EPA 910/9-76-020
APRIL 1976
FOREST HARVEST, RESIDUE TREATMENT,
REFORESTATION &
PROTECTION OF WATER QUALITY
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION X
12OO Sixth Avenue Seattle .Washington
981O1
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EPA 910/9-76-020
APRIL 1976
FOREST HARVEST, RESIDUE TREATMENT,
REFORESTATION AND PROTECTION OF
WATER QUALITY
PREPARED UNDER CONTRACT BY:
JAMES M. MONTGOMERY, CONSULTING
ENGINEERS, INC.
1301 Vista Avenue, Suite 210
Boise, Idaho 83705
The Project Director was H. Tom Davis,
assisted by C. Fred Hagius. Assistance,
on a subcontracting basis, was provided
by Dr. Benjamin A. Jayne; Mr. Clifford W.
Wylie; Dr. David D. Wooldridge; and
Mr. Roger L. Guernsey.
for
EPA REGION X
This document is available to the public through the
National Technical Information Service, Springfield,
Virginia 22161
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The Environmental Protection Agency, Region X,
has reviewed this report and approved it for
publication. Mention of trade names or commercial
products does not constitute endorsement or
recommendation for use.
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TABLE OF CONTENTS
Page
List of Figures 6
List of Tables 7
CHAPTER I
INTRODUCTION 8
Purpose 8
Scope 9
CHAPTER 2
BACKGROUND INFORMATION 13
Interior Alaska 14
Coastal Alaska IV
Western Olympics 19
Coastal Washington and Oregon 20
Klamath Mountains , 22
Puget-Willamette Trough 25
Western Cascades 27
Eastern Cascades - North 29
Eastern Cascades - South 31
Blue Mountains 32
Okanogan Highlands 34
Northern Idaho 35
Intermountain 37
Regional Fisheries Resources 39
CHAPTER 3
FOREST PRACTICES IN THE PACIFIC NORTHWEST 43
Cutting Practices 43
Thinning 43
Precommercial Thinning 43
Commercial Thinning , 44
Final Harvest , 46
Shelterwood 47
Seed Tree 48
Clearcutting , 48
Selection Cutting 50
Water Quality Implications 50
Regeneration Practices , 53
Reproduction , 53
Site Preparation 55
Water Quality Implications 58
Logging Methods 59
Animal , 59
Tractor ,., 60
Cable 62
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CONTENTS
Page
Aerial 74
Water Qaulity Implications 74
Forest Residues , ,, 79
Management., 79
Water Quality Implications 83
Log Storage and Handling 86
Practices 86
Water Quality Implications 90
CHAPTER 4
IMPACT OF FOREST PRACTICES ON WATER QUALITY 91
Surface Erosion 91
Physiography 91
Silvicultural and Logging Systems 95
Residue Management 103
Reforestation Practices 106
Summary 108
Mass Soil Movement , 109
Physiography 109
Debris Movements , 110
Creeps, Slumps and Earthflows , Ill
Dry Ravel, Dry Creep and Sliding 112
Slope Stability 113
Factors Influencing Shear Strength 116
Factors Influencing Shear Stress 117
Forest Operations 118
Summary 121
Channel Erosion , 123
Suspended Organic Material 124
Dissolved Organic Material , 127
Dissolved Inorganic Material 133
Nutrients 134
Oxygen 139
Thermal Pollution 144
Vegetation 145
Physiography and Hydrology 146
Forest Practices 147
Water Temperature Criteria for Fish 153
Summary 154
CHAPTER 5
PLANNING AND MANAGEMENT 155
Information Requirements 156
Planning 157
Prediction 164
Hydrologic 165
Water Quality 166
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CONTENTS
Page
Erosion Rates and Sediment Yields 166
Meteorology 167
Aquatic or Marine Ecosystems 167
Plant Competition 168
Impact Monitoring 168
Water Temperature 169
Suspended Sediment 170
Dissolved Oxygen 170
Specific Conductance 171
Predicting Effects 171
Background 171
Soil Erosion 17/4
Megahan Erosion Model 175
Water Temperature 177
Peak Flow Accentuation and Channel Erosion 180
Aquatic or Marine Ecosystem Modeling 183
Planning 4. 186
Basic Methodology 188
Basic Information and Analysis 190
Alternative Plan Elements 191
Synthesis 192
Selection 192
Implementation 192
Public Involvement 193
Site Specific Planning 193
Sensitive Areas and Facilities Location 194
Stream Channels 194
Summary , 194
Discussion 196
Stream Banks and Water Influence Environs 198
Summary 198
Discussion 200
Marine, Lake or Reservoir Environments 202
Summary 202
Discussion 204
Steep Slopes and Unstable Soils 206
Summary 207
Silvicultural and Logging Systems Selection 211
Selection 211
Summary 211
Discussion 212
Layout 215
Summary 215
Discussion 217
REFERENCES 222
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LIST OF FIGURES
Figure Page
1 Region X With Subregions 12
2 Crawler Tractor — Ground Skidding Logs ,. 61
3 Crawler Tractor with Integral Arch Skidding Logs , 61
4 High Lead System — Ground Skidding Uphill 63
5 Jammer Ground Skidding Logs Uphill 65
6 Tight Skyline (Single Span) 67
7 Tight Skyline (Multispan) 67
8 Slack Skyline 69
9 Running Skyline 70
10 Mobile-Crane — Grapple-Yarding System 71
11 Balloon Logging Rigging Systems , 72
12 Logging Systems with Optimum Yarding Distances 73
and Slope
13 Helicopter Logging at a Landing in The Boise , 75
National Forest, Idaho
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LIST OF TABLES
Table
1 Effect on Streamf low of Four Forest Practices ........... 98
2 Soil Disturbance From Four Yarding Methods and .......... 99
Clearcutting .
3 Total Understory Vegetation Cover and Exposed ........... 107
Mineral Soil after Clearcutting of Timber
and after Burning of Logging Residue.
4 Factors Contributing To Instability of Earth Slopes ..... 114
5 Douglas-fir Bark Loss During Log Handling Operations .... 128
6 Stand Density Effects on Light Intensity ................ 146
7 Spacing Effect on Light Intensity ....................... 146
8 Ideal and Maximum Temperatures for Fish .... ............. 153
9 Categories and Potential Sources of Information ......... 159
Concerning Forest Management and Water Quality
10 The Land System ......................................... 160
11 System Outline Land Base Portion of Integrated .......... 161
Environmental Inventory
12 R-l Stream Reach Inventory and Channel Stability , . , ..... 184
Evaluation
13 R-l Stream Channel Stability Field Evaluation Form ...... 185
14 Basic Planning Methodology .......... .... ......... .,,..,, 187
15 Relative Erosion Hazard of Logging Areas in Relation , . , , 210
to Site Factors
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CHAPTER 1
INTRODUCTION
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INTRODUCTION
Purpose
The Federal Water Pollution Control Act Amendments of 1972,
PL-92-500, set a national goal of water quality which provides for the
protection and propagation of fish, shellfish, and wildlife and which
provides for recreation in and on the waters. This goal must be achieved
by 1983. The Act mandates that pollution caused by runoff from forest
lands, as well as other nonpoint sources (mining, construction, agri-
culture, etc.), be controlled in addition to the control of point sources
in order to achieve the national goal of water quality.
This report is a state-of-the-art reference on the protection of
water quality in planning and conducting forest harvest, residue treatment,
and regeneration operations based largely on data collected in Region X
(Figure l). It is intended to be an aid for dealing with pollution from
nonpoint sources; and is designed to inform and assist state, federal and
local agencies; industry; and the general public. The report is specifi-
cally intended to assist in the (l) identification of potential hazards to
water quality, and (2) selection of procedures, practices, or methods
suitable for preventing, minimizing, or correcting water pollution problems.
It is also a reference source to other publications, information, and
materials.
The Environmental Protection Agency (EPA) has previously prepared
reports on "Processes, Procedures and Methods to Control Pollution from
Silvicultural Activities," and on "Methods for Identifying and Evaluating
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the Nature and Extent of Non-Point Sources of Pollutants" both published
in October 1973. A third report published in March 1975, by EPA Region X
on "Logging Roads and Protection of Water Quality," deals specifically
with one important aspect of forest practices. The present report builds
on previously published information.
Scope
The report emphasizes summarization of research, currently applied
prediction, prevention and control techniques, and criteria for preventing
or minimizing water pollution.
Subregions have been defined in Chapter 2 in recognition of the
diverse characteristics of the Pacific Northwest. A future goal of water
quality management should be to specify the applicability and relevance
of the available research information and "best preventative techniques"
by subregion. However, there was limited potential for such subregional
specificity in this study due to the lack of information concerning the
geographic applicability of existing research data and techniques.
Chapter 3 summarizes the current forest practices utilized in Region
X. These summaries are brief, but should be sufficient to facilitate a
general understanding of the report.
Chapter 4 addresses the impact on water quality of the various forest
practices presented in Chapter 3.
In Chapter 5 of the report, various methods and approaches to planning
and control are described. Emphasis is placed on providing the reader with
summaries concerning: (l) the selection of silvicultural or logging systems
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based on water quality impact, (2) planning approaches and simulation
models, (3) specific operational, design or planning constraints, and
(4) the information requirements for monitoring, prediction or plan-
ning purposes.
Throughout Region X there are significant potentials for adverse
water quality impact from many facets of timber harvest, residue man-
agement, and regeneration. The most significant of these potential
impacts appears to be related to erosion and sedimentation but in many
areas thermal pollution is a significant potential problem. Nutrients
held by the soil media and vegetation can result in significant water
quality problems but this is generally of less severity than sediment
and elevated water temperature.
There are variations in the applicability of the techniques and
methods presented in this report. This results from the varying sig-
nificance from one subregion to another of physical or biological fac-
tors such as temperature regime, soils/hydrologic characteristics,
geology, fisheries, precipitation pattern and forest types. Users of
the report are urged to review the pertinent references to determine
the relevance of a specific method or technique in their geographic
area of interest.
Significant advances in water quality protection can be made
through planning. Depending upon the complexity and degree of water
quality impact this may involve interdisciplinary input, use of pre-
dictive or impact models, expanded utilization of advanced logging equip-
ment, and guidelines which have been developed for the specific area
of consideration.
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Throughout the region there is a wide range of physical and biological
characteristics. From one operation to another there are widespread
differences in the availability of management expertise, field personnel,
advanced logging equipment, automated analysis technology and field
control. These differences influence the methods by which water quality
goals are achieved and suggest a need for various types and levels of
planning and management.
Detailed site planning and engineering, complemented by adequate field
control, are necessary if the most effective water quality management
programs are to be realized. The most efficient solutions involve
site specific planning along with broader scope subregional (or areawide)
planning and guidelines, impact analysis, and the use of current technology.
When these are not available, general management standards are needed to
ensure compliance with water quality requirements.
This report does not include a glossary due to the large number and
wide range of types of terms involved. The following publications are
recommended to report users who are unfamiliar with the terminology herein.
Society of American Foresters, 1971.
Terminology of Forest Science, Technology, Practice and Products;
(English language version).
USDA Forest Service, 1969.
Glossary of Cable Logging Terms. PNW Forest and Range Expt. Sta.,
Portland, Oregon.
USDA Forest Service, 1973.
Silvicultural systems for the major forest, Agriculture Handbook
No. 445, 114 p.
Franklin, Jerry F., and C. T. Dyrness, 1973.
Natural Vegetation of Oregon and Washington. USDA Forest Serv. PNW
Forest and Range Expt. Sta. Gen. Tech. Rept. PNW-8, 417 p.
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u « WASINGTON
CK.YMPIA /
LEM
/ / /
;' ( OREGON
REGION X
WITHSUBREGIONS
FIGURE 1
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CHAPTER 2
BACKGROUND INFORMATION
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BACKGROUND INFORMATION
This section includes background information on the fisheries and
subregions of Region X. Forest use statistics are not included since
this subject is adequately summarized in "Logging Roads And Protection
Of Water Quality" EPA, Region X March 1975 which complements this
report. The subregional information presented is very brief and intended
only as a conceptual framework for understanding, on a comparative basis,
the variables which affect water quality and the management techniques
selected.
Region X has been subdivided into subregions on the basis of
uniformity of forest type, uniformity of usual silvicultural practices
and similarities in climate, physiography and hydrology. Influence of
a given forest land management practice on water quality varies from
one subregion to another based on these factors and the season.
One major difference concerns the runoff pattern. At lower coastal
elevations most precipitation occurs as rain, which is immediately avail-
able to streams for a hydrologic response and transportation of dissolved
and suspended materials. In contrast, precipitation occurring as snow at
the higher elevations generally accumulates during the winter and is
released as a free water input to streams during the melt season. Thus,
the solvent action of water in passing through the forest soil and
erosive action in streams and rivers is concentrated in the late spring
and early summer.
The discussion of subregions in Region X will identify major forest
species, climate, geologyf and soil parent material where possible. These
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data present a framework for discussion of interacting water quality
problems with forest management, soils erosion and basic hydrology.
Based on the above rationale, Region X has been divided into the
following subregions (see Figure l):
1) Interior Alaska
2) Coastal Alaska
3) Western Olympics
4) Coastal Washington and Oregon
5) Klamath Mountains
6) Puget-Willamette Trough
7) Western Cascades
8) Eastern Cascades - North
9) Eastern Cascades - South
10) Blue Mountains
11) Okanogan Highlands
12) Northern Idaho
13) Intermountain
In most cases, it was impossible in this study to differentiate between
applicable and inapplicable techniques on a subregional basis. However,
the subregions defined present a format that can be used for such purposes
in future studies.
Interior Alaska
The vast area of Interior Alaska has greatly varied topography, vega-
tive cover and climatic conditions. While large in size, there is little
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commercial timber harvest in the subregion. Permafrost is found on
varying aspects and to varying depths. The occurrence and depth to
permafrost greatly influences the vegetative type, vegetative patterns,
and annual growth. In general, it is a dry region; however, permafrost
holds the moisture near the soil surface resulting in a relatively
heavy ground cover of grasses, mosses and shrubs which retard surface
runoff.
The better forest stands are confined to lower slopes and valley
bottoms of larger rivers and their major tributaries. Forest stands
are generally classed commercial in the Interior, if the site is capable
of producing 20 cubic feet of wood per acre per year. The most important
species is white spruce followed by paper birch, quaking aspen, and
balsam poplar. White spruce is generally classed as the climax forest
species on most commercial forest lands of the Interior. The best stands
of white spruce occur on well-drained soils in river bottoms. Mature
stands generally require 100 to 150 years for development. One of the
most common trees is the black spruce, which is considered non-commercial.
The climate of Interior Alaska varies from a moderate continental in
the southern portion near Cook Inlet, to a subarctic climate in the re-
mainder of Interior Alaska. In the transition between coastal and Interior
Alaska (Kenai Peninsula area), mean annual temperatures vary from 32 to
35°F, with the months of June, July and August having average monthly
temperatures in excess of 55°F. Precipitation is relatively uniform,
showing moderate orographic influences. Over a broad area in the Kenai-
Kodiak area, average annual precipitation varies from 30 to <40 inches.
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The climate of Fairbanks might be considered as somewhat of an
average for interior forested areas. The average annual temperature at
Fairbanks is 26°F and can vary locally depending on elevation and aspect
from 15 to 36°F. The official all-time low temperature was -66°F in
January 1934, with the highest temperature recorded 99°F in July 1919.
On the average, the frost free growing season is approximately 90 days.
Average annual precipitation is about 10 inches.
The underlying bedrock of Interior Alaska is predominately Tertiary
sediments with older Jurassic granitic intrusives. Many of the broad
valleys contain very deep alluvial deposits of sand and gravel. Much
of the existing topography is a result of reworked material and deposi-
tions by glaciers.
