL O V
as-
/sr
10
10
asr
^0
Percent
organic
matter
V.o
1,0

-------
                                                                                                                1 of  3
           G-vVts  Creek
                                WORKSHEET IV.2

         watershed erosion response  unit management data
         sediment delivery index,  hydrographic area  13 ,
                                                                    for  use in the
                                                                     g/jgrnalive.
MSLE and
Erosion
response
unit
1. SC 13.1
2. 5C.I3.A
3. CCI3-/
4. J,on dip*.
                    = 43,560
/toad CA.O&&ZA a.
    -into a channel..
               It U>
                                                           fytom the. nut oft the. fioad  bzcauAe. Aedune.nt jj>

-------
                                                   2 of 3
WORKSHEET IV.2—continued
Area with surface residues
Percent
of total
area
1. MO
2. 15"
3. SS
4. (oO
5.
6. 0
1. 0
8. fcO
9.
10. &0
11. 0
12. Ł0
13.
14. O
15. O
16. foO
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Percent
of surface
with mulch
85
8S-
4>0
6,0

O
0
ss-

85-
0
86T

0
O
85-









Percent of
area with ,,.
f ine roots —'
?Y
n
9?
<*9

0
0
so

50
O
SO

O
0
SO









Open area
Percent
of total
area
60
55-
^5"
Ą0

loo
IOO

-------
                                                            WORKSHEET I V.2—cont inued
                                                                                                                 3 of  3
Average
mi n imum
height of
canopy
(m)
i. a.
2. X
^) -n.—
4. _
5.
6. a.
7. —
e. a.
9.
10. JL
11 . -
12. 2.
13.
14. 2.
15.
16. 0.
17.
is. a.
19. -
20. a.
21 .
22. —
23. -
24. —
25.
Time for
recovery
(mo )
4



















UMKMOUW












•














Average
d i st . from
disturbance
to stream
channel (ft)
O
o
O
o
/38



O



193



O



193




Overal 1
slope shape
between
d i sturbance
and channel
COMCAVC
COMCAUE
QONCAVE
COWCAVE
COMCAVE



STRftl&HT



COMCAl/fiT



STfcBI&HT



COMCAVE:




Percent
ground
cover in
f i Iter
strip
88
84>
?4
90
S?



0



SCo



0



94




Surface
roughness
(qual i-
tat i ve )
MODERATE-
MOOERflTE-
moDERATe
moDER-ATE
DlOOtefiTE



smooTH



(HODERftTe



smoorH



MOOEKATC




Texture of
eroded g,
mater i al — ^
(? silt +
clay)
y?
S7
S7
SO
39



38



SO



SO



SO




Percent
slope
between
disturbance
and channel
8
Ifo
la.
AO
8



IOO



Ib



100



/a.




<
-1 It  hat
                   been aAAum&d that k o& thu  c.la.ij lejncu.yu> on-b-tim  cu>  btabtt aggie.gateA  and tkat the, H.ut ofa the. clay pŁu6
                 *and and biXjt &nteA the. Ae.dime.nt de.ti.veAy

-------
                                                      WORKSHEET IV.3

                          Estimates  of  soil  loss and delivered sediment by erosion response  unit
                          for  hydrographic area   /3	 of   Grits   C.4>
^o.o
/./
3107


SD,

O.OA.
0-OX
o.oa.
o.o
o.oi
o.H
0.01


Del i vered
sed iment
(tons/yr)

O.OST
0.37
0.07
o.o
0.90
o.a,
3. a.


f—H
B
         - SC  - Section cut
            CC  - Cl&aAcut
              R  - Road

         -1   T  - Top* o^l
              S  -
          •21
of, two LS vaJLuu, one.
eac/i
             a
                                                             tke. n.oad,  Atasuting out tkn cn.nt&i tine, and including

-------
                                                                                                  WORKSHEET  IV.4
                                                                          Estimated  VM factors for siIvicuIturaI  erosion  response units
                                                                           Gr i"ts  Creek	 watershed,  hydrographic  area   /3	
Ol
CO
Logging residue arLea
Erosion
response
unit
SCI3.I
SCI3.-3.
CCI3. 1
CCI3.^
Mil CUT
BED
FILL
RI3.2. FILL
BED
FILL.
RI3.ST CUT
BED
FILL



Fraction
of
total
area
o.Mo
0.^
O.SS"
o.fco
0.0
o.o
o.feo
ofeo
o.o
O.fcO
o.o
0.0
o.fco



Mulch
(duff &
residue)
o./o
O.IO
0.25-
o.Ar
-
—
0.10
O.IO
—
O.IO
—
-
O.IO



Canopy
0.98^
0.98
1.0
1.0
—
—
0.88
O.SS
-
O.S8
—
-
1.0



Roots
O.IO
O.IO
OJO
O.|0
-
—
o.ai
o.ai
—
0.31
-
—
o.ai



Sub
VM
.003?
.00
J.o
0.3G
1.0
1.0
O.VI



                                           —  Canopy e^ecti  onŁi/ appty to open OHHOA  without neAJ-due.  and

                                           —  Example. caJLcvJLoJUioYi-   F/iom woikAhe.et  IV.2,  &5% 0(j the. iuAiJace. kaA match, ieav-Lng 151 without tnuUl-ch.   If, the. canopy
                                               -ci unibointy dii,t>iibute.d oueA 451 0|S  Ae. ioiaŁ nAea, the.n  oniy 151 0(j tke  cflwopy can coueA iKe atea wtifcocrf mutch.
                                               TVieAetfo/i.e:   (0.15) (0.45) (WO) -  71  o coveAtd bij the. canopy.   Thit, neAuttA in a
                                               l/M - 0.9S.

                                           —'. EnteA on uioiki>he.et IV. 3.
                                           —  VM fjOti load* il>  &ol a iecoveAe.d  condition.

-------
            WORKSHEET  IV.6
  Weighting  of  VM values for roads in
C»-ee<      watershed,  hydrographic area
13
Erosion
response
unit

KI3.I

RI3.2.

RI3.S
























Cut or fill
Fraction
of total VM
width

(OJ065) (0.88)

(0.0118} (o-3fe)
^ ^
(O.|b%) (|.0)
-» »• —























	
Roadbed
Fract ion
of total VM
wi dth

+ (0.7 ioi) CIA)

+ Co.7i^ (10]

+ Co.s^n) (\.o)





















\


Fi 1 1
Fract ion
of total VM
wi dth

+ (o.|g3
-------
                                                                          WORKSHEET  IV.7

                                               Factors  for  sediment delivery index  from  erosion response units  in

                                                &TUS  Creek	 watershed,  hydrographic area    /3	



Erosion
response
unit
SCI3.I

SCI3.2.
CCJ3.I
«ai
RI3-I
RI3.1
R.I3.S






Water (.
aval 1 abi 1 ity
o. ooa.
a/
O.003
iy
O.oolS
o.o
JJ
o.oia
o.ool J
o.oifc"^





Texture
of eroded
mater i al
47

57
*7
so
38
38
SO


Percent
ground
cover
between
disturbance
and channel
47

U,
53
47
47
O
53





Slope
shape
code
a*

3.S
2.S-
«
3.S"
3.0
3.S-



Distance
(edge of
disturbance
to channel )
(ft)
1

1
1
1
138
«*
l?3





Surface
roughness
code
i

I
i
i
Z
1
*•





Slope
gradient
($)
*

l\o
,Z
30
?
loo
^





Specific
site
factor
—

—
—
—
—
—
—




Percent
of total
area for
po 1 ygon
/a.a

J3./
13.1
—
1.0
30.9
8. 2,






^/
SD|
o.oi

o.oo.
o.oa.
i/
o.o
0.01
o./V
o.oj


Cn
Cn
                 I/ Majtimum J5 min. annual ttoim  oŁ  2.5 -in/hA.
                ~2/ InfrMxation note, ofi 2.0 in/hi  (baAnd on t>o-UL peAmiabillty].
                TJ ln(,iJUnaŁion note, of, 3.0 -Ln/kn.  ibaJ>e.d on &oiŁ
                ~4/ Infiltration note, of, 0.1 In/kn  (boAe.d on t>oJJL
                T/ EnieA on woAfeifieet IV. 3.
                ~6/ Wfeen uw-te/t avcMabi&ity -Us  Z«AO,  fke.n the. Ae.dime.nt deZtueAi/ -index -u  zeAo.

-------
                                WORKSHEET IV.8
          Estimated tons of sediment delivered to a channel  for each
hydrographic area and type of disturbance for  Gfjfo   Creek	 watershed,
                      Al+«t>n«cfl\/e,  A	
Hydro-
graphic
area
/
3,
3
4
5-
(o
7
8
?
10
II
U
/3
/
-------
                                                                                                              1  of 3
           Gnrijs  Cve&k
                                   WORKSHEET IV. 2

             watershed erosion  response unit management  data for  use in
             sediment  delivery  index,  hydrographic  area  13

                                                              the MSLE
                                                              .  S
                                                                   and
Erosion
response
unit
1. SCI3J
2. SCI3.2.
3. CC.I3J
4- CCI3.2.
5. R 13.)
5. CUT
7. BED
8- PILL
9. Rj3.au
10. FILL
11. 6ED
12. FILL
13. R|3.3
14. CUT
15. BED
16. FILL
17. RI3.4J/
18. FILL
19. BED
20. FILL
21. RJ3.S
22. ClCT
23. BEP
24. FILL
25.
Slope
length of
disturbed
area (ft)
IU
384.
133.
H8<4

3.5-
ia.o
4.5T

a.o
13.0
5.0

H.O
11.0
5.0

a.s-
ia.o
fe.o

8.0
ia.o
10.0

Slope
gradient of
disturbed
area (%)
9
It
is.
10

no
1.0
loo

IOO
0
JOQ

170
a.
JOO

loo
o
100

J*0
J
IOO

Length of
road
section
(ft)




543



a4



543



*6



6/4,




Average
width of
d isturbance
(ft)




Ife.Y
U
14.O
3.1
18.0
L<4
13.0
3.6,
IL.4,
a.o
//.o
3.fc
/*.o
l.g
ia.o
y.i
23.0
3.9
la.o
7J

Area
(sq.ft.)

























Area
(acres)
6.1
5-7
/.4
4.V
fl.Al



O-Ol



o.al



0.0 1



0.33




K
en
           —
           -1 1
     200
43,560
 4ecXion
between
       a b&uiam.
-into a cha.nn Ae.paSLate.d
                                                                        thu fi&>t o^ the. fioad foecmtie

-------
                                                                                                                2 of 3
                                                           WORKSHEET  I V.2~cont i nued
Area with surface residues
Percent
of total
area
1. HO
2. HS
3. 60
4. 65
5.
6. 0
7. 60
8. /OO
9.
10. (00
11 . 4,0
12. (GO
13.
14. 0
15. feO
16. /t>0
17.
18. 100
19. fco
20. loo
21.
22. 0
23. feo
24. |oo
25.
Percent
of surface
with mulch—/
100
|OO
loo
95-

O
8S
85"

85-
8S-
8Ł-

0
SS
85"

85"
85"
85-

0
85"
85-

Percent of
area with
fine roots
99
W
??
??

0
40
(00

loo
60
/OO

o
4o
loo

loo
Ł>0
loo

o
fco
|OO

Open area
Percent
of total
area
GO
S5-
^0
35"

100
40
0

0
40
0

100
40
0

0
40
0

too
40
0

Percent
of surface
with mu 1 ch
80
75-
8ST
SO

0
0



0


0
0



o


o
0


Percent of
area with
fine roots
11
11
11
11

O
60
IOO

100
60
loo

0
60
100

IOO
60
/OO

0
60
|OO

Are open areas
separated by
f i Iter strips?
yes
ves
YŁS
yes

wo
wo



wo


MO
NO



MO


WO
WO


Percent of
total area
with canopy
4S"
4S-
0
a

AST
0
as

as"
o
AS"

ar
0
as*

as
0
AS

0
0
0


en
00
         —  Not appreciable to scalped a/iaa4  unŁtŁ uegstation

-------
                                                              WORKSHEET I V.2—cont i nued
                                                                                                                    3 of  3
Average
mi n imum
height of
canopy
(m)
1- Ł
2- 4.
3.
4.
5.
6- 2,

8. 2_
9.
10. 2,
1 1 .
12. fl.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Time for
recovery
(mo )
J













UMKNOWfJ







i

















Average
dist. from
disturbance
to stream
channel (ft)
0
o
o
o
138



O



11 3












Overal 1
slope shape
between
disturbance
and channel
CONC/WE
COMCflvE
CoWCflVF
GONJCflVE
COM CAVE



STRfil&HT



CDNCRVE












Percent
ground
cover in
f i Iter
strip
fe7
Llo
S3
sn
47



O



S3












Surface
roughness
(qual i-
tat i ve)
mODERflTE-
mODERflTE
MODECOTF
MOOERflTE-
mooeRftTG"



smooTH



MOD CRATE












Texture of
eroded gi
material —
(? silt +
clay)
47
S7
57
50
3?



3S



s-o












Percent
slope
between
disturbance
and channel
8
1C,
ia.
ao
?



(00



IX












Ol
CO
         -1 It ha*
b on-b-Ltt t
   -band  and A

-------
                                             WORKSHEET  IV.3

                Estimates  of  soil  loss and delivered sediment  by  erosion response unit
                for hydrographic  area    / 3     of   G-rftS  Cr€€JC	 watershed
II
Erosion response
un it

SCJ3.I
seis.a
ŁC/3./
CC/3.JL
A/3.1
RI3.il
R (3. 5
RM
R.13.5*
Soil
unit-7

Tl
T3
T3
T&
SI
SI
S3
S3
S3
R

3oo
300
3oo
3oo
300
3oo
Sot)
3oo
300
K

0.0?
o./S
0.1*
O.H
O.a7
o.^
S.o
IS.«
0.08
aa.o
0.3)
7s.o
SD|

o.oa.
o.ox
O.OSL
0-0
o.oi
o-if
O.O/
OJ4»
O.OI
Del i vered
sed iment
(tons/yr)

O.OSL
0.13
o.oi
o
O.Ko
o.o|
o.aa
O.OS"
0.75-
SC -
CC -
 R - Road
-   T -
    S -
                   Co*
   a  &JUL
               two LS vainer, one.  faoti each koJLfa oŁ the. fiocid, Atasuting at the. c.e,nt&i tino, and

-------
                                                        WORKSHEET IV.4

                               Estimated VM factors  for  si IvlcuItural erosion  response units
                                Grits Creek.	  watershed,  hydrographic  area   13
Logging residue area
trosion
response
unit
SC.I3.I
SCI3.1
CC13.I
CCI3.X
ftlll^CttT
BED
FILL
RI3.3. FILL
BED
FILL
RI3.3 CUT
ge&
Pia
Ris.
o.?<|
l.o
l.o
0.87
0./8
—
—
1.0
-
O.S7
O.I?
—
—
1.0
—
0.87
0.1*
—
Roots
O.I
O.I
0.1
O.I
—
—
—
—
0.18
—
-
—
-
—
o.lt
-
—
—
—
F i 1 ter
strip
o.ff
o-s-
o.S
Q.S-
l.o
l.o
—
—
l.o
—
l.o
10
—
—
l.o
—
l.o
1.0
—
Sub
VM
.0034
.003?
.00)8
.001.1
.0870
.O7i
0.0
0.0
.012,
0.0
D.J70
0.070-
0.0
0.0
0.011
0.0
O.J70
q.oli
o.o
TotaT
VM
.00 IX
.00^8
.0030
.oasq
.870
.083
.010
.010
.083
.010
,«70
.083
.010
.0)0
.083
.0)0
.870
.0*3
.010
_/_/ Canopy t^tctA  only apply to ope.n ouuuu, without ie4.cdue and
y Example. c.alc.uZation:   fn.om vioi.kAhe.it. IV. 2,  &0% of, the. Aun.^a.c.e. in the. open ane.a hM  malah,  le.avj.ng 20% without mulch.
   T-i the. canopy u>  wUfioimly dit,tfbibute.d o\ieA 45% o& the. total oAea,  the.n only 20%  0)j the. canopy can coueA the. a/ie.a
   uiithout muZch.  Thejit&oie.:   (0.20} (0.45) {100}    9% o<( the.  aneA without mulch, that  -LA  coveAe.d by the. canopy.   ThiA
   X-UultA In a.  l/M   0.95.
_3/ EnteA on (aolkAhe.et IV.3.
4/ VU do>i loadA  iA ^01 a le.coveA.e.d condition.
                                                          vra.8i

-------
WORKSHEET  IV.6
         Weighting of VM values  for  roads  in
G-t-its  Creek.      watershed, hydrographic  area
                                13.
Erosion
response
un it
RI3.I
Ria-a.
ft is. a
M».4
*<3.s-

























Cut or fill
Fraction
of total VM
wi dth
il.lOfes) (0.810}
0.0778^ (fl.Olo }
0J&O (0.87o^
a.ldOO^ (0.0/oS
fo.iiotf^ ro.^^o^

























Roadbed
Fraction
of total VM
wi dth
+(o.7lo(Ho.o*3}
+(o.iMi$(o.o8$
+ ffl.fcUhf)(0.0«3^
•^(o.fe647^?o)o83^
+ (o.Jrai-fi (o.o«3l
^
























Fi 1 1
Fraction
of total VM
wi dth
* (o.im) (0.0 10)
+ (0.aW> (o.oi
-------
                                                                           WORKSHEET IV.7

                                               Factors  for  sediment delivery index from erosion response units  In

                                                         CtCfeX	 watershed, hydrographic area    i3	
Eros 1 on
response
unit
SCI3.I
S
lit
40
S
loo
Ife
loo
i&
Specific
site
factor
—
—
—
—
-
—
—
—
—
Percent
of total
area for
po 1 ygon
111
ia.7
U.I
—
5.1
30.9
(,./
2^.3
s-.t
^
O.OJL
o.ox
o.oa.
0.0^
o.oi
O.It
o.oi
o.ffc
O.OI
CO
                !/  Maxtmura J5 min.  annuat &toxm oŁ  2.5 -tn/fi*.
               ?/  In(5^tt(tt<.ow ^ui^e 0|5 2.0 -Ln/kn.  (fatued on
               I/  In^ittMLtion lati o$ 3.0 -In/hi  ibtu,e.d on &OJJL peMne.ab-iM.ti/].
               ?/  IniJiWwLtion /urte otf 0.1 ^n/fiA  (boied on i>o*Jl ph.e.et IV. 3.
               6/  When uiateA avaitab-i&ity -u zato,  then the. ie.dime.nt deJti.veJiy -lnde.x. -it,  z&to.

-------
                                WORKSHEET  IV.8
          Estimated tons of sediment  delivered  to a channel  for each
hydrographic area and type of disturbance  for   (art-its
                  a I rev-noil ue,  8
watershed,
Hydro-
graphic
area
/
a.
3
1
5
fo
7
8
9
10
II
la.
(3
H
ir
Me
17










Col umn
total
Di stur-
bance
total
^ercent
Cutting units
SC,








o.ol
o.o/
0.01
0.0
0.02.
0.0
0.0|
0.0|











O.O?
SC2








0.01

0.01

0.13
o.o
0.0
o.o











0.15
0.47.
3.3
CC]
o.ol
o.ol
o.ol
0-0)
o.oo.
0.01
o.ol
o.ol
0.01
o.ol
0.0|
o.o
O.Ol
0.0
o.ol
o.o
O.ol










o./J-
CC2
o.oi
o.ol
o.ol
o.ol


0.0|

0.01

O.Ol

o.o

0.0

o.o










0.07
CC3















o.o











0.0
0.2.0.
3.3
Roads
"1
o.a.
0.03
O.I
o.a
O.k>
0.°3
o.a
0.°3
0.03
0.03
0.03
o.ol
o.a.
O.I
0.1
O.I
O.I










3.0?
«2
O.I
0.01


O.OI
O.I
o.oi
O.ol
0.0|
O.ol
0.01
0.1
0.01
O.ol
o.ol
O.Ol
0.0|










o.va
«3
O.ol
O.I


O.ol
o.o|
0.1

O.I
0.4
0.03
o.l
o.a
O.I
O.I
0.1
—










l.llo
K4
O.I



o.oi
O.I


o.ol
o.o/
O.ol
o.l
0.05"

O.oS'
-
-










o.
-------
                                                          WORKSHEET  VI.1
                                Suspended sediment  quantification  for  Grits  Creek.
Time
(a)
ith hydro-
raphs use
ate; with
low dura-
ion curves
use % of
365 days
1
5
10
2.0
30
40
SO
t*o
10
80
?0
100








(\ )
i ncremen
(b)
Number
of
days
pre-
s i 1 vi-
cu 1 tura 1
act i vi ty
3.C,
(8.1
3C..5-
73.0
tol.s
I-&.0
isa.s-
aif.o
ass.0
a'fa.o
3.J8.0
36S.0








h
(c)
Number
of
days
post-
si I v i-
cu 1 tura 1
act i vi ty
3.fc
(8.1
36. S"
73.0
/0?.S"
;
-------
                                WORKSHEET VI.3

                     Sediment prediction worksheet summary

Subdrainage name Gr\ts Or€ek fflhWtflue  /Q      Date of analysis_
     Suspended Sediment Discharge

A.  Pre-siIvicuItural  activity total  potential  suspended sediment
    discharge (total  col.  (4), wksht. VI.1) (tons/yr)
B.  Post-si IvicuItural  activity total  potential  suspended sediment
    discharge (total  col.  (7), wksht.  VI.1) (due to streamflow           .
    increases) (tons/yr)                                               \l'(e
C.  Maximum allowable potential  suspended sediment discharge (total
    col. (9), wksht. VI.1) (tons/yr)

D.  Potential introduced sediment sources:  (delivered)

    1.  Surface erosion (tons/yr)                 3i.**

    2.  Soil  mass movement (coarse) (tons/yr)        0

    3.  Median particle size (mm)                   ""	
    4.  SoiI  mass movement—
          washload (silts and clays) (tons/yr)
    Bed Ioad Discharge (Due to increased streamflow)

E.  Pre-siIvicuItural activity potential  bedload discharge (tons/yr)
F.  Post-si IvicuItural activity potential bedload discharge (due
    to increased streamflow) (tons/yr)
    Total Sediment and Stream Channel  Changes

G.  Sum of post-si IvicuItural activity suspended sediment + bedload
    discharge (other than introduced sources) (tons/yr)               \7-\e
                                                                   (sum B + F)

H.  Sum of total  introduced sediment (D)
       = (D.I + D.2 + D.4) (tons/yr)

I.  Total increases in potential suspended sediment discharge

    1.  (B + D.1 + D.4) - (A) (tons/yr)

    2.  Comparison to selected suspended sediment limits
        (1.1 ) - (C) (tons/yr)                                     +
                                     Vffl.66

-------
                           WORKSHEET VI .3—continued
J.  Changes in sediment transport and/or channel change potential
    (from introduced sources and direct channel impacts)

    1.  Total  post-si IvicuItural activity soil mass movement
        sources (coarse size only) (tons/yr)                            0

    2.  Total  post-si IvicuItural soil  mass movement sources (fine
        or wash load only) (tons/yr)                                     Q
    3.  Particle size (median size of coarse portion) (mm)
    4.  Post-si I vicu Itural activity bedload transport (F) (tons/yr)     Q

    Potential  for change (check appropriate blank below)

        Stream deposition _

        Stream scour      _

        No change          y

K.  Total  pre-si I vicu Itural  activity potential  sediment discharge
    (bedload + suspended load) (tons/yr)
                                                                   (sum A + E)
L.  Total post-si I vicu Itural activity potential sediment discharge
    (all  sources + bedload and suspended load) (tons/yr)             S3.
                                                                   (sum G + H)
M.  Potential increase in total sediment discharge due to proposed
    activity (tons/yr)
                                                              (subtract L - K)
                                    V1II.67

-------
                                WORKSHEET VI .3

                     Sediment prediction worksheet summary

Subdrainage name &HJS  Creek    fkrhoW  B)       Date of analysis
     Suspended Sediment Discharge
A.  Pre-si I vicu Itural  activity total  potential  suspended sediment
    discharge (total  col.  (4), wksht. VI. 1) (tons/yr)                  \\-(a
B.  Post-si IvicuItural  activity total  potential  suspended sediment
    discharge (total  col
    increases) (tons/yr)
discharge (total  col.  (7),  wksht.  VI.1)  (due to streamflow         ~ ..
C.  Maximum allowable potential  suspended sediment discharge (total
    col. (9), wksht. VI.1)  (tons/yr)

D.  Potential introduced  sediment sources:   (delivered)

    1.  Surface erosion (tons/yr)                 P.7

    2.  Soil  mass movement  (coarse)  (tons/yr)        0	

    3.  Median particle size (mm)                   *""	
    4.  SoiI  mass movement—
          washload (silts and clays) (tons/yr)
    Bed load Discharge (Due to increased streamflow)

E.  Pre-siIvicuItural  activity potential  bedload discharge (tons/yr)    0

F.  Post-si IvicuIturaI  activity potential  bedload discharge (due
    to increased streamflow)  (tons/yr)                                  0
    Total  Sediment and Stream Channel  Changes

G.  Sum of post -si I vicu Itural  activity suspended sediment + bedload
    discharge (other than introduced sources) (tons/yr)               //•
                                                                   (sum B + F)
H.  Sum of total  introduced sediment (D)
       = (D.I  + D.2 + D.4) (tons/yr)                                  6. /

I.  Total  increases in potential  suspended sediment discharge

    1.  (B + D.1  + D.4) - (A) (tons/yr)                              /
-------
                           WORKSHEET VI .3~cont i nued
J.  Changes in sediment transport and/or channel change potential
    (from introduced sources and direct channel  impacts)

    1.  Total  post-si IvicuItural activity soil  mass movement
        sources (coarse size only) (tons/yr)                            0

    2.  Total  post-si IvicuItural soil  mass movement sources (fine        >.
        or wash load only) (tons/yr)                                     0
    3.  Particle size (median size of coarse portion) (mm)
    4.  Post-si I vicu Itural activity bedload transport (F) (tons/yr)     0 _

    Potential  for change (check appropriate blank below)

        Stream deposition _

        Stream scour      _

        No change           \r

K.  Total  pre-si I vicu Itural  activity potential  sediment discharge
    (bedload + suspended  load) (tons/yr)                               \\,(o
                                                                   (sum A + E)

L.  Total  post-si I vicu I tura I activity potential sediment discharge
    (all  sources  + bedload and suspended load)  (tons/yr)              «6.3
                                                                   (sum G + H)

N.  Potential  increase in total sediment discharge due to proposed
    activity (tons/yr)
                                                              (subtract L - K)
                                    VIH.69

-------
                                              WORKSHEET VI1.1

                           Variation of solar azimuth and  angle with time of day
Time of day
(Daylight savings time)
/a -'30
/ : 00 Solav noovi
1:30
_ . _ On«v\4e
-------
                                             WORKSHEET VI I.2




                              Evaluation of downstream temperature  impacts
Stream reach
appefc

MIDDLE

LOWER







Aad justed
«*•
?97

/g?

7S-Q







Had justed
*Tu/ft*-win
3.JSL

3,SX

3.S2,







Q
Surface
c4s
o.z

O.diS

O.Vs-







Subsurface
C^5


0.05

o.os







Ail/
°F
s.x

0.6

is







T2/
•F
68.1

65.3

6f?







      = Aadjusted * Hadjusted  x 0.000267   where Q  is surface flow only.



2/                  Q
—  T from mixing ratio equation.

-------
   PROCEDURAL EXAMPLE FOR HORSE CREEK—A SNOW DOMINATED
                                HYDROLOGIC REGION
DESCRIPTION OF AREA AND PROPOSED
        SILVICULTURAL ACTIVITY
  The  Timber Management Assistant  on  the
Glacier Ranger District, Rocky National  Forest3,
prepared a 5-year timber management plan for the
district. After cruising the Horse Creek drainage,
he determined that a sale of 600,000 board feet of
lodgepole pine was warranted based upon the stand
condition and timber market.


  The sale has been designed as a group of 24 small
clearcut blocks of approximately 12.5 acres each.
The blocks have been designated in the field with
orange marking paint. Engineering has flagged the
center lines of the roads that will need to be  con-
structed and has surveyed the actual location, col-
lecting sufficient data to design the roads to forest
standards. See figures IV. 17 and IV. 18 for the road
locations and layout of proposed clearcut  blocks.
  Resource specialists  have been asked to review
the proposed sale and to evaluate potential im-
pacts. Information from a general soil survey of the
area is available.
          Water Quality Objectives


  The  established water quality  objectives re-
quired  that suspended  sediment  discharge be
limited to 38.6 tons/yr and that water temperature
increases be no greater than 1.5°F  for the Horse
Creek drainage.
  3This is intended to be a fictitious forest; any similarity to an
actual forest is entirely coincidental.
                 DATA BASE


  Necessary  data have  been  obtained  from
resource specialists in timber, soils, hydrology, and
engineering.
  The collected data are presented in table VIII.4.
A complete water  resource evaluation  includes
analyses in the following categories (numbers for
the corresponding chapters in  this handbook ap-
pear in  parentheses):
  Hydrology (III)
  Surface Erosion (IV)
  Soil Mass Movement (V)
  Total Potential Sediment (VI)
  Temperature (VII)

          HYDROLOGY ANALYSIS

  Horse Creek is situated in hydrologic region 4, a
snow dominated region.  The procedure presented
in  "Chapter III:  Hydrology"  for  the  snow
dominated regions (including wkshts.  III.5,  III.6,
in.7, and in.8, proposed and revised worksheets
are  located at the end of section "Procedural Ex-
ample For Horse Creek—. . .") is applied to es-
timate  potential  volume  and  timing  of the
streamflow under the present conditions and under
the  conditions that would exist  if the proposed
silvicultural activity is implemented.  Necessary
data for conducting this evaluation is presented in
table Vin.4.

      Water Available For  Streamflow—
             Existing Conditions

  Step 1. — The first step in the hydrologic evalua-
tion of Horse  Creek is  to  estimate  the  water
available for streamflow  under  the existing condi-
tions. The following details the necessary steps out-
lined in worksheet m.5.  (Numbers in parentheses
refer to items or columns on the  worksheet.)
                                            VIII.72

-------
                                         Table  VI I 1.4.—A summary  of  information  required  for  the analysis  procedures.  Horse Creek  watershed
Description of the
information
required
Information
requirements
by chapter.!/
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology
Flow — hydrograph or flow
duration curve
Bankful
Basef low
Representative flows to be used to
establish suspended and bed load
rating curves
Width stream
Bankful
Basef low (average width flowing
water)
Depth stream (bankful)
Water surface slope
Suspended sediment for representative
flows
Bed load sediment for representative
flows
Channel stability rating
Orientation stream — azimuth
Low f 1 ow per i od ( date )
Percent streambed in bedrock
Bedrock adjustment factor
Length reach exposed
Travel time through reach
0






















































X,P

X

X

X
X
X
X
X








X,P



X





X
X
X
p
X
X

0.73 c-fe

-------
Table VII I .4-. —continued
Description of the
i n format I on
required
nformation
requirements
by chapter
1 1
IV
V
VI
VI 1
Information for watershed
Information on hydrology — continued
Normalized hydrographs
of potential excess water
Normalized flow duration curves
Date of peak snowmelt discharge
Map of drainage net
Presence of springs or seeps
Change stream geometry
Water surface slope
Bankful width
Bankful depth
P
P
0
X








X








X
X







X


X
X
X



X





Fiqu»e H.fcl a"d ^le HE. 13
N/fl
June 11th
Figuve tt.ll awd Agu.e. H./ST
/es

O.Oa.50 -ft/ft
a.s- ft
0.8&
Information on climate
Precipitation
Form
Annual average
Seasonal distribution
Storm Intensity and frequency
Extreme event
1 yr, 15-minute storm Intensity
Drop size
Precipitation — ET relationship
Wind direction

X
X
X




P
X

0

0
0

X
0



X


X


























Snow 3 maximum snowpaclc does mi exceed AO " water eiju.ii/a/eKt
3
-------
Table VI I I .1-.—continued
Description of the
information
required
Information
requirements
by chapter
I I I
IV
V
VI
VI I
Information for watershed
Information on climate — continued
Snow retention coefficient
Date snowmelt begins
Maximum snowmelt rate
Radiation
Solar ephemeris
Heat influx
Iso-erodent map for "R" factor
X,P
0
0










p


















p
p

Fi3u»e UL.to
N/fl
N/fl

Figute 3HL .3
Rau*c. 3Z3L.7
Rgure. JT.l
Information on vegetation
Species
Height
Over story
Understory
Riparian vegetation
Presence phreatophytes
Crown closure (?)
Cover density
Leaf area index (pre)
Basal area
Basal area — C^ relationship
Ground cover
X

X




p
X
0
p



X
X



X



X





X


















X

X
X
X

X





Uod^epJe ^>me.

10 K
N/fl
N/fl
N/fl
65%
33%
N/fl
3.00 ft yacre.
Figur*. ISL.'H
Worksheai: "Or. &

-------
                                                                                  Table VIII .4-.—continued
Description of the
i nf ormat i on
requ i red
nformat on
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on vegetation — continued
Percent transmission solar radiation
through canopy
Percent stream shaded by brush
Basel ine ET
ET modifier coefficient
Rooting depth
Rooting depth modifier coefficient

Depth soi 1
Percent sand (0.1-2.0 mm)
Percent silt and very fine sand
Percent clay
Percent organic matter
Soi 1 texture
Soi 1 structure
Permeabi 1 ity/lnf i Itration
Presence of hardpan
Nomograph for "K" factor
Baseline soi 1 -water relationships
Soil -water modifier coefficients
Jointing and bedding planes


X,P
P
X
P


















X,P
X




Figure IE. O.I ->8%
is7o
R9uY«s Jt.ae.; Winoy frufe «t a«al«s I«SS thai^ -fke MakiMj slope;
j«'mfe tmtty C(mc«iiH>niŁt% u)o»«y-. ° Q
I
O5

-------
Table VIII .4-.—continued
Description of the
information
required
Information
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on soils and geology — continued
Soi Is map
Previous mass movements
Number
Location
Unit weight dry soi 1
De 1 i very potent i a 1
Percent silt and clay delivered
Median size coarse material
0







X







X
X
X
X
X
p
X
X
















F,3u»-e. IS- -Ik
W*rU*t 3T.S
Fiftixre.3ZIIL.'S-
Fi3tt»e:2IIL.IS"
?0 Its/ft3
Rgu»«. IT."
34%
|0 Mm
Information on topography
Map (hydrologic region)
Latitude
Size watershed
Elevation
Aspect
Slope
Length
Gradient
Dissection
Shape/ 1 rregu 1 ar i ty
Nomograph for "LS" factor
X
X
X
X
X






X





X
X

X
p
X






X
X
X

X










X
X





X



USG-S map } figure H. 1 ; Hydrolo^c M^jioK V

-------
                                                                                  Table VIII .4-.— continued
Description of the
Information
required
Information
requirements
by chapter
III IV
V
VI
VI 1
Information for watershed
Information on topography — continued
Surface roughness

X



Moderak ^ SModfk
Information on the si 1 vlcu Itural activity
Past history
Harvesting
Fires
Other disturbances
Proposed harvest
Location units
Size cuts
Leaf area index removed
Cover density removed
Basal area removed
Cover density overstory remaining
Cover density understory remaining
Average minimum canopy height
Slash and duff~l itter
Cover percent
Height
Percent bare soi 1

X
X
X

X
X
X
X
X





X


0
0
0

X
X



X
X
X
0
X

X




















































N/fl
w/fl
W/fl

Rflu»«. 3E.I8, worksta«t nr.a,
Rqur«, J3T. 1? j 3OO acres -t- /I acres «f roads
N/fl
100 Ł
100%
tioAsslneek 3ST-1
Worksk^et JC.l,
O.S'w
W//I
Wor^€6-t ISC.il
3ft
Workskcet H.iL
oo

-------
Table VI I I .1-.--continued
Description of the
information
required
1 n format ion
requirements
by chapter
1 1 1
IV
V
VI
VI 1
Information for watershed
Information on si 1 vicultural activity — continued
Transportation system
Area disturbed
Locat i on
Cut slopes (location and slope)
Fill slopes (location and slope)
Cut and fill vs. ful 1 bench
Ins lope vs. outs lope
Surface
Width
Gradient
Surfacing (amount and kind)
Road density
Harvesting system
Landings
Location
Size
Gradient
Ground cover
Time for vegetative recovery of
disturbed surfaces

X
X











X
X




X
X
X
X
X
X

X
X
X

X

X
X
X
X
X





X





X
X













































Worksheet HL-SL j ll.Saeres
Figure 31.17
WoAst^tUI.a. • levgik W& j slope 66.7%
UJorU*€t 2T. a ; |««3-tk W & ; sfe^ 4>-7%
Ga±/fil|
Wo^staet J3T- 3. j oiofeleflxz.

/a.W
tUorkslwwi 3&. A j 0.0
Wov-lcsk^et JEE.2. ; bore
4.% = (J/.S acws iroads/Vtr aftr*s ^-^J
Twusk)V- skidam^

Figure 33C.I7
VOorU>cet IT-iL
Warkslieet IE. 1.
Worlcslice-t 3JT. It
1 year

-------
    (1) Watershed name. — Horse Creek can be
 evaluated as a single hydrologic unit. Division of
 the basin  into  hydrologic  subunits based  upon
 energy aspect or silvicultural zone is, therefore, un-
 necessary.
    (2) Hydrologic region. — Horse Creek is"within
 hydrologic  region  4.   Hydrologic  regions  are
 described in chapter HI.
    (3) Total watershed area. — There is one
 silvicultural prescription for the existing condition
 with an  area of 600 acres.
    (4) Dominant aspect. — The  most represen-
 tative aspect for Horse Creek is southwest.
    (5) Vegetation type. — Lodgepole pine is the
 most hydrologically significant vegetation  type.
    (6) Annual precipitation. — Annual precipita-
 tion averages 34.3 inches.
    (7) Windward length of open area. — There
 are no clearcuts on Horse Creek; the watershed is
 undisturbed.
    (8) Tree height. — Average tree height is 70
 feet.
    (9) Season. — There are three hydrologic sons
 in region 4: winter (October, November, December,
 January, February);  spring (March, April,  May,
 June);   and summer  and  fall (July, August,
 September).
   (10) Compartment.  — Since the area is un-
 disturbed, with no previous silvicultural activity,
 there are no impacted areas.
   (11) Silvicultural state. — Watershed areas are
 grouped into zones of similar hydrologic response
 as  identified  and  delineated  by silvicultural  or
 vegetational state.  For  Horse  Creek,  the  only
 silvicultural state is "forested."
   (12) Area, acres. — Horse Creek is undisturbed.
 There are no meadows  or roads within the basin;
 the watershed  is  completely  forested.  Therefore,
 unimpacted forested area equals the silvicultural
 prescription area, which is the total watershed area
 of 600 acres.
  (13) Area, %. — This refers to the percentage of
watershed area in each silvicultural state. In this
case, the unimpacted forested area is 100 percent
(1.00 as a decimal percent) of the total watershed
area.

  (14)  Precipitation.  — Precipitation  averaged
16.1, 12.1, and 6.1 inches for winter,  spring, and
summer and fall seasons, respectively.
  (15) Snow retention coefficient. — Since there
are no clearcuts or other open areas  within the
watershed, snow redistribution is not a factor.
  (16) Adjusted snow  retention coefficient. —
Since snow redistribution is not a factor, there is no
adjustment.
  (17) Adjusted  precipitation.  —  (No adjust-
ments to the precipitation  estimates  are neces-
sary.)
  (18) ET. — Baseline evapotranspiration (ET) is
obtained from figures III.24 to IE.26.  For Horse
Creek, baseline ET is  2.1,  7.6,  and 9.2 inches,
respectively,  for winter,  spring, and  summer and
fall.
  (19) Basal area. — The basal  area  for  the
forested zone is  200 ft2/ac.
  (20) Cover density, %. — For a basal area of 200
ft2/ac,  figure ni.41 gives a cover density of 33 per-
cent.
  (21) Cover  density, %Cdmax. — In the case of
Horse  Creek,  a  cover  density  of 33  percent was
judged sufficient  for  full hydrologic utilization.
Therefore,  it  is  considered  to beCdmax, so  the
percentage is 100.
  (22) ET  modifier coefficient. — The modifier
coefficient is  1 for all seasons since the cover den-
sity is atCdmax.
  (23) Adjusted  ET.  — (No  adjustments  are
necessary.) Values for Horse Creek are 2.1, 7.6, and
9.2  inches for winter, spring, and summer and fall,
respectively.
  (24), (25), (26), (27), (28), (29) Water available
for  streamflow. — The  following formula is used
to calculate water available for seasonal streamflow
by silvicultural state:
                Q = A  (P-ET)          (in.15)
where:
  Q   = water available for seasonal streamflow
         for a silvicultural activity
  A   = silvicultural activity  area as  a decimal
         percent of the total prescription area [col.
         (13)]
  P    = adjusted precipitation inches  [col. (17)]
  ET  = adjusted ET  inches [col. (23)]
  (30), (31), (32), (33), (34), (35) Water available
for  annual streamflow. — The sum of water
available for  streamflow by season represents  an-
nual streamflow. For Horse Creek, the unimpacted
forested zone generates 14.0 + 4.5 + (-3.1) = 15.4
inches of water available for annual streamflow.
(Negative values imply storage depletion.)
                                               VIII.80

-------
    Water Available For Streamflow—After
         Proposed Silvicultural Activity

   Step 2. — The second step in the hydrologic
 evaluation of Horse Creek is to estimate the water
 available  for  streamflow  if the  proposed
 silvicultural activity is implemented. The following
 details the  necessary steps outlined  in worksheet
 III.6.  (Numbers in parentheses refer to the items
 or columns in the worksheet.)
   (1), (2), (3), (4), (5), (6). — Same as worksheet
 III.5.
   (7) Windward length of open area. — All roads
 and clearcuts on Horse Cree.k are treated as single
 clearcuts with a windward length of 6 tree heights
 and a total area of 311.5 acres (11.5 acres in roads).
   (8), (9). — Same as worksheet HI.5.
   (10) Compartment. — For the proposed condi-
 tion of Horse Creek, there will  be two compart-
 ments: impacted and unimpacted. The impacted
 compartment includes  those areas  affected
 (directly or indirectly) by the proposed silvicultural
 activities, while the unimpacted  compartment in-
 cludes  areas  unaffected  by  the  proposed
 silvicultural activities.
   (11) Silvicultural state.  — For the proposed
 condition, Horse Creek will have one silvicultural
 state for  the unimpacted compartment (forested)
 and two for the impacted compartment (forested
 and clearcut). The set of silvicultural states com-
 prises the single  silvicultural prescription for the
 proposed condition.
   (12)  Area, acres.  — The 135 acres in the
 northeast corner  of the watershed will not be im-
 pacted by the proposed silvicultural activity. The
 remaining 465 acres  in the  watershed will  be
 directly  or  indirectly impacted by the proposed
 silvicultural  activity.  Trees  will  be completely
 removed from 311.5 acres, consisting of 300 acres
 clearcut and 11.5 acres  in roads. The  remaining
 153.5 impacted acres will not be harvested, but will
 be affected  by snow redistribution. For the pur-
 poses of calculation, clearcuts and roads are clas-
 sified  as clearcut  (impacted), while the un-
 harvested area affected by snow redistribution is
 classified as forested (impacted).
  (13) Area, %. — Column (12) is divided by item
 (3) giving decimal percent areas of 0.225, 0.256, and
0.519 for forested  (unimpacted),  forested  (im-
pacted),  and  clearcut  (impacted)  areas, respec-
tively.
  (14)  Precipitation.  — This  corresponds  to
column (14) of worksheet HI.5.
   (15) Snow retention coefficient. — From figure
 III.6 the snow retention coefficient for a clearcut 6H
 in windward length is 1.3. The snow retention coef-
 ficient  for the forest (unimpacted) remains 1.0,
 while that for the forested (impacted) area is not
 defined  by figure III.6.
   (16) Adjusted  snow  retention coefficient. —
 For the  forested (unimpacted) area, it is assumed
 that there is no net  change in  precipitation from
 snow redistribution.  The adjusted snow retention
 coefficient for  the clearcut area is determined by
 weighting the snow retention coefficient as follows:
         p  ,.=
         'oadj
                   0.50
                    X
(in.3)
 where:
     dj= adjusted  snow retention coefficient for
         the clearcut area
       = snow retention coefficient from  figure
         III.6 =  1.3

       y _ clearcut area (including roads)
               total impacted area


         This is the percent of impacted area to be
         clearcut.  Substituting values:
            X  =
                        311.5 ac
                  (311.5 ac  + 153.5 ac)
   Substituting values for Horse Creek:

                   I"	0.50
P<,aHj= 1 + (1-3-1)   311.57(311.5  + 153.t
                                =  1.22
  The adjusted snow retention coefficient for the
forested  area in the  impacted  compartment  is
calculated using the following formula:
         Pt =
               1- X
                                         (111.13)
where:

  Pf   =

  Poadi~
adjusted snow retention  coefficient  for
the impacted forested area
adjusted snow retention  coefficient  for
the clearcut =  1.22

_  clearcut area (including roads)
      total impacted  area
                                              VIII.81

-------
 This is the percent of impacted area to be clearcut.
 Substituting values:
          y  =         311.5 ac	
                (311.5 ac  + 153.5 ac)
   Substituting values for Horse Creek:
         1 - [(1.22) ((311.5)7(311.5 + 153.5)) ]
              1 - [311.57(311.5  +  153.5)]
Pf =
   = 0.55
   (17) Adjusted precipitation. — Multiplying the
 precipitation value in column (14) by the adjusted
 snow retention coefficient in column (16) gives ad-
 justed  precipitation. For  example, the  adjusted
 precipitation for the clearcut area of Horse Creek is
 16.1 X 1.22  =  19.6 inches.
   (18) ET. — Same instruction as worksheet III.5.
   (19) Basal area. — For forested areas, the basal
 area greater than 4 in dbh is 200 ft2/ac, while the
 clearcut basal  area greater than 4 inches dbh  is
 zero. These data are needed to estimate cover den-
 sity, if cover density is not supplied by the user.
   (20) Cover density. — For a basal area of 200
 ftVac,  figure in.41 gives a cover density of 33  per-
 cent. For a  basal area of zero, the cover density is
 zero.
   (21) Cover density,%Cdmax. — A cover density of
 33 percent  has  been judged sufficient for  full
 hydrologic utilization and has been assigned the
 value of Cdmax. Division of cover density percent in
 column (17) by Cdmax gives %Cdmaxwhen multiplied
 by 100.
   (22) ET modifier coefficient. — The %Cdmaxcan
 be entered  into figure  III. 46 to  obtain  the  ET
 modifier coefficient.  For a %Cdmax of 100, figure
 IE.46 gives  ET  modifier coefficients of 1.0 for all
 seasons. For a  %Cdmax  of zero, the ET mdifier
 coefficients from figure 111.46 are 0.60, 107,  and 0.55
 for winter, spring, and  summer and fall, respec-
 tively.
   (23) Adjusted ET. — Multiplying ET in column
 (18) by the ET modifier coefficient in column  (22)
yields the adjusted ET.
   (24), (25), (26), (27), (28), (29) Water available
for streamflow. — Multiplication of the treatment
area (as a decimal  percentage of the  watershed
area, item 13)  times the difference between  ad-
justed  precipitation and  adjusted evapotranspira-
tion (item 17-  item  23) is an  estimate  of  area
weighted contribution to  total watershed flow that
will be derived from the  treatment (or state)  area
by season and is entered in one of the columns from
24-29.
                                                     For example, for the clearcut in winter:
                                                          Q  = 0.519(19.6-1.3)  = 9.5 inches
  (30), (31), (32), (33), (34), (35) Water available
for annual streamflow.  —  The  summation  of
seasonal streamflows is an estimate of the water
available  for  annual streamflow.  Horse  Creek
values are 3.5, 1.1, and 13.5 inches for the (unim-
pacted) forested, (impacted) forested, and clearcut
areas, respectively.
                                                 Streamflow Discharge And Timing — Existing
                                                                    Conditions

                                                   Step 3. — The third step  in  the hydrologic
                                                 evaluation of Horse Creek is to estimate the dis-
                                                 charge and timing of the existing condition. The
                                                 following details the necessary steps outlined  in
                                                 worksheet El.7. (Numbers in parentheses refer to
                                                 the items or columns in the worksheet.)
                                                   (1), (2). — Same as worksheet III.5 and III.6.
                                                   (3) Date  or  interval. — Based on  previous
                                                 knowledge of the area, peak discharge for Horse
                                                 Creek occurs June 19. Six-day  intervals centered
                                                 around this date are listed in column (3).
                                                   (4) Forested  (unimpacted),%.  — Values from
                                                 the forested column of table III. 13 are entered into
                                                 column (4) with a peak discharge of 0.1575 percent
                                                 occurring on June 19.
                                                   (5) Forested (unimpacted), inches. — Forested,
                                                 (unimpacted), percent [col.  (4)] is multiplied by
                                                 potential  streamflow for the  existing condition
                                                 from the  forested (unimpacted) zone [item (30),
                                                 wksht III.5] which is  15.4 inches.
                                                   (6) Forested (unimpacted),  cfs. — Each value
                                                 in column (5) forested (unimpacted) in inches, is
                                                 multiplied by the following factor:
                                                   	total watershed area (ac)	
                                                   (12 in/ft) (1.98) (number of days in interval)
                                                 For example, on May 26, 0.92 inches is converted to
                                                 cfs as follows:

                                                         cfs  =  (600) (Q-92>     = 3.87 cfs
                                                               (12) (1.98) (6)

                                                   (7) - (21). — Not applicable to the existing con-
                                                 dition of Horse Creek.
                                              VIE .82

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  (22)  Composite hydrograph. —  The sum of
columns (6), (9), (12), (15), (18), and (21) gives the
composite hydrograph in digital form. A plot of
column (3) versus column (22) yields the existing
condition hydrograph (fig. VIII.13).
Streamflow  Discharge And Timing  — After
                   Proposed
             Silvicultural Activity

  Step  4.  — The final step in  the  hydrologic
evaluation  of Horse Creek  is to estimate the dis-
charge and timing of the streamflow if the proposed
silvicultural activity is implemented. The following
details the necessary steps outlined in worksheet
in.8. (Numbers in parentheses refer to the items or
columns on the worksheet.)
   (1), (2). — Same as worksheet  HI.5,  IH.6, and
m.7.
   (3)  Date  or interval.  — The date of peak
snowmelt discharge for Horse Creek is June 19, the
peak discharge date for the forested (unimpacted)
zone. Six-day intervals are  labeled accordingly.
   (4) Forested (unimpacted),  %. —  Same in-
structions as worksheet DI.7.
   (5) Forested (unimpacted), inches. — Column
(4) is multiplied by potential streamflow for the
proposed condition from the forested (unimpacted)
zone [item (25), wksht. IE.6]. For Horse Creek this
value is 3.5 inches.
   (6) Forested (unimpacted), cfs. — Each value
in column (5), is multiplied by the following factor:
  	total watershed area (ac)	
  112 in/ft) (1.98) (number  of days in interval)
           total watershed area (ac)
   (12 in/ft) (1.98) (number of days in interval)
         600
                  = 4.209
    (12) (1.98) (6)

   (7), (8), (9).  — Not applicable for the Horse
Creek example.
  (10) Forested (impacted),%. — These values are
taken from the forested column in table III. 13.
  (11)  Forested (impacted), inches. — Column
(10)  is multiplied by potential streamflow for the
proposed condition from the forested (impacted)
zone [item  (32), wksht. 131.6]. For Horse Creek this
value is 1.1 inches.

  (12) Forested  (impacted), cfs. — Conversion of
inches to cfs involves multiplication of each value
in column  (11) by:
          600
                   = 4.209
     (12) (1.98) (6)
  (13) Clearcut (impacted),%. — Percent poten-
tial streamflow distribution for open areas is taken
from the open column of table III. 15. Note that
peak discharge from clearcut areas occurs before
peak discharge from forested areas.
  (14)  Clearcut (impacted), niches. — Column
(13) is multiplied by potential streamflow for the
proposed condition from the open  (impacted) zone
[item (33), wksht. HI.6] . For Horse Creek this value
is 13.5 inches.
  (15) Clearcut (impacted), cfs. — Convert inches
to cfs by multiplying values in column (14) by the
factor:
  _ total watershed area (ac) _
   (12 in/ft) (1.98) (number of days in interval)
                   = 4 209
     (12) (1.98) (6)

  (16) - (21). — Not applicable for the Horse Creek
example.
  (22) Composite hydrograph. —  The sum of
columns (6), (9), (12), (15), (18), and (21) for each
interval gives the composite hydrograph for the en-
tire Horse Creek watershed (in cfs) (fig. VIII. 13).
      SURFACE EROSION ANALYSIS


  The  quantity  of surface  eroded  material
delivered to stream channels from sites disturbed
by the proposed silvicultural activities is estimated
in two stages. First,  the quantity of material that
may be made available from a disturbed site is es-
timated using the Modified Soil  Loss Equation
(MSLE).  Second,  a  sediment  delivery  index
( SDj ) is estimated. When this is applied to the
estimated quantity  of  available  surface eroded
material, an estimate of the quantity of material
that may enter a stream channel is obtained.


      Erosion Response Unit Delineation
  Steps 1-7. — A method for preparing the maps
(or overlays) for these steps is discussed in chapter
IV. Figures IV. 14  to IV.19 show the results of these
steps for the drainage net, hydrographic areas, soil
                                             VIII .83

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12



11



10



 9



 8



 7



 6



 5



 4



 3



 2



 1



 0 •
                                                                       Existing Condition Flow
                 Proposed Condition Flow
LU
O
ir
<
I
o
CO
Q
        MARCH
                           APRIL
MAY          JUNE


     MONTH
                                                                     JULY
                                                                                      AUGUST
       Figure VIII.13.-Pre- and post-sllviculiural activities annual hydrograph, Horse Creek watershed.
                                        VIII. 84

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 groups,  location  of cutting  units,  roads,  and
 landings.
   Step 8. —  Set up  worksheets  for estimating
 potential sediment load from surface erosion.
   Worksheets IV.1 and IV.2 show field data for ero-
 sion response units by hydrographic area and type
 of disturbance. Individual soils in the Horse Creek
 watershed have been grouped according to similar
 texture, organic  matter, structure, and  perme-
 ability characteristics.  Worksheet IV.l shows the
 three soil groups  used for surface erosion evalua-
 tion. Data on  worksheet IV.l should  not change
 when  different  management  proposals  are
 evaluated for the  watershed.
   Worksheet IV.2 displays  various  types of data
 needed for evaluating the effects of the proposed
 management  of  Horse   Creek watershed,
 hydrographic area 3 (fig. IV. 15). Individual erosion
 response units are identified and listed. A different
 erosion response unit is created for each change in
 management activity,  each design change for a
 given activity (e.g., road change from a cut-and-fill
 design to a complete fill for a stream crossing), or
 each change  in environmental parameters affecting
 erosion (e.g., a change in soil characteristics).
   Worksheet IV.3 is a summary of the  values used
 in the MSLE  and  sediment  index  for  erosion
 response units in hydrographic area  3 of the Horse
 Creek watershed. The values for both management
 proposals are obtained using the steps  and discus-
 sions which  follow.  Only values for the proposed
 plan are used to illustrate methods for solving the
 equations; however, values for the revised plan are
 similarly determined
   Step 9.  — List each erosion source  area  and
 number by erosion response unit.
   For  the Horse  Creek watershed, the response
 units have been coded  as follows. The treatment
 types are clear cuts (CC), landings (L), and roads
 (R). The example hydrographic area is number 3.
 Disturbance types are numbered sequentially (e.g.,
 clearcut CC3.1, clearcut CC3.2, etc),  to identify
 them in the following evaluations for soil loss and
 sediment delivery.
Using The Modified Soil Loss Equation (MSLE)

  Step 10. — For each erosion response unit and
source area  (silvicultural  activities  and roads),
determine the values to be used for each of the fol-
lowing variables:
        R   Rainfall factor
        K   Soil credibility factor
      LS   Length-slope factor
      VM   Vegetation-management factor
     Area   Surface area of response unit
  Values for these factors are entered on worksheet
IV.3 using the following procedures.
Rainfall Factor


  This value is obtained from figure IV.2. For the
Horse Creek area, R = 45. This R value is the same
over the entire Horse Creek area and will  be used
for all erosion response  units.
 Soil Erodibility Factor


  The K  value  can be  estimated  using the
nomograph in  figure IV.3, or by  using  equation
IV.4. The data  for soil group 2 needed to compute
the K value using  equation  IV.4 are found on
worksheet  IV.l. K must be determined  for both
topsoil and subsoil. For disturbances which enter
the subsoil, such  as roads, the subsoil  value of K
must be  used.
  Application of the equation  to determine the K
factor is  shown in the following example for soil
group 2 topsoil. This  example is also plotted on the
nomograph (fig. IV.3) for the subsoil. Because of in-
flections  in the  family of curves on the nomograph
(fig. IV.3) for percent sand, the equation cannot be
used when silt  plus very fine sand exceed 70 per-
cent.
K = (2.1 X  10-6) (12-Om) M1-14
      + 0.0325  (S-2) +  0.025 (P-3)        (IV.4)
where:
  Om =  % organic  matter
  M  =  (% silt + % very fine sand) (100-% clay)
  S   =  structure code
  P   =  permeability code
  Substituting values for topsoil (soil group 2) from
worksheet IV.l  into equation IV.4:
  K  =  (2.1 X 10-6) (12-4) [40 (100-10)]1-14
         + 0.0325 (4-2) + 0.025 (4-3)
  K  =  0.28
  The K value  of the subsoil (0.30) may  be deter-
mined from either the nomograph or equation.
                                              VIII.85

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Length-Slope Factor

  The length-slope factor, LS,  is a combination
factor which incorporates the slope gradient and
the length of the eroding surface into a single fac-
tor. The LS factor must be estimated for each ero-
sion response unit.
  Two methods may be used to estimate the LS
factor on straight slopes.  One  method is  to  use
equation IV.8 to derive  the  estimated  LS value.
The second method utilizes a nomograph (fig. IV.4)
to estimate the LS value.
  The cutting units (CC3.1 and CC3.2) are each
different in regard to  slope gradient and length.
Therefore, LS for each  clearcut  unit must  be
evaluated separately. Using equation IV.8 and data
from worksheet IV.2,  the  LS value for CC3.1 is
calculated as follows for slope length A =  100 feet
and slope gradient s = 38  percent.
     LS =
           72.6
             10,000
            10,000+s2
                   0.43 + 0.30s + 0.043s2 \
                 6.613
                               (IV.8)
where:
  X    = slope length, in feet
  s    = slope gradient, in percent
  m   = an exponent based on slope gradient from
         equation IV.6
Using data from worksheet IV.2:
    LS =
100_V5/0.43 + 0.30(38) + 0.043(38)2
72.6,
                           6.613
              10,000
           10,000+(38)2
   LS  =  11.5
 A  similar calculation  is performed for  clearcut
 CC3.2 and landing L3.1. All values are tabulated in
 worksheet IV.3.
   Road R3.1 is outsloped with a typical cross sec-
 tion shown in figure IV.7. Road R3.2 is assumed to
 be fill, over  culverts. Average dimensions will be
 the same as for R3.1 with the cutbank changed to a
 fill slope.
   To compute the length-slope value for  the road
 sections (R3.1, R3.2,)  the equation for  irregular
 slopes is  used in this example. An alternative
 method using graphs (figs. IV.5 and IV.6) is discus-
 sed in chapter IV.
                                                                        Q  \m + l
                                                                        bJAJ-l
                                                                         72.6'
                                                                                   (IV.9)

                                         The number of calculations  can be reduced by
                                         simplifying equation IV.9 to:
                                                                    m + l  _ \m + l
                                            LS = I_  .
                                                      10,000
                                                    10,000 + s2
                                                                      72.6
                                        (IV.9.1)
                                         where:
                                           Xe
         entire length of a slope, in feet
  Xj  =  length  of slope to  lower edge  of j
         segment, in  feet
  j    =  slope segment
  Sj   =  slope gradient, in percent
  Sj  =  dimensionless slope steepness factor for
         segment j defined by:

          (0.043s2 + 0.30Sj + 0.43)76.613

  m  =  an exponent based on slope gradient
  n   =  total number of slope segments
  For the road R3.1, using values in worksheet IV.2
and assuming that no sediment is deposited on the
road surface, the computations are as follows:


Slope segment 1 (cut)
  Xi  =  4.8 ft
  ^1-1 =  0.0 ft (there are no preceding slope seg-
         ments, hence length is 0.0 ft)
  s   =  66.7%
  m  =  0.6 (for slopes  on construction; see eq.
         IV.6)
               0.043s2 + 0.30s  + 0.43
                                                   S,  =
                                         substituting for s:
                                                                 6.613
                                           c    0.043(66.7)2 +  0.30(66.7)  + 0.43      Q0
                                           oi  — 	 =  6i
                                                            6.613

                                          Substituting values of S, X,  and m for j = l into
                                          equation IV.9.1 to the right of the summation sign
                                          gives:
                                              Vin.86

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                                   10,000
                             10,000 + (66.7)2
   =  20.83
   Slope segment 2 (roadbed)
   *2  =  4.8 + 12.0 = 16.8 ft
   X2-i =  slope length  = 4.8 ft
   s   =  0.5%
   m  =  0.6 (for slopes on construction sites)
         S2 =
             0.043s2 + 0.30s + 0.43

                      6.613
 substituting for s:

       0.043(0.5)2 +  0.30(0.5) +  0.43
S-, =
                    6.613
                                          = 0.09
 Substituting S, X, and m values for j=2 into equa-
 tion IV.9.1 to the right side of the summation sign
 gives:
                                                Solving  the  entire  equation IV.9.1, using  the
                                                calculated values
                                                where:
                                                Xe = 4.8 + 12.0 + 4.8 =21.6 ft

                                                then:     -,
                                                  LS  = ~~r~ (slope seg.  1 + slope seg. 2

                                                              pe seg. 3)

                                                               (20.83  + 0.54 + 76.53)
                                                             + slope  seg. 3)
                                                               1
                                                         21.6

                                                       = 4.53
                                                  A similar LS calculation is made for road R3.2.
                                                Road R3.2 is a fill,  over culverts across a stream
                                                channel, however, and it becomes two problems,
                                                each with two slope segments. Each segment starts
                                                at the middle of the road surface,  and the second
                                                segment includes one of the fill slopes. An average
                                                value (4.3)  for the  LS factor using the two LS
                                                values just determined by splitting the road in half
                                                is entered on worksheet IV.3.
  0.09
   = 0.54
       (16.8) L6- (4.8)
                       1.6
              (72.6)
                   0.6
                            10,000
                         10,000 + 0.52
   Slope segment 3 (fill)
   *3  = 4.8 + 12.0 + 4.8  = 21.6 ft
   X3.i  = slope length = 16.8 ft
   s    = 66.7%
   m   = 0.6 (for slopes on construction sites)

                0.043s2 +  0.30s + 0.43
          S, =
substituting for s:
                        6.613
       0.043(66.7)2  + 0.30(66.7) + 0.43
  S:i  = 	 =  32
                    6.613

Substituting S, X, and m values for j=3 into equa-
tion IV.9.1 to the right side of the summation sign
gives:
  32
A21.6)1-6 -  (16.8)L
         ,0.6
                                 10,000
          (72.6)
                       10,000  + (66.7)2
   = 76.53
                                                    Vegetation-Management Factor

                                                      The vegetation-management factor (VM) is used
                                                    to evaluate effects of cover and land management
                                                    practices on surface erosion over the entire slope
                                                    length  used for the LS factor. Values for VM  are
                                                    determined for  all cutting  units, roads,  and
                                                    landings.
                                                      (1) Cutting units. — Worksheet IV.2 has  the
                                                    field data  used for  calculating a VM factor  for
                                                    clearcut units CC3.1 and CCS.2. Example calcula-
                                                    tions are shown for clearcut  CC3.1. The  cutting
                                                    unit is  divided into two areas based on presence or
                                                    absence of logging residues. A ground cover of slash
                                                    and other surface residues covers 65 percent of the
                                                    unit (wksht. IV.2). The remaining  35 percent is
                                                    scattered in open areas of soil averaging 10 feet in
                                                    diameter.4  In both areas, fine tree  roots  are  un-
                                                    iformly distributed over 90 percent of the clearcut
                                                    block. All of the overstory and understory canopy
                                                    has been removed.
                                                      Using worksheet IV.4, first enter percent area as
                                                    0.65 and 0.35 for area covered by residues and open
                                                     ^Information about the amount of residue is often expressed in
                                                    tons per acre. Maxwell and Ward (1976) have published photos
                                                    and tables for parts of Oregon and Washington which relate
                                                    visual appearance of a site with the  volume of residue and
                                                    amount of ground cover.
                                               vm.87

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area, respectively. Separate calculations are made
for the logging residue and open areas.
  Second, the logging slash represents the mulch
and close growing vegetation. Because slash varies
in density, assume that small openings a few inches
in diameter exist over 10 percent of the  surface.
From figure IV.9, the 90-percent cover provides a
mulch factor of 0.08. The 35 percent of CC3.1 that
is open is assumed to have 10 percent of the surface
protected by widely scattered slash.  Using figure
IV.9, a mulch factor of 0.78 is found for this situa-
tion.
  Third, zero canopy cover gives a canopy factor of
1.0 for both areas (fig. IV.8).
  Fourth,  evaluate the role of fine roots that are
remaining in the soil. Since they are uniformly dis-
tributed over 90 percent of the entire clearcut area,
the value, 0.10, from figure IV. 10 can be used  for
both logging residue and bare areas.
  Fifth, determine if the open areas are connected
with  each  other, such  that  water can  flow
downslope from one to another (ch. IV). In this ex-
ample, the open areas are  isolated from each other
by bands of logging residue, requiring the use of a
sediment filter strip factor of 0.5 (see "Sediment
Filter Strips"  section of chapter IV).  If sediment
filter strips did not exist,  a factor of 1.0 would be
used.
  Sixth, using worksheet  IV.4,  multiply the VM
subfactors for logging residue  (0.65)   (0.08) (1.0)
(0.10) = 0.005. Likewise,  the subfactors for bare
area are: (0.35) (0.78) (1.0) (0.1) (0.5) = 0.014. The
overall VM factor is the sum of the VM subfactors:
(0.005)  + (0.014) = 0.019.
  Clearcut  CC3.2  will have 60-percent  logging
residue  cover and 40-percent bare, with bare areas
averaging 10 feet in diameter. Fine roots will be un-
iformly  distributed over 85 percent of both areas.
There will not be any canopy. Bare areas will have
filter strips between them. The assumptions about
residue  density are the same as for CC3.1. Values
are shown on worksheet IV.4.
   (2) Landings. — Landing L3.1 is  assumed to
 represent  a  surface  described in table IV.3  as
 "freshly disked after one rain," with a VM factor of
 0.89.
   (3) Roads. — The VM factor must represent two
 conditions on the road areas: (1) the road running
 surface, and  (2) the cut-and-fill banks that  are
 needed (fig. IV.7).
  The following assumptions have been made for
road erosion response units R3.1 and R3.2.
  a. All cut-and-fill slopes will be seeded and fer-
     tilized within 10 days after completion of the
     road section.
  b. Vegetation will be fully established within 1
     year.
  During the first year, the  VM factor will  be
changing constantly from bare soil to a vegetated
surface on the cut-and-fill slopes. To account for
this change, VM is estimated monthly; total those
months  with  erosive rainfall or  runoff, and  then
divide by the total number of erosion months to ob-
tain an  average VM value for those time periods
with potential for erosive rainfall and/or snowmelt
runoff (wksht. IV .5). Use the method described for
clearcuts to estimate VM for the site by month.
The VM factor will be effected  initially by the
ground cover (fig. IV.9). As the vegetation matures,
canopy and fine  roots will also influence the VM
factor.
  Summing the  VM values from worksheet  IV.5
and dividing by 8 months (3.36/8 =  0.42) gives a
VM value of 0.42 to use for the first year following
construction with cut-and-fill slopes.
  The VM  for the  roadbed  (1.24) for R3.1 is ob-
tained from table IV.3 for compacted fill without
surfacing.
  Total width for
    exposed surface = 2.9 ft + 12 ft + 2.9 ft

                  = 17.8 ft

  Running  surface = 12'° ft = 0.6742
                     17.8 ft
                   = fraction of total width
   Each cut or fill  =  2.9ft
     slope            17.8 ft
=  0.1629
                   =  fraction of total width
  The weighted VM factor for Rl.l and  R1.2 is
calculated from data on worksheet IV.2 and shown
on worksheet IV .6.