As is common in association with glacial activity, many of the soils
are windblown loess. These soils occur throughout the interior in de-
positions of a foot to 10 to 15 feet. In many places, the highly erodible
loess soils have been redeposited as alluvial soils in the valleys
through normal erosional processes. Soils of the forest stands have
generally developed on loess or alluvium, in some cases mixed with ash.
The flow regimes of Interior Alaska streams are typical of a cold
snow zone. 40 percent of the annual precipitation usually occurs as snow,
which accumulates and is then released in a melt season from May through
August with augmentation by rainfall in July and August. Over an extended
area of the Interior, the average annual runoff is about 10 inches per
year; however, this can be highly variable depending on annual precipita-
tion and summer temperatures. It is not uncommon to have a two- to three-
fold variation in annual water yield in a very few years.
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Coastal Alaska
Coastal Alaska comprises an area of about 33 million acres of which
15.8 million acres are forested (at least 10 percent stocking with trees).
The forested zone consists of 5.8 million acres of commercial forest land.
Coastal Alaska is made up of hundreds of islands with a narrow
mainland broken by many fjords and inlets. The islands vary in size from
those of less than an acre to islands such as Kodiak with 2.3 million
acres, and Prince of Wales with 1.6 million acres.
Alaska's coastal forests are similar to the temperate coastal rain
forests of Washington and Oregon. The major difference is the absence of
Douglas-fir and an increase in Sitka spruce. In the southeast, near
Ketchikan, forest stands are composed primarily of western hemlock and
Sitka spruce. Interspersed and in occasional small blocks are stands
of western redcedar and Alaska cedar. Commercial hardwoods, such as red
alder and black cottonwood, are confined to stream bottoms and exposed
mineral soil in slide areas. Progressing northwest, western redcedar and
Alaska cedar become much less important. Commercially important stands
of cottonwood occur in the Haines area, and on most alluvial soils to the
west. Sitka spruce becomes an increasingly important species in the
northwest coastal regions.
Land forms of southeast Alaska exhibit the complex effects of
Pleistocene glaciation with great variety of bedrock types including
extensive areas of granitic, metamorphic, volcanic and calcareous rocks.
Granitic rock forms are generally more massive and resistant to the
erosional powers of glaciers; consequently, they form the most extensive
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mountain systems. Calcareous (marble and limestone) bedrocks are exten-
sively fractured providing excellent subsurface drainage.
The great pressure of glacial ice overriding previously deposited
tills formed extensive areas of compacted till. These compacted tills
occur to elevations of about 1,500 feet in many of the U-shaped valleys.
Post glacial, ash and pumice deposits occur over an extensive area
on Revilla, Kruzof, Baranof and Chichagof Islands. Ash and pumice mantle
many sides and upper valley walls, and have been redeposited on terraces
in major river valleys.
The climate of southeast Alaska is wet and cool. Summers are re-
latively cool, and extreme cold weather is uncommon except at higher
elevations. Average annual precipitation near tidewater is about 100
to 150 inches. With relatively small increases in elevation, precipita-
tion ranges to 200 to 300 inches. Rainfall rates are moderate (0.3 to
0.5 inches per hour), and often of long duration. The frost free growing
season varies from about 100 days in northern areas, removed from the
water, to about 200 days at tide water in the southeastern areas.
Coastal Alaska falls within the hydrologic regime of the warm snow
zone. Large amounts of precipitation (20 inches) occur during October
and November, and frequent warm rainstorms occur even after snow accumu-
lation begins in December. The combination of steep slopes and abundant
precipitation with shallow soils, produces streams with highly variable
flow characteristics. Surface runoff varies from 60 to 100 inches for
lower elevation watersheds, to 100 to 150 inches and more for intermediate
and higher elevations.
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Western Olympics
The coastal zone of the Olympic Peninsula combines forest types of
the narrow shoreline Sitka spruce type with the western hemlock type.
Soils and land forms of the Western Olympics, like Coastal Alaska, are
dominated "by Pleistocene glaciation.
Near the ocean, Sitka spruce is the dominant species extending up
river valleys on recent alluvial soils, frequently for many miles. The
western hemlock zone is confined to elevations below 3>000 feet. The
species composition consists of western hemlock, Sitka spruce, western
redcedar, and Douglas-fir. At higher elevations, removed from the
coast, Pacific silver fir becomes an important species. Red alder and
cottonwood occur in commercial stands on recent alluvial soils along
major rivers.
The climate of the Western Olympics is definitely maritime due to
air masses moving inland from the Pacific Ocean. Maximum rainfall
occurs in December and January (15 to 20 inches), with minimum amounts
in July and August (2 to 4 inches). Precipitation averages 70 to 90
inches at low elevations, increasing with elevation and distance inland
to 150 to 170 inches at 1,000 feet, and in excess of 200 inches at
higher elevations. Rainfall intensities are usually moderate (0.4 to
0.6 inches per hour), but may occur for long duration resulting in 5
to 10 inches of rain per day.
The average annual maximum temperature is 58°F at Forks, with an
average annual minimum of 40 F and mean of 49 F. The average frost
free growing season is about 200 days.
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Unusual weather conditions are a frequent occurrence along the Pacific
Coast. Winds of 70 miles per hour occur almost annually, frequently
causing extensive "blowdown of trees.
The central core of the Olympic Peninsula is made up of the very
rugged Olympic Mountains which are surrounded by a glacially reworked,
almost level, lowlands or coastal plain. Bedrock of the Olympics consist
of a volcanic horseshoe-shaped formation extending from Neah Bay east
along the north sides of the Olympics, south along Hood Canal and then
west to just south of Lake Quinault. The main Olympic Mountains are com-
prised of a sedimentary deposit or Tertiary origin.
A large variety of soils have formed from glacial materials with
the type of soil influenced by the degree of compaction, slope and internal
drainage. Alluvial soils of a variety of textures occupy terraces and
valley bottoms adjacent to major rivers.
The hydrologic regimes of the low elevation forest basins of the
Western Olympics, are typical of the rainfall zone with summer lowflow in
rainless periods, and peaks in winter. Average annual runoff varies from
60 inches at lower elevations to 140 for the mid-elevations. Major rivers
flowing from high snowfall zones of the interior Olympic Mountains have
runoff of 160 to over 200 inches per year.
Coastal Washington and Oregon
This subregion essentially drains the western side of the Coast Range.
Valleys are typically water eroded, with very limited glacial activity in
the headwaters of a few higher elevation streams. Vegetation is somewhat
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similar to that of the Western Olympics, with increasing amounts of
Douglas-fir farther south.
In this zone, western hemlock is considered the climax species.
Large areas of the zone, however, are dominated "by second growth and
some old-growth Douglas-fir forests. Much of the subregion has been
logged, or logged and burned, during the past 150 years. Major forest
species are Douglas-fir, western hemlock, western redcedar, grand fir,
Sitka spruce (near the ocean), and western white pine. In Oregon, near
the southern limits of the zone, incense cedar, sugar pine and occasionally
ponderosa pine occur. Near the upper elevational limit of the zone,
Pacific silver fir occurs in mixed stands with western hemlock. Important
hardwoods include red alder and black cottonwood in northern portions
of the zone, with increasing amounts of big-leafed maple, Oregon ash,
madrone, white oak and tan oak in southern Oregon.
The maritime climate of the Pacific Coast prevails throughout this
zone. Annual precipitation averages 60 to 70 inches near sea level in
southern portions of the zonej to 80 to 90 inches in southwest Washington.
Near the crest of the Coast Range, average annual precipitation varies
from 100 to 200 inches, depending largely on elevation, Maximum rainfall
rates are moderate (0.4 to 0.6 inches per hour), with L, to 6 inches per
day total.
Mean annual temperatures range from 53°F near sea level in Oregon
to 50°F in the Grays Harbor area of Washington. Average annual maximum
temperatures range from 6l°F in the south to 59°F in the north, Average
annual low temperatures show about the same spread, with 45 F in the
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south and 42°F at Grays Harbor. The frost free growing season varies
from about 200 days in Grays Harbor to over 300 days in the south.
The Coast Range from the Willapa Hills in the north to Coos Bay
in the south is a complex of volcanics and sedimentary depositions (with
certain interrelated volcanics).
Land forms show the dominating effect of high rainfall from pre-
vailing western winds. Valleys are typically V-shaped with steep side
slopes and active erosional processes.
Many areas have well-drained forest soils which are relatively
heavy-textured, and with a very high surface organic matter content. On
steep mountainside slopes, soils tend to be shallower, with a stony loam
texture.
The hydrologic regime of Coastal Washington and Oregon is very
similar to that of the Western Olympics. Rainfall predominates with
maximum runoff occurring in December and January, the months of highest
amounts of precipitation. Runoff can be highly variable from year to
year. Average annual runoff varies from 4-0 inches to 80 inches in southern
portions of the Coast Range to 120 inches in northwest Oregon, and the
Willapa Hills of southwest Washington. Coastal areas of Washington and
Oregon have very high water yields, with very dynamic river channels.
Klamath Mountains
The Klamath Mountains of southwest Oregon have been separated as a
subregion based on their complex geology and related problems of mass
movement, surface soil erosion and forest regeneration following timber
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harvest. The complexity of the subregion is somewhat indicated by the
annual precipitation patterns, which vary from 100 to 200 inches along
the coast to 20 inches in the interior valleys.
The forest types in the mountainous zones have been termed generally
mixed conifer, which includes Douglas-fir, sugar pine, ponderosa pine
and incense cedar, with a significant component of white fir and grand
fir. On the ocean side of the Coast Range, redwood, Sitka spruce and
western hemlock occur. Their occurence is confined to the mild, humid
climate fronting the ocean, and their distribution becomes very limited
in the interior valleys. These stands contain very high quality trees,
with some of the maximum recorded amounts of biomass per acre.
The Klamath region contains two contrasting climates, The coastal
area is relatively wet, with very little year-round temperature change
and considerable rain during the late fall, winter and early spring.
Average annual precipitation varies from 100 to 200 inches at higher
elevations immediately adjacent to the coast. Rainfall of 75 to 85
inches is common at sea level. The frost free growing season at low
elevations is in excess of 300 days.
The interior valleys of the Umpqua and Rogue Rivers have a signifi-
cantly different climate, as they lie in the rain shadow of the Coast
Range. At lower elevations on the valley floor, average annual precipi-
tation ranges from 20 to 35 inches. There is a gradual increase going
both east and west to the Coast Range and Cascades.
Average monthly temperatures range from 35 to 40°F during the coldest
months to around 70°F in the warmest months.
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Geologically, the Siskiyou Mountains of this subregion are the oldest
formation in Oregon. Terrain is very rugged and deeply dissected. Geo-
logic formations are quite complex, with areas of deposition of volcanic
tuffs and sedimentary rocks which have been subsequently metamorphosed.
Other formations include a variety of granitics, diorites and pyorites.
Soils of the subregion fall into two main groupings. Those of the
western portion are considerably wetter and more humid than those of the
dry eastern condition. Parent materials for these soils include both
sedimentary and igneous rocks. There are also major drainages which contain
a variety of well developed alluvial soils on terraces. Soils of the
eastern portion of the region are often continuously dry for long periods
during the summer, relatively shallow and show less profile development.
Two major rivers (the Umpqua and Rogue) bisect the Coast Range.
Their drainages have characteristics of both the coastal rainfall zone
and the snowpack zone at higher elevations. Smaller streams with their
basins totally within the coastal rainfall zone have peak discharges in
December and January, at times of maximum rainfall. The Rogue River,
gauged at an interior location, shows peak flows from February through
May. Minimum flows occur in September and October. When the Rogue is
gauged near the mouth at Gold Beach, it responds to the pattern of coastal
rainfall, with peak flows occurring in January and minimum flows in
September. Threefold variations in average annual yield are common for
rivers in the Klamath region.
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Puget-Willamette Trough
The general characteristics of the maritime climate and distribution
of plant species are quite similar to the Coast Range, which forms part
of this subregion's western boundary. However, the Coast Range provides
a barrier for movement of air masses, resulting in a marked rain shadow
effect along the eastern slopes of the Coast Range, and in many places
in the valley bottom.
Throughout much of the Puget-Willamette Trough, western hemlock is
considered to be the potential climax species. Currently, much of the
zone has been logged and burned, or converted to agriculture. Douglas-
fir continues to be the dominant species in many of the second growth
stands. Northern portions of the subregion contain mixtures of Douglas-
fir, western hemlock and western white pine, with western redcedar and
Sitka spruce occurring sporadically, and Pacific silver fir at higher
elevations.
Northern portions are strongly influenced by the rain shadow of
the Olympic Mountains. The Dungeness Spit has less than 15 inches of
average annual precipitation. Most of the Puget Sound lowlands average
30 to 40 inches. Similar precipitation patterns occur in the Willamette
Valley, High rainfall (up to 200 inches) on the summit of the Coast
Range decreases very rapidly to lows of 40 to 45 inches in the valley
bottoms. Maximum rainfall rates are moderate, seldom exceeding 0.5
inches per hour and 2 to 4 inches per day.
There is an expected progression in mean temperature from north to
south. Mean annual temperature at Bellingham is 49°F, with the warmest
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months, July and August, averaging 74 F maximum temperature. Coldest
months are January and February, with mean average low temperatures about
30°F.
The current land form and many aspects of the soils reflect the
dominance of Pleistocene glaciation and the effects of flooding and
redeposition of materials.
The Willamette Valley is bordered on the west by a variety of
sedimentary and volcanic rocks of Eocene age, including pillow basalts,
conglomerates, sandstones and siltstones. Less resistant materials have
eroded, forming a series of east-west valleys with resistant formations
forming ridges as extensions of the Coast Range. The western margin of
the Cascade Range is made up of marine sediments. Columbia River basalts
occur on eastern portions of the subregion.
In the Puget Sound area, the soils and landform are dominated by
erosional and depositional activities of the Vashon glaciation. Glacial
deposits have been reworked by rivers, and in some cases till deposits
have been severely compacted.
The extreme variability of soil parent materials of the Puget-
Willamette Trough, combined with the effects of extensive glaciation and
reworking by meltwater, produce a very complex pattern of soils. These
range from very shallow residual soils to deep silty alluvials and
lacustrine deposits in the valley floors. These soils generally have
well developed forest floor layers with varying incorporations of organic
matter.
The peak flows of the smaller streams with their watersheds completely
within the subregion occur in December and January immediately after
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rainfall maximums and runoff varies from 5 to 15 inches per year. River
systems draining the east slope of the Coast Range have average annual
runoff from 4-0 to over 100 inches.
Most major rivers flowing west from the Cascade Mountains integrate
the effects of the rainfall, warm snow and frequently the cold snow
zone. The combined effects of rainfall and the warm snow zone usually
dominate, with peak discharges occurring during December and January,
and with lowest flows in August and September.
Western Cascades
This subregion has many features in common with the Coastal Washing-
ton and Oregon subregion.
The Western Cascades has been classified (Franklin and Dyrness 1973)
as the Pacific silver fir zone. Forest composition varies widely de-
pending on age, stand history and local habitat, usually consisting of
western hemlock, Douglas-fir, western redcedar and varying amounts of
western white pine, Englemann spruce and subalpine species.
The climate of the subregion is wetter and cooler than the adjacent
lowlands with considerably more of the precipitation in the form of
snow. The winter pack usually accumulates in depths of up to 8 to 10
feet at upper elevations and persists from late October until May.
Average annual precipitation ranges from 70 to 90 inches or more with the
maximum occurring in December and January (10 to 13 inches), and mini-
mum amounts in July and August (1 to 2 inches). Maximum rainfall rates
seldom exceed 0.5 inches per hour with daily accumulations of 3 to 5 inches,
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Average annual temperatures of the zone are about 42 F, with average
maximum temperatures in July of 72°F and average minimum temperatures in
January of 22°F. The frost free growing season varies from 120 to 150
days per year.
The subregion could be divided into several units based on origin of
geologic material. From Mt. Rainier south, volcanic rocks predominate.