Surface Area Of Response Unit

  Total surface  area  within  each treatment
unit—clearcuts, landings,  and roads—is given in
worksheet IV.2 and is entered  onto worksheet IV.3.
All other MSLE factors  are also entered onto
worksheet IV.3.  Total potential onsite soil loss is
computed by multiplying all factors on worksheet
IV.3.
                                               VIII.88

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              Sediment Delivery

  Step 12. — The computed potential surface soil
loss is delivered to the closest stream channel using
the sediment  delivery index  (SDj ).  Worksheet
IV.7 is used to organize the data for each erosion
response  unit, for each factor shown  on the stiff
diagram  (fig. IV.22).
  1. Water  availability for sediment delivery  is
     calculated using equation IV. 12 for each ero-
     sion response unit.
                     F =  CRL          (IV. 12)
where:
  F   =  available water (ftVsec)
  R  =  [1  yr, 15 min storm  (in/hr)] - [soil in-
         filtration rate (in/hr)]
  L   =  [slope length distance of disturbance (ft)]
         +  [slope  length  from disturbance to
         stream (ft)]
                     f f 2 Li
  C  =  2.31  X 10-5  :	—
                     in sec
   The infiltration rate, used in determining the R
 factor, is the maximum rate at which water could
 enter a soil. In actual situations, the water entry
 rate will usually be somewhat lower than  the in-
 filtration rate and can  be  based on the soil
 permeability,  with  consideration  for  effects  of
 various management practices.
   Using  data from  worksheet IV.2 and  footnotes
 from worksheet IV.7, the calculations are:
F   =  (2.31  X 10-5
                      ft2 hr
                               (1.75  in/hr
                      in sec
         -  0.26 in/hr) (100 ft + 15 ft)
      =  (2.31 X 10-5) (1.49) (115)
      =  0.004 ftVsec
  2. Texture  of eroded  material is  based on the
    amount of very fine sand, silt, and clay shown
    on worksheet IV. 1.  For this case, it has been
    assumed that half of the clay will form stable
    aggregates with the remainder influencing the
    sediment delivery index. For soil group 2 top-
    soil, the  following calculations were made:
      texture of
                           clay
                           2
                        + % very fine sand
                        10
eroded material  =
                            - + % silt
                         2
                        45
                          -+ (15)  + (25)
                                                 3. Ground cover is the percentage of the soil sur-
                                                   face with vegetative residues and stems  in
                                                   direct contact with the soil. The ground cover
                                                   on  the  area between a disturbance  and a
                                                   stream  channel  is  determined  from field
                                                   observations  and  used  for  the sediment
                                                   delivery index. For CC3.1, 90 percent is shown
                                                   on worksheet IV.2 for ground  cover.
                                                 4. Slope shape is a  subjective evaluation  of
                                                   shapes between convex  and concave.  From
                                                   worksheet IV.2 for  CC3.1 the slope  shape is
                                                   straight.
                                                 5. Distance is the slope length from the edge of a
                                                   disturbance to  a stream channel. For  CC3.1
                                                   (wksht.  IV.2), the  distance is  15 feet.
                                                 6. Surface roughness is a subjective evaluation
                                                   of soil  surface microrelief  ranging  from
                                                   smooth to moderately rough. Worksheet IV.2
                                                   shows  a moderate surface roughness for
                                                   CC3.1.
                                                 7. Slope gradient  is the percent  slope  between
                                                   the lower boundary of the disturbed area and
                                                   the stream channel. Worksheet IV.2 shows a
                                                   gradient of 38 percent for the disturbed area.
                                                 8. Site specific is an optional factor that was not
                                                   used in this example. See chapter IV for more
                                                   discussion of this factor.
                                                 The tabulated factors for CC3.1 (wksht. IV.7) are
                                              plotted on  the  appropriate  vectors  of a stiff
                                              diagram (fig. VIII.14) as discussed  in chapter IV.
                                              Use one of the several methods to  determine the
                                              area bounded by the irregular  polygon that  is
                                              created when points on the stiff diagram are joined.
                                              The area of the  polygon for this example is  94.94
                                              square  units.  The stiff  diagram has  784 square
                                              units. The percentage of the total area enclosed by
                                              the polygon is:
                                                                f94-94") (100) = 12.1%
                                                                V 784  / \  /
                                                 Entering the  X-axis  of the probit  curve (fig.
                                              IV.23)  with 12.1 results  in a sediment delivery in-
                                              dex (SD j ) or 0.02. This is the estimated fraction of
                                              eroded material  that could be delivered from the
                                              disturbance to the stream channel.
                                                Step 13. — Find the estimated quantity of sedi-
                                              ment (tons/yr) delivered to  a stream channel by
                                              multiplying  surface  soil  loss  by the  sediment
                                              delivery  index  (wksht.  IV.3)  for  each  erosion
                                              response unit.
                                              VHI.89

-------
         Percent Ground
             Cover
   Texture of
Eroded Material
                                                  100-
Available
 Water
Slope
Shape
                                                                                          0.10
                                              100   Site
                                                  Specific
        Delivery Distance
              feet
   Surface
  Roughness
   Slope
  Gradient
                 Figure VIII.14.—Stiff diagram for CC3.1 proposed plan, Horse Creek watershed.
                                             vni.9o

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  Step 14. — Using worksheet IV.8, tabulate quan-
tities  of  delivered  sediment  (tons/yr)  for  each
hydrographic  area by the erosion source.  When
completed, this table provides a summary of sur-
face erosion sources and estimated quantities of
sediment production from each hydrographic area.
  Step 15. — Totals and percentages are shown on
worksheet  IV.8. The total quantity  of  delivered
material is shown in table VIE. 5.
    SOIL MASS MOVEMENT ANALYSIS


  A step-by-step  description,  using  the Horse
 Creek  data,  was presented in "Chapter V: Soil
 Mass Movement." The following discussion sum-
 marizes the results of that detailed description.
  Evaluation of the existing soil mass movement
 hazard (fig. VIII.15) in the Horse Creek drainage is
 based  upon seven  natural site factors using table
 V.5 and worksheet V.I. Based upon the informa-
 tion collected and presented in the beginning of the
 example, the natural soil mass movement hazard
 index is medium, with a factor summation of 31.
 The value 31 falls within the medium hazard range
 (21-44).
  The  proposed silvicultural activity will result in
 an  increased   soil   mass  movement  hazard.
 Worksheet V.2 is  completed  based   upon  the
 proposed silvicultural activity. The information re-
 quired to complete this worksheet is presented in
 table Vin.4. The three silvicultural activity factors
 total 31. Adding the existing natural hazard value
 of 31 to the silvicultural activity hazard value of 31
 gives the total  value for  the post-silvicultural ac-
 tivity:  62. This value falls within the high hazard
 range (greater than 44).

  There is evidence of one soil mass movement in
 Horse Creek watershed approximately 20 years ago
 on a smooth 67 percent (34°) slope. The dimensions
 of the failure are 84 feet long, 28 feet wide, and 1.5
 feet deep. The bulk density was found  to be  90
 lbs/ft3  (1.43g/cm3).
  To evaluate the potential impact of the proposed
 silvicultural activity on soil mass movement, Horse
 Creek must be compared to an adjacent watershed,
Mule Creek. Mule Creek, which had a silvicultural
activity similar to that proposed for Horse Creek,
was investigated to ascertain  the actual impacts
that followed a silvicultural activity. Mule Creek
watershed  is considerably  larger  than  Horse
Creek—3,900 acres vs. 600 acres  (1,620 ha vs. 243
 ha)—however,  both watersheds have similar site
 characteristics—soils,   geology,   precipitation,
 vegetation, etc. Prior to the silvicultural activity in
 Mule Creek, there had been only one soil  mass
 movement (debris avalanche-debris flow), approx-
 imately 25 years ago, on a smooth 84 percent (40°)
 slope-length 115 feet, width 19 feet, depth 1.5 feet
 and bulk density 99 lbs/ft3. During the 4 years since
 the silvicultural  activity, five debris  avalanche-
 debris flows have occurred:
  1.  Smooth 73  percent (36°)  slope—length 80
     feet, width 24 feet, and depth 1.5 feet.
  2.  Smooth 73 percent  (36°) slope—length 129
     feet, width 26 feet, and depth 1.5 feet.
  3.  Smooth 55 percent  (29°) slope—length 121
     feet, width 17 feet, and depth 1.5 feet.
  4.  Smooth 55 percent  (29°) slope—length 113
     feet, width 18 feet, and depth 1.5 feet.
  5.  Smooth 40  percent  (22°)  slope—length  95
     feet, width 23 feet, and depth 1.5 feet.
  Using the procedure outlined in chapter V and
figure V.8, worksheets V.I, V.2, V.5, and V.6 were
completed. Based upon these computations, it was
determined that 192 tons of soil mass movement
material  could  potentially be delivered to Horse
Creek due to the  proposed  silvicultural activity.
This total is shown on table VIII.5.
      TOTAL POTENTIAL SEDIMENT
                  ANALYSIS

  Step 1. — The stream reach characterization will
be obtained on the lower 1/4 mile of the third-order
stream channel on Horse Creek.
  Step  2.  — See figure  VIII.13 pre- and  post-
silvicultural activity hydrographs.
       Suspended Sediment Calculation

  Step 3. — Establish suspended sediment rating
curve.
  a. Data  were obtained from  depth integrated
     suspended sediment sampling and concurrent
     stream discharge measurements taken over a
     period of 1 year. Samples were taken during
     representative flows and are plotted in figure
     VIII.16.
                                              VIII.91

-------
                       Table VI I 1.5




Summary of quantitative outputs for:
sJSssk
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Sol 1 Mass
Movement:
Chapter V
Total
Potential
Sed iment :
Chapter VI
Temperature:
Chapter VI 1
Line
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Output descr
Water aval I able for
streamf low
pt ion
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration

curve
Surface soi I loss
Sediment delivered
Hazard index
Weight of sediment
Acceleration factor
Sediment discharge
due to f low
change
to stream channel

Coarse >0.062 mm
Fine <0.062 mm
Total

Bed load
Suspended
Total
Total suspended sediment discharge
from a I I sources
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
acti vity
IS.t in
"^\_
/o.a ofs
3~une IS"

M.fl.
W.fl.
N.fl.
31
M.fl.
M.A.
M.fl.
^\^
/.«/ -K>ns/yr
7,1 W^r
&S* lw/xr
7.3. S" W/yr
511-9 Us/yr
1.7 af
Chapter
reference
(worksheets)
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                          vra.92

-------
                                                    llllim Road
                                                          Clearcut
                                                          Debris Slide
Figure VIII.15.—Horse Creek draihage showing potential areas of mass movement.
                              VIII P3

-------
100.0
                                   1.0                          10.0




                                 STREAM  DISCHARGE, (cfs)
100.0
                      Figure VIII.1B.—Sediment rating curve, Horse Creek watershed.
                                            Vin.94

-------
  b.  log Y = 0.31 + 0.64 log Q
     r2 =  0.95:  coefficient of determination. See
     figure Vm.16 for plot of data.
  c.  The  channel stability rating procedure  by
     Pfankuch  (1975) was used  to obtain a fair
     rating.

  Step 4.  —  Calculate  pre-silvicultural activity
potential suspended sediment discharge. See figure
VIII.13  for pre- and  post-silvicultural  activity
hydrographs. Use data from worksheet VI.1.
  a.  Use worksheet VI.1, columns (1), (2), (3), and
     (4).
  b.  Record the total of 7.1 tons/yr on worksheet
     VI.3, line A.

  Step 5.  — Calculate post-silvicultural activity
potential suspended sediment discharge (due to
streamflow increase).
  A  Use worksheet VI. 1, columns (1), (5), (6), and
     (7).
  b.  Record the total of 8.8 tons/yr on worksheet
     VI.3, line B.

  Note that there is a 24-percent increase in sedi-
ment discharge due only to flow  increase.


  Step 6.  — Convert water quality objective from
state water quality standards  (mg/1) into  units
compatible with the analysis  (tons/yr).
  a. Maximum allowable limits as set by state
     water quality standards for suspended solids
     is a  30 mg/1 increase above existing condi-
     tions.
  b. Use columns (8) and (9) on worksheet VI. 1 to
     calculate maximum allowable, sediment dis-
     charge.
  c.  Record the total of  38.6 tons/yr on worksheet
     VI.3, line C.
             Bedload Calculation

  Step 7. — Establish bedload rating curve.
  a.  Data points for bedload transport (tons/day)
     are  plotted  against  stream discharge (cfs),
     figure VIII. 17. Data are shown from worksheet
     VI.2.
  b.  log  Y = -3,43 + 2.18 log X
         r2 = 0.99: coefficient of determination
   Step 8. — Calculate  pre-silvicultural activity
bedload discharge.
   a. Use  columns  (1),  (2),  (3),  and (4)  on
     worksheet VI.2.
   b. Record the  total of 1.4 tons/yr on worksheet
     VI.3, line E.
   Step 9. — Calculate  pre-silvicultural activity
sediment discharge (suspended and bedload).
   a. From step 4, obtain 7.1  tons/yr (suspended
     sediment)  and  from  step 8,  1.4 tons/yr
     (bedload sediment) and add for a total of 8.5
     tons/yr.
   b. Record this total on worksheet VI.3, line K.
   Step 10. — Calculate post-silvicultural activity
bedload sediment discharge.
   a. Use  columns  (1),  (6),   (7), and (8) on
     worksheet VI.2.
   b. Record the  total of 1.9 tons/yr on worksheet
     VI.3, line F.


     Total Potential Sediment Calculation

   Step 11. — Obtain  total potential  sediment
delivered by soil mass movement. Sum  the con-
tributions of the coarse size (wksht. VI.3,  line D.3)
and fine size material (wksht. VI.3, line D.4) to ob-
tain the total soil  mass movement contributions
which  equal  192 tons/yr.
   Step 12.  —  Obtain total potential coarse size
sediment delivered by soil mass movement.
   a. 24 percent (table IV. 1) of delivered  soil con-
     sists of coarse silts, silt, and clay sizes  (only
     half of the  total clay is included in this
     category) [wksht. IV.l (soil 2—topsoil)]; thus
     76 percent  of the delivered soil  is coarse
     material (including the remaining half of the
     clay, as stable aggregates); therefore, 0.76 X
     192 tons  =  146 tons/yr of  coarse  material
     delivered to streams.
  b. Enter this value (146 tons/yr)  on worksheet
     VI.3, lines D.2 and J.I.
  c. Median size  of coarse portion  =  10  mm;
     record on worksheet VI.3, lines D.3  and J.3.
  Step  13.  —  Determine  washload  volume
delivered  from soil  mass movement.
  a. 24  percent  of  total  delivered  volume  is
     washload (tons/yr), therefore,
     total volume soil mass
       movement                 =  192 tons/yr
                                              VIII.95

-------








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1.0
                        10.0
                                                100.0
          STREAM DISCHARGE, (cfs)
 Figure VIII.17.—Bed load rating curve, Horse Creek watershed.
                     Vffl.96

-------
     total coarse size soil mass
       movement                 =  146 tons/yr
     total washload  (fine) size     =   46 tons/yr
  b. Record this total  (46 tons/yr)  on worksheet
     VI.3, lines  D.4  and J.2.
  Step  14. — Determine total delivered tons  of
suspended sediment from surface erosion.
  a. The total  of 17.7 tons/yr is obtained from
     worksheet IV.8.
  b. Record this value on worksheet VI.3, line D.I.

  Step  15.  —  Compare  total  potential  post-
silvicultural activity suspended sediment (mg/1)  to
selected limits (tons/yr). On worksheet VI.3:
  Add totals of:                      tons/yr
    Surface erosion (line D.I)        17.7 tons/yr
    Total post-silvicultural activity
      suspended sediment discharge
      (line B)                        8.8 tons/yr
    Soil mass movement (washload)
      (line D.4)                     46.0 tons/yr
                              Total 72.5 tons/yr
    Subtract the total pre-silvicultural
      activity suspended sediment discharge
      (line A) from the previously
      determined figure              7.1 tons/yr

    The remainder is the total increase in
      potential  suspended sediment
      discharge  (line I.I)            65.4 tons/yr
    Subtract the maximum allowable suspended
      sediment  discharge (line C) from the
      total increase  in potential suspended
      sediment  dischrge (line I.I)    38.6 tons/yr

    The remainder is the net change (this
      may be either a positive or negative
      number) (line 1.2)           +26.8 tons/yr

  Step 16. — Total potential post-silvicultural ac-
tivity sediment discharge—all sources.
  a. Summation: from steps 5, 10, 11,
  and 14.                                 tons/yr
     1.  Post-silvicultural activity sediment
        flow related  increases (step 5,
        wksht. VI.3, line B)                  8.8
     2.  Post-silvicultural activity bedload
        load, flow related increases
        (step 10, wksht. VI.3, line F)         1.9
     3.  Soil mass movement volumes
        (step 11, wksht. VI.3,
        line D.2 plus D.4)                  192.0
      4. Surface erosion source (step 14,
        wksht. VI.3, line D.I)
                     Total
  b.  Record on worksheet VI.3, line L.
 17.7
220.4
  Step 17. — Increase in total potential sediment
discharge resulting from silvicultural activity.
  a. Subtract total  pre-silvicultural activity sedi-
     ment  discharge  (step 9) from  total post-
     silvicultural activity sediment discharge (step
     16).
                                         tons/yr
      1. Total post-silvicultural activity
        (wksht. VI.3,  line L) 	220.4
      2. Total pre-silvicultural activity
        (wksht. VI.3,  line K)	8.5
      3. Total potential sediment increase . 211.9
  b. Record this total increase of 211.9 tons/yr on
     worksheet VI.3, line M.
               Channel Impacts

  Step 18. — Channel geometry.
  a. Collect channel geometry data for third-order
     stream being impacted. Record on worksheet
     VI.5.
     1. Water surface slope, measured 0.005 ft/ft
     2. Bankful stream width         4.8  ft
     3. Bankful stream depth         0.8  ft
  b. Channel geometry for the first-order stream
     being impacted. Record  on worksheet VI.5.
     1. Water surface slope           0.029 ft/ft
     2. Bankful stream width         1.0  ft
     3. Bankful stream depth         0.6  ft
  Step 19. — Evaluate post-silvicultural activity
channel impacts. Determine post-silvicultural ac-
tivity  changes that impact the channel,  which
would  influence  stream  power calculations by
altering water surface slope and/or bankful stream
width. The debris-slide on the stream reach being
evaluated will change the water surface slope from
0.029 to 0.250 with an increase in  bankful width
from 1.0 feet to 1.5 feet.
  Step 20. — Establish bedload transport rate-
stream power relationship for third-order reach or
closest adjacent drainageway that has measured
data.
                                              Vffi.97

-------
  Water surface slope
  (K) Constant
Use  worksheet  VI.4
VIH.18).
   =  0.005
   =  62.41b/ft3
for calculations
(see  fig.
  Step 21. — Make a qualitative determination of
channel change potential based on introduced sedi-
ment from soil mass movement  and channel im-
pacts: Soil mass movement source (coarse size) 146
tons/yr  (wksht.  VI.3,  line J.I).  The debris-slide
delivery to the first-order stream is instantaneous.
  a. To   determine  channel  response  on  the
     delivered material, the following calculations
     are made:
      1. Stream  power under bankful discharge for
        first-order reach (wksht.  VI.5,
          line 2A)                  1.32 ft/lb/sec
      2. Maximum sediment transport under max-
        imum stream  power at bankful discharge
        (fig.  VIII. 18)             0.0018 ft/lb/sec
  Based on this calculation, the introduced coarse
(0.08 tons/day) size  (10mm) soil mass movement
material  of  142 tons  exceeds the  transport
capability of the stream  under bankful  stream
power (0.08 tons/day).  Since bankful discharge has
a relatively short duration, the 0.08 tons/day trans-
port would be decreased as  discharge, and resul-
tant stream power is reduced over time. The ex-
pected channel response would be local deposition
of sediment (dominant particle size  of 10 mm) on
the streambed. This would adjust local slope and
the width-depth ratio of the channel (based on
similar  channel  response due to debris-slide im-
pacts on similar channels adjacent to Horse Creek).
  b. To determine the change in  steam power and
     bankful discharge for Horse Creek at the first-
     order reach,  the following  calculations are
     made:

     A     = (width 1.0 ft) (depth 0.6 ft)
           = 0.60 ft2
     S     = 0.029
     log Q = 0.366 + 1.33 log 0.60 +  0.05  log 0.029
             -0.056 (log 0.029)2
     Q     = 0.73 cfs (pre-silvicultural activity)
  c.  Changes in transport rate due to changes in
     stream power from:

      1.  Reduced surface water slope
      2.  Increased width
      3.  Reduced depth
      4.  Reduced bankful discharge
    Using worksheet VI.5:
    Post-silvicultural activity width 1.5 ft
    Post-silvicultural activity depth 0.2 ft
    Post-silvicultural activity slope  0.0250
    Post-silvicultural activity (Qb)
      discharge                    0.28 cfs
    Post-silvicultural activity stream
      power (w)                    0.29 ft/lb/sec
    Post-silvicultural activity bedload
      transport rate (fig. Vffl.18)    2.6 X 10~6
                                        ft/lb/sec

    This value (2.6  X 10~6 ft/lb/sec) is
      converted to tons/day/ft of width by
      multiplying by 86,400 sec/day and dividing
      by 2,000 Ib/ton	0.001 tons/day/ft

  This value  (0.001 tons/day/ft)  is converted  to
tons/day by multiplying by 1.5 feet (bankful width
of stream).

    Thus, a reduction in bedload sediment trans-
  port from 0.08 tons/day to 0.002 tons/day would
  indicate an increase in  sediment storage in the
  channel;  until such time, recovery would return
  to pre-silvicultural activity  rates. This would
  reduce the channel stability rating, and by the
  imbalance in sediment  supply—stream energy,
  disequilibrium  conditions  would be  expected
  (this is evaluating the coarse fragment portion of
  soil mass movement sediment supply only).

  e. Difference.
     Maximum instantaneous, pre-silvicultural
      activity transport at bankful
      (Qepre)                     0.08  tons/day
     Maximum instantaneous, post-silvicultural
      activity  transport at bankful
      (Q Bpost)                    0.002 tons/day
      A difference of              0.078 tons/day
                                              VHI.98

-------
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                                                 Measured Values
                                                 Extrapolated Values
             .01
                         .05      .1                 .5      1.0

                          STREAM POWER (CU)  (ft./lbs./sec.)
5.    10.0
           Figure VIII.18.—Bedtoad transport-stream power relationship, Horse Creek watershed.
                                         Vin.99

-------
        TEMPERATURE ANALYSIS


  Several of the proposed cutting blocks are close
to streams; removal of the trees would expose the
streams to  increased  solar  radiation.  The ad-
ditional radiation would result in an increase in the
maximum daily water temperature.
  The maximum  increase  in the  daily  water
temperature must be evaluated to determine if the
water quality objectives for the stream will be met.
The proposed clearcut in hydrographic area 29 was
selected to illustrate the procedure to estimate the
maximum potential  daily temperature increase.
All cutting  blocks  that  could impact  water
temperature would be evaluated similarly.


  Computing H, Adjusted Incident Heat Load
  Step 1. — Determine H (i.e., incident heat load)
based upon  latitude  of site, critical  time of year
(month and day), and orientation of stream.
  Step 1.1. — Select the solar ephemeris that most
closely  approaches  the latitude  of  the site,  40
1/2°N.
  Step 1.2. — Locate the declination in the solar
ephemeris (fig. VH.3) that corresponds to the date
when maximum water temperature increase is an-
ticipated:  second week in July; therefore,  use a
declination of +21 1/2°.
  Step 1.3. — Once  the declination, +21 1/2°, is
known, determine the azimuth and solar angle  for
various  times  during  the  day  from  the  solar
ephemeris (see fig. VUG) and record the values in
worksheet Vn.l. Azimuth readings are found along
the outside of the circle and are given for every 10°.
Solar angle (i.e., degrees above the horizon) is  in-
dicated by the concentric circles and ranges from
0° at the outermost circle to 90° at the center of the
circle. The time is indicated  above  the +23°27'
declination line and is given in hours, solar time.
  To determine the solar azimuth and angle that
would occur at 12:30 p.m. daylight savings time
(DST):
  Step 1.3.1. — Follow along the +211/2° declina-
tion line that is interpolated between the+20° and
+ 23°27' line. Locate the point that is equal dis-
tance between the 11 a.m. (12 noon DST) and noon
(1 p.m. DST) time interval.  This point represents
the 12:30 p.m. DST.
    Step 1.3.2. — The solar angle is determined by
  noting  where the point established above  (12:30
  p.m. with a  declination of +21 1/2°) occurs in
  respect to the  solar angle lines present .on the
  figure. The solar angle lines are represented as con-
  centric circles and range from 90° at the center to
  0° at the periphery.  The point established above
  falls on the 70° line; therefore, the solar angle is
  equal to 70°.
    Step 1.3.3. — The solar azimuth is determined
  by noting where the point established in step 1.3.1
  occurs in respect to the solar  azimuth lines that
  radiate out from the center of the circle. The point
  falls midway between  the  150° and  160°  lines;
  therefore, the solar angle equals 155°.
    More points should be selected about the midday
  period, when solar radiation is at the greatest in-
  tensity.
    Step 1.4. — Evaluate the orientation of the sun
  (i.e., azimuth and angle determined from step 1.3
  above)  with  the  stream,  and  determine what
  vegetation effectively shades the stream. To do
  this, compare stream effective width with shadow
  length. Determine the maximum solar angle (i.e.,
  maximum radiation influx to stream)  that will oc-
  cur when  the stream  is exposed following the
  silvicultural activity. Height of the existing vegeta-
  tion immediately adjacent to the stream is 70 feet.
    Step 1.4.1. — The direction the shadows fall
  across  the stream will determine effective width of
  the stream. Effective  width is computed using the
  following formula:
           measured average stream width
  EW =
        sine | azimuth stream   azimuth sun |
                                        (VII.4)
  The  azimuth of the particular stream used for
this  example is  225°.  Effective  width varies
depending  on the time of day. For example, at
12:30 (wksht. VII.l) EW would be equal to:
                      1.5ft
                                 = 1.6 ft
EW =
             sine! 225° -  155°
   The absolute value of the azimuth of the stream
 subtracted from  the  azimuth of the sun must be
 less than a 90° angle. Should the difference exceed
 90°, subtract this absolute value from 180° to ob-
 tain the correct acute angle. The sine is then taken
 of this  computed acute angle.
                                            vm.ioo

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  Step 1.4.2. — Shadow length is computed using
the formula:
         S =
height vegetation
tangent solar angle
(VII.5)
  For example, at 12:30, S would be equal to:
        S = 70 ft/tangent 70° =  25.5 ft
  Note, the only periods of the day that should be
considered are those when existing vegetation that
will be eliminated by the silvicultural activity ef-
fectively shades the stream (i.e., when the shadow
length extends onto some portion of the stream).
Those periods of the day when the stream is not ef-
fectively shaded by the existing vegetation will not
have an increase in net radiation if the vegetation is
removed by the  silvicultural activity.  Also, there
may be periods of the day when the stream is effec-
tively shaded by existing vegetation that will not
be removed by the silvicultural activity; therefore,
the proposed silvicultural activity will have no im-
pact on water temperature.
  Summary of steps 1.4.1 and 1.4.2: The existing
trees that are scheduled to be cut provide shade to
the stream. The only time when the trees do not
shade  the stream is  about 2:10 p.m., when the
stream's effective width is infinity (sun is oriented
with the stream) and the shadow length is only 28.1
feet. Therefore, removal  of this  vegetation would
result in exposure of the water surface to increased
solar radiation.
  The proposed  silvicultural activity would  have
the maximum impact on water temperature at 1
p.m. (solar noon) when the solar angle and radia-
tion are greatest.
  Step  1.5.  — Topographic  shading should  be
evaluated to determine if the water course would be
shaded  by topographic features. For topographic
shading, the  percent slope of the ground must ex-
ceed the  percent  slope  of  the  solar  angle  (i.e.,
tangent of the solar angle). In the present example,
the
     side slope =  30%
    solar angle =  72° or 308%
  Thus, topographic shading is not possible due to
the  angle of the sun  and  relatively  gentle
topographic relief.
  Step 1.6. — Calculate the incident heat load for
the site. This is obtained from reading the values
shown in figure VII.7. To read these values, apply
the following:
   1.  Select the correct curve (shown in fig. VII.7)
      obtained from the correct solar ephemeris (fig.
      VII.3): in this example, 40°N latitude, given a
      declination of  +21 1/2°: 72°. (Note that the
      midday value will always have an orientation,
      i.e., azimuth, of due south.)
   2.  In figure VII.8, interpolate between the  70°
      and 80°  curve  to obtain the 72° values.
   3.  Determine the critical  time period, which in
      step 1.4  was found to be 1 p.m.
   4.  Find the average H value. In this example, the
      travel time  through the reach  is only  0.3
      hours, so it is not necessary to find an average
      H value. From figure VII.8, with a 72° midday
      angle, the H value for 1 p.m. is approximately
      4.7 BTU/ft2-min.  (Note:  If  the  solar
      ephemeris had been used for 45°N latitude,
      the H value would have be approximately 4.8
      BTU/ft2—min.  If the  solar ephemeris had
      been used  for 35°N latitude, the H  value
      would have been 4.5 BTU/ft2-min). Figure
      Vn.8 illustrates the procedure used to obtain
      H.

   Step  1.7. — Because bedrock acts as a heat sink,
 reducing the heat load absorbed by the water, the
 H value must be corrected to reflect this heat loss.

     Hadjusted  = WH +[B(1.00-C)H]  (VII.6)

where for Horse Creek:
  W  = percent streambed without bedrock  =
         10%
  H  = unadjusted heat load = 4.7 BTU/ft2-min
         with  a  solar ephemeris for 40°N latitude
         (step 3.6)
  B   = percent streambed with rock = 90%
  C   = correction factor =  18%  (see explanation
         for C directly below)
(Note: All percent values used in eq. III.6 are in
decimal form.)
  Now,  C is obtained from figure  VII.9.  In the ex-
ample,  bedrock comprises 90  percent of the
streambed; therefore, H should be reduced by 18 i
percent.
Thus,

   Hadjusted  =[0.1X4.7]

              +  [0.9 X  (1.00 -  0.18)  X  4.7]

             =  3.94 BTU/ft2-min
                                              vm.ioi

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       Computing Q, Stream Discharge

  Step 2. — Determine stream discharge following
the  proposed  silvicultural activity  during the
critical summer low-flow period when maximum
temeratures   are   anticipated.  A  pre-activity
baseflow measurement during the critical summer
period was taken.  Discharge  during the critical
period was 0.4 cfs.
     Computing A, Adjusted Surface Area

  Step 3. — Determine the adjusted surface area of
flowing water  exposed  by  the  proposed
silvicultural activity.
  Step 3.1. — Total surface area of flowing water

                Atotai=LW            (Vll.Va)
  where:
  L   = length of exposed reach
  W   = width of flowing water
  A (  = 530 ft X 1.5 ft
    total
       = 795 ft2
  Step 3.2. — Total surface area shaded by brush

  Ashade brush = LW(% stream shaded by brush only)
                                       (VH.Tb)
            = 530 ft  X  1.5 ft  X  0.15

            =  120 ft2
  Step 3.3. — Surface area exposed under current
vegetative canopy cover; correct for transmission of
light through the existing stand that has a 65 per-
cent crown  closure.  Since  only  vertical crown
closure values are available, estimate the percen-
tage transmission of solar radiation  through the
overstory canopy. Values for these estimates may
be obtained from figure VII.D.l. A  crown closure of
65 percent permits about 8 percent transmission of
solar radiation.

A presently exposed ~ (Atotal - "shade brush I
               X % transmission  through existing
                vegetation              (VH.7c)
                = (795ft2- 120 ft2 X 0.08)
                = 54ft2

  Step 3.4. — The adjusted surface area that will
be exposed to increased solar radiation if all vegeta-
tion is  removed is
    •"•adjusted   Atotal ~~ A presently exposed
            = 795 ft2 - 54 ft2
            = 741 ft2
               Step 4.  — Estimate  AT, maximum  potential
            daily temperature increase in  °F if the  proposed
            silvicultural activity is implemented. Solve equa-
            tion VH.Sa
                       Aadjusted "adjusted
                             Q
  AT  =
X 0.000267  (VII.3a)
              A   = 741 ft2
              H   = 3.94 BTU/ft2-min
              Q   = 0.4 cfs
                    (741 ft2) (3.94 BTU/ft2 - min)
              AT  =
                              0.4 cfs
                                     X 0.000267
                  =  1.9 °F
(VH.7d)
          The Mixing Ratio Formula

  The following example is provided to illustrate
the use of the mixing ratio formula for evaluating
downstream  water  temperature  impacts.  The
water  temperature increase associated with the
proposed  clearcut in hydrographic  area  29 has
previously been evaluated, and a maximum poten-
tial daily temperature increase of 1.9°F was es-
timated.  With  similar evaluations  made  for
proposed clearcuts in hydrographic areas 27 and 28,
an estimate of the water temperature of the main
stream draining this area can now be obtained.
  The data and results of the individual water
temperature evaluations are recorded on worksheet
VII.2. The pre-silvicultural activity stream water
temperature is 55°F. The sequence of steps to ob-
tain an estimate of the water temperature of the
main stream draining this area follows.
  Hydrographic area 27 stream reach. — The es-
timated  maximum  potential  daily  stream
temperature increase (2.5°F) is added  to the pre-
silvicultural activity stream temperature (55°F) to
obtain an estimate  of the water temperature
(57.5°F) below the proposed clearcut draining this
hydrographic area.
  Hydrographic area 28 stream reach. — The es-
timated  maximum  potential  daily  stream
temperature increase (2.1°F) is added  to the pre-
silvicultural activity stream temperature (55°F) to
obtain an estimate  of the water temperature
(57.1°F) below the proposed clearcut draining this
hydrographic area.
                                           Vm.102

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  To estimate the water temperature below the
confluence of the streams draining hydrographic
areas 27 and 28, the mixing ratio formula may be
used.
where:
  TD =  temperature downstream  after  the
         tributary (hydrographic area 28)  enters
         the main stream (hydrographic area 27)
  DM =  discharge main stream = 0.4 cfs
  TM =  temperature main stream  above
         tributary = 57.5°F
  DT =  discharge stream draining treated area =
         0.3 cfs
  TT =  temperature stream  below  treated area
         equals temperature above plus computed
         temperature  increase  (i.e.,  Brown's
         model) or
         TT   = TA + AT = 55°F  + 2.1°F
              = 57.1°F
                 TA  = temperature  stream
                        above  treated area
                     = 55°F
                 AT = temperature  increase
                        computed  using
                       Brown's model = 2.1°F
Therefore,
    „    (0.4 cfs) (57.5°F)  +  (0.3 cfs)(57.1°F)
     1 n = -
                  (0.4 cfs) + (0.3 cfs)
        = 57.3°F
  The main stream below the confluence will have
a water temperature of 57.3°F.
  Hydrographic area 29 stream reach. — The es-
timated maximum potential daily stream temper-
ture increase  (1.9°F)  is  added  to the  pre-
silvicultural activity stream temperature (55°F) to
obtain  an  estimate  of  the water  temperature
(56.9°F) below the proposed clearcut draining this
hydrographic area.
  To estimate the water temperture below the con-
fluence of the main stream and the stream draining
hydrographic  area 29, the mixing ratio  formula
may be used.
         Tn =
              DMTM + DTT
(VII.8)
           where,
             TD =  temperature downstream  after  the
                    tributary  (hydrographic area 29)  enters
                    the main  stream
             DM =  discharge  main stream = 0.7 cfs
             TM =  temperature main  stream  above
                    tributary  = 57.3 °F
             DT =  discharge  stream draining treated area =
                    0.4 cfs
             TT  =  temperature  stream below  treated area
                    equals temperature above plus computed
                    temperature  increase  (i.e., Brown's
                    model)
                    TT  = TA + AT = 55°F + 1.9°F
                        = 56.9°F
                          TA = temperature  stream
                                 above treated area
                              = 55°F
                          AT = temperature  increase
                                 computed using Brown's
                                 model = 1.9°F
           Therefore,
                    =  (0.7 cfs) (57.3°F) + (0.4 cfs) (56.9°F)
                 D            (0.7 cfs) + (0.4 cfs)
                    = 57.2°F

             The main stream below the confluence will have
           a water temperature of 57.2°F or a maximum daily
           temperature increase of 2.2°F.  This  same
           procedure is  used  to  evaluate other  tributary
           streams further downstream.
             Groundwater  influence  has  previously  been
           demonstrated in the Grits Creek example.
                      ANALYSIS REVIEW
   Interpretation Of The Analysis Outputs

  The proposed  silvicultural plan  has  been
evaluated in the  preceding  discussion  and  es-
timated values from various outputs are shown in
table  VEI.5. These outputs  are  compared to
previously determined water quality  objectives.
When considering  whether these objectives have
been met or not, it is important to consider the
reliability of the computed values as previously dis-
cussed in the analysis review for Grits Creek. A
review of the data reliability and the computed
outputs for Horse  Creek indicates the possibility
                                           VIII.103

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that the water quality objectives will not be met;
therefore, a revised silvicultural plan that includes
a different mix of controls should be prepared and
evaluated.
        Comparing Analysis Outputs To
           Water Quality Objectives

   Two  potential non-point source pollutants must
 be controlled—total potential sediment and water
 temperature. Evaluation of the individual compo-
 nents of  the estimated total potential  sediment
 value (216 tons), clearly indicates the major con-
 tribution  of  potential sediment is from  soil  mass
 movement (192 tons). The  surface erosion  (17.7
 tons) and increased flow  (6.3 tons) contributions,
 although significant, are an order of magnitude less
 than the soil  mass  movement. Therefore, first
 priority is to  evaluate control opportunities  for
 minimizing  the soil mass  movement  non-point
 source.  The  second priority is to consider control
 opportunities for the surface erosion component.
   The  sediment  contribution  from  increased
 streamflows cannot be significantly altered without
 major reductions in amount of area harvested or
 changes in the cutting pattern. Since the proposed
 silvicultural plan has an optimum layout of cutting
 units, and their contribution  to increased flow was
 small, no  further consideration of flow-related con-
 trols is  necessary.
   Since existing stream temperatures (55°F) are
 suitable for the fishery resource and the area is un-
 disturbed, mitigative controls before the activity
 are unnecessary; only preventive controls need be
 considered.
   Following  is a discussion of the procedures ap-
 plied to select a different mix of controls that could
 be implemented to meet the  water quality objec-
 tives—first for total potential sediment  and then
 for temperature. These procedures are discussed in
 chapter II, appendix A, "Example Three: Selecting
 Controls When Plans Do Not Meet Water Quality
 Objectives." After  identifying control oppor-
 tunities, the  favorable and adverse impacts of the
 controls,  along with possible  interactions, are
 evaluated before finally selecting control oppor-
 tunities to be used.

Control Opportunities For Soil Mass Movement

  Since  it is  very  difficult  to  apply  effective
mitigative controls  after a large soil mass move-
ment occurs,  only preventive control opportunities
will be  evaluated. Table E.2  of "Chapter E:
Control  Opportunities"  presents the  potential
resource impacts and control opportunities.
  Soil mass movement initiation or acceleration in
the Horse Creek watershed may be caused by road
construction, due to large  fill sections, and loss of
root strength,  due to vegetative  removal. Based
upon this  assessment of the causes  of  soil  mass
movement, controls for slope configuration changes
and vegetative changes are reviewed  in table II.2,
and preventive controls are identified.
  Once  the  possible  preventive control oppor-
tunities have been  identified, table II.3 is used to
determine  which variables that influence soil mass
movement are  affected  by the various control op-
portunities. That portion of table II.3 dealing with
slope configuration and vegetative change  is ex-
amined.  From  the  possible control opportunities
for  slope configuration change, it is apparent that
some  controls   influence  several  variables and
would, therefore, be more effective in controlling
soil mass movement than controls that  influence
only one. The following preventive control oppor-
tunities affect the principal variables influencing
soil mass movement:
  1. Bench cut and compact fill
  2. Full bench section
  3. Reduce logging road density
  4. Road  and  landing location
  5. Slope rounding or reduction in slope cut
Possible  preventive controls for vegetative change
are:
  1. Cutting block  design
  2. Maintain ground cover
  From this list of possible control opportunities,
the proposed silvicultural activity was modified for
soil mass movement by:
  a. Elimination of cutting block  14 on the un-
     stable area.  The  volume  of  timber not
     removed in  this  unit has  been  obtained
     elsewhere by making slight changes to enlarge
     other  cutting units on stable terrain.
  b. Removal  of  the  road  and  landings  in
     hydrographic areas 26 and 27 that served cut-
     ting block 14.                   '
  By incorporating these  controls, the soil  mass
movement  hazard index will be reduced from high
to moderate. Worksheet V.2  is completed based
upon the  above preventive  controls. The new
silvicultural activity factor total is 7. Combining
this with the natural total of 31 gives the  new total
                                              Vm.104

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value for the modified silvicultural activity of 38,
which falls within the medium hazard range (21-
44) for soil mass movement.
  Control Opportunities For Surface Erosion

  By reviewing  worksheet IV.8,  the maps (figs.
FV.14 to IV. 18),  and using  professional judgment,
the following resource impacts and conditions were
noted:
  Problem No.  1: Some  landings  were  located
                  close to  a stream,  allowing
                  direct  delivery  of  eroded
                  material.
  Problem No.  2: Because there was no road sur-
                  facing included in the proposed
                  silvicultural  plan,   erosion
                  resulted from bare  road sur-
                  face.
  Control opportunities  for Problem  No. 1, road
and landing location, are discussed under resource
impacts for  soil  compaction, bare  soil,  excess
water, and water concentration. Bare soil and com-
paction  are directly related to the number  of
landings and  miles of road in  the  proposed
silvicultural activity  area.  Since the initial plan
has incorporated the minimum number of landings
and miles of roads, controls listed here  are not as
applicable as controls for excess water and water
concentration. Using sections B and  C  of the
"Control Opportunities" chapter,  the following ap-
plicable controls were selected:
  Excess water
    1. Cutting block  design
    2. Waterside area
    3. Revegetate treated areas
  Water concentration
    1. Reduce road grades
    2. Road and landing location
    3. Waterside areas
  The cutting block designs have been carefully
chosen,  and there is little opportunity to  make
significant  changes.  The  proposed silvicultural
plan already contains provisions  for revegetating
treated  areas.  The remaining  control,  waterside
areas, is discussed below.
  Under "water concentration," the  control oppor-
tunity "reduce road grades" is not practical, since
the  road locations  are determined  by minimum
grades  to reach benches  and  suitable  cutting
blocks. Considering the control opportunity "road
and landing location," it was determined that there
 were opportunities to make some slight modifica-
 tions in landing locations by moving them  back
 from stream channels. At the same time, the con-
 trol opportunity "waterside areas" (leaving some
 area to  act  as  a sediment filter  strip)  was also
 utilized  to  reduce  the  amount  of sediment
 delivered to  a channel.
  Using the  same calculation procedures outlined
 in chapter IV and in the example for the proposed
 silvicultural  plan, a  new analysis was made using
 revised values  for the different landing locations
 (wkshts. IV.2 to IV.4 and IV.6  to IV.8).
  By moving a landing a short distance away from
 a stream channel, three factors affecting sediment
 delivery are changed (compare wksht. IV.7 for both
 plans—proposed  and revised). First, the distance
 from the edge of the  disturbance to the stream
 channel  is increased, creating more area for sedi-
 ment deposition;  second, the amount of ground
 cover between the disturbance and channel in-
 creases;  third,  the  surface  roughness increases
 slightly.  The net result is a change in the sediment
 delivery  index from 0.11 under  proposed manage-
 ment,  to 0.01 in the modified plan.  This  would
 reduce the amount of eroded material that might
 be  delivered to  a stream by 91 percent for each
 landing  next to a  stream.  The  total from  all
 landings has been reduced from 0.9 tons/yr to 0.03
 tons/yr (wksht. IV.8  for both plans).
  Control opportunities  for Problem  No. 2,  "no
 road surfacing," are found in section B under bare
 soil, with "protection  of road bare surface areas
 with non-living material" being the most practical.
 A decision was made to use 6  inches  of crushed
 gravel on all roadbeds. The same procedures out-
 lined under roads  should  be applied  to  the
 proposed silvicultural  plan, except that  the  VM
 factor has now been  changed for the running sur-
 face from 1.24 (wksht. IV.6, proposed) to 0.005
 (wksht. IV.6, revised). The weighted VM factor for
 the road is now 0.17,  which compares with a value
 of 0.91  for  the proposed  plan. A summary on
 worksheets IV.8 (for both plans) shows that the
total for all  roads has now been reduced from 8.1
 tons/yr to 1.3 tons/yr, or an 84 percent reduction.


    Control  Opportunities For Temperature

  To meet the temperature water quality  objec-
tive, the  maximum potential daily temperature in-
crease  must  be reduced by  applying  preventive
controls. Table II.2 of "Chapter  II: Control Oppor-
tunities" presents potential  resource impacts and
                                             vm.io5

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control  opportunities  to  be  evaluated.  Water
temperature increases resulting from silvicultural
activities are caused by removal of vegetation that
shades the  stream. Therefore, controls for stream
shading are reviewed in table n.2.
   Three  preventive  control  opportunities  are
presented that  could  be used  to meet the  water
quality objectives:
   1. Cutting block design
   2. Directional felling
   3. Waterside  area
   Directional felling  away from  the  stream is
already specified in the proposed silvicultural plan
and so is not an alternative. Both cutting  block
design and waterside areas are viable control  op-
portunities.

   Cutting  block  design.  — Using  the  basic
procedure  presented  in  "Chapter  VII:
Temperature,"  compute the maximum length of
stream channel  that could be exposed with a resul-
tant  maximum potential  daily temperature  in-
crease of 1.5°F.
   From the previous evaluations: The stream reach
length that would be  exposed if the proposed
silvicultural activity was  implemented was  530
feet.  Maximum potential  daily temperature  in-
crease would be 1.9°F. The water quality objective
limits the maximum potential daily  temperature
increase to  1.5°F (temperature objective). A direct
relationship can  be  established to  estimate  the
reach  of stream that could be exposed (length  ob-
jective)/
                         L
where:
   AT  = potential daily temperature increase
   Tobj = allowable daily temperature increase
   L   = potential exposed stream length
   Lobj = allowable exposed stream length
          L,,
1.5°F
1.9°F
X  530ft  = 418ft
  By modifying the proposed cutting block design
so that no more than 418 feet of the stream is ex-
posed, the water quality objective will be met.
  Waterside areas. — Using the basic procedure
presented in "Chapter VII: Temperature," com-
pute the minimum crown closure that is required to
prevent a maximum  potential daily temperature
increase greater than 1.5°F.
                                       From the previous evaluation:
                                          Atotai = 795 ft2
                                      Ashade brush = 120 ft2
                                        Hadjusted = 3.94 BTU/ft2-min
                                              Q = 0.4 cfs
                                       Estimate  the  maximum  A adjusted value that
                                    would result in a AT value of 1.5°F, water quality
                                    objective.

                                           'A adjusted'' " adjusted )
                                      AT =
                               1.5°F  =
                                                   Q
                                                         X 0.000267
                                                                         X  0.000267
                                                      0.4 cfs

                                        Rearranging the equation gives:

                                    A       =       (1.5"F)(0.4cfB)         =  ,?of 2
                                    ^adjusted   (3 Q4 BTU/ft2_min) (0.000267)

                                    -"•adjusted   "total  •" presently exposed

                                        Rearranging the equation gives:

                                    "presently exposed ~ "total ~~ " adjusted
                                                  =  795ft2 - 570 ft2 =225 ft2


                                      presently exposed ~ ^  total ~  shade brush ' X PerC6nt
                                                    transmission through existing
                                                    vegetation

                                        Rearranging the equation gives:
                                    percent
                                    transmission
                                    through
                                    existing
                                    vegetation  = Apresently exposed /(Atotal _ A shade brush )

                                                       225 ft2
                                                  795 ft2 -  120 ft2
                                                                    = 0.34
  From figure VH.D.l, 34 percent transmission cor-
responds to a crown close of 35 percent. A reduction
in the  amount of vegetation removed from the
streamside zone so that 35 percent crown closure
existed after the silvicultural activity would meet
the water quality  objectives for temperature.
  The forest manager, after reviewing both viable
control opportunities and discussing the alter-
natives with other resource specialists, selected the
waterside area control.  Using this control,  only
mature overstory  trees were removed,  leaving  a
productive understory for other uses.
                                               VIH.106

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                        Table VI I 1.6




Summary of quantitative outputs  for:  Rgviseg ?W. tioVSg. Creek
Chapter
Hydrology:
Chapter 1 1 1
Surface
Erosion:
Chapter IV
Soil Mass
Movement:
Chapter V
Total
Potential
Sediment:
Chapter VI
Temperature:
Chapter VI 1
_ine
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19


Output descr ption
Water aval 1 ab 1 e for
streamf low
annual
Increase in water available for
annual streamf low
Peak discharge
Date of peak discharge
Hydrograph
7-day flow duration
curve
Surface soi 1 loss
Sediment del i vered
Hazard index
Weight of sediment
to stream channel

Coarse >0.062 mm
Fine <0.062 mm
Total
Acceleration factor
Sediment discharge
due to f low
change
Total suspended sec
from a 1 1 sources
Bed load
Suspended
Total
iment discharge
Increase in total potential bed load
plus suspended sediment from all
sources
Potential temperature changes
Computed value
Pre-
act i vity
IS.n< e
TIL. -3 line F
3ZL.3 lw« A
JDL.3 li«i< B
XL. 3 KM k:
S(. 3 )i»« 8
JZt.3 I.'IK fl
lirx LI* A
3ZT.3lrt»eM
JZZT.2,
                            vm.io7

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          Revised Silvicultural Plan

  Based on these possible control opportunities, a
revised silvicultural plan was prepared that con-
sisted of the following changes:
  1. Leave vegetation on  the unstable  area  in
     hydrographic  area  26,  eliminating  cutting
     block CC14.
  2. Increase slightly all other cutting units to ac-
     commodate loss of timber from cutting block
     CC14.
  3. Eliminate road and landings to serve cutting
     block CC14.
  4. Move some  landings  further  away from
     streams.
  5. Use 6 inches of crushed  rock on all road sur-
     faces.
  6. Use waterside areas with a crown closure of 35
     percent to shade streams.
  The summary of computed  outputs  for the
revised  silvicultural plan with these  controls  is
shown on  table Vin.6.
  The next step is to assess  the possible  adverse
impacts of these controls. With the removal  of
more timber on other cutting units, it is expected
that  the  surface erosion figures would increase;
however, the changes were insignificant on all but
hydrographic  areas  14  and  16. These two areas
show an increase of 0.2 tons/yr of delivered sedi-
ment (wksht. IV. 8 for both proposed and revised
plans).

  For this hypothetical example, the net  effect of
these controls has been a reduction in all non-point
source pollutant outputs (table VIII.6). The soil
mass movement hazard index was reduced from 61
to 39. The anticipated  impacts of the introduced
material  on  the first-order  drainage  has been
eliminated.  The delivered sediment from surface
erosion sources has been reduced from 17.7  to 9.8
tons/yr. The  transport  efficiency of the stream
channel will  be maintained and  is  capable of
handling  the  available  sediment  without  major
channel adjustments and  stability change. Con-
sidering  the  water  quality  objectives,  limiting
suspended sediment discharge to 38.6 tons/yr and
allowing a maximum water temperature increase of
1.5°F, the revised silvicultural plan is determined
to be acceptable from a water quality standpoint.
                                             Vm.108

-------
                  Worksheets for Horse Creek,
                  proposed and revised plans
Worksheets  are  presented  in  numerical  order  with  all III.1-III.4
proposed followed by III.1-III.4 revised, IV.1-IV.8 proposed followed
by IV.1-IV.8 revised,  etc.
                            vm.io9

-------
(1)  Watershed name  Horse.
Creek
(5)  Vegetation type  L.Q,
                                          WORKSHEET



              Water available for streamflow for the




(2)  Hydro logic region   T	



(6)  Annual precipitation  3^.3
Season
name/dates
(9)
WINTER
"/ - V*
Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11 )
Forested





Tota I for season
Area
Acres
(12)
4,00





too
%
(13)
l.ooo





l,ooo
Precipi-
tation
(in)
(14)
/Ł.!





/G.I
Snow
retention
coef .
(15)
1.0






Adjusted
snow
retention
coef.
(16)
1.0






Adjusted
precipi-
tation
(in)
(17)
/fe./







SPRING-
3/ ' Vao
Un impacted
Impacted
Forested





Total for season
too





Ł00
l.ooo





1.000
/a.i





/a.)
1.0






l.o






/a.l







SUMMER
a«
-------
III.5



existing  condition In snow dominated  regions



(3) Total watershed area  (acres)
(4)  Dominant energy-aspect
(7) Windward  length of open area (tree  heights)    O
    (8) Tree height (feet)   JO
ET
(In)
(18)
a.)






Basal
area
(ft2/ac)
(19)
400






Cover
density
(20)
33






pCdmax
(21)
100






ET
modifier
coef .
(22)
1.0






Adjusted
ET
(In)
(23)
4.1






Water available for streamflow (In)
(24)
l
-------
Notes for Worksheet 111.5

Item or
Col. No.                     	Notes
  (1)         Identification  of  watershed  or  watershed  subunlt.

  (2)         Descriptions  of hydrologlc regions  and  provinces  are given  In
              the text.

(3)-(8)        User supplied.

  (9)         Seasons  for each hydrologlc  region  are  described  In  the  text.

  (10)         The unlmpacted  compartment Includes areas  not  affected by
              siIvlcultural activity.   The Impacted compartment  Includes  areas
              affected by siIvlcultural activity.   Impacted  areas  do not  have
              to  be physically disturbed by the si IvlcuItural activity.   For
              example, If an  area  Is subject  to snow  redistribution due to a
              siIvlcultural activity.  It Is an  Impacted  area.

  (11)         Areas of similar hydrologlc  response as Identified and
              delineated by vegetation  or  si IvlcuItural  activity.

  (12)         User supplled.

  (13)         Column (12) * item  (3).

  (14)         User supplled.

  (15)         From figure I I I.6 or appendix A or  user supplied.

  (16)         Snow retention  coefficient adjustment for  open areas:
                                  .50
              Poadj  1 +  <  PO-I)(~jp

        where:

              poadj  adjusted snow retention coefficient for open areas
                      (receiving areas)

                  po  snow retention coefficient for open areas
                      open area (In acres)
                      Impacted area (in acres)
                                vm.ii2

-------
              Snow retention coefficient adjustment for forested source
              areas  (impacted  forest areas):
              p     1- PoadJ X
                f         1-X
         where:

              Pf =  adjusted snow  retention coefficient for areas affected by
                    snow  redistribution  (source areas)
                    open  area  (In  acres)
                    Impacted area  (In acres)
  (17)         Column (14) x column (16)

  (18)         From figures  I I I.24  to  I I I.40 or user supplied.

  (19)         User supplied  (not required  if  % cover density  Is user
              supplled).

  (20)         From figures  111.41  to  I I I.45 or user supplied.

  (21)         (Column (20)  T C,jmax> *  10°  where Cdmax  is tne  % cover density
              required  for  complete hydro logic utilization.   C(jmax  's
              determined  by  professional judgment  at the site.

  (22)         From figures  I I I.46  to  I I I.56.

  (23)         Column (18) x  column (22).

(24)-(29)     The quanitity  [column  (17)-column (23)] x column (13).

  (30)         Sum of column  (24).

  (31)         Sum of column  (25).

  (32)         Sum of column  (26).

  (33)         Sum of column  (27).

  (34)         Sum of column  (28).

  (35)         Sum of column  (29).
                                   vin.m

-------
(1)  Watershed name
                           Creek.
(5)  Vegetation type LoOagbolg.  Pine
                                           WORKSHEET




               Water  available for streamflow for the




(2)  Hydrologic  region    T	



(6)  Annual  precipitation   3#3  /flC/HS	
Season
name/dates
(9)
WINTER
tf- &
Si Ivicu Itural prescription
Compartment
(10)
Un impacted
Impacted
Si Ivicultural
state
(11)
FowjsteJ j

F«west«d
Clearoct


Total for season
Area
Acres
(12)
(3S-.0

153-5-
311 .5


(,00. 0
%
(13)
.aar

.a»«,
.51?


l.ooo
Precipi-
tation
(in)
(14)
llc.l

IU
/fe.l


/t..l
Snow
retention
coef .
(15)
1.00

—
1.3



Adjusted
snow
retention
coef.
(16)
1.00

.55"
I.1X



Adjusted
precipi-
tation
(In)
(17)
(U

*.^
l?.6,




SPRING-
3/ k/
T( /30
Un impacted
Impacted
Festal

Rji-estei
Cteafcui


Tota I for season
/3S.O

I53.5"
311.5"


too.o
.aas"

.ssfc
.519


1.000
U./

U.I
ia./


ya.i
1.00

_
A3



1.00

.55-
/.ax



/a./

fe.7
(4.8




summER
and
FflLL
V, - >/30


Un impacted
Impacted
Forested

Forested
Clea.irc.ut


Total for season
I35.O

153. ff
311.5


iOO.O
•aas"

.asfe
.si?


1.000
6.)

ti
fe.i


fe.i
/.o

1.0
1.0



L_ '-°

/.o
/.o



tl

kl
4.1




Un impacted
Impacted






Total for season











































Water
aval I able
for annual
streamflow
(in)
Un impacted
Impacted
F«w«ted (30)
(31 )
Forested (32)
Cleavaeb (33)
(34)
(35)
                                                Vffl.114

-------
III.6




proposed condition  In  snow dominated  regions




(3) Total  watershed area (acres)       (oOO
                                                         (4) Dominant energy-aspect
(7)  Windward length  of  open  area (tree  heights)
(8)  Tree height  (feet)   70
ET
(in)
(18)
4.1

3.1
S.I



Basal
area
(ft2/ac)
(19)
AOO

100
0



Cover
density
(20)
33

33
O



'^dmax
(21)
100

loo
o



ET
modi f ler
coef .
(22)
1.00

1.00
.to



Adjusted
ET
(In)
(23)
3.1

4.1
1.3



Water available for streamflow (In)
(24)
3.2<






(25)







(26)


1-7




(27)



7.5



(28)







(29)







7.4,

4.1
7.t>



a oo

200
0



33

33
O



100

IOD
0



1.00

l.oo
1.07



7. la

6 1
8.1



/.O















0.2,







3.S"

















9,2,

y A,
7.2.



3.0O

800
O



33

33
0



100

(00
0



/.oo

/.oo
.55"



9.1

9. 1
5.1



-0.7















-0.8







o.r

















                                                                                   (3.5-
                                                 Vffl.115

-------
Notes for Worksheet I I I.6

Item or
Co I . No.                          	Notes
  (1)         Identification of watershed or watershed subunit.

  (2)         Descriptions of hydrologic regions and provinces are given  in
              the text.

(3)-(8)       User supplled.

  (9)         Seasons for each hydrologic region are described in the text.

  (10)        The unimpacted compartment includes areas not affected by
              siIvicultural  activity.  The impacted compartment includes areas
              affected by siIvicultural  activity.  Impacted areas do not have
              to be physically disturbed by the si IvicuItural  activity.  For
              example, if an area is subject to snow redistribution due to a
              siIvicuItural  activity, it is an impacted area.

  (11)        Areas of similar hydrologic response as identified and
              delineated by vegetation or si IvicuItural  activity.

  (12)        User supplied.

  (13)        Column (12)  T item (3).

  (14)        User supplied.

  (15)        From figure I I I.6 or appendix A or user supplied.

  (16)        Snow retention coefficient adjustment for open areas:
                                   .50
               Poadj   1  + (  P0-' )(~)
        where:
               Poadj   adjusted snow retention coefficient for open areas
                       (receiving areas)

                  Po   snow retention coefficient for open areas
                       open area (in acres)
                       impacted area (In  acres)
                               VIII.116

-------
             Snow retention coefficient adjustment for forested source
             areas  (Impacted forest areas):
              p     1- PoadJ X
               f         1-X
        where:

              Pf    adjusted snow retention coefficient for areas affected by
                    snow  redistribution  (source areas)
                    open  area (In acres)
                    Impacted area (In acres)
  (17)        Column (14) x column  (16)

  (18)        From figures  I I I.24 to  11 I.40 or user supplled.

  (19)        User supplied  (not required  if  % cover density  Is user
             supplled).

  (20)        From figures  111.41 to  I I I.45 or user supplied.

  (21)        (Column  (20) T C(jmax) x 100  where Cdmax  is the  % cover density
             required  for complete hydro I ogle utilization.   C(jnax is
             determined  by  professional  judgment at the site.

  (22)        From figures  I I 1.46 to  I I 1.56.

  (23)        Column (18) x  column  (22).

(24)-(29)     The quanitity  [column (17)-column (23)3  * column (13).

  (30)        Sum of column  (24).

  (31)        Sum of column  (25).

  (32)        Sum of column  (26).

  (33)        Sum of column  (27).

  (34)        Sum of column  (28).

  (35)        Sum of column  (29).
                                 vm.ii7

-------
                                                                                 WORKSHEET
                                                             Existing condition hydrograph

                                                   ( 1 )  Watershed name  UorSK.
Date
or
interval
(3)
APRIL 2
14
ao
3fc
MflY OL
8
14
30
3fc
JUNE 1
7
13
1?
ZS
JltLV /
7
13
1?
SLS
31
Distribution of water
Un impacted
Forested
%
(4)
.OOOO
.OOOO
.0000
.0000
.0050
.0150
.0550
.0.sa
?.09
/0.83
?.o?
6.82-

-------
111.7

for snow dominated  regions

(2) Hydrologlc region    4
available for annual streamflow
Impacted (continued)

%
(13)




















Inches
(14)




















cfs
(15)





















%
(16)




















Inches
(17)




















cfs
(18)





















%
(19)




















Inches
(20)




















cfs
(21)




















Compos 1 te
hydrograph
cfs
(22)
.00
.00
.00
.00
.3*
.77
1*4-
Ml
3.87
S.3S-
&.S2,
?.o?
10.13
9.0?
4-8X

-------
                                                                                    WORKSHEET

                                                                Proposed condition hydrograph

                                                      (1)  Watershed name  HotSt
Date
or
Interval
(3)
flPRIU 8
1*
30
at
Mfl/ a
8
14
ao
2k
TUNE /
7
13
I?
as
JU.LV /
7
13
19
25
31
Distribution of water
Un 1 mpacted
Forested
%
(4)
.0000
.0000
.OOOO
.0000
.0050
.0/50
.oaso
.0
-------
II I .8

for  snow  dominated  regions

(2)  Hydro I ogle  region  	'
available for annual streamflow
Impacted (continued)
Clearoit
%
(13)
.0000
.ocas'
.0075"
.•oaso
.ofas
.ofcs-o
.083&
.1075"
• UTS'
.(IcSO
.l
-------
to
to
                                                         WORKSHEET IV.1

                                  Soil characteristics for the  r/OrSC
watershed









Soi 1 group
Topsoi 1
i
Subsoi 1
Topsoi 1
Subsoi 1
Topsoi 1
3
Subsoi 1



|

-i- •—
c
0 0
U -0 1
l_ C O
0 (0 •
CL in CM
10
AO
so
10
(>S
70

c
(D E
ui E
0 in
C 0
•i— • — •
c: M- o
(D 1
O >^O
L. 1_ ^
Q)  O
10
30
as-
ao
iff
(s-
— i

-1- E
— in
en o
•
+- 0 O
c to i
0 1- CN
(J (D >Ł>
U O 0
0) U •
a. = o
\Z
9
4
3
a
?

E

CM
o
o
-f— •
C O
0) 1
(j +- in
1_ — O
Q — .
a. in o
30
^
IS
15-
10
5"



e
^
^_
C CM
Q) O
O >-O
1_ (D «
Q) — O
CL U V
10
as-
10
35
/O
/o





+- u
c: — i_
0 c 0
u ro +-
t- D)+-
0 1_ ID
Q- O E
7.0
1.0
1.0
l.o
V.o
3-0


Soi 1
structure




MSLE
code
3
4
L ..
V
Ą
a
3



Descrip-
ti ve
TO coarse
G-MwaLflR
PRlsmwrJc
8LOCKY
BiocKy
FlME*
&RRUULAR.
COARSE"


Soi 1
permeabi 1 ity




MSLE
code
5"
5"

-------
                                                                                                           1 of 3
                Creek
                      WORKSHEET IV.2


watershed erosion response unit management data for use

sediment delivery index, hydrographic area 3 «  propost
                      in
                                                                                   the MSLE

                                                                                   plarx
and
Erosion
response
un it
1 . CC 3.1
2. CC3-3L
5. L3, I
4. R3J
5. CU.T
5. aeo
7. FILL
a. R3.a -*/
9. C.U.T
10. BED
11- FIUU
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
S lope
length of
d isturbed
area (ft)
IOO
ISO
kS

fc.7














Length of
road
section
(ft)



680



30

















Average
width of
di sturbance
(ft)


410
J7.8
a.^
/a.o
a. 9
/7.g
a.9
/a.o
2.?














Area
(sq.ft.)

























JJ
Area
(acres)
8.0
(o
O.33
0.31



o.oi

















to
CO
        nj
                 =  43,560
     noad &
-------
                WORKSHEET I V. 2—continued
                                                                       2 of  3
3/
Area with surface residues — '
Percent
of total
area
1. 6S-
2. (,o
3. 0
4.
5. (00
6. o
1 . IOO
8.
9. \OO
10. o
11. 100
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Percent
of surface
with mulch
70
10
—

70
—
70

70
—
70














Percent of JU
area with
fine roots
?0
ffS"
—

so
—
so

50
—
so














3/
Open area — '
Percent
of total
area
3S-
VO
/OO

O
/OO
O

0
IOO
o














Percent
of surface
with mulch
10
10
UMKWOWAJ

— .
O
—

• —
O
l_ —














Percent of JU
area with
f i ne roots
?o
ffS
UMKNOtuAj

—
0
—

—
O
—














Are open areas
separated by
f i Iter strips?
yes
yes
NO


NO



NO















Percent of
total area
with canopy
O
O
o

?o
o
?0

?o
0
?o















— Not
e.nd o&  ^6t6-t i/eot
     to  i>c.al.pe.d
  the.
until ve.QntaŁion 

-------
                                                  WORKSHEET I V .2—cont i nued
                                                                                                       3  of  3
Average
min imum
height of
canopy
(m)
1 . —
o _
3. —
4.
5.
6.
7.
o.s-
—
o.s
8.
9.
o.s
10. —
T1
0.5-
12.
T3.
14.
T5.
16.
T7.
18.
19.
20.
2
.
22.
23.
24.
25.
Time for
recovery
(mo)
UNkwowM
U.NKWOUJW
U.WK.NJOWN
I YEAR



1 YEAR

















Average
dist. from
disturbance
to stream
channel (ft)
IS"
IS
O
IOO



o

















Overal 1
slope shape
between
di sturbance
and channel
STRfll&HT
STRfllG-HT
STRfll&HT
STRflKJHT



STRfilGriT

















Percent
ground
cover in
f i Iter
str ip
90
JJm. cu> stable. aggie.gat&A and  that the.
  band and bJUUL e.nt&i the. Ae.dune.nt deAiveAy
                                                                                                       tke. day pint,  v&iy

-------
                                                      WORKSHEET  IV. 3
                          Estimates of soil  loss and delivered sediment by erosion  response unit
                          for hydrographic area    3 _ of  Horse Cteefc, _ watershed
p . Jl
Erosion response
un it

CC3.I
CC3.2,

U3.I

K3.I
R3.a


Sol 1
un it

ra.
Ta.