These are mainly andesite flows with intermixed breccias in Washington
with similar young volcanics and pyroclastics in the Western Cascades of
Oregon. The topography generally exhibits the effects of Pleistocene
glaciation, but land forms are less rugged than those farther north due
to less extensive glaciation. North, along the west slope of the Cascades
from Mt. Rainier, bedrock is frequently much older sedimentary materials
which have been extensively folded and metamorphosed. Granitics occur in
some areas, and major volcanic peaks occur in the southern portions,
Soils are formed from glacial deposits, reworked by rivers and residual
soils. Very shallow soils grade into Lithic soils and wetter locations in-
to Aquic soils. To the south, soils are dominated by ejected volcanic
materials and glacially reworked soil parent material. The central portion
of the Western Cascades in Oregon is predominately pyroclastics. These
include tuffs, breccias and agglomerates. Glaciation and erosion have
resulted in steep slopes and rugged topography. Southeast portions of the
subregion tend to have large amounts of pumice and ash as a soil parent
material.
The hydrology of the Western Cascade subregion matches the regime of
the warm snow pack zone. An early peak discharge frequently occurs in
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December and January coincident with maximum rain in lower elevation
tributaries. Another peak occurs in late March or early April as snow
melts at higher elevations. Annual runoff varies from 30 to 60 inches.
Eastern Cascades - North
Douglas-fir is the dominant and probably climax species in the
more mesic habitats of this zone, giving way to ponderosa pine at lowest
elevations. The forest composition varies widely but generally con-
sists of Douglas-fir mixed with western hemlock, Engelmann spruce and
western redcedar in higher elevation valleys, with extensive areas of
lodgepole pine. In some areas, western larch and ponderosa pine become
significant. Moist stream bottoms frequently contain significant amounts
of grand fir.
The climate of the forest zone varies from the moist subalpine snow
zone at higher elevations to the arid, ponderosa pine/grass type at low
elevations. The Cascade Range forms a barrier to the easterly movement
of moist air from over the Pacific, resulting in greatly reduced annual
precipitation. The combination of the Cascades and Rocky Mountains
forms a trough for north-south movement of air masses, resulting in
seasonally very warm or cold conditions.
Seventy-five percent of the annual precipitation occurs between
late October and early March, During this period, the bulk of the pre-
cipitation occurs as snowfall. Through much of the zone, annual pre-
cipitation averages 25 to 40 inches.
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Extremes in temperature are common throughout the zone, Maximum
summer temperatures are frequently in excess of 100°F, with minimum
temperatures ranging from 10 to 30°F or more below 0°F. Average annual
temperature for much of the zone varies from 45 to 50°F. The growing
season ranges from 130 days in the north to 150 days in the south.
Movement of moist air masses over the Cascades during the summer
frequently result in intense thunderstorms, which can yeild maximum rain-
fall rates of 6 inches per hour for short duration (5 to 10 minutes).
Such storms produce flash floods and mud flows from localized forest drain-
ages, but usually cover a limited area.
The geology of the Eastern Cascades is similar to that of the west
side. Pleistocene uplifting exposed large areas of intruded granitics,
including granodiorite, with metamorphosism of these formations into
gneisses and schists. A large area of Cretaceous sedimentary rocks
(Swauk sandstones) occurs between the acid igneous granodiorite types
(Chelan Batholith) to the north and the basic igneous Columbia River
basalt flows to the south. This formation has been steeply tilted in
places, giving rise to highly erodible soils. Topography of the Columbia
River basalts is considerably more gentle than granitic formations farther
north. Inherently, unstable soils develop from granite and granodiorite
parent materials. Soils formed from Swauk sandstones are also quite
unstable, while soils formed on basalt tend to be more stable.
The Eastern Cascades are predominately in the hydrologic regime of
the cold snow zone. Snow accumulates throughout the winter, to melt during
late spring and early summer. Low flows occur during the coldest portions
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of the winter (January and February). High snow pack zones of the
alpine and subalpine produce 60 to 100 inches of runoff per year. Lower
elevations and watersheds with south exposure tend to produce peak
discharge earlier in the melt season (March and April) as compared with
higher elevations and north-facing slopes. Major floods of this sub-
region occur as a result of delayed melt, with synchronization of melt
from a wide range of elevational zones and heavy, late-spring rainfall
(4 to 6 inches in 36 to 48 hours).
Eastern Cascades - South
The northern portion of the eastern slopes of the Cascades varies
from predominately Douglas-fir/ponderosa pine to a grand fir/Douglas-fir
type. Other species include lodgepole pine and western larch. White
fir and sugar pine occur in southern portions of the zone in Oregon,
with significant amounts of western hemlock and western redcedar in
localized habitats.
The climate of the Eastern Cascades - South is essentially a
continuation of that in the Eastern Cascades - North. Precipitation
averages 60 to 80 inches annually at upper boundaries of the subregion,
with 25 to 30 inches in lower elevations. About two-thirds of this
precipitation occurs in a five-month period between November and March,
mainly as snow.
The mean annual temperatures tend to vary from 45 to 50°F. The
frost free growing season ranges from 90 to 120 days.
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Most of the terrain is relatively gentle, interrupted at intervals
by glaciated river channels. The area is dotted with volcanic peaks and
cones of varying age, size and elevation. Geologically, portions of the
area are very young, with recent lava flows. Locally, glacial deposits
are abundant and major mountain peaks are typically mantled with snow.
Valley walls are frequently quite steep, with depositions of till and
alluvial material in the valleys. Soils of the subregion are generally
quite young and erodible.
The flows of the major rivers draining eastern slopes of the Cascades
parallels that of the cold snow regime, with peak discharges in late May
and minimum flows during the coldest months, January and February. Water
yields vary from 40 to 60 inches at higher elevations to 10 inches or
less near the forest-grass boundary. Over extended areas surface waters
are extremely sparse. The Deschutes River combines the drainage of an
extensive area of the zone in Oregon.
Blue Mountains
This subregion is discontinuous with the balance of the forest zones
of eastern Oregon and Washington in that it is separated by the interior
Columbia Basin of Washington and the high deserts of Oregon.
The Blue Mountains include both the ponderosa pine type and the
grand fir/Douglas-fir type, as defined by Franklin and Dyrness (1973).
Climax ponderosa pine is widely distributed in northeast Oregon and south-
east Washington at the boundary between the sagebrush-grass zone and the
forest zone. The upper limits of the ponderosa pine forest grade into
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Douglas-fir, grand fir and white fir depending on locale. Lodgepole
pine also occurs in association with ponderosa pine/lodgepole pine on
the more mesic sites, while drier sites are occupied by ponderosa pine.
Other mesic sites are frequently occupied by quaking aspen.
The climate of the Blue Mountains is dominated by Pacific maritime
air masses moving eastward. Annual precipitation varies from 12 inches
at lower elevations to about 80 inches at the crest of the Wallowa
Mountains. The major portion of precipitation occurs as snow, with
amounts exceeding 150 inches at higher elevations. The frost free growing
season ranges from 100 to 140 days per year, with temperature extremes
similar to those of the eastern slopes of the Cascades.
The eastern portions of the Blue Mountains span a variety of rock
types. Permian formations consist of schists, limestones, slates, tuff
and chert. Sedimentary formations also occur intermixed, but are
discontinuous due to erosion. Certain portions of the Wallowa Mountains
appear to be extensions of the granitic formations of the highly erodible
Idaho Batholith. Other portions have recent depositions of Miocene
lavas. Widespread glaciation occurred during the Pleistocene, with
typical moraines, deposits and outwashes. Limestone, mudstone and
sandstone of Paleozoic formations occur in the western region, and are
some of the oldest formations in Oregon.
The Blue Mountains have been covered frequently with ash and fine
pumice as aerial deposits. Subsequent erosion has removed much of the
ash from south-facing slopes. Reworking by wind has also been common,
with loess deposits.
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The hydrologic regimes of streams of the Blue Mountains closely
parallel those of the cold snow zone. Snows accumulate during winter
months to be released as snowmelt from March through May. Annual water
production is relatively low, with much of the Blue Mountains yielding
1 to 10 inches per year of runoff. Higher elevation snow packs in the
Wallowa Mountains average 30 to 40 inches of runoff.
Okanogan Highlands
The Okanogan Highlands contain the most extensive area of ponderosa
pine timber type in the state of Washington. Forest types vary from
pure ponderosa pine at lower elevations in mixture with sagebrush and
bitterbrush, to ponderosa pine, grand fir and Douglas-fir mixtures on
gentle north slopes. More mesic sites include significant amounts of
western hemlock and grand fir. Lodgepole pine frequently occurs in
extensive pure stands following fire. Ground cover of pine grass and
elk sedge are common.
Precipitation is relatively consistent throughout each month of the
year, with the driest months of July and August receiving about half the
rain (l inch) of the amount received in the wettest months of December
and January (2.1 inches). Many areas have more growing season rainfall
than areas in the Eastern Cascades subregion with 70 to 90 inches of
annual precipitation. This growing season rainfall is able to sustain
good forest growth in 10 to 20 inches of average annual precipitation.
Temperatures of the Okanogan Highlands are very similar to those of
the Eastern Cascades - North. Mean annual temperatures vary from 50°F at
Grand Coulee Dam to 47 F at Laurier. The frost free growing season varies
from 100 to 128 days per year.
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Land form is in considerable contrast to many other subregions of
the northwest. Glacial drift and reworked deposits are found throughout
the area. Bedrock geology is complex with rocks of the Palezoic forma-
tion including quartzite, graywacke, slate, greenstone and some limestone.
Granitic rocks of the Mesozoic are abundant, including some granitics and
granodiorite. Limited areas of Tertiary deposition occur adjacent to
major river valleys, including andesite and basalt.
Soils are equally complex in that recent deposits of ash have been
reworked through erosion, providing a host of soil parent materials of
widely varying textures. Soil erosion potential is relatively low as
topography is usually gentle. Soils are noncohesive, however, and quite
erosive, so disturbance of vegetation on the steeper slopes can result
in significant soil movement from both high intensity rainstorms and
snowmelt.
The subregion is relatively arid with much of the areas receiving
less than 20 inches of annual precipitation. Low precipitation plus
very pervious soils results in a very low density stream network. Annual
runoff ranges from zero to about 10 inches, with the bulk of the area
averaging 5 inches.
Northern Idaho
There is a progression of forest types from lower elevations on the
west to higher elevations in the mountain ranges bordering the subregion
in the east. Ponderosa pine intermixes with Douglas-fir and lodgepole
pine at lower elevations. With increasing elevation and annual
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precipitation, western larch, western white pine, grand fir, Engelmann
spruce and subalpine fir become important. Interior western hemlock and
western redcedar sometimes form climax stands.
The climate of the Northern Idaho subregion is typical of that of
the cold snow hydrologic regime. Annual precipitation varies from 15
inches at lower elevations at the boundary of the commercial forest to
50 inches near the summit of the Selkirk and Bitterroot Mountain Ranges.
The driest months are usually July and August, with the wettest period
usually in December and January. About 70 percent of the annual precipi-
tation occurs during the snow accumulation season of October through March.
Warmest areas are at the lower boundary (near Spokane) where mean
annual temperatures are approximately 4-8 F. At the higher elevations,
there are significant decreases in temperature. At Mullen Pass (6,000
feet), mean annual temperature is 37°F, ranging from a monthly maximum
temperature of 69 F in July to a minimum of 14 F in January. The frost
free growing season varies from less than 90 days at higher elevations to
150 days at lower elevations in the ponderosa pine zone.
Northern portions of the subregion show the dominating influence of
Pleistocene glaciation, with rolling topography and deep glacial deposits.
Glacial erosion intermixed with Tertiary lava flows leave a complex of
deep lake deposits with exposed basalt. Erosion of the Kaniksu Batholith
formed the Selkirk Mountains. An extensive area of Columbia River basalts
occurs in the vicinity of Lake Coeur d'Alene. These flows overlay the
Precambrian sedimentary rocks which form the Bitterroot Range. Considerable
metamorphism occurred where the basalts contact the northern boundary of
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the Idaho Batholith.
Lithic soils occur on eroded granitic materials of the Kaniksu
Batholith. The young Columbia River basalts also have an eroded phase
which classes as Lithic soils or undeveloped soils. The effects of
glaciation have generally removed the weathered granitic surface materials.
Formations of Northern Idaho are highly erosive, particularly those
farther south in the Idaho Batholith. Extreme care must also be taken
on the Palouse loess soils, which occur in the western portion of the
timbered zone.
The major drainages include the Spokane River (including the Coeur
d'Alene and St. Joe), the Clearwater, and portions of the Salmon, Kootenai
and Clark Fork of the Flathead. Average annual runoff varies from less
than 10 inches at lower elevations in the ponderosa pine zone to about
40 inches at highest elevations in the Selkirk-Bitterroot Mountains.
Intermountain
Glaciation effects in the Intermountain subregion are limited to
higher elevations where alpine glaciers locally affected the soils and
topography. Parent materials of much of the area are Precambrian,
metamorphics and other intrusives. Precambrian sedimentary rocks also
occur in a complex intermixture.
Forest types are typical of the ponderosa pine/Rocky Mountain
Douglas-fir forests which cover much of northeast Washington, Idaho and
Montana. Ponderosa pine is dominant and climaxes at lower elevations in
mixtures with Douglas-fir. With increasing elevation and more humid
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conditions, western larch, Engelmann spruce and lodgepole pine make up
significant components of the forest stand. Localized in humid river
bottoms, grand fir is also an important species.
The forest zone occupies a precipitation range from 15 inches at
lower elevations to 50 inches of annual precipitation at higher elevations
in the Salmon River Mountains. Maximum precipitation occurs in November
through February. Snowfall accumulates to maximums of 100 to 200 inches
at higher elevations in the mountains.
Temperatures show the expected inverse relationship with elevation
for mean annual, highs and lows. The frost free growing season ranges
from 140 days at lower elevations to less than 90 days at the upper
limits.
The Intermountain subregion is the location of the Idaho Batholith,
a Cretaceous granitic intrusive that has weathered in place for the last
70 to 90 million years. It is an extremely large outcrop covering over
14 thousand square miles. While uniform in its origin, it contains a
host of grain and crystal sizes in various areas. Most grain sizes are
relatively large, weathering to a. very coarse-textured soil. The soil
texture in combination with relatively steep topography has resulted in
one of the most erosive geologic formations in the western United States.
The eastern boundary of the Intermountain subregion in Idaho is
formed by the Beaverhead, Lemhi and Lost River Ranges. These ranges
are Precambrian and Paleozoic sedimentary rocks. Older rocks of the
Precambrian include slates and mudstones, while rocks of the Paleozoic
are predominately limestones and dolomites.
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Soils of the Intermountain zone are highly erosive. In areas
of gentle topography, forest floor layer can build up sufficiently to
initiate processes of soil formation. In general, erosion and limited
accumulations of forest floor material have resulted in extensive areas
of immature soils.
The hydrologic regime of the Intermountain subregion closely
parallels the cold snow zone. Snow packs accumulate throughout the
winter, to be released as snowmelt with peak flows occurring in late
May. South exposures and lower elevations melt in late March and
April with higher elevations and north exposures melting later.
Average annual runoff varies from insignificant amounts at lower ele-
vations in the ponderosa pine zone to maximums of <40 inches in the
higher mountain ranges of the Bitterroot-Beaverhead.
Regional Fisheries Resources
Commercial and sports fisheries resources of Region X are dependent
on aquatic and estuarine habitats within, or affected by, the commercial
forest zones for reproduction and rearing. The more important species
utilizing these environments are: pink (humpback) salmon, chum (dog)
salmon, sockeye (red) salmon, Chinook (king) salmon, coho (silver)
salmon, rainbow and steelhead trout, cutthroat trout, and Dolly Varden
(char). The spawning habitats of reproducing species consists of suit-
able gravel with a continuous supply of high-quality water with a highly
dissolved oxygen content. Spawning beds must be protected from physical
damage by floating debris or depositions of sediment while eggs, or
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alevins (recently hatched fish), are in the gravel, The quality of the
aquatic environment is also very important year round for the rearing and
growth of juvenile fish.