Til

S3.
SSL


R

^5-
^ŁT

45-

fS"
4sr


K

o.w
o.as

o.as

0.30
0.30


LS

//.*/
7-4,

o.v.o

0.3

0.3
0.01


Surface
soi 1 loss
(tons/yr )

23.0
15.0

/.S"

18-0
0.6


SO,

o.oa
0.0 a.

0,11

o.o/
o.aa.


Del i vered
sediment
(tons/yr)

0-S
0.3

0.2.

0.2.
O./


to
O5
         -  CC -
             L - Landing
             R - Road
         -   T -
             S - Sub&oU.
            a {Wi
oft two LS
                                     ,  onu {on &ac.h kal& o& the. fioad, Atat&ing at the. canteA Line, and i.ncŁu.ding

-------
                                                  WORKSHEET IV.4
                           Estimated VM factors for si IvicuItural erosion response units
                                    Crgefc.	 watershed,  hydrographic area    3 .
Lodging residue area
irosion
response
un it
CC3.I
ccs.a.














Fraction
of
total
area
0.4,5
o.feo














Mulch
(duff &
residue)
O.08
O.08














Canopy
l.o
1.0














Roots
o.io
o.ll














Sub
VM
o.oos
O-OOS"














Open area
Fraction
percent
of total
area
0-3ST
o.yo














Mu 1 ch
(duff &
residue)
0.7*
0.7S














Canopy
l.o
1.0














Roots
O.IO
0.11














Filter
strip
0.5"
0.5-














Sub
VM
o.o/he.&t IV. 3.

-------
                              WORKSHEET  IV.5
        Example of estimated monthly change  in VM  factor  following

  construction for road cuts and fills  in  H0>"SC  Cree-k>    watershed,


                    hydrographic area    3.	
Month
Sep.l/
OctJ/
Nov.
Dec.2/
Jan.^/
FebJ/
March^/
April*/
Mayf/
June^/
Julyl/
AU2j_
Percent cover and VM subfactors
Mulch
Percent
0
8
ao
—
—
—
—
10
as
so
&0
70
VM
/.oo
0.80
o.s?




0.78
0.5T0
o.3a
0.31S
O.I?
Canopy
Percent | VM
0
la
a a.
—
—
—
—
10
ao
70
g3
90
/.oo
O.S8
0.^0




o.?o
o.sa
O.MI
0.30
o.as
Roots
Percent









ao
^yo
50
VM









0.3S
oa7
o.:u
Month 1 y
VM
1.00
0.70
o.V7
—
—
—
—
0.70
o.V/
0-OS
o.oa
O.Oj
-/ Begin seeding, enough rain is assumed to ensure seed germination.
2/
-  Snow cover with no erosive precipitation.

-  Significant canopy effect developing.
47
-  Snowmelt runoff occurs, some protective vegetative cover  lost  during
    winter.


-  Significant root network developing from seeded grass.
                                  VIII. 128

-------
                   WORKSHEET IV.6
         Weighting of VM values for roads  in
Ho»*SC,  Creek    watershed, hydrographic area
Erosion
response
unit

A 3.1

R3.A


























Cut or fill
Fraction
of total VM
width

(o./«9) (o.«a;

(o.y&a?; (0-W


























Roadbed
Fraction
of total VM
wi dth

+ (o.fc7v*X i.a.
-------
                                                           WORKSHEET  IV.7
                                Factors for sediment  delivery index  from  erosion response units  in
                                                             watershed, hydrographic area    3.
Eros i on
response
unit
CC3.I
ccs.a.
L3.I
fi.3.1
boo
<\ «J . ot^




Water jj
aval labi 1 ity
JJ
o.oo4
O.OOfe
0.003
0.004
o.ooH *




Texture
of eroded
material
^5"
45"
45-
MS
48




Percent
ground
cover
between
disturbance
and channel
?o
i.
fit (faaieti  on
— ' Maximum )5 mtn. annual
-' In^^ttfuution >mte. o
-------
                                         WORKSHEET IV.8
                  Estimated  tons  of  sediment delivered to a channel  for each
        hydrographic area  and  type of  disturbance for   Hovsg.  Creelc
watershed
pi-onoseo ryianrtaewe/iJ
Hydro-
graphic
area
/
a
3
1
s
(o
7
3
9
10
II
i a.
I3
if
IS
ik
17
1?
1?
ao
^
a?
a.8
a?
30
SI
32.
Col umn
total
Distur-
bance
total
Percent
Cutting units
CC,
0.0
0.3
o.s
0.0
0.3
—
o.o
O.I
o.a
0.2.
o.o
o.l
—
0.3
0.0
0.3
o.o
o.o
0.0
0.3
0.0
0.0
0.0
0.3
o.o
o.o
o.a
3.1
CC2
0.0
o.a
0.3

o./



o.a
0.3

o.o







Q.I
0.3
o.s
0.3
0.3
o.o
O.I
o.o
2.7
CC3

0.3



















0.3
O.I
O.I

o.s-

/.3
CC4

o.a



















0.3
0.3
oA



/.a
CC5





















0.1





0-1
8.7
M?. 2.
Landings
LI
0.0
O.I
o.a
o.o
o.o




aa

o.o


0.0
o.o

o.o

0.0
O.I
O.I

o.o
o.o
o.o
o.a
o.?
1-2
o.o


o.o







o.o





o.o


o.o






0.0
13
0.0










o.o








o.o






0.0
o.?
S.I
Roads
"1
o.o
O.I
o.a
0.0
o.o
0.0
0.0
o.l
O.I
o.a
0.0
O.I
o.a
o.a
0-0
0.0
o.o
O.o
o.l
O.I
o.a.
o.o
o.a
o.a
o.o
o.o
o.s
2.3
R2
o.o
o.l
o.l
o.o
o.l
0.0
O.I
O.I

o.l
o.a
0.3
O.I
O.I
0.3
0.3
0.3
0.0



o.a
o./
O.I
0.0
o.o
o.a
3.3
*3

0.1

O.I
O.I
O.I

O.I

o.l
04

0.3
0.3
0.3
O.I
0.2
0.2



0.1
Q.I




*.l
R4

Q.I



O.I

O.I


O.I



O.I


O.I



o.l
0.1




0.8
R5










O.I
















o.l
8.1

-------
                                                                                                             1  of  3
          Horse  Creek
                      WORKSHEET IV.2


watershed erosion response unit management  data  for  use

sediment delivery index,  hydrographic  area  3,
in  the MSLE  and
Eros ion
response
unit
1. caa.J
2. CC3.a
3. L3. /
4. R3./
5. CUT
6. BEb
7. PILL
8. R3-A JJ
9. FILL
10. flED
11. PILL
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
Slope
length of
disturbed
area (ft)
Maa
80
48


-------
                                                                                                          2 of 3
                                                    WORKSHEET  I V.2—-centinued
Area with surface residues—'
Percent
of total
area
1 . 6>S
2. fcO
3. 0
4.
5. 100
6. 0
7. IOO
8.
9. IOO
10. o
11. IOO
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Percent
of surface
with mu Ich
90
90
—

70
—
7O

70
—
70














Percent of
area with ,
fine roots -u
?0
85"
—

so
—
SO

so
—
5-0














Open area — /
Percent
of total
area
3S
i the end ofa tke fi-Lut yeaA fio-ttoMcng
A /
—  Not appLicabie to  bcatped asiecu> u.ntU. vegetation AJ.

—  S-tx -inc.hu 0){ c/MAhed gftave-t, 3/4 -inch on moJUL&i -in i>-ize,  placed on Banning

-------
                                                                 WORKSHEET IV.2—continued
                                                                                                                      3 of  3
Average
minimum
height of
canopy
(m)
1 — ••
2. —
3. —
4.
5. O.S
6. —
7. o.S
8.
9. O.S
10. _
11. O.S
12.
13.
14.
15.
16.
17.
18.
19.
20.
21 .
22.
23.
24.
25.
T i me for
recovery
(mo)
UMKNOtuU
UNKNOWN
UMtCNOU)M
1 veflR.



1 Y5AH

















Average
d i st . from
disturbance
to stream
channel (ft)
IS
IS"
a.o
100



0

















Over a 1 1
slope shape
between
disturbance
and channel
STRAIGHT
STRAt&HT
STRfllG-MT
STR.A1G-HT



STRRI6HT

















Percent
ground
cover in
f i Iter
str ip
90
90
90
ff9



0

















Surface
roughness
(qual i-
tat i ve )
rnoDeR.«TE
m«DER«Te
W^>l>fR.ATe
moaeeATe



SMOOTH

















Texture of
eroded Ł/
mater ial —
(% si It +
clay)
4S
«/Ł•
«*s-
US



W

















Percent
slope
between
disturbance
and channel
38
30
5"
30



47

















a
—  It  hcu>  been /UAumud that k o& the. cZ&y
                   and  &-Ltt e.nteA the, -Ae.dJjme.nt
on-A^te. cu>
      &y&te.m.
                                                                                    agg^ingcutu and that the. tut oft  the. c.tay

-------
                                                       WORKSHEET IV.3

                          Estimates  of  soil  loss and delivered sediment by erosion response  unit
                          for  hydrographic area    3      of  Morse  Cr€ek	  watershed
Erosion response
unit -I/

CC 3.1
CC 3.2
L.3.1
R3.\
R3.^




Soili|
unit^

T2,
T 2.
T 2.
s a.
s a.




R

45
45"
US
HZ
4S




K

o.as
o.as
o.as
0-30
0.30




LS

114
<>.,  one
   a
eac/i
                                                                 load,  *>tcviŁing at thu ce.nteA Line, and Including

-------
                                                        WORKSHEET IV.4
                                Estimated VM factors  for  siIvicuIturaI erosion  response units
                                MorSS  Creak	  watershed,  hydrographic  area   .3
Logging residue area
Erosion
response
un it
CC3.I
CCS. 3.
f\3. 1 CttT
BED
FILL
R3.SI FILL
BED
FILL








Fract ion
of
total
area
O.foS
O.(o0














Mulch
(duff &
residue)
O.08
O.O8














Canopy
l.o
l.o














Roots
OJO
o.//














Sub
VM
0.005-
0.005"














Open area
Fraction
percent
of total
area
0.3S-
O.MO

l.oo


l.oo









Mulch
(duff &
residue)
0.78
0.7S

O.OOS2'


O.ooS--^









Canopy
l.o
1.0

l.o


l.o









Roots
o-io
o.//














Filter
strip
o.s
0.5-














Sub
VM
o.o/
-------
                   WORKSHEET  IV.6
         Weighting of VM values for roads in
tiorge  Creek	 watershed, hydrographic area
Erosion
response
un it
KS.I
R3.3.




























Cut or fill
Fraction
of total VM
wi dth
(




























Roadbed
Fraction
of total VM
wi dth
+ (o.feo) (o.oos^
+ /0-*o> fa<»S\
\ J ^I«TT-M^



























Fi 1 1
Fraction
of total VM
width
+ (o.ao) fo.te)
•f fo.ao^ (o<<4-i\




























Weighted
VM
= 0,17
= 0. /7




























                       VHI.137

-------
                                                                        WORKSHEET  IV.7


                                              Factors for sediment delivery index  from  erosion response units in


                                               nOrSŁ  Creek.	 watershed,  hydrographic area     3 .
Erosion
response
unit
CC3.I
ccs.a.

L3.|

R 3.1
R3.2.


Water
aval labi I i ty
_ay
O.OO
-------
                                           WORKSHEET IV.8
                    Estimated tons of sediment delivered to a channel  for each
         hydrographlc  area and type of  disturbance for  Horse,  Creek	 watershedj

Hydro-
graphic
area
/
a.
3
1
0.04
0.0



O.o3
0.01
o.oa
0.0
0.0
0.03
o.is
R3

o.oa

O.oi
o.oa
o.oa

0.01

o.oi
0.03

0.01
o.o
0.03
o.oa
0.03
0.03



o.oa.
0.03




0.3S
R4

0.01



0.01

0.01


o.oa.



0.01


o.oi


i/
0.01





O.W
«5










o.oa.
















0.01
/.30
0.3 ll /3.X
Total
tons/yr
o.o
/.o?
o.%
o.oa.
0.11
o.o &o>i mtu,t, uiaAtLng.
T/ Landing vio&ian leAponte. u.nitt>  uLuru-naJtid by c.ontnat!> {,on maA& waiting.
bj Road  eA.o64.on tuponAe. urMt, eliminated by c.onŁnot!> ^01 ma&i
                                               VIII.139

-------
                       WORKSHEET V.1




Debris avalanche-debris flow natural  factor evaluation form



I ndex
High
^ed i urn
.ow


Slope
grad lent
30
©
5


Soi I
depth
3
©
1

Subsurface
dra i naae
character i st ics
©
2
1


Soi 1
texture
3
@
0
Bedd inq
structure
and
or ientat ion
3
©
1


Slope
conf iqurat ion
3
©
1

Precipi-
tation
input
12
©
3
                  Factor summation table
Gross hazard index
High
Medium
Low
Factor ranqe
Greater than 44
21 - 44
Less than 21
Natural

31


-------
             WORKSHEET V.2

Debris avalanche-debris flow management
    related factor evaluation form
Index
High
Medium
-OW
Vegetation
cover remova 1
©
5
2
Roads and
skidways
(§)
8
2
Harvest
methods
@
2
0
        Factor summation table
Gross hazard index
High
^ledi urn
Low
Range
Greater than 44
21 - 44
Less than 21
Natural +
management
31431 = 6^


                vni.i4i

-------
          WORKSHEET V.5




Estimation of volume per failure

S 1 i de
Number
Worse
/

/Hole
/
i
3
i
S~

I



Debris avalanche-debris flow
Natural
Creek
X

Oeek






X



Man-
induced




X
X
X
X
X





Length
(ft)

w


80
U9
Ul
It3
;s-

//s



Width
(ft)

<2S


*1
a&
/7
/*
53

/?



Depth
(ft)

AS"


AS"
AS"
AS-
AS"
A5-

AS



Vol ume
(ft3)

3,5-3.8


3,8SO
^031
3,08(o
3,0*11
3,a7?

3,3^0



Slump earthflow
Natura 1














Man-
induced














Length
(ft)














Width
(ft)














Depth
(ft)














Vol ume
(ft3)















-------
This page intentionally left blank.
             VHI.143

-------
                                           WORKSHEET V.6

                  Estimation of soil mass movement delivered to the stream channel
(1 )  Watershed name
                      Mal
               Factor
                 (2)
                                                                Soil  mass  movement  type
           Debris avalanche-
           Debris flow
                                                  Natural
                                                    (3)
                    Man-induced
                        (4)
                                                                                    S 1 ump  f low
Natura
  (5)
Man-inducec
    (6)
1   Total  volume  (Vt)  in  ft
           3480
2  Total  number  of  failures (N)
3  Average volume per  failure (VAMft )
4  Number of  failures per slope
   class
5  Number  of  failures per slope
   position category
   Total  volume per slope class or
   position category
          (V)  in ft3
     V  = VA x N
Va'
           3^0

                                       vc'
                                       V
  Unit weight of dry soil
  material (Yd) (Ib/ft3)
                                            VIH.144

-------
WORKSHEET V.6—cent inued
8 Total weight per slope class
or position category (W)
in tons
2,060
wa
WB,
Wb
wb.
We
wc-
Wdi
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S W x D
Da
Da'
Db
°b'
DC
DC'
Dd'
sa
SB-
Sb
V
sc
Sc'
Sd'
12 Total quantity of sediment delivered to
the stream channel in tons
13 Acceleration factor (f)
f TSs! Ivicultural actlvity/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed sllvi-
cultural activity (TS) in tons
TSsi Ivicultural activity = Tsnatural x f
/t3
—
—
/
smootK
O.tl
—
—
/
lol
—
—
/
|0|
W
3
-------
                                           WORKSHEET V.6

                 Estimation of soi I  mass movement del ivered  to the  stream  channel
(1)   Watershed name  Horse
                    H
              Factor
                 (2)
                                                                Soi 1 mass movement type
                                                  Debris avalanche-
                                                  Debris flow
                                                  Natural   Man-induced
                                                    (3)         (4)
                                                                                   Slump  flow
                                                                              Natural  Man-lnducec
                                                                                (5)        (6)
1   Total  volume  (V-f)  in ft
2  Total  number of failures (N)
3  Average volume per failure (VAMft )
                                                  ssas
4  Number  of  failures per slope
   class
5  Number of  failures per slope
   position category
                                       a1
6  Total  volume  per slope class or
   position  category
          (V)  in  ft'
     V   VA  x  N
                                       va'
                                       V
7  Unit weight of  dry soil
   material  (Y(j>  (Ib/ft3)
                                                    ?o
                                             VHI.146

-------
WORKSHEET V.6--continued
B Total weight per slope class
or position category (W)
in tons
w = V x Yd
2,000
wa
W3'
Wb
wb,
We
WC'
Wdi
9 Slope irregularity — smooth or irregular
10 Delivery potential (D) as a
decimal percent for slope
class or position category
11 Total weight of soil delivered
per slope class or position
category (S) in tons
S = W x D
Da
Da'
Db
Db'
DC
DC'
Dd'
Sa
V
Sb
Sb,
Sc
sc.
sd-
12 Total quantity of sediment delivered to
the stream channel in tons
13 Acceleration factor (f)
f = TSsilvlcultural actl vlty/TSnatural
14 Estimated increase in soil delivered to the
stream channel due to the proposed silvi-
cultural activity (TS) in tons
T^si | vicu Itural activity = ^natural x *
—
(5?
/
	
sr»tooTn
—
o.4o
—
/
—
64
—
/
Li
	
	
^^
	
	
	
—
	
^^
—
—
	
^^
—
FVOKH Mule
Cr««lc
^.0
/?!
—
—
—
—
— .
—
—
—
—
	
—
—
—
—
—
—
—
	
—
	
	
—
—
—
—
—
	
	
	
	
       VIII.147

-------
             WORKSHEET V.2
Debris avalanche-debris flow management
    related factor evaluation  form
Index
High
vied ium
_ow
Vegetation
cover removal
8
5
©
Roads and
skidways
20
8

-------
                                                          WORKSHEET V I.I
ffte onJ Post fi>v P~p»s«d av>J Rwised S/wcuW»r»l Ha,sJ
(1 )
Time increment
(a)
ith hydro-
graphs use
ate; with
flow dura-
ion curves
use % of
365 days
flPR 8
14
w
Xo
MAY a
?
/

(0
(o
(,
V
^y
(a
^0
(o

6> (2) Pre- si Ivl- cu 1 tural activity flow (cfs) 0.00 0.34 0.?7 1.1,4 3.frl 3.87 5.3S- 6.8a J.o? 10. AS 7.0? 6.81 Y.«l 3.44 1.14 0.34 0.00 <3) Sus- pended sed i ment concen- trat ion (mg/l) — 1.0 9.0 a. 8 3.7 f.8 5.9 6.? 8.3 8.? 8.3 4,9 5.1 3.6> 3.1 /.o — (4) Total increment suspended sedi ment cols. (2) x (3) x U.b) x .0027 (tons) 0.01 0.03 0.0? o. /t> 0.3O 0.51 0.7fc /.« /.v* /.a.2. OK 0.35 0./ 1.0 O.S" - (7) Total Increment post-si Ivlcultural activity suspended sed iment cols. (5) x (6) x (l.c) x .0027 (tons) — MEGLI 0.01 0.04> O.IS 0.32, 0.4? 0.77 /.sa. /.t.7 /.so /.as 0.70- 0.33 0./S" O.OS" 0.02, 0.01 NESLI — (8) Max i mum concentra- tions from selected water qual Ity objective (mg/l) — - — — 31.0 3JI.O 33.8 33.7 34.8 35.9 34,? 38.3 38.9 3S.3 3C.7 3S.I 33.4 33.2. 31. 0 — (9) Max i mum sediment discharge cols. (2) x (8) x U.b) x .0027 (tons) — — - — 0.11 O.SO 0.87 1.13 3.18 3.11 4.08 S.(,4 4.^ Ł.bi 1.0S 3.39 /.33 0.60 0.17 (Totals are rounded to nearest tenth) Total Total 8.8 tons/yr Summary: Total pre-slIvicultural activity suspended sediment discharge = TJ Total post-si Ivicultural activity suspended sediment discharge = g.g Total maximum sediment discharge = Total 38.(o tons/yr


-------
                                                                                                            WORKSHEET VI.2
Vl
O
Bedload sediment quantification for Horse Creek

(1 )
Time increment
(a)
With hydro-
graphs use
date; with
flow dura-
tion curves
use % of
365 days
APR 8
It
20
afc
MAY 1
8
H
AO
at
TUIO /
7
13
1?
zs
JU.L /
7
13
1?
AS
31
(b)
Number
of
days
pre-
si Ivl-
cu 1 tura 1
activity
6.
Ł>
fe
fc
&
k
4,
6 J
lo
C.
k
Ł»
(«
&
G.
k
6
&
fe
6
(c)
Number
of
days
post-
si IvI-
cu 1 tural
act 1 v ity
6,
(.
1.
b
lo
b
(a
6
Ł>
6>
6>
t
C?
t.
&
6
6
k
fc
6p
(2)
Pre-
si Ivicultural
activity flow
Ve
(cfs)



0.00
0.3«/
0.97
/.fcV
S.H
3.87
5:35-
fe.sa,
?.o?
laas
9.o?
fc.?a,
V.ai
3M4
1-lH
0.3
-------
This page intentionally left  blank.
             VIII.151

-------
                                WORKSHEET VI .3

                     Sediment prediction worksheet summary

Subdrainage name tiorSfc  CfCfek      _ Date of analysis W Af /O
                                                 ~                   '
                                  PlttH
     Suspended Sediment Discharge

A.  Pre-si I vicu Itural  activity total  potential  suspended sediment
    discharge (total col. (4), wksht. VI. 1) (tons/yr)                 7. 1
B.  Post-si IvicuItural  activity total  potential  suspended sediment
    discharge (total  col.  (7), wksht.  VI.1) (due to streamfJow
    increases) (tons/yr)                                              O-o
C.  Maximum allowable potential  suspended sediment discharge (total
    col. (9), wksht. VI.1) (tons/yr)                                 3o.fe

D.  Potential introduced sediment sources:   (delivered)

    1.  Surface erosion (tons/yr)                 /7-7

    2.  Soil  mass movement (coarse) (tons/yr)
    3.  Median particle size (mm)                 /O
    4.  SoiI  mass movement—
          washload (silts and clays)  (tons/yr)
    Bed Ioad Discharge (Due to increased streamflow)

E.  Pre-siIvicuItural  activity potential  bedload discharge (tons/yr)   AT
F.  Post-si IvicuItural  activity potential  bedload discharge (due
    to increased streamflow)  (tons/yr)
    Total  Sediment and Stream Channel  Changes

G.  Sum of post-si IvicuItural  activity suspended sediment + bedload   ..  n
    discharge (other than introduced sources) (tons/yr)               |Q- /
                                                                   (sum B + F)

H.  Sum of total  introduced sediment (D)
       = (D.1  + D.2 + D.4)  (tons/yr)                                 tflQff. 7

I.  Total  increases in potential  suspended sediment discharge

    1.   (B + D.1  + D.4) - (A)  (tons/yr)

    2.   Comparison to selected suspended  sediment limits
        (1.1)  - (C)  (tons/yr)                                      +
                                    VIII.152

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                           WORKSHEET VI .3~continued
J.  Changes in sediment transport and/or channel change potential
    (from introduced sources and direct channel  impacts)

    1.   Total  post-si IvicuItural  activity soil  mass movement            ,,
        sources (coarse size only) (tons/yr)                          I\\Ł

    2.   Total  post-si IvicuItural  soil  mass movement sources (fine        .
        or wash load only) (tons/yr)                                    TV?

    3.   Particle size (median size of  coarse portion) (mm)              \Q

    4.   Post-si IvicuItural  activity bedload transport (F) (tons/yr) 	/./

    Potential  for change (check appropriate blank  below)

        Stream deposition   ^^

        Stream scour     	

        No change        	

K.  Total pre-siIvicuItural  activity potential  sediment discharge       Q
    (bedload + suspended load) (tons/yr)                               Q.5"
                                                                   (sum A  +  E)

L.  Total post-si IvicuItural activity potential  sediment discharge         .
    (all  sources + bedload  and suspended load)  (tons/yr)             g?30-T
                                                                   (sum G  +  H)

M.  Potential  increase in total sediment discharge due to proposed   -.• Q
    activity (tons/yr)                                              c*.\\-7
                                                              (subtract L - K)
                                    Vm.153

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                                      WORKSHEET VI.4

          Bed load transport-stream power relationship for  Worse CreelfC.  FVocoSBa Plavy
(1)
Water
surface
slope
S *
(ft/ft*
O.oaso
O.oos^
o.ooso
o.ooso
o.ooso
0.0050
o.ooso














(2)
Constant
(62.4)
K
(Ib/ft3)
W-f
43. «
«.*
62.*
W.f
63.V
«.»














(3)
Measured
stream
discharge
0
(cfs)
\o.s
3.0
7.0
5.0

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                                WORKSHEET VI .5

               Computations for step 21  (jerse
                                              (stream name)
                                             osed SilrfeuHujraJG  P

Changes in bed load transport-stream power due to channel  impacts

1.  Potential changes in channel dimensions

    a.  Bankful  stage width  (Wpre)   10      (wpost)   /-^

    b.  Bankful  stage depth  (Dpre)   O.b      (Dpost}  d.&
    c.  Water surface slope  (Spre)  O.Qfl?   (Spost)  O.OUSO

    d.  Bankful discharge    (Qepre* ^-^3     ^Bpost* °-^

where:  Qspre = 0.366 +1.33 log Apre + 0.05  log Spre - 0.056  (log Spre);

        where:  A = cross-sectional area  (a) x (b)   0-v)

                S = water surface slope (c)          0.0'Xf

        Calculate Qepost Us'n9 post-si IvicuItural A and S

           ^Bpost = 0.366 + 1.33 log Apos+ +0.05 log Spost

                    - 0.056 (log Spost)2

2.a.  Pre-siIvicuItural activity stream power calculation

                  Spre     62.4     QBpre
           ,„      (l.c)  x  (K)  x  (l.d)  .
                           ;?::,                   o-°)
2.b.  Post-si IvicuItural activity stream power calculation

                   spost    62-4    PBpost
           0)
               f = ^-L^.—=_~—-—^-i^- = \.v«*y\v«-ij\.u.*.*j ^ *
                            Wpost                   7T7\
                            (i .a)
3.   Calculate post-si IvicuItural activity bedload transport rate at bankful
    discharge, using post-si IvicuItural activity stream power
                                  VHI.155

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                                WORKSHEET VI.3

                     Sediment prediction worksheet summary

Subdrainage name Worse CWlcYfouis&J  SlluieJWl P\a\n\    Date of analysis
                                                  ~
     Suspended Sediment Discharge

A.  Pre-siIvicuItural  activity total  potential suspended sediment
    discharge (total col. (4), wksht. VI.1) (tons/yr)                  /.|

B.  Post-si IvicuItural  activity total potential suspended sediment
    discharge (total col. (7), wksht. VI.1) (due to streamflow
    increases) (tons/yr)

C.  Maximum allowable potential suspended sediment discharge (total
    col.  (9), wksht. VI.1) (tons/yr)

D.  Potential introduced sediment sources:  (delivered)

    1.  Surface erosion (tons/yr)                  /.o

    2.  Soil  mass movement (coarse) (tons/yr)      0	

    3.  Median particle size (mm)               	~~	
    4.  SoiI  mass movement—
          washload (silts and clays) (tons/yr)      0
    Bedload Discharge (Due to increased streamflow)

E.  Pre-siIvicuttura I  activity potential  bedload discharge (tons/yr)   /
-------
                           WORKSHEET V I . 3—cont i nued
J.  Changes in sediment transport antj/cr channel change potential
    (from introduced sources and direct channel  impacts)

    1.   Total  post-si IvicuItural activity soil  mass movement
        sources (coarse size only) (tons/yr)                            0

    2.   Total  post-si IvicuItural soil  mass movement sources (fine
        or wash load only) (tons/yr)                                     0

    3.   Particle size (median size of  coarse portion) (mm)             •—
    4.  Post-si I vicu Itural activity bedload transport (F) (tons/yr)    /.7

    Potential  for change (check appropriate blank below)

        Stream deposition _

        Stream scour      _

        No change          V

K.  Total  pre-si I vicu Itural  activity potential  sediment discharge
    (bedload + suspended  load) (tons/yr)
                                                                   (sum A + E)

L.  Total post-si I vicu Itural activity potential sediment discharge
    (all  sources + bedload and suspended load) (tons/yr)             o/O.b
                                                                   (sum G + H)

M.  Potential increase in total sediment discharge due to proposed
    activity (tons/yr)                                              _J_L_ _
                                                              (subtract L - K)
                                    Vin.157

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                                                        WORKSHEET V I I . 1



                                     Variation of solar azimuth and  angle with time of day
Time of day
(Daylight savings time)
?:00
10. '00
fl :00
II :30
U:00
ISU30
/ ;00
/ :30
a^oo
3US
,5:30
3 :00

Solar
angl e
30
43
54
S?
62.
45-
65
4s-
6 a.
60
SS
S^
^3
30
Shadow!/
length (S)
(ft)
/3ft 6
SS.8
s&l
5o.O
^.S"
37.3
37.3
37.3

-------
Ol
co
                                                                 WORKSHEET VI 1.2


                                                  Evaluation of downstream temperature Impacts
/.
S.
3.
V-
5.
6.
7
S.
Stream reach
flrea. 47

Area. S18
fBelou cimflucne«)
Area. Ł9

/W 30
f6a|ou confiuetwa)




^adjusted
*«•
?so

565"

741







^adjusted
8T(A./<'4'--»>,\»,
«/.3l

tf/X

aw







c
Surface
c4s
O.^f

0.3

O.^f








Subsurface
0(5
—

—

—







All/
°F
S.S

Q.\

IJ







&
•F
57.5"

S7.3

^.9

S-?. fl.





                    \J Łj _ Aadjusted x Hadjusted  x 0.000267   where Q is surface flow only.


                    2/                  °
                    - T from mixing ratio equation.

-------
                                 LITERATURE CITED

Maxwell, W. G., and F.  R.  Ward. 1976a. Photo       ponderosa pine  type; ponderosa pine and as-
  series  for quantifying  forest  residues  in  the:       sociated species type; lodgepole pine type USDA
  coastal  Douglas-fir-hemlock type;  coastal       For. Serv. Gen Tech. Rep. PNW-52.
  Douglas-fir-hardwood type. USDA For. Serv.
  Gen. Tech. Rep. PNW-51.                        ™  ,   ,   « T
                                                Pfankuch,  D. J. 1975. Stream reach inventory and
Maxwell, W. G., and F.  R.  Ward.  1976b. Photo       channel  stability evaluation. USDA For. Serv.,
  series  for quantifying  forest  residues  in  the:       Reg. 1, Missoula, Mont. 26 p.
                                         VIII.160

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                 Chapter IX

DISSOLVED OXYGEN  AND  ORGANIC
                MATTER
      this chapter was prepared by the following individuals:

                Stanley L. Ponce
                John B. Currier

-------
                           CONTENTS
                                                            Page

INTRODUCTION	   IX.l
DISCUSSION  	   IX.2
  OXYGEN SOLUBILITY IN FRESH WATER	   IX.2
  IMPORTANCE OF DISSOLVED OXYGEN TO FISH	   IX.2
  THE OXYGEN BALANCE IN A STREAM	   IX.4
  DISSOLVED OXYGEN AND LOGGING	   IX.8
     Water Temperature Increases  	   IX.8
     Logging Debris	   IX.8
  PREDICTING DISSOLVED OXYGEN DEFICITS,
   THE DO SAG METHOD	   IX.ll
     Predicting Components Of The DO Sag Method	   IX.13
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS	   IX.14
CONCLUSIONS 	   IX.15
LITERATURE CITED 	   IX.16
                              IX.ii

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                           LIST OF EQUATIONS




Number                                                                Page



IX.l.      S*(P)=S760-p    	   IX.2


DC.2.      P= 29.92 / exp (E/25,000)  	   IX.2


IX.3.      S(T) = 14.56 - 0.38163T + 0.0066366T2 - 0.0005227T3   	   IX.2


IX.4.      ADOm = DOm(i)-DOm(o)  	   IX.4


Bt.5.      D0m(i) = D0m(o)   	   IX.4


DC.6.      Substrate + 02 °rganism  » C02 + H20 + energy + other byproducts   IX.5


IX.7.      dD
          -Ł- = -K2D   	   IX.12


IX.8.      dL
          -7- = -KiL    	   IX.12
          at


DC.9.        dL   dD

          ~ dT = ~dt~   	  IX'12


IX.10.     dD
          -^- = KiL   	  IX.12



IX.11.     D =  KiLa  [exp (_Kjt) - exp (-K2t)] + Da exp (-K2t)    	  IX.12
               K2—Ki


IX.12.          Ki
          Dc = — La exp (-Kitc)   	  IX.12


IX.13.        K!      K2   f  Da (K2-Ki)"|                             TV
          tc= -_  T. In —  1-	^T	     	  IX.13
           c  K2-Ki    Li   L      KlLa  J


IX-14-     K2(T) = 1.016(T-20) [181.6 E - 1657 S + 20.87]    	  IX.13


IX.15,     E =  (S)  (u) (g)    	  IX.13


DC-16-     Kim = 0.796 [1.126(T-ao)K1(ao)l; 2° < T < 15° C	  ix.13


K'17-     K1(T) = 1.000 [1.047(T-20)K1(2o)];  15° < T < 32° C	  IX.13


DC 18                      (T-20)
          K1(T)= 1.728 [0.985     K1(20)); 32° < T < 40° C	  IX.13


K.19.     La(T)=La(20)[1.0 + 0.0033(T-20)];20
-------
                             LIST OF FIGURES



Number                                                                 Page

IX. 1.—Relationship between temperature, pressure (elevation), and dissolved
        oxygen	  IX.3
IX.2.—Hypothetical section of stream channel to be considered in the dissolved
        oxygen mass balance	  IX.5
IX.3.—Sources and sinks  of  dissolved  oxygen in a mountain stream under
        natural  conditions (after Ponce 1974b)	  IX.6
IX.4.—The biochemical oxygen demand process in a  mountain stream (after
        Ponce 1974b)	  IX.7
IX.5.—Surface dissolved oxygen levels (mean and range) taken  twice weekly in
        the clearcut watershed (Needle Branch) and control watershed (Flynn
        Creek) during the year of timber harvest  (1966)	  IX.10
IX.6.—Intragravel dissolved oxygen  levels in the  clearcut watershed (Needle
        Branch) from December 1965 to May 1966 (before logging)	  IX.11
IX.7.—The dissolved oxygen sag	  IX.12
                                    IX.iv

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                              LIST OF TABLES
Number                                                                 Page

IX.1.—Mean cumulative BOD in milligrams of (Vg (dry weight) by Douglas-fir
        needles and twigs, western hemlock needles, and red alder leaves in
        stream water at 20° C  (Ponce 1974a)	   IX.9
IX.2.—Mean cumulative BOD in milligrams of (Vg (dry weight) by Douglas-fir,
        western hemlock, and red alder leaves under conditions of temperature
        fluctuation (Ponce 1974a) 	   IX.9
IX.3.—K1(2o) and La (2o) values for selected tree species and materials	   IX.13
                                     IX.v

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                                      INTRODUCTION
  The  dissolved  oxygen  (DO)  concentration  in
small,  forest streams  strongly influences the
character  and  productivity  of  the  aquatic
ecosystem. Fish and other aquatic organisms need
dissolved oxygen  to survive, grow, and develop.
  Silvicultural  activities may influence the dis-
solved oxygen concentration of a stream draining a
logged  area. If  timber  harvesting exposes the
stream  to  direct  solar  radiation,  the  water
temperature will  increase, as discussed in chapter
VII, resulting in a decrease in the saturation con-
centration of DO  in the water. In addition, if large
quantities of organic  debris are allowed to enter
and remain in the stream channel over an extended
period, they may contribute to decreased DO levels
by: (1) forming debris ponds,  which  enhance
heating of water and reduce the reaeration rate; (2)
releasing dissolved materials,  such  as  sugars,
nutrients,  and  phenolics, which are readily ox-
idized  by  microorganisms;  and (3)  forming   a
benthic mat  that can inhibit the flow of DO into
the intragravel  water.
  It is not possible to accurately predict the impact
of silvicultural activities on the DO concentration
of forest streams. The physicochemical properties of
oxygen solubility, the pool and riffle  nature  of
mountain streams, and the non-point source pollu-
tants  affecting DO  concentration make  such
prediction  very difficult.  However, several
mathematical models  have been proposed for use
with forest  streams. In general, these models are
merely extensions of methods developed for quies-
cent waters,  such as rivers and  lakes, and most
have met with only limited success. One notable
exception is a model by Berry (1975)  specifically
developed to predict the impact  of logging debris
on  dissolved oxygen  content  in  small forest
streams. This model can be used to predict  DO
concentrations  in the  surface water of a stream
where  DO content  has a critical bearing on  a
resource management decision. However, if only a
rough estimate of the DO concentration in the sur-
face water is required, the Streeter and Phelps
(1925) DO sag method may be used. Little work has
been done concerning oxygen dynamics in the in-
tragravel /one of a stream. As a result, there are no
models  available to predict  DO changes in  the
streambed gravels following logging.
  Although accurate prediction may not be possi-
ble, a clear understanding of oxygen dynamics in a
stream  is essential  to identify  silvicultural  ac-
tivities that will adversely affect the DO concentra-
tion in a small forest stream. As a result, informa-
tion on oxygen solubility, the dissolved oxygen
balance, dissolved oxygen and logging, and land
use practices to protect and maintain  the oxygen
concentration in a forest stream is explained prior
to discussion of the Streeter-Phelps model. Evalua-
tion of the impacts of silvicultural activities on  DO
concentrations is essential in identifying potential
impacts on the fishery resource of a DO reduction
caused by timber harvesting.
                                              IX. 1

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                                        DISCUSSION
 OXYGEN SOLUBILITY IN FRESH WATER


  Although  free oxygen is  abundant  in  the  at-
mosphere (20.9 percent by weight), it is relatively
insoluble in water.  The saturation concentration
varies between 14.6  mg/l (ppm)1 at 32°  F (0° C) to
7.6 mg/1 at 86° F (30° C) under 29.92 inches of Mer-
cury  (760  mm) atmospheric pressure. In  fresh
water, oxygen solubility, or  saturation  concentra-
tion, is determined by atmospheric  pressure and
the temperature of water. Figure IX.1 illustrates
the relationship between temperature, pressure
(elevation), and concentration of dissolved oxygen.
  Atmospheric pressure. — The effect of pressure
is described by Henry's law, which states that  the
solubility of a gas in a liquid is  directly  propor-
tional to the pressure of the gas above the liquid. As
the atmospheric pressure (partial pressure of  ox-
ygen) increases, there is a proportional  increase in
the water's capacity to hold oxygen. The pressure
effect can be calculated by equation  IX. 1:
„     Qp-p
 

~ & 760-p (IX.l) where: S*p) = the oxygen solubility in mg/l at at- mospheric pressure P in inches (mm) of mercury, S = the oxygen solubility at 29.92 inches (760 mm) of mercury, and p = the pressure (inches or mm) of saturated water vapor at the temperature of the water (American Public Health Associa- tion, Inc. 1971). At elevations below 3,000 feet (900 m) m.s.l. and temperatures below 77° F (25° C), p can be con- sidered negligible. If the elevation (E in feet) is known, an approximate value of P can be calculated by: P = 29.92 / exp (E/25,000) (IX.2.) 'In fresh water (total dissolved solids <7,000 mg/l) 1 mg/l = I ppm (Hem 1970). As a result, the English unit of concentra- tion will not be given throughout the balance of this chapter since it is equivalent to the mg/l of concentration. Water temperature. — The solubility of oxygen in water is inversely proportional to water temperature. This is important because some silvicultural activities expose the stream to direct solar radiation, resulting in an increase in the stream water temperature (chapter VII). As the water temperature increases, its capacity to hold oxygen decreases. The temperature effect can be calculated by: S(T) = 14.56 - 0.38163T + 0.0066366T2 - 0.00005227T3 (IX.3) where: S(T) = the solubility of oxygen (mg/l) in water of a given temperature, and T = the temperature in °C. IMPORTANCE OF DISSOLVED OXYGEN TO FISH Adequate levels of DO in the surface and in- tragravel water are essential for survival offish. An "adequate level" of DO is a vague term and varies with the species and age of the fish, prior ac- climatization, temperature of the water, and con- centration of other substances in the water (McKee and Wolf 1963). However, fishery biologists often use the following "rule of thumb" for minimum DO concentrations for freshwater biota: 5 mg/l for warm water species, declining to a lower limit of 4 mg/l for short periods, provided that the water quality is favorable in all other respects; and no less than 6 mg/l, or 7 mg/l during spawning times, for cold water species. Fish often are exposed to DO concentrations well below 5 mg/l for prolonged periods. DO concentra- tions between 5 and 2.5 mgA are generally con- sidered sublethal to fish. Under such conditions, fish experience an oxygen stress, and if the ex- posure is extended, their activity, growth, and reproduction may be reduced. Several responses to oxygen deficiencies by fish within the surface water and by fish eggs and embryos in the intragravel water have been reported. Shellford and Allee (1913) studied the avoidance reaction of 16 species of fish to different IX.2


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                                                         ELEVATION IN THOUSANDS OF FEET
                                    10"   12°  14°   16°
                                    TEMPERATURE,°C
             Figure IX.1.—Relationship between temperature, pressure (elevation), and dissolved oxygen.
concentrations of oxygen. They reported a definite
effort by all the fish to avoid water substantially
deficient in oxygen. Jones (1952) ran a similar ex-
periment with stickleback, minnows, and trout fry.
At  temperatures near 68°  F  (20° C), all three
species  reacted  violently and retreated  rapidly
when they swam into water containing 0.5 to 1.0
mg/1 of DO.  At a concentration of 3.5 mg/1, the
reaction  was again  one of rejection  but much
slower.  Whitmore and others (1960)  conducted
avoidance tests  with juvenile  chinook and  coho
salmon, large mouth bass, and bluegill. They found
all four species markedly avoided water containing
less than 4.5 mg/1 of DO; some coho avoided con-
centrations of 6 mg/1.

  Davison  and others (1959), studying dissolved
oxygen requirements of cold water fishes, reported
that at a temperature of 64° F (18° C), young coho
salmon survived for 30 days at a DO level  of 2.0
mg/1. During this period the fish ate little and lost
weight. At a higher DO level, near 3.0 mg/1, the fish
ate more food and gained weight.  However, this
gain was much  less than that of similar fish in
                                               IX.3

-------
oxygen-saturated water.  Herrmann and others
(1962)  further examined the influence of oxygen
concentration on growth and food consumption of
juvenile coho salmon. They found that at 68° F
(20° C), both growth and food consumption over a
prolonged period declined gradually as the oxygen
level dropped from  8.3  to  about  5.5  mg/1. The
decline of each was rapid  as the oxygen  level
dropped from about  5 to 1.8 mg/1, and fish often
died at DO levels below  1.0 mg/1. The fish ate very
little and lost weight at oxygen levels at or below 2
mg/1.
  These studies indicate that fish attempt to avoid
areas significantly deficient in oxygen, and that
when fish are exposed to such water for a prolonged
period, their growth and  food consumption rates
decrease.
  The  value of high oxygen levels in the intragravel
water is often overlooked. However, it is critical for
Pacific Coast salmonoids, as well as other sport and
commercial fish that spawn in small forest streams.
The salmonoid species deposit their eggs 10 to 12
inches (25 to 30 cm) deep into the stream gravels.
The eggs  hatch, and the embryos develop for  ap-
proximately 3 months before the fry emerge into
the surface water (Lantz 1971). Continuously high
oxygen levels during embryo development are very
important. If oxygen becomes deficient,  the per-
cent egg survival, rate of embryo development, and
quality of fish produced may decrease significantly.
   Shumway and others (1964) examined the in-
 fluence of oxygen  concentration and water move-
 ment  on  the growth of steelhead trout and coho
 salmon embryos.  In their  experiment,  embryos
 raised from fertilization to hatching were exposed
 to different concentrations of DO ranging from 2.5
 to 11.5 mg/1 and water velocities ranging from 2 to
 138 in/hr (3 to 350 cm/hr) under a near constant
 temperature of 50° F (10° C). They found that fry
 produced from embryos raised at oxygen levels of
 less than 4.0 mg/1 hatched later and were smaller at
 hatching  than  fry from embryos raised at oxygen
 levels  near saturation.  They also  reported that
 reduced water  velocities affected the fry in much
 the same  manner  as  reduced oxygen levels,
 although  the effect was not  as pronounced.
   Garside (1966) conducted a similar experiment
 which  examined  the   effects  of  oxygen  and
 temperature on brook and rainbow trout embryo
 development. The embryos of each species were ex-
 posed  to  oxygen concentrations of 2.5,  3.5,  and
 10 mg/1 at each of four temperatures — 36° F (2.5°
 C), 41° F (5.0° C),  45° F (7.5° C), and 50° F (10° C)
— from the time  of fertilization to late develop-
ment.  The development  rate  slowed  and the
hatching period increased for both species of fish as
temperature  levels increased and  oxygen levels
declined.
  THE OXYGEN BALANCE IN A STREAM
  The oxygen concentration in a stream is deter-
mined by the addition and depletion of dissolved
oxygen by biological and physical processes. Under
undisturbed conditions, a forest stream is in a state
of oxygen balance. Aquatic animals and decom-
position agents continuously withdraw free oxygen
while, at the same time, oxygen is supplied inter-
mittently by green plants during daylight, and con-
tinuously by  direct  absorption from  the at-
mosphere.
  The oxygen  system within a  stream may be
described using the mass balance approach. The
change in  mass of DO  (ADOm)  within a fixed
volume of stream is equated to the inputs (DO m(i))
minus the outputs (D0m(o)) of oxygen and may be
expressed as:
            ADOm = DO
'm(i) •
     DO
                                m(o)
(IX.4)
If an oxygen balance exists, there will be no net
change in the oxygen mass within the volume, and
the equation may be reduced to:
                D0m(i) = DO
    m(o)
                 (K.5)
  The oxygen balance  of a section of mountain
stream (fig. IX.2) under undisturbed conditions is
illustrated diagrammatically in figure IX.3. The
size  of the arrows between components indicates
the magnitude of oxygen transfer.
  A  mountain stream is replenished with oxygen
from three sources: the direct absorption at its sur-
face,  the photosynthetic process of green aquatic
plants, and, to a minor extent, the influent ground
water.

  Surface water is supplied with oxygen primarily
by  direct absorption (reaeration)  from the  at-
mosphere. The reaeration rate is a function of the
DO concentration at the surface, while the disper-
sion of oxygen thoughout the water is controlled by
simple molecular diffusion and mass transfer. In
                                              IX.4

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                                Stream Bank
   Stream. Bank
 Figure IX.2.—Hypothetical section of stream channel to be
  considered in the dissolved oxygen mass balance.
general, the rate of reaeration in a still water body,
such as a pond or lake, is relatively slow. However,
forest  streams often have  steep  gradients  that
result in turbulence, which  produces vertical and
horizontal mixing as well as oxygen entrainment,
all of which greatly increase the reaeration rate.
   During  daylight, plankton  and algae that are
often present  in quiet pools photosynthesize and
produce free oxygen as a byproduct. In large, low
gradient  streams  or  lakes, photosynthesis  may
serve as a major source of oxygen; however, in small
forest streams, it  is generally  only a very minor
source of oxygen (Camp 1965).
   The intragravel water is  supplied with oxygen
primarily by mass transfer and diffusion from the
overlying surface water. The rate of this transfer
and diffusion is relatively slow, because the mixing
agents present in the surface water are inhibited in
the intragravel water. Water velocity through the
intragravel layer is much lower than the surface
layer: 1 to 2 in/hr (2 to 5 cm/ hr) compared to 20 to
60 in/sec (50 to 150 cm/sec)  (Narver 1971).

  A second,  and generally very minor, input of ox-
ygen into the intragravel water is oxygen carried in
by influent  ground water (Vaux  1968). Sheridan
(1962) found that oxygen input by ground water in
pink salmon streams in southeast Alaska was very
small. He concluded that the major intragravel ox-
ygen source was direct diffusion from the surface
layer.
  The predominant dissolved oxygen sink in an un-
polluted mountain stream, both in the surface and
intragravel water, is  biochemical oxygen  demand
(BOD). DO will be lost to a lesser extent to respira-
tion by larger  aquatic life and plants, to the at-
mosphere by direct diffusion — if the stream is in a
state of oxygen supersaturation — and to effluent
ground water flow.
  Biochemical  oxygen  demand  imposes  the
greatest drain on a stream's DO supply. The BOD
process  in a  mountain  stream  is  illustrated
diagrammatically in  figure IX.4. The  decomposi-
tion agents (decomposers)  may be  separated  into
two classes:  dispersed and  attached  organisms.
Dispersed organisms flow freely within  the stream;
attached organisms remain stationary,  attached to
rocks and other fixed objects. Both exert an oxygen
demand.  In  a small forest  stream,  where  the
gradient is high and the flow turbulent, dispersed
organisms generally  predominate.  In streams
where the gradient is low and there are a number of
quiescent pools,  attached organisms may exert a
significant demand.  In general, the decomposers
are  comprised  primarily of  bacteria, protozoa,
fungi, and, to  a lesser extent, larger aquatic life
(insects and fish).
  The substrate, or food source, is composed of
suspended material (finely divided plant material),
dissolved material  (nutrients and  simple sugars
leached from plant material), and benthic deposits
(organic material that has settled  to  the  stream
bottom).
  Once the material  is ingested, the assimilative
process is one of wet  oxidation within  the decom-
posers. This process may be expressed by the fol-
lowing reaction:
Substrate + 02
                          » C02 + H2O
                                         (IX.6)
            + energy + other byproducts
In this process, the decomposers utilize oxygen to
break down the substrate to produce carbon diox-
ide, water, energy for growth and reproduction, and
other byproducts.
  Larger aquatic life  impose another sink on  a
stream's dissolved  oxygen  supply  (fig.  DC.3).
Although a mountain stream may appear to be
relatively free of larger  aquatic life, it generally
supports a multitude of organisms, such as snails,
                                              DC.5

-------
Dissolved Oxygen in
Inflow Stream Water


S
                            Atmospheric
                              Oxygen
                          I   I
                     Sub-Saturation
                           Green Plant
                          Photosynthesis
                                   Super-Saturation
                        Dissolved Oxygen
                        in Outflow Water
 Dissolved Oxygen
 in Outflow Water
 Dissolved Oxygen
      in Inflow
  Intragravel Water
Dissolved Oxygen
    in Outflow
 Intragravel Water
!u
              Aquatic
              Animal
             Respiration
                                         I
                      Dissolved Oxygen in
                       Intragravel Water
                             Influ
        uent
        ;
        I
                                         i
                                     Effluent
    Dissolved Oxygen
    in Ground Water
                        Biochemical
                      Oxygen Demand
                                                          1
                                                          JL
Green Plant
Respiration
Figure IX.3.—Sources and sinks of dissolved oxygen in a mountain stream under undisturbed conditions
 (Ponce 1974b).
                              IX.6

-------
                     Agents of Decomposition
          Dispersed
         Organisms
                          Attached
                         Organisms
  Oxygen
  Supply
   Energy for
   Organisms


Organic
Substrate
^


«•
-M
Suspended
Material

Dissolved
Material

Benthic
Deposits
                      Oxidative Assimilation
Carbon
Dioxide
Water


^m

Other
Byproducts
Substrate + O?	organism	».CO2 + H2O + energy + other byproducts
  Figure IX.4.—The biochemical oxygen demand process in a mountain stream (Ponce 1974b).
                              IX.7

-------
insect  nymphs,  crayfish, and fish.  All these
organisms  require oxygen. The rate  of  oxygen
removal by these organisms  is a function of the
species present and their environment.
  The  oxygen balance  is an important water
quality concept. Alteration of any of the sources or
sinks will  result in a new oxygen equilibrium con-
centration and may  have a pronounced effect on
the aquatic life present.
   DISSOLVED OXYGEN AND LOGGING


  Timber harvesting can  have a substantial im-
pact on the DO balance in upland streams, par-
ticularly if logging debris are allowed to enter and
remain  in the stream channel. Timber harvesting
may affect dissolved  oxygen  concentrations in
small forest streams in several ways.


         Water Temperature Increases


  Logging  may alter the temperature regime in a
small stream  (chapter  VII). Brown and Krygier
(1970) evaluated the effect of two different methods
of clearcutting on stream temperature in Oregon's
Coastal Range. They found that the maximum
temperature increased from 57° to 85° F (13.9° to
29.4° C) on the completely clearcut watershed 1
year after cutting. In terms of oxygen decrease, due
only to temperature fluctuation,  the saturation
concentration  of oxygen would have  dropped 28
percent (from  10.3 to 7.4 mg/1). Temperature levels
in the stream draining the watershed, which was
patchcut with vegetation buffer strips left along the
channel, showed no significant change in stream
temperature due to timber harvesting, and main-
tained DO  levels near those of the control stream.
  Similar trends have  been observed in the Ap-
palachian  highlands.  Eschner  and  Larmoyeux
(1963) report that, prior to treatment, there was lit-
tle difference  between  water temperatures of the
control watershed and the watershed to be entirely
clearcut. However, the first year following cutting,
the maximum water temperature measured on the
clearcut watershed was 75° F (23° C), 20° F (11°
C) greater than the maximum recorded on the con-
trol  stream.  In  terms  of  DO solubility  in the
stream,  the saturation  concentration  would have
dropped 19 percent (9.0 to 7.3 mg/1).
                Logging Debris


  Slash is a byproduct of logging. It is composed of
limbs, branches, needles, and leaves  of trees. This
debris, along with forest  floor  material, may  ac-
cumulate in the stream channel, particularly if log
yarding across the channel is permitted. Once this
organic  material enters the  channel, it may
adversely affect the DO concentration  in several
ways: (1) by exerting a high BOD, (2)  by restricting
flow and reducing reaeration, and (3)  by  accen-
tuating water temperature increases.
  The oxygen demand (BOD) by plant matter has
been  well  documented.  Plant  materials contain
simple sugars and other nutrients that are readily
leached  in  water (Currier  1974,  Ponce 1974b).
Microorganisms  consume  these leached con-
stituents and,  in turn,  exert a demand on the
stream's oxygen supply.  This demand for oxygen
may continue for a  relatively long period.
  Chase  and Ferullo (1957) studied  the effect of
autumn leaf fall on the oxygen concentration  in
lakes  and streams in the eastern  United States.
After  1 year, maple leaves demanded about 750 mg
of O^/g of initial dry weight, while oak leaves and
pine needles required about 125 mg of 02/g of in-
itial dry weight. The oxygen uptake was relatively
rapid: by day 100 maple had achieved about 70 per-
cent,  and oak and pine 55 percent, of the demand
exerted in 1 year.
  Slack and Feltz (1968) examined the effect of leaf
fall on quality changes in a small Virginia stream.
They  reported no significant change in oxygen con-
sumption as the leaf fall rate increased  from 0 to
0.05 Ib/ft2/day  (0 to 2 g/m2/day). As the rate  in-
creased from 0.05 to 0.28 Ib/ft2/day (2 to 12 g/m2/-
day),  however,  there was a corresponding drop in
DO from 8 mg/1 to less than 1 mgA. Upon natural
flushing of  the  stream by  a storm,  the DO
responded  by  climbing  to  near saturation con-
centration (11 mg/1).

  Ponce (1974a) determined the BOD of Douglas-
fir needles and twigs, western hemlock needles, and
red alder leaves in stream water. The oxygen de-
mand by these materials was measured for 90 days
at 68° F (20° C) and for 5 days under the condition
of temperature fluctuation similar  to  patterns
observed in  clearcut watersheds  of  the Oregon
Coastal Range.  Selected results of Ponce's work are
presented in tables  IX.l  and IX.2. It is apparent
that this material exerts a substantial oxygen  de-
mand: 101, 178, and 273 mg of O^g for Douglas-fir,
                                              IX.8

-------
Table IX.1.—Mean1 cumulative BOD in milligrams of Oz/g (dry weight) by Douglas-fir needles and twigs, western
               hemlock needles, and red alder leaves in stream water at 20° C (Ponce 1974a)
Vegetation
type

Douglas-firneedles
Western hemlock needles
Red alder leaves
Douglas-fir twigs
5


63
32
79
25
10


76
88
124
47
Days
20


97
130
169
75
45
"Wn
J2/Q 	
99
169
239
100
60


96
176
260
—
90


101
178
273
—
  'The mean of four replications for each species
 Table IX.2.—Mean1 cumulative BOD in milligrams of 02/g (dry weight) by Douglas-fir, western hemlock, and red alder
                     leaves under conditions of temperature fluctuation (Ponce 1974a)
Vegetation
type


Douglas-fir needles
Western hemlock needles
Red alder leaves
1


46
24
72
2


62
55
131
Days
3
.... 4 r\ i

124
81
124
4


175
92
207
5


190
97
237
   1The mean of three replications for each species.
western hemlock,  and  red  alder  leaves, respec-
tively, over 90  days; and  100 mg  of  O^g for
Douglas-fir twigs over 45 days at 20° C. This de-
mand is exerted relatively rapidly with 96, 73, and
62 percent of the 90-day  demand achieved in 20
days for Douglas-fir, western hemlock,  and  red
alder leaves, respectively. When the temperature
fluctuated, the oxygen demand increased by a fac-
tor of 3 for each leaf type over the 5-day test period.

  The toxicity of the leachate extracted from each
of these vegetative species was determined on gup-
pies and steelhead trout fry. The concentration of
leachate needed to produce toxic effects was so
high that  oxygen  depletion probably would  be
responsible for death long before the leachate ef-
fect would.

  Hall and Lantz (1969) reported the effects of log-
ging on habitat of coho salmon and cutthroat trout
in  coastal streams of Oregon.  Two small
watersheds were studied, one completely clearcut,
the other  patchcut  with buffer strips. They were
compared  with a third watershed that served as a
control. Felling on the clearcut watershed began in
the spring. Timber was felled along the stream, and
logs were yarded uphill by cable across the stream
to landings. This resulted in the accumulation of
considerable quantity of debris in  the channel,
which restricted flow and formed pools. The large
material remained in the channel throughout the
summer. In early fall, the channel was cleared of
the large material to permit free flow.
  DO concentration was substantially reduced in
surface  and intragravel waters of  the clearcut
watershed (figs. IX.5 and IX.6). The DO reduction
was noted first in the intragravel water, after felling
began along the stream. A layer of debris on the
gravel and ponding of the surface water caused a
substantial decrease in the rate of oxygen transfer
from the  surface to  the intragravel  water. This
decrease, coupled with an oxygen demand by the
decomposing debris, caused a rapid decline in DO
in the intragravel water. DO concentrations in the
surface water from late spring through most of the
summer were too low to support salmon and trout
in one-third  of the  streams   available to  the
salmonoids; juvenile  coho salmon placed in  live-
boxes there survived less than 40 minutes.  The
lowest  oxygen concentration reported, 0.6  mg/1,
was observed in  a pool resulting from a dam com-
posed of debris. During  this period,  oxygen  con-
centration of the control stream and the stream
                                               IX.9

-------
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0 WEIR 305 610 915 1830
                          DISTANCE UPSTREAM FROM WEIR  (meters)
         Figure IX.5.—Surface dissolved oxygen  levels (mean and range) taken twice weekly in the clearcut
           watershed (Needle Branch) and control watershed (Flynn Creek) during the year of timber harvest
           (1966). Sampling on Needle Branch occurred at 500 feet (152 m) in the area accessible to salmon and
           6,004 feet (1,830 m) (upper edge of clearcut). Samples from Flynn Creek were taken only at the weir (Hall
           and Lantz 1969).
draining the patchcut watershed remained at near
saturation  levels.  Upon removal of large debris
from the channel and establishment of free-flowing
conditions, the DO concentration rapidly returned
to near pre-logging conditions in the surface water.
Intragravel  oxygen  concentrations,  however,
remained about 3.0 mg/1 lower than the pre-logging
concentrations for the next 2 years, and continued
to decline over the next 4 years to levels less than
2.0 mg/1 at several locations.
  Although a portion of the intragravel DO decline
was attributed to long-term BOD by organic mat-
ter that intruded the gravel, it was concluded the
major  cause  for  the prolonged reduction  was
                                               IX. 10

-------
restriction of water flow through the gravel due to
sedimentation  in  the gravel  bed. Garvin (1974)
found that, in  the absence of sedimentation, log-
ging debris intrusion into streambeds resulted in a
large, but short-term, reduction of DO concentra-
tion in  the gravel. Within 6 months, DO levels
returned to almost normal.
 During  this  period, winter freshets provide the
 streams the energy to flush the material through
 the system. However, if the material is deposited
 between early spring and late  summer, serious ox-
 ygen  deficit is  much  more  likely.  During  this
 period, the streams are generally at low flow and do
 not have sufficient energy to transport the debris.
  It is apparent that logging debris may be respon-
sible for severe oxygen deficits within small forest
streams. However, it should be noted that the pol-
lution  impact  of  this material,  particularly the
finely divided  debris, depends not only on the
amount that enters the stream, but also the season
it enters the stream. Debris deposited in an Oregon
Coastal Range  stream between early fall and late
winter generally caused only minor oxygen deficit.
    PREDICTING DISSOLVED OXYGEN
     DEFICITS, THE DO SAG METHOD


  Berry  (1975)  developed  a working computer
model to predict the impact of logging debris on
dissolved  oxygen  concentrations  in small  forest
streams. Since this model appears to yield reliable
results, it can be used to predict DO concentration
12-
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I I
D 775 SURFACE
                                         SAMPLING STATIONS
         Figure  IX.6.—Intragravel dissolved oxygen levels in the clearcut watershed (Needle  Branch) from
          December 1965 to May 1966 (before logging). (All standpipes in Needle Branch were removed during
          logging; the six for which data are shown were replaced in their previous locations). Surface dissolved
          oxygen levels are shown for comparison (Hall and Lantz 1969).
                                              IX. 11

-------
for  resource management decisions. However,  if
only a coarse estimate of the oxygen deficiency is
required, it may be obtained by using the DO sag
method developed by Streeter and Phelps (1925).
The numerous  limitations  associated with this
method that greatly affect the  accuracy of the
prediction will be noted later.
  The DO sag concept is illustrated in figure DC.7.
It is assumed that the rate change in oxygen deficit
is governed by two independent reactions which oc-
cur simultaneously: reaeration and biochemical ox-
ygen demand (depletion). Each of these processes,
in turn, may be described by  a differential equa-
tion.
 Q.
 g 10
 0
 2
 O
 U-
   20
                1   1   '    I"   I
                DISSOLVED
                OXYGEN SAG •
     /I   I  .I   I    I    I   I    I
 20
 10 1
                                        10
                   TIME, days
 Figure IX.7—The dissolved oxygen sag.
  In the reaeratation equation, it is assumed that
 rate of oxygen absorption by the water is propor-
 tional to the oxygen deficit in the water. This rela-
 tion may be expressed as:
                  ar=
(DC.7)
where:
  D   =  the oxygen deficit in mg/1
  t   =  time in days, and
  K2  =  is the reaeration constant (base  e)  in
         units of I/day.
  In the depletion equation, it is assumed that the
rate of biochemical oxygen demand (BOD) due to
          biochemical oxidation  is  proportional  to the
          amount of BOD present. This may be expressed as:
                                -   KT
                            dt  ~ ~KlL
                                         (IX.8)
where:
  L   =  the BOD concentration in mg of (Vg,
  Ki  =  the BOD rate coefficient (base e) in units
         of I/day, and
  t   =  is as  previously defined.
  Equation IX.8 also may be expressed in terms of
oxygen deficit, D.  Since BOD concentration is
measured in terms of the quantity of oxygen con-
sumed, it follows that the rate change in BOD is
equal to  the rate of oxygen depletion.  The rate of
oxygen depletion may be expressed as the rate
change in oxygen deficit:
                                                                      dt
                                   dD
                                    dt
                                                                                           (IX.9)
Substituting equation IX.8 in IX.9 yields equation
IX.10:
                            dD
                            dt
                                                                         = K,L
                                                                                          (IX.10)
          Equations IX.7 and DC. 10 may be combined and
          solved for D, which enables the calculation of ox-
          ygen deficit at any given time, resulting in equation
          IX. 11:
 D =    ?L- [exp (-K,t) - exp (-K2t)]
      K2-Ki
       + Da exp (-K2t)
                                                  (IX.ll)
where:
La and Da are, respectively, the initial BOD con-
centration and initial oxygen saturation deficit in
units of milligrams of Oz/1 at time (t) equal to 0,
exp is  the base  of natural logarithms,  and the
remaining terms are as previously defined. Equa-
tion DC. 11 is commonly referred to as the Streeter-
Phelps  equation,  and may be used to predict any
point on the dissolved oxygen sag curve (fig. DC.7).
   Of particular interest is the point of maximum
deficit,  Dc (mg of O2/1) — the lowest point in the
DO sag curve  — and the time it occurs,  tc (days).
The point of maximum deficit may be calculated
by equation IX. 12 developed by Fair (1939):
                        Ki
                   Dc =   ~La exp (-
                                        (DC.12)
                                             DC. 12

-------
The critical time,  tc, is obtained  from equation
IX. 13 developed by Fair (1939):
      Ki
tc-K,-Ki
ln
           Da(K2-
                             (K2-Ki)"|
                              KiLa   J
                          (IX.13)
All terms  in  equations IX. 12 and IX.13 are as
previously  defined.


Predicting Components Of The DO Sag Method

  Although the DO sag method appears to be sim-
ple to apply, it is difficult to obtain reliable results
because of the lack of accurate values for Ki, Kz,
and La. Berry (1975) suggests the following equa-
tions to predict  these components.

  The reaeration rate constant. — The reaera-
tion rate constant can be predicted with equation
IX.14 developed by Holtje (1971):
                    fT—201
        K2(T) = 1.016     [181.6 E
               - 1657 S + 20.87]
                         (IX.14)
 where:
  K2(T)= the reaeration rate constant (I/day) at the
         water temperature T (°C),
  E  = energy of dissipation (ftVsec3 or mVsec3),
         and
  S  = the average channel slope (ft/ft or m/m).