While the life cycle habits of many of the species have certain
aspects in common, there are sufficient differences in their use of the
freshwater environment that a distinction should be made between certain
species. Pink and chum salmon utilize freshwater only, for spawning
and egg incubation. These species typically spawn low in streams very
close to salt water in summer and autumn, with fry emerging from stream
bed gravels in spring. Fry may migrate to salt water immediately, or
remain in the stream for a very short time. The life cycle in the ocean
requires one-and-a-half to four-and-a-half years, then adults return to
their streams of origin to spawn. Pink and chum salmon are important
throughout coastal Alaska, Puget Sound and in streams of Washington and
Oregon.
Sockeye salmon generally require a lake in the river system used for
reproduction. Adults move upstream to the lake and into the tributaries
where they spawn. The emerging fry then migrate to the lake where they
spend one or more years as residents. On reaching migratory size,
juvenile sockeye salmon migrate to the ocean in the spring of the year
where they feed and grow to mature adults, usually after one-and-a-half
to three-and-a-half years. The very red flesh of the sockeye salmon makes
it one of the most prized commercial species. It is still a particularly
important species in Washington and Alaska and was once important in the
Columbia River system, but has now declined significantly there due to
habitat changes.
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Chinook and coho salmon and steelhead trout utilize rivers
throughout coastal Alaska, Washington, Oregon, Idaho and northern
California. Chinook salmon are the largest of the Pacific salmon, and
generally favor larger river systems. There are runs in most of the
large rivers from the Yukon south to San Francisco Bay. Three races
of Chinook salmon are commonly recognized based on the time of entry
into fresh water (spring, summer or fall). Spring Chinooks enter these
streams as early as March and April, while later runs peak in mid-July.
A fall run enters the streams from September into December. Coho
salmon have a much wider range of suitable stream habitats as they will
enter both large and small streams for spawning. Coho and most Chinook
juveniles spend one or more years in fresh water before reaching
migratory size, and returning to the ocean (certain races of Chinook
emigrate to sea after only three months), They will then spend one or
more years in the ocean completing their life cycle to return to spawn
in fresh water.
Rainbow trout (steelhead) and cutthroat trout also have similar
life cycles, entering fresh water from the ocean to spawn, with juveniles
spending differing times in the fresh water. The primary difference
between trout and salmon in life cycle, is that trout do not necessarily
die after spawning and may return to spawn in fresh water several times.
Most major water bodies in Region X either have natural populations
of fish that are important for sport or commercial use or have introduced
species. Physical barriers have caused natural landlocking of both the
salmon and trout in particular river systems. Landlocked sockeye
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salmon (kokanee) are important in many of the larger lakes tributary
to the Columbia River.
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CHAPTERS
FOREST PRACTICES IN
THE PACIFIC NORTHWEST
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FOREST PRACTICES IN THE PACIFIC NORTHWEST
Cutting Practices
THINNING
Cuttings which are made in immature stands to stimulate growth of
the remaining trees in order to increase the total wood yield are termed
thinnings (Smith 1962). Although many types of thinning are recognized
in the practice of silviculture, in general two types of thinning receive
the greatest use in the Pacific Northwest: precommercial thinning and
commercial thinning. Precommercial thinning is most effectively applied
as a single thinning when trees are small - perhaps 10 to 15 feet in
height (Carter et_ al_ 1973). Commercial thinning, on the other hand,
is practiced on older stands for which the thinned trees have marketable
value as pulpwood, poles or sawlogs.
Precommercial Thinning
The "basic objective of precommercial thinning is to increase
merchantable yields by concentrating productivity of the site into
fewer stems per acre (Miller 1971, Carter et_ al_ 1973). Although the
principal objective of precommercial thinning is such stocking control,
thinning is also valuable for the control of mortality due to insects
and disease (Nelson 1971). Precommercial thinning is accomplished
either with chemicals or by mechanical methods, primarily power saws.
One of the problems associated with precommercial thinning is the
treatment of slash. It is reported that perhaps one-fifth of the cost
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of precommercial thinning on the National Forests of Region 6 is
attributable to slash disposal requirements (Robertson 1971). The
quantity of slash generated during precommercial thinning is highly
correlated with the age of the stand; i.e., the larger the trees, the
larger the amounts of slash (Donald 1975).
Commercial Thinning
Commercial thinning in the Pacific Northwest is practiced in the
management of a number of the more valuable species, including Douglas-
fir (Reuhema and Pinaar 1973), western hemlock (Molmberg 1965), and
ponderosa pine (Barrett 1968). The objective of commercial thinning
in these stands is to provide more desirable tree spacing and to con-
centrate growth on the remaining trees as a means of increasing the
total yield of wood. The age at which stands are thinned is determined
both by tree growth rate and market demand for specific types of wood
products.
Many foresters feel that dense stands which will respond to thinning
on poorer sites should receive primary emphasis for thinning (Barrett
1968). Others prefer to concentrate on stands that will respond the
most quickly to treatment.
In contrast to precommercial thinning, commercial thinning requires
entry into stands with logging equipment for removal of felled trees.
Both cable systems and tractors are used in the Pacific Northwest. The
soil disturbance which occurs can result in surface erosion and thereby
impact water quality. In addition slash produced during commercial
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thinning, if not treated properly, can adversely affect water quality.
The effect of commercial thinning is nearly always to improve
the general quality of a stand. Rates of growth in diameter and height,
primarily the former, usually increase. Because the less vigorous
trees are customarily cut during thinning, future stand mortality is
reduced (Smith 1962). Consequently, the quantity of defective material
in the stand at final harvest is lowered and reduced quantities of
slash can be expected. This tends to reduce somewhat the slash manage-
ment problems at final harvest and, consequently, to lessen the water
quality impact.
Both crawler and wheel tractors are used for thinning throughout
the region and in general are restricted to topography of moderate
slope (less than 35 percent). The use of tractors requires the con-
struction of skid roads as well as landings. The resultant exposure of
mineral soil and soil compaction (as will be discussed in Chapter 4)
can contribute to soil erosion problems.
Smith (1962) has pointed out that thinning increases the runoff
of forested watersheds mainly by the temporary opening of the crown
canopy, which causes a reduction of interruption of precipitation. More
water reaches the soil and less is lost by direct evaporation. Goodell
(1952) found that the yield of water might be increased by 15 to 20
percent as a result of heavy thinnings in young lodgepole pine standvS.
This could well increase erosion, but site-specific data is not avail-
able to demonstrate the runoff/erosion impacts of thinning.
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Commercial thinning of stands located on steep slopes and therefore
unsuitable for tractor operation would be best accomplished with either
aerial or cable logging systems. However, high costs and low production
preclude the use of aerial systems for thinning. Although several
cable systems can be used for commercial thinning, skyline systems
equipped with a carriage capable of lateral yarding to the skyline
offers several distinct advantages (Binkley and Williamson 1966). Logs
were yarded laterally to the skyline and longitudinally with one end in
contact with the ground. The extent of soil disturbance engendered should
be less with this system than that caused by tractor logging.
Burke (1975) has pointed out that a running skyline equipped with
a slackpulling carriage with a lateral yarding capability of 150 feet can
be used for partial cuts. Aulrich e_t_ al_ (1974) compared tractor and
skyline logging for thinning young Douglas-fir stands. Although no
soil compaction was found in skyline units, increases in soil density
were detected in tractor units. (Tractor logging also left less slash
and therefore less potential for organic leachates. ) Because tractor
logging left less slash, a reduction in water quality impact resulting
from slash would be expected.
FINAL HARVEST
In general, four silvicultural systems have been used for the manage-
ment of coniferous forests in North America: shelterwood, seed tree,
clearcutting, and selection. The selection method leads to uneven-aged
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stands, whereas even-aged stands result from use of the clearcutting,
seed tree and shelterwood methods.
Of the four silvicultural systems in use, clearcutting and selection
cutting are used predominately in the Pacific Northwest. Clearcutting
prevails on the west slope of the Cascades, throughout the mixed conifer
stands of eastern Washington and Oregon, and in the white pine stands of
northern Idaho. Selection cutting is used primarily for the harvest of
ponderosa pine. There are exceptions to this general pattern; however,
Williamson (1973) has reported limited success with shelterwood cutting
of Douglas-fir at the higher elevations in western Oregon. Also, partial
cutting of old-growth lodgepole pine stands is successful under some
circumstances (Alexander 1972). Williamson (1966) has suggested that
adequate regeneration of well-stocked stands of western hemlock can be
assured under any one of a broad range of shelterwood densities.
Shelterwood
The shelterwood system requires the removal of the stand in a
series of cuts. Although some natural regeneration normally occurs
under the cover of a partial forest, it is common practice to artifically
regenerate shelterwood cuts. This system is especially well adapted to
species or sites where protective cover is needed, usually for repro-
duction purposes, or where the shelterwood gives the regeneration an
advantage over undesirable competing vegetation. Shelterwood cutting
is sometimes used for special aesthetic management purposes (for example,
in or near campgrounds).
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Seed Tree
The seed tree method requires the removal of nearly all the timber
of an area, usually in one cut. Consequently, the impact on the site
is not unlike that of the clearcutting method. Specially selected,
vigorous, wind-firm trees of the desired species are left scattered over
the area to provide a natural source of seed (USFS 1973). The very
nature of the method requires that it be applied only to species whose
seed is wind disseminated (Smith 1962). Because the size and frequency
of seed crops are difficult to predict for many species, the seed tree
method has not proven to be particularly satisfactory for obtaining
stand regeneration. The seed tree method has limited applicability in
regenerating coastal Douglas-fir because of the high risk of wind damage
(Smith 1972).
Clearcutting
Clearcutting involves the complete removal of the timber stand over
a given area in a single cut. This system requires the use of intensive
management practices, including erosion control, in site preparation and
regeneration of the new forest. Regeneration can be achieved through
natural seeding. However, the larger clearcuts frequently must be re-
generated artificially to avoid extended periods of exposed soil surface
(USFS 1973). Hand planting of nursery stock is considered to be the
most reliable method for regeneration.
Clearcuts range in size from a few to several hundred acres. The
areas range in shape from small nearly square patches (sometimes called
-------
"patch cuts") to long narrow strips sometimes parallel but more often
perpendicular to the contour. Clearcutting in alternate strips is
sometimes practiced (Smith 1962). Recently, attempts have been made
to blend clearcuts with natural openings in the forest, including
avalanche zones at the higher elevations (USFS 1974).
Clearcutting is one of the most economic harvest methods from the
standpoint of timber marketing, since it permits intensive use of
both labor and equipment over a short time period. Clearcuts can be
yarded with any logging system, although cable systems are perhaps
used more extensively, particularly in western Oregon and Washington.
A wide range of mechanical equipment for preparation of the cutover
site for either seeding or planting is available. For the most part,
equipment for site preparation is restricted to use on moderate and
gentle slopes. Theoretically, areas suitable for Clearcutting can be
harvested and regenerated in a relatively short period of time.
Clearcutting is particularly appropriate for old-growth stands as
well as for disease- and insect-infested stands. Large quantities of
slash frequently accumulate from Clearcutting old-growth stands as well
as from stands characterized by a high degree of mortality. Treatment
of the slash is essential in order to avoid water quality damage as
well as to reduce the fire hazard and minimize insect infestations.
Because practically all of the vegetation is removed from an area
during Clearcutting, the site is exposed to more intense levels of
radiation than previously, and site desiccation (rapid losses of soil
moisture) is sometimes a problem. A minimum cover of vegetation remains
49
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to receive and disperse rainfall. The area is also more subject to wind
action and the timber in adjacent areas is more subject to windthrow. Re-
gardless of the species involved, site regeneration can be a problem,
particularly at higher elevations on south- and west-facing slopes.
Selection Cutting
Selection cutting in the Pacific Northwest is practiced largely in
the ponderosa pine stands located primarily in eastern Washington, but also
in Oregon and Idaho. In general, two variations of the system are practiced:
(l) single tree selection and (2) group selection. Single tree selection
leads to an increase in the proportion of shade-tolerant species. Group
selection, on the other hand, tends to maintain a higher proportion of the
less shade-tolerant species. For the management of ponderosa pine forests,
however, several modifications of the selection method have been developed,
including maturity-selection, improvement-selection, sanitation-salvage, and
unit control area. Smith (1962) summarizes the various forms of selection
cutting as follows:
"The maturity-selection method is aimed mainly at making
best use of the growing stock in a rather passive manner:
improvement-selection at the active upgrading of the stock;
sanitation salvage, at overcoming catastrophic losses; and
unit area control, not only at reproducing stands but also at
establishing an efficient arrangement for future management."
WATER QUALITY IMPLICATIONS
The water quality impacts of precommercial thinning are, for the most
part, indirect and minimal. Since precommercial thinning is usually
50
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accomplished manually, site disturbance is almost nonexistent. However,
small quantities of slash are produced which introduce a fire hazard
and also may harbor insects. Increased insect populations can lead to
increases in stand mortality and can thereby add to the fire hazard. As
will be emphasized later, fire exposes the soil surface and leads to
increased rates of erosion; therefore, adequate slash treatments following
precommercial thinning are necessary. The precommercial thinning of older
stands will, in general, produce larger quantities of slash, thereby
increasing the need for treatment.
Commercial thinning, in contrast, requires the use of tractors or
cable logging systems for removal of felled trees. Furthermore, sub-
stantial quantities of slash can be generated. Normally, however, slash
volumes are expected to be somewhat lower than that of final harvest.
The extent of site disturbance brought about by commercial thinning
should, in general, be less than that of final harvest, since lower
volumes of material are being removed. Nonetheless, mineral soil will
be exposed and the amount of precipitation which reaches the ground
will be increased. Consequently, the probability of an undesirable
amount of erosion can be expected to increase. However, under normal
circumstances and with adequate precautions, the remaining stand and
associated understory should limit the resulting surface erosion. The
evidence available suggests that tractor logging is more destructive
to the site than cable logging with the difference accentuated on
steeper sites.
Although the shelterwood method offers many water quality advantages,
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It also has disadvantages. There is no practical way to use the shelterwood
system in many old-growth stands or in stands where mistletoe is a problem.
Damage to the newly-established stand is almost unavoidable during the
final removal cut, particularly in old-growth timber on steep slopes. Slash
management is more difficult because of the need to protect the residual
stand. Perhaps most important from the standpoint of water quality, however,
is that several entries into the stand are required. Consequently, the site
is disturbed on a number of occasions and the period of surface erosion risk
is extended.
The impact of clearcutting (including seed tree) on water quality is
associated primarily with: (l) site exposure and soil disturbance, and
(2) the presence of large quantities of forest residue.
Some soil disturbance occurs with all types of harvesting equipment
used on clearcuts. Current evidence, however, suggests that tractor
logging is more disruptive than cable logging (see Chapter 4). The
added exposure of the site to the extremes of climate brought about by
clearcutting can result in accelerated surface erosion if adequate
measures for site protection are not taken ( Smith 1962). Because large
quantities of residue are usually generated by clearcutting, particularly
of old-growth stands, debris can accumulate in ravines and streams. An
increase of organic materials in the runoff water and the failure of
debris dams which may lead to stream scouring can result.
The impact of selection cutting on water quality is associated with
site disturbance and, to a much lesser extent, with forest residues.
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Because of the low quantities of slash normally produced during selection
cutting, particularly on low-volume ponderosa pine stands, residues are
rarely a problem insofar as water quality is concerned. Soil disturbance,
however, can be more of a problem. Selection cutting requires entry
into the stand more frequently than clearcutting. Cable logging systems
including jammers as well as both crawler and wheel tractors are used in
selection cuttings of ponderosa pine. As a consequence, soil disturbance
and soil compaction can be a problem, praticularly on steep sites and
erodible soils.