The energy of dissipation can be calculated by:
                E =  (S)(U)(g)          (IX.15)

where:
  U  =  the average velocity (ft/sec or m/sec), and
  g   =  the  gravitational  acceleration  constant
         (32.2 ft/sec2 or 980 cm/sec2).
                                       The  leachate BOD  rate constant.  —  The
                                     leachate BOD rate constant, KI(T) (liter/day), can
                                     be determined by the set of equations developed by
                                     Zanoni (1967):
                                           K1(T) = 0.796 [1.126(T-20)K1(20)];
                                                  2° < T < 15° C

                                           K1(T) = 1.000 [1.047(T-20)K1(20)];
                                                  15° 
-------
             APPLICATIONS, LIMITATIONS, AND PRECAUTIONS
  The applications of the DO  sag method have
been discussed earlier. However, the  method has
several important limiting factors. The oxygen sag
method does not account for the following:
  1. The continuous redistribution of both the
    BOD and oxygen by the effect of longitudinal
    dispersion.
  2. Changes in channel configuration that alter
    the characteristics of surface turbulence and
    the reaeration rate, K2.
  3. Diurnal variation in oxygen content and water
    temperature.
4. The variation of Ki over time.
5. The removal of oxygen from the water by dif-
   fusion into the intragravel layer.
6. The  addition of BOD below the point of
   reference.
7. The effect of suspended and dissolved sub-
   stances on the rate of diffusion of oxygen from
   the surface into the main body of the stream.
8. Nitrogenous  BOD (the method  assumes
   nitrogenous  BOD does not occur).
9. Ponding.
                                           IX. 14

-------
                                       CONCLUSIONS
  Changes  in  dissolved oxygen  concentration in
streams  resulting  from  silvicultural  activities
usually can be  linked to changes in  stream
temperature  and  introduced  organic  debris.
Control practices and abatement goals that meet
temperature  and  sediment standards  will  also
minimize the reduction of dissolved oxygen.
  Introduced organic  matter may contribute ad-
ditional stress on dissolved oxygen concentration
beyond  that  produced  by increased  water
temperature. Primarily, the magnitude of the im-
pact of organic matter on dissolved oxygen  in-
creases with:
  1.  The amount and type of organic debris enter-
     ing the stream either  directly  or indirectly
     through runoff;
  2.  The extent  to which the  debris dams the
     stream  course and produces pools,  thus
     facilitating heating and reduction of reaera-
     tion; and
  3.  The length of time the debris remains in the
     stream water.

  Steep slopes near the stream  channel increase
the probability of debris washoff, and a decrease in
the stream channel gradient reduces the rate of
reaeration.
  Introduction  of  solid organic  debris  during
silvicultural activities  can  be  minimized  or
eliminated. Finer organic particles normally will
enter a stream along  with the surface eroded
materials. For organic material to enter the stream
via surface  erosion in sufficient  quantity  to
adversely affect the aquatic ecosystem, the quan-
tity of eroded soils would have to be so large that it
would present a problem in itself, overshadowing
any  deterioration of water  quality  due to  the
organic  matter component.
  Large debris can be prevented from entering the
stream by felling trees away from the stream, by
avoiding the  stream in  all  skidding  operations,
and/or by leaving an adequate streamside  zone.
Froehlich (1976) found accelerated debris loading
through logging to be most strongly related to the
timber  felling  process.  Conventional felling
resulted in a fivefold increase in organic loading,
whereas directional felling only doubled the load.
Streamside zones provided  a debris barrier that
limited  or totally prevented the loading increase,
with  effectiveness in restricting organic  loading
varying  with width  of the area.
  Large  debris deposited in a  stream during a
silvicultural activity normally should be removed
as soon as possible. However,  some large debris
within  a watercourse can  provide  stable  and
diverse habitats for biota. Removal of debris that
have been in position for any extended period and
have  trapped  considerable  sediment  normally
should not be undertaken until the full impact (loss
of habitat,  increased  turbidity, realignment  of
stream,  etc.)  is evaluated.  A general policy  for
removal of all debris in a stream is unreasonable
and could result in damage to water quality and
aquatic  habitat (Triska and Sedell 1977).
                                              IX.15

-------
                                   LITERATURE CITED
American Public Health  Association,  Inc.  1971.
  Standard methods for examination of water and
  waste water. 13th ed. Washington, D. C. 874 p.

Berry, J. D. 1975. Modeling the impact of logging
  debris  on the dissolved oxygen balance of small
  mountain streams.  M.S.  thesis.  Oreg. State
  Univ.,  Corvallis.

Brown, G.W.,  and J. T. Krygier. 1970. Effects of
  clear-cutting on  stream  temperature.  Water
  Resour. Res. 6(4):1133-1139.

Camp, T. R.  1965. Field  estimates  of oxygen
  balance parameters.  Proc.  Am. Soc. Civ. Eng.
  91(SA5):1.

Chase, E. S., and A. F. Ferullo.  1957. Oxygen de-
  mand  exerted by leaves stored under water. J.
  New Eng. Water Works Assoc. 71:307-312.

Davison,  R. C.,  W. P. Breese,  C. E. Warren, P
  Doudoroff.  1959. Experiments on the dissolved
  oxygen requirements  of cold water fishes. Sewage
  and industrial wastes. 31:950-966.

Eschner,  A. R., and J.  Larmoyeux.  1963. Logging
  and  trout:  Four experimental forest practices
  and their effect on water quality. Prog. Fish Cult.
  25:59-67.

Fair, G.  M. 1939. The  dissolved  oxygen sag — an
  analysis. Sewage Works J.  11:445-461.

Froehlich, H. A. 1976. Accumulation of large debris
  in forest streams before and after  logging. For.
  Eng. Dep., Oreg. State Univ.,  Corvallis. 10 p.

Garside,  E. T.  1966. Effects of oxygen in relation to
  temperature on the development of embryos of
  brook  trout  and  rainbow trout.  J.  Fish, Res.
  Board  Can. 23:1121-1134.

Garvin, W. F. 1974. The intrusion of logging debris
  into artificial gravel streambeds. Water Resour.
  Res.  Inst., Oreg. State Univ., Corvallis. WRRI-
  27.

Hall, J. D., and R. L. Lantz. 1969. Effects of log-
  ging on habitat  of coho  salmon and cutthroat
  trout in coastal streams. In Symp. salmon and
  trout in streams. T.  G. Northcote, ed. Univ. B.
  C., Vancouver, p. 355-375.
Hem, J. D.  1970. Study and interpretation of the
  chemical  characteristics  of natural water. U.S.
  Geol. Surv.  Water Supply Pap. 1473. 363 p.

Herrmann, R.  B., C. E. Warren, and P. Doudoroff.
  1962. Influence of oxygen concentration on the
  growth of juvenile coho salmon. Trans. Am. Fish.
  Soc. 89:17-26.

Holtje, R. K.  1971. Reaeration in small mountain
  stream. Ph.D. diss. Oreg. State Univ., Corvallis.
  146 p.

Jones, J. R. E. 1952. The reactions offish to water
  of  low  oxygen  concentration. J.  Exp. Biol.
  29:403-415.

Lantz, R. L. 1971. Guidelines for stream protection
  in logging operations. Oreg. State Game Comm.,
  Portland.  29 p.

McKee, J. E.,  and H. W. Wolf. 1963. Water quality
  criteria.  Calif.  State  Water  Resour. Control
  Board, Resour. Agency Calif.,  Sacramento. 548
  P-
Narver, D. W.  1971. Effects of logging debris on fish
  production.  In Proc. symp. for. land uses  and
  stream environ. J. T. Krygier and J. D. Hall, eds.
  Oreg. State  Univ., Corvallis. p. 100-111.

Ponce, S. L. 1974a. The biochemical oxygen de-
  mand of Douglas-fir  needles and twigs, western
  hemlock needles, and red alder leaves in stream
  water. M.S.  thesis. Oreg. State Univ., Corvallis.
  141 p.

Ponce, S. L. 1974b. The biochemical oxygen de-
  mand of finely divided logging debris in stream
  water. Water Resour. Res. 10(5):983-988.

Shellford, V. E., and W. C. Allee. 1913. The reac-
  tions of  fishes  to  gradients  of  dissolved at-
  mospheric gases.  J. Exp.  Zool. 14:207-266.

Sheridan, W. L.  1962. Waterflow  through a salmon
  spawning riffle  in Southeastern  Alaska. U.S.
  Fish and Wildl. Serv., Spec. Sci. Rep., Fish. No.
  407, 20  p.
Shumway, D.  L., C. E. Warren, and P. Doudoroff.
  1964. Influence  of oxygen concentrations  and
  water movement on the growth of steelhead trout
  and coho salmon embryos. Trans. Am. Fish. Soc.
  93:342-356.
                                              IX.16

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Slack, K., and H. R. Feltz. 1968. Tree leaf control
  on low flow water  quality in a small Virginia
  stream. Environ.  Sci. and Tech. 2(2):126-131.
Streeter, H. W., and E. B. Phelps. 1925. A study of
  the pollution and natural purification of the Ohio
  River.  Publ. Health  Bull.  146.  U.S.  Public
  Health  Serv.  U.S. Dep. Health,  Educ., and
  Welfare, Washington, D. C. 75 p.
Swanston, F, and T. Dyrness. 1973. Stability and
  steepland. J. For. 71(5):264-269. [Illus.]
Triska, F., and J. Sedell. 1977. Accumulation and
  processing of fine organic debris. Dep. Fish, and
  Wildl., Oreg. State Univ., Corvallis. 13 p.

Vaux, W. G. 1968.  Interchange of stream and in-
  tragravel water in a salmon spawning riffle. U.S.
  Fish, and Wildl. Serv. Spec. Sci. Rep., Fish. No.
  405. 11 p.

Whitmore, C. M., C. E. Warren, and P. Doudoroff.
  1960.  Avoidance  reactions  of salmonoid  and
  centrarchid fishes to low oxygen concentrations.
  Trans. Am. Fish. Soc.  89:17-26.

Zanoni, A. E. 1967.  Waste water deoxygenation at
  different temperatures. Water Res.  1:543-566.
                                              IX. 17

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               Chapter X

           NUTRIENTS
this chapter was prepared by the following individuals:

              John B. Currier
                 Coordinator

          with major contributions from:

            Arthur P. O'Hayre
                    X.i

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                             CONTENTS
                                                             Page

INTRODUCTION	   X.I
DISCUSSION  	   X.2
  SOLUBLE COMPONENT EVALUATION	   X.2
       The Loehr Study	   X.2
       The Hubbard Brook Study	   X.3
  INSOLUBLE COMPONENT EVALUATION  	   X.4
APPLICATIONS, LIMITATIONS, AND PRECAUTIONS	   X.7
CONCLUSIONS	   X.7
LITERATURE CITED 	   X.8
APPENDIX X.A: DETAILED DISCUSSION OF THE
  NUTRIENT CYCLE 	   X.12
    INPUT TO THE NUTRIENT CYCLE	   X.12
       Atmosphere	   X.12
         Atmospheric Nitrogen  	   X.12
         Atmospheric Phosphorus	   X.12
       Soil and  Rock	   X.15
         Nitrogen Inputs From Soil And Rock  	   X.15
         Phosphorus Inputs From Soil And Rock	   X.15
       Forest Fertilization	   X.15
    THE INTRACYCLE PROCESS	   X.15
     Intracycle Nitrogen	   X.15
       Mineralization	   X.15
       Nitrification	   X.16
     Intracycle Phosphorus 	   X.18
       Organic Phosphorus 	   X.18
       Inorganic Phosphorus	   X.18
    OUTPUTS FROM THE NUTRIENT CYCLE	   X.19
     Dissolved Materials 	   X.19
     Removal Of Vegetation	   X.19
     Nitrogen Outflux	   X.19
       Pathways Of Nitrogen Removal  	   X.19
       Nitrification And Mineralization	   X.20
     Phosphorus Outflux 	   X.20
APPENDIX X.B: EIGHTEEN STUDIES OF NUTRIENT
    RELEASES FOLLOWING SILVICULTURAL ACTIVITIES	   X.21
                                X.ii

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                              LIST OF FIGURES
Number                                                                   Page

X.I.  —Range of total N and P concentrations found in various non-point
          sources	  X.2
X.2.  —Summary of studies undertaken to quantify nitrogen release following
          silvicultural activities	  X.3
X.3.  —Percent  nitrogen (N)  in surface foot of soil	  X.5
X.4.  —Percent phosphorus (P205) in surface foot of soil	  X.6

X.A.I.—Biochemical cycle for nitrogen in  a  forest	  X.13
X.A.2.—Nitrogen (NH+4N-N and NOs-N)  in precipitation 	  X.14
X.A.3.—Simplified nitrogen cycle showing  N utilized in the  nitrate (NO :0 and
          ammonium (NHt) forms and acid and base relations associated with
          the various processes	  X.16
X.A.4.—Flow model of nitrogen cycling in an oak-hickory forest at Coweeta Ex-
          perimental Forest, North Carolina	  X.17
X.A.5.—General  estimate of the relative proportion of phosphorus present in
          each component of the geochemical, biochemical, and biogeochemical
          cycles of loblolly pine plantation ecosystem	  X.18
                                        X.iii

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                             LIST OF STUDIES
Number                                                                  Page
X.I. —Hubbard Brook Experimental Forest, New Hampshire	   X.22
X.2. —Hubbard Brook Experimental Forest, New Hampshire	   X.23
X.3. —White Mountain National Forest, New Hampshire	   X.24
X.4. —White Mountain National Forest, Upper Mill Brook, New Hampshire    X.25
X.5. —Leading Ridge  Watershed 2, Pennsylvania State University	   X.26
X.6. —Fernow Experimental Forest, West Virginia	   X.27
X.7. —Coweeta Hydrologic Laboratory, North Carolina 	   X.28
X.8. —USAEC's Savannah River Plant, Aiken, South  Carolina	   X.29
X.9. —Grant Memorial Forest, Georgia	   X.30
X.10.—H.J. Andrews Experimental  Forest, Eugene, Oregon	   X.31
X.11.—Bull Run Watershed,  Portland, Oregon	   X.32
X.12.—South Umpqua Experimental Forest, 50 Kilometers ESE  Rosberg,
         Oregon 	   X.33
X.13.—Alsea Basin,  Oregon  Coast Range	   X.34
X.14.—Bitterroot National Forest, Montana	   X.35
X.15.—Priest River Experimental Forest, Idaho	   X.36
X.16.—Marcell Experimental Forest, Minnesota	   X.37
X.17.— West Central Alberta, Canada	   X.38
X.18.—Dennis Creek, Okanagan Valley,  British Columbia	   X.39
                                     X.iv

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                                      INTRODUCTION
  Much concern has been expressed over nutrient
additions  to  streams following silvicultural ac-
tivities. Of the nutrients, nitrogen and phosphorus
generally have the greatest impact upon water
quality. Introduction of nitrogen and phosphorus to
forest streams may  result in  enrichment of the
receiving waters (i.e., eutrophication), as these two
chemicals are normally limiting  factors in the
production of aquatic vegetation. Accelerated ad-
ditions  of  nutrients to  streams following
silvicultural  activities may  result in  accelerated
eutrophication and adversely affect stream water
quality. In other cases,  however, enrichment of
streams may be beneficial, particularly in streams
relatively  devoid of dissolved  nutrients in  their
natural state.
  Streams  may show symptoms  of overenrich-
ment; however, there is  usually minimal oppor-
tunity for a buildup of these nutrients in the stream
system because of the continual transport of water
and the normally brief period of increased nutrient
influx to the stream. Other nutrients rarely cause
water quality problems. This discussion, therefore,
is limited to nitrogen and phosphorus. (For ad-
ditional information on the nutrient cycle, see ap-
pendix X.A.)
  Research  conducted  throughout  the  United
States and Canada has found that nutrient outflux
following  silvicultural  activity usually does not
result in  any  measurable deterioration of water
quality. The most notable exception is the Hub-
bard  Brook experimental  watershed in  New
Hampshire.  This was, however,  an extreme ex-
perimental treatment  and  not  a  normal
silvicultural activity. Based upon existing research,
it can be concluded that nutrient release associated
with  silvicultural   activities  may occur;  but
resulting concentrations of  nitrogen  and
phosphorus  will normally not be  great enough to
adversely  affect the water quality of the receiving
forest streams.
  Quantification of nitrogen and phosphorus influx
into a  watercourse, given  a  specific  site and
proposed silvicultural activity,  is not possible at
this time.  There are no available models capable of
accurately predicting the total nutrient addition to
streams due to silvicultural activities. The soluble
component of the nutrient outflux can be examined
presently  only  through a  comparison of those
nutrients  contributed by silvicultural  activities
with those  nutrients contributed by  other  land
management practices. The  insoluble component
can be estimated with cautious use of one available
model.
                                               X.I

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                                        DISCUSSION
  SOLUBLE COMPONENT EVALUATION
               The Loehr Study
  Numerous studies have been made  of the
relationship between streamflow and chemical load
in the stream. The dilution theory principle (an
average relationship between dissolved chemical
load and stream discharge) is now widely accepted.
A number  of  models  have been proposed to
describe the dilution theory (Carson and  Kirkby
1962,  Hendrickson and Krueger 1964, Toler  1965,
Hem 1970, Hall 1971, Betson and McMaster 1975).
However, this theory assumes both a relatively con-
stant  source of dissolved nutrients and  a constant
rate of release by weathering, independent of the
volume of water passing through the  soil. These
models, therefore,  are not suitable for  evaluating
nutrient outflux  due to  silvicultural activity
because release is variable, depending upon  vegeta-
tion uptake and microbiological processes.
  In lieu of an adequate model, an evaluation of
the relative impacts of non-point source nutrient
pollution from silvicultural activities  and other
land uses has been published by Loehr (1974) and
is presented here. Loehr compared available infor-
mation on characteristics and relative magnitudes
of certain non-point sources entering surface waters
and  commented on  the feasibility of  controlling
these sources. Concentrations  of organic and in-
organic compounds representative of the range that
could be  anticipated  from  various  non-point
sources  were compared. Loehr's results are dis-
played in figure X.I and indicate that  concentra-
tions of nitrogen and phosphorus lost from forest
lands approximate  those  found in precipitation.
Additional  data to support Loehr's  findings are
presented in figure X.2, and appendix X.B. Loehr's
findings have been confirmed by all the data with
the exception of the data from the Hubbard Brook
experiment.
3 .0


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-------
  This study represents the application of an ex-
treme treatment and not a normal silvicultural ac-
tivity.  Its  results have been  verified by  other
studies, although the magnitude of the changes in
nutrient release has not been as great  in  other
studies. The conditions under which the Hubbard
Brook study was conducted show that significant
water quality  degradation  is possible if (1) all
vegetation  is killed,  (2) revegetation is prevented
by application  of herbicides, and (3) the soils are
coarse  textured,  with a  low  cation exchange
capacity. These conditions do not normally exist
under prevalent  land management practices.
Silvicultural activities are presently  constrained so
that devegetation of a complete watershed is  not
generally a viable land management option. In ad-
dition,  the application of herbicides  to prevent
revegetation is  contrary to normal forestry opera-
tions. Finally,  many forest soils have a greater
capacity to  fix  nitrogen  and phosphorus,  or
otherwise prevent the loss of nutrients from a site.
 INSOLUBLE COMPONENT EVALUATION


  Nitrogen  in  the  soil is primarily organically
bound and is not readily transported in solution.
Nitrate and ammonium ions are available and can
be transported in solution in  the  soil water and
eventually  reach  a  watercourse. The nitrate ion
(NO 3) is the principal dissolved nitrogen form lost
from  the forest ecosystem; the ammonium ion
(NHt) is ordinarily strongly adsorbed to exchange
surfaces  and is not readily lost. However,  these
available forms of nitrogen — NO 3  and NHIj —
make  up only a small  proportion  of  the  total
nitrogen  present in soil.
  Phosphorus in soil may be present in the organic
or inorganic form.  The soluble inorganic  forms
derived from chemical weathering or decomposi-
tion of organic matter  are readily immobilized in
the soil and are not easily leached from it. The
primary mode of transport for organic forms of both
nitrogen and phosphorus is surface erosion.
  Outflux of insoluble,  precipitated or adsorbed,
organic nitrogen and total  phosphorus can be es-
timated  in  a  manner proposed  by  Midwest
Research Institute in their report to EPA (McElroy
and  others  1976). As  proposed  by Midwest,
"loading" functions for organic nitrogen and total
phosphorus can be estimated based upon the "sedi-
ment loading"  function derived from a modified
version  of  the  Universal   Soil  Loss Equation.
Concentrations  of total nitrogen and phosphorus in
the surface foot of soil can  be obtained from  ex-
isting general  maps  (figs.  X.3 and X.4),  from
regional or local Soil Conservation Service data, or
by actual measurement. The  Midwest model  in-
cludes an enrichment ratio  that is based upon the
soil  texture  and organic  matter  content. The
general loading function is:
                                                   where:
                                                     Y  =
  a   =
  S   =
  c   =
                                                                     Y =  aSCr
total  loading  (organic  and  adsorbed
nitrogen or total  phosphorus)  from sur-
face erosion, Ibs/ac/yr (kg/ha/yr),
dimensional  constant  (20  for  English
units or 10 metric units),
sediment  loading  from surface  erosion,
tons/ac/yr (MT/ha/yr),
total  (organic  nitrogen  or total
phosphorus) concentration in surface foot
of soil, g/lOOg,
enrichment  ratio,  nitrogen  values
generally  range  from  2  to  5,  and
phosphorus values range from 1 to 3, with
an average value of 1.5. The enrichment
ratio is the concentration of nitrogen or
phosphorus  in the  eroded  material
divided by its  concentration in  the soil
proper  (Massey  and  others 1953,
Stoltenberg and White 1953).
                                               X.4

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01
NITROGEN

Percent N
                                                                                                                                      Highly Diverse
                                                                                                                                      Insufficient Data
                                               Figure X.3.—Percent nitrogen (N) in surface foot of soil (after Parker 1946).

-------
><
                        \
PHOSPHORIC ACID



   Percent ?2O5




     0.0-0.04




[   JO. 05 -0.09
                                                                                                                                   0.10-0.19




                                                                                                                                   0.20-0.30
                                           Figure X.4.—Percent phosphorus (PzOs) in surface foot of soil (after Parker 1946).

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             APPLICATIONS,  LIMITATIONS, AND PRECAUTIONS
  The insoluble component model represents the     adequately tested in forested situations and should
current state-of-the-art; however,  it has not been     be used with caution.
                                     CONCLUSIONS
  Reinhart (1973), Loehr (1974), Patric and Smith       time because the concentrations and yields of
(1975), and  Sopper  (1975) evaluated available       constituents  are comparable to those  of
studies and  concluded  that normal  silvicultural       precipitation.  These two non-point  sources,
operations do not raise nitrogen and phosphorus       forest runoff  and  range land runoff,  may
concentrations above  public health standards for       generally be considered as background sources
drinking water. Loehr (1974) concluded:                unless  current  practices or available  data
  Control of forest land runoff and range land         change drastically.
  runoff does not appear to be necessary at this
                                             X.7

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                                   LITERATURE CITED
Alexander,  M.  1967.  Introduction to  soil
  microbiology. 472 p. John Wiley & Sons, Inc.,
  New York.

Aubertin,  G.  M.,  and J. H. Patric. 1972. Quality
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  and Timber Process., March 1972.  p. 14-15, 22-
  23.

Aubertin,  G. M.  and J.  H. Patric.  1974.  Water
  quality after clearcutting a small watershed in
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Bateridge, T. 1974. Effects of clearcutting on water
  discharge and nutrient loss, Bitterroot National
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  Resour.  Res., Univ. Montana,  Missoula. p. 36,
  38, 42-46.

Betson, R. P., and W. M. McMaster. 1975. Non-
  point  source  mineral water quality  model.  J.
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Bormann,  F. H., and G. E. Likens. 1967. Nutrient
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Bormann,  F. H., and G. E. Likens.  1970.  The
  nutrient cycles of  an  ecosystem.  Sci.  Am.
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Brown, G. W., A. R. Gahler,  and R.  B. Marston.
  1973. Nutrient losses after clear-cut logging and
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Carson, M. A., and M. J. Kirkby. 1972. Hillslope
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Coffee, R. C., and W. V. Bartholomew. 1964. Some
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Colman, E.  A. 1953. Vegetation and  watershed
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Corbett, E. S., J. A.  Lynch, and W. E. Sopper.
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Cramer, 0. P., ed. 1974. Environmental effects of
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Cravens, J. H. 1974. Personal communication. Reg.
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DeBell, D. S., and C. W. Ralson.  1970. Release of
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DeByle, N.  V., and P.  E. Packer.  1972.  Plant
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Dochinger,  L.  S.,  and T.  A. Seliga.  1976.
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Douglass,  J. E., and W. T. Swank. 1975. Effects of
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Feth, J. H. 1966. Nitrogen compounds in natural
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Fredriksen, R. L. 1977. Personal communication.
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Fredriksen, R. L., D. G. Moore, and L. A. Norris.
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  Soils Conf.,  Laval Univ., Quebec City, Can. p.
  283-313.
                                              X.8

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Greenwood, D. J. 1962. Measurement of microbial
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Grier, C. C.  1975. Wildfire effects on nutrient dis-
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Hall, F. R. 1971. Dissolved  solids — discharge
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Hem, J. D. 1970. Study and interpretation of the
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Hendriksen,  G.  E., and  R.  A.  Krueger. 1964.
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Hetherington, E. D. 1976. Dennis Creek: A look at
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  phosphorus, dissolved organic carbon, and fine
  particulate  carbon  from  Hubbard  Brook
  watersheds.  Limnol. and Oceanogr.  18(5): 734-
  742.

Hornbeck, J. W., G. E. Likens, R. S. Pierce, and F.
  H. Bormann. 1973.  Stripcutting as a means of
  protecting site and  streamflow  quality when
  clearcutting northern hardwoods. 4th North Am.
  For. Soils Conf., Quebec, Can. p.  209-225.

Johnsen, D. R. 1953. A laboratory study of the
  decomposition of vegetable debris in relation to
  the formation of raw humus. Plant and Soil
  4:345-369.

Jorgenson, J. R., C. G. Wells, and L. Metz. 1975.
  The nutrient cycle:  Key to  continuous forest
  production. J. For.,  July. p. 400-403.

Junge, C. E.  1958.  The distribution of ammonia
  and nitrate in rain water over the United States.
  Trans. Am. Geophys. Union 39(2) :241-248.
Keeney,  D.  R.  1973.  The  nitrogen cycle  in
  sediment-water  systems. J. Environ. Qual.
  2(l):15-29.

Kormondy,  E.  J.   1976.  Concepts  of  ecology.
  Prentice-Hall, Inc., Englewood Cliffs, N.J.

Kramer, J. R., S. E. Herbes, and H. E. Allen, eds.
  1972. Phosphorus: Analysis of water, biomass,
  and sediment. In  Nutrients in natural waters, p.
  51-101. Wiley-Intersci., John Wiley & Sons, Inc.,
  New York.

Lewis, W. M., Jr. 1974. Effects of fire on nutrient
  movement in a South Carolina pine forest. Ecol.
  55:1120-1127.

Likens, G. E.  1976.  Acid precipitation. Chem. and
  Eng. News 54(48):29-44.

Likens, G. E.,  F. H. Bormann, N. M. Johnson, and
  others. 1970. Effects of forest cutting and her-
  bicide treatment on nutrient budgets in the Hub-
  bard Brook watershed ecosystem. Ecol. Monogr.
  40(l):23-47.

Likens, G. E., F. H. Bormann, J.  S. Eaton, and
  others. 1976. Hydrogen ion input to the Hubbard
  Brook  Experimental  Forest,  New Hampshire,
  during the last decade. In  Proceedings first inter-
  national symposium on acid precipitation and
  the forest ecosystem. USDA Serv. Gen. Tech.
  Rep.  NE-23,  p.   293. Northeast. Exp. Stn.,
  Bloomall,  Pa.

Loehr, R. C. 1974. Characteristics and comparative
  magnitude of non-point sources. J. Water Pollut.
  Control Fed. 46(8): 1849-1872.

Lutz, H. J., and R. F. Chandler, Jr. 1961. Forest
  soils. 514  p. John Wiley and Sons,  Inc., New
  York and London.

McCarty,  P.  L., chairman.  1970. Chemistry of
  nitrogen and  phosphorus  in water.  J.  Am.
  Waterworks  Assoc. 62:127-140.

McElroy, A. D., S.  Y., Chiu, J. W. Nebgon, and
  others. 1976. Loading for assessment of water
  pollution from non-point  sources. U.S. Environ.
  Prot. Agency.  Off. Res. and Dev.,  Washington,
  D.C. p.  267-268.

Massey, H.  F., M.  L. Jackson, and 0. E. Hays.
  1953. Fertility  erosion on two Wisconsin soils.
  Agron. J. 45(11):543-547.
                                               X.9

-------
Mikola,  P.  1960.  Comparative  experiment  on
  decomposition rates of forest litter in Southern
  and Northern Finland. Oikos 11:161-166.

Mitchell, J. E., J. B. Waide, and R. L. Todd. 1975.
  A  preliminary  compartment  model  of  the
  nitrogen cycle in a deciduous forest ecosystem. In
  Mineral  cycling  in  Southeastern ecosystems.
  Howell, F. F., J.  B. Gentry, and M.  H.  Smith,
  eds. AEG Symp.  Series (CONF-740513).

Moore, D. G., and L. A. Norris. 1974. Soil processes
  and  introduced chemicals. USDA For. Serv.
  Gen. Tech. Rep. PNW-24, 33 p. Pac. Northwest.
  For.  and Range Exp. Stn.,  Portland, Oreg.

National  Academy  of   Sciences   and National
  Academy of Engineering.  1972.  Water quality
  criteria 1972.  U.S. Environ.  Prot. Agency,
  Washington, B.C. p. 594.

Parker,  F.  W., J. R. Adams, K.  G. Clark, and
  others. 1946. Fertilizer and lime in the  United
  States — resources, production marketing and
  use. U.S. Dep. Agric. Misc. Publ. 586. 96 p.

Patric,  J. H.,  and D.  W. Smith.  1975.  Forest
  management and nutrient cycling in  eastern
  hardwoods. USDA For. Serv. Res. Pap. NE-324,
  12 p. Northeast. For. Exp. Stn.,  Bloomall, Pa.

Patric, J. H., and G. M. Aubertin. 1976. Response
  of a headwater stream  to diameter-limit timber
  harvesting.  Unpubl. manuscr. on file at USDA
  For.  Serv., Northeast. For. Exp. Stn., Bloomall,
  Pa. 15 p.

Pierce, R. S.,  C.  W. Martin, C. C. Reeves, and
  others. 1972. Nutrient  losses from clearcuttings
  in New  Hampshire.  In National symposium
  watersheds in transition. Am. Water Resour. As-
  soc. Proc. Ser. 14. p. 285-295.

Reinhart, K. G. 1973. Timber harvest clearcutting
  and nutrients in the Northeastern United States.
  USDA For.  Serv.  Res. Note  NE-170. 5  p.
  Northeast For. Exp. Stn., Bloomall, Pa.

Reuss,  J.  0.  1976.  Chemical and  biological
  relationships relevant to the effect of acid rain-
  fall on the soil-plant system. In Proceedings of
  the first international symposium on  acid
  precipitation  and the forest ecosystem. USDA
  For.  Serv.  Gen.  Tech. Rep. NE-23,   293  p.
  Northeast For. Exp. Stn., Bloomall, Pa.
Reuss, J. 0., and R. L. Smith. 1965. Chemical reac-
  tions of nitrites in acid soils. Soil Sci. Soc. Proc.
  p. 267-270.

Robinson, E., and R. C. Robbins. 1970. Gaseous
  nitrogen compound pollutants from urban and
  natural sources. J. Air Pollut.  Control  Assoc.
  20(5): 303-306.

Rothacher, J., C. T. Dryness, and R. L. Fredriksen.
  1967. Hydrologic and related characteristics of
  three small watersheds in the Oregon  cascades.
  U.S. For.  Serv.  PNW-unnumbered.  Pac.
  Northwest. For. and Range Exp.  Stn.,  Portland,
  Oreg. 54 p.
Singh  T.,  and Y.  P. Kalra. 1975.  Changes in
  chemical composition of natural waters resulting
  from progressive clearcutting  of forest  catch-
  ments in West Central Alberta, Canada. Int. As-
  soc. Sci. Hydrol. Symp. Proc. Publ. 117. p. 435-
  449.  [Tokyo, Japan. December 1970.]

Smith, W. H., F. H.  Bormann, and G. E. Likens.
  1968. Response of chemoautotrophic nitrifiers to
  forest cutting. Soil Sci. 106(6):471-473.

Snyder, G. G., H. F.  Haupt, and G. H. Belt, Jr.
  1975. Clearcutting and  burning  slash  alter
  quality  of  stream  water  in Northern Idaho.
  USDA   For.  Serv.  Res.  Pap.  INT-168,  34 p.
  Intermt. For. and  Range Exp. Stn.,  Ogden,
  Utah.

Sopper, W. E. 1975.  Effects of timber harvesting
  and  related  management  practices  on  water
  quality in forested watersheds. J.  Environ. Qual.
  4(l):24-29.

Stewart, W. D. P. 1975.  Nitrogen fixation by free-
  living micro-organisms. Int. Bio. Programme 6.
  471 p. Cambridge Univ. Press, Eng.

Stoltonberg, N. W., and J.  L. White. 1953. Selec-
  tive loss of plant nutrients by erosion. Soil Sci.
  Soc. Proc.  17(4):406-410.

Stone, E. 1973. The impact of timber harvesting on
  soils and water. Appendix M.  In Report of the
  President's Advisory Panel on timber and the en-
  vironment. April. U.S. Gov. Prin.  Off. 197310-
  505-287. p. 445-467.

Stuart, G., and D. Dunshie. 1976. Effects of timber
  harvest on water chemistry. Hydol. Pap. USDA
  For. Serv. East. Reg.  34 p.
                                              X.10

-------
Stumm,  W., and  J.  J.  Morgan.  1970. Aquatic
  chemistry. 583 p. Wiley-Interscience: New York,
  London, Sydney, Toronto.

Swank, W. T., and J. E. Douglass.  1975. Nutrient
  flux  in undisturbed  and  manipulated  forest
  ecosystems in the Southern Appalachian Moun-
  tains. Int. Assoc. Sci. Hydrol. Symp. Proc., Publ.
  117. p.  445-456. [Tokyo, Japan. December 1970.]

Switzer, G. L., and L. E. Nelson. 1972. Nutrient ac-
  cumulations and cycling in loblolly pine, Pinus
  taeda,  plantation ecosystems: The first  twenty
  years. Soil Sci. Soc. Am. Proc. 36(1):143-147.

Tabatabai, M. A., and J. M. Laflen. 1976. Nutrient
  content  of  precipitation over  Iowa.  In
  Proceedings of the first international symposium
  on acid precipitation and the forest ecosystem.
  USDA  For. Serv. Gen. Tech. Rep. NE-23, p. 293.
  Northeast. For. and Range Exp. Stn., Bloomall,
  Pa.

Tisdale, S. L., and W. L. Nelson. 1966. Soil fertility
  and fertilizers, p. 194-243. Macmillan Co., New
  York.
Toler,  L. G.  1965.  Relation  between  chemical
  quality and water discharge of Spring Creek,
  Southwestern  Georgia. U.S.  Geol. Surv. Prof.
  Pap. 525-C.  p. C209-C213.

U.S. Senate Hearings Subcommittee on Public
  Lands. 1971.  "Clear-cutting" practices  on
  national timberlands. First session on manage-
  ment practices on the public lands, p. 1057-1064.

Verry,  E. S. 1972. Effect of an aspen clearcutting
  on water yield and quality in Northern Min-
  nesota. In National symposium on watersheds.
  Trans. Am. Water Resour. Assoc. Proc., Ser. 14.
  p. 276-284.

Waide, J. B.,  and W. T. Swank. 1975.  Nutrient
  recycling  and the  stability of ecosystems:
  Implications  for  forest  management in  the
  Southeastern United States. Proc. Natl. Conv.
  Soc.  Am. For. [Washington, D.C. Sept. 28-Oct.
  2, 1975.] p. 404-424.

Weber, D. F., and P. L. Gainey. 1962. Relative sen-
  sitivity of nitrifying organisms to hydrogen ions
  in soils and in solutions. Soil Sci. 94(3):138-145.
                                              X.ll

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                                       APPENDIX X.A:
                     DETAILED DISCUSSION OF THE NUTRIENT CYCLE
  The forest nutrient cycle is generally segmented
into three compartments — input, intracycle, and
output. The action  and interaction  of the major
compartments of the process are depicted in figure
X.A.I. Placing the nutrient cycle  in such a format
forces the investigator to consider the processes and
variables that  are likely to be  impacted  by
silvicultural  activities and the effect that  these
changes will have on soil and water  chemistry.
     INPUT TO THE NUTRIENT CYCLE

   Nutrient inputs to a forest ecosystem come prin-
 cipally from (1) the atmosphere, (2) the soil and
 underlying bedrock, and (3) depositions by floods
 on alluvial  terraces. Alluvial  deposition is not a
 dominant nutrient  input factor for many of the
 forested areas. Man enters the cycle with fertilizer
 additions.


                 Atmosphere

   Atmospheric inputs account  for  most of the
 nutrients  entering  the cycle,  usually  during  a
 precipitation event, in the form of dissolved gases,
 aerosols,   and  solid  particulate  matter.
 Nonprecipitation events, commonly referred to as
 dry fall, also contribute solid  particulate matter;
 and in some areas, aerosols are carried by prevail-
 ing winds and storm tracts from cities, industrial
 centers, and agricultural lands, then deposited on
 the forest without benefit of a precipitation event
 (U.S. Senate Hearings 1971, Jorgensen and others
 1975).  Deposition of dry fall and aerosols may oc-
 casionally be  extensive  during  initiation  of  a
 precipitation event, when  these  materials are
 "washed"  from  the atmosphere.  In any event,
 precipitation falling on  a forested area is not
 chemically  pure  water  but may  contain  many
 chemical  compounds,   ranging  from  beneficial
nutrients (such  as  nitrogen) to deleterious acid
compounds (U.S. Senate Hearings 1971). An exten-
sive coverage of the  addition of acidic materials to
the  forest  ecosystem can  be found in  the
"Proceedings of the First International Symposium
on Acid Precipitation and the  Forest Ecosystem"
(Dochinger and Seliga 1976).
 Atmospheric Nitrogen

   Precipitation  contains significant quantities of
 numerous substances including nitrogen; one of the
 primary sources of nitrogen input  to the  forest
 ecosystem  is through the atmosphere (fig. X.A.I).
 Nitrogen occurs in the gaseous form — principally
 as N2, NO, N02 and NHs, and in aerosols — as
 NH^ and  NOs. However, the gaseous nitrogen
 form N2 is considered inert and cannot be directly
 utilized  by most organisms. Biological fixation by
 microorganisms  during  the  intracycle  process
 (discussed in detail in "The Intracycle Process")
 converts free nitrogen to the ammonia form which
 is then utilized  in biological functions.
   The compounds named are naturally produced;
 however, increasingly large  concentrations of them
 are the result of industrial activities, vehicle ex-
 hausts, and  agricultural operations  (Feth  1966,
 Robinson  and  Robbins  1970).  Transport of
 relatively  large quantities of  nitrogenous  com-
 pounds  from  various concentrated pollutant
 sources by  prevailing winds or storms has resulted
 in the deposition  of large amounts of  these
 materials (Likens and  others 1976).  Such deposi-
 tion occurs not  only as dissolved and particulate
 matter in precipitation, but it also occurs during
 nonprecipitation periods as dry fall  and aerosol
 deposition. Junge (1958) reported a nationwide sur-
 vey of ammonium and nitrate in rainwater over the
 United States. The study indicated that concentra-
 tions of NH^ and NO 3 varied markedly. Nitrogen
 input values have been estimated for the United
 States and are presented in figure X.A.2. It should
 be noted that the values  are  based on regional
 averages and specific  sites can  differ markedly
 from the regional values due to local conditions.
   Electrochemical  and  photochemical  fixation,
 lightning, and radiation convert a limited amount
 of elemental nitrogen to available inorganic forms.
Atmospheric Phosphorus

  Precipitation may also be a source of phosphorus
input into the system, but the quantities involved
can generally be assumed to be minor in com-
parison to  those from the weathering of soil and
rock (Tabatabai and Laflen 1976).
                                              X.12

-------
                                                      Atmospheric Inputs
                            Water

                            Transport
                                                     t
                                                     I
                                                     I
                                                Volatilization
                                                     I
                                                     I
                                                        Dry Fall  Interception  Interception Loss  |    Evaporation

                                                                       t
                                   Evapotranspiration
Precipitation
Vegetation
                                                  Harvesting
00
^ Chemical

Transport
Overland
Flow
I
1
1
t

I
i
i
III !
j Foliar Drip Decomposition
fj| Fixation
Impervious Area
or Bare Soil
Litter & Organic
Layer
1 1 I 1
Percolation
t H t
' T '
Subsurface Flov
i Lead
t
Streamflow
(Exchange/
Transport)
V
Soil Water _
ling 1
Leaching
i
! Ne
i i FyphsinnA

1 Processes 	 ^
'Weathering 	 ^
w Minerals. *.
Soil
Micro-
organisms
A i
Mineralization
i
j Immobilize
	 1
i


1
1
1
1
UpU
1
ition |
1
1
1


Mineral Soil,
Weathering
Bedrock


ike

                         4.
                    i Goundwater Flow
                                                     Ground water
                                ^-Weathering	i
                                          Figure X.A.1—Biochemical cycle for nitrogen in a forest.

-------
           .5 kg/ha/yr
                         .5 kg/ha/yr
2.0 kg/ha/yr
1.0 kg/ha/yr
                                         1.0 kg/ha/yr    1.5 kg/ha/yr     2.0 kg/ha/yr          2.5 kg/ha/yr
                  1.5 kg/ha/yr
            1.0 kg/ha/yr
                               1.0 kg/ha/yr
    1.0 kg/ha/yr



    1.5 kg/ha/yr
                                          Figure X.A.2.—Nitrogen (NH+4 and NO;,) in precipitation.

-------
                 Soil and Rock
              Forest Fertilization
  Chemical decomposition and physical weather-
ing of the  soil and  bedrock continually  release
nutrients to the ecosystem. Soil and bedrock are
the  principal sources of  metallic  cations,
phosphorus, and trace metals.
  Soil. — Weathering and decomposition of the
solum and  regolith  add significant amounts of
nutrients to the forest and the intracycle processes.
Weathering and decomposition occur much more
rapidly within the upper soil horizons (i.e., rooting
zone)  where plants,  animals,  bacteria, and  soil
fungi all contribute to decomposition of the soil and
secondary  minerals, and  where the  physical
processes, particularly freezing and thawing, ac-
celerate the weathering of the soil and rock (Lutz
and Chandler 1961).
  Bedrock. — Geologic weathering and decom-
position  of  bedrock  are not primary sources of
nutrient input to the  forest ecosystem over a short
period (i.e., timber rotation age), in that nutrients
released from rock do not normally enter the forest
ecosystem  directly  through  the  intracycle
processes, but  are removed from the system via
deep ground water. An exception occurs when the
root zone penetrates to bedrock.
Nitrogen Inputs From Soil and Rock

  Geologic formations do not have large amounts
of nitrogen present, so nitrogen inputs to the forest
ecosystem from geologic weathering and  chemical
decomposition are  insignificant,  especially when
compared  with  nitrogen  inputs  from   the  at-
mosphere.
   Introduction of nitrogen and phosphorus to the
 forests by fertilization can be a potentially signifi-
 cant input  source. However, at the present time
 forest fertilization has not been extensively under-
 taken and  has  been  limited  to  the Pacific
 Northwest and  to the  Southeast. Fertilization  is
 the only major nitrogen input source that the forest
 land  manager  can  control. A  more  complete
 evaluation of its use and potential water quality
 degradation is  presented in  "Chapter  XI:
 Introduced Chemicals."
   The introduction of phosphorus to the forest by
 fertilization may also be a significant input in some
 locations but, as mentioned  previously, forest fer-
 tilization  is  not  being  applied to large acreages
 nationally.  See  "Chapter  XI:  Introduced
 Chemicals," for a more complex discussion.
        THE INTRACYCLE PROCESS
  Intracycle  processes (fig. X.A.1) are numerous
and varied. Nutrients entering the  ecosystem in
available  form  are utilized  by vegetation and
animals and become unavailable (i.e., they become
stored nutrients). The  transfer rate of nutrients
between living organisms (vegetation and animal),
forest floor, and mineral soil is dependent upon the
nutrient's chemical and  physical characteristics
and physiological function (Jorgensen  and others
1975).
              Intracycle Nitrogen
Phosphorus Inputs From Soil and Rock

  Phosphorus input to the forest ecosystem comes
almost exclusively from chemical decomposition of
rocks. Phosphorus  is estimated to rank eleventh
among elements in igneous  rocks. It occurs in all
known minerals as phosphates (McCarty 1970).
Apatites,  the   principal  minerals  containing
phosphorus, are found in almost all igneous  and
sedimentary rocks.  Phosphorus  in soil  can  be
classed  generally  as  organic  or  inorganic.
Phosphorus is found predominantly in the mineral
fraction in combination with a heavy metal, iron,
aluminum,  or magnesium  (McElroy  and others
1976).
Mineralization

  Mineralization,  or  ammonification,  is  ac-
complished by heterotrophic  bacteria,  ac-
tinomycetes,  and  fungi.  These  ammonifying
microorganisms1  metabolize organic  nitrogen  —

  lTwo general groups of organisms fix nitrogen — symbiotic
nitrogen  fixers and free-living nitrogen fixers.  Symbiotic
organisms are associated with legumes, and several tree species,
notably  alder. The quantity of nitrogen fixed by symbiotic
organisms exceeds that fixed by free-living nitrogen fixers by a
factor of 100. Symbiotic nitrogen fixers are restricted to the ter-
restrial environment, whereas free-living nitrogen fixers  are
found  in both  terrestrial  and aquatic environments.
Azotobacter. Clostridium, and blue-green algae are  the primary
free-living nitrogen fixers  (Stewart 1975, Weber and Gainey
1962, Kormondy 1976).
                                               X.15

-------
amino acids, urea, uric acids and peptone (usually
in the form of an amine group, ~NH.2) — to an in-
organic  form,  ammonium.  Excess  ammonium
produced by the organisms is released; some of this
nitrogen is lost from the soil to the atmosphere as
gaseous ammonia, NHa (Kormondy 1976).
   Mineralization is the principal nitrogen process
conducted by microorganisms in highly acidic soils.
DeByle and Packer (1972)  reported that nitrifica-
tion rates were barely detectable in acid soils under
a coniferous  stand.  They concluded  that am-
monium  was  probably the  principal  form  of
available  nitrogen present  and that because of its
high solubility could easily be lost in deep seepage
or overland flow.
   However, most of the nitrogen remains within
the  forest  ecosystem,  being  utilized  by  soil
microorganisms or vegetation, becoming adsorbed
on clay and organic colloids (through cation ex-
change), and  by  remaining in solution in the soil
water (Bormann  and Likens  1967).
Nitrification

  Nitrification (fig. X.A.3) is the biological conver-
sion of organic or inorganic nitrogen compounds
from a reduced to a more  oxidized  state,  NOs.
Although  nitrification  usually  applies  to
autotrophic oxidation of ammonia or  nitrate ions,
                                          numerous heterotrophs, including bacteria, algae,
                                          and fungi are known to oxidize organic nitrogen to
                                          nitrite or nitrate. It is generally acknowledged that
                                          the rate  of nitrogen oxidation by heterotrophs is
                                          negligible  compared  to  that  by  autotrophs.
                                          Autotrophic nitrifying bacteria are confined largely
                                          to Nitrosomonas (oxidation of NH^ to NO 2) and
                                          Nitrobacter (oxidation  of NO 2 to NOlj); however,
                                          five other genera have  also been shown to oxidize
                                          nitrogenous compounds. Adequate oxygen must be
                                          present for nitrification to occur. Nitrification has
                                          been  detected in  aquatic  systems  with approx-
                                          imately  0.3 ppm  dissolved  oxygen  (Greenwood
                                          1962).
                                            For most soils, nitrification depends very much
                                          on pH. It usually decreases greatly at a pH below
                                          6.0 and  becomes negligible at a pH of 5.0 (Alex-
                                          ander 1967).  The  Hubbard Brook  study,  where
                                          nitrification rates were increased in an acid soil
                                          (pH  4) following a complete clearcut,  is a  par-
                                          ticularly  notable exception to the  norm. It was
                                          hypothesized by the investigators  that the in-
                                          creased  nitrification rate was caused by  a little
                                          known species of  nitrifying bacteria  adapted to
                                          more  acid  conditions (Likens and  others  1970).
                                          Nitrate and nitrite, end products of the nitrifica-
                                          tion  process, are  the  principal  components of
                                          nitrogen outflux from the forest ecosystem. (This
                                          process is discussed in more detail under "Outputs
                                          From the Nutrient Cycle — Nitrogen  Outflux" in
                                          this appendix.)
     Plant

         NH2
      R-C—R -*-
                  ASSIMILATION
                 	NH3  -•-
             Organic Nitrogen
                                                   NO3+H2O
                                             NH4r
•2H+	^NH4++2O2
    DENITRIFICATION
-      N03-
                                                               2H
     Soil
 NH2

_C_
                                           H
R ORGANIC
  NITROGEN
                           MINERALIZATION
                                                                          OH-
                                                   2H+
                                                           NH4++2O2
                                                                        N03-
                                                                      NITRIFICATION
                                                                     H+*N03~+H20
         Figure X.A.3.—Simplified nitrogen cycle showing N utilized in the nitrate (NO3) and ammonium (NHt)
         forms and showing acid and base relations associated with the various processes (after Reuss 1976).
                                               X.16

-------
  The intracycle nitrogen processes have been in-
tensively investigated at the Coweeta Experimen-
tal Forest,  North Carolina. A  relatively un-
disturbed oak-hickory  stand was selected, and a
flow model of the nitrogen cycle for this forest was
prepared.  An estimate of  the  nitrogen pools,
vegetation increments  of nitrogen,  and  transfer
rates among the various compartments was made
and is illustrated  in  figure X.A.4.  The model
shows that most of the nitrogen in the undisturbed
forest is contained in large storage pools that turn
over slowly. Over 80 percent of the total nitrogen in
this  forest ecosystem is bound within soil organic
matter, with about 11 percent in total vegetation, 3
percent in litter,  4  percent in microbial biomass,
and 2 percent in free soil (Mitchell and others 1975,
and Waide  and Swank 1976).
                        X1

                         Reproductives

                             2.738
          Figure X.A.4—Flow model of nitrogen cycling In an oak-hickory forest at Coweeta Experimental Forest,
           North Carolina. Values Inside boxes represent standing crops of nitrogen (kg N/ha); values inside dotted
           lines are vegetation Increments (kg N/ha/yr); numbers on arrows represent nitrogen transfers among
           compartments (kg N/ha/yr). This diagram shows nitrogen transfer associated with nitrogen uptake by
           plants and return to litter-soil pools (after Waide and Swank 1976).
                                                X.17

-------
  Although the values presented in the flow model
are valid only for the specific site studied, the flow
model itself has general applicability to all forest
types. Detailed analyses, similar to the one under-
taken in this study, are necessary to quantify the
actual amounts and rates of nitrogen in the cycle,
but are not feasible except  in a research environ-
ment. Forest managers could utilize the results of
such  studies to evaluate the potential impacts of
changing the nitrogen cycle.
             Intracycle Phosphorus
that  may  make  up the  dissolved  organic
phosphorus  fraction of waters draining a forested
ecosystem (Stumm and Morgan 1970). It has been
estimated that about 40 to 50 percent of the organic
soil phosphorus  consists of nucleic  acids,  inositol
phosphate  and  phospholipids; the remainder  is
largely unidentified. It  is known that decomposi-
tion of organic matter results in the mineralization
of organic phosphorus and the release of inorganic
phosphate. Actual chemical reactions involved are
not fully known.
   Phosphorus intracycle processes (figure X.A.5)
 are  neither fully understood nor  quantified.
 Research to date has been limited  in  scope  to
 general processes and to site factors that influence
 them. Phosphorus occurs as both inorganic and
 organic compounds.
 Geochemical
    5%
Figure X.A.5—General estimate of the relative proportion of
  phosphorus present in  each component of the
  geochemical, biochemical, and blogeochemlcal cycles of
  loblolly pine plantation ecosystem, 20th year (after SwKzer
  and Nelson 1972).
Organic Phosphorus

  Organic phosphorus compounds found in forest
soils and water are products of biochemical reac-
tions. Almost no information is available to iden-
tify specific compounds or groups of compounds
Inorganic Phosphorus

  Inorganic phosphorus  compounds occur as con-
densed  phosphates  and  orthophosphates.
Condensed phosphates  are generally manmade
compounds but some are also generated by all liv-
ing organisms. These latter  compounds are un-
stable in water, where they are slowly hydrolyzed to
the orthophosphate form (McCarty 1970).
  Inorganic phosphate compounds generally react
with metallic cations  and clays present in soil to
form complexes. Phosphate materials held by the
soil may be loosely adsorbed and remain available
to plants or may be firmly fixed and unavailable.
  Acidic  mineral  soils generally  contain  ap-
preciable quantities of  adsorbed aluminum and
smaller but  significant  amounts of iron and
manganese. These ions  combine with phosphates
to  form  insoluble  compounds  that may  be
precipitated from soil solution or adsorbed on the
surface of iron and aluminum oxides or on clay par-
ticles. The more acidic soils contain more adsorbed
aluminum and iron;  therefore, the products of
phosphorus  fixation   are  largely complex
phosphates of iron and aluminum.
  Another mechanism whereby phosphorus is fixed
in the soil is the reaction of phosphates with silica
clays. Phosphorus  and   polyphosphates  are  ad-
sorbed onto clay minerals by chemical bonding of
the anion to positively charged edges of the clays
and by substitution of phosphates for silicate in the
clay structure. In general, high phosphate adsorp-
tion by  clays occurs at  lower  pH values (Stumm
and Morgan  1970);  in most soils  phosphorus
availability is at a maximum in the pH range 5.5 to
7.0 and decreases as the pH  drops below  5.5
(Tisdale and Nelson 1966).
                                              X.18

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 OUTPUTS FROM THE NUTRIENT CYCLE


   Nutrients  are naturally lost  from  the  forest
 ecosystem in the form of dissolved or particulate
 matter in moving water  or  colluvium or both,
 through removal of the vegetation, through the dif-
 fusion or transport of gases or particulate matter by
 wind, and by fire or by animal activity. Gaseous ex-
 change from the  soil and  vegetation  to the at-
 mosphere has not been extensively studied, but it
 does not  appear that this would  account for ap-
 preciable nutrient loss.
surface. Soil water loss (i.e., evapotranspiration) is
reduced, which increases soil moisture. Nutrients
made  available in the  soluble form  during the
decomposition processes may exceed nutrient up-
take capacity of the vegetation remaining on the
site. Excess available nutrients then become lost
from  the forest ecosystem in surface and ground
water flows to streams and deep seepage (Cramer
1974).
               Nitrogen Outflux
              Dissolved Materials
   Nutrients are lost from the system in overland
 flow, subsurface flow and ground water. Numerous
 studies have shown that overland flow rarely occurs
 within an undisturbed forest (Colman 1953); and
 even following  silvicultural activities,  overland
 flow does not normally contribute significantly to
 watershed discharge.
   The chemical  content  of subsurface flow and
 ground water depends  on both biochemical and
 geochemical  cycles. Thus the chemical composi-
 tion will vary regionally and seasonally depending
 on variations  in rates of decomposition of organic
 matter  and  immobilization by microorganisms,
 differences in weathering and exchange processes,
 and changes  in concentration  brought  about by
 vegetative uptake. Nutrients carried in  the water
 draining a forest ultimately  enter the streams and
 determine the chemical character of the receiving
 stream.
            Removal Of Vegetation


  Timber harvesting results in the loss of nutrients
from  the forest  ecosystem.  The  proportion  of
nutrients in the vegetation lost from the forest is
determined by the utilization  that is made of the
tree, being maximized when the entire tree (bole,
limbs, foliage, and roots) is utilized and minimized
when only the bole is removed from the site. The
removal  of  overstory  vegetation  results in ac-
celerated decomposition of organic matter on and
in the forest floor  due  to an  increase  in soil
temperature and moisture content. Increased soil
temperatures are caused by removal of the shading
trees, which allows direct solar heating of the soil
Pathways Of Nitrogen Removal

  Nitrogen  is  lost from  a forest  ecosystem by
volatilization,  removal of the  biomass through
harvesting, and by leaching to surface and subsur-
face flows.
  Volatilization.  — Generally,  volatilization
losses are extremely limited due to the nature of
the forest environment. However, large volatiliza-
tion losses of nitrogen occur when forest and log-
ging residue are burned. Wildfire and prescribed
burning of slash result in loss of organic nitrogen in
the vegetation  (DeBell and Ralston 1970).  Grier
(1975) reported that a wildfire on the Entiat Ex-
perimental Forest, Washington, caused a reduction
of 97 percent of the nitrogen in the forest floor and
two-thirds of the nitrogen in the Ai horizon of the
mineral soil. Ash from fires may be carried by the
wind or by  surface erosion  into  a watercourse.
Losses  via  volatilization were  discussed in
"Nitrification and Mineralization."
  Removal of the  biomass.  —  Nitrogen  as-
similated by vegetation and utilized in biomass
production is lost from the site when the vegetation
is harvested and physically removed from the site.
  Surface and subsurface flow. — Nitrogen loss
from a site in the surface water or soil  water has
direct and immediate impact on the quality  of
water draining a forested area. Nitrogen may be in
solution (principally as NO 3) or transported by the
water adsorbed to suspend particles (principally as
NHt  and organic  compounds). The  intracycle
processes — mineralization  and nitrification —
that have as their  end products nitrate and am-
monium,  will be discussed in the next section.
Nitrogen  losses associated with surface  erosion
(i.e., adsorbed  nitrogen) may be estimated  using
the  insoluble component  model  previously
presented.
                                              X.19

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Nitrification And Mineralization

  The acid-base relations associated with nitrifica-
tion and mineralization are shown in figure X.A.3.
Acidity of the system remains unchanged as long as
plant  uptake  of nitrogen  equals  the  rate  of
mineralization  of nitrogen and neither NH1 nor
NOs accumulates in the soil.
  When mineralization  occurs followed by
nitrification, an excess of hydrogen ions (H+) is
released, which may replace cations on the ex-
change  sites. If plant  uptake of nitrate does not
take place, both nitrate ions and metallic cations
are subject to  leaching by subsurface flow.  Bor-
mann   and Likens (1970)  found  that  excess
hydrogen ions may be released from exchange sites
and go into solution in soil water, and are thereby
lost from the forest ecosystem. The result is an in-
creased  outflux  potential  of  nutrients  from
deforested watersheds  that  have  increased
nitrification rates.  They reported that increased
concentrations  of calcium,  magnesium, sodium,
and potassium in water draining a clearcut oc-
curred  almost  simultaneously  with  increased
nitrate concentration.
  Nitrate, an end product of nitrification reactions
of the intercycle stage,  is the principal component
of  nitrogen outflux from  the forest  ecosystem.
Increased biological nitrification  may result from
silvicultural activities  that reduce the  vegetative
cover, thus resulting in increased soil temperatures
and moisture.
  Accelerated  nitrogen losses  following  some
silvicultural  activities  have  generally been at-
tributed to changes in the forest floor environment
conducive to nitrifying  bacteria and to a reduction
in assimilation due to the reduced vegetative cover.
  Microbial  populations  in  the  forest  floor
generally increase following a timber harvest that
exposes the  soil to increased  radiation,  which
results in warmer soil temperatures. Little decom-
position takes place during the period when the soil
is frozen or covered with snow. Thus, temperature
of the  growing  season  appears to be the decisive
factor (Johnsen 1953, and Mikola 1960). The poten-
tial increase in nitrification rates is greater in the
northern climates, where thick humus  layers ac-
cumulate on the mineral soils and temperatures of
shaded  soils remain low most of the year  (Stone
1973).
  Soil   moisture  also  influences  the  growth  of
microbial  populations:  removal of the overstory
vegetation  reduces interception and transpiration
losses which results in increased soil  moisture.
Saturated  soils,  however, may retard microbial
growth and thus reduce nitrification rates.
  If nitrification and plant uptake of ammonium
ions are less than the rate of mineralization, am-
monium accumulates in the soil (fig. X.A.3). Am-
monium ions are adsorbed on cation exchange sites
and are not readily leached.  Clay soils and soils
with high  cation exchange  capacities  hold am-
monium ions most efficiently. Leaching of NH^ oc-
curs in soils with higher pH and lower  cation ex-
change capacity (Coffee and Bartholomew 1964).
  Denitrification.  —  Denitrification, the
biochemical reduction of  nitrate and/or nitrite, is
one possible route  whereby nitrogen may be lost
from the forest ecosystem — microorganisms may
reduce the nitrate and/or  nitrite forms of nitrogen
to gaseous nitrogen, and in some cases these forms
are reduced to ammonia. Denitrification will occur
in any microbial microenvironment that is essen-
tially anaerobic. The  microorganisms utilize the
nitrogen  oxides  as a source  of  oxygen in the
presence of glucose and  phosphate. The rate  of
denitrification  is  partially  controlled by  pH.
Denitrifying microorganisms are active in soils that
range in pH from 5.8 to 9.2 (with an optimal value
between pH 7.0 and 8.2).
  Many  commercial  forest  lands have soil pH
values  below  5.8 and   are  normally aerobic;
therefore  denitrification  is  severely limited,  if
detectable  at all (Lutz and Chandler  1961, and
Keeney 1973).

             Phosphorus Outflux

  Phosphorus is lost from the forest ecosystem in
surface and subsurface water, and in  vegetation
removed from  the site  during silvicultural  ac-
tivities. Water quality is affected only by
phosphorus lost from the site and entering the
stream. Phosphorus loss  via water transport in-
cludes not only the phosphorus dissolved in water,
but also that adsorbed to suspended solids.
  Generally, the greatest loss of phosphorus from a
forest will occur as insoluble phosphorus  complexes
adsorbed  on the  clay-sized  materials that  are
transported by  surface flow.  Research  investiga-
tions  (app.  X.B.)  have  generally  not reported
significant increases in phosphorus concentrations
in the receiving streams following  silvicultural ac-
tivities. It would appear that increases in available
phosphorus due to  silvicultural activities are nor-
mally utilized or fixed, and only a  small fraction is
transported from the site to a watercourse in the
absence of excessive erosion.
                                               X.20

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                                     APPENDIX X.B:

               EIGHTEEN STUDIES OF NUTRIENT RELEASES FOLLOWING
                               SILVICULTURAL ACTIVITIES
  The  results of research investigations into
nutrient release of nitrogen and phosphorus follow-
ing silvicultural  activities  are summarized  and
presented in figure X.2. A more thorough presenta-
tion  of the  results  of  these investigations  is
presented in  the following 18 studies.
  The  Hubbard  Brook study  initiated concern
regarding nutrient release  following  clearcutting
and is presented first  (study X.B.I.).  It should be
noted  that  the  treatment was extreme. The
NOa-N and NHt-N concentrations were greater
in the precipitation than in the streams draining
the control watersheds.
  Concentrations of nitrogen and phosphorus in
the control watersheds may be used as estimates of
baseline water quality for the various geographic
areas studied. It should be realized, however, that
there may be considerable variation between adja-
cent watersheds  as  well as between geographic
areas.
                                             X.21

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                              Study X.B.I
                   Hubbard Brook Experimental Forest,
                             New Hampshire
Silvicultural        Watershed 2 had all trees and brush cut (but left in place)
  treatment:        during November and December 1965, and herbicides were
                   applied during  the following three summers  to  inhibit
                   regrowth. Watersheds 4 and 6 were undisturbed and were
                   used as controls.

Vegetation:         Northern hardwoods — beech, birch, and maple.

Drainage:          Treated, Watershed 2, 39 ac (15.6 ha).
                   Control, Watershed 4,  90 ac (36 ha).
                   Control, Watershed 6,  33 ac (13.2 ha).

Sampling:          October 1965-September 1968.
Results:   	

      Study and          NOs-N       NHJ-N           Total dissolved P
        year          Mean annual   Mean annual     Maximum     Mean annual
                   	mg/l	
Watershed 2
1965-66
1966-67
1967-68
Watershed 4
1965-66
1966-67
Watershed 6
1965-66
1966-67
1967-68
Precipitation
1 965-66
1966-67
1967-68

0.21
8.67
11.94

0.19
0.20

0.19
0.16
0.29

0.32
0.34
0.35

0.11
0.05
0.04

0.09
0.05

0.09
0.04
0.02

0.16
0.14
0.17

...
... —
0.0026 0.00156

... ...
...

... —
... ...
0.00118

... ...
... ...
_.
Sources: Likens and others 1970; Hobble and Likens 1973.
                                  X.22

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                                Study X.B.2
                    Hubbard Brook Experimental Forest,
                              New Hampshire
Silvicultural        Progressive strip cutting. A 90  ac  (36 ha) watershed was
  treatment:        divided into 49 east-west strips, each 82 ft (25 m) wide.
                    Every third strip was clearcut in October 1970. The remain-
                    ing strips are cut at 2-year intervals.

Vegetation:         Uneven-aged northern  hardwoods — beech,  birch, and
                    maple.

Drainage:           Treated, Watershed 4, 90 ac (36 ha).

Sampling:          January 1968-September 1972.
Results:
NO3-N
Average concentration

Date

November 1970
December 1970
January 1971
February 1971
March 1971
April 1971
May 1971
June 1971
July 1971
August 1971
September 1971
October 1971
Estimated
(if untreated)
	 mg/l
0.43
0.50
0.61
0.6B
0.70
0.86
0.52
0.16
0.11
0.04
0.02
0.02
Actual


0.56
0.70
0.74
0.79
0.88
1.24
0.77
0.25
0.25
0.34
0.43
1.15

Date

November 1971
December 1971
January 1972
February 1972
March 1972
April 1972
May 1972
June 1972
July 1972
August 1972
September 1972

NO~3-N
Average concentration
Estimated
(if untreated)
	 mg/l
0.11
0.13
0.38
0.36
0.61
0.72
0.61
0.09
0.07
0.11
0.02

Actual

	
1.54
1.76
1.72
1.44
2.08
1.90
1.72
0.72
0.56
0.63
0.47

  1No noticeable change in NH1 concentration between treated and control watersheds.
Source: Hornbeck and others 1973.
                                    X.23

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Silvicultural
  treatment:
    Church Pond:

    Conner Brook:

    Davis Brook:


    D.O.C. Creek:

    Gale River:


    Greeley Brook:


    HB 101:

    Stony Brook:


Vegetation:
           Study X.B.3
 White Mountain National Forest,
          New Hampshire


Timber sales conducted on the White Mountain National
Forest. All areas were clearcut; more than 75 percent of the
timber was cut. Adjacent undisturbed watersheds were also
monitored.
Clearcut in summer 1969,  329 ac (133 ha); 10 ac (4 ha);
watershed monitored.
Clearcut in May 1969-Dec.  1969, 282 ac (114 ha); three 20
ac (8 ha) watersheds were monitored.
Clearcut Sept.  1969-Sep   1970,  160  ac (65 ha);  three
watersheds were monitored  — 2.5 ac (1 ha), 7 ac (3 ha), 10
ac (4 ha).
Clearcut July 1970, 126 ac  (55 ha); two 20 ac (8 ha)
watersheds were monitored.
Clearcut Dec.  1968-Aug.  1970,  297 ac  (120 ha);  three
watersheds were monitored — two 10 ac (4 ha) and one 5 ac
(2 ha).
Clearcut initially 1960 and again 1967, 371 ac  (150 ha);
three watersheds were monitored — 35 ac (14 ha), 10 ac (4
ha) and 5 ac (2 ha).
Clearcut Nov. 1970, 30 ac (12 ha); 25 ac (10 ha) watershed
monitored.
Clearcut Nov. 1968-May 1970, 160 ac (65 ha);  10 ac (4 ha)
watershed monitored.

Northern hardwoods (beech, birch, and maple)  were pre-
sent on all  areas except Greeley  Brook  which  had
predominantly red spruce.
Drainage:
Sampling:
Results:
Watershed
Church Pond
Control
Clearcut
Conner Brook
Control
Davis Brook
Control
Clearcut
D.O.C. Creek
Control
Clearcut
See "Silvicultural
Biweekly

NO3-N
Max
	 mg/l -
0.95
1.60
0.40
0.09
5.26
1.22
3.54
analysis

Mean
0.81
1.40
0.20
0.02
3.84
0.52
1.90
treatment," above.
from April-November

Watershed
Gale River
Control
Clearcut
Greeley Brook
Control
Clearcut
Stony Brook
Control
Clearcut


1971.

Max
0.50
6.39
0.79
1.85
0.81
3.73




NOa-N
Mean
--mg/l 	
0.20
4.47
0.54
1.31
0.18
1.99

Source: Pierce and others 1972.
                                  X.24

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                              Study X.B.4
                     White Mountain National Forest,
                    Upper Mill Brook, New Hampshire
 Silvicultural       Harvesting operations were conducted on the Upper Mill
   treatment:       Brook sale area from December 1971-February 1973
        Watershed
           No.

            1
            2
            3
            4
            5

            6
            8
            9
            C
              Date
         Jan.-Feb. 1972
        Feb.-Mar. 1972
    Dec. 1971-Jan. 1972
    Dec. 1971-Jan. 1972
       June-Sept. 1972

   Sept. 1972-Feb.1973
 Treatment and
  drainage area

Thinning (10-20 ac)
Thinning (10-20 ac)
Clearcut( 10-20 ac)
Clearcut (20-30 ac)
Clearcut with buffer
    (10-20 ac)
Clearcut (10-20 ac)
Control (30-40 ac)
Control (20-30 ac)
Control (620 ac)
Vegetation:

Drainage:

Sampling:
Northern hardwoods.

See "Silvicultural treatment," above.

1972-1974, 10 to 12 samples per year were collected. This
number of samples was based on previous data evaluations.
Results
Watershed and
treatment

1 and 2— thinnings
3— Clearcut
4— clearcut
5— clearcut/buffer
6— clearcut
8 and 9— controls
C— control (upstream)
NOa-N
Mean

0.45
0.79
0.96
0.39
0.23
0.23
0.27
NO3-N
Max

2.10
2.55
2.48
1.51
1.35
1.21
1.02
Total N
Mean

0.92
1.32
1.50
0.94
0.81
0.71
0.67
Total N
Max
mn/l --------

2.50
3.55
3.40
2.92
4.10
2.88
4.20
POs3
Mean

0.02
0.03
0.02
0.02
0.02
0.02
0.01
PO43
Max

0.11
0.13
0.09
0.09
0.16
0.12
0.04
Source: Stuart and Dunshie 1976.
                                 X.25

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                                Study X.B.5
                        Leading Ridge Watershed 2,
                       Pennsylvania State University
Silvi cultural
  treatment:
Vegetation:

Drainage:
Sampling:
Forty-six percent of the watershed was successively clear-
cut and herbicided.  The  sequence of operation was (1)
winter of 1966-67—21.3 ac (9 ha) of the lower watershed
were  clearcut; (2)  summers of  1967, 1968, and 1969 —
stumps were treated  with herbicide to  control stump
sprouting;  (3) winter of 1971-72 — 2.70 ac (1.0 ha) of the
middle watershed were clearcut; and (4)  both clearcuts
treated with herbicide in June 1974.

Uneven-aged oak, hickory,  and maple.

Treatment, Leading Ridge Watershed (LR) 2,106 ac (42 ha)
with 48.3 ac clearcut.
Control, Leading Ridge Watershed 1,  303 ac (121 ha).
Control, Leading Ridge Watershed 3,  257 ac (100 ha).

Weekly sampling for nutrient concentrations in streamflow
began in 1972.
Results:
Date



Control
LR-1


Treatment
LR-2
NOa-N
	 mn/l 	
Control
LR-3


Oct. 1972-Sept. 1973
Oct. 1973-May 1974
June1974-Dec. 1974
June-Aug. (ave max)
Sept.-Dec. (ave max)
Sept.-Dec. (max measured)
                   Clearcutting had no apparent effect
                0.02            0.10            0.01
                0.04            2.08            0.08
                               0.4
                               5.0
                               8.4
Source: Corbett and others 1975.
                                  X.26

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                               Study X.B.6
                       Fernow Experimental Forest,
                               West Virginia
Silvicultural        Watershed 3 was clearcut  1969.  Watershed  4 was  un-
  treatment:        disturbed and used as a control. Watershed 2 was subjected
                    to a diameter-limit cut in August 1972.

Vegetation:         Mixed deciduous — oaks, maples, yellow poplar,  black
                    cherry and beech.

Drainage:           Watershed 3, 84 ac (34 ha).
                    Watershed 4, 94 ac (38 ha).
                    Watershed 2, 38 ac (15 ha).

Sampling:           Weekly  sampling,  May  1970-April  1971,  Watersheds  3
                    and 4.
                    Weekly sampling, Aug. 1972-Sept. 1974, Watershed 2.
Results:
Watershed
Watershed 4
1970 growing season
1970-71 dormant season
Watershed 3
1970 growing season
1970-71 dormant season
Watershed 2
Growing season
Pre-silvicultural activity
Post-silvicultural activity
Dormant season
Pre-silvlcultural activity
Post-sllvicultural activity

NOa-N NHJ-N
Mean Max Mean
0.32 — 0.48
0.10 — 0.13
0.1 B 0.59 0.35
0.49 1.42 0.14
0.2
0.6
Values unchanged
Values unchanged

PO43
Ave
0.04
0.02
0.07
0.04

Sources: Aubertin and Patric 1972; Aubertin and Patric 1974; Patric and Aubertin 1976.
                                   X.27

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                               Study X.B.7
                      Coweeta Hydrologic Laboratory,
                              North Carolina
Silvicultural treatment:
    Watershed
        No.
         1

         2
         6
        14
        13

        18
        17
        21
        28
        32
        37

        34

Vegetation:

Drainage:

Sampling:
All trees and shrubs cut 1956-57,  no products removed;
white pine planted 1957, 40 ac (16.2 ha).
Control, mixed mature hardwoods, 30 ac (12.1 ha).
Cut 1958 and products removed; lime added, fertilized, and
grassed in  1959; refertilized 1965; herbicided 1966 and 67,
22 ac (8.9 ha).
Control, mixed mature hardwoods, 151 ac (61.1 ha).
All trees and shrubs  cut  1936, recut 1962; no products
removed, 40  ac (16.2 ha).
Control, mixed mature hardwoods, 31 ac (12.5 ha).
All trees and shrubs cut 1942; recut annually through 1955,
no  products  removed; white pine planted in 1956, 33  ac
(13.4 ha).
Control, mixed mature hardwoods, 60 ac (24.3 ha).
All trees and shrubs cut on 190 ac (77 ha); cove hardwoods
thinned on 96 ac (39 ha); no cutting on 69 ac (28 ha);
products removed 356 ac (144.1 ha).
Control, mixed mature hardwoods, 102 ac (41.3 ha).
All trees and shrubs cut in  1963; no products removed, 108
ac (43.7 ha).
Control mixed mature hardwoods 81  ac  (32.8 ha).

See "Silvicultural treatment," above.

See "Silvicultural treatment," above.

May 1972-April 1973.
Results:
Watershed1

1
2
6
14
13
18
17
21
28
32
37
34

NOa-N
Mean

0.029
0.004
0.619
0.004
0.044
0.003
0.154
0.003
0.094
0.003
0.149
0.002

Max

0.077
0.017
1.230
0.024
0.084
0.014
0.249
0.016
0.208
0.015
0.246
0.019

NHJ-N
Mean
	 rng/| -
0.003
0.002
0.004
0.004
0.003
0.004
0.004
0.004
0.003
0.003
0.004
0.003

Max

0.020
0.020
0.010
0.031
0.014
0.022
0.012
0.024
0.017
0.013
0.038
0.024

PO
Mean

0.006
0.006
0.007
0.005
0.004
0.005
0.012
0.004
0.004
0.004
0.006
0.006

43-P
Max

0.022
0.020
0.030
0.017
0.013
0.018
0.336
0.029
0.020
0.013
0.095
0.019
  'Watersheds listed  below are alternated treated and controlled (1—treated, 2—control) for com-
parison. Refer to "Silvicultural treatment" for details.
Sources: Douglass and Swank 1975; Swank and Douglass 1975.
                                   X.28

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                               Study X.B.8
                      USAEC's Savannah River Plant,
                           Aiken, South Carolina


Silvicultural        Prescribed burn of surface litter.
  treatment:

Vegetation:         Loblolly pine.

Drainage:           Approximately 450 ac (180 ha).

Sampling:          Ground water samples were taken at control and burned
                    areas 5 weeks after burn.


Results: Ground water.

  Sample                           NOs-N                   PO33-P
    area                      Mean          Std         Mean         Std
                                          error                     error
                         	mg/l  	
Burned                       0.007        0.0005        0.0047        0.0012
Control	0.006	0.0009	0.0040	0.0010

Source: Lewis 1974.
                                   X.29

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                                Study X.B.9
                           Grant Memorial Forest,
                                   Georgia
Silvicultural         77 ac were clearcut beginning in October 1974. Harvesting
  treatment:         and site  preparation (roller chopping)  was completed in
                     December 1975. The site was planted in January 1976. An
                     adjacent  untreated watershed was monitored as a control.

Vegetation:          Old field Loblolly pine.

Sampling:           December 1973-January 1977  (approximately  200 weekly
                     samples).
Results: (Mean cone, of all samples)
                   Watershed
NOa-N
                                                            mg/l
                                                                   Total P
Treated
Calibration, Dec. 1973-Oct. 1974
Harvest and site prep., Nov. 1974-Dec. 1975
Following planting, Jan. 1976- Jan. 1977
Control
Calibration, Dec. 1973-Oct 1974
Nov. 1974-Dec. 1975
Jan. 1976-Jan. 1977

0.058
0.029
0.028

0.149
0.113
0.108

0.210
0.190
'0.476

0.216
0.230
'0.582
  'Particularly high values of phosphorus occurred during September-October 1976. Although unex-
plained, it is important to note that both the treated and the control watersheds exhibited high values dur-
ing this period.
Source: Hewlett 1977.
                                    X.30

-------
 Silvicultural
   treatment:
Vegetation:

Drainage:
                                 Study X.B.10
                      H. J. Andrews Experimental Forest,
                                Eugene, Oregon
Patchcut using high-lead yarding;  with 25 percent of the
area cut, plus an additional 6 percent in roads. Clearcut en-
tire drainage, but no roads were present. Harvesting opera-
tions were begun in the fall of 1962 and were completed in
1966. Both areas were broadcast burned following yarding.
A third drainage was undisturbed and served as a control.

Old-growth Douglas fir.

Patchcut,  237 ac (96 ha).
Clearcut, 149 ac (60 ha).
Control, 250 ac (101 ha).
Sampling:
Results:
Date and
treatment
1966 (H)<
1967 (B)
1968 (R)
1971 (R)
1972 (R)
119 samples were collected, usually during storm runoff,
during the period April 1965-July 1968.
N<
Mean
annual
0.020
0.050
0.200
0.046
0.023
Clearcut
Instan-
taneous
max
0.050
0.066 0.110
0.600 0.001
0.065
0.056
PO4a
Mean
annual
0.024
0.039
0.036
0.034
'-P
Instan-
taneous
max
0.066
0.121
0.050
0.045
  Measurement

Maximum
12-day mean
              Maximum and mean maximum taken during a 12-day period
                           after broadcast burning in 1967
                        NOs-N               NHJ-N              PO43-P
                  Clearcut    Control    Clearcut    Control  Clearcut      Control
                                              mg/l
                   0.60
                   0.43
        0.01
7.60
1.19
0.001
0.13
0.05
0.05
                                    Patchcut
Dissolved solids concentration Increased as a result of harvesting. The effect lasted for 6 years and
was no longer statistically different from the pre-sllvlcultural activity In 1968.
                        NOl-N
                              Instan-
                                     Control
                                          PO^'-P
                                                Instan-
Date and
treatment


1966 (U)
1967 (U)
1968 (U)
1971 (U)
1972 (U)
Mean
annual


0.010
0.003
0.001
0.0003
0.0015
taneous
max NHJ-N
	 mn/l 	

... ...
0.003
<0.001
—
—
Mean
annual


0.026
0.016
—
0.032
0.016
taneous
max


...
—
—
—
—
  'H  = harvested, B = burned, R  = revegetating, and U =  undisturbed.
Source: Fredriksen 1971; Fredriksen 1977; Fredriksen and others 1975; Rothacher and others 1967.
                                     X.31

-------
      Silvicultural
        treatment:
      Vegetation:

      Drainage:



      Sampling:
                                     Study X.B.ll
                                 Bull Run Watershed,
                                   Portland, Oregon
Clearcut on 25 percent of watersheds — the slash on one
was burned and  left to decompose  on the other. On the
burned watershed, harvesting was done the summer of 1969
and the slash was burned in the fall of 1970. On the un-
burned watershed,  two seasons (1971 and 1972) were re-
quired to completely fell the units; harvesting was com-
pleted summer of 1973. The untreated watershed served as
a control.

Old-growth Douglas fir.

Fox Creek: Clearcut and burned, 145 ac  (59 ha).
           Clearcut and not burned,  175 ac  (71  ha).
           Control, 625 ac (253 ha).

Sampling began  April  1970. Proportional samples taken
over 3-week intervals throughout each year.
Results:
                                         Clearcut
   Year and
   treatment
1970 (H)1
1971 (B)
1972 (R)
1973 (R)
1974 (R)
1975 (R)
1976 (R)
Dissolved
NOs-N
Mean
annual


0.012
0.027
0.046
0.034
0.045
0.023
—
Max



0.019
0.079
0.056
0.057
0.064
0.034
0.033
NHt-N
Mean
annual


0.003
0.005
0.001
0.001
—
—
—
Max



0.020
0.100
0.022
0.090
—
...
—
organic N
Mean
annual
	 it
- - mg/i 	
0.037
0.036
0.040
0.036
0.043
0.043
—
Max



0.058
0.049
0.062
0.058
0.133
0.075
0.051
Total
phosphorus
Mean
annual


0.035
0.027
0.014
0.028
0.011
0.016
—
Max



0.065
0.055
0.030
0.100
0.093
0.032
0.025
                                   Clearcut—Not Burned
1970 (U)
1971 (F)
1972 (F)
1973 (H)
1974 (R)
1975 (R)
1976 (R)

1970 (U)
1971 (U)
1972 (U)
1973 (U)
1974 (U)
1975 (U)
1976 (U)
0.002
0.004
0.014
0.022
0.080
0.093
—

0.006
0.003
0.005
0.013
0.002
0.002
—
0.014
0.017
0.030
0.042
0.115
0.114
0.066

0.027
0.020
0.040
0.056
0.053
0.028
0.040
0.002
0.005
0.001
0.003
—
—
...

0.005
0.004
0.002
0.002
—
—
—
0.005
0.089
0.010
0.036
—
—
—
Control
0.013
0.078
0.018
0.007
—
...
—
0.036
0.038
0.029
0.032
0.032
0.044
—

0.045
0.043
0.036
0.038
0.034
0.050
—
0.078
0.096
0.046
0.042
0.082
0.076
0.066

0.063
0.064
0.070
0.062
0.081
0.068
0.065
0.028
0.032
0.013
0.021
0.011
0.020
—

0.040
0.032
0.014
0.024
0.013
0.015
—
0.070
0.055
0.045
0.030
0.062
0.046
0.030

0.065
0.070
0.080
0.100
0.090
0.033
0.031
  'H = harvested; B = burned; F = felled; R = revegetating, and U = undisturbed
Source: Fredriksen 1977.
                                         X.32

-------
                                     Study X.B.12
                          South Umpqua Experimental Forest,
                          50 kilometers ESE of Rosberg, Oregon
       Silvicultural        Shelterwood harvest —  50  percent of the area removed;
         treatment:        small clearcut — 30 percent of the area in 20 small clearcuts
                          from  0.6 - 1.4 ha  (3.1 ac);  complete clearcut — all trees
                          removed. Logging residue on watersheds was piled and
                          burned. Roads were constructed June-September 1970 and
                          harvesting done June-September 1971.

       Vegetation:         Mixed conifer.

       Drainage:           Coyote  Creek:  Shelterwood, 171 ac (69 ha).
                                         Complete clearcut, 123 ac (50 ha).
                                         Small clearcut, 169 ac (68 ha).
                                         Control, 120 ac (49 ha).

       Sampling:          Sampling began October 1, 1969. Proportional samples
                          taken over 3-week intervals throughout each year.
Results:
Shelterwood
Disolved
NOs-N
Year and
treatment

1970
1971
1972
1973
1974
1975

(U)<
(RC)
(H)
(R)
(R)
(R)
mean
annual
IT
0.001
0.002
0.004
0.003
0.001
0.004
max

ig/l
0.005
0.016
0.012
0.033
0.017
0.019
NH4-N
mean
annual
mg/l
0.002
0.002
0.003
0.005


max


0.027
0.010
0.009
0.015


organic N
mean
annual
mg/l
0.077
0.048
0.075
0.039
0.051
0.067
max


0.165
0.126
0.114
0.060
0.155
0.151
Total-P
mean
annual

0.032
0.052
0.043
0.048
0.030
0.038
max

mg/l
0.080
0.090
0.095
0.115
0.076
0.069
Ortho-P
mean
annual

0.015
0.020
0.026
0.014
0.015
0.016
max

mg/l
0.030
0.033
0.070
0.090
0.021
0.021
Complete Clearcut
1970
1971
1972
1973
1974
1975
(U)
(U)
(H)
(R)
(R)
(R)
0.001
0.005
0.002
0.126
0.242
0.275
0.009
0.018
0.007
0.178
0.365
0.510
0.001
0.002
0.003
0.018


0.020
0.010
0.008
0.043


0.093
0.064
0.080
0.084
0.104
0.123
0.142
0.132
0.178
0.252
0.176
0.161
0.048
0.086
0.062
0.100
0.068
0.091
0.150
0.133
0.140
0.205
0.130
0.148
0.048
0.051
0.054
0.064
0.054
0.060
0.100
0.115
0.062
0.112
0.082
0.092
Small Clearcut
1970
1971
1972
1973
1974
1975

1970
1971
1972
1973
1974
1975
(F)
(RC)
(H)
(R)
(R)
(R)

(U)
(U)
(U)
(U)
(U)
(U)
0.003
0.055
0.004
0.026
0.007
0.019

0.001
0.005
0.003
0.002
0.004
0.004
0.022
0.177
0.031
0.120
0.087
0.059

0.004
0.025
0.005
0.034
0.022
0.034
0.003
0.001
0.001
0.009



0.001
0.003
0.002
0.014


0.031
0.004
0.005
0.034



0.006
0.012
0.006
0.061


0.105
0.073
0.081
0.056
0.070
0.084
Control
0.105
0.058
0.078
0.124
0.072
0.089
0.149
0.142
0.120
0.142
0.138
0.121

0.185
0.133
0.095
0.057
0.132
0.137
0.034
0.032
0.035
0.038
0.023
0.034

0.036
0.060
0.045
0.053
0.036
0.049
0.090
0.049
0.070
0.090
0.058
0.077

0.118
0.200
0.080
0.110
0.069
0.071
0.016
0.013
0.031
0.011
0.011
0.011

0.025
0.029
0.039
0.025
0.024
0.024
0.038
0.026
0.045
0.021
0.018
0.022

0.060
0.114
0.045
0.045
0.033
0.026
  1U-undisturbed, F-fertilized, H-harvest, RC-road construction R-revegetating
Source: Fredriksen 1977.
                                        X.33

-------
Silvi cultural
  treatment:
Vegetation:



Drainage:



Sampling:

Results:
                              Study X.B.13
                     Alsea Basin, Oregon Coast Range
Needle  Branch was completely  clearcut  beginning in
March 1966; logging slash was burned (very hot fire) in Oc-
tober 1966. Deer Creek was 25 percent clearcut in three log-
ging units. Only one unit in Deer Creek was burned (light
burn). Flynn Creek remained untreated and served as the
control.

Douglas fir and alder. Alder was predominant species on
Flynn Creek (68%)  and Deer  Creek (68%). Douglas fir
predominated on Needle Branch (80%).

Needle Branch, 175 ac (70.68 ha).
Deer Creek, 750 ac (303.32 ha).
Flynn Creek, 500 ac (203.14 ha).

2 years before and 2 years after  logging.

Watershed
and treatment

Needle Branch
Clearcut


Deer Creek1
Patchcut


Flynn Creek1
Control



Water
year

1965
1966
1967
1968
1965
1966
1967
1968
1965
1966
1967
1968
NOa
Max
observed


0.20
0.70
2.10
1.65
3.17
2.10
2.70
2.40
3.19
2.18
2.70
2.20
	 U
Yearly
mean

	 mg/i -
0.12
0.19
0.44
0.43
1.12
0.98
1.21
1.12
1.21
1.16
1.18
1.18
Total phosphate P

Min


0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01

Max


0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
  1Migh nitrate-N values probably due to alder.

  Source: Brown and others 1973.
                                  X.34

-------
Silvicultural
  treatment:
Vegetation:


Drainage:
                              Study X.B.14
                        Bitterroot National Forest,
                                Montana
Three watersheds  were  clearcut  and  three paired
watersheds were used as controls. Lodgepole Creek was 97
percent clearcut, most of it in 1969 and 1970. Mink Creek
was 83 percent clearcut in 1968 and dozer piled in 1971. The
lower 46 percent of Little Mink Creek was clearcut in 1963,
dozer piled in 1971, burned in 1972, and planted in 1973.

Mixed coniferous,  ponderosa pine, Douglas fir, lodgepole
pine,  Engelmann spruce, and  subalpine fir.

1. Lodgepole Creek,  treatment, 497 ac (201 ha).
1. Spruce Creek, control, 467 ac (189 ha).
2. Mink Creek, treatment, 614 ac (249 ha).
2. Springer Creek, control, 866 ac (350 ha).
3. Little Mink Creek, treatment, 103 ac (41 ha).
3. Little Mink Creek, control, 152 ac (61 ha).
Sampling:
Results:
Watershed
1. Lodgepole Creek
1. Spruce Creek
2. Mink Creek
One year from October

NOa-N
Mean annual
mg/l
0.19
0.11
0.17
1,


2.
3.
3.
1972-September

Watershed
Springer Creek
Little Mink Creek
Little Mink Creek
30, 1973.

NO3-N
Mean annual
mg/l
0.13
0.40
0.17
Source: Bateridge 1974.
                                  X.35

-------
                               Study X.B.I5
                     Priest River Experimental Forest,
                                  Idaho
Silvicultural         Three watersheds were treated. Benton Creek was clearcut
  treatment:         in 1969, with a waterside area remaining along stream, and
                    broadcast burned in 1970. Ida Creek was clearcut in 1970.
                    with waterside area,  and the  slash was  windrowed and
                    burned. Canyon Creek was also clearcut with a waterside
                    area, and broadcast burned.

Vegetation:          Mixed conifers, western white  pine, western  red  cedar,
                    Douglas fir, and western larch.

Drainage:           Not defined.

Sampling:           Benton Creek, September 1970 to June 1972.
                    Ida  Creek, October 1970 to June 1972.

Sampling was done above  and below the silvicultural operation.
Results:

Watershed
Benton
Control
Treatment
Ida
Control
Treatment
-NO:

Mean
0.20
0.18
0.14
0.16
i 
-------
                                     Study X.B.16
                              Marcell Experimental Forest,
                                       Minnesota
      Silvicultural        62.5 ac of aspen uplands were clearcut between December
        treatment:        1970 and January  1972.

      Vegetation:         Aspen/birch and black spruce (bog).

      Drainage:           Treatment, 84 ac (34 ha).
                          Control, 130 ac (52 ha).

      Sampling:          Pre-silvicultural activity samples (9)  were taken  in the
                          spring, summer and fall. Post-silvicultural activity sampl-
                          ing (26 samples) was concentrated during high flows.
Results:
 Sampling
  Organic -N
        Std
Mean    error
                             Mean
NH4 -N
     Std
     error
    NCh N
         Std
 Mean   error
	mg/l	
                                                            Mean
Total -N
      Std
     error
                                                                           Mean
Total P0«
      Std
      error
Silvicultural-
activity
Pre-
Post-
Control
Pre-
Post-


0.93
0.80

0.92
0.85


0.19
0.07

0.16
0.07


0.35
0.55

0.25
0.41


0.10
0.11

0.03
0.06


0.31
0.16

0.30
0.12


0.12
0.06

0.10
0.01


1.69
1.50

1.48
1.39


0.18
0.13

0.14
0.07


0.15
0.17

0.13
0.12


0.03
0.03

0.01
0.02
Source: Verry 1972.
                                          X.37

-------
                              Study X.B. 17
                          West Central Alberta,
                                 Canada
Silvicultural         Clearcutting progressively over 13 forest watersheds located
  treatment:         in 3 working circles (management units).

Vegetation:          Lodgepole pine, white spruce, and aspen.

Drainage:           Ranged in size from 1,725 to 5,914 acres (700 to 2,400 ha).

Sampling:           Summer 1974, 117 samples during spring snowmelt and 104
                    samples during summer recession period.
Results:

Marlboro Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
Berland Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
McLeod Circle
2 controls May-June
July-Aug.
2 treated May-June
July-Aug.
Source: Singh and Kalra 1975.
Nl
Mean

0.52
0.22
0.68
0.18

0.39
0.10
0.34
0.09

0.48
0.20
0.48
0.22

n;
Std
error

0.07
0.03
0.09
0.02

0.05
0.01
0.06
0.02

0.03
0.03
0.03
0.03

N
Mean
• 	 m(
0.04
0.006
0.02
0.006

0.011
0.004
0.047
0.028

0.010
0.008
0.016
0.005

03
Std
error
-./i
3'1 	
0.02
0.0002
0.01
0.001

0.003
0.001
0.009
0.004

0.002
0.002
0.003
0.001

PO.
Mean

0.011
0.007
0.012
0.008

0.010
0.005
0.008
0.004

0.012
0.006
0.009
0.005

•3-P
Std
error

0.001
0.001
0.001
0.001

0.001
0.003
0.0005
0.0001

0.001
0.0003
0.001
0.0005

                                  X.38

-------
                                    Study X.B.18
                           Dennis Creek,  Okanagan Valley,
                                   British Columbia
      Silvicultural         Clear-cutting 383 ac (155 ha) representing about 25 percent
        treatment:         of the drainage area.

      Vegetation:          Engelmann spruce-subalpine fir.

      Drainage:           Dennis Creek treatment, 2,370 ac (960 ha).
                          James Creek control, 2,000 ac (810  ha).

      Sampling:           Sampling was done at two sites each above and below the
                          silvicultural  operation  and  on an  adjacent  undisturbed
                          watershed.
Results:
Total
Kjeldahl nitrogen
Min Mean Max
Below cut
Sitel
Site 2
Above cut
Site 1
Site 2
Control
Sitel
Site 2
Source: Hetherington
0.090
0.090
0.095
0.095
0.100
0.100
1976.
0.189
0.242
0.166
0.191
0.308
0.328

0.351
0.596
0.346
0.418
0.448
0.467

Min
0.002
0.002
0.002
0.002
0.002
0.002

NO3-N
Mean
mg/l
0.003
0.028
0.004
0.010
0.015
0.029

Total phosphorus
Max Min Mean Max
0.010 0.005
0.368
0.013 0.002
0.050
0.040 0.014
0.124

0.015 0.038
0.010 0.031
0.028 0.056

                                        X.39

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              Chapter XI

INTRODUCED CHEMICALS
 this chapter was prepared by the following individuals:
            Duane G. Moore
             John B. Currier

         with major contributions from:
             Logan A. Norris
                 Xl.i

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                              CONTENTS
                                                                    Page

INTRODUCTION	   XI.l
DISCUSSION 	   XI.2
  MAGNITUDE AND SCOPE OF CHEMICAL USE	   XI.2
     Pesticides	   XI.2
     Fertilizers  	   XI.4
     Patterns Of Chemical Use  	   XI.4
       Insecticides	   XI.4
       Herbicides	   XI.5
       Fungicides	   XI.5
       Rodenticides	   XI.5
       Fertilizers  	   XI.5
    CONCEPTS OF HAZARD AND CHEMICAL ACTION	   XI.5
    CHEMICAL BEHAVIOR OF PESTICIDES	   XI.6
     Initial Distribution of Spray Materials	   XI.7
     Movement, Persistence, And Disposition of Pesticides	   XI.8
       Distribution In Air	   XI.8
       Distribution In Vegetation 	   XI.8
       Distribution On The Forest Floor And In Soil 	   XI.9
       Distribution In Surface Waters	   XI. 12
     Entry Of Pesticides Into The Aquatic Environment	   XL 12
       Movement To Streams From The Air	   XI. 12
       Movement To Streams From Vegetation 	   XI.13
       Movement To Streams From The Forest Floor And Soil	   XI. 13
       Summary Of Pesticide Entry Into The Aquatic Environment 	   XL 16
     Behavior In The Aquatic Environment	   XI. 16
       Volatilization 	   XL 16
       Adsorption	   XL 16
       Degradation 	   XL 17
       Downstream Movement	   XL 17
    CHEMICAL BEHAVIOR OF FERTILIZERS	   XI.18
     Initial Distribution In Air, Vegetation And Forest Floor  	   XI.18
     Entry Of Fertilizers Into The Aquatic Environment	   XI.18
       Summary of Fertilizer Entry Into The Aquatic Environment	   XL22
       Behavior In The Aquatic Environment	   XI.23

CONCLUSIONS 	   XI.24
LITERATURE CITED 	   XI.25
  APPENDIX A: WATER QUALITY DATA—PESTICIDE CHEMICALS .. .   XI.31
  APPENDIX B: WATER QUALITY DATA—FERTILIZER CHEMICALS ..   XI.43
  APPENDIX C: REFERENCE SOURCES FOR PESTICIDE CHEMICALS   XI.51
                                  Xl.ii

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                               LIST OF FIGURES
 Number                                                                   Page
 XI. 1.   —The interaction of chemicals with the environment	  XI. 6
 XI.2.   —The distribution and disposition of chemicals in the environment..  XI.7
 XI.3.   —Lateral movement of spray particles	  XI.7
 XI.4.   —Recovery of 2,4-D, amitrole, 2,4,5-T  and picloram from red alder
            forest floor material	   XI.10
 XI.5.   —Chemical adsorption in soil  is an equilibrium reaction	   XI. 10
 XI.6.   —Persistence of individual pesticides in soils	   XI. 11
 XI.7.   —Precipitation and herbicide runoff patterns at the Beacon Rock Study
            Area	   XI. 14
 XI.8.   —Relative mobility of pesticides leached in columns of soil 	   XI. 15
 XI.9.   —The degradation of 2,4-D in a bacterially active water culture	  XI. 17
 XI. 10.  —Coyote Creek  watersheds, South Umpqua Experimental Forest, Um-
            pquaNational Forest, Oregon	   XI. 19
 XI.11.  —Fertilization of a 68-ha watershed	   XI.21
 XI.A.l. —Cascade Creek Treatment Unit	   XI.31
 XI.A.2. —Eddyville Treatment Unit	   XI.32
 XI.A.3. —West Myrtle  Treatment Unit	   XI.32
 XI.A.4. —Camp Creek  Spray Unit 	   XI.33
 XI.A.5. —Keeney-Clark Meadow Spray Units	   XI.33
 XI.A.6. —Wildcat Creek Spray Unit	   XI.34
 XI.A.7. —Farmer Creek Treatment Watershed  	   XI.35
 XI.A.8. —Precipitation,  stream discharge, and concentrations of  tryclopyr in
            stream water following application of 3.36 kg/ha by helicopter to a
            small watershed  in southwest Oregon in May 1974	   XI.37
 XI.A.9. —Boyer Ranch,  southwest Oregon. Small 7-ha hill-pasture spray unit
            treated with Tordon 212	   XI.38
 XI.A.10.—Discharge of  herbicide in streamflow from small 7-ha hill-pasture
            watershed,  Boyer Ranch, southwest Oregon	   XI. 39
 XI.A. 11.—Concentration of endrin in streamflow after aerial seeding with
            endrin-coated Douglas-fir seed	   XI.40
XI.A.12.—Water yield and bromacil release from watershed 2, Hubbard Brook
            Experimental Forest, West Thornton,  N.H	   XI.41
XI.A.13.—Atrazine concentration in streamflow during and for SVz months after
            herbicide treatment	   XL42
                                     XLiii

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                               LIST OF TABLES
Number                                                                    Page
XI.1.   —Pesticide use in forests, July 1, 1975, to September 30, 1976	   XI.2
XI.2.   —Reported pesticides used for silviculture in the United States  	   XI.3
XI.3.   —Residues of herbicide in forage grass 	   XI.8
XI.4.   —Effect of slope, rate of application and movement over untreated sod
            on the concentration of picloram in runoff water	   XI. 13
XI.5.   —Concentration of fertilizer nitrogen in selected water samples	   XI.20
XI.6.   —Nitrogen lost from treated watershed 2 and untreated watershed 4
            during the first 9 weeks	   XI.20
XI.7.   —Nitrogen lost from treated watershed 2 and untreated watershed 4
            during the first year	   XI.21
XI.A.l. —Cascade Creek Unit, Alsea Basin,  western Oregon  	   XI.31
XI.A.2. —Eddyville Unit, Yaquina Basin,  western Oregon 	   XI.32
XI.A.3. —Concentration of 2,4-D in West Myrtle Creek, Malheur National
            Forest, eastern Oregon	   XI.32
XI.A.4. —Camp Creek Spray Unit, Malheur National Forest, eastern Oregon   XI.33
XI.A.5. —Concentration of 2,4-D in streams in Keeney-Clark Meadow,  eastern
            Oregon 	   XI.33
XI.A.6. —Concentration of Amitrole-T in Wildcat Creek, Coast Range, western
            Oregon 	   XI.34
XI.A.7. —Concentration of amitrole in stream  water, loss  or dilution with
            downstream movement. Amitrole-T applied to 105 ha at 2.24 kg/ha   XI.35
XI.A.8. —Concentration of dicamba in Farmer Creek	   XI.36
XI. A.9. —Concentrations of 2,4-D and picloram in drainage waters from a 7-ha
            hill-pasture watershed in southwest Oregon	   XI.38
XI.A.10.—Total DDT content of stream water flowing from sprayed area before
            treatment and for 3 years after treatment  	   XI.39
XI.A.11.—Concentration of herbicides in  water samples,  as determined by odor
            tests	   XI.40
XI.A.12.—Concentrations of 2,4-D and 2,4,5-T herbicide in water samples from
            Monroe Canyon, San Dimas Experimental Forest,  northeast of
            Glendora,  California 	   XI.41
XI.B.l. —Stream   water  quality  following forest  fertilization, fall  1975:
            Hoodsport-Quileene  Ranger Districts  Olympic National  Forest,
            Washington	   XI.43
XI.B.2. —Stream  water quality  following forest  fertilization,  spring  1975:
            Hoodsport-Quileene  Ranger Districts,  Olympic  National Forest,
            Washington	   XI.44
                                     XLiv

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                         LIST OF TABLES (Continued)
Number                                                                     Page

XI.B.3. —Stream water  quality  following  a  wildfire and fertilization with
            reseeding for erosion control, 1971: Entiat Experimental Forest,
            central Washington	   XI.45
XI.B.4. —Stream water  quality  following  forest fertilization,  1970:  Mitkof
            Island,  southeast Alaska	   XI.46
XI.B.5. —Stream water  quality  following  forest fertilization of  two small
            watersheds, 1970 and 1971: Siuslaw River Basin,  western Oregon   XI.46
XI.B.6. —Stream water quality following fertilization of forested watersheds on
            the Olympic Peninsula,  spring 1970:  Quileene Ranger District,
            Olympic National Forest, Washington	   XI.47
XI.B.7. —Stream water quality after fertilization of a small forested watershed
            on the west slopes of the Cascade Mountains,  1970: Oregon	  XI.47
XI.B.8. —Stream water quality after fertilization following wildfire in north
            central  Washington, 1970: Chelan,  Washington	  XL48
XI.B.9. —Stream water  quality  following  forest fertilization,  spring 1976:
            Quileene Ranger District, Olympic National Forest, Washington .  XI. 48
XI.B.10.—Stream water quality and quantity of flow following fertilization of a
            forested watershed,   1971:  Fernow Experimental Forest, West
            Virginia	  XI.49
XI.B.ll.—Stream water quality following fertilization  of a gaged experimental
            watershed, spring 1970: South Umpqua Experimental  Forest,
            Oregon  	  XI.49
XI.B.12.—The impact  of forest fertilization on stream water quality in the
            Douglas-fir region—a summary of monitoring studies in Alaska,
            Idaho, Oregon, and Washington	  XI.50
                                       XI.v

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                                      INTRODUCTION
  Chemicals have played an important role in the
success  story  of modern American agriculture.
These same management tools — fertilizers, insec-
ticides,   herbicides,  fungicides,   rodenticides,
avicides, piscicides, etc. — are equally important
in meeting the rapidly growing demand for forest
products. Their magnitude, intensity, and pattern
of use is  vastly different in forestry,  and these
chemicals provide an economically feasible means
of controlling  insects  and disease and increasing
timber production. However, their widespread use
cannot proceed without adequate consideration of
the potential impacts upon environmental quality.
The  forest land  manager has a  responsibility to
protect the environment  from contamination and
thus  must be  aware of the potential hazards in-
volved with  each silvicultural practice that uses
chemicals.
  Chemicals introduced into a watershed as part of
a silvicultural activity represent a potential non-
point  source  of pollution for forest  streams.
Research findings and a long history of use have es-
tablished  that  most forest  chemicals offer
minimum potential for degradation of the aquatic
environment when they are  used properly (Norris
and Moore 1976). This chapter discusses the types
of fertilizers and pesticides  used, the magnitude
and  scope  of chemical  use,  the  behavior of
chemicals  in  the forest  environment,  and  the
mechanisms by which chemicals may reach forest
streams. This  information forms the basis for un-
derstanding  the non-point  source  pollution
processes  that result from  chemicals  used  in
silvicultural activities  and for selecting effective
controls. There is insufficient data to permit us to
quantify control  effectiveness.
                                              XI. 1

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                                         DISCUSSION
MAGNITUDE  AND SCOPE OF CHEMICAL
                      USE
  Newton and Norgren (1977) have categorized the
chemicals used in forest management into three
general groups based upon the broad objectives of
their use. One group is herbicides which are used
when  forest  productivity  is  to  be  focused on
selected species. Herbicides do not influence the
basic productivity of the forest ecosystem, but are
used to channel that productivity into selected
timber species that have special value. The second
group  of chemicals,  including  insecticides and
rodenticides, is  used to reduce losses of important
tree species. The specific targets of these chemicals
are  insect  and  animal pests that are  capable of
damaging  or destroying commercially desirable
tree species. Fungicides used to control diseases in
existing stands are also included in this group. The
behavior of these two major groups is discussed
together as "pesticides" in this  publication. The
third group of chemicals includes only fertilizers.
Chemicals  in this category are  used to increase
growth rates of commercial tree species by raising
the  overall  productivity  of forest ecosystems. Fer-
tilizer chemicals also are  used as fire retardants
and will be included in this group rather than dis-
cussed  separately.  A  wide variety  of  other
chemicals are used in forestry for insect and disease
control in nurseries, for soil stabilization,  for dust
control, for road surfacing,  and various other pur-
poses. However, these  latter chemical  uses are
limited in  scope and will not be discussed in this
publication.
  The potential  impact of introduced  chemicals
upon forest water quality depends largely on the
chemical  and  its  pattern of  use.  In intensive
agriculture, chemicals may be applied one or more
times during a crop cycle. Crop cycles are short;
thus, regular and repeated applications are a com-
mon practice. By contrast, most forest land will not
be treated with chemicals at any time during a crop
cycle. Lands that are treated seldom receive more
than  one treatment in a crop  cycle. (Crop cycles
range from 20 to more than 100 years.)  A large
number of chemical compounds are registered for
use in agriculture, while in  forestry less than 15
principal pesticides are used. Forestry practices ac-
count for only slightly more than 1 percent of the
total  pesticide  use and less than  1 percent of the
total  fertilizer consumption in the United States.

                   Pesticides
  Pesticide use on forest lands between July 1,
1975, and September 30,  1976, is  summarized in
table XI. 1. The figures represent  both pesticides
used by the Forest Service and pesticides used on
projects involving Federal assistance provided by
the Forest Service  (USDA 1977). In general, these
figures  underestimate the total  use  in  forestry
because they do not include pesticide use by other
Federal land management agencies or by various
State  and private  groups.  In  addition,  data
presented for insecticide use have been modified by
deducting the figures for one large  project con-
ducted  to control defoliation caused by the Eastern
spruce budworm. This single insect control project
accounted for 85 percent of the  total figure  for
                     Table XI.1.—Pesticide use in forests, July 1, 1975, to September 30, 1976'
             Pesticide used
                                       Acres treated
 Percent
Pounds used2
                                                                               Percent
Herbicide
Insecticide
Fungicide
Rodenticide
Piscicide
Bird repellent
235,551
326,148
34,109
22,599
481
714
38
53
5
4
0
0
563,517
'192,175
143,431
6,053
833
289
62
21
16
1
0
0
               'Reporting period is 15 months, FY 1976 and Transition Quarter (USDA 1977).
               'Reported as pounds of active ingredients.
               3Data presented do not include 3,501,950 acres treated with 2,663,208  pounds of insecticide
             chemicals to control defoliation caused by the Eastern spruce budworm. These data were omitted in
             order to provide a closer approximation of the annual pesticide use pattern.
                                                XI.2

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treated land area and 75 percent of the total figure
for  applied pesticide chemicals  during the  15-
month period covered by the report. Large control
projects of this magnitude (3,501,950 ac) do not oc-
cur on an annual basis; therefore, the data were
modified as described in order to provide a closer
approximation of the annual pesticide use pattern.
  Most insecticides applied to forests in the United
States are applied to Forest Service and adjacent
lands through Federal  cooperative insect control
projects for which the Forest Service has respon-
sibility. Thus, the figures presented in table XI. 1
provide a fairly  close estimate of the total annual
use of insecticides. Herbicide use projects are car-
ried out independently by the various forest land
management groups,  and  the figures  presented
reflect a considerable underestimate of total her-
bicide use. It is  apparent, however, that herbicide
use is considerably greater than insecticide use in
terms of  the  amount  of chemical applied,,  and
probably exceeds insecticide use in terms of total
area treated annually (with the exception of large
insect control projects).
                                    To further illustrate the scope of pesticide use in
                                  forests, a list of individual pesticide compounds or
                                  combinations is presented in table XI.2. The land
                                  area treated with each pesticide provides an indica-
                                  tion of its importance in forest land management.
                                  Data presented were obtained from the Fiscal Year
                                  (FY)-1976  and Transition  Quarter Pesticide-Use
                                  Report (USDA 1977)  and essentially represent an-
                                  nual  usage.  The total  number of  pesticide
                                  chemicals or combinations  is quite large, but the
                                  major  applications employ  only a few. Seven her-
                                  bicide  chemicals account for 95 percent of the total
                                  herbicide use.

                                    These figures  indicate that approximately 0.2
                                  percent of the commercial forest land in the United
                                  States is treated with pesticides in any given year
                                  (0.8 percent in FY-1976 including the large Eastern
                                  spruce  budworm  spray program). Therefore, in-
                                  teraction between pesticides and water quality is
                                  not  an extensive problem.  In  those areas treated
                                  with pesticides, however, the interaction, although
                                  localized, can be intense.
 Table XI.2—Reported pesticides used for silviculture in the United States, July 1, 1975, to September 30, 1976.1
 Herbicides
Acres treated
Herbicides
Acres treated
Insecticides
Acres treated
2,4-D
2,4,5-T
2,4-D & Picloram
Picloram
2,4-D & 2,4,5-T
MSMA
2,4-D & 2,4-DP
Simazine
Simazine and Atrazine
Atrazine
Diphenamid
Mineral Spirits
Dalapon
2,4,5-TP (Silvex)
Dicamba
2,4-D & Dicamba
79,713
40,155
36,662
29,891
12,797
7,624
6,073
5,424
3,000
2,440
1,673
1,219
1,215
1,198
981
950
Cacodylic Acid
Methyl Bromide
Dacthal
Amitrol
Trichlorobenzoic Acid
Trifluralin
Ureabor
Ammonium Sulfamote
Pentachlorophenol
Bromacil
Prometryne
Glyphosate




688
605
473
412
354
227
200
194
190
166
156
146




Carbaryl
Lindane
Trichlorfon
Malathion
DDT
Acephate
Dibrom
Difluron
Mirex
Bacillus Thuringiensis
Crotoxyphos
Dimethoate
Azinphos Methyl
Methomyl
Dursban
Pyrethrins
274,036
65,076
258,705
50,488
36,875
25,900
3,000
21,800
1,674
2950
900
851
681
450
368
300
  'Compiled from U.S. Forest Service Pesticide Use Reports, the amounts include chemicials used by the Forest Service
and chemicals used on projects involving Federal assistance by the Forest Service (USDA 1977). Actual total amounts are
considerably greater.
  2Does not include amounts used to control Eastern spruce budworm.
  3DDT and Carbaryl were used for  plague control.
                                               XI.3

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                  Fertilizers


  Fertilizers are applied annually to only a small
portion of  commercial  forest  lands.  Levels of
management on  most forest lands have not yet
reached the intensity where fertility would severely
limit economic yields;  however, several major
forest industrial corporations and public agencies
have been  using forest fertilization as a standard
management practice for a little over 10 years. Fer-
tilization operations are restricted to  the Pacific
Northwest, where nitrogen  deficiencies  are com-
monly encountered, and to the Southeast, where
phosphorous deficiencies often limit  tree growth
and reduce survival of young stands.
  Fertilization  of  forest stands  in  the Pacific
Northwest  was initiated in 1965 when one in-
dustrial corporation aerially fertilized 1,500 acres of
Douglas-fir with urea. Between 1965 and 1975, ap-
proximately 750,000 acres of Douglas-fir were fer-
tilized in western Oregon and Washington (Moore
1975b, Norris  and Moore 1976). Annual fertiliza-
tion increased  rapidly  up to  1973 when 160,000
acres were treated in 1 year.  The practice  then
dropped drastically as the energy crisis caused a
shortage of fertilizer  and also  raised the price of
nitrogen use to nearly double the cost per acre. Fer-
tilization practice is  increasing again  now in the
Pacific  Northwest, but  has not yet reached the
earlier peak of annual fertilizer application.
  The  first  forest  fertilization  project in  the
Southeast  was conducted in   1963 on 630 acres
(Groman 1972). The scope of operations in the
Southeast  has  not  approached that of  the
Northwest,  but by 1971 approximately 110,000
acres had  received chemical  fertilizers. When  a
moderate, but steady, increase in the practice was
assumed, a gross estimate of total fertilized acreage
through 1975 was 350,000 acres.
  Investigations conducted in the hardwood stands
of the Northeast indicate that nitrogen  deficiencies
appear to be limiting growth,  and the  application
of potassium has effectively stimulated growth on
old fields that  are being reforested. However, ad-
ditional field research is needed before forest fer-
tilization will be used in that region (Beaton 1973,
Mader 1973d,  Weetman and Hill 1973).
  Fertilizers, like pesticides, are applied to a very
small proportion of the total  commercial forest
land each year, and applications to any given site
occur infrequently. Through 1975, the total acreage
fertilized was only 0.2 percent of the  commercial
forest land in the United States, and the forested
 area  fertilized in any one  year did not exceed
 250,000 acres. However, a much larger total acreage
 of commercial timber stands is considered poten-
 tially  amenable  to  fertilization. The use of this
 practice to  increase  the  volume  of wood  fiber
 produced per unit area, and over a shorter period of
 time, can be expected to increase.


          Patterns Of Chemical Use
Insecticides

  At  present,  there  are  very  few  insecticides
registered for use on forest lands. Insect damage
problems in recent years  have been  handled as
special  projects,  where approval for a particular
chemical  or formulation  is usually  granted  by
regulatory agencies on a case-by-case basis. An en-
vironmental impact statement must be prepared
for  each project and is used as the basis for ap-
proval or denial of the proposed chemical control
program.
  The chlorinated hydrocarbon insecticides are not
usually selected for use in  forestry when alternate
chemicals are available. The application of DDT in
Idaho, Oregon,  and Washington for  control  of the
Douglas-fir tussock moth in 1974 was an exception.
Insecticides more likely to be used in  forestry are
various organophosphate  and  carbamate  com-
pounds. Nonresidual biological control agents are
also being used. Recent research has developed
suspensions of insect disease cultures that are quite
specific for the target insects. Virus  cultures have
been used in several projects with considerable suc-
cess and low impact on nontarget terrestrial and
aquatic insects. This material is now registered for
use in the control of Douglas-fir tussock moth.
  Applications  of insecticides to forest  areas are
almost exclusively made by aerial spraying. Large
or contiguous areas may be treated in a single pro-
ject to control an outbreak of defoliating insects on
commercially valuable  timber.  Regional projects
may include a large part of an entire river drainage
basin. Thus, in any one year, a large percentage of
the total amount of a given insecticide applied to
forests in the United States may be applied in only
one region.  Several  to many years  will normally
elapse before an  application of  any  magnitude is
made again in the same region. While the potential
for impact of insecticides on water quality and the
aquatic community may be relatively widespread
on a regional basis, it is still infrequent in  occur-
rence.
                                               XI.4

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Herbicides
  Herbicidal chemicals are used for a wide variety
of purposes in silvicultural activities including fuel
break  management;  vegetation  control  on
powerline,  road,  and railroad rights-of-way; con-
version of hardwood brush to conifers; release of es-
tablished conifers from hardwood brush competi-
tion;  thinning; cull tree removal in established
stands; and  control of noxious  weeds.  The most
commonly  used chemicals are  the phenoxy her-
bicides (2,4-D,2,4,5-T, and Silvex), picloram, and
triazines (atrazine and simazine), and the organic
arsenicals (MSMA and Cacodylic acid).
  Herbicides are  applied by a variety of means —
aerial (rotary or fixed-wing aircraft), low pressure-
high  volume  ground  spray  equipment,  mist
blowers, stem injection devices — and in a variety
of forms — pellets,  granules, and undiluted con-
centrates. Treatment areas are typically small (5 to
200 ac)  and widely scattered.  Large contiguous
blocks are  seldom treated. The annual extent of
herbicide use remains  reasonably constant on a
regional basis; therefore, the opportunity for in-
teraction between herbicides  and streams occurs
regularly,  but is of limited scope  in  any one
drainage system. Use  of herbicides on  any given
site is usually limited to one or, at most, two ap-
plications.
Fertilizers

  Forest fertilization is carried out in the Pacific
Northwest by  aerial application. Present opera-
tions  are  conducted almost exclusively with
helicopters (Moore 1975b). In the Southeast and on
Southern pine lands, ground equipment is used to
fertilize young stands and aerial equipment makes
application on older stands. Soils in Florida,  the
Flatwoods, and Atlantic Coastal Plain subregions
are deficient in phosphorus and fertilizer is applied
to them at time of planting or  soon thereafter.
Older stands respond to nitrogen or to nitrogen plus
phosphate,  if  the   stand  is  on  a  phosphorous
deficient site (Bengston 1970).
  Fertilizers may be applied to relatively large con-
tiguous areas, but a more typical practice is to fer-
tilize smaller management  units in  a patchwork
fashion. Treated areas are usually some distance
from users of potable or irrigation waters. The in-
frequency of application  coupled with application
to undisturbed forest soils and vegetation tends to
minimize the potential for impact on water quality.
Buffer strips   can  be  maintained  along major
streams,  but it is not possible to  avoid all of the
smaller headwater  streams. Thus,  some forest
streams in a fertilized watershed will normally con-
tain detectable amounts of chemical  immediately
after application.
Fungicides

  Fungicidal chemicals receive intensive use  in
forest nurseries, but  are seldom used  in
silvicultural activities. Nursery use is  more com-
parable to agricultural use than to forestry use and
is not included in this discussion. Fungicide treat-
ments to stumps and  roots for control of root and
butt rots affect only small and isolated areas and
provide little, if any, opportunity for  impact on
water quality.
Rodenticides

  Rodenticide use has decreased sharply in recent
years. The small quantities used in forestry and the
methods of applying them to the ground indicate
that any effects on water quality are not likely to be
detectable.
          CONCEPTS OF HAZARD
         AND CHEMICAL ACTION
  Pesticides used in  forest management are
selected because of their known effects on specific
targets. The hazard involved in their use is the risk
of adverse effects on nontarget organisms. Two fac-
tors determine the degree of hazard: (1) the toxicity
of the chemical and (2) the likelihood that non-
target organisms  will be exposed to a  toxic dose.
Toxicity  alone  does not make a chemical  hazar-
dous. The hazard comes  from exposure to toxic
doses  of  that  chemical.  Even the  most toxic
chemicals pose no hazard  if organisms  are not ex-
posed to them. Therefore,  an adequate  assessment
of the hazard involved in  the use of any chemical
requires that both the likelihood of exposure and
the toxicity of the chemical  be considered (Norris
1971).

  Chemical action is the direct effect of a chemical
on an organism. Chemical action on any organism
                                              XI.5

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 requires exposure and, furthermore, requires suf-
 ficient quantity of chemical present at the site of
 action, in an active form and for a sufficient period
 of time, to produce  a toxic effect. There are two
 kinds of toxicity: acute and chronic. Acute toxicity
 is the fairly rapid response of organisms to one, or a
 few, relatively large doses of chemical administered
 over a short period of time. Chronic toxicity is the
 slow or delayed response of organisms that occurs
 after repeated or continuous exposure to small
 doses of chemical extending over a relatively long
 period  of time.  There  are various  gradations
 between these two extremes. The kind of response
 (acute or chronic) observed in nontarget organisms
 depends on the magnitude of the dose, the duration
 of exposure, and the behavior of the chemical.

  Toxicity. — A consideration of the principles of
 toxicity or a review of the toxicity characteristics of
 silvicultural chemicals is beyond the scope of this
 chapter. Newton and Norgren (1977) provide an ex-
 cellent summary of this topic. Reference sources for
 the more  frequently used silvicultural chemicals
 are given  in appendix XI.C.

  Potential for exposure. — The potential for ex-
posure of nontarget organisms is determined by the
initial distribution of the chemical and its subse-
quent movement,  persistence, and disposition in
the environment. When a chemical is applied to a
forested watershed, there is an interaction between
the properties of the chemical and the properties of
the environment. These interactions follow  the
basic  laws of physics, chemistry, and biology and
define chemical behavior (fig. XI.l). The resulting
quantities of a chemical found in different parts of
the environment at varying times after application
determine the duration and magnitude of exposure
of different organisms to the  chemical. The overall
impact of chemicals on both target and nontarget
organisms and the selective action of chemicals de-
pend  on this exposure.
  CHEMICAL BEHAVIOR OF PESTICIDES
  The behavior of a chemical consists of its move-
ment, persistence, and disposition in the environ-
ment. Such behavior determines how much
chemical is  in what part of the environment for
what period of time and in what form. The initial
distribution of a silvicultural chemical and its sub-
sequent behavior in the terrestrial environment
determines its potential role as a non-point source
pollutant. Its behavior in the aquatic environment
and its inherent toxicity determine its importance.
                                            LAWS  OF
                                                          BEHAVIOR
                          POTENTIAL
                              OF
                          EXPOSURE
         Of OMHOttHŁKT
                  Figure XI.L—The Interaction of chemteata with th« environment (Morris 1971).
                                             XI.6

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                                         CHEMICAL APPLIED
                                                                                     Direct
                                                                                   Application
                                                                             Fallout
                                                                            Washout
                                                                    •-  s&t-Leochma,,*4^^^ AW-saW
                   WATER-—Decay, exudation-pLANTS—Decay, exudation—» SOIL

                          I	  Absorption 	'   '	 Absorption 	'

                        	  Surface runoff, sheet erosion, leaching   	
           Figure XI.2.—The distribution and disposition of chemicals in the environment (Foy and Bingham 1969).
    Initial Distribution Of Spray Materials


  Aerially applied chemicals are distributed in-
itially among four major components of the forest
environment: air,  vegetation,  the forest floor, and
surface waters (fig. XI.2). The amount of chemical
entering each portion of the environment is deter-
mined by the chemical and equipment used and
the environmental conditions that prevail at the
time of spraying (Norris and Moore 1971).
  Some spray material is dispersed by the wind as
fine droplets called "drift." The degree of lateral
movement of spray drift depends on droplet size,
height of release,  and wind  velocity  (fig.  XI.3)
(Reimer and others 1966). Additional amounts of
chemical may remain in the air due to volatiliza-
tion of spray materials while falling through  the
air. Most of the pesticide chemical not lost through
drift or volatilization is intercepted by vegetation
or the forest floor.  Some small amount of pesticide
may fall directly on surface waters.
              5 M.P.H WIND  	*•

Figure XI.3.—Lateral movement of spray particles of various
  diameters falling at terminal velocity  in an 8 km/hr cross-
  wind (5 mph = 8 km/hr; 1 ft = 0.3048 m) (Reimer and others
  1966).
                                                XI.7

-------
   Movement, Persistence, And Disposition
                 Of Pesticides
  The movement of pesticides includes movement
within a given compartment of the environment
(leaching in the soil profile) or movement from one
compartment  to  another  (washing  pesticide
residues from leaf surfaces to the forest floor by
precipitation).  Persistence  is  the  tendency  of
pesticides to remain in an unaltered form. The dis-
position of pesticides concerns the various physical,
chemical,  and biological pathways taken  by
chemicals  in  becoming  biologically  harmless
products. These aspects of chemical behavior will
be discussed for each environmental compartment.
Distribution In Air

  Losses of herbicides and insecticides to the air
may be appreciable, but there is little quantitative
data. During one test in western Oregon, for exam-
ple, from 20 percent to 75 percent of a herbicide ap-
plication  did not  reach  the ground,  but these
results were confounded by the presence of nearby
overstory vegetation1. Use of helicopters in place of
fixed-wing aircraft  and  the  introduction  of
improved drift control nozzles and spray additives
have  greatly  reduced  the amount of chemical
reaching sites outside the target zone.

  More recent work  has  used spray interception
disks. Norris and others (1976b) reported 85 per-
cent recovery of picloram and 70 percent recovery
of 2,4-D when using the spray interception disks in
a  southern Oregon  brush field  that  had been
sprayed by helicopter. On four powerline rights-of-
way  in Oregon  and  Washington treated  by
helicopter  with  2,4-D and  picloram, interception
disks recovered 71 percent of the 2,4-D and 90 per-
cent of the picloram.
  Several  things can happen to  that  portion  of
chemical that becomes dispersed  in the air. Fine
droplets (drift) or vapors (volatiles)  can be moved
to other locations where they settle to the earth.
Droplets and vapors can also be washed out with
rain,  absorbed or taken up by plants and other
organisms, or  adsorbed   on  various  surfaces.
Another possible  fate for many  pesticides  is
  ^Newton, M., LA. Norris, and J. Zauitkouski. Unpublished
data on file Sch. For.. Oregon State Univ., Corvallis.
photodegradation (Moilanen  and  others  1975).
With the exception of direct application or the
deposition of spray drift, the air is not an important
source of chemicals that later enter the aquatic en-
vironment.
Distribution In Vegetation

  The amount of pesticide intercepted by vegeta-
tion depends on the rate of application, the nature
and density of the vegetation, and  the  physical
characteristics of the spray material. Chemicals in-
tercepted by vegetation may be volatilized into the
atmosphere, washed off by rain, or adsorbed on the
leaf surface. There is limited absorption and very
little  translocation of many pesticides intercepted
by foliage. Through the action of rain, much of the
unabsorbed pesticide will be washed from the sur-
face of the leaf. Pesticide remaining on the leaf sur-
face and any pesticide not translocated  to other
plant parts will enter the environment of the forest
floor during leaf fall.
  Pesticides retained by the plant may be excreted
back  into the  environment through  the  roots or
they may end up in some plant storage tissue to be
released  at  a later time. Through metabolic ac-
tivity, plants may degrade  a pesticide  to  non-
biologically  active substances.
  Studies of herbicides show that the highest con-
centrations of residue occur in foliage shortly after
application  (see1 table XI.3) (Morton and others
   Table XI.3.—Residues of herbicide1 In forage grass
Tim* after
treatment
(Weeks)


0
1
2
4
8
16
52

2,4-D1



100
60
50
30
6
1
—
Herbicide rae
2,4,5-T*



100
60
30
15
6
2
—
Mue
Picloram9



135
—
32
—
24
16
3
 'Rate of application equals 1.12 kg/ha.
 2Data from figure 4 In Morton and others 1967.
 'Data from table 5 in Qetzendaner and others 1969.
                                               XI.8

-------
1967, Getzendaner and others  1969). A combina-
tion of factors causes the residue concentrations to
decrease  rapidly with  time.  Growth,  dilution,
weather,  and metabolism of the herbicide by the
plant are particularly important.
  Weathering is very important in reducing residue
levels of carbaryl on foliage. Wells (1966) reported
that rain in excess of 1.8 inches (45 mm) falling 12
to 24 hours after spraying reduced initial residue
levels  of carbaryl on oak foliage from 190 ppm to
about 15 ppm 3 days later. Degradation of carbaryl
residues on plants is less important, but plants ab-
sorb only small amounts  (Union Carbide  1968).
Formulation also influences persistence of residues
on foliage (Fairchild 1970). Carbaryl applied in an
80 percent wettable powder formulation had a half-
life (the time required by an organism to eliminate,
by biological or chemical processes, half the quan-
tity of a substance taken in) of 3 to 4 days, while
carbaryl applied in a Sevin-4-oil formulation was
found to  have a half-life of 8 to 10 days on range
grasses. Typical  initial residue  levels on  forest
foliage ranged from  30 to 100 ppm immediately
after treatment. These residues decreased to 5 to 20
ppm after 2  or  3 weeks (Back 1971).
  Dylox (trichlorfon)  insecticide is relatively non-
persistent; only small amounts remain on treated
foliage beyond  1 week  after  application. Residue
levels of 0.33 to 3.3 ppm trichlorfon on leaves, 0.42
to 1.1 ppm on twigs, and 1.5 ppm on forest litter 26
days after application  were reported  by Wilcox
(1971). Residues  were  still detectable after  106
days, even though residues declined most rapidly
over the first 7 days following spraying (Devine and
Wilcox 1972). Weiss  and  others  (1973)  reported
that Dylox residues dropped  sharply within a few
days after spraying, and that after 60 days, 15 per-
cent of the initial level remained on leaves,  5 per-
cent on the forest floor,  and less than 1 percent in
the soil.