Regeneration Practices
REPRODUCTION
Artificial reproduction is obtained either by planting young trees
or by applying seed, sometimes called "direct seeding." Natural
regeneration of coniferous forests is obtained from seedlings which
originate by natural seeding. In the Pacific Northwest artificial
regeneration is practiced much more extensively than natural regeneration.
The regeneration of stands in southeastern Alaska, on the other hand,
is more dependent on natural seeding (Harris 1967).
Direct seeding offers many advantages such as lower cost, fewer
organizational problems, and the possibility of seeding over longer
periods of the year than planting (Smith 1962). Although labor and
equipment are costly, the probability of survival is much better with
planting than with seeding. Consequently, planting is practiced much
more widely than direct seeding today in the Pacific Northwest and is
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considered to be the surest method for obtaining regeneration.
Natural regeneration following harvesting requires a source of viable
seed. The size of the cutover area, topography, prevailing wind direction
and many other factors have a significant bearing on the success of natural
regeneration of clearcut areas (Harris 1967). Partial cuts such as
selection cutting, offer marked contrast to clearcuts in that provision
is made for a seed source in the immediate vicinity of the harvest area.
Leaving a natural seed source on harvested areas, however, does not
guarantee successful regeneration and/or stocking.
Seedbed preparation for natural regeneration is often accomplished
as a result of logging and slash disposal. However, in many instances
deliberately-planned additional site preparation work is also needed.
The resulting soil disturbance and possible soil compaction from the use
of heavy equipment on the site can have adverse water quality effects.
Some species will regenerate rapidly on cutover areas if the site
conditions are at all conducive to their reestablishment. For example,
provided that all critical environmental factors are favorable, Douglas-
fir will regenerate naturally on many sites in the Pacific Northwest. On
the other hand, natural reestablishment of Douglas-fir is difficult on
many sites. Given the proper circumstances, ponderosa pine will regenerate
naturally in many parts of its natural range. Nonetheless, there are
many situations, particularly on drier, less fertile sites that are
subject to extremes of temperature and radiation on which natural regener-
ation is difficult if not impossible to obtain.
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Planting stock is grown in nurseries, with transplanting one or
two years after seeding, depending on the species. Field planting is
nearly always a hand operation, using either bars or mattock-type tools.
Under certain conditions the power auger prepares satisfactory planting
holes, speeds the planting operation and improves planting quality. In
areas of gentle slope or where steeper slopes have been terraced, machine
planting is sometimes practiced (Adams 1969). Both containerized
seedlings and bare-rooted stock are used.
SITE PREPARATION
Both planting and direct seeding nearly always require some form of
site preparation beforehand, including slash treatments and disturbance
of mineral soil. As will be described in the section on Residue
Management, slash burning is practiced throughout the region. Burning
of slash exposes the soil, reduces the organic matter content and can
thereby lead to increased rates of surface erosion. Lopping and
scattering of slash and crushing in place are sometimes used and re-
portedly offer advantages in terms of seedling survival (Cochran 1973).
The regeneration of old brush fields may require the use of herbicides
and fire as a first step in site preparation. The conversion of brush
lands as well as lands occupied by inferior species has been, and will
continue for some time to be, a major management activity of significance
to water quality in the Pacific Northwest.
Following slash treatment or removal of competing vegetation, some
form of site disturbance is sometimes necessary to expose the mineral
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soil needed for direct seeding as well as for planting. Partial or
complete removal of the layer of duff and litter is involved. On
cut-over areas the disturbance brought about by the movement of logging
equipment over the area is frequently sufficient. However, additional
measures are sometimes needed to expose mineral soil, whether planting
or artificial seeding is used (Adams 1969; Schultz and Biswell 1959;
Foiler and Curtis 1973; Smith 1962).
In recent years, new mechanical methods of site preparation have
been developed and old ones greatly refined. All sizes of tractors with
various attachments, as well as specially-designed machinery prepare
planting sites more efficiently and economically than was previously
possible. Several years ago, Curtis (1964) itemized the kinds of
disturbance that site preparing equipment can inflict on the ground or
vegetation. The list is imposing and includes disking, furrowing,
stripping, ripping, punching, slitting, dragging, chopping, tilling,
churning, logging, and crushing. In addition, the list could have
included plowing, scalping and terracing. During the last 10 years,
most mechanical site preparation has involved scarification, stripping,
or terracing.
Machine scarification is usually accomplished with a crawler tractor
equipped with a toothed brush blade. The objective of scarification is
to eliminate obstacles to planting such as heavy brush, slash and old
stumps. An intermixing of litter and duff with mineral soil takes place
such that soil adequate for regeneration is exposed. The litter and
duff act to some extent as a mulch for retention of water and slow
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release of nutrients. If the volumes are excessive, windrowing of
brush and residue may be essential. Burning of the windrowed material
before planting allows additional planting space for seedlings, removes
habitat for rodents, pests and insects, and minimizes the fire hazard
for newly-established stands.
Dishpanning, a form of scarification, is accomplished with machine,
usually a crawler tractor equipped with a blade. The "vegetation is
removed from a relatively small area a few feet in diameter preparatory
to direct seeding or planting.
Hand scarification of a small area, approximately three feet in
diameter is frequently practiced by crews before planting seedlings.
Highly localized disturbance of this nature removes plant competition in
the immediate vicinity of the seedling and also reduces soil moisture
losses. Hand scarified spots are sometimes sloped from the edges to
the center in order to trap and retain moisture.
Stripping is the removal of long strips of competing vegetation on
narrow contour benches, incised across slopes by small tractors. These
strips are usually too narrow to accommodate a planting machine, so
hand planting is necessary. Contour strips are kept narrow to limit
or control disturbance of the soil mantle and interruption of ground-
water movement.
Terracing involves a more complete clearing of competing vegetation
than stripping and is accomplished by constructing large contour benches
that are commonly the width of a tractor. Packer (1971) reports that
little erosion has resulted from terracing since its first use in
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southern Idaho. A U. S. Forest Service task force appraisal (1969-1970)
on the Bitterroot National Forest found few signs of serious erosion on
most of the terraced slopes but cautioned that long-run erosion could
not be determined.
WATER QUALITY IMPLICATIONS
The burning of residues left after harvesting or of brush from old
fields being prepared for planting can indirectly affect water quality.
A number of researchers including Dyrness and Youngberg (1957) and
Tarrant (1956) have reported that slash burning modifies soil properties
in highly localized areas where burning is particularly intense. These
areas, which usually occupy a relatively small part of a controlled burn,
exhibit changes in soil structure, decreases in wettability, and loss
of nutrients. Such occurrences have little overall impact on water
quality when the area involved is minimized. However, large areas in
which burning is intense could increase runoff, erosion and the nutrient
loss to streams.
The exposure of mineral soil preparatory to seeding and planting
has far greater potential for impacting water quality than burning. As
is discussed in other portions of this report, exposed mineral soil can
be eroded rapidly. Furthermore, dishpanning, scarification, stripping,
terracing, and plowing all require the travel of heavy equipment over the
site. Soil exposure and compaction can take place and intensify erosion
processes. Sites at higher elevations, soils that are derived from
igneous rock, and soils on steep slopes are particularly vulnerable.
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Site preparation methods that reduce soil disturbance to a minimum
commensurate with obtaining stand regeneration and which also minimize
the use of heavy equipment on the site are preferable from a water
quality standpoint.
Logging Methods
In the Pacific Northwest systems used for the movement of logs
from the stump (point of felling) to a landing (point of concentration)
can be classified as one of three major types: tractor, cable and
aerial. Animal skidding is a fourth, but minor type. Tractor skidding
is accomplished with either crawler or wheel type units, both of which
are frequently equipped with auxiliary devices for reducing the extent
of contact between log and ground (Pearce and Stenzel 1972). Cable
logging, of which there are many forms, is a yarding system employing
winches in a fixed position (USFS 1969). Aerial logging, a recent
development in the logging industry, is accomplished with heavy-duty
and medium-duty helicopters.
ANIMAL
At one time, skidding was accomplished entirely with animals,
primarily mules, horses and oxen. Animals are still used but on a much
restricted basis, primarily in the northeastern and southeastern parts
of the United States, in Canada in situations where log sizes are small,
and occasionally in the northern Idaho subregion on small private
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woodlots. Moderate slopes with favorable grade are essential. Maximum
skidding distance rarely exceeds a few hundred feet and, consequently, a
dense road system is required. The few instances for which data are
available indicate that site disturbance during animal logging is sub-
stantially less than that brought about by tractor skidding, not including
the road system effects (Pearce and Stenzel 1972).
TRACTOR
Crawler tractors, introduced to logging in the early 1930's, are
now used throughout the Pacific Northwest. The slope distance from the
outer boundary of the cutting unit to the landing (external yarding
distance) is limited to approximately 300 feet and 20 percent slopes
for uphill yarding. Maximum downhill yarding is limited to yarding
distances of 800 feet on slopes of 35 percent (Studier and Binkley 1974).
Crawler tractors used for logging are normally equipped with a winch
and wire rope (Figure 2). When yarding on steep, swampy, rocky or
otherwise difficult terrain, the tractor can be located on stable terrain
and the winch used to skid logs a short distance to the tractor. The
winch can also be used to pull the tractor from terrain in which limited
traction is available (Pearce and Stenzel 1972). Various attachments,
primarily arches and sulkies, have been developed for tractors which
reduce the degree of contact between log and ground. The arch, which is
either track-mounted or an integral part of the tractor, is designed to
raise the leading end of a tractor-skidded log (Figure 3). A tractor
sulky or "wheeledarch" is similar to the arch. Track-mounted arches are
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reported to be 30 to 50 percent heavier than tractor sulkies. Con-
sequently, the tractor sulky unit can negotiate steeper grades, which
results in a higher potential for soil disturbance and erosion (Pearce
and Stenzel 1972).
CRAWLER TRACTOR
GROUNDSKIDDING LOGS
FIGURE 2
CRAWLER TRACTOR WITH
INTEGRAL ARCH SKIDDING LOGS
FIGURES
Agricultural and industrial tractors were the first wheel-type units
to be used for logging, During the 1950's, however, developmental work
by several manufacturers was undertaken to produce rubber-tired wheel
skidders designed specifically for logging.
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Wheel skidders have the advantage of greater speed but the dis-
advantage of limited traction. They can be equipped with a light bull-
dozer blade, useful for clearing obstacles from skid roads and moving
logs at the landing. Wheel skidders can be equipped with an articulated
hydraulically operated grapple which lifts the leading end of the log
free of the ground and reduces soil disturbance during skidding. In-
accessible logs can be winched short distances into position to be
grappled and skidded.
CABLE
Cable logging, of which there are many forms, is used throughout the
Pacific Northwest. Cable systems are designed to yard logs from the
felling site by a machine equipped with multiple winches commonly called
a yarder. A wide range of systems are available today for logging both
large and small timber.
Although originally used almost exclusively for yarding clear cuts,
recent innovations have made cable systems highly suitable for yarding on
partial cuts such as selection cuts. Cable logging is highly efficient
for logging steep rough ground on which tractors cannot operate. Some
cable systems can operate in any direction - upslope, downslope and along
the contour. Most importantly, several studies, (Wooldridge I960;
Dyrness 1965; Aulerich et_ al 1974) have indicated that cable systems result
in far less site disturbance than tractor logging and can operate on terrain
for which tractors would be unsuitable due to the possibility of site
disturbance. Depending on the system used, yarding distances of up to
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4,000 feet are possible (Studier and Binkley 1974), which tends to
reduce the required road density compared to tractor logging.
For many years cable logging systems could be classified as either
high lead or skyline. Balloon logging, first introduced in North
America in the 1960's, can be considered as a third type of cable
yarding. The high lead system (Figure 4) moves logs from stump to
landing by reeling in a wire rope called the mainline. The mainline
is fastened to a block which is located well above the ground on a spar
tree or steel tower.
HIGH LEAD SYSTEM
GROUND SKIDDING UPHILL
FIGURE 4
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Portable steel towers, ranging from 80 to 120 feet in height, are
now used almost exclusively for high lead logging. The tower assists
in providing lift to the leading end of the log in order to reduce
friction between log and ground, overcome obstacles, and reduce the
amount of soil disturbance. The maximum uphill yarding distance of high
lead systems is approximately 1,000 feet; whereas downhill yarding is
limited to approximately 500 feet (Studier and Binkley 1974; Binkley
1967). Although downslope and sideslope yarding are possible, control
of log movement is minimal and severe site damage often results (Peters
1973). The system is suited only for clear cut logging.
The mobile shovel yarder or mobile logger is a modification of the
high lead system (Studier and Binkley 1974). Usually track mounted,
its mobility permits yarding partial cuts as well as clear cuts. Logs
can be yarded perpendicular to the contour along parallel yarding roads
and decked in windrows along the edge of the truck road. Consequently,
landing size can be reduced with this system (Pearce and Stenzel 1972).
The system is limited to uphill yarding for distances of 500-700 feet
(Studier and Binkley 1974).
The jammer (Figure 5) came into widespread use in northern Idaho
and the Intermountain sub-regions following World War II (Pearce and
Stenzel 1972). Jammers are either track or wheel mounted and are
equipped with either a steel or wood boom. The units are equipped with
either a one- or a two-drum winch. One drum is used to power a skidding
line which is attached to the log; the other drum, if used, is attached
to a haulback line. Jammer logging is limited to uphill yarding of
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clear cuts and distances of 300-400 feet. Consequently, an intense
network of roads, oriented predominately parallel to the contour, is
required for this system. Logs are usually decked along the lower side
of the road (Studier and Binkley 197/4). The dense road system and
constant contact of the log with the ground during skidding, required
in jammer logging, creates considerable soil disturbance and erosion
potential.
JAMMER GROUND SKIDDING
LOGS UPHILL
FIGURES
Skyline logging systems, the most versatile of all cable logging
methods, were introduced in the Pacific Northwest in the early 1900's
(Pearce and Stenzel 1972). Since the turn of the century, loggers have
devised a number of skyline systems including the Tyler, North Bend,
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South Bend, and the Lidgerwood skidder. In the late 1940"s and early
1950's, the European skyline crane systems were introduced in the Pacific
Northwest primarily on an experimental basis (Wooldridge I960). These
systems are capable of yarding timber from the most difficult sites with
almost no soil disturbance or damage to the residual stand. Electronic
carriages for use on existing high lead and slackline yarders were
developed in the late 1950's in response to a need for a highly productive
system which included also the silvicultural advantages of the European
skyline cranes (Lysons 1973).
Binkley (1966) describes the skyline crane as a yarding system in-
corporating a carriage which moves logs laterally and then longitudinally
along a suspended cable. Logs are first yarded to the skyline with one
end on the ground. Subsequently, the logs are moved longitudinally along
the skyline either completely suspended free of the ground or with one
end on the ground, depending on topography and type of equipment used.
For downhill yarding it is preferable to suspend the logs free of the
ground. Uphill yarding can be accomplished with one end of the logs in
contact with the ground while still keeping soil disturbance to a minimum.
Lysons and Twito (1973) have categorized all skyline systems as one
of three types:
1) tight skylines (single or multispan)
2) slack skylines (also called live skylines)
3) running skylines
Differences between the systems primarily involve the skyline set up,
type of carriage and yarder design.
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The tight (standing) skyline has "both ends anchored and employs
either a single or double drum yarder for moving a carriage along the
skyline (Figure 6). Most tight ( standing) systems can yard either
uphill or downhill; however, downhill operation is more common, De-
pending on the type of yarder used, yarding distances up to 5,000 feet
are possible (Studier and Binkley 1974). For full suspension of the
logs during longitudinal yarding, multispan rigging is sometimes
necessary (Figure 7). The long yarding distances allow a low road density.
STANDING LINE
OPERATING DRUM
TIGHT SKYLINE
(SINGLE SPAN)
FIGURES
STANDING LINE
TIGHT SKYLINE
(MULTISPAN)
FIGURE?