  Orthene, also an organophosphate insecticide, is
readily degraded by plants. It has an observed half-
life of from 5 to 10 days (Chevron 1973). This insec-
ticide adheres to or is absorbed by leaf surfaces and
washing of field-treated vegetation will remove no
more  than  5  percent  of the residue present.
Translocation from treated leaves to other parts of
the plant is only very  slight. Orthene is not persis-
tent on forest vegetation because of its short half-
life (Devine  1975). Following field applications at
V4-, %,  and IVfc-lb active ingredient/acre, residues
on leaves and in forest floor material declined to
nondetectable levels in  1 to 2 months.
Distribution On The Forest Floor And In Soil

   The forest floor is a major receptor of aerially ap-
plied spray materials. Pesticides on the forest floor
may be volatilized and reenter the air, adsorbed on
soil mineral or organic matter, leached through the
soil profile  by  water,  absorbed  by  plants,  or
degraded  by chemical  or biological  means.
Volatilization of chemicals  from  the soil surface
may be responsible for the redistribution of fairly
large amounts of some pesticides such as DDT and
perhaps some phenoxy ester herbicides.
   The length of time chemicals persist in the forest
floor and soil bears strongly on the probability they
will  contaminate the  aquatic  environment.
Pesticide  degradation  is  usually biological, but
chemical  degradation is important in the loss of
amitrole  and  the organophosphate  insecticides
(Hance 1967, Kaufman and others  1968, Norris
1970).
   The common brush control herbicides  (2,4-D,
amitrole, 2,4,5-T, and picloram) are all degraded in
the forest floor although their rates of degradation
vary considerably (fig. XI.4). In red  alder (Alnus
rubra) forest floor material, 80  percent  of the
amitrole and 94 percent of the 2,4-D were degraded
in 35  days, but 120 days were required to degrade
87 percent of the 2,4,5-T. Picloram degradation was
slow,  35 percent in 180 days (Norris 1970).
   Adsorption and  leaching  are processes which
work  in  opposition  to one another. Adsorbed
molecules are not available  for  leaching, but ad-
sorption is not permanent. The amount of pesticide
that is adsorbed is in equilibrium with the amount
of pesticide in the soil solution. As the concentra-
tion of pesticide in the soil solution decreases, more
pesticide will be released from adsorption sites (fig.
XI.5). Thus, adsorption provides  only temporary
storage, and the soil is, in effect, a reservoir of the
chemical that will eventually be released. Leaching
is a slow process, capable of moving pesticides only
short distances (Harris 1967, 1969). Herbicides are
generally more mobile in soil than insecticides, but
mobility is relative, and even the movement of her-
bicides is usually  measured in terms only of inches
or a few feet.
  Most of the chemicals  applied to the forest,
regardless  of method of application, eventually
reach the  forest  floor and soil  compartments.
Chemical  behavior  in this  part  of  a  forest
watershed  is  particularly important because  it
determines  whether these  introduced chemicals
will be immobilized,  degraded,  or transported  to
                                               XI.9

-------
                                                                   LEGEND
                                                                Q  2,4-D
                                                                •  Picloram

                                                                EJ  2,4,5-T
                                                                •  Amitrole
                      20
40
80     100
TIME .days
120     140     160    180
          Figure XI.4.—Recovery of 2,4-D, amitrole, 2,4,5-T, and picloram from red alder forest floor material
                                           (Norris 1970).
         CHEMICAL+ADSORBENT  ^1
                      ^T CHEMICAL : ADSORBENT
                      Figure XI.5.—Chemical adsorption in soil is an equilibrium reaction.
the aquatic environment. The forest floor and soil
make up  a very active biological system  that
provides a number of processes by which pesticides
can be destroyed,  thus preventing their accumula-
tion or  redistribution.  Each pesticide material,
however, has its own chemical and physical proper-
ties that give it some degree of stability against
degradation.  Kearney  and  others (1969)  have
grouped the pesticides into major chemical classes
and  summarized  their  persistence in soil  (fig.
XI.6). Only the organochlorine insecticides have
persistence times expressed in years. Persistence in
                     the soil  of  all the  other  classes or groups of
                     pesticides is measured in weeks or months. The
                     length of each bar in figure XI.6. indicates the time
                     required for  70 to 100 percent degradation of the
                     particular pesticide when it was applied at normal
                     rates. Data used to construct the graphs were ob-
                     tained from studies conducted in agricultural soils,
                     but the same pesticides used in  forestry should
                     have the  same relative stability  in forest  soils.
                     Some pesticides that are degraded by soil microbial
                     activity persist for a shorter period of time in forest
                     soils.
                                             XI. 10

-------
   Organochlorine insecticides

               •••
                Chlordane

                DDT

  BHC, Dieldrin

Heptachlor, Aldrin, Metabolites
                                              Phosphate insecticides
                                                               Diazinon
0123456
              Years
                                         Malathion, Parathion
                                            J	I	I	I
                                                 468
                                                    Weeks
    10   12
Urea, triazine, and picloram herbicides     Benzoic acid and amide herbicides
             Propazine, Picloram
            •••
             Simazine
 Atrazine, Monuron
        IH
        Diuron
 Linuron, Fenuron

[Prometryne
    i 	i	i   i
                                                             2,3,6-TBA
                                                            ••
                                                       Bensulide
                                                       •1
                                                Diphenamide
                                        CDAA, Dicamba
                                            I     I	1
I
                                                 4     6    8   10
                                                    Months
         12
0  ?   4  6   8   10 12 14  16 18
              Months
Phenoxy, toluidine, and nitrile herbicides  Carbamate and aliphatic acid herbicides
                   2,4,5-T
                   •
           Dichlobenil
           ••
          MCPA
          2345
             Months
                                              Dalapon, CIPC

                                                 CDEC
                                                 468
                                                    Weeks
    10   12
           Figure XI.6.—Persistence of individual pesticides in soils (Kearney and others 1969).
                                     XI.11

-------
  Carbamate and organophosphate pesticides are
relatively nonpersistent in the forest floor and soil.
When  Sevin-4-oil was applied  at  1 pound car-
baryl/acre  to  control the gypsy moth, pesticide
residues in the soil were still detectable 64 days
later, but were below the  level of detection (0.2
ppm) 128 days after spraying (Wilcox 1972).
  Dylox (trichlorfon)  breaks  down rapidly  in the
soil. In studies carried out in New York (Judd and
others  1972), trichlorfon was  not detected in any
forest soil or lake mud samples after 4 days. Wilcox
(1971), in another New York  study, reported that
after 14 days no residues  were detected in soil.
Malathion applied to soil persisted for 2 days in one
study  and 8  days in another  (Pimentel  1971).
Devine (1975) found that residues of Orthene in soil
dissipated in  3  days.  Studies conducted  by
Chevron Chemical Company (1973) on the per-
sistence of Orthene in nine soils types indicated a
half-life of 0.5 to 6 days when treated at 1  ppm.
Distribution In Surface Waters

  Degradation  of  environmental quality in the
forest is often first recognized by changes in stream
quality. Stream contamination is a most important
expression of environmental contamination in the
forest because water  is not only the habitat  for
many biological communities, but also  a critical
commodity to downstream users. Pesticides may
enter streams  by several pathways and forest
managers can  greatly influence the amount of
chemical which enters streams near treated areas.
           Entry Of Pesticides Into
          The Aquatic Environment

  Any amount of pesticide that has  not  been
degraded, adsorbed,  volatilized, or taken up by
plants is available to move into  the  aquatic en-
vironment.
Movement To Streams From The Air

  That portion of the introduced chemical which is
not lost as drift or intercepted by vegetation or the
forest floor will fall directly on surface waters. This
route of entry offers the greatest potential for short-
term, but high-level, contamination of streams by
pesticides in the forest environment.  Stream con-
tamination by herbicide residues from forest spray
operations in Oregon has been intensively studied
(Norris 1967, Norris and Moore 1971, Norris and
Moore 1976, Norris and others 1976a, Norris and
others 1976b,  Norris and  others 1977).  Herbicide
residues were found for short periods in all streams
that flow  through or by treated areas.
  Although stream monitoring has been carried out
in conjunction with numerous field applications of
herbicides over a period of more than 10 years,
measured residues of the phenoxy herbicides have
never  exceeded  0.1  mg/1  in  western  Oregon.
Concentrations of amitrole to 0.4 mg/1 were found
in one stream immediately below a spray unit  in
the Coast Range  of Oregon (Norris and  others
1966).  Examples illustrating several  important
points about minimizing residues in streams are
presented in appendix  XI.A.
  For a given rate of application, the concentration
of herbicides in streams depends  on the surface
area of the stream in relation to its volume. The
total amount of herbicide entering a stream varies
with the length of the stream which receives the
spray materials and with the location of the spray
unit boundaries with respect to the stream. The
highest concentrations of herbicide are found  in
streams originating in or flowing directly through
spray units. In contrast, lowest concentrations are
found in streams which are totally excluded from
the spray  area.
  Surface water contamination caused  by direct
application of DDT was measured during and after
forest spraying in eastern  Oregon. The maximum
DDT concentration (0.28 ng/\) was a sample taken
a few hours after spraying. Most samples contained
less than 0.01 »g/l DDT (Tarrant and others 1972).
Endrin has also been found in forest streams fol-
lowing direct  aerial seeding with  endrin-coated
Douglas-fir seed. The maximum concentration  of
0.070 Mg/1 occurred immediately after seeding and
decreased rapidly to below detection level (0.001
Mg/1) within 5 hours (Moore and others 1974). At a
second site in  the same study, the maximum con-
centration of  endrin  found in a  slower moving
stream was 0.013 ng/l. However, residue concentra-
tions decreased slowly and did not reach the detec-
tion limit of 0.001 jtg/1 until 10 days after seeding.
  During  insecticide application, some spray does
reach  small  inconspicuous  streams and  small
bodies of  water such as shallow ponds or puddles
even though direct application to larger bodies  of
water  is avoided.  Triclorfbn has  been  found  in
small  amounts in  water  samples collected im-
mediately after  spraying, but the concentration
dropped below detectable limits 4 days after spray-
                                              XI.12

-------
ing (Judd and others 1972). In an outdoor pond
trichlorfon had a half-life of 0.3 days (Chemagro
1971).
  The  movement  of spray drift from  treatment
areas to surface waters is also an important source
of pesticides in the aquatic environment, especially
when large  contiguous  areas  are sprayed. The
amount of spray drift which occurs is influenced by
the carrier, the size of the droplets, and the height
of release. Wind speed, temperature inversions,
relative  humidity,  and  temperature are  en-
vironmental factors which influence the droplet's
size, rate of evaporation, speed of vertical descent,
and, therefore, the  extent of its  lateral movement
(Hass and Bouse 1968).
Movement To Streams From Vegetation

  Only small  amounts of pesticides will enter the
aquatic environment from the washing action of
rain on  the  vegetation  that overhangs  stream
courses and  from leaves falling into the water.
Residues on buffer strip vegetation will normally be
restricted to small amounts  of  chemical moved
laterally  as spray  drift  during  application and
volatile material brought down by precipitation.
Some pesticide chemicals are  excreted from plant
roots, but the quantities  are very small and only
the roots in  the stream  or hydrosoil would add
chemicals to the water. How much chemical enters
the stream in this way has not been studied.
Movement To Streams From The Forest Floor
And Soil

  Two competing reactions, leaching or infiltration
and  surface  runoff,  are the  ways by which
chemicals are moved from spray areas to streams.
Factors  favoring  infiltration  will  decrease  the
amount of surface runoff and with it the overland
flow  of  introduced  chemicals. The  amount of
chemical actually entering a stream due to surface
runoff will depend  on:

  1. Distance from treated area  to the nearest
     stream,
  2. Infiltration properties  of the soil  or surface
     organic layer,
  3. Rate of surface flow, and
  4. Adsorptive   characteristics  of surface
     materials.


  Conditions that retard the rate of surface runoff
will minimize the immediate level of stream con-
tamination. The long-term stream load of pesticide
will be reduced as  well, since  a longer residence
time in the soil provides greater opportunity for ad-
sorption and degradation.
  Runoff from agricultural lands and discharge
from  manufacturing  plants  are  the   principal
sources of water pollution by pesticides (Nicholson
1967).  Barnett and others  (1967)  maximized  the
probability of runoff by applying artificial rain (2.5
inAr) to recently tilled agricultural land and found
38 percent of the 2,4-D isooctyl ester in washoff
(sediment plus water),  but only 5 percent of the
2,4-D amine salt.  In  another  study, only small
amounts of 2,4,5-T and picloram moved from com-
pacted sod or recently plowed fallow clay loam soil
following artificial  rainfall  of 0.5  inch  in  1 hour
(Trichell and others  1968). Movement of  con-
taminated water over untreated soils significantly
reduced the concentration of herbicide in the runoff
(table XI.4).
                 Table XI.4.—Effect of slope, rate of application, and movement over untreated sod
                              on the concentration of picloram In runoff water12

Rat*
(Ib/ac)

2
1
2
1

Slope
(percent)
Percent
8
8
3
3

Portion of plot
treated

Upper half
Entire
Upper half
Entire

Picloram In runoff
water3
ppm
2.1
3.8
1.3
2.0
Applied
picloram
runoff
Percent
1.6
5.5
0.9
2.8
              'Data from Trichell, and others 1968.
              'Picloram applied as potassium salt In water .88 Ibs/ac (400 g/ac).
              •Simulated rainfall was 0.5 ip/hr, 24  hours after herbicide application.
                                              XI.13

-------
                                 BEACON ROCK STUDY AREA

w
a;
"§1.0-
0

30-
.020-
a.
10-
0
RAINFALL PATTERN



r
r-.
L

in

I Ifll I
ni k
'4 ' i'UI 'U U 1 ' 1 i
I




P a?
:• i
'•:


10 20 30
SEPT.
50 CONCENTRATION OF HERBICIDE IN RUNOFF WATER
)7 HO A_r>
51 U*.*"
|n 38 ^
.-jtl | Sampling Date
'* ^ r
= •;

10


1 PR
20 30 10 20 30 10 20 30
OCT. NOV. DEC.
         Figure XI.7.—Precipitation and herbicide runoff patterns at the Beacon Rock Study area. A total of 6 and 1.5
           Ibs/ac of 2,4-D and picloram, respectively, was applied in two treatments (July and August 1967). Her-
           bicide residues were measured in ponded drainage water from the treated area (Morris 1969).
  In areas where runoff is likely to occur, pesticide
washoff will be greatest during the first storms after
the pesticide is applied. The greatest potential for
pesticide  movement  exists  when  significant
amounts of precipitation occur shortly after ap-
plication.   On  a  powerline  right-of-way in
southwestern Washington, the highest  concentra-
tions of the herbicides 2,4-D and picloram in runoff
water  were associated  with the  first  significant
storm  following the herbicides'  application  (fig.
XI.7).  The concentrations of herbicides declined
with  time  despite  subsequent  storms of even
greater intensity (Norris 1969). Mobilization of
chemicals in transitory stream channels by the ex-
panding stream  system described by Hewlett and
Hibbert  (1967)  is believed to account for the im-
mediate  flush of chemical observed with the  first
significant   storms.  Norris  and  others  (1976a,
1976b) found the total  discharge of picloram and
trichlopyr from two watersheds was approximately
equal to the amount of chemical applied to an
ephemeral stream channel.
  There  is ample evidence to show that phenoxy
and amitrole herbicides are not lost in runoff dur-
ing intense fall precipitation from lands treated
with herbicides in the spring  in  western Oregon
(Norris 1968).  Favorable conditions  and  ample
time for degradation of the herbicides under these
circumstances reduce the chance that they will be
mobilized in ephemeral stream channels.

  In order to determine to what extent trichlorfon
might move with surface runoff, Chemagro (1971)
sprayed this insecticide on sloping plots of three
soil types at 20  pounds active  ingredient/acre.
Simulated rainfall was then applied once weekly
                                               XI.14

-------
for 5 weeks. After the 5-week period, total residue
in runoff water from a silt loam soil was 2.86 per-
cent of the total applied. Losses from a sandy loam
were 0.65 percent,  and from  a high  organic  silt
loam, 0.35 percent.

  Pesticides leach into the soil profile and subse-
quently are  transported to streams by subsurface
drainage;  this is  another possible route to stream
contamination. Leaching, however, is a relatively
slow process in highly organic forest soils; only sm-
all amounts of chemical move through short dis-
tances.  Harris (1967,  1969)  has determined  the
relative mobility of  pesticides in soil  columns
leached with water (fig.XI.8). Herbicides in general
are more  mobile  in soil than  pesticides, but this
mobility is only relative. Even the herbicides move
only short distances in the soil under normal condi-
tions (Scifres  and others 1969,  Wiese and Davis
1964).

  Orthene is not tightly bound by soil particles and
is, therefore, susceptible to leaching.  However, it
does not persist long  enough to allow any signifi-
cant movement,  either by  leaching  or surface
runoff  (Chevron 1973). This compound  also
degrades  rapidly in   water.  In the  laboratory,
Orthene showed a half-life in water of 46 days, but,
in  the field,   degradation  is  accelerated  by
breakdown  in  aquatic  vegetation  and  soil
microorganisms in  bottom  mud;  measurable
residues were gone in 1 to 9 days (Chevron 1973,
1975; Devine 1975).
  Boschetti (1966) reported carbaryl residues of 1
to 3 parts per billion (ppb) in streams in or near
areas  treated  for  gypsy  moth  control  in the
Northeast. In a later study (Devine 1971), carbaryl
residue in  ponds and streams ranged from non-
detectable to 50 ppb during an 8-day period follow-
ing spraying. Residues in pond mud ranged from
nondetectable to 620 ppb.
  DDT is very low in water solubility (1.2 ng/\) and
is extremely  resistant to  movement  in  soil
(Bowman and others 1960, Guenzi and Beard 1967,
Reikerk and Gessel 1968). Any appreciable move-
ment of DDT  through  soils  by leaching must,
therefore,  be the result  of  movement of colloidal
particles of the free  or  adsorbed pesticide. The
likelihood of large amounts of the chemical enter-
ing the aquatic system seems remote when move-
ment of chemicals by leaching can be measured in
inches and the  distance between  spray units and
streams may be hundreds of feet.
 Figure  XI.8.—Relative mobility of
  pesticides leached in columns of soil
  (Harris 1967, 1969).
   Phenoxy and Picloram
        Herbicides
                                        Misc. Herbicides
                                                                  Phenylurea, Triazine, and
                                                                      Other Herbicides
                                           Cipc and Toluidine Herbicides

                                                          |  Thionazin
                                         Diazinon
                                    Disulfoton and Phorato

                              I   Chlorinated Hydrocarbon Insecticides
                          least mobile
                                           o.is
RELATIVE MOBILITY
0.15           1.0
        most mobile
                                              XI.15

-------
Summary Of Pesticide Entry Into The Aquatic
Environment

  To summarize, most chemicals enter the aquatic
environment through either direct application or
drift of spray materials to the water surface. The
forest manager has considerable control over these.
Research has demonstrated that direct application
of spray  materials to  water surfaces can  be
minimized by excluding  streams from treatment
areas.  Careful  selection  of  spray equipment,
chemical formulations, and conditions of applica-
tion will minimize the potential for drift.
  Mobilization  of residues in ephemeral stream
channels during the first  significant storms follow-
ing chemical application is the second most impor-
tant source of chemical residues in forest streams.
  Pesticide residues moving overland with surface
runoff during intense precipitation  is  the  third
most important way by which chemicals may enter
the aquatic system.  The  phenoxy herbicides,
amitrole, and the carbamate and pyrethrum insec-
ticides degrade  rapidly so  they  are  available  for
overland  transport  to   streams  for only  short
periods. Picloram may persist for more than one
season, but  its  tendency to leach into the soil
profile reduces  its chances of moving by surface
runoff into streams. DDT and similar compounds
are resistant  to degradation  and  leaching,
therefore,  they  are exposed to overland transport
for extended  periods  of  time.  However, the
chlorinated  hydrocarbon  insecticides are no longer
selected for use in  forestry  when  alternate
chemicals are available. Overland flow of water on
forested watersheds is relatively uncommon, and
pollution of streams from  this source will be limited
to areas where rates of infiltration are considerably
less than normal rates of precipitation. The stream
contamination  that  does occur will  be reduced
when the contaminated water moves over the un-
treated buffer strips. Leaching is not a significant
process in  the  entry of  forest chemicals into
streams. Specific Controls are listed under "Aerial
Drift  and Application of  Chemicals,"  and "All
Resource Impacts" in Section B of Chapter H:
Control Opportunities.
    Behavior In The Aquatic Environment


  How an aquatic organism responds to a chemical
will depend on the duration and magnitude of the
exposure and the interaction of the organism with
other stresses in its environment. How a chemical
behaves in the aquatic environment will determine
both duration and magnitude of the exposure.
  Chemicals may be lost from the aquatic environ-
ment through volatilization;  adsorption in stream
sediments; absorption by aquatic biota; degrada-
tion by chemical,  biological,  or photochemical
means; or dilution with downstream movement
(fig. XI.2).
Volatilization

  The amount  of  pesticide lost from water by
volatilization varies with both the properties of the
chemical  and the environmental conditions. The
chlorinated hydrocarbon insecticides (like DDT)
are of very low solubility in water and tend to col-
lect at water surfaces in films where they may be
subject to co-distillation. Water suspensions con-
taining 5  ng/[ DDT have been reported to lose 30
percent of the insecticide  in 20 hours at 79°  F
(26° C) (Bowman and others 1964). Fuel oil carriers
may concentrate oil soluble pesticides at water sur-
faces (Cope 1966).
Adsorption

  In turbulent  streams chemicals will be quickly
dispersed throughout the water allowing maximum
interaction with various adsorbing surfaces (Cope
and Park 1957). Reductions in pesticide concentra-
tions in water by adsorption depend on the rate, ex-
tent, and strength of adsorption, and the mixing
characteristics of the stream (which will govern the
opportunity for interaction within the stream bot-
tom). Researchers have given these factors only
limited attention. Clay and fine silt are effective in
adsorbing and reducing the activity of DDT and
other chlorinated hydrocarbon insecticides in river
water  (Ferguson and others  1966,  Fredeen and
others  1953). Bottom sediments from bodies of
water treated with various phenoxy herbicides fre-
quently contain residues which may indicate ad-
sorption  (Bailey and others 1970, Smith and Ison
1967).  Aly  and Faust (1965) reported that the
amounts of 2,4-D adsorbed on suspended clays in
water were small. Considerable research is needed
to clarify the importance of adsorption in reducing
pesticide concentrations in water.
                                              XI.16

-------
Degradation

  There are conflicting reports on the persistence
of pesticides in streams. In one study, 2,4-D esters
were hydrolyzed to free acid in 9 days in lake water,
but 2,4-D acid persisted up to 120 days (Aly and
Faust  1964). In  another  study,  only 40  percent
degradation of 2,4-D in water was observed in 6
months, during  which excellent conditions  for
biological activity were present (Schwartz 1967). A
considerable decrease in degradation of 2,4-D was
observed in bacterially active natural river waters
that had  reduced levels of dissolved oxygen (fig
XI.9).
  Robson  (1968) reported that the persistence of
2,4-D in fresh water was decreased from 9 weeks to
1 week when small quantities of soil previously
treated with phenoxy herbicides were added. Rapid
degradation of 2,4-D occurred in water samples col-
lected from areas with a history of repeated 2,4-D
applications (Goerlitz and Lamar 1967). Many sur-
face  waters may  lack suitable  conditions for
biological  degradation of herbicides or they may
not contain populations of microbes adapted to use
of the phenoxy  herbicides  as substrates (Hemmet
and Faust 1969).
  Degradation of certain chemicals is pH depen-
dent.  Amitrole resists  degradation in activated
sludge  cultures, distilled water, or sewage held at
room  temperatures for various periods  of  time
(Ludzak and  Mandia  1967).  Carbaryl  rapidly
degrades in sea  water, but it will persist for longer
periods in the more  acid conditions found in forest
streams (Aly and El-Dib 1971, Karinen and others
1967). The rapid hydrolysis of malathion in water is
               also pH dependent (Guerrant and others 1970), 50
               percent decomposition occurred in 26 days at pH
               6.0 and in 2.5 hours at pH 10.0.
                 In studies  conducted as a part of gypsy moth
               suppression in the Northeast, carbaryl persistence
               in the aquatic environment was found to be brief.
               Romine and Russian (1971) suggest that an initial
               level of 1 mg/1 will be completely gone in 1 to 2
               days. In an earlier study, water residues of 30 jug/1
               dropped to 1-5 Mg/1  in 1 day (USDA  1964).
                 Carbaryl, the phenoxy herbicides, amitrole, and
               picloram are all susceptible to photodegradation
               (Crosby and  Li 1969, Karinen and others 1967).
               The importance of this reaction in the natural en-
               vironment is  questionable, however, because most
               streams are shaded and there is limited penetration
               of the water by ultraviolet radiation.
               Downstream Movement

                 Downstream  movement of chemicals and the
               resulting dilution due to natural stream mixing and
               the addition of  uncontaminated water from  side
               streams is one of the most important mechanisms
               by which the concentration of pesticides in streams
               is  reduced near treatment  areas. Although the
               hazard  of exposure  is not  eliminated until the
               residues are completely degraded to nontoxic com-
               pounds, dilution as the result of downstream move-
               ment can reduce the concentrations of pesticides in
               streams to levels that do not represent a hazard to
               nontarget organisms.  DDT residues were  carried
               downstream in well defined blocks and did not per-
               sist for long periods  at sampling stations located
     .0
      o.
     Q
     4
     CM"
Q  WARM - AEROBIC

°  COLD - DEOXYGENATED
•  COLD - AEROBIC
                            20
       40              60
          TIME,  (days)
80
100
         Figure XI.S.'—The degradation of 2,4-D In a bacterlally active water culture (DeMarco and others 1967).
                                              XI. 17

-------
along an 85-mile stretch of the Yellowstone River
following  spray operations  in Montana  (Cope
1961).  Marked  reductions  in concentrations  of
amitrole and the phenoxy herbicides were observed
in water due to downstream movement (Marston
and others 1968, Norris and others 1966).
 CHEMICAL BEHAVIOR OF FERTILIZERS
Initial  Distribution In  Air,  Vegetation,  And
                 Forest Floor
  Many  concepts concerning the initial distribu-
tion of pesticides apply also to fertilizers, but there
are some important exceptions. The rate at which
nitrogen  fertilizer is applied varies with site and
timber type but is usually 150 or 200 pounds of urea
nitrogen/acre. Phosphorus  is  applied  at rates
between  80  and  100 pounds  P206/acre  in  the
southeast.  In  contrast  with  pesticides,  where
significant quantities may  remain  in the  at-
mosphere,  essentially all of the fertilizer applied
reaches the intended target.  However, because of
the higher rates of application,  it is necessary to
make at  least two flights over the unit and a uni-
form rate of application  over an entire unit is dif-
ficult to  obtain (Strand  1970).
  The introduction of large, specially coated urea
granules  (forest grade)  has  eliminated the  drift
problems that  were  experienced when standard
agricultural urea was used. Drift problems still ex-
ist, however, when standard agricultural urea (45%
N)  is used, or when experimental liquid formula-
tions  of  nitrogen  are substituted  for the forest
granules.   Should  liquid fertilizer formulations
come into commercial use, their initial distribution
in the environment will be subject to the same fac-
tors controlling distribution of aerially  applied
pesticides.
  Because  very little granular  fertilizer  is in-
tercepted by a dry forest  canopy, the forest floor is
the major receptor.  The  initial distribution  of
aerially applied fertilizers is thus restricted to the
forest floor and to exposed surface waters within
the treated areas.
  Urea fertilizer is highly water soluble and readily
moved into the forest floor  and soil by any ap-
preciable amount of precipitation.  Under normal
conditions, urea is rapidly hydrolyzed (4-7 days) to
the ammonium ion by the enzyme urease. When
moisture is limited, however, urea granules may be
slowly hydrolyzed on the forest floor, resulting in a
marked increase in surface pH and a loss of am-
monia nitrogen  by volatilization.  In a laboratory
study, Watkins  and others (1972) measured losses
of ammonia nitrogen ranging from 6 percent to 46
percent of the urea nitrogen applied to forest floor
and soil depending on the nature of the surface,
surface pH, and rate of airflow across the surface.
Although some  applied  nitrogen  is undoubtedly
lost by volatilization in the field, it is generally con-
ceded that such losses are small. Time of applica-
tion is important, and forest fertilization projects
are usually conducted  during the spring or fall
months to take  advantage of precipitation.  Urea
nitrogen is quickly distributed throughout the liv-
ing complex,  becomes  a part of  the  nutrient
budget, and is cycled within the ecosystem.
   CO(NH2)2 [solid]  H2°»CO (NH2)2 [solution]

    CO  (NH2)2  + 2H20  urease > (NH4)2 C03

       (NH4)2C03 —H2°' C°2 » 2 NH4HC03


         Entry Of Fertilizers Into The
             Aquatic Environment


  Fertilizer chemicals may enter the aquatic en-
vironment by one of several routes. Direct applica-
tion of chemicals to exposed surface water is the
most important way. This can be minimized by
carefully marking and avoiding larger streams dur-
ing applications, but it is usually  impractical to
avoid small headwater  streams,  which  frequently
are intermittent and  difficult to see from the air.
Exposed  surface  water  may  absorb   ammonia
nitrogen that has volatized from the forest floor
into the air. It is doubtful, however, that  this source
adds significant amounts to the  streams.
  Overland flow,  or  surface  runoff, is a  major
source of nutrients in streams draining nonforested
areas, but it is not an important route for fertilizers
from  treated forest watersheds to enter streams
since  surface  runoff rarely  occurs. Subsurface
drainage is another possible way soluble forms of
nitrogen enter into streams. Forest soils are excel-
lent filters for most plant nutrients because of their
high exchange  capacities and dense root systems
which can absorb  and recycle nutrients (Moore
1970). However, measurable levels of ammonium-,
                                              XI. 18

-------
nitrate-,  urea-,  and organic-nitrogen have  been
found in several streams that were monitored for
water quality in western Oregon and Washington.
  There is an enormous amount of literature con-
cerning the  effects of farm fertilization on water
quality, but only a few papers concerning the ef-
fects of forest fertilization. Soileau's (1969) exten-
sive  bibliography (701 entries)  on effects of fer-
tilizers on water quality contains no references on
effects of forest fertilization.
  Several forest fertilization projects have  been
monitored recently and examples of the data ob-
tained are presented in appendix XI.B. Data from
one study conducted in the Pacific Northwest are
discussed  below to illustrate the  magnitude  and
pattern of nutrient loss to streams. Measures that
may be used to minimize the potential for stream
contamination are also indicated.
  Moore (1971) measured the amounts and forms
of nitrogen entering streams during and following
aerial application of 200 Ibs/ac of nitrogen (as urea)
to an experimental watershed  in  southwestern
Oregon in March 1970 (fig XL 10). Data obtained
during the first 15 weeks after application are sum-
marized  in  table XI.5. Urea  concentrations in-
creased  slowly and  reached a maximum of 1.39
mg/1  urea-N 48  hours after application  started.
Ammonium-N  increased  slightly  above  pre-
treatment level,  but never reached 0.10  mg/1.
Nitrate-N began  to increase slowly the second day,
reached 0.168 mg/1 in 72 hours, and was 0.140 mg/1
at the end of 2 weeks. Nitrite-N was not detected
and wouldn't be  expected to occur in well aerated
streams.

  All urea losses of applied nitrogen occurred dur-
ing the  first  3  weeks. Losses  in  the form  of
ammonium-N, even though small, continued for 6
weeks. During the first 9 weeks after application,
net loss of applied nitrogen amounted to only 1.81
kilograms from watershed 2 (table XI.6).
                                         COYOTE CREEK WATERSHEDS
                                 SOUTH UMPQUA  EXPERIMENTAL FOREST
                                              0-125 0-25  0-375
                                                    MILES
              0-5
       PROPOSED ROADS
                                                          TO S. UMPQUA RIVER
                                                              EXISTING ROAD
   20 SMALL 2-3 A
     CLEARCUTS
   TOTALING 52 A
                                                                                   NORTH
        Figure XI.10.—Coyote Creek watersheds, South Umpqua Experimental Forest, Umpqua National Forest,
                                        Oreg. (Moore 1971).
                                             XL 19

-------
                       Table XI.5.—Concentration of fertilizer nitrogen In selected water samples
                       collected at watershed 2, South Umpqua Experimental Forest, following
                                application of 200 pounds urea-N/ac (Moore 1971)
              Date
                               Time
                                           Urea-N
                                                        NHaN'
                          NOs-N
Total


3/25
3/26


3/27


3/28
4/1
4/8
4/15
4/22
5/6
5/27
6/17
7/8


0800
0815
1230
2025
0805
1640
2005
0805
—
—
—
—
—
—
—
—


.007
.437
.237
.171
1.389
.606
.488
.075
.007
.028
0
0
0
—
—
—
mi
	 IT'!
.001
.016
.012
.034
.048
.036
.029
.036
.016
.015
.010
.010
.013
0
0
0
n/l

.002
.040
.069
.067
.107
.150
.168
.117
.091
.140
.030
.021
.022
.004
.002
.006


.010
.493
.318
.272
1.544
.792
.685
.228
.185
.183
.040
.031
.035
.004
.002
.006
                'Includes both ionized (NH4+) and un-ionized (NHs) ammonia-nitrogen
                    Table XI.6.—Nitrogen lost from treated watershed 2 and untreated watershed 4,
                     South Umpqua Experimental Forest, during the first 9 weeks after application
                                   of 224 kilograms urea-N/ha (Moore 1971)
              Unit
Urea-N
                                                        NHa-N
                                                                    NOa-N
Total
Kilnnrnms N
Watershed 2
Watershed 4
Net loss
Percent of total loss
0.65
0.02
0.63
34.75
0.28
0.06
0.22
12.25
1.01
0.05
0.96
53.00
1.94
0.13
1.81
100.00
   Low streamflow caused by limited precipitation
throughout the summer and fall months resulted in
essentially no loss of applied nitrogen during the
next  24  weeks.  Storm  activity in  November
brought the soil moisture level back to maximum
storage capacity. In December the nitrate-N con-
centration in samples for the fertilized watershed
reached a second peak of 0.177 mg/1 (fig. XI.ll).
Both  streamflow  and nitrate-N  levels remained
high throughout December and January, resulting
in the loss of an additional 23.8 kg applied nitrogen.
This second peak accounted for 92 percent of the
total amount of fertilizer nitrogen which was lost
during the first year.

   Total net loss of applied nitrogen from the fer-
 tilized watershed (68 ha)  during the  first year
 amounted to 25.85 kg, or 0.38  kg of nitrogen/ha
 (table  XL 7).  Over the  same  period  the total
 amount of soluble inorganic nitrogen lost from the
           control watershed (49 ha) was 2.15 kg, or 0.04 kg
           nitrogen/ha. Data  for  soluble  organic  nitrogen,
           total phosphorus, silica, and exchangeable cation
           content of the stream samples, including sodium,
           potassium,  calcium, magnesium, iron, manganese,
           and aluminum,  indicate that there was no ap-
           parent effect of nitrogen fertilization  on loss of
           native soil nitrogen  or other plant nutrients: Move-
           ment  may  have occurred in the soil profile, but
           there was no measurable change in stream water
           quality.
              Initial  losses of  applied  nitrogen were largely
           caused by direct application of urea fertilizer to the
           drainage channel. These losses were measured first
           as an increase in urea-nitrogen and then as a small
           increase in ammonium-nitrogen, the  latter as a
           result of hydrolysis  of urea applied to open water.
           The nitrate-nitrogen entering the  stream shortly
           after application  was probably leached from the
           soil immediately adjacent to the stream channel.
                                                XI.20

-------
                 25   29   2   6   10
                 MARCH —  APRIL 1970
                   TIME AFTER APPLICATION
                                                                0. 2-1
1.5-,


1.0-
mg/l
0.5



0.0
— - UREA -N
,', 	 NO, - N
l\
\ \ 	 NH3 - N
1 i
I i

I s
/ \


                                                             mg/l
                                                                0. 1-
                                     14
                                                                0. 0 LJT
             MAR  MAY  JUL  SEP NOV JAN MAR

                       1970           1971
         Figure Xl.11.—Fertilization of a 68-ha watershed with 224 kg urea-nitrogen/ha in March 1970. A. Immediate
           effect on water quality; B. Effect on nitrate-nitrogen concentration in streamflow for 1 year following fer-
           tilization (Fredriksen and others 1975).
During the first 9 weeks after application, approx-
imately half of  the  applied  nitrogen  was  lost
through direct  application  and half entered the
stream as nitrate-nitrogen. However, all of the ap-
plied  nitrogen  lost during this 9-week period
amounted to only 7 percent of the total loss that oc-
curred over the first year.
  High streamflow coupled with the second peak in
nitrate-nitrogen  levels during  the winter  storm
period accounted for 92 percent of the total loss. In
February and March 1971,  streamflow remained
high, but most of the mobile nitrogen had already
been lost, and nitrate-nitrogen concentrations had
returned to near normal.
  Similar data have been obtained in each of the
monitoring studies that have been conducted in the
Douglas-fir region and elsewhere. The length of the
monitoring period has varied from a few weeks fol-
lowing treatment to 6 or 7 months, and in a few
studies monitoring  continued for at least a full
year. Sampling  usually continued until the forms
of nitrogen  being  measured  decreased  to  near
pre-treatment levels. Increases in the concentra-
tion  of urea-N are almost entirely caused by direct
application to surface waters, and the peak con-
centration reached is directly proportional to the
amount of open surface water in the treated unit.
Peak concentrations above 5.0 mg/l are in every
case associated with projects where no buffer strips
were left along the main streams; or where fertilizer
application was  carried out early  in  the spring,
when the drainage system was greatly expanded by
spring runoff of snowmelt.  Even when buffer strips
of 30 to 90 m are  left along main streams and
tributaries, some direct application to water sur-
faces still will occur  because of a relatively dense
network of small feeder tributaries that are only a
foot or two wide and  cannot be identified from the
air.

  Peak concentrations of urea-N do not persist  for
more than  a  few hours. Concentrations
characteristically reach a  peak each day that fer-
tilizer is being applied and then drop rapidly back
toward pre-treatment levels. Within 3 to 5 days
after application is completed, levels of urea-N in
the stream have returned to pre-treatment  con-
centrations.
                   Table XI.7.—Nitrogen lost from treated watershed 2 and untreated watershed 4,
                      South Umpqua Experimental Forest, during the first year after application
                                  of 224 kilograms urea-N/ha (Moore 1971)
             Unit
                                          Urea-N
  NHa-N
NOa-N
Total
... Kl

Watershed 2
Watershed 4
Net loss
Percent of total loss
0.65
0.02
0.63
2.44
0.28
0.06
0.22
0.86
27.09
2.07
25.02
96.70
28.03
2.15
25.88
100.00
                                                XI.21

-------
  Ammonium-N levels also increase as a result of
direct application of urea-N to open water. Urea is
readily hydrolyzed to ammonium-N in the aquatic
system. Urea applied to the forest floor and soil will
not reach the stream since it hydrolyzes rapidly to
ammonium  carbonate  and is held on  cation  ex-
change  sites in the soil and  forest floor  like any
other salt. Concentrations of ammonium-N in  the
stream  are  rapidly  reduced  through  uptake  by
aquatic organisms and by adsorption  on stream
sediments. Levels in the streams sampled exceeded
1.00 mg/1 only when direct application of urea to
the stream was noted. Peak concentrations are nor-
mally 0.10 mg/1 or less  and do not persist for more
than a  few  hours, but  levels  of ammonium-N  re-
main slightly above pre-treatment level for up to 3
and 4 weeks.
projects, where direct application to the open sur-
face waters has been avoided or minimized by buf-
fer strips along the main streams and tributaries,
measured amounts of applied nitrogen entering the
stream are less than 0.5 percent.

  Increased phosphorous concentrations following
application of phosphate fertilizers have not been
reported. Phosphorus added to forest soils is readily
utilized by forest organisms or is rapidly converted
to nonsoluble forms. Powers and others (1975) have
stated that most forest soils have the capacity to tie
up, in nonmobile form, many times the quantity of
phosphate that foresters are likely to apply. There
have  been no reports of  significant increases in
phosphorous  concentration in  streams following
fertilizer application.
  The peak concentration of nitrate-N in stream
samples usually occurs from 2 to 4 days after fer-
tilization. Magnitude of the peak concentration de-
pends on  whether buffer strips are left along the
main stream channels, the width of the waterside
area, and  the density of small feeder and tributary
streams in the drainage system of the fertilized
area.  Peak  concentrations  of  nitrate-N are
generally  below 1.0  mg/1, but higher levels have
been measured in a few studies.  Concentrations
usually decrease rapidly after the peak is reached,
but  remain above pre-treatment level for  6 to 8
weeks. In monitoring studies where sampling has
continued through the first winter following fer-
tilization, additional peaks in the concentration of
nitrate-N have  been measured.  These  peaks
usually coincide  with the  more  intense  winter
storms, and the concentration  drops sharply
between  storms.   Maximum   concentrations
measured are still low and tend to decrease with
each successive storm.


  Losses of applied nitrogen are usually very small
because the maximum concentrations are generally
low, and  streamflow decreases  rapidly with the
onset of the growing season. Following spring ap-
plication,  about half of the applied nitrogen enter-
ing the stream during the first 30 days is from
direct application and is measured as urea-N and
ammonium-N;  the other half enters as nitrate-N.
All subsequent losses of applied nitrogen  to the
stream  enter as nitrate-N.  During early fertiliza-
tion projects, where buffer strips were either inade-
quate or not used, estimated total loss was between
2 and 3 percent of the applied nitrogen. In later
Summary Of Fertilizer Entry Into The Aquatic
Environment

  The most  important  mechanism of  fertilizer
entry into the aquatic environment  is direct ap-
plication to open surface waters. Numerous studies
(appendix B) have shown that the amount of ap-
plied nutrients entering  streams has resulted in
minimal increases in the instream concentrations
of nitrogen and phosphorus. When direct applica-
tion of fertilizer to  streams can  be reduced or
prevented by use of adequate buffer  strips and
marking of water courses, the potential impact on
stream quality can be minimized.

  Transport of mobile forms of nitrogen (nitrate-
N)  to streams  by subsurface  drainage from the
riparian zone during dormant season storms is the
second most  important mechanism by which fer-
tilizer nitrogen  may  enter the aquatic system.
Again, the use of adequate buffer strips will reduce
the potential impact on water quality. Nitrogen
that does enter  the  stream is rapidly decreased
through utilization by  biological communities in
the stream. Concentrations are further reduced by
dilution with downstream movement. Studies con-
ducted to date indicate that forest fertilization will
not result in degradation of water quality to the
detriment of other resources. With only one excep-
tion,  none  of the studies have recorded nitrogen
concentrations that approach the Public Health
Service maximum permissible levels for drinking
water  (Moore 1971,  Hornbeck and  Pierce 1973,
Moore 1975b, Sopper 1975, Norris and Moore 1976,
Newton and Norgren 1977).
                                              XI.22

-------
Behavior In The Aquatic Environment

  Forest fertilizers properly applied to an entire
watershed undoubtedly will change the nutrient
balance among soil, vegetation, animal life, and
water in the forest ecosystem, but should pose little
or no threat to water quality (Cole and  Gessel
1965). Fertilizers applied  directly  into streams,
however, do represent a potential problem, and the
total impact of the introduced chemicals will de-
pend on their behavior in the aquatic environment.
  When  urea nitrogen  is  introduced  into  small
streams of forested watersheds, either from wildlife
activity or through aerial application of fertilizers,
it disappears rapidly and only  traces can normally
be  detected  in undisturbed ecosystems. Urea is
hydrolyzed to ammonium nitrogen  by urease en-
zyme adsorbed on suspended solids and bottom
sediments. Ammonium nitrogen may remain  in
solution or be adsorbed by suspended organic and
inorganic colloids and bottom sediments. All forms
of nitrogen are diluted by downstream movement
caused by natural stream mixing  and increased
flow volume from side streams and  ground water.
Dissolved inorganic and organic nitrogen may also
be removed by aquatic organisms to  such an extent
that they are undetectable at  a downstream sam-
pling point (Thut and Haydu  1971).
  Phosphorus is not considered a mobile element
in the soil system. Even those forms of phosphorus
that are readily available for plant uptake are not
subject to  leaching  to  any  significant  extent.
Phosphate fertilizer applied to a forest watershed
would not be expected to enter the stream system
except by direct application. Since most headwater
streams in relatively undisturbed forest watersheds
contain only low concentrations of phosphorus, the
small amounts of phosphorus added during a nor-
mal fertilization program would be rapidly utilized
by the biological community in the stream. Many
of the streams in  forested areas of the Douglas-fir
region are nutrient deficient, and it has been sug-
gested that forest  fertilization  may  have  a
beneficial  effect  on  forest stream  productivity
(Thut and Haydu 1971).

  The fate of nitrogen applied to cultivated crops
has been  studied extensively  (Allison  1966), but
only limited data are available on the nitrogen cy-
cle  in temperate forests (Cole and  others 1967,
Weetman  1961). The output of nitrogen in drainage
from  actively growing forest  stands  appears  to
nearly balance inputs in  precipitation  (Cooper
1969).  Since stream  enrichment resulting  from
forest fertilization is apparently small and of short
duration, it can be assumed  that any deleterious ef-
fects that do occur will not persist. However, the ef-
fect of small additions at  upstream  sites on ac-
cumulation of nutrients in  downstream impound-
ments must be considered.
                                              XI.23

-------
                                       CONCLUSIONS
  The amount of a particular chemical that enters
a stream will vary depending on many of the fac-
tors discussed in this chapter. Each of the compo-
nents of the forest environment indicated in figure
XI.2 can  be  designated  as  a  compartment in a
systems diagram or conceptual  model and the
various processes responsible for transformation or
movement of chemicals  within or between  com-
partments identified. With an  adequate  data base
for any given site and a thorough knowledge of the
controlling processes, one could then predict the
extent of non-point source pollution that would be
expected as the result of using  a silvicultural prac-
tice that includes the application of a pesticide or
fertilizer chemical. Although much is known about
the behavior  of chemicals in the environment, we
still  lack  a precise mathematical model that will
meet this  objective. Therefore, the major routes of
entry of chemicals into forest  streams have been
identified, and the processes  which  are involved
within each environmental compartment are iden-
tified and discussed primarily from a conceptual
and  qualitative  basis.   This  framework  should
provide a logical  basis  for  understanding the
mechanisms  and processes  which may  result in
non-point source contamination of stream water in
a  qualitative way even  though  quantitative  es-
timates are not yet possible.

  Based on research experience, history of use, con-
sideration of the manner in which most chemical
application operations  are conducted, and  an
analysis of the chemical and  physical properties
which influence the  behavior  of chemicals in the
environment, it is estimated that the following con-
centrations  of  various   chemicals  may  be en-
countered in the aquatic environment near treat-
ment areas.
  Herbicides. — A strong background of research
experience permits prediction with confidence that
concentrations  of  2,4-D, picloram, 2,4,5-T,  and
amitrole exceeding 0.05 mg/1 will seldom be en-
countered in streams adjacent to carefully control-
led forest  spray operations. Concentrations ex-
ceeding 1 mg/1 have never been observed and are
not expected to occur. The chronic entry of these
herbicides into streams for long periods after ap-
plication does not  occur.
  Insecticides. — Concentrations of carbamate in-
secticides exceeding 0.1 mg/1 will rarely be found in
forest streams. Carbamate and pyrethrum insec-
ticides do not persist in the environment and they
offer little opportunity for movement to streams.
The organophosphorous insecticide, malathion, is
rapidly degraded in soil and water and enters water
only by stream channel interception and  limited
streamside surface runoff.  Ultra-low-volume aerial
applications will rarely produce more than 0.5 mg/1
malathion in streams.
  Fertilizers. —  There  is  still  only a  limited
history of field use and research experience con-
cerning the behavior and fate of fertilizer nitrogen
introduced into the aquatic environment as a result
of  forest  fertilization.  Available  data  suggest,
however, that concentrations of the various forms
of nitrogen found in streams adjacent to  treated
units are well below accepted standards for public
water supplies. The impact of these introduced
chemicals on various elements of the ecosystem
must be investigated.
  Direct application to surface waters is the major
source  of aerially applied  forest chemicals in the
aquatic environment. Drift  is another important
pollution source with pesticides, but not with fer-
tilizer.  Careful selection of chemicals, carriers, and
equipment and control of the manner in which the
project is conducted can materially reduce both the
direct  application and the  drift of chemicals to
streams.  Specific  control  opportunities  were
described in Chapter II. Volatilization, adsorption,
degradation,  and  downstream   movement of
residues will minimize the exposure time of aquatic
organisms to chemicals which do enter the  aquatic
environment.
  The  forest manager has no control over the in-
herent  toxicity of a selected chemical, but the
hazards of chemical use to nontarget organisms can
be  minimized by limiting  their exposure to
biologically  insignificant doses.  Research ex-
perience and history of use have established that
important forest chemicals offer minimum poten-
tial for pollution of the aquatic environment when
they are used properly. The key to proper use is an
understanding of the ways  which chemicals can
enter streams and an appreciation of the factors
which  influence  the degree to  which these
mechanisms operate.
                                             XI.24

-------
                                   LITERATURE CITED
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                                             XI.25

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Cope, 0. B. 1966. Contamination of the fresh water
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                                              XI.26

-------
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                                             XI.27

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                                              XI.28

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  pasture soils of Nebraska. Weed Sci. 17:486-488.

Smith, G.E., and D.G. Ison. 1967. Investigation of
  effects of large-scale applications of 2,4-D  on
  aquatic fauna and water quality. Pestic. Monit.
  J.
Soileau, J.N. 1969. Effects of fertilizers on water
  quality. 107 p. Term. Val. Auth., Muscle Shoals,
  Ala.

Sopper, W.E. 1975. Effects of timber harvesting
  and related  management  practices on water
  quality in forested watersheds. J. Environ. Qual.
  4(l):24-29.

Stephens, R. 1975a. Effects of forest fertilization in
  small streams in the Olympic National Forest,
  spring 1975. Unpubl. For. Serv. Rep. 43 p. Olym-
  pia, Wash.

Stephens, R. 1975b. Effects of forest fertilization in
  small streams on the Olympic National Forest,
  fall 1975. Unpubl. For. Serv. Rep. 40 p. Olympia,
  Wash.

Stephens, R. 1976. Effects of forest fertilization in
  small streams in the Olympic National Forest,
  Quileene Ranger District, spring. Unpubl. For.
  Serv. Rep. 36 p. Olympia, Wash.

Tarrant, R.F., D.G. Moore, W.B. Bollen, and B.R.
  Loper. 1972. DDT residues in forest floor and soil
  after aerial spraying, Oregon, 1965-1968. Pestic.
  Monit. J. 6(l):65-72.

Thut, R.N., and E.P. Haydu. 1971. Effects of forest
  chemicals on aquatic life. In Forest and land uses
  and stream  environment symposium
  proceedings. J.T.  Krygier and J.D. Hall, eds.
  Oreg. State Univ., Corvallis.
Tiedemann, A.R. 1973. Stream chemistry following
  a forest fire and urea fertilization in north central
  Washington. USD A For. Serv. Res. Note PNW-
  203, 20 p. Pac. Northwest. For. and Range Exp.
  Stn., Portland, Oreg.

Tiedemann, A.R., and G.O. Klock. 1973. First-year
  vegetation after fire reseeding and fertilization
  on the Entiat Experimental Forest. USDA For.
  Serv. Res. Note PNW-195, 23 p. Pac. Northwest.
  For. and Range Exp. Stn., Portland, Oreg.

Trichell, D.W.,  H.L.  Morton, and M.B. Merkle.
  1968. Loss of  herbicides in runoff water. Weed
  Sci. 16:447-449.

Union Carbide Corporation. 1968. Technical infor-
  mation on Sevin carbaryl insecticide. Union Car-
  bide Corp. 10G-0449A Bookl. 56 p.

U.S. Department of Agriculture. 1964. The effects
  of the  1964 gypsy moth treatment program in
  Pennsylvania  and New Jersey on the  total en-
  vironment.  USDA  Agric.  Res.  Serv.,
  Moorestown, N.J. Unpubl.

U.S. Department of Agriculture. 1977. U.S. Forest
  Service pesticide use report for FY1976 and tran-
  sition quarter. 19 p. Mimeo.

Watkins, S.H., R.F. Strand, D.S. DeBell, and J.
  Esch,  Jr. 1972. Factors  influencing ammonia
  losses from urea applied to northwestern forest
  soils. Soil Sci. Soc.  Am. Proc. 36(2):354-357.

Weetman,  G.F. 1961. The nitrogen  cycle  in
  temperate forest stands. Woodland Res. Index,
  Pulp Pap. Res. Inst. Can.  No. 126, 28 p.

Weetman, G.F.,  and S.B. Hill. 1973. General en-
  vironmental and biological concerns in relation
  to forest fertilization. In Forest fertilization sym-
  posium proceedings. USDA For.  Serv. Gen.
  Tech. Rep. NE-3, p. 19-35. Northeast For. Exp.
  Stn., Upper Darby, Pa.

Weiss, C., T. Nakatsugawa, J.B. Simeone, and J.
  Brezner.  1973. Gas  chromatographic analysis of
  spray  residues in  a forest environment  after
  aerial spraying of Dylox. In Environmental im-
  pact and efficacy of Dylox used for gypsy moth
  suppression in New York state, p. 15-25. Appl.
  For. Res. Inst., N.Y. State Coll. For., Syracuse,
  N.Y.

Wells, L.F., Jr. 1966. Disappearance  of carbaryl
  (Sevin) from oak foliage in plots aerially sprayed
                                             XI.29

-------
  for control  of gypsy moth on Cape Cod, Mas-     Wilcox, H.H. III. 1971. The effects of Dylox on a
  sachusetts,  in 1965. In Report of the surveillance       forest ecosystem. Lake Ont. Environ. Lab., Prog.
  program conducted in  connection with  an ap-       Rep. State Univ. Coll..  Oswego, N.Y.
  plication of carbaryl (Sevin) for the control of
  gypsy moth on Cape Cod, Massachusetts. Com-
  monw. Mass. Pestic. Board Publ. 547, p. 12-17.     Wilcf>x-  H-H .  ™-  1972  Environmental  impact
                                                    study <>t aerially applied Sevm-4-Oil on a forest
Wiese, A.F.,  and R.G.  Davis.  1964.  Herbicide       and aquatic   ecosystem.  Lake  Ont.  Environ.
  movement in soil with various amounts of water.       Lab.. Prog. Rep. (Dec. 7), 55 p. State Univ. Coll.,
  Weeds 12:101-103.                                  Oswego, N.Y.
                                             XL 30

-------
                                          APPENDIX XI.A
                       WATER QUALITY DATA — PESTICIDE CHEMICALS
                     Table XI.A.1.—Cascade Creek Unit, Alsea Basin, western Oregon (Morris 1967)
                     Sample points1
                 Sample point 4
                                Sample point 5
                Hours after
                 spraying
2,4,5-T
Hours after
 spraying
2,4,5-T
Hours after
 spraying
2,4,5-T
                                                           M9/I
0.05
0.62
1.28
2.0
4.0
5.2
9.8
24.7
48.2
274.8
0
16
7
4
4
4
4
2
1
1
0.17
1.33
2.2
3.9
5.4





1
2
1
1
0





0.27
1.40
2.0
3.9






lost
3
3
0






                'Entire watershed feeding the sampled stream was sprayed.
                2Herbicide was detected for 16 weeks at sample point 3.
Figure XI.A.1.—Cascade Creek Treatment Unit. (26 ha (2%)
  of a 1400-ha watershed was treated with 2.24 kg/ha 2,4,5-T.
  Large streams not included in treatment area.) (Morris
  1967).
                                                                            I mile
                                                  XI.31

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                        Table XI.A.2.—Eddyville Unit, Yaquina Basin, western Oregon' (Morris 1967)
                      Sample point 12
                                Sample point 13
                                                                                Sample point 14
                 Hours after
                  spraying
               2,4-D
                Hours after
                 spraying
                                                               2,4-D
                             Hours after
                              spraying
                                                                          2,4-D
                                                                                             M9/I
0.83
1.83
2.8
Z53.5

33
13
13
9

1.33
2.3
3.3
4.3
253.6
62
71
58
44
25
1.38
2.3
3.3
4.3
Z53.6
30
44
25
23
11
                 1Rate of application was 2.5 to 3.36 kg/ha.
                 2No further residues detected although sampling continued for 10 months.
Figure XI.A.2—Eddyville Treatment Unit. (20 ha (10%) of a
  287 ha watershed was treated with 2,4-D (LVE) at rates
  ranging from 2.5 to 3.36 kg/ha. Sampled streams flowed
  from or through treatment area.) (Morris 1967).
Table XI.A.3.—Concentration of 2,4-D in West Myrtle Creek,
   Malheur National Forest, eastern Oregon' (Morris 1967)
       Sample point 1
                Sample point 22
   Hours after
    spraying
2,4-D
Hours after
 spraying
2,4-D
1.7
3.7
4.7
6.0
7.0
8.0
9.0
13.9
26.9
37.9
78.0
80.8
168.0

132
61
85
10
26
75
59
51
3
9
8
1
0

2.0
3.9
5.0
6.2
7.2
8.2
9.2
14.1
17.0
38.0
77.8
81.0
104.8
168.0
0
0
0
2
7
8
13
14
7
6
9
9
3
1
  'Rate of application was 2.24 kg/ha.
  2Sampling point 2 is 1.6 km downstream from point 1
                                          North
                                                                     I mile
                                          Figure XI.A.3.—West Myrtle Treatment Unit (240 ha treated
                                            in one block. Live streams Included In the treatment area.)
                                            (Morris 1967).
                                                      XI.32

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          Table XI.A.4.—Camp Creek Spray Unit,
             Malheur National Forest, eastern
                  Oregon1 (Morris 1967)
       Hours after
        spraying
                            2,4-D
           0.1
           2.0
           5.4
           8.8
          84.5
         168.0
                              o
                             25
                              1
                              1
                              3
                              0
  1Rate of application was 2.24 kg/ha.
                                                              North
                                                              Figure XI.A.4.—Camp Creek Spray Unit. (121 ha treated with
                                                                2.24 kg/ha 2,4-D (low volatile esters). Spray boundaries ad-
                                                                jacent to, but did not include, live streams.) (Morris 1967).
Table XI.A.5.—Concentration of 2,4-D in streams in Keeney-
             Clark Meadow eastern Oregon1
                      (Norris 1967)
  Hours after
   spraying
2,4-D
Hours after
 spraying
  1Rate of application was 2.24 kg/ha.
2,4-D
0.7
2.5
3.1
3.6
4.1
6.1
8.1
9.6
840
48
128
106
106
121
176
138
14.3
37.8
56.4
100.1
103.6
289.9
297.0

113
91
76
115
95
5
7

                                                                                                                  pelat
                                                              Figure  XI.A.5.— Keeney-Clark Meadow Spray Units. (89 ha
                                                                treated with 2.24 kg/ha 2,4-D. Flat, marshy area with many
                                                                small live streams and other sites  with standing water.)
                                                                (Norris 1967).
                                                       XI.33

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Table XI.A.6.—Concentration of Amitrole-T in Wildcat Creek,
             Coast Range, western Oregon1
                (Morris and others 1966)
       Sample point 2
                  Sample point 3
  Hours after
   spraying
Amitrole-T
Hours after
 spraying
                                           Amitrole-T
0.05
0.39
0.74
1.13
1.43
1.73
2.1
3.3
4.8
5.8
7.1
8.1
9.5
10.4
15.3
26.1
30.1
46.1
71.5
1
30
35
37
17
16
19
21
12
8
5
4
3
2
1
7
4
2
0
0.05
0.33
0.67
1.07
1.38
1.60
2.0
2.8
4.2
5.2
6.9
8.0
10.3
15.2
20.5
26.0
45.7
69.4

0
0
9
90
110
40
35
24
14
7
5
5
3
2
25
8
3
0

  'Rate of application was 2.24 kg/ha.
                                                                                     I mile
                                                                      ©	*»   Sampling Point

                                                                                 Stream

                                                                                 Watershed Boundary
                                                            Figure XI.A.6.—Wildcat Creek Spray Unit. (28 ha treated with
                                                              2.24 kg/ha amitrole-T. Spray units include live streams.)
                                                              (Norris and others 1966).
                                                     XI.34

-------
Table XI.A.7.—Concentration of amitrole in stream water,
       loss or dilution with downstream movement.
       Amitrole-T applied to 105 ha at 2.24 kg/ha1
                (Morris and others 1967)
Hours after
spraying
hours
0.1
0.5
1
2
3
4
5
6
8
10
12
14
24
35
48
72
Amitrole concentration on
sampling point
1


1
5
7
45
24
8
10
9
3
2
1
1
1
1
0
0
2


0
0
2
42
15
18
5
5
3
2
1
1
2
0
0
0
3
iin/l
M9'1 	 	
0
0
0
0
0
4
6
6
12
2
2
2
1
1
0
0
4


0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
  'Study was conducted in Coast Range of Oregon. Sampling
point 1 was located just below boundary of sprayed unit; point 2
was 3.2 km downstream from point 1; point 3 was 0.48 km below
point 2; and point 4 was  1.49 km below point 2. No detectable
quantity of amitrole was found between 3 and  150 days after treat-
ment.
                                                                              Watershed Boundary
                                                                               (Area =244 hectares )
                                                                             Treatment Boundary
                                                                              (Area =67 hectares )
                                              Figure XI.A.7.—Farmer Creek Treatment Watershed. (67 ha of a 244 ha
                                                watershed sprayed by helicopter with 1.12 kg dicamba and 2.24 kg 2,4-D
                                                per ha. Sampling point 1 is about 1.3 km from edge of treated unit) (see
                                                table XI.A.8) (Morris and Montgomery 1975)
                                                      XI.35

-------
 Table XI.A.8.—Concentration of dicamba in Farmer Creek' (Morris and Montgomery 1975)
Sampling date

6/05/71
6/07/71



















6/08/71

6/09/71
Hours after
application
hours
(prespray)
0.3
0.6
1.0
1.2
1.7
2.1
2.5
2.7
3.3
3.8
4.3
4.8
5.2
6.2
6.8
7.8
8.8
10.2
13.1
22.8
30.1
37.5
50.2
Dicamba
M9/I
0
0
0
0
0
0
1
0
0
3
12
16
28
37
33
30
27
24
16
11
6
2
0
0
Sampling
date

6/10/71
6/11/71
6/13/71
6/16/71
6/18/1
6/21/71
6/30/71
7/08/71
7/09/71
8/11/71
8/20/71
8/25/71
9/01/71
9/02/71
9/07/71
9/29/71
10/19/71
11/17/71
11/29/71
12/22/71
5/18/72
6/08/72
6/30/72
7/28/72
Dicamba
/ug/i
2
4
9
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
'Coastal Oregon; 67 ha treated with 1.12 kg/ha dicamba and 2.24 kg/ha 2,4-D.
                                     XI.36

-------
                                            STREAM DISCHARGE AND PRECIPITATION
Figure  XI.A.8—Precipitation,
 stream discharge, and con-
 centrations of tryclopyr In
 stream water following ap-
 plication of 3.36 kg/ha  by
 helicopter  to  a  small
 watershed  In southwest
 Oregon In May 1974  (Morris
 and others 1976b).
 A. First 20 hours after ap-
 plication.

 B. First significant storm ac-
 tivity, channel flushing.
                                      E
                                      o
                                      <
                                      cc
                                    .a
                                    a.
                                    a.
                                    O)
                                    DC
                                    LU
                                    LU
 CO
 LU
 cc
                                       80
                                       40
                                                       No Rain
                                                       No Stream Discharge
         i  i  i  i  i  i  i  i   i  i  i   i  i  i   i  i  i  i   r
                     Triclopyr in Water
                                            i  i  i  i  i   i
     4        8        12       16
TIME AFTER APPLICATION, (hours)
20
                                    Is

                                    I 2
                                    z"
                                    < 1
                                    CC
                                   Q.
                                   Q.
                                     '16
                                   O)
                                      12
co 4
LU
CC
   0
                                                               B
                                            STREAM DISCHARGE AND PRECIPITATION
              Rain
              Stream
              Discharge
                                                        120
                                         o Malfunction
                                                   Triclopyr in Water
                                          i  i  i   i  i  i  i   i  i
                                         28   30   1
                                         OCTOBER
                                    o—o Concentration

                                     f|f  Discharge
                                                                                        I
                         5   7   9   11
                          NOVEMBER
                            DATE
                            13  15   17
                                            XI.37

-------
  Table XI.A.9.—Concentrations of 2,4-D and plcloram In
        drainage waters from a 7-ha hill-pasture
watershed in southwest Oregon1 (Norrls and others 1976a)
Date

9/18/69
10/09/69
10/13/69
10/21/69
11/14/69
11/24/69
12/01/69
12/09/69
12/19/69
12/24/69
1/01/70
1/24/70
Rain


7.9

3.0
5.0
—
0.1
2.0
6.8
9.9
4.6
18.6
2,4-D

	 /
0
22
0
3
0
0
0
0
0
0
0
0
Picloram
,n/l 	
110
43
64
39
0
0
0
0
0
12
1
0
  'Rate of application—2.3 kg picloram and 4.6 kg 2,4-D in 93.5
I/ha applied as Tordon 212 by helicopter.
                                    WATERSHED, SAMPLING STATIONS AND RATE OF APPLICATION
                                                                                        LEGEND
                                                                                     "S"Weir
                                                                                      • Interception Disc
                                                                                     O Cluster
                                                                                      Intermittent Stream
                                                    0   30  60   90   I2O  150  180  BO  240  270
                                                                 SCALE, METERS
                                         Figure XI.A.9.—Boyw Ranch, MuthwMt Oregon. Small  7-ha hlll-pattura
                                              •pray unit treated with Tordon 212 (Norrls and others 1976a).
                                                XI.38

-------
 Table XI.A.10.—Total DDT content of stream water flowing
  from sprayed area — before treatment and for 3 years
       after treatment1 (Tarrant and others 1972)
   Date
  Days
  after
spraying
Total DDT residues In
 Rattlesnake Creek
                        East Fork
           West Fork
5/24/65
6/19/65
6/23/65
7/14/65
8/26/65
11/17/65
6/07/66
7/19/66
11/09/66
7/04/67
11/07/67
7/16/68
11/12/68
-30
- 4
1
21
64
147
349
391
505
742
869
1,131
1,251
<
ND
.104
.031
.028
.014

.010
ND
ND
.032

.010

ND
.277
.022
.015
ND
ND


ND
.010


  'Area sprayed with DDT at rate of 0.84 kg/ha.
  'Blank = levels of DDT isomers and metabolites less than 0.01
mg/l but greater than 0.002 mg/l.
  ND = not detected
                                                 HERBICIDE    DISCHARGE
                                                                                           Area in Stream
                                                                                 Discharged     Channel
                                                                  Total Applied  Total    %    % of Total
                                                    ^  2,4-D       29800 g    6g     0.02   0.21
                                                    ^  Picloram    14900g    43g     0.29   0.2I
V)
§>20
uT
o
X
HERBICIDE DISC
D 01 6

—
-
"l
I
fwrt 777\
!
W(
1
1
1

HI Picloram -
—
                                i	OCTOBER	1 ^^JOVEMBER^
                                •3-ld 11-201 I2I-3B •-! • 12-301

                                        SAMPLING    PERIOD
                          Figure XI.A.10.—Discharge of herbicide In streamflow from small 7-ha hill-pasture watershed,
                            Boyer Ranch, southwest Oregon. Treatment was with Tordon 212 at 2.3 kg picloram and 4.6 kg
                            2,4-D per hectare (Norrls and others 1976a).
                            Note: All of the herbicide discharged with streamflow is accounted for by the quantity applied to
                            the stream channel and adjacent banks. (The question mark for the period December 21 through
                            31 reflects equipment malfunction resulting in no measure of stream discharge.)
                                                 XI.39

-------
Table XI.A.11 .—Concentration of herbicides in water samples,
  as determined by odor tests1 (Reigner and others 1968)
     Herbicide and time
         of sample
Pennsylvania    New Jersey
  streams       streams
                               M9/I
2,4,5-T butory ethanol ester:
  Immediately after spraying      40
  4 hours later                  20
  Next 9 samples2               ND3
  After first large storm           10
2,4,5-T emulsifiable acid:
  Immediately after spraying      40
  4 hours later                  10
  Next 9 samples2               ND
  After first large storm           20
All downstream samples
  (both herbicides)              ND
40
20
ND
ND


20
ND
ND
ND


ND
   'Test panel used procedure approved by American Society for
 Testing and Materials.
   2Samples taken daily for first week; twice a week for next 2
 weeks.
   3ND = no detectable odor.
                                                    Figure  XI.A.11.—Concentration  of
                                                     endrin  in  streamflow  after aerial
                                                     seeding  with  endrin-coated
                                                     Douglas-fir  seed.  Needle  Branch
                                                     Watershed—seed treated with 1.0%
                                                     endrin  and sown at 0.84 kg/ha;
                                                     Watershed  1,  H.J.  Andrews  Ex-
                                                     perimental Forest—seed treated at
                                                     0.5% endrin and sown at 0.56 kg/ha
                                                     (Moore and others 1974).
                                                                   NEEDLE BRANCH
                                                             18 December 1967-12 January 1968
                                   I
                                   if
                                   UJ —
                                   cc
                                                        100
                                                                   200         300        400

                                                                     HOURS AFTER SEEDING
                                                                         500
                                         O.OSf—
                                           WATERSHED NO. 1
                                           30 October 1967
                                                                                   MEAN STREAMFLOW
                                                                                        0.049 m'/s
                                                                        2            3
                                                                    HOURS AFTER SEEDING
                                                                                   J
                                                                                    5
                                                    XI.40

-------
                    Table XI.A.12.—Concentrations of 2,4-D and 2,4,5-T herbicide In water samples from
                     Monroe Canyon, San Dlmas Experimental Forest, northeast of Glendora, California
                                            (Krammes and Wlllets 1964)1
                     Date
          Site
                                                Weir
 Surface
WelM
Well 2

May 10/61
May 22/61
June 5/61
July 24/61
July 31/61
Aug. 28/61
Sept. 25/61
Oct. 30/61
Jan. 29/62
Feb. 26/62
June 20/63

0.00
.00
.05
.05
.00
.00
.00
.00
.00
.00
.00

	 PI
—
0.09
.03
.00
.00
.00
.00
—
—
—


—
0.01
.00
.00
.00
.04
.00
...
—
—


—
0.01
.00
.00
.01
.00
.00
—
—
—
                 'The riparian zone and intermediate slopes of a 354-ha watershed were hand sprayed several times
               with a mixture of equal parts of 2,4-D and 2,4,5-T in diesel oil. Care was taken to avoid any direct con-
               tamination of the stream. A total of 1701 of herbicide was applied on May 10,1961, but actual rates of ap-
               plication are not known. Maintenance spraying was carried out again in June,  1963, also followed by
               hand spraying at later dates. Stream contamination was below the safe limit of 1 ppm. No traces of diesel
               oil were found. Riparian zone vegetation was handsprayed during the week following the May 22, 1961
               sampling and just before the June 20, 1963 sampling.
              2.0
               1.5
                                  CLEARCUT   WATERSHED
               i.o-
                .5-
                             STREAMFLOW   -
                             AREA  INCHES/DAY
       BROMACIL
             PPM
                     J   J  ' A '  S  ' 0   N   D  I  JFMAM    J '  J  ' A '  S '
                               1966                             1967
Figure  XI.A.12.—Water yield and bromacll release  from
  watershed 2, Hubbard Brook Experimental Forest,  West
  Thornton, New Hampshire (Pierce 1969).
Note: Watershed 2  (15.8 ha) was clearcut of all timber and
woody vegetation in late fall and early winter of 1965. In June
1966, bromacll was  broadcast sprayed by helicopter at a rate
of 28 kg/ha. Persistent sprouts were sprayed with 2,4,5-T in
the summer of 1967. About 20 percent of the bromacil left the
watershed through the stream in Vk years. The concentration
of 2,4,5-T in the stream was less than  1  mg/l for the entire
period following application.
                                                    XI.41

-------
         cr
         a.
         in
CD

ce
LlJ
0.
(Ł
2
g
i-
<
                                                                   Q
                                                                   z
                                                                   o
                                                                   o
                                                                   UJ
                                                                   in
10    15   20

    MAY
                                               15   20

                                             JUNE
                                                                          15   20

                                                                         JULY
 10    IS

AUGUST
                                                                                                         20   25
        Figure XI.A.13.—Atrazine concentration in streamflow during and for 31/z months after herbicide treatment
                                            (Douglas and others 1969).
        Note: A 9-ha watershed was treated May 3-6,1966, with 3.9 kg atrazine and 0.95 I technical paraquat per hec-
        tare, including the water course. Surviving vegetation was sprayed again on July 5-11 with a mixture of 3.36
        kg 2,4-D (isobutyl esters) and 5 kg atrazine per hectare, but a 3-m buffer strip was left unsprayed on both
        sides of the stream. Atrazine content in water samples from the stream is graphed above. Paraquat was
        detected in only 5 of more than 35 samples, and maximum concentration measured was 19 /jg/l. After the se-
        cond spraying, 2,4-D was never detected in the stream  and the concentration of atrazine did not increase,
        even  during storms.
                                                     XI.42

-------
                                       APPENDIX XL B
                      WATER QUALITY DATA — FERTILIZER CHEMICALS
                  Table XI.B.1.—Stream water quality following forest fertilization, fall 1975:
         Hoodsport-Quileene Ranger Districts, Olympic National Forest, Washington (Stephens 1975b)


    Treatment: Urea pellets were applied to several thousand acres of second growth Douglas-fir. As a general rule,
               stream buffer strips of 100 ft (30 m) were left along tributary streams which were flowing greater than
               0.5 ft3/sec (14 I/sec). 300 ft (91 m) wide buffer  strips were left along main streams.
       Site
     Rate of         Date of       Treatment
   application     application        area
Ib-N/ac  kg-N/ha
                      Range concentrations
                 Urea-N      NH3-N      NOs-N
McDonald Creek
  Pre-treatment
  Post-treatment

Jimmycomelately
  Pre-treatment
  Post-treatment

Gold Creek
  200      224    Oct.-Nov. 75
 ac       ha

316      128
                                                                                  -mg/l-
                                                0.01-0.02       0       0.03-0.05
                                                0.32-0.01     0-0.18     0.03-2.85
  200      224    Oct.-Nov.75     48       20
  200      224    Oct.-Nov. 75    229       93
                                                  0-0.05
                             0-0.07     0.03-0.13
Pre-treatment
Post-treatment
Elbo Creek
Pre-treatment
Post-treatment
Mile & V2 Creek
Pre-treatment
Post-treatment
Fulton Creek
Pre-treatment
Post-treatment
Waketickeh Creek
Pre-treatment
Post-treatment
0
0-0.31
200 224 Oct.- Nov. 75 33 13
0
0-0.28
200 224 Oct.-Nov. 75 169 68
0-0.02
0-0.22
200 224 Oct.-Nov.75 592 240
0
0-0.13
200 224 Oct.-Nov. 75 1432 580
0-0.01
0-0.84
0
0-0.22
0
0-0.10
0
0-0.02
0
0-0.10
0
0-0.55
0.02-0.05
0.02-0.18
0.01-0.02
0-0.07
0.06-0.07
0-0.92
0.01-0.02
0.01-0.09
0-0.02
0-0.40
                                                XI.43

-------
                 Table XI.B.2.—Stream water quality following forest fertilization, spring 1975:
         Hoodsport-Quileene Ranger Districts, Olympic National Forest, Washington (Stephens 1975a)
    Treatment: Urea pellets were applied by helicopter to several thousand acres of second growth Douglas-fir. As
               a general rule, stream buffer strips 200 ft (60 m) wide were left along streams which were flowing
               greater than 0.5 ftVsec (14 I/sec).	
    Site
     Rate of          Date of        Treatment
   application      application        area
Ib-N/ac kg-N/ha     	
                                           Range
                                       concentration
                                           NCh-N
Mile & 1/2 Creek
  Pre-treatment
  Post-treatment

Trap per Creek
  Pre-treatment
  Post-treatment

Salmon Creek
  Pre-treatment
  Post-treatment

Eddy Creek
  Pre-treatment
  Post-treatment

Jackson-Mar pie
  Pre-treatment
  Post-treatment

Turner Creek
  Pre-treatment
  Post-treatment
  200      224
Apr. 75
 ac       ha

292      118
  200      224      Apr. 75      200       81
  200      224      Apr. 75      112       45
  200      224      Apr. 75      240       97
  200      224      Apr. 75      460      186
  200      224      Apr. 75      286      116
                                                                         	mg/|	
                                                              0.01-0.03
                                                               0-0.18
                                                                -0.03
                                                              0.01-0.54
                                                                 0
                                                              0.03-0.65
                                                                 0
                                                               0-0.72
                                                               0-0.01
                                                               0-0.50
                                                               0-0.04
                                                               0-0.25
                                                XI .44

-------
Table XI.B.3.—Stream water quality following a wildfire and fertilization with reseeding for erosion control, 1971:
           Entiat Experimental Forest, central Washington (Klock 1971; Tiedemann and Klock 1973;
                                       and Helvey and  others 1974)


    Treatment: Following a wildfire in August 1971, three watersheds were monitored for water quality. Fox Creek
               was used as a control, Burns Creek was fertilized with ammonium sulfate and McCree Creek was
               fertilized with urea. An unburned watershed, Lake Creek was also monitored as an undisturbed con-
               trol.
Site
Fox Creek
Rate of
application
Ib-N/ac kg-N/ha
Control
Dates of
appli-
cation
Percent of
total
applied
no application
Treatment
area
ac ha
1,169 473
Peak concentrations
Urea-N NCh-N NH4-N
	 mg/l 	 •
  Pre-treatment
  Post-treatment

McCree Creek
     1970
     1971
                                               10.035
                                               N.D.
                                                  N.D.2
                                                  N.D.
                                              N.D.
                                              N.D.
 48
urea
54
10/30/70
11/05/70
11/08/70
 7.5
24.3
68.2
1,270
513
Pre-treatment
Post-treatment
Burns Creek
Pre-treatment
Post-treatment
Lake Creek
1970
1971
51 57
(NH4)2SO4
1970
1971
Control
1972

10/30/70
11/09/70

13.6
86.4
N.D.
0.616
1,394 564
N.D.
0
no application
N.D.
0.210
N.D.
0.068
0.065
N.D.
<0.02
N.D.
0

   'Attributed to wildlife activity
   2N.D.—Not detected, concentration below detection limit of equipment.
                                                  XI.45

-------
                 Table XI.B.4.—Stream water quality following forest fertilization, 1970:
                      Mitkof Island, southeast Alaska (Meehan and others 1975)
Treatment: Two areas of cutover land were fertilized
Site Rate of Date of
application application
Ib N/ac kg N/ha


Falls Creek
Control
1970
1971
Treated 190 210 May 70
1970
1971
Three Lakes
Control
1970
1971
Treated 190 210 May 70
1970
1971
N.D. = Not Detected
in May 1970 by helicopter with
Treatment Urea-N
area




—
N.D.
N.D.
—
N.D.
N.D.