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European skyline cranes are essentially multispan tight skyline
systems designed primarily for downslope yarding and can "be used for either
clear cuts or partial cuts. The Wyssen Skyline crane was introduced in
North America in the late 19-40' s. The system can be categorized as a
standing skyline which combines both lateral and longitudinal yarding
capability. Single span and multispan arrangements are possible. The
system is capable of lateral skidding distances of up to 250 feet and
longitudinal yarding of up to 5,000 feet. Logs can be yarded either
partially or completely suspended above the ground. The multispan system
is designed for complete suspension of the logs, except during initial
lateral skidding.
The multispan system's skyline (Figure 7) permits long skyline roads
using intermediate support which allows large areas to be yarded with
minimal site disturbance. Soil disturbance which does occur is limited
largely to short distances along the contour. Consequently, erosion
problems are reduced to a minimum. Yarding can be upslope or downslope,
reportedly over distances up to 6,000 feet. One of the major advantages of
the skyline crane system is the unusually large yarding distance and con-
comitant minimal road density.
The slack skylines, also known as live skylines, require at least
two drums on the yarder. One end of the skyline is anchored and the
opposite end is attached to a drum on the yarder so that the skyline can
be lowered to attach to a load (Figure 8). Carriages are operated
mechanically by radio control. Either chokers or a grapple is used for
attachments of the logs.
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OPERATING DRUM
^LIVE SKYLINE DRUM
SLACK SKYLINE
FIGURES
These systems are reportedly more versatile and productive than
standing skylines (Lysons and Twito 1973). Except during lateral
yarding, the logs are mostly free of the ground, thereby allowing faster
inhaul while minimizing soil disturbance and damage to any residual trees,
Maximum yarding distances are approximately 2,000 feet. The systems can
be used for partial cuts as well as clear cuts.
One of the latest innovations in cable logging systems is the running
skyline (Figure 9). Running skyline systems require the use of inter-
lock mechanisms that couple the main and haulback drum to control line
tension and resulting lift forces. Uphill and downhill yarding over
distances of up to 2,000 feet are possible. The use of a slack-pulling
carriage permits lateral yarding for distances of up to 150 feet (Burke
1975; Lysons 1973). During lateral yarding, one end of the log is in
contact with the ground. With adequate deflection, however, longitudinal
yarding is accomplished with the log free of the ground. When equipped
with a slack-pulling carriage both partial cuts and clear cuts can be
yarded. Grapple yarders, however, are limited to yarding of clear cuts.
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-HAULBACK DRUM
MAIN DRUM
RUNNING SKYLINE
FIGURES
A mobile crane equipped with a running skyline and either chokers or
a grapple is a highly efficient and adaptable yarding machine (Burke 1972)
(Figure 10). Logs can be yarded for distances to 1,000 feet. The system
can be moved with minimal losses of time. Logs can be lifted clear of the
ground, minimizing soil disturbance. Both uphill or downhill logging can
be accomplished. Since the crane moves along a truck road, a near parallel
network of yarding roads is required. Logs are distributed along the edge
of the road rather than being concentrated at a landing. As a result,
this type of logging system has considerable potential for reducing site
damage.
Balloon yarding was tested in northern Europe during the 1950's, and
in Canada and the United Stales in the 1960's. Helium-filled balloons of
a variety of types and sizes are used to lift the logs. Three rigging
systems have been used for balloon logging: high lead, inverted skyline
and running skyline (Peters 1973) (Figure 11). A tail block and a
series of corner blocks are required in order to bring the balloon close
to the surface for attaching the logs. The blocks are moved as needed to
bring the balloon down to the ground at various locations (Figure 12),
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Theoretically, a maximum yarding distance of 5,000 feet is possible;
however, 2,500 to 3>000 feet seem to be a more realistic limit (Peters
1973; Gardner et_ al_ 1973). Each turn of logs can be lifted entirely
free of the ground surface. Hence, the system is particularly adaptable
to logging steep slopes with fragile soils which are highly susceptible
to erosion. Damage to residual trees can be kept to a minimum. However,
balloon logging is particularly vulnerable to adverse weather conditions.
MOBILE-CRANE
GRAPPLE-YARDING SYSTEM
FIGURE 10
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Balloon
Yardtr
Ynrd«r
Haulback
Ynrdtr
HIGH LEAD
Balloon
Skylln*
INVERTED SKYLINE
Balloon
Skyline and Haul bock
BALLOON LOGGING
RIGGING SYSTEMS
FIGURE 11
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LOGGING SYSTEMS WITH
OPTIMUM YARDING DISTANCES
AND SLOPE
FIGURE 12
Adapted from: "Cable Logging Systems,"
PNW, USFS
73
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AERIAL
One of the more recent innovations in yarding involves the use of
helicopters (Figure 13). One way to view the helicopter is as an expen-
sive, infinitely-mobile yarder which can elimate many of the constraints
that hamper conventional logging systems in areas of environmental con-
cern. Yarding distances in excess of 6,000 feet are possible with
optimal distances of 2,500 to 4-,000 feet. The logs are flown completely
free of the ground from stump to landing. Consequently, soil disturbance
can be held to a minimum. Safety and maneuverability requirements
necessitate the construction of large landings, perhaps as much as one
acre in size. Most operators prefer uphill yarding. For a yarding
distance of 2,500 to 3,000 feet an elevation gain of 800 feet is reasonable
(Burke 1973).
Because of the high cost of equipment and large crews necessary,
hourly operating costs of helicopters can be 10 times that of conventional
cable systems. Helicopters are limited by their vulnerability to weather,
limits to elevation differences between stump and landing, and lack of
suitable landing locations. Lack of access roads can hamper post-harvest
management (residue and regeneration) of logged area (Burke 1973).
WATER QUALITY IMPLICATIONS
The impact of logging activities on water quality is determined largely
by the extent to which a forested area is disturbed by the network of
access roads and by the movement of logs from stump to landing. Soil
compaction brought about by the use of heavy equipment such as logging
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HELICOPTER LOGGING AT A LANDING IN
THE BOISE NATIONAL FOREST, IDAHO
FIGURE 13
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tractors has a direct impact on water quality as well. Logging methods
which result in higher concentrations of slash on the logged area can
also adversely affect water quality. Because Chapter 4 includes a de-
tailed review of the literature pertaining to these effects, specific
literature will not be cited in this section. Rather, this brief
summary is concerned with contrasting various logging systems insofar
as they can affect water quality.
Helicopter and balloon logging generally result in the least amount
of soil disturbance at the felling site. Helicopters, however, are
expensive and require large landings which can contribute measurably to
soil erosion if not properly maintained. Both systems are vulnerable to
adverse weather conditions; their use can therefore extend the time
required to complete logging of an area, and consequently, the period of
erosion susceptibility may be extended. On the other hand, the required
road density is at a minimum, which is of considerable value in reducing
erosion potential.
Long reach single or multispan skyline systems with capability for
lateral yarding and complete suspension of logs during longitudinal yard-
ing also allow low road densities for access. Disturbance of the felling
site is restricted almost entirely to that which occurs during lateral
yarding. Normally this disturbance is minimal. Landings of moderate
size are required. Depending on the system used, the rigging time can
be longer than that required for more portable skyline systems. Con-
sequently, the time required to complete logging can be extended. Never-
theless, of the various cable systems, this type will in general have the
least impact on the site.
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Since the maximum yarding distance of slackline systems is in
general less than that of the tight skylines, road density must increase
with their use. The degree of site disturbance, exclusive of the road
system, "brought about by slackline systems is comparable to that of
tight skylines. Rigging time is comparable, also. Since the slackline
systems are in general more productive than tightline systems, the total
time required to log an area is reduced over that of most tightline
systems. When considering all factors, tightline and slackline systems
probably inflict comparable levels of overall site disturbance.
The maximum yarding distance of running skylines is comparable to
that of slackline systems. Consequently, road density could be expected
to be comparable, also. Frequently, a crawler tractor is used for the
tail hold of a running skyline. Movement of the tractor over the
setting can introduce additional soil disturbance and compaction.
Normally, however, the magnitude of this additional disturbance is
minimal. Rigging time is low and production rates of running skylines
are in general higher than other cable systems. Consequently, for a
given setting logging can be completed in a relatively short period.
When equipped with running skylines and a grapple, mobile cranes can
yard logs to continuous landings adjacent to the road (Burke 1972).
Consequently, site disturbance due to land construction can be limited.
High lead systems, which are suitable for uphill logging of clear
cuts only, are restricted to yarding distance of 1,000 feet, although
700-800 feet is probably a more reasonable maximum. As a consequence,
access road mileage must be increased for use of this type of cable
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system over that of the cable systems discussed earlier. More importantly,
however, high lead systems provide practically no lift to the logs during
yarding except in close proximity to the yarder. In general, the area of
soil disturbance is increased over that of the various skyline systems.
Also, smaller settings of high lead logged areas require a higher con-
centration of landings as compared to skyline systems. Since, for the
most part, logs are skidded while in contact with the ground, high lead
systems tend to concentrate slash in ravines and stream bottoms. These
concentrations can have adverse impacts on water quality due to floatable
debris in streams and the development of debris dams.
Jammer logging is the most road intensive of all of the cable systems.
Restricted primarily to yarding uphill, jammers provide little or no
lift to logs during skidding. Consequently, relatively large areas of
soil disturbance usually result. Normally the logs are decked below the
road for loading and hauling, so the area of soil disturbance for landings
is relatively small.
Tractor logging with either wheel skidders or the crawler variety
can disturb soil over relatively large areas. The compaction that results
from tractor logging reduces infiltration rates and accelerates surface
erosion. Soil disturbance and surface erosion are increased when tractors
are used on steep terrain at higher elevations. In general, tractor
logging should be limited to slopes of less than 35 percent. Because
tractors generally operate most efficiently over relatively short skidding
distances, access road mileage can be expected to be high and similar to
that of high lead logging. Studies have shown that if logging is well
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planned in advance, site damage during tractor logging can be markedly
reduced over that of an unplanned logging operation.
Forest Residues
MANAGEMENT
Forest residue is defined as the unwanted, generally unutilized
accumulation in the forest of woody material, including litter on the
forest floor, that originates from natural processes or from the
activities of man, such as timber harvesting, land clearing and cultural
practices (Jemison and Lowden 1974). Harvesting operations produce
large quantities of residue, but so do many other forest operations.
Small trees, tree limbs, and tops are left as residue following pre-
commercial thinning. Land clearing of all kinds, e.g., roads, utility
right-of-way, and for urban and agricultural development, is responsible
for the production of sizable volumes of residue.
The conversion of brush lands to sawtimber and the conversion of
one timber type such as alder to a softwood, a frequent occurrence
on the west slope of the Cascade Range, will frequently produce large
volumes of residue. Residues are produced when trees or other vegetation
are killed by natural processes such as insect kills, wind, disease,
fire and drought. However, it is the residue from logging that is of
major concern because of the large volumes produced and the vast area
covered (Jemison and Lowden 1974). Many of the most damaging fires in
the Pacific Northwest start or spread in slash, particularly on the west
slope of the Cascades (Howard 1971).
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In the Douglas-fir region of Western Oregon and Washington, gross
volume of slash ranged from 1,507 cubic feet per acre on private lands to
4,511 cubic feet per acre on national forest land. Logging slash in the
ponderosa pine regions is substantially less. Gross volumes ranged from
423 on private lands to 404 cubic feet per acre in national forests. Net
volumes were slightly less at 376 and 325 cubic feet per acre, respectively.
The larger volumes of residue on national forest lands can be attri-
buted to a higher proportion of old-growth timber (which produces more slash)
and the fact that private companies operating on their own lands receive all
benefits from residue reduction efforts such as increased mobility for second
growth management (Howard 1973). The differences in volume suggest that
management of residues in the Douglas-fir region will be more complex than
that required for the ponderosa pine region.
Typically, residue management techniques fall into four broad
categories (Jemison and Lowden 1974).
1) no treatment
2) rearranging or mechanically treated and left
3) removal and disposal
4) burning
Each year slash on a large part of the forests in the Pacific North-
west receives no treatment. Areas in which the volume of slash is rela-
tively low often requires no treatment, and leaving slash untreated may
in some instances be the least destructive practice. Where needed, for
example, residues can benefit soil formation processes and reduce soil
erosion. Notwithstanding, the fire hazard posed by untreated residues
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can be intolerable, particularly on the west slope of the Cascades where
residue volumes tend to be large. Intense fire exposes the soil surface
and can lead to accelerated erosion.
The practice of rearranging or mechanically treating residue, prac-
ticed in some parts of the country with success, has received only
limited use in the Pacific Northwest. During the past ten years heavy
equipment for chopping, crushing or masticating residues has been developed.
Generally speaking, the equipment is suitable only for areas in which
residue sizes and total volumes are relatively low. Most of this equip-
ment must be used in conjunction with a crawler tractor and hence is
limited to slopes of 35 percent or less. Soil compaction can result.
Chipping of residues for dispersal over roads, landings and cutover
areas has been suggested. However, chipping is costly. In areas of
high volume slash, chips can reach an excessive depth and thereby add to
the fire hazard, reduce the availability of soil nitrogen and impede
regeneration. On the other hand, chips protect the soil from high
impact rainfall and can reduce soil losses due to surface erosion.
Beginning in about 1970 the U. S. Forest Service initiated a practice
of yarding the larger size classes of residues from recently logged units.
The practice, termed YUM (Yarding Unmerchantable Material), was limited
to a relatively small proportion of the cutover areas located predominately
on the west slope of the Cascades. Unmerchantable material is yarded
during or following log removal and piled at the landing. In some
instances, especially designed cable logging systems are used to yard
residues. Later, the material is burned, or if a substantial volume of
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the material is sound and market conditions are favorable, it may be sold
on the pulp market.
Burning of residues is practiced in all parts of the Pacific North-
west. The extent to which burning is used on both public and private
lands is governed primarily by factors such as the state of advanced
reproduction, cost of burning, size of the fuel load, and the availability
of favorable burning conditions.
Area slash burning, piling and burning, and light underburning are
by far the most commonly used control methods. These burning techniques
have been used extensively for a number of years. More recently the
use of incinerators, sometimes referred to as bin burners, has been
introduced for disposal of residue in heavy use areas such as campgrounds,
ski areas, along roads and near developments. Incinerators can be of
simple design such as especially prepared open pits. Alternatively,
portable prefabricated steel bins are available. Bin burners have, to
date, received only limited use for residue management primarily due to
high cost.
Slash burning is usually done in the spring or fall, although summer
burning is sometimes practiced along the coast. Fire lines are built
either by hand or with bulldozers around the area to be burned. Snags
are felled to lessen danger of fire escape and prelocated pumps, hose
systems, tankers, and standby fire crews may be used.
Area slash burning, more frequently called broadcast burning, has
been the most widely used of all burning techniques. According to
Jemison and Lowden (1974), in the 1962-64 period clearcut logging slash
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on all ownerships in Oregon and Washington was broadcast burned on
51,800 ha. and piled and burned on 50,991 ha. Since that time, broad-
cast burning has decreased 4-0 percent and pile and burn acreage has
increased 50 percent, due in part to a change from clearcutting to
partial cutting on national forests. Although used primarily on the
west side of the Cascade Range in clear cuts, broadcast burning is used
occasionally in the pine areas east of the Cascades where residue volumes
are low.
As suggested earlier, piling and burning is usually associated with
some form of partial cutting, e.g. selection cutting. Piling before
burning affords a measure of protection to the remaining stand. De-
pending on the quality, size, and dispersal of residue, either machine
or hand piling is used. Machine piling is more common and the slash is
bunched in piles or is windrowed. Crawler tractors are equipped with
special brush blades with teeth in order to minimize the quantity of
soil that is deposited in the slash piles. Other types of piling
equipment have been used but the tractor receives widest use. Windrowing
of slash is practiced on the west slope of the Cascade Range as a part
of the scarification of lands prior to artificial regeneration. Light
underburning of uncut forest is a practice confined largely to the
southern states. This particular control method has been suggested for
ponderosa pine but to date has received limited use.