—
N.D.
N.D.
—
N.D.
N.D.

urea pellets.
NOa-N


iiiy/i


0.23
0.24

1.26
1.66


0.20
0.18

2.36
0.30


NHs-N





0.23
0.11

1.28
0.11


0.10
0.12

0.14
0.08

Table XI.B.5.—Stream water quality following forest fertilization of two small watersheds, 1970 and 1971:
                 Sluslaw River Basin, western  Oregon (Burrough and Froehlich 1972)


 Treatment:  Two watersheds, Nelson Creek and Dollar Creek, were fertilized by helicopter with  urea pellets.
            There were no buffer strips established along watercourses within the treated area. Untreated adja-
            cent watersheds were also monitored  as a control.
Site:
Rate of Date of Treatment Peak Concentration
application appli- area Urea-N
Ib-N/ac kg-N/ha cation
NHa-N
NOa-N
ac ha 	 	 mg/l 	
Nelson Creek
treated
untreated
Dollar Creek
treated
untreated
200 224 Apr. 70 94
8.6
0.20
200 224 Apr. 71 85
44.4
<0.02

0.32
0.33

0.49
0.15

7.6
4.3

0.13
0.16
                                              XI.46

-------
   Table XI.B.6.—Stream water quality following fertilization of forested watershed on the Olympic Peninsula,
          spring 1970: Quileene Ranger District, Olympic National Forest, Washington (Moore 1975b)


    Treatment:  Two watersheds, Jimmycomelately and Trapper Creek, were fertilized by helicopter with urea. Pel-
                letlzed or large granule forest grade urea was unavailable so agricultural grade was used. Drift of the
                fertilizer was noted. The stream was flagged and fertilizer was not applied within 200 ft (60 m) of the
                stream.
Site:
Jimmycomelately
Pre-treatment
Post-treatment
Trapper
Pre-treatment
Post-treatment
Rate of Date of Treatment Peak Concentration
application appli- area Urea-N
Ib-N/ac kg-N/ha cation

200 224 Apr. 70 120 49
0
0.71
200 224 Apr. 70 158 64
0.013
0.71
Ntft-N

<0.004
0.04
<0.004
0.01
N03-N

0.002
0.042
0.055
0.121
     Table XI.B.7.—Stream water quality after fertilization of a small forested watershed on the west slopes
                     of the Cascade Mountains, 1970: Oregon (Malueg and others 1972)


    Treatment: A watershed was fertilized by helicopter with urea pellets. No effort was made to prevent the direct
               application of urea into the water courses.
    Site:
      Rate of         Date of       Treatment
    application        appli-           area
Ib-N/ac   kg-N/ha    cation	
                                              Cencentrations
                                                                           NH4-N
                                                   NO2-N
                                                    NOa-N
Crabtree Creek
  Pre-treatment
  Post-treatment
  200
224
May 70
 ac

569
 ha

230
                                                                         	mg/l	
                                                     <0.01
                                                     <0.08
                                                   <0.01
                                                   <0.01
                                                    <0.01
                                                    <0.25
                                                 XI.47

-------
   Table XI.B.8.—Stream water quality after fertilization following wildfire in north-central Washington, 1970:
                                   Chelan, Washington (Tiedemann 1973)
Treatment: Urea fertilization following wildfire. Falls Creek was
Grade Creek was unburned and unfertilized.
Site:
Falls Creek
Pre-treatment
Post-treatment
Camas Creek
Grade Creek
fertilized, Camas Creek was not fertilized, and
Rate of Date of Treatment
application appli- area
Ib-N/ac kg-N/ha cation
ac
70 78 Oct. 70 6,180
1,680
6,920

ha
2,500
680
2,800
Peak Concentrations
Urea-N

0.330
0.029
0.006
1 0.450
NHa-N

0.011
0.011
0.001
0.011
NOa-N

0.016
0.310
0.042
0.016
'Attributed to animal activity.
     Table XI.B.9.— Stream water quality following forest fertilization, spring 1976: Quileene Ranger District,
                              Olympic National Forest, Wash. (Stephens 1976)
Treatment: Urea pellets were applied to 800 ac of second-growth Douglas-fir. As a general rule, stream buffer
strips 100 ft (30 m) wide were left along tributary streams which were flowing greater than 0.5 ftVsec
(14 I/sec); 300 ft (91 m) wide buffer strips were left along main streams.
Site:



Townsend Creek
Pre-treatment
Post-treatment
Big Quileene
River
Pre-treatment
Post-treatment
Rate of Date of Treatment Range Concentrations
application appli- area NHa
Ib-N/ac kg-N/ha cation


200 224 Apr. 76 102 41
0
0-0.11

200 224 Apr. 76 800 324
0-0.03
0-0.05
NOa




0-0.05
0-0.008


0-0.06
0-0.09
Urea




0-0.02
0-0.75


0-0.01
0-0.04
                                                 XI.48

-------
Table XI.B.10.—Stream water quality and quantity of flow following fertilization of a forested watershed, 1971:
                      Fernow Experimental Forest, W.Va. (Aubertin and others 1973)
Treatment: Hardwood sprouts and seedlings were fertilized by helicopter with urea. No attempt was made to
avoid a small perennial stream.
Site:
Rate of Date of Treatment Concentration

application appli- area NH4-N NOs-N

Treated
1970-1971
1971-1972
Control
1970-1971
1971-1972
Ib-N/ac kg-N/ha cation max ave max

230 258 May 71 74 30
0.8 0.23 19.8
0.19
-« — - -.- ... ...
0.19
0.20
ave

0.76
0.10

0.10
0.21
       Table Xl.8.11.—Stream water quality following fertilization of a  gaged experimental watershed,
                   spring 1970: South Umpqua Experimental Forest, Oreg. (Moore 1971)
Treatment: Watershed 2 was fertilized in March 1970 by helicopter. Urea, prill formulation, was applied and
there was no attempt made to leave an untreated buffer zone along the stream. Watershed 4 was un-
treated and served as a control.
Site:
Watershed 2
Watershed 4
Rate of Date of
application appli-
Ib-N/ac kg-N/ha cation
200 224 Mar. 70
Treatment
area
ac ha
169 68
120 49
Concentrations
Urea-N NHa-N

1.39 0.048
0.006 0.005

NOs-N

0.177
0.002
                                               XI.49

-------
        Table XI.B.12.—The impact of forest fertilization on stream water quality in the Douglas-fir region—
         a summary of monitoring studies in Alaska, Idaho, Oregon, and Washington (Moore 1975a, 1977)
Treatment: Aerial application of urea.
Site: Rate of Date of
application appli-
|b-N/ac ka-N/ha cation


Burns Creek1
Canyon Creek
Coyote Creek
Crabtree Creek
Dollar Creek
Elochoman Creek
Fairchilds Creek
Falls Creek
Jackson Creek
Jimmycomelately Creek
McCree Creek
Mica Creek
Mill Creek
Nelson Creek
Newaukum Creek
Pat Creek
Quartz Creek
Roaring Creek
Row Creek
Skookumchuck Creek
Spenser Creek
Tahuya Creek
Thrash Creek2
Three Lakes Creek
Trapper Creek
Trout Creek
Turner Creek
Waddel Creek
Wish bone Creek


50
200
200
200
200
200
200
190
150
200
50
200
200
200
150
200
200
200
150
150
200
200
200
190
200
200
200
200
200
Treatment
area


56
224
224
224
224
224
224
213
168
224
56
224
224
224
168
224
224
224
168
168
224
224
224
213
224
224
224
224
224

Nov1970
Nov1969
Mar 1970
May 1969
Apr 1971
Nov1969
Apr 1972
May 1970
May 1969
Apr 1970
Oct1970
Sep1972
Dec 1969
Apr 1970
Sep 1971
Apr 1972
May 1972
Mar 1972
Oct1972
Sep 1969
Nov 1972
Oct1972
May 1974
May 1970
Apr 1970
Mar 1968
Mar 1972
Dec 1969
May 1972
ac
1390
3325
170
570
85
735
475
650
235
120
1265
115
565
95
6085
600
125
660
6500
470
7680
4005
300
170
160
1600
870
1480
115
ha
562
1346
68
230
34
297
192
263
95
49
513
47
228
38
2463
243
51
267
2630
191
3108
1620
121
69
64
648
352
600
46
Urea-N
Pre- Post-
treatment
Peak Concentration
NHs-N NOs-N
Pre- Post-
treatment
Pre- Post
treatment

	 my /i 	
0
0.005
0.006
—
0.016
0.073
0.008
nd
0.007
0.002
0
0
0.02
0.016
0.009
0.003
0.004
0.007
0.006
0
0.019
0.01
—
nd
0.008
0.10
0.004
0.01
0
0
15.20
1.39
24.00
44.40
19.10
23.40
nd
0.09
0.71
0.62
0.30
0.68
8.60
0.26
3.26
1.75
0.76
0.13
2.63
0.37
27.20
—
nd
0.70
14.00
4.36
2.48
0.30
0
nd
0.005
0
0.030
nd
0.009
0.020
0.004
0
0
0
0
0.010
0
0.007
0
0.004
0.005
0.004
0.041
0
nd
0.015
0
0.12
0
0
0
0
nd
0.048
0.080
0.490
nd
0.280
1.28
0.044
0.040
0
0
0.12
0.32
0.008
0.079
trace
0.040
0.022
0.026
0.123
1.40
0.06
0.13
0.010
0.700
0.046
0.340
0
0
0.005
0.002
0
0.060
nd
0.030
0.015
0.065
0.005
0
0.15
0.02
0.290
0.011
0.061
0.120
0.017
0.004
0.005
0.005
0.01
nd
0.003
0.034
0.03
0.032
0.02
0.12
0.068
0.80
0.177
0.25
0.13
4.00
0.828
1.67
0.116
0.042
0.210
0.28
1.32
2.10
0.438
0.388
0.70
0.210
0.044
0.085
0.005
1.83
1.88
2.36
0.121
0.160
0.243
0.99
0.28
1(NH4)Z SO4 applied
"NhUNOa applied
nd = no data available or not determined
                                                XI.50

-------
                                      APPENDIX XI.C:

                    REFERENCE SOURCES FOR PESTICIDE CHEMICALS
Common name:
Chemical name:

Other names:

Registered use:
2,4-D
2,4-dichlorophenoxyacetic
acid
Stauffer, Esteron, Amine,
Dacamine
Control method for herbaceous
and woody plants on cropland,
forest,  and rangeland,  in
orchards, on fallow land, and
in pastures.
                  References

Bjorklund, N.-E., and K. Erne. 1966. Toxicological
  studies of phenoxyacetic herbicides in animals.
  Acta Vet. Scand. 7:364-390.
Gratkowski, H.J. 1961.  Toxicity of herbicides on
  three northwestern conifers.  U.S. Rep. Agric.
  For. Serv., Pac. Northwest For. and Range Exp.
  Stn., Stn. Pap. 42. 24 p. Portland, Oreg.
House, W.B., L.H. Goodson, H.M.  Gadberry, and
  K.W. Docktur. 1967. Assessment of ecological ef-
  fects of extensive or repeated use of herbicides.
  Final rep. Midwest Res.  Inst. Proj. 3103-B. Adv.
  Res. Proj. Agency ARPA order No.  1086. Dep.
  Defense  Contract No.   DAHC   15-68-C-0119.
  369 p.
Innes,  J.R.M., B.M. Ulland, M.G. Valeric, L.
  Petrucelli, L. Fishbein, E.R. Hart, A.J. Pallota,
  R.R. Bates,  H.L. Falk,  J.J. Gart, M. Klein, I.
  Mitchell,  and  J. Peters.  1969. Bioassay  of
  pesticides  and industrial  chemicals for
  tumorigenicity in mice:  a preliminary note.  J.
  Natl. Cancer Inst. 42:1101-1114.
Johnson, J.E. 1971. The public health implications
  of widespread use of the  phenoxy  herbicides and
  picloram. Bioscience 21:899-905.
Lawrence, J.N. 1964. Aquatic herbicide data. U.S.
  Dep. Agric., Agric. Handb.  231.
Leonard, O.A.  (Ed.) 1961. Tables on reaction of
  woody plants to herbicides. West. Weed Control
  Conf. Res. Prog. Rep., p. 27-37.
Leonard, O.A.,  and W.A. Harvey. 1965. Chemical
  control of woody plants. Calif. Agric. Exp. Stn.,
  Davis, Calif., Bull. 812.  26 p.
Mrak, E. 1969.  Report of the Secretary's Commis-
  sion on pesticides and their  relationship to en-
  vironmental  health.  U.S. Dep.  Health, Educ.
  and Welfare.  December.
Newman, A.S.,  and J.R. Thompson. 1950. Decom-
  position of 2,4-dichlorophenoxyacetic acid in soil
  and liquid media.  Soil  Sci. Soc. Am.  Proc.
  14:160-164.
Norris, L.A., and D.G. Moore. 1971. The entry and
  fate of forest chemicals  in streams. In Forest
  Land  Uses and  Stream Environment  Sym^
  posium Proc., p. 138-158. J.T. Krygier and J.D.
  Hall, eds. Sch.  For. and Dep. Fish, and Wildl.,
  Oreg. State Univ., Corvallis.
Oregon Extension Service.  1977. Oregon weed con-
  trol handbook.  158 p. Oreg. State Univ., Coop.
  Ext. Serv., Corvallis.
Palmer, J.S., and R.D. Radeleff.  1964. The tox-
  icological  effects of certain fungicides and her-
  bicides on sheep and cattle. Ann. N. Y. Acad. Sci.
  111:729-736.
Romancier, R.M.  1965.  2,4-D, 2,4,5-T, and related
  chemicals  for  woody plant control  in  the
  southeastern  United States.  Ga.  For. Res.
  Counc. Rep. No. 16,  46 p.
Rose, V.K.,  and T.A. Hymas.  1954. Summary of
  toxicological information on  2,4-D  and  2,4,5-T
  type herbicides and an evaluation of the hazards
  to livestock associated with their use. Am. J. Vet.
  Res. 15:622-629.
Rudolf, P.O., and R.F. Watt. 1956.  Chemical con-
  trol of brush and trees in the Lake States. U.S.
  Dep. Agric, For.  Serv. Lake States For. Exp.
  Stn., Stn. Pap.  No. 41. 58 p. St. Paul, Minn.
                                             XI.51

-------
Tucker, R.K., and D.G. Crabtree. 1970. Handbook
  of toxicity of pesticides to wildlife. U.S. Dep.
  Inter., Bur. Sport Fish, and Wildl., Res. Publ.
  84.
U.S. Department of Agriculture,  Forest  Service,
  1978. Vegetation management with herbicides.
  Final environ, impact statement. Pac Northwest
  Reg.  USDA-FS-R6-FES  (Adm) 75-18  (Rev.).
  Mar. 6,1978. 330 p. plus append. Portland, Oreg.
Verrett,  J.  1970. Testimony before the  United
  States Senate Committee on Commerce. Sub-
  Comm. on Energy, Water, Nat. Resour.  and En-
  viron. Apr. 15,  1970. Ser. 91-60, p. 190-203.
Weed Science Society of America. 1974. Herbicide
  handbook of  the  Weed Science  Society  of
  America. 3rd ed. 430 p. Champaign, 111.
                                 Hughes, J.S., and J.T. Davis. 1963. Variations in
                                   toxicity to bluegill sunfish of phenoxy herbicides.
                                   Weeds 11:50-53.
                                 Martin, H. (ed.) 1971. Pesticide Manual: Basic In-
                                   formation on the Chemicals used as Active Com-
                                   ponents of Pesticides.  2nd  ed.  British Crop
                                   Protect. Counc. p. 169.
                                 Pimentel, D. 1971.  Ecological effects of pesticides
                                   on non-target species. Exec. Off. Pres., Office
                                   Sci. Technol. U.S. Govt. Printing Off., Wash.,
                                   D.C. 220 p.
                                 U.S. Department of Agriculture,  Forest Service.
                                   1978.  Vegetation management with  herbicides.
                                   Final environ impact statement.  Pac. Northwest
                                   Reg. USDA-FS-R6-FES  (Adm)  75-18  (Rev.).
                                   March 6, 1978, Portland, Oreg.  330 p. plus ap-
                                   pend.
                                 Weed Science Society of America.  1974. Herbicide
                                   handbook of the Weed Sci. Soc. Am., 3rd ed. 430
                                   p. Champaign, 111.
Common name:
Chemical name:

Other Names:

Registered Use:
 Dichlorprop, 2,4-DP
 2-(2,4-dichlorophenoxy)
 propionic acid
 Weedone  2,4-DP, Weedone
 170, Envert 170
 Brush  control  on  non-
 agricultural lands


References
Amchem Products, Inc.  1972. Toxicity summary
  for Weedone Brush-Killer-170.  Data sheet.
  Ambler, Pa.
Anderson,  K.J.,  E.G. Leighty, and M.T.
  Takahashi. 1972. Evaluations of herbicides for
  possible mutagenic properties.  J.  Agric. Food
  Chem. 20(3):649-656.
Burger, K., C. MacRae, and M. Alexander. 1962.
  Decomposition of phenoxyalkyl carboxylic acids.
  Soil Sci. Soc. Am. Proc. 26(3):243-246.
Hiltibran, R.C.  1967. Effects of some herbicides on
  fertilized fish  eggs and fry. Trans. Am. Fish. Soc.
  96(4):414-416.
Hirsch,  P., and M. Alexander.  1960.  Microbial
  decomposition of  halogenated  propionic  and
  acetic acids. Can. J. Microbiol.  6:241-249.
Hughes, J.S., and J.T.  Davis. 1962. Toxicity of
  selected herbicides to bluegill sunfish.  Proc.
  Louisiana Acad.  Sci. 25:86-93.
Common name:
Chemical name:

Other names:
                                 Registered use:
2,4,5-T
(2,4,5-Trichlorophenoxy)
acetic acid
Esteron 245—PGBE ester;
Ded-weed—Isooctylester;
Brush/killer Lo Vol 4T—
Isooctylester;  Dinoxol—
Butoxyethanol ester.
2,4,5-T is registered for control
of  woody and  herbaceous
plants;  especially for brush
control,  selective   conifer
release,  and control of woody
plants  in  rangeland  and
pastures.
                                                   References
                                 Advisory Committee on 2,4,5-T. 1971. Report of the
                                   Advisory  Committee on  2,4,5-T  to  the Ad-
                                   ministrator  of  the  Environmental Protection
                                   Agency. Submitted May 7, 1971.
                                 Abesson, N.B., W.E. Yates, and S.E. Wilce. 1970.
                                   Key to safe and effective aerial application: con-
                                   trolling  spray   atomization.  Agrichem.  Age
                                   13(12): 10,12,13,16,17.
                                             XI.52

-------
Allen, J.R., J.P. Van Miller, and D.H. Norback.
  1975.  Tissue  distribution,  excretion,  and
  biological effects of [14 ]  tetrachlorodibenzo-p-
  dioxin in rates.  Food Cosmet. Toxicol. 13:501-
  505.
Allen, J.R., D.A. Barsotti, and  J.P. Van Miller.
  1977.  Reproductive dysfunction  in  non-human
  primates exposed to dioxins. Presented at 16th
  Annu. Meet.,  Soc. Toxicol.,  Toronto, 1977.
  Abstract in.
Anderson,  K.J.,  E.G. Leighty, and  M.T.
  Takahashi. 1972. Evaluations  of herbicides for
  possible  mutagenic properties. J.  Agric. Food
  Chem. 20(3):649-656.
Arend, J.L., and E.I. Roe. 1961. Releasing conifers
  in the Lake States with chemicals.  U.S. Dep.
  Agric., Agric. Handb. 185. 22 p.
Bache, C.A., D.D. Hardie, R.F. Holland,  and D.J.
  Lisk.  1964. Absence of phenoxy acid herbicide
  residues in the milk of dairy cows at high feeding
  levels. J. Dairy Sci. 47:298-299.
Crosby, D.G., and A.S. Wong. 1977. Environmen-
  tal degradation of 2,3,7,8,-tetrachlorodibenzo-p-
  dioxin (TCDD). Science 195:1337-1338.
Drill, V.A., and T. Hiratzka. 1953. Toxicity of 2,4-
  D and 2,4,5-T acid: a report on their acute  and
  chronic toxicity in  dogs. Arch.  Indust. Hyg.
  Occup. Med. 7:61-67.
Gratkowski, H. 1961. Use of herbicides on forest
  lands in southwestern Oregon.  U.S. Dep. Agric.
  For. Serv. Pac. Northwest For. and Range Exp.
  Stn., Res. Note 217. 18 p. Portland,  Oreg.
Gratkowski, H., and  R.E. Stewart.  1973.  Aerial
  spray  adjuvants  for herbicidal drift  control.
  USDA For. Serv. Gen. Tech. Rep. PNW-3. 18 p.
  (illus.) Pac. Northwest For. and  Range Exp.
  Stn., Portland, Oreg.
House, W.B., L.H. Goodson, H.M.  Gadberry,  and
  K.W. Docktur. 1967. Assessment of ecological ef-
  fects of extensive or repeated use of herbicides.
  Final Rep.,  Midwest Res. Inst. Proj. 3103-B.
  Adv. Res. Proj. Agency ARPA  Order No. 1086.,
  Dep. Defense Contract No. DAHC 15-68-C-0119.
  369 p.
Hughes, J.S., and J.T. Davis.  1963. Variations in
  toxicity to bluegill sunfish of phenoxy herbicides.
  Weeds 11:50-53.
Lines, J.R.M., B.M.  Ulland, M.G. Valeric,  and
  others. 1969. Bioassay of pesticides  and  in-
  dustrial chemicals for tumorigenicity in mice: a
  preliminary note. J. Natl. Cancer Inst.  42:1101-
  1114.
 Johnson, J.E. 1971. The public health implications
   of widespread use of the phenoxy herbicides and
   picloram. Bioscience 21:899-905.
 Kenega, E.E. 1974. 2,4,5-T and derivatives: tox-
   icity  and stability in the aquatic environment.
   Down to Earth 30(3): 19-25.
 Leonard, O.A., and W.A. Harvey. 1965. Chemical
   control of woody plants.  Calif. Agric. Exp. Stn.
   Bull.  812. 26 p.  Davis, Calif.
 Mahle,  N.H.,  H.S. Higgins,  and M.E. Getzen-
   daner. 1977. Search for the presence of 2,3,7,8-
   tetrachlorodibenzo-p-dioxin   in  bovine   milk.
   Bull.  Environ. Contam. Toxicol. 18(2): 123-130.
 Mrak, E.M. 1969.  Report of the Secretary's Com-
   mission on  pesticides and their relationship to
   environmental health. U.S. Dep. Health, Educ.
   and Welfare. U.S. Gov. Print. Off., Washington,
   D.C.  677 p.
 Norris,  L.A.,  M.L.  Montgomery,  and  E.R.
   Johnson. 1977. The  persistence of 2,4,5-T in a
   Pacific Northwest forest. Weed Sci. 25(5):417-
   422.
 Norris, L.A., and D.G.  Moore. 1971. The entry and
   fate of forest chemicals in streams, p. 138-158. In
   Forest land uses  and stream  environment.
   Krygier, T.J., and J.D. Hall, eds., Symp. Proc.,
   Oreg. State Univ., Corvallis.
 Palmer, J.S.,  and  R.D. Radeleff. 1964. The tox-
   icological effects  of certain fungicides and her-
   bicides on sheep and cattle. Ann. N.Y. Acad. Sci.
   111:729-736.
 Rowe, V.K., and T.A.  Hymas. 1954.  Summary of
   toxicological information on 2,4-D and 2,4,5-T
   type herbicides and an evaluation of the hazards
   to livestock associated with their use. J. Am. Vet.
   Res. 15:622-629.
 Shadoff, L.A., R.A. Hummel, L. Lamparski, and
   J.H.  Davidson.   1977. A  search  for  2,3,7,8-
   tetrachlorodibenzo-p-dioxin (TCDD)  in  an en-
   vironment  exposed  annually  to 2,4,5-
   trichlorophenoxyacetic  acid ester (2,4,5-T) her-
   bicides.  Bull.  Environ.  Contam. Toxicol.
   18(4):478-485.
U.S.  Department of Agriculture, Forest Service.
   1978.  Vegetation  management with herbicides.
   final environ, impact statement, Pac.  Northwest
   Reg.  USDA-FS-R6-FES  (Adm)75-18(Revised).
  March 6, 1978,  Portland, Oreg.  330  p. plus
   append.
Weed Science  Society of America. 1974. Herbicide
  handbook  of the Weed Science  Society  of
  America. 3rd ed.  430 p. Champaign,  111.
                                             XI.53

-------
Common name:
Chemical name:

Other names:
Registered use:
Atrazine
2-chloro-4-ethylamino-6-
isopropylamino-s-triazine
AAtrex 80 W
Selective  control of broadleaf
and grassy  weeds  in conifer
reforestation where  it serves to
increase seedling survival ap-
preciably; also used  in forest
and Christmas tree  planta-
tions of Douglas-fir, grand fir,
noble fir, white fir, lodgepole
pine,  ponderosa   pine,  and
Scotch  pine.


References
Alabaster, J.S. 1969. Survival of fish in 164 her-
  bicides, insecticides, fungicides, wetting agents
  and miscellaneous substances. Int. Pestic. Contr.
  l(2):29-35.
Anderson, W.P. 1977. Weed science principles, p.
  244-247. West Publ. Co.: St. Paul, N.Y., Boston,
  Los Angeles, San Francisco.
Bickford, M.L., and R.K. Hermann.  1967. Her-
  bicide  aids  survival  of Douglas-fir seedlings
  planted on dry sites in Oregon; root wrapping has
  little  effect. Tree Planters' Notes 18(4):l-4.
Butler,  P.A.  1963. Commercial fisheries investiga-
  tions. In Pesticide wildlife studies. U.S. Fish and
  Wildlife Serv. Circ. 167, p. 11-24.
Esser, H.O., G. Dupuis, E. Ebert, G.J. Marco, and
  C. Vogel. 1975. S-Triazines. Vol. 1, p. 129-208. In
  Herbicides—chemistry, degradation, and mode
  of action. 2nd ed., [revised and expanded] P.C.
  Kearney, and D.D. Kaufman, eds., Marcel Dek-
  ker, N.Y.
Federal Water Pollution Control Administration.
  1968. Water quality criteria. Rep.  Natl. Tech.
  Adv.  Comm. to the Seer. Inter. Fed. Water Pol-
  lut. Contr. Admin., U.S. Dep.  Inter. 234 p.
Gratkowski, H. 1975. Silvicultural use of herbicides
  in  Pacific  Northwest forests. USD A For. Serv.
  Gen.  Tech. Rep. PNW-37. 44 p. Pac. Northwest
  For. and Range Exp. Stn., Portland, Oreg.
Jones, R.O. 1965. Tolerance of the fry of common
  warm-water fishes to some chemicals employed
  in  fish culture.  Proc.  16th Annu.  Conf.
  Southeast. Assoc. Game Fish Comm.,  1962. p.
  436-445.
Kearney, P.C.  1970. Summary and conclusion, p.
  391-399. In  Residue  Reviews,  Vol. 32. Single
  pesticide  volume:  the  triazine  herbicides.
  Springer-Verlag: N.Y., Heidelberg,  Berlin.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. U.S.
  Environ. Protect. Agency Rep. No. EPA-910/9-
  77-036. 224 p. EPA Reg. X, Seattle, Wash.
Palmer, J.S., and R.D. Radeleff. 1969.  The toxicity
  of some organic herbicides to cattle, sheep and
  chickens.  U.S. Dep.  Agric., Agric. Res.  Serv.
  Prod. Rep. No. 106. 26 p.
Pimentel, D. 1971. Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off. Sci.
  Technol., Washington, D.C. 220 p.
St. John, L.E.,  D.G. Wagner, andD.J. Lish. 1964.
  Fate of atrazine, kuron, silvex, and 2,4,5-T in the
  dairy cow. J. Dairy Sci. 47(11):1267-1270.
Tucker, R.K. and D.G. Crabtree.  1970. Handbook
  of toxicity of pesticides to wildlife. U.S.  Dep.
  Inter., Fish and Wildl. Serv., Bur.  Sport  Fish.
  and Wildl. Resour. Publ. No. 84. 131 p.
Walker, C.R. 1964.  Simazine and other s-triazine
  compounds as  aquatic  herbicides  in  the fish
  habitat. Weeds 12(2):134.139.
Weed Science Society of America. 1974. Herbicide
  handbook  of the Weed  Science  Society of
  America. 3rd ed. p. 29-35. Champaign, 111.
                                  Common name:
                                  Chemical name:

                                  Other names:
                                  Registered use:
                   Carbaryl
                   1-Naphthyl N-methyl
                   carbamate
                   Sevin, Sevin 4-Oil
                   Suppression of various insect
                   outbreaks including the gypsy
                   moth,  cankerworm, saddled
                   prominent  and  tent caterpil-
                   lar, and the spruce bud worm
                   (eastern and western).


                  References
                                  Anderson, E. J. 1964. The effects of Sevin on honey
                                    bees. Gleanings Bee Cult. 92(6) :358-364.
                                  Boschetti, N.M. 1966. Sevin residues in water and
                                    top soil following its use on a watershed area. p.
                                    52-62. In Report of the surveillance program con-
                                    ducted in connection with an application of car-
                                    baryl  (Sevin) for the  control of gypsy moth on
                                              XI.54

-------
  Cape Cod, Massachusetts. Mass. Pestic. Board,
  Publ. 547. 75 p.
Fairchild, H.E.  1970.  Significant  information on
  use of Sevin-4-Oil for insect control. Union Car-
  bide Corp. [Undated folder of text and various
  reports.]
Felley,  D.R.  1970. The effect  of Sevin  as a
  watershed pollutant. Ph.D. diss., SUNY Coll.
  Environ. For., Syracuse Univ., N.Y.  97 p.
Karinen, J.F., J.G. Lamberton, N.E. Stewart, and
  L.C. Terriere. 1967. Persistence of carbaryl in the
  marine  estuarine environment.  Chemical and
  biological  stability  in aquarium systems.  J.
  Agric. Food Chem. 15(1): 148-156.
Macek, K.J., and  W.A. McAllister. 1970. Insec-
  ticide susceptibility of some common fish family
  representatives. Trans. Am. Fish. Soc. 99:20-27.
Metcalf, R.L., W.P. Flint, and C.L. Metcalf. 1962.
  Destructive and useful insects. 1087 p. McGraw
  Hill, N.Y.
Muncy, R.J., and A.D. Oliver.  1963. Toxicityoften
  insecticides to the red crayfish, Procambarus
  clarki (Girard).  Trans. Am. Fish. Soc. 92:428-
  431.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection  of water quality. U.S.
  Environ. Protect. Agency  Rep. No. EPA 910/9-
  77-036.  224 p. EPA Reg. X, Seattle,  Wash.
Pimentel, D. 1971.  Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off.  Sci
  Technol., Washington, D.C. 220 p.
Sanders, H.O., and O.B. Cope. 1966. Toxicities of
  several  pesticides to two species of cladocerans.
  Trans. Am. Fish. Soc. 95:165-169.
Sanders, H.O., and O.B. Cope. 1968. The relative
  toxicities of several pesticides to naiads of three
  species  of stoneflies.  Limnol.   and  Oceanogr.
  13:112-117.
Stewart, N.E., R.E. Millemann, and W.P. Breese.
  1967. Acute toxicity of the insecticide Sevin and
  its hydrolytic product 1-naphthol to some marine
  organisms. Trans. Am. Fish. Soc. 96:25-30.
Thomson, W.T. 1977. Agricultural  chemicals book
  I: insecticides. Thomson Publ., Fresno, Calif.
Tucker, R.K., and D.G. Crabtree. 1970.  Handbook
  of toxicity of pesticides to wildlife.  U.S. Dep.
  Inter. Fish and Wildl. Serv., Bur. Sport Fish.
  and Wildl. Res. Publ. No. 84. 131 p.
Union Carbide Corporation.  1968. Technical infor-
  mation on Sevin carbaryl insecticide. Union Car-
  bide Corp. ICG-0449A Bookl. 56 p.
 Union Carbide Corporation. 1970. Facts on Sevin
   carbaryl insecticide. Union Carbide Corp. Publ.
   F-43382. 28 p.
 U.S.  Department of Agriculture,  Forest Service.
   1977.  Final  environmental  statement,
   cooperative spruce budworm suppression pro-
   ject—Maine.
 Weiden, M.H.J., andH.H. Moorefield. 1964. Insec-
   ticidal  activity  of the commercial  and  ex-
   perimental  carbamates. World  Review.  Pest
   Contr. 3:102-107.
Common name:
Chemical name:

Other names:

Registered use:
 Chlorpyrifos
 0,0-diethyl-0-(3,5,6-trichloro-
 2-pyridyl) phosphorothioate
 Dursban,   DOWCO  179,
 LORSBAN
 Insect control.


References
Dow Chemical, U.S.A. 1974. Dursban insecticide
  technical information. Brochure. 14 p.
Evans, E.S., J.H. Nelson, N.E. Pennington,  and
  W.W. Young. 1975. Lavicidal effectiveness  of a
  controlled-release formulation of chlorphyrifos in
  a  woodland pool  habitat. Mosquito  News
  35(3):343-350.
McMartin, K.D. 1977. Control of cattle lice with a
  low volume pour-on formulation of chlorpyrifos.
  Down to Earth 33(1): 18-19.
Oberheu, J.C., R.O. Soule, and M.A. Wolf. 1970.
  The correlation of cholinesterase  levels in  test
  animals and exposure levels resulting from ther-
  mal fog and aerial spray applications of Dursban
  insecticide. Down to Earth 26(1):1216.
Thomson, W.T. 1977. Agricultural chemicals book
  I: insecticides.  236 p. Thomson Publ., Fresno,
  Calif.
Walker, A.I. 1975. Field tests of Dursban M insec-
  ticide against gypsy moth larvae. Down to Earth
  31(1)26-28.
Walsted,  J.D., and J.C.  Nord. 1975.  Applied
  aspects  of pales weevil control. Down to Earth
                                              XI.55

-------
Common name:
Chemical name:
Other names:

Registered use:
Dalapon
2,2-dichloropropionic acid
Dowpon, Dowpon C, Dowpon
M
A moderately  specific  grass
herbicide commonly used as a
pre-plant treatment on conifer
planting sites.


References
Alabaster,  J.S. 1969.  Survival of fish in  164 her-
  bicides, insecticides, fungicides,  wetting agents
  and miscellaneous substances. Int. Pest Control
  ll(2):29-35.
Bohmont,  B.L.  1967. Toxicity of herbicides to
  livestock, fish, honey bees and wildlife. Proc.
  West. Weed Contr.  Conf. 21:25-27.
Cope, O.B. 1965.  Sport fisheries  investigations.
  p.51-63.  In  Effects of pesticides  on fish and
  wildlife,  1964 research findings of the Fish and
  Wildlife Service. U.S. Fish and Wildl. Serv. Circ.
  226.
Frank, P.A., R.J. Demint, and  R.D. Comes. 1970.
  Herbicides in irrigation water following  canal-
  bank treatment for  weed control.  Weed  Sci.
  18:687-692.
Holstun, J.R., and J.W.E. Loomis. 1956. Leaching
  and  decomposition  of sodium  2,2-
  dichloropropionate  in several Iowa soils. Weeds
  4:202-207.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. U.S.
  Environ. Protect. Agency, Rep. No. EPA 910/9-
  77-036. 224 p. EPA Reg. X, Seattle, Wash.
Surber, E. W., and Q.H. Pickering. 1962. Acute tox-
  icity of endothal, diquat, hyamine, dalapon, and
  silvex to fish.  U.S.  Dep. Inter., Fish and Wildl.
  Serv., Prog. Fish-Cult. 24:161-171.
Warren, L.E. 1964. The fate of dalapon in the soil.
  Pap. presented at the Wash. State Weed Conf.,
  Yakima.  Nov. 2-3, 1964.
Warren, L.E. 1967. Residues  of herbicides and im-
  pact on uses by  livestock, p. 227-242. In Sym-
  posium proceedings, herbicides and vegetation
  management in  forests, ranges, and non-crop
  lands. Oreg. State Univ., Corvallis.
Weed Science Society  of America. 1974. Herbicide
  handbook  of  the  Weed  Science  Society  of
  America. 3rd ed. 430 p. Champaign, 111.
Common name:
Chemical name:
Other names:

Registered use:
                  Dicamba
                  3,6-dichloro-o-anisic acid; also
                  2-methoxy-3,6-dichloroben-
                  zoic acid
                  Banvel, Banvel Brush Killer,
                  Banvel 5G Granules
                  Brush  control  on  non-
                  croplands,  including  forest
                  lands.

                  References

Andus, L.J. 1964. The physiology and biochemistry
  of herbicides, p. 104-206. Acad. Press.
Boppart, E.A. 1966. Chemical leaching and bioas-
  say of Banvel D granules. Biol. Res. Sect., Her-
  bic. Rep. 47-H-66. Velsicol Chem. Corp.
Cain, P.S. 1966.  An investigation of the herbicidal
  activity of 2-methoxy-3,6-dichlorobenzoic  acid.
  Ph.D.  diss., Agron.  Dep.,  Univ. 111., Urbana.
  131 p.
Friesen, H.A. 1965. The movement and persistence
  of dicamba in soil. Weeds 13:30-33.
Harris,  C.I.  1963.  Movement  of  dicamba  and
  diphenamid in soils.  Weeds 12:112-115.
Markland, F.E.  1968. Evaluation of encapsulated
  granules of Banvel D for leaching characteristics.
  Velsicol Chem. Corp.  Biol. Res. Sec., Herbic.
  Rep. 31-H-68.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. U.S.
  Environ.  Prot. Agency Rep. No. EPA 910/9-77-
  036. 224 p. EPA Reg. X, Seattle, Wash.
Pimentel, D. 1971. Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off. Sci.
  Technol., Washington, D.C. 220  p.
Velsicol  Chemical  Corporation.  1971. Banvel
  federal label registrations. Velsicol Chem. Corp.
  Bull. 07-001-501. 15 p.
Velsicol Chemical  Corporation.  1971. Banvel her-
  bicides for brush  and broadleaf weed control.
  Velsicol Chem. Corp., unnumbered pamphlet.
Velsicol Chemical  Corporation.  1971. Banvel her-
  bicides general bulletin. Velsicol Chem. Corp.
  Bull. 07-151-501. 4 p.
Weber,  J.B., and  J.A.  Best. 1971. Activity and
  movement  of  13 soil-applied herbicides  as in-
  fluenced by soil reaction. South.  Weed Sci. Soc.
  Proc.  24:403-413.
Weed Science Society of America. 1974. Herbicide
  handbook  of  the Weed  Science  Society of
  America. 3rd ed. p. 139-141. Champaign, 111.
                                              XI.56

-------
Common name:
Chemical name:
Other names:
Registered use:
                   Diflubenzuron
                   N(((4-Chorophenyl)
                   amino)carbonyl)-2,6-di
                   fluorobenzam ide
                   Dimilin, Difluron, TH-6040
                   Control of the gypsy moth; also
                   used in aquatic ecosystems.


                  References

 Schoeltger, R.A. 1976. Annual progress report, fish-
   pesticide research laboratory. U.S. Dep. Inter.,
   Fish and Wildl. Serv., Columbia, Mo.
 Thompson-Hayward  Chemical Company.  1977.
   Environmental  safety  and  interactions  of
   Dimilin. [Typed Rep.] 31 p.
 Thomson, W.T. 1977. Agricultural chemicals book
   I: insecticides, acaricides and oricides. 236 p.
   Thomson Publ., Fresno, Calif.
Common name:
Chemical name:
Other names:
Registered use:
                  Ethylene Dibromide
                  1-2 dibromoethane
                  EDP,  Fumo-gas, E-D-Bee,
                  Bromo-fume, Soil-Fume, Dow-
                  fume, Urifume
                  Forest  insecticide  against
                  Douglas-fir beetle, Jeffrey pine
                  beetle, mountain  pine beetle,
                  roundheaded  pin  beetle,
                  spruce  beetle,  California
                  flatheaded  bores, Monterey
                  pine ips, fir engraver beetle,
                  and western pine beetle.


                  References

Henderson, C. 1966. Special report, pesticide sur-
  veillance program, Teton bark beetle. Cont. Proj.
  Div. Fish Serv., U.S. Dep. Inter., Bur. Sport Fish
  and Wildl., Fort Collins,  Colo.
Hoyle, H.R. 1951. Hazard to men engaged in spray-
  ing spruce trees with an ethylene dibromide
  emulsion.  T3.5-6-8. Biochem. Res.  Lab.  Rep.
  Dow Chem. Co., Denver.  [Unpubl. Rep.]
Pillmore,  R.E.  1966.  Letter  to Chief, Sect, of
  Chem., Physiol., and Pestic-Wildl.  Stud., U.S.
  Dep. Inter., Fish and Wildl. Serv. [June 6,1966.]
Rowe, V.K., H.C. Spencer, D.D. McCallister, and
  others.  1952. Toxicity of ethylene  dibromide
  determined on experimental animals. Arch. Ind.
  Hyg. and Occup. Med. 6:158-173.
Tracy,  R.H. 1970. Letter to Reg. For., U.S. Dep.
  Agric., For. Serv. [Nov. 10, 1970.]
U.S. Department of Health,  Education, and
  Welfare. 1963. Studies on the effect of forest in-
  sect control  with ethylene dibromide on water
  quality. PR-9, USPHS, HEW, Denver.
White,  V.L.  1972. Letter to Stanley I. Undi, U.S.
  Dep. Agric.,  For. Serv. from Great Lakes Chem.
  Corp. [Feb. 21,  1972.]
                                                  Common name:
                                                  Chemical name:
                                                  Other names:
                                                  Registered use:
                  Fenitrothion
                  0,0-dimethyl-0-(3 methyl-4-
                  nitrophenyl) phosphorthioate;
                  also  0,0-dimethyl 0-(4-nitro-
                  m-tolyl) phosphorothioate (1)
                  Sumithion, Sumitomo
                  Control  of  hepidoptera,
                  diptera,     orthoptera,
                  hemiptera, and  coleoptera  in
                  field  crops and on fruits and
                  vegetables;  forest protection
                  through control  of Japanese
                  pine  sawyer,  pine caterpillar,
                  hemlocklooper,  spruce
                  budworm,  bark   beetle,  and
                  weevil; control of insects af-
                  fecting public health such  as
                  mosquitos, flies,  bedbugs, and
                  cockroaches;  and  control  of
                  locust and grasshopper.

                 References
                                                  Associate Committee of Scientific Criteria for En-
                                                    vironmental Quality. 1975. Fenitrothion: the ef-
                                                    fects of its use on environmental quality and its
                                                    chemistry. Natl. Res. Counc. Can. NRCC No.
                                                    14104. 162 p.
                                                  Benes, V., and R. Sram. 1969. Mutagenic activity
                                                    of some pesticides in Drosophila melanogaster.
                                                    Ind. Med. 38:50-52.
                                                  Hazelton  Laboratory.  1974. Toxicology studies,
                                                    part III. Three-generation study in rats. In Tox-
                                                    icology  studies of Sumithion.  Sumitomo Chem.
                                                    Co. Ltd.,  Osaka, Japan.
                                            XI.57

-------
Industrial  Bio-Test  Laboratories.  1972.
  Teratogenic study with Sumithion in albino rab-
  bits. Ind. Bio-Test Labs. [Unpubl. rep.]
Industrial Bio-Test Laboratories. 1974. Ninety-day
  subacute one  year  and two  year oral feeding
  study with Sumithion in beagle dogs. Ind. Bio-
  Test Labs. [Unpubl. rep.]
Kadota, T. 1974. Two year chronic feeding toxicity
  of Sumithion on rats. Sumitomo Chem. Co. f Un-
  publ. rep.] Osaka, Japan.
Kadota, T., and J. Miyamoto. 1975. Acute toxicity
  of Sumithion  lOO^r w/v EC in mice  and rats.
  [Unpubl.]
Miyamoto, J. 1972.  Toxicological  studies with
  Sumithion, acute/rats, mice. Sumitomo Chem.
  Co., [Unpubl.  rep.]  Osaka, Japan.
Miyamoto, J. 1974. Decomposition and leaching of
  Sumithion in  four  different  soils  under
  laboratory  conditions. Sumitomo Chem.  Co.,
  [Unpublished rep.] Osaka, Japan.
Miyamoto, J. 1974.  Stability in water.  Sumitomo
  Chem. Co., [Unpubl. rep.] Osaka, Japan.
Namba, N., T. Twamoto, and T. Saboh. 1966. Oral
  toxicity and metabolism of Sumithion on cattle,
  sheep and pigs. Hokkaido Natl. Agric. Exp. Stn.
  Res. Bull. 89:82.
Sumitomo Chemical Company.  1972. Toxicology
  studies, part IV:  delayed  neuroloxicity  of
  Sumithion. Osaka, Japan.
Sumitomo Chemical Company.  1975. Sumithion
  technical manual. Osaka, Japan.
Yasuno, M., S. Hirakoso, M. Sasa, and M. Uchida.
  1965. Inactivation of some organophosphorous
  insecticides by  bacteria in  polluted  water.
  Japanese J. Exp.  Med. 35:545-563.
Zitko,  V.,  and  T.D.  Cunningham.  1974.
  Fenitrothion derivative and isomers: hydrolysis,
  adsorption and biodegradation. Fish. Res. Board
  of Can. Tech. Rep. No. 458.
Common name:
Chemical name:

Registered use:
Malathion
(0,0-dimethyl  dithiophospate
of diethylmercaptosuccinate)
Control of a number of forest
insects  including  defoliators
and sucking insects of conifers
and hardwoods.
                  References

Eaton, J.G. 1970. Chronic malathion toxicity to the
  bluegill,  Lepomis macrochirus  Rafinesque.
  Water Res. 4:673.
Environmental  Protection  Agency.  1975. Initial
  scientific and minieconomic review of malathion.
  EPA 540/1-75-005.  Off. Pestic. Programs. 251 p.
 Golz, H.H. 1959. Controlled human  exposures to
  malathion aerosols. Am. Med. Assoc. Arch. Ind.
  Health 191516-523.
Konrad,  J.G., C. Chesters, and D.E. Armstrong.
  1969.  Soil  degradation of  malathion,  a
  phosphorodithioate insecticide.  Soil Sci.  Soc.
  Am.  Proc. 33(2):259-262.
Macek,  K.J., and W.A.  McAllister.  1970. Insec-
  ticide susceptibility of some common fish family
  representatives. Trans. Am. Fish. Soc. 99:20-27.
Matsumura,  Fumio. 1975. Toxicology of insec-
  ticides. Plenum Press.  N.Y.
Mount, D.I., and C.E. Stephen. 1967. A method for
  estimating acceptable toxicant limits for fish —
  malathion  and butoxyethanol  ester of 2,4-D.
  Trans. Am. Fish. Soc.  96:185-193.
Muncy, R.J., and A.D. Oliver. 1963. Toxicity often
  insecticides to  the red crayfish, Procambarus
  clarki (Girord). Trans. Am. Fish.  Soc. 92:428-
  431.
Newton, M., and J.A. Norgren. 1977.  Silvicultural
  chemicals and protection of water quality. EPA
  910/9-77-036.  224 p.
Pimentel, D. 1971. Ecological effects  of pesticides
  on non-target species. Exec. Off. Pres.,  Off. Sci
  Technol., Washington,  B.C. 220 p.
Rider, J.A. 1958. Studies on the effects of EPN and
  malathion   in   combination   on   blood
  cholinesterose of man. Prep. Natl. Agric. Chem.
  Assoc. 5 p.
Roberts, J.E. and others. 1962. Presistence of insec-
  ticides in soil and their effects on cotton in
  Georgia. Abstr. Rev. Appl. Ent., Vol. 50, Ser. A,
  Part II. 567 p.
Sanders, H.O. 1970.  Toxicities of  some herbicides
  to six species of freshwater crustaceans. J. Water
  Pollut. Contr. Fed. 42:1544-1550.
Sanders, H.O.,  and O.B. Cope. 1966. Toxicities of
  several pesticides to two  species of cladocerans.
  Trans. Am. Fish. Soc.  95:165-169.
Sanders, H.O.,  and O.B. Cope. 1968. Toxicity of
  several pesticides to naiads of  three species of
  stoneflies. Limnol. and Oceanog. 13:112-117.
                                             XI.58

-------
Walter,  W.W.,  and B.J.  Stojanovic.  1973.
  Microbial vs. chemical degradation of malathion
  in soil. J. Environ.  Qual. 2(2):229-232.
Common name:
Chemical name:
Other names:
Registered use:
MSMA
Monosodium  methane  ar-
sonate or  Monosodium  acid
methan arsonate
Silvisar  550  Tree  Killer,
Vichem   120  Arsonate
Silvicide, Glowon Tree Killer
For post-emergent weed con-
trol and as a silvicide for con-
trol  of undersirable  conifers
and big leaf maple.
                  References

Bollen,  W. B., L. A. Norris, and K. L. Stowers.
  1974.  Effect of cacodylic acid and MSMA on
  microbes  in forest floor  and soil. Weed  Sci.
  22:557-562.
Dickens, R., and A. E. Hiltbold. 1967. Movement
  and persistence of methanearsonates in soil.
  Weeds 15:299-304.
Duble, R. L., E. C. Hold, and G. G. McBee. 1969.
  Translocation  and breakdown  of DSMA in
  coastal bermuda grass. J. Agric. Food Chem.
  17:1247-1250.
Ehman, P. J. 1965. The effect of arsenical buildup
  in the soil on subsequent growth and residue con-
  tent of crops. Southern Weed Control Conf. Proc.
  18:685-687.
Frost,  D. V.  1970.  Tolerances for  arsenic  and
  selenium:  A  psychodynamic  problem.  World
  Rev. of Pest Contr. Spring 1970, 9(l):6-27.
Johnson, L.  R., and A. E. Hiltbold. 1969. Arsenic
  content of  soil and  crops  following  use of
  methane arsonate herbicides. Soil Sci. Soc. Am.
  Proc.  33:279-282.
Morton,  H.  L.,   J. O. Moffett, and R. H. Mac-
  Donald. 1972. Toxicity of herbicides to  newly
  emerged  honey  bees.   Environ.  Entomol.
  1(1): 102-104.
Mrak, E. M. 1969. Report of the Secretary's Com-
  mission on pesticides and their relationship to
  environmental health. U.S. Dept. Health, Educ.
  and Welfare. U.S. Gov. Print. Off., Wash, D.C.
  677 p.
Newton,  M., and H.  A. Holt. 1968. Hatchet-
  injection of phenoxys, picloram, and arsenicals
  for control of some hardwoods and conifers. Proc.
  Western Soc.  Weed Sci. 22:20-21.
Newton,  M., and L. A. Norris. 1976.  Evaluating
  short- and long-term effects of herbicides on non-
  target  forest  and range biota. Symposium on
  Biological Evaluation of Environmental Impact,
  Counc. for Environ.  Qual.  Annu. Meet.  Ecol.
  Soc.  Am.  and AIBS. New Orleans.  [Published
  also in Down  to Earth 32(3): 18-26].
Norris, L. A. 1974.  The behavior and  impact of
  organic arsenical herbicides in the forest:  Final
  report on cooperative  studies. USD A  Forest Ser-
  vice, Pac. Northwest  For. and Range Exp. Stn.
  98 p.
Wagner, S. L., and P. H. Weswig. 1974. Arsenic in
  blood and urine of forest workers as indices of ex-
  posure to cacodylic acid. Arch. Environ. Health
  28(2):77-79.
Woolson, E. A.  (Ed.). 1975. Arsenical  Pesticides.
  ACS Symposium Series  7,  Am.  Chem.  Soc.,
  Washington, D.C. 176 p.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
  1971. Correlation between available soil arsenic,
  estimated by  6 methods, and response  of corn
  (Zea  Mays  L.).  Soil Sci. Soc.  Am. proc.
  35(1):101-105.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
  1971. The chemistry and phytotoxicity of arsenic
  in soils. I. Contaminated field soils. Soil Sci. Soc.
  Am. Proc. 35:938-943.
Woolson, E. A., J. H. Axley, and P. C. Kearney.
  1973. The chemistry and phytotoxity of arsenic
  in soils. II. Effects of  time and phosphorus. Soil
  Sci. Soc. Am. Proc. 37:254-259.
                                 Common name:
                                 Chemical name:

                                 Registered use:
                  Orthene (acephate)
                  (O,S,Dimethyl acetylphos-
                  phoramidothioate)
                  Control of gypsy moth.
                                             XI.59

-------
                  References

Bossor, J., and T. F. O'Connor. 1975. Impact on
  aquatic ecosystem. In  Environmental  impact
  study   of  aerially  applied orthene  (0,S-
  dimethylacetyl-phosphoramidothiote)   on  a
  forest and aquatic system. Rep. No. 174, p. 29-
  47. Lake Ont. Environ. Lab., State Univ. Coll.,
  Oswego, N.Y.
Chevron  Chemical Corporation. 1972. Technical
  information experimental data sheet. October. 2
  p. Chevron Chem. Co.
Chevron  Chemical Corporation. 1976. Technical
  information experimental data sheet. February.
  4 p. Chevron Chem. Co.
Schoeltger,  R. A. 1976. Annual progress  report
  1975-76. Fish-Pestic. Res. Lab., U.S. Dep. Inter.,
  Fish and Wildl. Serv., Columbia, Mo.
Thomson,  W.  T. 1975. Agricultural chemicals.
  Thomson Publ., Indianapolis.
Witherspoon, B., Jr.  1977. Letter to Superv., Spec.
  Prod. Dev., Chevron Chem. Co.
Common name:
Chemical name:

Other names:
Registered use:
                  Picloram
                  4-amino-3,5,6-trichloro-
                  picolinic acid
                  Tordon, ATCP
                  Control of annual  and  deep
                  rooted perennial weeds in non-
                  cropland.


                  References

Beatty, S. 1962. Results of dietary feeding studies
  of 4-amino-3,5,6-trichloropicolinic acid in  rats.
  Biochem. Res. Lab., Unpubl. Rep. 35. 12-38212-
  2. Nov.  15. Dow Chem. Co., Midland, Mich.
Buttery, R. F., T. R. Plumb, and N. D.  Meyers.
  1972. Picloram — background information state-
  ment. 43 p.
(ioring,  C. A. I., C. R. Youngson, and J. W.
  Hamaker. 1965. Tordon herbicide .  .  . disap-
  pearance from soils. Down to Earth 20:3-5.
Green, C. R. 1970. Effect of picloram and phenoxy
  herbicides in small chaparral watersheds. West.
  Soc. Weed Sci., Res.  Prog. Rep., Sacramento,
  Calif, p. 24-25.
Grover, R. 1967. Studies on the degradation of 4-
  amino-3,5,6-trichloropicolinic acid in soil. Weed
  Res. 7:61-67.
Hamaker, J. W., H. H.  Johnston, T. R. Martin,
  and C. T.  Redemann. 1963.  A picolinic acid
  derivative: A  plant  growth regulator. Science
  141:363.
Hardy, J. L. 1966. Effect of Tordon herbicides on
  aquatic chain  organisms. Down to Earth 22:11-
  13.
Jackson, J. B. 1965. Toxicological studies on a new
  herbicide  in sheep and cattle.  Am J. Vet. Res.
  27:821.
Kenaga,  E. E. 1969. Tordon herbicides — evalua-
  tion of safety  to fish and birds. Down to Earth
  25:5-9.
Lynn, G. E. 1965. A review of toxicological infor-
  mation on Tordon herbicides. Down to  Earth
  20:6-8.
McCollister, D.  D., and  M. L. Lang.  1969. Tox-
  icology  of picloram  and  safety evaluation  of
  Tordon herbicides. Down to Earth 25:5-10.
Norris, L. A. 1968. Degradation of herbicides in the
  forest floor. In  Tree growth and forest soils. C. T.,
  Youngberg,  and  C. B. Darey,  eds., Proc. 3rd
  North  Am. For. Soils Conf., Oreg. State Univ.
  Press, Corvallis.
Olson, K. 1963. Toxicological properties of Tordon
  22K (M-2477). Dow Chem. Co.,  Biochem. Res.
  Lab., Midland, Mich. Toxicol. Ref. 2 MO-2477-
  1.
Thompson, D. J., J. L. Emerson, R. J. Strenring,
  and others. 1972. Teratology and  post-noted
  studies on 4-amino-3,5,6-trichloropicolinic acid
  (picloram)  in  the rat. Food Cosmet. Toxicol.
  10:797-803.
Tucker, R. H., and D. G. Crabtree.  1970. Hand-
  book of toxicity of pesticides  to wildlife. Bur.
  Sport Fish and Wildl., Fish and Wildl.  Serv.,
  U.S. Dep. Inter. Res. Publ. No. 84 [Natl. Tech.
  Info. Serv. No. PB 198 815].
U. S. Department of Agriculture.  1969. The tox-
  icity of some organic herbicides to cattle, sheep
  and chickens.  Prod. Res.  Rep.  No. 106:22.
Weed Science Society of America. 1974. Herbicide
  handbook  of  the Weed Science  Society  of
  America. 3rd ed. p. 302-306. Champaign, HI.
Youngson, C. R., and R. W. Meikle. 1972. Residues
  of picloram acquired by  a mosquitofish, Gam-
  busia sp., from treated water.  Dow Chem. Co.,
  Walnut Creek, Calif. Rep. GH-1210.
                                              XI.60

-------
Common name:    Silvex-fenoprop
Chemical name:    2-(2,4,5-trichlorophenoxy)
                   propionic acid
Other names:      Kuron, Weedone
Registered use:     Control of woody plants, trees,
                   and shrubs; specific brush con-
                   trol in forest site preparation
                   and release; aquatic herbicide.


                  References

Anderson, W.P. 1977. Weed science principles, p.
  220-228. West Publ. Co.: St. Paul, N.Y., Boston,
  Los Angeles, San Francisco.
Bond, C.E., R.H. Lewis, and J.L. Fryer. 1960. Tox-
  icity  of various herbicidal materials to fishes.
  Robert A. Taft Sanit. Eng. Center,  Tech. Rep.
  W60-3:96-101.
Environmental Protection Agency. 1974. Herbicide
  report: chemistry and analysis, environmental
  effects, agricultural and other applied uses. Sci.
  Adv.  Board.  195 p.
Hughes, J.S.,  and J.T. Davis.  1964. Effects  of
  selected  herbicides  on bluegill sunfish.  Proc.
  Southeast Assoc.  Game Fish Comm. 18:480-482.
Kearney, P.C.,  and D.D. Kaufman.  1971. Her-
  bicides—chemistry, degradation and mode of ac-
  tion.  Vol. 1, p. 1-101. Marcel Dekker. N.Y.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. EPA
  910/9-77-036.
Pimentel, D. 1971.  Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off. Sci.
  and Technol., Washington, B.C. 220 p.
Sanders, Herman O. 1970. Toxicities of some her-
  bicides to six species of freshwater crustaceans.
  J. Water Pollut. Contr. Fed.  42:1544-1550.
Surber,  E.W., and Q.H. Pickering. 1962. Acute tox-
  icity of endothal, diquat, hyamine, dalapon, and
  silvex to fish. Prog. Fish. Cult. 24:164-171.
Weed Science Society of America.  1974. Herbicide
  handbook  of the  Weed  Science  Society  of
  America. 3rd ed.  Champaign, 111.
Common name:
Chemical name:
Simazine
(2-chloro-4,6 bis(ethylcunino)-
s-triazine)
Other names:      Princep SOW
  Registered use:   Weed  control  in  Christmas
                   tree plantations.