WATER QUALITY IMPLICATIONS
Residue management techniques influence surface erosion, mass soil
movement, and the quantity of both dissolved and undissolved organic
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materials which are present in runoff waters. In general, any treatment
such as residue management which removes or disturbs organic matter in
contact with the soil surface may increase soil erosion and stream
sedimentation (Rothacher and Lopushinsky 1974). Leachates from residues,
if present in sufficient quantity, can collect in streams following log-
ging and can be toxic to aquatic organisms.
Rothacher and Lopushinsky (1974) point out that from the standpoint
of surface erosion it may be best to leave slash after logging without
further disturbing the site (no treatment). However, Haupt and Kidd
(1965) have shown that slash can be rearranged to form skid trail barriers
and retard surface erosion. Slash can be relocated on hillsides and in
stream bottoms to act as a sediment filter or trap. Also, cull logs
placed across the slope can be beneficial for trapping material moved by
surface erosion.
Chipped residues distributed over landings and along right-of-ways
can also be beneficial for reducing surface erosion. On the other hand,
mechanical treatments such as crushing and chopping of residues requires
the movement of tractors equipped with auxiliary devices over the cutover
area. Fire lines constructed with crawler tractors also require the
movement of heavy equipment on cutover lands. Practices of this type can
accelerate surface erosion due to exposure of additional mineral soil,
compaction, and reduced infiltration.
Normally, the additional soil disturbance brought about by yarding
unmerchantable material (YUM) should not add substantially to problems
of surface erosion unless the logged area is unusually steep. Not
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infrequently, residues located on steep hillsides near the head of a
drainage tend to collect in the stream bottom. Yarding residues can
help avoid this particular impact to water quality. On the other hand,
as pointed out by Brown (197-4) the practice of burning all residue
yarded to a central point located in a draw near the landing can create
a severe source of erosion. Burying of residues introduces an additional
area of soil disturbance.
Although, as Rothacher and Lopushinsky (1974) point out, residue
treatments apparently have little direct effect on mass soil movement,
their indirect contribution can be marked.
Residues may indirectly contribute to mass erosion. For
example, in steep terrain, logging slash may be moved downslope
by small slides of saturated soil to block stream channels.
This, in turn, can result in large debris-mud torrents causing
severe mass erosion. Any logging debris left in stream channels
will increase the chance of channel blockage.
A number of studies reviewed in Chapter 4 indicate that infiltration
rates are reduced and surface erosion accelerated in soils which are
severely burned during slash fires. Considerable quantities of organic
matter, an important cementing agent in soil aggregate formation which
effects infiltration rate, can be lost from the soil, especially under
conditions of elevated temperature. Although the area of severely-
burned soil is normally relatively small (5-8 percent), it is increased
by broadcast burning in areas of heavy concentration of slash. Piling
and burning of unmerchantable material can also result in severe burns
in localized regions.
Burning can markedly increase the release of chemicals, some of
which reach streams and influence water quality (Frederickson 1971).
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Tiedemann (1973) has reported that fire was responsible for increasing
nitrate-N concentrations in runoff waters from experimental watersheds.
Concentrations of calcium, magnesium, and sodium declined, presumably
due to dilution caused by increased runoff.
Log Storage and Handling
PRACTICES
Approximately 3 billion board feet of logs are dumped and handled
each year in the public waters of the Pacific Northwest (Hansen et al
1971). Of this total, a relatively small quantity of logs is processed
in stream and impoundments in Idaho and Montana, and approximately 500
million board feet are dumped in the coastal waters of southeast Alaska
(Pease 1974). The remainder, a quantity in excess of 2 billion board
feet, is dumped in the waters of Washington and Oregon.
Log storage in the free flowing rivers as well as freshwater im-
poundments in the inland part of the Pacific Northwest is relatively
small. In contrast, log storage west of the Cascades is predominately
in salt water bays and estuaries or near the mouths of the larger river
systems. It is reported that 650 acres are required for log storage in
Alaska (Pease 1974). This figure suggests that the log storage area
in the coastal region of Washington and Oregon may be approximately
2,500 acres.
In Alaska the composition of log rafts is approximately 70 percent
western hemlock, 25 percent sitka spruce, and 5 percent western red and
yellow cedar. In the inland part of the Pacific Northwest western white
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pine, ponderosa pine and Douglas-fir are the principal species that
receive water storage, whereas, the "bulk of the logs stored in western
Washington and Oregon are Douglas-fir and western hemlock.
In northern Idaho limited log storage facilities have been developed
on the St. Joe River, on the Clearwater and Palouse River and on the
Pend Oreille River near Newport, Washington. For the most part the
logs are free-fall dumped from trucks at specific sites. Several of
the facilities are used for holding logs prior to processing in nearby
sawmills and/or pulp mills.
Pease (1974) has identified four types of log storage facilities in
the coastal waters of southeast Alaska.
1) sale area dumping sites
2) sale area raft collecting and storage sites
3) winter raft storage sites
4) mill storage and sorting sites.
Several methods for introducing logs into the water have been
identified, including:
l) bundled on land, lifted and lowered into the water using a
crane
2) bundled on land and either slid or skidded into the water
3) lifted, skidded or slid into the water individually and then
bundled
4) dumped on the beach, bundled, and skidded into the water at
high tide
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After dumping, logs are collected into rafts approximately 70 x 550
feet in dimension, each of which can contain in the range of 300-600
thousand board feet. Bundled logs stored in the salt water bays of
southeast Alaska sometimes run aground particularly at low tide. Pease
(1974) reports that the abundance of benthic infauna was reduced dras-
tically at a log storage area in southeast Alaska due to the grounding
of bundled logs. Bottom sediments had been compacted to the consistency
of sandstone.
In western Oregon logs are dumped in a number of salt water bays and
estuaries including Coos Bay, Yaquina Bay and Siuslaw Bay, Tillamook
Bay and Youngs Bay. In addition, logs are stored in the waters of the
lower Willamette River and in the sloughs of the lower Columbia. Other
freshwater storage areas include the Klamath and Deschutes Rivers. Logs
are introduced in the water by free-fall dumping and the lowering of
bundled logs with a crane. In some locations, logs are stored in the
water for varying periods of time prior to processing. In other regions,
large rafts are made up of bundled logs for transport by tug to a mill
site. Raft sizes are similar to those used in Alaska.
In western Washington, most of the log storage facilities have been
developed in Puget Sound and the Straits of Juan de Fuca. Grays Harbor
and Willipa Bay and the lower Columbia River also serve as major locations
of log storage facilities. Rafting operations are maintained at several
locations on the south end of Puget Sound, including Budd Inlet, Henderson
Inlet, and Oakland Bay near Shelton. A relatively small rafting operation
exists in Hood Canal. In addition, the harbors at Tacoma, Seattle, Everett,
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Anacortes, Port Gamble, and Port Townsend are used for storage of log
rafts. Log rafts are made up at the south end of Lake Washington and
moved by tug through the ship canal into Puget Sound. In both western
Washington and Oregon the species compostion of log rafts is approxi-
mately 70-75 percent Douglas-fir. The bulk of the remainder is in
western hemlock. A relatively small part of the total is made up of
western red cedar.
The development of heavy equipment suitable for efficient handling
and sorting of logs has resulted in more extensive use of land storage
facilities in recent years. Areas devoted to this purpose are frequently
used for both sorting and storage and may or may not be used for supplying
a processing facility located close by. Many, but not all, of the land-
based sorting areas are equipped with sprinkling systems. Not infre-
quently, large quantities of bark and wood debris collects in the storage
yards after long periods of use and must eventually be disposed of.
Waters used for sprinkling usually are introduced into the natural
drainage waters of the area. The extent of concentration of substances
toxic to aquatic organisms which results depends largely on the number
of logs in storage and on the size of the receiving stream system. In
general, water-based storage facilities for logs are used much more
extensively than land based operations in the Pacific Northwest. Con-
sequently, insofar as water quality is concerned, it is the water-based
facilities that have received and will continue to receive the most
attention.
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WATER QUALITY IMPLICATIONS
Pease (197/4) and Schaumburg (1973) have identified two major wastes
which affect water quality: (l) bark and wood debris, and (2) soluble
organic materials (leachates).
Bark losses occur at several stages of log handling. The quantity
deposited in water is governed primarily by:
l) species
2) method of handling
3) type of storage area
4) length of time in storage
The concentrations of leachates or water-soluble organic materials
in storage water is determined by:
l) species
2) length of time in storage
3) flushing action of the storage area
4) the age of the logs at the time of timber harvest
5) the amount of bark remaining on the logs when in water storage
For specific information on the above, see Chapter 4.
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CHAPTER 4
IMPACT OF FOREST PRACTICES
ON WATER QUALITY
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IMPACT OF FOREST PRACTICES ON WATER QUALITY
Surface Erosion
Surface erosion is the direct result of rain striking an exposed
soil surface and detaching a soil particle, then transporting the de-
tached particle by surface flow to some downslope deposition point.
Forest practices disturb and expose mineral soil (as contrasted to the
top organic layers) in varying degrees. In a review of literature con-
cerning surface erosion, Smith and Wischmeier (1962) identified four
basic physiographic factors affecting surface erosion:
l) rainfall characteristics
2) soil characteristics
3) topography
4) plant litter and cover
PHYSIOGRAPHY
Soil detachment is caused by raindrop impact and is therefore in-
fluenced by drop kinetic energy which varies with velocity and mass.
The transport of detached soil particles in overland flow is controlled
by runoff amount and turbulence, both of which are to some extent func-
tions of rainfall intensity.
Soil properties pertinent to the erosion process include physical,
chemical, organic, and saturation properties, parent material, and re-
sistance to detachment.
Some of the earliest work on soil erodibility was conducted by
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Middleton (1930). He developed two indices for indicating inherent
soil erodibility: the "dispersion ratio" and the "erosion ratio." Both
are based on laboratory determinations of aggregate stability, particle
size distribution, and moisture content. Anderson (1951) tested Middle-
ton's ratios for possible use in upland areas of California and recom-
mended use of the dispersion ratio since he found it offered a somewhat
better index of soil erodibility than did the erosion ratio. He sup-
plemented these indices later with his "surface-aggregation ratio"
(Anderson 195/4). Wooldridge (1964, 1970) has used mean water-stable
aggregate size as a measure of soil erosion hazard of forest soils. He
reported a considerable decrease in mean aggregate size with increasing
erodibility.
Parent material generally exerts a profound influence on the prop-
erties of forested upland soils. Profiles tend to be shallow and im-
mature, and many characteristics may be inherited directly from the parent
material. Willen (1965), Wallis and Willen (1963), and Andre and
Anderson (1961) demonstrated that soils derived from acid igneous rocks
tend to be considerably more erodible than soils derived from other
parent materials. As a result of a study of soils at 258 locations,
Wallis and Willen ranked 12 parent materials in the following manner:
Erodible parent materials—granite, quartz diorite,
granodiorite, Cenozoic nonmarine sediments, schist.
Intermediate—diorite, a variety of metamorphic rocks.
Nonerodible—Cenozoic marine, basalt and gabbro, pre-
Cenozoic marine sediments, peridotite and serpentinite,
and andesite.
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The size and shape of the particles or aggregates and the degree
of soil compaction are the most important physical properties to be
considered. Compaction generally retards particle detachment, but also
reduces infiltration and thereby increases overland flow.
Organic matter is an important cementing agent in the formation of
large water-stable aggregates. Wooldridge (1965) found organic content
has a significant effect on surface erosion primarily through its effect
on mean aggregate size. Willen (1965) also found that those soils which
were the most stable had the highest organic matter content. Organic
matter content is affected by vegetation, precipitation, and other cli-
matic factors, consequently varying with aspect and elevation.
Ions adsorbed on the exchange complex in the soil may have a strong
influence on erodibility by causing either flocculation or dispersion.
Wallis and Stevan (1961) evaluated through regression analysis the ef-
fects of calicum, magnesium, potassium, and sodium on erosion, and found
that calcium and magnesium had a positive and significant correlation
with soil erodibility due to ionic dispersion and flocculation.
Saturation or water content of soils affects the buoyancy of the
particles and the capillary forces, thereby influencing the resistance
to detachment. Resistance to detachment also depends on cohesion (elec-
trical bonding), adhesion (chemical and physical cementation), compac-
tion, and the effective diameter-surface area relationships. Cohesion,
adhesion, and compaction affect the internal forces holding the soil
together. The effective diameter-surface area relationships affect
the detachment force.
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Hydrologic characteristics affecting the erosion process include
the infiltration-runoff relationships, cover, runoff characteristics,
soil-water interfacial characteristics and snowmelt. Infiltration-
runoff relationships include percolation, or the surface water intake
potential; permeability, or the potential groundwater flow rate; and
the surface detention and storage capability of the land surface.
One of the most important factors involved in the erosion process
is the amount of cover, which not only protects the soil surface from rain-
drop detachment but aids significantly in the interception, retention and
infiltration process. Lowdermilk (1930) studied the effects of forest lit-
ter on runoff and erosion of several California soils. He concluded that
the beneficial effects of litter cover were not due to its water absorbing
capacity, but rather to its action in protecting soil from the destructive
action of raindrops. Packer (1957) found that in the Boise Basin of Idaho,
total ground cover and the maximum size of bare soil openings exerted the
most influence on the erosion process, and concluded that in order to min-
imize runoff and erosion, ground cover density should be at least 70 per-
cent, with maximum size of bare openings no greater than four inches.
Dortignac and Love (1961) studied vegetation and soil influences on
infiltration in granitic soils of the ponderosa pine-bunch-grass type of
the Colorado Front Range. They found the most important factors influenc-
ing infiltration were weight of dead organic material and the amount of
non-capillary pores in the surface soil.
The primary elements related to the topographic effects on
erosion include elevation, slope and aspect. Willen (1965) reported
significant increase in erodibility (surface-aggregation ratio) with
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increasing elevation. Andre and Anderson (1961) have also observed
a significant relationship "between elevation and credibility.
Bethalmy (1967) investigated the effect of exposure on runoff and
erosion in central Idaho. He found that erosion was much more severe
on southwest facing slopes, and concluded that this is primarily due to
differences in the organic content of the soil.
SILVICULTURAL AND LOGGING SYSTEMS
The selection and layout of the silvicultural system directly
affects the water pollution potential of the harvesting operation.
Rothwell (1971) reported that the degree of site disturbance asso-
ciated with cutting method decreases in the following order: clearcut,
seed tree, shelterwood, group selection and selection.
The logging system used can have a major influence on the extent
of soil erosion. In general, and not considering logging roads, the
selection of the logging system most effects water quality. Effects
range from severe to superficial, depending on the methods used, the
degree of planning, and the attention paid to detail of plan execution.
Roads for logging are a prime source of erosion and contribute directly
to stream siltation (Packer and Christensen n.d. ). Roads for skidding
also contribute to soil erosion, but normally to a lesser extent than
logging roads. Tractor and cable logging systems affect the land sur-
face to different degrees of severity. The effects of tractor logging
may be particularly severe in steep mountainous terrain.
Tractors cause deep soil disturbance in the form of compaction,
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displacement, or puddling under saturated conditions. This disturbance
can be extensive because tractor yarding requires a network of skid roads
over the entire cutting unit. Steinbrenner and Gessel (1956) showed that
skid roads occupied 26 percent of the tractor logging area and that per-
meability rate on these skid roads was reduced 92 percent of that in the
uncut area. Garrison and Rummell (1951) reported that in eastern Oregon
and Washington, an average disturbance of 26 percent of the ground surface
and the estimated density reduction of 33 percent in shrubby and herbaceous
plant cover were results of tractor logging.
Cable systems, including high lead, skyline and balloon, have evolved
into highly complex and efficient yarding methods. Because the cable is
attached at some distance above ground, the high lead system provides a
lifting force on the logs over a restricted part of the skidding distance.