                  References

Anderson, W.P. 1977. Weed science principles, p.
  244-247. West Publ. Co.: St. Paul, N.Y., Boston,
  Los Angeles, San Francisco.
Bond, C.B., R.H. Lewis, and J.L. Fryer. 1959. Tox-
  icity of various herbicidal materials to fishes. In
  Biological problems in  water pollution.  Trans.
  1959 Sem., p. 96-101. U.S. Dep. Health,  Educ.,
  and Welfare.
Bond, C.B., R.H. Lewis, and J.L. Fryer. 1960. Tox-
  icity of various herbicidal materials to  fishes.
  Robert A. Taft Sanit. Eng. Center Tech. Rep.
  W60-3:96-101.
Burnside, B.C., E.L. Schmidt, and R. Behrens.
  1961.  Bissipation  of  simazine from the soils.
  Weeds 9(3)477-484.
Cope, O.B.  1964.  Sport fishery investigations. In
  The effects of pesticides on fish and wildlife. U.S.
  Bep. Inter., Circ. 226, p. 51-63.
Geigy Agricultural Chemicals.  1970. Princep her-
  bicide. Geigy Chem. Corp.  Tech. Bull., 8  p.
  Ardsley, N.Y.
Jordan, L.S., W.J. Farmer, J.R. Goodin, and B.E.
  Bay. 1970. Nonbiological detoxication of the s-
  triazine herbicides. Residue Rev. 32:267-286.
Kearney, P.C.,  and B.B.  Kaufman. 1971. Her-
  bicides—chemistry, degradation and mode of ac-
  tion. Vol. 1, p. 129-191. Marcel Bekker, N.Y. and
  Basel.
Klingman,  G.C. 1961. Weed control: as a science.
  421 p. John Wiley & Sons, N.Y.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. EPA
  910/9-77-036.
Pimentel, B. 1971. Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off. Sci.
  and Technol., Washington, B.C.
Ragab,  M.T.H.,  and  J.P.  McCollum.   1961.
  Begradation of  C14-labeled simazine by  plants
  and soil microorganisms. Weeds 9(l):72-84.
H.O. Sanders. 1970. Toxicities  of some herbicides
  to six species of freshwater crustaceans. J. Water
  Pollut. Contr. Fed. 42:1544-1550.
Talbert, R.B., and O.K. Fletchall. 1964. Inactiva-
  tion of simazine and atrazine in the field.  Weeds
  12:33-37.
                                              XI.61

-------
Walker, C.R. 1964. Simazine and other s-triazine
  compounds  as  aquatic herbicides in fish
  habitats. Weeds 12(2)134-139.
Water Quality Criteria.  1968.  Report  of the
  Technical Advisory Committee to the Secretary
  of the Interior. U.S. Dep. Inter., Fed. Water Pol-
  lut. Contr. Admin.
Weed Science Society of America. 1974. Herbicide
  handbook  of the  Weed Science  Society of
  America. 3rd ed. p. 29-35. Champaign, 111.
Wellborn, T.L.,  Jr.  1969. The toxicity of nine
  therapeutic and herbicidal compounds to striped
  bass. Prog. Fish. Cult. 31:27-32.
 Common name:
 Chemical name:

 Other names:
 Registered use:
Trichlorfon
Dimethyl-(2,2,2-trichloro-l-
hydroxy-ethyl)  phosphorate
Dylox
Control of the gypsy moth lar-
vae on forest land shade trees.
                  References

 Borough, H.W., N.M. Randolph, and H.G. Wim-
   bish. 1965.  Imidan and trichlorfon residues on
  coastal Bermuda grass. Tex. Agric. Exp. Stn.
  Prog. Rep. PR-2385.
Jensen, L.D., and A.R. Gaufin. 1966. Acute and
  long-term effects on organic insecticides on two
  species  of stonefly  naiads.  J.  Water  Pollut.
  Control Fed. 38:1273-1286.
Matton, P.,  and  O.N. LeHam.  1969. Effect of
  organophosphate Dylox on rainbow trout larvae.
  Can.  Fish. Res.  Board 26:2193-2200.
Newton, M., and J.A. Norgren. 1977. Silvicultural
  chemicals and protection of water quality. EPA
  910/9-77-036.
Pickering, Q.H., C. Henderson, and A.E. Lemke.
  1962. The  toxicity of organic phosphate insec-
  ticides to different species of warm water fishes.
  Trans. Am. Fish. Soc. 91:175-184.
Pimentel, D. 1971. Ecological effects of pesticides
  on non-target species. Exec. Off. Pres., Off. Sci.
  and Technol., Washington, B.C.
Sanders, H.W., and O.B. Cope. 1966. Toxicities of
  several pesticides to two species of cladocerans.
  Trans. Am. Fish. Soc. 95:165-169.
Schafer, E.W. 1972. The acute oral toxicity of 369
  pesticidal,  pharmaceutical  and  other chemicals
  to wild birds. Toxicol.  and Appl.  Pharmacol.
  21:315-330.
Wilcox, H.N. 1971. The effects of Bylox on a forest
  ecosystem. Lake Ont.  Environ. Lab. Prog. Rep.,
  State Univ. Coll., Oswego, N.Y.
                                              XI.62

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                                          GLOSSARY
  Below is a glossary of terms appearing in the text
of this handbook. Those terms drawn from specific
sources have been cited with a code in parentheses
following the definition.  Such citations are listed
under "Sources" at the end of the Glossary (e.g.,
DOT stands for "Dictionary of Geological Terms").
Those terms with no citations have had a definition
prepared for use in this handbook. Words not listed
in the glossary can be found in standard sources.

Access road: Any road used to gain access to an
  area for the purpose of carrying out some form of
  management. These roads may be a temporary
  or permanent part of the transportation system.

Active flood plain: See Bankful  stage.

Activity: Work  processes conducted  to produce,
  enhance,  or maintain  outputs  or to achieve
  management and environmental quality  objec-
  tives.

Acute toxicity: Brief and severe physical and/or
  psychological  disturbances  resulting  from  a
  single dose or exposure to a toxic or poisonous
  substance.

Advected  energy [fluxes]: The process  of energy
  transport  by the atmosphere or water bodies
  from one location to another due to circulation of
  these bodies.

Aeration potential: (See Oxygen  saturation level.)

Aerial drift: The movement of pesticide droplets or
  particles by wind and air currents from the target
  area to an  area  not intended  to  be treated.
  (PAST)

Aerial skidding: The process  of hauling logs by
  sliding them off the ground along  a cable. (SAF)

Aggradation:  The  raising of  the  surface of
  streambeds, floodplains, and  the  bottoms of
  other water bodies by the accretion of material
  eroded and transported from other areas. It is the
  opposite of degradation.
Aggraded stream: A stream that has built up its
  grade or slope by deposition of sediment. (DGT)

Ammonification: The biochemical process whereby
  ammoniacal nitrogen is released from nitrogen-
  containing organic compounds. (SSSA)

Ammonifying  microorganisms:   Microorganisms
  that  are   responsible  for ammonification of
  nitrogen-containing organic material. (See Am-
  monification.)

Angle of internal friction (coefficient of friction):
  The angle  at which the driving forces in a soil
  mass due to gravity are equal and opposite to the
  resisting forces due to friction; a measure of soil
  strength due to interlocking of individual soil
  particles.

Angular canopy density (ACD): A measure of the
  canopy density  along the path of incoming solar
  radiation. It is measured using a gridded mirror
  tilted at an angle so that a person looking down
  on the mirror views the surrounding vegetative
  canopy in the same perspective as the incoming
  solar radiation.  The number of grids covered by
  the canopy can  be  measured and converted to a
  percent canopy  cover.

Animal skidding: The use of animals such as mules
  or horses to slide loads along the ground.

Antecedent moisture: The degree of wetness  of a
  soil at the beginning of a runoff or storm period,
  expressed as an index or as the total volume of
  water stored in  the soil. (WPG)

Antecedent rainfall:  The rainfall or precipitation
  occurring during some period prior to the event
  of interest. This expression is intended to express
  watershed wetness. (VTC)

Aquatic environment: An environment in which all
  conditions, circumstances, and influences sur-
  rounding and affecting the  development of an
  organism  or groups  of organisms pertain to
  water. (WPG)
                                               xn.i

-------
Area-inches:  A measure of volume. One inch of
  depth  over the  entire surface of a delineated
  piece of land.

Armor: (1) To apply rock, mulch, or vegetation to
  damaged areas to serve  as protective covering.
  (2) To  use rock, concrete, asphalt, gravel, riprap,
  gabions, or equivalent for protection of a ditch,
  channel, or low water crossing. (3) Any natural-
  occurring  quality,  characteristic, situation  or
  thing that  serves as a protective  covering.

Aspect: The compass direction that the slope of the
  land faces toward (e.g., north, northwest, south),
  (WPG)

Balanced  road construction:  Cut-and-fill  road
  design; material cut on the uphill side of a road is
  placed in fills on the downhill side.

Balloon logging: A system which employs balloons
  to transport timber from the stump to a collec-
  tion point.

Bankful  discharge: Discharge at a river cross sec-
  tion which  just fills  the channel to the tops of the
  bank,  marking  the  condition  of  incipiant
  flooding.

Bankful  stage: Water surface  elevation  of the ac-
  tive floodplain.

Bankful  width: The width of the effective area of
  flow across a stream channel when flowing at
  bankful discharge.

Bare soil: Mineral soil without vegetative ground
  cover,  rock, or litter on the  soil surface.

Basal  area: The area  of the cross-section of a tree
  stem near its base, generally at breast height and
  inclusive of bark. Stand basal area is generally
  expressed as the total basal area per unit area.
  (SAF)

Baseline  condition: Hydrologic state of a watershed
  where   complete   hydrologic  utilization  is
  achieved. (See Complete hydrologic utilization)

Bedding:  A  silvicultural  process  where soil  is
  placed in long ridges approximately 6 inches high
  and  6 feet at the base to elevate tree roots above a
  high water table or to concentrate soil nutrients
  where  they can be readily utilized.

Bedding  planes: Planar or nearly planar surfaces
  that visibly  separate each  successive layer of
  stratified rock.
Bedload: Material moving on or near the stream
  bed  by rolling, sliding and sometimes making
  brief excursions into the flow a few diameters
  above the bed. It is not synonymous with dis-
  charge of bed material.

Bedrock sink: Term used to denote when bottom
  bedrock  is functioning as a heat sink within a
  flowing stream. (See Energy sink)

Bench: A working level  or step  in a cut which is
  made in several layers. A small terrace or com-
  paratively level platform breaking the continuity
  of a  slope.  (DOT)

Best Management Practices (BMP): A practice or
  combination of practices that are determined (by
  a state or designated area-wide planning agency)
  through  problem  assessment, examination  of
  alternative  practices,  and  appropriate  public
  participation  to  be the  most effective,  prac-
  ticable (including technological, economic, and
  institutional  considerations)  means   of
  preventing or  reducing the amount of pollution
  generated by non-point sources to a level com-
  patible with water quality goals.

Biochemical oxygen  demand (BOD): The amount
  of dissolved oxygen, generally expressed in parts
  per  million,  required  by  organisms  for the
  aerobic biochemical decomposition of organic
  matter present in  water. (WWU)

BMP:  (See Best Management Practices.)

BOD:  (See Biochemical oxygen  demand.)

Braided  stream: A  stream  flowing  in several
  dividing  and reuniting channels resembling the
  strands of a braid,  the cause of the division being
  the obstruction by sediment  deposited by the
  stream.

Broadcast burn: Allowing a controlled fire to burn
  over a designated area within well-defined boun-
  daries  for  reduction  of fuel hazard,  as  a
  silvicultural treatment or both. (SAF)

Bucking:  To  cut tree length  logs into shorter
  lengths.

Buffer strip: (See Waterside area.)

Cable  logging: Cable systems are designed to yard
  logs  from the felling site by a machine equipped
  with multiple winches. Cable logging is highly ef-
  ficient for logging steep rough ground on which
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  tractors cannot operate. Cable systems could be
  classified as either high lead, skyline, or balloon.
  (CEAP)

Cable yarding: Operation of hauling logs to a col-
  lection  point using a cable system. (See cable
  logging.)

Caloric  deficit: The energy  (calories) needed to
  bring a snowpack temperature up to an isother-
  mal temperature of 0° C.

Canopy: The more  or less  continuous  cover of
  branches  and foliage formed collectively  by the
  crowns of adjacent trees and other woody growth.
  (SAF)

Carbamate: A  synthetic organic pesticide which
  contains carbon, hydrogen, nitrogen, and  sulfur,
  and belongs to a group of chemicals which are
  salts or esters of carbonic acid. Carbamates may
  be fungicides, herbicides, or insecticides. Exam-
  ples:  aldicarb,  carbaryl, carbofuran, and
  methomyl.

Cation exchange: The exchange of cations held by
  soil particles with other cations that are  in the
  water solution surrounding the soil particles.

Cation exchange capacity (CEC): The sum total of
  exchangeable cations that a soil can absorb. Ex-
  pressed in milliequivalents per 100 grams of soil
  or per gram of soil (or of other exchangers such as
  clay). (SCS, SSSA)

Channel bars: An alluvial deposit or bank of sand,
  gravel,  or other material  at  the  mouth of a
  stream or  at any point in the stream itself which
  causes an obstruction to flow.  (NIA)

Channel gradient  change:  A change in  channel
  slope  which can  alter energy relationships that
  can, in turn, cause streambank and channel ero-
  sion or aggradation.

Channel interception: That portion of precipitation
  that falls directly into the channel or into open
  water channel extensions.

Channel stability:  The relationship  of sediment
  supply and stream energy available in a channel
  system.  As changes  occur  in  either supply or
  energy, the channel stability is affected and the
  channel tends to adjust its boundaries to accom-
  modate the change, i.e., when the supply exceeds
  the carrying capacity (aggradation occurs) or the
  energy exceeds supply (degradation occurs).
 Channel stability rating:  A numerical rating of
   channel  stability  using Pfankuch's  (1972)
   procedures which account for hydraulic forces,
   resistance of channel to flow forces, and  the
   capacity of the stream to adjust and recover from
   changes in flow and/or sediment load.

 Chemical-biological  balance:  Biological  balance
   relating  to  the relationship of the  earth's
   chemicals   to  plant and  animal  life
   (biogeochemical).  (WPG)

 Chip and  spread: Converting wood  to chips and
   scattering the resultant material. (SAF)

 Chlorinated  hydrocarbon:  A  synthetic  organic
   pesticide that contains  chlorine,  carbon, and
   hydrogen;  they are  generally very persistent
   (compared to carbamates or organophosphates).
   Examples: DDT, endrin, lindane.  Same as
   Organochlorine.

 Chronic  toxicity:  Physical and/or psychological
   disturbances  resulting from repeated doses or ex-
   posure of a poisonous or toxic substance over a
   period of time.

 Claypan: A dense, compact layer in the  subsoil
   having a much higher  clay  content  than the
   overlying material, from which it is separated by
   a sharply defined boundary. (SSSA)

Clay stone: An  indurated clay having the texture
  and composition, but lacking the fire lamination
  or platyness of shale.

Clearcutting: The harvesting in one cut of all trees
  on an  area for the purpose of creating a new,
  even-aged stand. The area harvested may be a
  patch, stand,  or strip large enough to be mapped
  or recorded as a separate age class.

Cohesion: The  bonding of soil  particles by thin
  water films, generally resulting in an increase in
  shear strength up to  some minimum moisture
  content.

Cohesive soils: Soils that have relatively high shear
  strength when moist.

Colluvial debris (colluvium): A general term ap-
  plied to loose  and incoherent deposits, usually at
  the foot  of a slope or cliff and brought there
  chiefly by gravity. Talus  and  cliff debris are in-
  cluded in such deposits.  (DOT)
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Compaction: The packing together of soil particles
  by instantaneous forces exerted at the soil sur-
  face  resulting  in  an increase in soil  density
  through a decrease in pore space.

Complete hydrologic utilization: Exists when the
  vegetation  onsite is  capable of utilizing water
  and energy at the maximum rate for the species
  and site.

Condition: Refers  to  a  hydrologic  state  of a
  watershed, i.e., baseline, existing or  proposed.

Cover  density: An  index  which references  the
  capability of the stand or cover to integrate and
  utilize the energy input to transpire water. It
  varies according to crown closure, vertical foliage
  distribution,  species, season, and stocking.

Creep: (See Soil creep.)

Cribbing: A structure which can be made of metal,
  treated timber, or precast reinforced concrete,
  generally  not watertight, used  to contain  un-
  stable earth masses either above or below a road
  surface.

Critical temperature threshold: The temperature
  at which physiological effects on fish begin to be
  produced. The  temperature threshold is an in-
  dicator of other water constituents such as dis-
  solved oxygen.

Crop tree: Any tree forming or destined to form a
  part of the forest crop. Usually a tree selected in
  a young stand or plantation to be carried through
  to maturity.  (SAF)

Cross drainage: A means,  generally a  culvert, of
  moving water from the uphill side of a road to the
  downhill side.

Crown closure: The percent of vegetation crown
  compared to open area as determined from an
  aerial photograph.

Cut-and-fill:  Fill  — the material  added to reach
  the formation  level. Cut  — the  excavation
  formed  when the material is removed.

Cut  banks: The  concave  wall  of a meandering
  stream that is maintained as a steep or overhang-
  ing cliff by the impinging of water at its  base.
  (See also Cut slope.) (DOT)

Cut slope: On sloping land, exposed banks above a
  road created by excavation during road construc-
  tion.
Cutting block: Cutting area or felling area. An area
  on which trees have been, are being, or are to be
  cut. (SAF)

Cutting plan: Part of the silvicultural  plan  that
  describes  the  method  of cutting (clearcut,
  seedtree, etc.).

Debris avalanche: Rapid, shallow mass movement
  on a  hillslope involving soil, rock,  and organic
  matter; less fluid in behavior than debris flow.

Debris dam: A dam in a channel resulting from the
  collection of tree limbs, logs, and other obstruc-
  tions.

Debris flow:  Rapid, shallow mass movement on a
  hillslope involving soil, rock, and organic matter;
  more  fluid behavior than debris avalanche.

Debris in channel: Those obstructions in a stream
  channel as a result of silvicultural  activities or
  natural events.

Debris jam: See Debris  dam.

Debris slide: The slow-to-rapid downward move-
  ment of predominantly unconsolidated and in-
  coherent earth and debris in which the mass does
  not show  backward rotation but slides or  rolls
  forward, forming an irregular hummocky deposit
  which may  resemble  morainal topography.
  (DOT)

Debris torrent: Rapid, turbulent movement of soil,
  alluvium,  and  organic  matter  down a stream
  channel.

Defoliant: A herbicide which causes the leaves of a
  plant to drop off.

Degradation: The general lowering of the surface of
  the land or stream by erosive processes, by the
  removal of material through erosion and trans-
  portation  by flowing water. (DOT)

Denitrification:  The biochemical  reduction  of
  nitrate and/or nitrite to molecular nitrogen or an
  oxide of nitrogen.  Under some  conditions, it
  results  in  a  loss  of  nitrogen  from the forest
  ecosystem.

Deposition: The mechanical or chemical processes
  through which sediments accumulate in a resting
  place.

Desiccant: A material used to draw moisture from
  or dry up  a plant, plant part,  or insect. Desic-
  cants are used primarily for pre-harvest drying of
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  actively growing plant tissues when seed or other
  plant parts  are  developed but  only  partially
  mature; or for drying of plants which normally do
  not shed their  leaves, such as rice, corn, small
  grains, and cereals.

Detection limit: The level at which, with current
  technology, a water quality component  can be
  detected with certainty.

Directional felling:  Cutting trees so that  they  will
  fall in a predetermined direction for  purposes
  such as increased logging efficiency, minimizing
  stand damage, and  reduction in pollution  im-
  pacts.

Ditch check: A small dam or structure in a road
  ditch to slow water velocity.

Ditch drain: Means of moving concentrated water
  from an inside  road  ditch to an outside area.

Drag(s): A frame, usually  iron, for roughly leveling
  a relatively loose or  soft surface.  (SAP)

Dry fall: Deposition of solid particles from the at-
  mosphere during nonprecipitation events.

Dry ravel: Downslope movement of sediment parti-
  cles or small rock on steeper slopes without flow-
  ing water.

Duff: The matted, partly decomposed organic sur-
  face layer of  forested soils. (SOIL)

Earthflow: Slow (rates of centimeters to meters per
  year), deep-seated (failure plain commonly 5-15
  meters below surface) mass movement. (AGI)

Effective stream width: Length of shadow required
  to  reach from one bank to the other; thereby ef-
  fectively shading the stream.

Effective weight:  Dry weight of soil minus the ef-
  fect of buoyancy in the zone of saturation. (AGI)

Electrochemical   exchange:  Chemical  action
  employing a  current of  electricity (lightning) to
  cause or to sustain a chemical reaction. (DMM)

Endline: To winch in without the use of block or
  pulleys to change the direction of pull.

Energy aspect: Refers to a combination of elevation
  and three aspect classes — (1) north, (2) south,
  and (3) east  and west  — used  in determining
  energy   inputs  for  generating  snowmelt  and
  evapotranspiration estimates.
Energy balance: An accounting of all energy inputs
  and outputs within some defined system.

Energy sink: A place where energy can be stored or
  absorbed  for use at some other time or place.

Enrichment ratio: The concentration of nitrogen or
  phosphorus  in the eroded material divided by its
  concentration  in the soil proper. (PNE)

Erosion—The  wearing away of the land surface by
  running  water,  wind, ice,  or  other geological
  agents, including such processes as gravitational
  creep.  Detachment and movement of soil or rock
  by water, wind, ice, or gravity. (SSSA)

The following  terms are used to describe  different
  types of water erosion:

  Accelerated  erosion—Erosion much more  rapid
    than normal, natural, geological  erosion,
    primarily  as a result of the influence of the ac-
    tivities  of man or, in some cases, of  animals.
    (SSSA)

  Channel  erosion: Erosion in which material is
    removed  by  water flowing  in  well-defined
    channels:  erosion caused by channel  flow.

  Gully erosion: The erosion process whereby water
    accumulates  in  narrow  channels  and,  over
    short periods,  removes the soil from from this
    narrow  area  to considerable depths ranging
    from 1 or  2 feet to as much as 75 to  100 feet.
    (SSSA)

  Rill  erosion:  An   erosion  process  in which
    numerous small channels of only a few inches
    in depth are formed; occurs mainly on recently
    cultivated soils. (SSSA)

  Sheet erosion. The  removal of a fairly  uniform
    layer of soil from the land surface by runoff
    water. (SSSA)

  Splash erosion: The spattering of small  soil par-
    ticles caused by the impact  of raindrops on
    very wet soils. (SSSA)

Erosion hazard: The possibility of soil loss due to
  erosion processes.

Erosion response unit: A delineated homogenous
  area that  will respond uniformly to forces which
  cause surface erosion.

ET: (See Evapotranspiration.)
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Evapotranspiration (ET): The loss of water from a
  given area by both evaporation from soil and
  open water surfaces, and by transpiration from
  plants.

Excess water: Increases in available water resulting
  from evapotranspiration  reduction from canopy
  removal. Excess  water can also be caused by
  reduced infiltration rates into bare or compacted
  soil.

Exchange surface: Surface of soil particles that ex-
  hibit  enhanced chemical activity, exchanging
  absorbed ions with ions present in the soil water.

Exfiltration: Water flowing from soil mantle back
  onto the soil surface from saturated soils due to
  bedrock  constrictions, concentration in  draws,
  excessive precipitation, etc.

Existing condition: The current hydrologic state of
  the watershed. It may be  thought of as, but is not
  necessarily  the  same   as  a  fully  forested
  watershed with  the trees capable of  maximum
  evapotranspiration  (ET) for the  energy and
  water available.

Factor of safety: A measure of the stability of a soil
  or rock mass, ratio of material strength retarding
  motion to applied stress tending to cause motion.

Fault: Surface or zone of rock fracture along which
  there has been displacement. (AGI)

Felling: The act of cutting down a standing tree.
  (SAF)

Fertilization: The  act of applying fertilizer.

Fertilizer: Any organic  or  inorganic material of
  natural or synthetic origin which is added to a
  soil to supply one or more elements essential to
  the growth of plants. (SSSA)

Field capacity index: The moisture content in the
  soil at one-tenth bar of soil-water pressure.

Fill  slope:  Man-made  slope  below  a roadbed
  resulting  from  road  construction  where  ad-
  ditional material is added to build up all or part
  of the road surface.

Filter strip: (See Waterside areas.)

Fireline: A term for any cleared strip used in fire
  control. More specifically, that portion of a con-
  trol line from which flammable materials have
  been removed by scraping or digging down to the
  mineral soil. (SAF)
Flow duration curve: A  graphical presentation of
  the percent of time streamflow equals or exceeds
  various levels of flow.

Fly logs:  Logs  carried completely off the ground
  during yarding.

Foliar drip: Loss of nitrogen from trees and under-
  story to litter and organic layer on forest floor.

Ford: An  unbridged stream crossing.

Forest cover density: An  index representing the ef-
  ficiency of a three-dimensional canopy system to
  respond to energy input.

Fracture:  Any break in  rock, whether or not  dis-
  placement is involved.

Fragipan: A natural soil horizon with higher bulk
  density than the overlying horizons, seemingly
  cemented when dry but having a moderate to
  weak brittleness when wet. The layer is low in
  organic matter, mottled,  slowly or very slowly
  permeable to water, and may show occasional or
  frequent bleached cracks which define polygons.

Free water: The water  (liquid  state)  being held
  within a snowpack. This free  water is generally
  considered to be less than 6 percent by volume
  for free-draining snow.

Free water surface:  The surface of water  bodies
  (i.e., streams, lakes, ponds, etc.).

Frictional resistance: Mechanical resistance to the
  relative motion of contiguous bodies or of a body
  and a medium.

Fuel break: A wide strip  with a low amount of fuel
  in a brush or wooded area to serve as a line of fire
  defense and usually covered with grass to provide
  soil cover. (WPG)

Fuel management:  The  management  and
  manipulation of fuels (vegetation) so as to lower
  fire hazard.

Fuel management plan:  Part of the silvicultural
  plan that describes the type of fuel management
  to be used.

Full bench road:  (See Full bench section.)

Full bench section: To construct  a roadbed entirely
  on natural ground. Generally used on cross slopes
  55 percent or greater.
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Fungicide: An agent, such as a spray or dust, used
  for destroying fungi. (RHD)

Gabion:  A specially designed basket or corrosion
  resistant wire boxes used to hold rock and other
  coarse  aggregate. These  wire  boxes  may  be
  locked together to form sea walls, revetments,
  deflectors,  and other structures. (WWU)

Glacio-lacustrine clays:  Fine clay-size  particles
  deposited in  glacial lakes. Usually clay size  but
  not clay minerals.

Gravitational stress: Acceleration of a mass due to
  gravity.

Ground  cover: Any  material (i.e.,  rock, litter,
  vegetation) which is attached to or lying on the
  soil surface.

Ground-lead  cable yarding systems:  A method of
  powered cable logging in which a main line is led
  out to the logs through a lead block  fastened
  close to the ground level. Generally operated by a
  double-drum power unit carrying the main and
  haul-back lines. (SAF)

Gunite: (See Shotcrete.)

Hand  pulpwooding:  The  procedure  of  driving
  trucks through the woods to  felling sites and
  hand-loading wood  cut primarily for manufac-
  turing into wood pulp.

Hardpan: A hardened or cemented soil horizon or
  layer. The soil material may be cemented by iron
  oxide,  silica,  calcium carbonate, or other sub-
  stances.  The hardness does  not  change  ap-
  preciably with changes in soil moisture content.

Harvesting: (See Timber harvesting.)

Hazard index:  Indicates the  intensity of analysis
  that may be necessary to  adequately  evaluate
  soil mass movement potential.

Headwall scarp: Steep (generally 50°) slope at  the
  upslope  end  of a  mass  movement landform
  produced  by  the  downslope  movement  of
  material away from the face. (AGI)

Heat flux: The quantity of heat transported during
  a given time  period through a unit area that is
  perpendicular to the flow direction.

Heat sink: (See Energy  sink.)

Helicopter logging: A system for hauling timber
  from stump to a collection point that employs a
   helicopter  as  the  means of transportation.
   (CEAP)

 Herbicide: A substance used to inhibit or destroy
   plant growth. If its effectiveness is restricted to a
   specific plant or type of plant, it is known as a
   selective herbicide. If its  effectiveness covers a
   broad  range of plants,  it  is considered to be a
   non-selective herbicide. (WPG)

 Heterotrophic bacteria: Bacteria requiring com-
   plex organic compounds of nitrogen and carbon
   for metabolic synthesis.

 High-lead logging: A method for transporting logs
   from the stumps to a collecting point by using a
   power cable, passing through a block  fastened
   high off the ground, to  lift the front end of the
   logs clear of the ground while dragging them.
   (CEAP, SAF)

 High-lead yarding: The initial hauling to a col-
   lecting point in a high-lead logging system. (See
   High-lead logging.)

 Hummocky topography:  Irregular  landscape  of
   benches  and depressions, indicative  of  mass
   movement activity.

 Humus layer:  The well-decomposed, more or less
   stable, part of the organic matter in mineral soil.
   (SOIL)

 Hydrographic area: A small sub watershed of a first
   order watershed.

 Hydrologic province:  A subunit of a  hydrologic
   region. Provinces are divided based on  major
   climatic  and  hydrologic  differences.  (See
   Hydrologic regions.)

 Hydrologic  regimes:  The  climatic,  lithologic,
   topographic, vegetation factors, and the tem-
   poral  distribution of seasonally variable factors
   which determine the extent of stability between
   a stream and its drainage  basin.

Hydrologic  regions:  Regions  that have  been
  delineated based upon  major climatic and
  hydrologic differences.

Hydrologic utilization: The  use of soil-water  for
  biological growth and maintenance. Complete
  hydrologic utilization is equivalent to potential
  evapotranspiration.

Hydrolyzation: A chemical decomposition in which
   a compound undergoes a reaction with water
  resulting in  new compounds or ions.
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Ignition pattern: Distribution of many individual
  fires over an area simultaneously or in quick suc-
  cession. (KPD)

Impacted areas:  Uncut  and  cut areas of  the
  watershed which are affected by a  silvicultural
  prescription.

Immobilization: The chemical or physical binding
  of ions and compounds such that they are not
  chemically active or capable of going into solu-
  tion.

Impaired drainage: Where subsurface  water move-
  ment is obstructed by a relatively impermeable
  material, as at the failure plane of an earthflow.
  (AGI)

Incident heat load: The source of heat influx that
  causes water temperature to increase.

Incipient drainage depression: Linear depression
  orientated  downslope  that may carry surface
  runoff only during infrequent storms, commonly
  the site of debris avalanche-debris  flow.

Incremental  precipitation:  The  amount  of
  precipitation falling over some specified interval
  of time.

Infiltration rate: A soil characteristic  determining
  or describing the maximum rate at  which water
  can  enter the soil under specified conditions, in-
  cluding the presence of  an  excess  of water.
  (SSSA)

Inorganic  phosphorus:   Phosphorus  compounds
  that do  not include  carbon. Ionic forms are
  readily soluble in water.

Insecticide: A pesticide used to control insects.

Inside road ditch:  A channel located adjacent to a
  road at the foot of the cut bank designed to con-
  centrate water and reduce erosion on the road.

Insloped road: A road sloped (at  1 to 2 percent)
  toward the cut bank to facilitate the drainage of
  water off of the  road surface.

Insoluble component: That portion of the nutrients
  entering  a stream as  relatively insoluble com-
  pounds or ions via surface flow either adsorbed to
  soil  particles or  as suspended solids.

Integral arch: An arch attached to the skidding
  machine to provide lift to the loading end of the
  log,  and to improve the ease of backing up on
  rough steep terrain.
Interception  loss: That  portion  of precipitation
  that is caught and retained on vegetation, litter
  layer or structures and subsequently evaporated
  without reaching the ground. (GOM)

Intracycle: A cycle (i.e., nutrient cycle) within the
  ecosystem. The forest nutrient cycle is generally
  segmented into three compartments: inputs, in-
  tracycle, and outputs.

Intracycle  process:  Biochemical processes  taking
  place within an intracycle. (See Intracycle.)

Intragravel water: Water within the pore spaces of
  stream bottom gravel material.

Isothermal snowpack:  A snowpack that has  the
  same temperature throughout its vertical profile.

Jackpot burn: (See Spot burn.)

"Jack-strawed" trees: Patch of trees tipped in dif-
  ferent directions, commonly indicative of mass
  movement activity. (AGI)

Jammer:  A light weight 2-drum winch  with a
  wooden spar,  generally mounted on a  vehicle
  which  is used  for both skidding and loading.
  (SAP)

Joint:  Surface of actual or potential fracture or
  parting in a rock, without displacement.

Landslide: Sudden  downslope movement of earth
  and  rock.

Land system inventory: A seven level land inven-
  tory  system which uses selected  differentiating
  characteristics  of soils, natural vegetation, and
  geology for  identifying and delineating compo-
  nent parts of a landscape. The  maps and as-
  sociated legends produced  at a given inventory
  level provide data for  use  at selected levels of
  land management.

Latent heat exchange: Energy given off or absorbed
  in a  process (evaporation/condensation).

Leaf area index: Ratio of leaf surface area to pro-
  jected ground  surface area.

Leave  strip: (See Waterside area.)

Limiting nutrient: An essential nutrient which is
  not available to timber in adequate amounts to
  insure normal growth (i.e., nitrogen, phosphorus,
  and  potassium).

Linear depression: Incipient drainage depression.
                                                XH.8

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Litter interception: That component of precipita-
  tion that is intercepted by the litter layer and
  eventually  evaporated back to the atmosphere.

Litter layer:  The surface layer of the forest floor
  consisting of freshly fallen leaves, needles, twigs,
  stems, bark, and fruits. (SAP)

Logging plan: Part of the silvicultural plan that in-
  cludes a planimetric map which depicts the type
  of logging system, landings, and road plan to be
  used.

Log landing:  Any place where round timber is as-
  sembled for further transport, commonly with a
  change of transport method. (SAP)

Lop  and scatter:  To chop branches, tops, and
  small trees after felling and  then spread the
  resulting materials more or less evenly over the
  ground without burning. (SAP)

Lopping: Cutting off one or more branches of a
  tree, whether standing, felled,  or fallen. (SAP)

Machine pile (and burn):  Slash which is put in
  piles by machinery to subsequently be burned.

Manning's equation: An empirical formula used to
  calculate the velocity of flow based on channel
  roughness,  the hydraulic radius, and the slope of
  the energy  gradient line.

Mass failure: (See Mass wasting.)

Mass movement: Unit movement of a portion of
  the land surface as in creep, landslide, or slip.

Mass wasting: A  general  term for a variety of
  processes  by which  large  masses of  earth
  materials are moved by gravity either slowly or
  quickly from one place to another.

Masticate:  Chewing or grinding wood into  small
  pieces.

Mechanized  logging operations:  The use of self-
  propelled ground equipment to fall and  bunch
  and/or limb and buck or top a tree.

Melt threshold temperature: An index temperature
  relating to when the snowpack will begin to melt.

Microrelief:  Small-scale, local differences in
  topography that are only a few feet in diameter
  and have elevational differences of a few  inches
  to 6 feet. (SSSA)
Mineral soil: A soil  consisting predominantly of,
  and  having  its properties  determined
  predominantly by, mineral matter. Usually con-
  tains less than 20 percent organic matter, but
  may contain an organic surface layer up to 30 cm
  thick. (SSSA)

Mineralization: The release of mineral matter from
  organic  matter as  a result of microbial decom-
  position.

Mitigative controls:  The physical, chemical, or
  vegetative measures  applied to  ameliorate ex-
  isting problems.

Modified Soil Loss Equation (MSLE): The Univer-
  sal Soil Loss Equation (USLE)  as it has been
  revised for application to forest conditions.

Mohr-Coulomb Theory of earth failure: States that
  failure in a material occurs if the shear stress on
  any  plane equals the  shear strength of the
  material. (AGI)

Montmorillonite: (See Smectite.)

Mudflow:  Rapidly flowing mass of predominantly
  fine-grained  earth materials possessing a high
  degree of fluidity during movement.

Mulch: (1) Any material such as straw, sawdust,
  leaves, etc., that is spread upon the surface of the
  soil to protect the soil and plant roots from ef-
  fects of  raindrops,  soil  crusting,  freezing,
  evaporation,  etc. (SSSA) (2) Any loose covering
  on the surface on  the soil, whether natural, —
  like litter, or deliberately applied like  straw,
  grass, or foliage, or artificial material such as cel-
  lophane. Used to conserve moisture, check weed
  growth,  and protect from climate. (SAP)

Natural event: Event that takes place according to
  the laws of nature  — inherent — not induced or
  changed by man's activities.

Nitrification: Biological oxidation of ammonium to
  nitrate or a biologically induced increase in the
  oxidation state of nitrogen.

Nitrogen fixation: Biological conversion of elemen-
  tal nitrogen (N2) to organic combinations or to
  forms utilizable in biological processes. (SSSA)

Nitrosomonas: A soil bacteria that obtains energy
  for growth by oxidizing ammonia to nitrites.

Non-cohesive soil: Soil with a relatively low shear
  strength.
                                                XE.9

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Non-point sources:  For silviculture,  sources from
  which the pollutants discharged are: (1) induced
  by  natural  processes, including precipitation,
  seepage,  percolation,  and  runoff;  (2)  not
  traceable  to any discrete or identifiable facility;
  and (3) are better controlled through the utiliza-
  tion of Best Management Practices, including
  process and  planning techniques.  (EPA)  Non-
  point sources as used in this document includes
  natural pollution  sources not  directly or  in-
  direclty caused by man.

Normalized  hydrograph:  Representative
  hydrograph expressed as the percentage of an-
  nual flow which can or will occur during any 6-
  day interval.

Nutrient availability: The state in which nutrients
  must be to be available to plants.

Onsite: The specific area on which an event, occur-
  rence,  or  activity has taken or will take place.

Onsite chemical balance changes: Silvicultural ac-
  tivity can result in release of chemicals which, in
  turn, may leach or wash into streams, thereby af-
  fecting nutrient and Biochemical Oxygen De-
  mand  (BOD) levels in water.

Open water: (See Free water surface.)

Organic  phosphate:  Phosphorus compounds that
  include carbon. They are not generally found  as
  water soluble ions.

Organophosphate: A synthetic  organic pesticide
  which  contains  carbon,   hydrogen,  and
  phosphorous.  It  acts by inhibiting a blood
  chemical  called  "Cholinesterase." As  a  rule,
  organophosphates  are less persistent than the
  chlorinated  hydrocarbon family. Examples:
  malathion and parathion.

Outslope construction: Used  in construction  to
  spread both the material and the potential flow
  of water out over a very large front with a subse-
  quent low energy per unit for transport.

Overland flow  (sheet flow): Runoff water which
  flows over the ground surface as a thin layer and
  does not infiltrate prior to reaching a stream,  as
  opposed to the channelized (concentrated) runoff
  which  occurs in rills and gullies. (WPG)

Overload stream: An aggraded stream, one with an
  excess  of sediment  supply  as evidenced  in a
  braided stream.
Overstory: That portion of trees in a forest forming
  the uppermost canopy layer.

Oxygen saturation levels: The maximum amount
  of oxygen  that theoretically  can be dissolved
  within  water for  the given  temperature  and
  elevation.

Patch cut: A modification of clearcutting. A 40- to
  200-acre area cut as single settings, separated for
  a  long as practicable,  preferably until  the
  regeneration is  adequately shading the forest
  floor. (SAF)

Permeability class: An arbitrary classification  of
  soil permeability into classes  (i.e., very slow,
  slow,  slow to moderate, moderate, etc.) Used in
  determining the soil erodibility factor (K) of the
  Modified Soil Loss  Equation.

Pesticide: A chemical substance, compound,  or
  other agent used to control, destroy, or prevent
  damage by a pest.

Phreatophyte: A plant that habitually obtains its
  water supply from the zone of saturation, either
  directly or  through the capillary fringe. (DMM)

Piezometric  surface: An  imaginary  surface
  representing the static head of groundwater and
  defined by  the level to which water will rise in a
  well.

Piping (soil piping): Subsurface erosion that  causes
  the formation of tunnel-like cavities.

"Pistol-butted"  trees: Trees with a  "J" shaped
  base with the  stem  displaced downslope,  due to
  mass  movement,   snow  creep,  and  other
  processes.

Planar failures: Shallow soil mass movement with
  a nearly flat plane of failure.

Plant growth regulator: A substance or organism
  that increases, decreases, or in some way changes
  the normal growth or reproduction of a plant.

Plow layer: A surface soil layer that has been mixed
  by human activities to an extent that the original
  properties of the soil have been modified.

Point bars: Sediment  deposited on the inside  of a
  growing meander loop. (DGT)

Pollution:. The manmade or man-induced altera-
  tion of the chemical,  physical, biological  and
                                               XII.10

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  radiological integrity of water. (Section 502, PI
  95-217 clean Water Act)

Pool areas: A body of water or portion of a stream
  that is deep and quiet relative to the main cur-
  rent.  (NIA)

Pore space: The volume of the various pores in a
  soil. The space not occupied by solid particles.

Pore  water  pressure: The  stress  transmitted
  through the fluid that fills the voids between par-
  ticles of a  soil or rock mass.

Prescribed fire (prescribed burn): Skillful applica-
  tion of fire to natural fuels under conditions of
  weather, fuel  moisture, soil moisture, etc., that
  will allow confinement of the fire to a predeter-
  mined area and  at the same time  will produce
  the intensity  of heat and rate of spread to ac-
  complish certain planned benefits. (KPD)

Prescribed underburning:  Skillful application of
  fire used to reduce fuels under stands following
  logging to reduce fuels created by some cultural
  treatments; to kill unwanted trees and shrubs
  and/or reduce fuels from leaf and needle fall; and
  to control  certain tree diseases. It  is successful
  only with fire-resistant tree species and low to
  moderate fuel loadings.

Preventive controls: Those controls that apply to
  the pre-implementation,  planning  phase  of  a
  silvicultural activity.

Probit: a  statistical unit of measurement  of
  probability based on deviations from the means
  of a normal frequency distribution.

Proctor curves: Curves resulting from the standard
  Proctor compaction test showing the variation of
  optimum soil-water content related to maximum
  density. (EM)

Proposed  condition:  The  hydrologic  state  of  a
  watershed following a proposed silvicultural ac-
  tivity.  It  is  synonymous  with  the  "post-
  silvicultural" activity condition.

Procedural controls: Those controls that are con-
  cerned  with administrative  actions of  a
  silvicultural activity.

Raindrop splash erosion: (See Erosion.)

Reaeration: The replenishment of deficit  oxygen
  concentration  in water.
Reflectivity:  The  fraction  of radiation  that is
  reflected back to the sky by the snowpack. A
  term used in energy budget modeling.

Release: Freeing a tree, or group of trees, from more
  immediate competition by cutting, or otherwise
  eliminating, growth that is overtopping or closely
  surrounding them. (SAP).

Residual soil: Soil developed in situ from underly-
  ing parent material.

Resource  impacts:  Change  to the resource  that
  alters natural processes.

Restricted drainage:  Where  subsurface water
  movement is  obstructed  by  a  relatively
  impermeable material, as  at the failure plane of
  an earthflow.

Retaining structure:  Structure  which retains  or
  restrains an oversteepened slope.

Rheological flow: A more or less viscous liquid flow
  of solid material.

Riffle: A shallow rapids in an open stream where
  the water surface is broken into  waves by
  obstructions wholly or partly submerged. (NIA)

Ripping: (See Soil ripping.)

Riprap: A foundation or sustaining wall of stones
  put together without order on an embankment
  slope or water course to prevent erosion.

Rodenticide:  A pesticide used to control rodents.

Rolling chopper: A cylindrical roller or water-filled
  drum equipped with several full-length cutting
  blades. Its purpose is to crush and cut brush and
  slash into small lengths.

Rolling dip: (1) To conform a road to the landscape
  by following the natural grade changes. (2) Used
  when constructing a road on nearly level terrain
  to provide for drainage by making small changes
  in grade.

Rotational failure: Mass movement with concave
  failure plane.

Sag pond: Poorly  drained depression formed  by
  rotational mass movement.

Salvage cut: The harvesting of trees that are dead,
  dying, or deteriorating (e.g., because overmature
  or materially damaged by fire, wind, insects, or
                                               xn.n

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  other  injurious  agents)  before  the  timber
  becomes worthless.

Saturated hydraulic conductivity: A measure of
  the rate of water traversing a unit area of soil in
  unit time per unit hydraulic gradient with the
  soil in a saturated condition.

Scalping: Paring off low  and surface vegetation
  together with most  of its roots  to  expose a
  vegetation-free soil  surface,  generally
  preparatory to sowing or planting. (CEAP)

Scarification: Loosening the topsoil or breaking up
  the forest floor to expose mineral soil.

Scour: Removal of loose material by running water,
  from the wetted portion of a stream channel.

Sediment:  (1) Particles derived from rocks or
  biological  materials that have been transported
  by a fluid. (2) Solid material (sludges) suspended
  in or settled from water.

  Sediment  delivery index: An estimated fraction
    of the total potential soil loss from a disturbed
    site  that  may  be moved over  land and
    deposited in a stream channel.

  Sediment  delivery ratio: The volume of sediment
    material actually delivered  to a point in a
    watershed divided  by the total amount of
    material available for delivery.

  Sediment  discharge (yield): The average quan-
    tity of sediment, mass or volume, but usually
    mass, passing a section in a unit time. The
    term may  be qualified as,  for example,
    suspended-sediment discharge, bedload dis-
    charge,  or total sediment discharge.

  Sediment  rating curve: A graphical representa-
    tion of the existing relationship between sedi-
    ment concentration  in mg/1 and stream dis-
    charge in  cfs.

  Sediment supply: The amount of inorganic sedi-
    ment made  available  in the  channel  for
    transport as either suspended or bedload sedi-
    ment. Sources of sediment include  contribu-
    tions from surface erosion and soil mass move-
    ment, and that derived from the channel itself.

  Sediment  transport: Term  used  to discuss the
    movement of sediment within a stream chan-
    nel system.
  Sediment trap: Usually  a  small  depression to
    capture sediment coming from  on-going con-
    struction. A temporary measure to trap sedi-
    ment.

  Suspended sediment: In the process by which
    running  water  transports  material,  smaller
    particles are lifted far from the bottom and are
    sustained for long periods before  being dis-
    tributed  through the whole body of the cur-
    rent. This constitutes  the suspended load or
    that component called suspended sediment.
    (DGT)

Seed  tree cutting:  Removing trees in a  mature
  stand so as to effect permanent openings of their
  canopies. This provides conditions for securing
  regeneration from the seed of trees retained for
  that purpose.

Selection  cutting:  A method  of logging  which
  removes trees from all size classes  in an uneven-
  aged stand to maintain proper stocking as incre-
  ments of trees  move  from  younger to older
  classes.

Serpentine:  A mineral of  the serpentine group,
  such as antigorite and chrysotile. These minerals
  are prone to mass erosion.  (DGT)

Shale: Fine-grained indurated detrital sedimen-
  tary rock formed by consolidation of clay, silt, or
  mud, and  characterized  by finely  stratified
  structure.

Shear strength: The internal resistance of a body to
  shear stress.

Shear stress: That component of stress which acts
  tangential to a plane through any given point on
  a body.

Sheet flow: Surface runoff which flows  over the
  ground in a thin layer as contrasted with runoff
  that is concentrated  in rills and gullies.

Shelterwood cutting: A method of harvest cutting
  involving two or three separate cuttings. The last
  cutting removes the shelterwood after adequate
  regeneration, encouraged by prior cuttings, has
  become established.

Shotcrete (also known as gunite): A  mixture of ce-
  ment, sand, or crushed slag and water sprayed
  over exposed soil on hillslopes to protect against
  surface erosion.
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Siltstone: Indurated silt having the texture and
  composition, but lacking the fine lamination of
  shale.

Silviculture: The science and art  of cultivating
  forest crops, based on a knowledge of silvics,
  which is the study of the life history and general
  characteristics of forest trees and stands with
  particular reference to locality factors, as a basis
  for the practice of silviculture (SAF).

  Silvicultural activity:  Activity associated with
     the care and cultivation of forest trees. It in-
     cludes  harvesting,  regeneration systems,  ac-
     cess systems, and various cultural practices
     (site preparation and timber stand improve-
     ment) that are appropriate to various manage-
     ment objectives.

  Silvicultural plan: A plan outlining a proposed
     silvicultural  activity, which should  include
     methods  of cutting,  felling,  yarding,  fuel
     management, site preparation,  miscellaneous
     cultural activities, and road and access system
     plans.

  Silvicultural state: The status of the vegetation
     complex on units of  land  to which a
     silvicultural prescription has been applied. A
     silvicultural system  or treatment actually ap-
     plied to  a  unit or  a description  of the
     vegetative cover on  all or a part of the unit.
     The state may  be  described  as  clear cut,
     thinned, forested, open, etc.

  Silvicultural  prescription:   The  management
     alternatives  applied  to  a watershed  or
     watershed subunit. The  delineation  of a
     watershed into a single unit or  series  of sub-
     units to which the prescription is to be applied,
     is based on uniformity of  soil depth, vegeta-
    tion, precipitation,  aspect, and other  unique
    site factors. A uniform practice over the entire
    unit or several practices resulting in more than
    one silvicultural  state  per  silvicultural
    prescription; i.e., the prescription may consist
    of patch cutting, thinning,  and leaving part of
    the area uncut.  The silvicultural prescription
    includes  for  each  unit  that  part  of  the
    silvicultural plan that affects the evapotran-
    spiration status  of the vegetation.

Simulation:  A  technique for analyzing complex
  inter-relationships among variables based upon
  known or  assumed influence of one variable on
  another. Often referred to as modeling, simula-
  tion provides a means of estimating and compar-
  ing the effects that a change in one or more of the
  variables will have on the other variables.

Site preparation: Preparing a site for the regenera-
  tion or planting of trees.

Site preparation plan: Part of the silvicultural plan
  that describes site preparation techniques to be
  used.

Site productivity: The present capability of a site
  for producing a specified  plant or sequence of
  plants under a defined set of management prac-
  tices.

Skidding (timber transport): A term for hauling
  loads by sliding  from stump to  roadside. The
  timber may slide more or less wholly along the
  ground (ground skidding)  with its  forward  end
  supported (high lead skidding) or wholly off the
  ground —  sliding along a cable — during its
  main transit (aerial skidding). (SAF)

Skid road  (skid trail): Any path,  more or  less
  prepared, over which logs are dragged. (SAF)

Skyline  cable  system: A cable logging system
  which employs a heavy cable stretched between
  two supports upon which traverses a carriage to
  support at least the leading end of the log. (SAF)

Skyline logging: A method for  transporting logs
  from  stumps  to  collecting points  that uses a
  heavy cable stretched between high points (such
  as in tall trees braced with guy lines) to function
  as an overhead track for a load carrying carriage.
  Logs  are lifted up by  cables or other similar
  devices, and powered cables are used to move the
  load  back  and forth  along  the main  cable.
  (CEAP)

Slope configuration change: Alteration of the land
  slope, such as occurs in roadbuilding when cuts
  and fills are constructed.

Slope gradient:  The  amount of inclination from
  horizontal of a piece of land. Gradient is expres-
  sed in degrees or percent (tangent of the slope
  angle which is the amount of rise divided by the
  horizontal distance).

Slump: A slip resulting  from the downward and
  backward rotation  of a soil block or  group of
  blocks with small lateral displacement. Closely
                                                XII.13

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  related to earthflow in terms of their occurrence
  and genetic process. (DGT)

Smectite clay:  Group of expanding  lattice  clay
  minerals. (AGI).

Snowpack ripening: The process of coarse crystal
  formation with an increase of the liquid phase
  within the  snowpack. (VTC)

Snow redistribution: The change in the distribu-
  tion  of snow  attributable to land management
  activities (i.e., increasing deposition in openings
  within forested areas).

Snow retention coefficient: A coefficient used in as-
  sessing snowpack redistribution associated with
  timber harvesting. The coefficient is the ratio of
  expected accumulation divided by the baseline
  or pre-harvest accumulation.

Soil creep:  Slow, gradual, more or less continuous
  permanent   deformation   of soil  under
  gravitational  body stress.

Soil mass movement: Movement of soil material en
  masse under gravitational body stress.

Soil resource  inventory: Term used by U.S.  Forest
  Service for the systematic examination of soils in
  the field and  laboratory, including descriptions,
  classifications,  and mapping  of soils  and
  management  interpretations according to their
  productivity and behavior under  use.  (See Soil
  survey.)

Soil ripping:  Act of breaking up hard gravel, soft
  rock,  tearing  out stumps and boulders.

Soil survey: The systematic examination, descrip-
  tion, classification,  and mapping of soils in an
  area.  Soil surveys are classified according to the
  kind and intensity of field examination. (SSSA)

Soil texture: The relative proportions of the various
  soil separates [sand, silt, and clay]  in a soil  as
  described by  the  classes of soil texture.  (SCS,
  SSSA)

Solar ephemeris: A table showing the  positions of
  the sun on a number of dates in a regular se-
  quence. (RHD)

Solar loading: The flux of solar energy reaching the
  forest floor or water body of interest.

Soluble component: That portion of the nutrients
  that enters  a stream  as soluble ions via surface or
  subsurface  flow.
Spot burn (jackpot): A method of burning where
  scattered concentrations of slash or other fuels
  are reduced  by  burning in place  under fuel
  moisture and weather conditions which maintain
  low flame lengths and fire intensities.

Stability threshold: The maximum change that a
  stream  reach can withstand  and still maintain
  it's morphological characteristics due to either
  sediment supply  and/or stream energy changes
  where channel  adjustments will be initiated to
  accommodate these changes over time.

Stage felling: To fell timber and remove it in stages
  so as to reduce breakage, normally small timber
  first.

Stations  (engineering):  A  unit  of measure
  equivalent to 100 horizontal linear feet.

Stiff  diagram:  A  method  of plotting  several
  variables using vectors on a graph, so that the
  combined effects of the variables are shown as an
  irregular polygon with a particular area.

Stream  aeration:  The process of  air being mixed
  with and re-entering  the stream water. This
  process  can be observed visually as white or
  foaming water.

Stream channel encroachment: Encroachment oc-
  curs when bankful discharge width of a stream is
  reduced due to direct alterations such as bridges,
  roadfills, culverts, organic debris, etc.

Stream   equilibrium: The  balance  of the
  availability of  sediment  supply  based on the
  erosional rates of adjacent slopes, the stream
  system, and  the energy available to transport
  this erosional debris in such a manner that the
  morphological  characteristics  of  the  stream
  channel are maintained.

Stream  gradient:  (See Water surface slope.)

Stream order: A method of numbering streams as
  part of  a drainage basin network. The smallest
  unbranched  mapped  tributary is called  first
  order, the stream receiving the tributary is called
  second  order, and so on.

Stream  power: Numerical  expression  of stream
  energy utilized  in determining bedload transport
  rate which is the product of water surface slope,
  stream  discharge, and a unit force factor of 62.4
  Ibs/ft3-width  of stream.
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Stream productivity: The amount of living matter
  actually produced within the stream under in-
  vestigation.

Stream shading changes: Changes that occur when
  trees  and/or understory  vegetation that  con-
  tribute to the shading of water in  streams are
  removed.

Streamside areas:  (See Waterside area.)

Streamside  management  zone:  (See Waterside
  area.)

Strip cutting: Removal of the crop in strips in one
  or more  operations, generally  for  encouraging
  regeneration. (SAP)

Stripping: Clearing or removing ground cover.

Structure  index:   An  index of  soil  structure
  (granular, blockly, massive, etc.) used in deter-
  mining the credibility (K) factor of the Universal
  or Modified Soil Loss Equation.

Subsurface flow: That part of the runoff that per-
  colates through the soil mantle primarily under
  the  influence of  gravity  before emerging as
  streamflow.

Surface erosion:  (See Erosion).

Swelling clays: Expanding  lattice clays which in-
  crease in  volume when  water  moves into  the
  crystal structure  and decrease in volume when
  water is removed.

Swing operation: Moving logs to a landing from a
  distant deck to  which they have been yarded.
  (CLS)

Symbiosis: The living together of two different
  organisms  with  a resulting mutual benefit. A
  common example includes the association of
  rhizomes with legumes.  The resulting nitrogen
  fixation is  sometimes called symbiotic nitrogen
  fixation. (See Nitrogen fixation).

Temporary road: A timber access road which is
  closed to traffic between timber needs.  When
  closed the  road is barriered,  scarified,  and
  reseeded to grass and forbs.

Tension cracks: Fissures in the earth formed by dif-
  ferential  displacement between two  blocks of
  earth caused by  tensional stresses.

Terracing: Use of terraces (raised levels with sloped
  front or sides) in site preparation.
 Thermal pollution: Disruption of the aquatic en-
  vironment or other beneficial use due to heating
  of a stream or other water body.

 Throughfall: The part of rainfall that reaches the
  ground directly  through the vegetative  canopy,
  as drip from leaves, twigs, and stems. (VTC)

 Timber harvesting: A general term for the removal
  of physically mature trees  in contrast to cuttings
  that remove immature trees. (SAF)

 Timber stand improvement:  A loose term compris-
  ing all intermediate cuttings made to improve
  the composition, constitution, condition, and in-
  crement of a timber stand. (SAF)

 Topographic shading:  Shading of  streams, water
  bodies, or other areas of interest by topographic
  features  positioned between the sun and area of
  interest, thereby eliminating direct solar radia-
  tion.

 Toxicity:   Quality,  relative  degree,  or   specific
  degree  of  being toxic or  poisonous  to  an
  organism; the ability of a substance or chemical
  to produce injury. (RHD)

 Tractor logging: Any system of logging  in which a
  tractor furnished the motive power, whether by
  direct hauling or by skidding. (SAF)

 Tractor skidding: Hauling logs by  sliding  using a
  tractor as the motive power. (SAF)

 Translational movement: Downslope movement of
  a mass of soil and/or rock on a surface roughly
  parallel to the general ground surface.

 Translocation of chemicals:  The movement of a
  chemical within a plant or animal after it has
  entered by some path.

Transmissivity of solar radiation: Ability of solar
  radiation to pass through the forest canopy to the
  forest floor, snow pack surface or water surface.

Transport capability: In general terms, the integra-
  tion  of several  variables  which influence the
  ability of the stream to transport the sediment
  made available.  The variables include velocity,
  gradient, bed roughness, existing sediment load,
  and particle size of material being transported.

 Transportation plan: A plan that coordinates the
  transportation system for  relatively large areas
  delineated by very limiting topographic features,
  economic centers, and legislative constraints. It
                                               XH.15

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  provides the interface for the logging road system
  and the public road system.

Transportation system:  The  transportation
  network  including  all existing and planned
  roads,  skid trails, bridges, airfields,  and other
  transport facilities wholly  or partly within or ad-
  jacent  to the watershed area for silvicultural ac-
  tivities. (WPG)

Trash  rack:  A  screen of parallel  bars or mesh
  placed across a stream or turbine intake to in-
  tercept floating debris. (DMM)

Treated  seed: Seeds  that are chemically treated
  with a pesticide or fertilizer.

Understory:  The woody  species  growing under a
  more or less continuous cover  of branches and
  foliage formed collectively by the upper portions
  of adjacent woody growth. (WPG)

Uneven-aged stands:  Stands with trees  that differ
  markedly in age.

Unimpacted  areas: Those unharvested  zones of a
  watershed  which are unaffected by a silvicultural
  prescription.

Universal Soil Loss Equation: An equation used for
  evaluating potential soil  loss in  specific  situa-
  tions. A = RKLSPC  wherein  A = average an-
  nual soil loss in tons/acre/year,  R = rainfall fac-
  tor, K =  soil erodibility  factor,  L  = length of
  slope, S = slope gradient, P = conservation prac-
  tice factor, and C  = cropping and management
  factor. (WPG)

Variable  source area: The portion of the  watershed
  that actively contributes to runoff.  These areas
  are dynamic  and  vary  with  antecedent  soil
  moisture, storm size and  duration.

Vegetative change:  Changes  which  include  the
  removal  of vegetative ground  cover,  canopy
  cover,  or a change in vegetative type.

Vegetative cover: The vegetation that is effective in
  protecting the ground surface. May be composed
  of overstory and understory vegetation.

Vegetative ground cover:  The effective vegetation
  and organic matter that  is  protecting the soil;
  this cover includes  litter.

Vegetative shading:   Shading of streams,  water
  bodies, or other areas  of interest by vegetation
  positioned  between the sun and area of interest
   thereby reducing the direct solar radiation strik-
   ing a surface.

 Volatilization: The  evaporation  or changing of a
   substance from liquid to vapor.  (SOIL)

 Volcanic  flow rock: Extrusive  igneous rock  —
   generally the result of a lava flow.

 Volcaniclastic: Fragmental rock of volcanic origin;
   may be a lava  flow breccis, ash flow breccia, air
   fall  ash,  mud flow  (lahar)  breccia,  or  other
   material.

 Washload:  That  portion of  the  suspended load
   which is 0.062  mm or smaller  (silts and clays).

 Washoff:  The flushing of  chemicals  deposited  as
   dryfall or introduced chemicals from the foliage
   during precipitation events.

 Water balance: A measure of continuity of flow of
   water. It  is an accounting of all the inputs and
   outputs of the  hydrologic system. (VTC)

 Water bar: A ridge or mound made across a road or
   cleared strip to divert water to one side. (CEAP)

 Water concentration:  The  condition that results
   when water  is intercepted  and allowed to con-
   verge  instead  of  infiltrating  into  the soil  or
   spreading naturally.

 Water quality objective: A  quantified statement
   that defines the quality of the water resource for
   a specific stream or stream segment. It is related
   to the uses of the water resources and may be in
   terms of existing water quality standards or other
   quantifiable conditions relating to water quality
   such as  degree  of channel  aggradation  or
   degradation.

Water  quality   standard:  Quantitative  or
  qualitative criteria for chemical, physical, and
  biological characteristics that are established for
  the purpose of providing water that is suitable for
  specific uses.

Water resource goal: A broad but concise state-
  ment of the desired  state or condition for the
  water resource.

Water surface slope: The slope or gradient of the
  stream energy grade line. For open channels, it is
  measured as the slope of the water surface and is
  frequently considered parallel to the stream bed.
                                                XH.16

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Waterside  area:  Land  area  of  varying  size and
  shape immediately adjacent to stream courses or
  to water bodies on which the type and/or inten-
  sity  of land use is tempered to meet defined
  water resource  goals.  Terms such as streamside
  management zone, aquatic habitat zone, water
  influence zone,  floodplain, buffer strip, and leave
  or filter  strip are  often used  when referring to
  management direction for waterside areas.

Water yield:  The runoff from  a watershed, in-
  cluding ground water  outflow.  Water yield is the
  precipitation less the evapotranspiration losses
  and  change in  storage.

Water  yield  increases:  Increases  in  water yield
  resulting from reduction in other components of
  the hydrologic  balance — primarily evapotran-
  spiration.
Weak link: A reference to the channel reach that is
  the most unstable either from  an increase in
  streamflow and/or increase in sediment supply.
  Many such weak links  are in a disequilibrium
  condition.

Winching: To hoist or pull with  as if with a winch.

Windbreak: A planting of trees, shrubs, or other
  vegetation, usually perpendicular or nearly so to
  the principal  wind direction,  to  protect soil,
  crops, homesteads, roads, etc.,  against the ef-
  fects of  winds such as wind erosion and the
  drifting of soil and snow. (SSSA)

Yarding: The operation of the initial hauling of
  timber from stump to a collecting point. Pulling
  logs from the tree stump to the skid way, landing,
  or (in rare cases)  the mill.
                                               XII.17

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                                         SOURCES
      KEY TO PUBLISHED SOURCES

AGI:   Gary, M,, R. McAfee, Jr., and C.L. Wolf,
         eds. Glossary of geology. Am. Geol. Inst.

CEAP: U.S. Department of Agriculture, Forest
         Service. 1978 Silvicultural activities and
         non-point pollution abatement: A cost-
         effectiveness  analysis  procedure.
         Prepared  under Interagency  No. EPA-
         IAG-D6-0660  with the Environ. Prot.
         Agency, Athens, Ga.

CLS:   Studier, D. D.,  and V.  W. Binkley. 1974.
         Cable logging systems. U.S. Dep. Agric.,
         For. Serv.

DGT:  American Geological Institute.  1962. Dic-
         tionary of geological terms. Doubleday,
         Garden City,  N.J.

DMM: Thrush, P.  W., ed.  1968. A dictionary of
         mining, mineral and related terms. U. S.
         Dep. Inter.

EM:   U.S. Department of the Interior, Bureau of
         Reclamation.  Earth  manual, 2nd ed.
         U.S. Gov. Print. Off., Washington, D.C.

EPA:   U.S. Environmental Protection  Agency.
         Federal Register Vol 41, No 119, Friday
         June 18, 1976 page 24710 - Preamble to
         parts 124 and 125, Application of Permit
         Program to Silvicultural Activities.

COM:  Huschke, R.  E.,  ed.  1959. Glossary  of
         meteorology.  Am.  Meteorol.  Soc.,
         Boston, Mass.

KPD:  Davis, K. P. 1959. Forest fire: control and
         use. McGraw-Hill, New York.

NIA:   U.S. Fish and Wildlife Service, Office of
         Biological Services. 1976. Nomenclature
         of instream  assessments. West.  Water
         Allocation, Washington, D.C.
PAST: Stimmann, M. W. 1977. Pesticide applica-
         tion and safety training. Div. Agric. Sci.,
         Univ. Calif.

PNE:  Stottenberg, N. L., and J. L. White. 1953.
         Selective loss plant nutrients by erosion.
         Proc.  Soil Sci. Am. 17:406-410.

RHD:  Stein, J., ed. 1973. The Random House dic-
         tionary of the English language. Random
         House, New York.

SAF:   Ford-Robertson, F. C.,  ed.  1971.  Ter-
         minology of forest science, technology,
         practice and  products. Soc. Am. For.,
         Washington, D.C.

SCS:   Soil  Conservation   Society  of  America.
         1976.  Resource  conservation  glossary.
         2nd ed.

SOIL:  U.S. Department of Agriculture. 1957. The
         yearbook of agriculture 1957. House Doc.
         No. 30, Washington, D.C.

SSSA:  Soil  Science  Society  of America. 1975.
         Glossary of soil science terms. Madison,
         Wis.

VTC:  Chow, V. T., ed. 1964. Handbook of applied
         hydrology.  A compendium  of water-
         resources technology. McGraw-Hill, New
         York.

WPG:  Schwarz, C. F., E. C. Thor, and G.  H.
         Eisner.  1976. Wildland  planning  glos-
         sary. U.S. Dep. Agric., For. Serv. Gen.
         Tech. Rep.  PSW-13.  Pac. Southweat
         For.  and  Range  Exp. Stn., Berkeley,
         Calif.

WWU: Veatch, J. 0., and C. R. Humphreys. 1966.
         Water and  water use  terminology.
         Thomas  Printing and Publishing Co.,
         Ltd.,  Kaukauna, Wis.
                                            XH.18

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
  EPA-600/8-80-Q12
                              2.
                                                           3. RECIPIENT'S ACCESSION-NO.
  TITLE AND SUBTITLE
 An Approach  to Water Resources  Evaluation of Non-point
 SiIvicultural  Sources  (A Procedural  Handbook)
                5. REPORT DATE
                 August 1980
                6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Forest  Service
 U.S. Department of Agriculture
 Washington  DC  20250
                10. PROGRAM ELEMENT NO.

                   A28B1A
                11. CONTRACT/GRANT NO.
                  EPA-IAG-D6-0660
 12. SPONSORING AGENCY NAME AND ADDRESS
 Environmental  Research Laboratory—Athens  GA
 Office of  Research and Development
 U.S. Environmental Protection Agency
 Athens   GA  30605
                13. TYPE OF REPORT AND PERIOD COVERED
                  Final . 12/76-12/79
                14. SPONSORING AGENCY CODE
                  EPA/600/01
 15. SUPPLEMENTARY NOTES
 16. ABSTRACT
       This  handbook provides an analysis methodology that can  be  used to describe and
 evaluate changes to the water  resource resulting from non-point si 1vicultural  activi-
 ties.   It covers only the pollutant  generation and transport processes and does not
 consider the  economic, social, and political  aspects of pollution control.
       This  state-of-the-art approach for analysis and prediction  of pollution  from non
 point siIvicultural activities is a  rational  estimation procedure that is most useful
 in making comparative analyses of management  alternatives.  These comparisons  are used
 in selecting  preventive and mitigative controls and require site-specific data for the
 analysi s.
       This  handbook also provides quantitative techniques for  estimating potential
 changes in  streamflow, surface erosion,  soil  mass movement, total  potential  sediment
 discharge,  and  temperature.  Qualitative discussions of the impacts of siIvicultural
 activities  on dissolved oxygen, organic  matter, nutrients, and  introduced chemicals
 are  included.
       A control  section provides a list  of control practices that haye been  used ef-
 fectively and a  methodology for selecting mixtures of these controls for the preven-
 tion and mitigation of water resource impacts.  Such mixtures  are the technical basis
 for  formulating  Best Management Practices.
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
a.
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDED TERMS
                                COS AT I Field/Group
 Non-point pollution
 SiIviculture
 Pollution control
 Water pol1ution
                              68D
18. DISTRIBUTION STATEMENT

 RELEASE TO PUBLIC
   19. SECURITY CLASS /ThisReport)
     UNCLASSIFIED
21. NO. OF PAGES
    861
                                              20. SECURITY CLASS (Thispage)
                                                 UNCLASSIFIED
                                                                         22. PRICE
EPA Form 2220-1 (9-73)
XI I.19
                                                                 f, U.S GOVERNMENT PRINTING OFFICE- 1980-657-165/0081

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