Consequently, less soil gouging results. Moreover, since the logs are
generally pulled uphill toward the spar tree, the channels fan out, thereby
tending to spread surface runoff. Some of the skyline systems permit
yarding with very little ground contact at all.
Increasing environmental concerns have heightened interest in balloon
and helicopter logging. Balloon logging requires few roads and eliminates
much of the damage associated with logging because logs are lifted vert-
ically from the ground.
The helicopter is essentially an infinitely mobile yarder which can
eliminate many of the constraints that hamper conventional logging systems
in areas of environmental concern. Helicopter logging may offer certain
advantages where road access is restricted or use of conventional logging
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systems is prohibited, but it may have disadvantages related to cost,
slash disposal, cull material handling, and post-harvest land manage-
ment (Burke 1973). It is extremely sensitive to production cost. The
most ideal use may be to remove scattered trees or pockets of high-
value timber.
Of the various cable systems, jammer logging probably causes the
greatest amount of soil disturbance. Yet, data are available to indicate
that this system produces less damage than that brought about by tractor
skidding. A study in Oregon and Washington by Garrison and Rummel (1951)
showed that jammer logging is superior to tractor logging. Jammer log-
ging on an area considered to be too steep for safe tractor operation
produced deep soil disturbance over 2 percent (of the terrain) and
exposed bare soil over 15 percent (of the area). By way of comparison,
tractor skidding on more favorable terrain produced deep soil disturbance
over 15 percent (of the area) and exposed bare soil over 21 percent.
Campbell et al (1973) surveyed logging damage by rubber-tired skidders
and reported that 23 percent of sites logged in Piedmont region were dis-
turbed. McDonald (1969) showed that in a partial cut operation, forest
soils were 12 and 22 percent compacted from wheeled and crawler skidders,
respectively. Wooldridge (I960) also showed that in a partial cut of
mixed conifer forest type in eastern Washington, tractor logging left ex-
posed mineral soil on 22 percent of the area, whereas less than 6
percent was exposed by a skyline crane.
Haupt and Kidd (1965) reported that in central Idaho, soil was ex-
posed by haul roads and skid trails on 8 percent of the total
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silviculturally-treated area, and that cutting by stem selection exposed
about 1.4 times more mineral soil than cutting by group selection. They
also found that a 10-foot minimum width stream buffer strip offered a fair mar-
gin of safety, but a wider minimum strip, perhaps 30 feet across, would
have been more desirable. Lantz (1971), Hornbeck (1967), Hornbeck and
Reinhart (1964), and Reinhart (1964) found that the maximum turbidities
of streams was significantly increased on the watershed which was entirely
clearcut. By way of contrast, no significant increases were apparent on
the watersheds which were selection cut intensively.
Reinhart and Eschner (1962) investigated the effect of streamflow
of four forest practices in the mountains of West Virginia. On a well-
planned tractor logging operation the maximum turbidity was 25 JTU. An
adjacent watershed was tractor logged without any plan or direction and
maximum turbidities of 56,000 JTU were reported (Table 1).
Table 1. Effect on streamflow of four forest practices.
(After Reinhart and Eschner 1963)
Harvesting Method Maximum Turbidity
Control watershed 15
Intensive selection 25
Extensive selection 210
Diameter limit 5200
Commercial clearcut 56000
These differences were attributed primarily to different skid road lay-
out and construction.
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The following tabulation (Table 2) taken from the results of Swans-
ton and Dyrness (1973) illustrates variation in soil disturbance caused
by four yarding methods used in clearcut operations in the Pacific
Northwest (Dyrness 1965, 1967, 1972):
Table 2. Soil disturbance from four yarding methods and clearcutting.
(After Swanston and Dyrness 1973)
Percent bare soil Percent compacted soil
Tractor 35.1 26.4
High lead 14.8 9.1
Skyline 12.1 3.4
Balloon 6.0 1.7
The literature suggests clearly that tractor logging is a poor choice for
an area in which soil erodibility is a problem. In a study of balloon
logging in central Idaho by Gardner, et_ al_ (1973), limited soil disturb-
ance was noted. This method is well adapted to steep slopes (45 to 90
percent) and shallow and/or fragile soils. Balloon logging is generally
limited to clearcutting with less usage for selection cutting.
Ruth (1967) stated that the silvicultural effects of skyline crane
yarding were similar to conventional high lead yarding when measured in
terms of soil disturbance and damage to tree seedlings and plant cover.
The main advantage of the skyline crane system appears to be its effect-
iveness in yarding logs from steep slopes with minimum road construction.
KLock (1973) has reported on soil disturbance during logging and soil
erosion after logging. His data showed that the percentages of the logged
area observed to be eroded were cable skidding, 41 percent; tractor
skidding on bare soil, 31 percent; tractor skidding on snow, 13 percent;
and helicopter, 3 percent.
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A determiniation of the sediment content of stream water flowing
from experimental watersheds is one of the more common approaches to es-
timate erosion. One of the earlier studies of the effect of logging on
stream sediment was conducted at the Coweeta Hydrologic Laboratory in
North Carolina beginning in 194-6 (Lieberman and Hoover 1948). No re-
strictions were placed on the operators and poor road construction prac-
tices were allowed. During logging, stream sediment content averaged
94 ppm with a maximum of 3500 ppm. Comparable figures for the unlogged
control were 4 and 80 ppm, respectively. The increased sediment was
traced largely to erosion from both the surface and backslope banks of
logging roads.
Eroding skidroads were the major source of stream sediment in a
logging experiment at Fernow Experimental Forest in West Virginia (Rein-
hart and Eschner 1962). Poorly located and constructed skid roads eroded
to such an extent that maximum stream sediment contents reached 56,000 ppm
( See Table 1 ). On the other hand, carefully planned and constructed
skidroads contributed only negligible amounts of sediment. This study
also showed that the impact on water quality was greatest during and im-
mediately after logging and that recovery of vegetation substantially
decreased erosion within one year.
Fredriksen (1970) indicated that following clearcutting and high
lead yarding in three small western Oregon watersheds the sediment in
streams averaged more than 100 times the undisturbed condition over a
period of one year.
Megahan and Kidd (1972) used erosion plots and sediment dams to
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evaluate the effects of jammer and skyline logging systems on erosion
and sedimentation of steep ephemeral drainages in the Batholith of cen-
tral Idaho. The results indicated that no difference in erosion re-
sulted from the two skidding systems per se. The logging operations
alone, excluding roads, increased sediment production by a factor of
about 0.6 over the natural sedimentation rate. Roads associated with
the jammer logging operation increased sediment production an average
of about 750 times over the natural rate for the six-year period fol-
lowing construction.
Trimble and Weitzman (1953) studied the erosional behavior of four
different kinds of tractor skid trails on the Fernow Experimental Forest.
High order skid trails having gradients of less than 10 percent and
drained by waterbars as needed produced 55 Ib/acre of sediment during
the first year after logging. In contrast, erosion from poorly designed
skid trails having no limit on gradients and no waterbars was 433 Ib/acre,
almost eight times as great.
Hoover (1954) reported that direct ground skidding of logs by teams,
which is the common practice in the Southern Appalachian Mountains, was
responsible for a loss of 4,370 ft^/acre of road surface for a three-
month period. Dils (1957) also showed that in the Coweeta hydrologic
watershed logged by horse and oxen skidding, stream turbidities during
a three-month summer period averaged 94 ppm, and maximum turbidity, con-
sisting largely of mineral soils, was 3500 ppm. By way of comparison,
stream turbidities on a control watershed averaged 10 ppm and the maximum
turbidity, primarily organic material, was only 80 ppm.
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Rice and Wallis (1962) showed that the suspended load of Castle Creek
in a Sierra watershed was increased eight-fold during the first year after
the beginning of logging, and the sediment load during the second year
after logging was almost twice its normal rate.
Under average conditions, timber cutting per se, may have no meas-
urable effect on erosion rates. Liken e_t al_ (1970), Oils (1957), and
Lieberman and Hoover (1948) reported that if all vegetation is cut and
left on the site, no increase, or negligible increase, in stream sedi-
mentation will occur. Since log removal is concomitant with timber cut-
ting this is not likely to occur in actual field operations, but it
illustrates the relative water quality significance of cutting versus
logging.
The effect of careful logging combined with clearcutting was inves-
tigated by Hornbeck (1968) on two watersheds. He concluded that small
forested areas in steep terrain could be clearcut without serious erosion
and damage to water quality if the logging operation was carefully plan-
ned and conducted. Brown and Krygier (1971) have reported that for a
clearcut logging operation in the Oregon Coast Range, felling and yarding
with a high lead system did not produce statistically significant changes
in sediment concentration.
Lynch et_ al (1972) conducted a study in central Pennsylvania in which
watersheds were partially clearcut and carefully logged with little dis-
turbance to the soil surface. Regarding water turbidity, during the first
year, the mean concentration was six times greater and the maximum was
fourteen times greater on the clearcut than on the uncut forest. These
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differences in concentration became negligible during the subsequent
four years.
Meehan et al (1969) studied the effects of clearcutting on stream-
flow, suspended sediment, stream temperature, log debris dams, and
indirectly on salmon populations of two watersheds in southeast Alaska.
Although some effects were observed, the timber harvesting as practiced
on these watersheds did not appear harmful to salmon habitat or popu-
lations. James (1957) also found that logging did not change stream
sedimentation and temperature in a logged salmon stream in Maybesco
Creek, Alaska.
RESIDUE MANAGEMENT
The final step in the progression of timber harvesting involves
the disposal of logging residues or slash which remains following re-
moval of the merchantable logs. Effective forest management and the
reduction of fire hazards dictate its removal. Fire is the tool most
commonly used for this removal in many sections of the country.
Burning has been one of the more widely used methods for reduction
of logging residues on clearcuts. Although severe burning may alter
surface soil characteristics sufficiently to bring about some increase
in erodibility, moderate and light burning often has very little direct
effect on soil properties. Therefore, the most important changes
caused by fire are often not in the mineral soil itself, but rather in
the vegetation and litter which protect the soil surface. If essentially
all surface fuel is consumed by an intense fire, exposure of mineral soil
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will result in decreased infiltration rates largely due to destruction
of surface structure by raindrop impact. A light surface fire, on the
other hand, will generally only char the litter, leaving most of the min-
eral soil at least partially covered. In many instances this remaining
litter may afford sufficient protection to maintain soil porosity and,
therefore, to avoid a large-scale increase in accelerated erosion (Dyrness
1967, Neal et_ al 1965, and Isaac and Hopkins 1937).
Results from Packer's (1971) research on logged and burned larch-
Douglas-fir sites in Montana showed that the effects of prescribed burning
on soil and vegetation can impair runoff and soil erosion control. Pre-
scribed broadcast burning, in particular, on eight clearcut blocks sig-
nificantly reduced the protective plant and litter cover, decreased the
surface soil macroporosity, and increased the soil bulk density. Con-
currently, overland flow and soil erosion produced both from snowmelt and
from summer rainstorms increased measurably. However, this impairment of
watershed protection conditions and attendant increases in runoff and
erosion were only temporary; they had almost returned to the prelogging and
preburning state within four years.
Dyrness (1967) measured the effect of logging operations and broad-
cast burning on disturbance to the soil and litter layer. The proportion
of clearcut watershed burned, and the fraction of the burned area severely
burned varied. The severity of the burn on these watersheds was moderate.
Dyrness and Youngberg (1957) and Tarrant (1956), studying intensity of
slash burning, found the severely burned area to range from less than 3
to approximately 8 percent of the total area burned.
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Packer and Williams (1966) reported that burning drastically re-
duced the proportion of the ground surface protected by plants, litter
and logging residue to less than 50 percent. Overland flow from the
logged-burned areas was from two to several times greater than that from
the unlogged-unburned ones. Soil erosion from the logged-burned plots
averaged 56 Ibs/acre for the first year after burning, but then increased
to 168 Ibs/acre in the second year. None of the unlogged-unburned plots
produced any soil erosion from snowmelt flow during the subsequent years.
Brown and Krygier (1971) showed that after clearcutting and burning,
sediment yields increased about five-fold, and maximum concentration in-
creased from 970 to 7,600 ppm after burning. Fredriksen (1970) reported
that for two years after clearcutting, skyline logging and slash burn-
ing, sediment concentrations were 67 and 28 times greater than those
recorded on an undisturbed watershed during the same periods.
Ralston and Hatchell (1971) studied five watersheds in the southern
United States and found that soil erosion was greater in the areas treat-
ed by prescribed burning, by factors ranging from 7 to 1,500 as compared
to the unturned forests.
Although severe burning may reduce the percolation rate in the soil
and increase surface runoff causing soil erosion, the overall influence
on moisture properties of the soils was concluded to be minor (Tarrant
1956) since severe burns usually cover a very small portion of the total
surface of a slash-burned area.
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REFORESTATION PRACTICES
Reforestation efforts often require some type of site preparation
prior to planting or seeding. The main types of site preparation involve
the use of fire, chemicals and mechanical means. Mechanical methods of
site preparation during the last ten years have included scarification,
stripping and terracing (Packer 1971).
Packer (1971) showed that by creating depressions, machine scari-
fication with debris spread in irregular patterns over the site usually
increases the storage capacity of the land, but seldom increases the over-
land flow and soil erosion hazard. Avoiding excessive scarification will
reduce the impact on the watershed (Rosgen 1973). Packer cautioned that
in preparing sites that slope directly to stream channels, untreated
ground should be left between strip sites and the stream as a buffer to
water and soil movement. Packer also stated that little erosion has re-
sulted from terracing since its first use in southern Idaho.
A U.S. Forest Service task force appraisal (1969-1970) on the Bitter-
root National Forest found few signs of serious erosion on most of the
terraced slopes but cautioned that long-run erosion could not be determined.
Immediate reforestation of the harvested area is usually desirable.
After site preparation, planting is initiated. Hand planting or seeding,
aerial seeding, or auger planting generally entail truck transportation.
Machine planting requires tractors, which introduce some potential for
further erosion if the planting is done a year or more after post-har-
esting stabilization.
Fredriksen (1970) showed the following tabulation (Table 3):
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Table 3. Total understory vegetation cover and exposed
mineral soil after clearcutting of timber and
after burning of logging residue.
(After Fredriksen 1970)
Patch Cut Watershed
Clearcut Watershed
Vegetation Bare Vegetation Bare
Year Condition Cover Ground Condition Cover Ground
Percent Percent Percent Percent
1962 Undisturbed
1963 Clearcut
1964 After burning
1965 Revegetating
1966 Revegetating
1967 Revegetating
70
10
15
49
54
80
3
16
29
28
30
27
Undisturbed 86
Being harvested
Being harvested
Being harvested
After logging 54
Revegetating 76
4
-
-
-
12
54
Burning which followed completion of logging by several months reduced
vegetation cover more on the patch cut than on the clearcut watershed.
In the clearcut watershed, regrowth of fire resistant species during the
three years required to complete logging may have been responsible for
the large cover of vegetation the year following burning (1967).
Revegetation was rapid in the case of both watersheds, but a sizable
proportion of the soil surface remained bare of litter for several years
following burning. On the patch cut watershed, the herb-rich vegetation
established the first two years following burning gradually gave way to
a rapidly expanding cover of shrubs and trees. By 1968, the total
vegetation cover on the clearcuts in the patch cut watershed exceeded
the cover measured in undisturbed forest in 1962.
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A dense cover of vegetation and a nearly complete mat of forest
floor material protects the surface soils from erosion in an undis-
turbed forest. Harvest operations and broadcast burning destroy a large
part of the natural shrub and ground cover. Through reforestation this
cover of vegetation can gradually be restored.
SUMMARY
Studies in the western United States indicate that the erodibility
of forested upland soil is perhaps influenced most by characteristics of
the parent rock. Soils derived from acid igneous rocks tend to be con-
siderably more erodible than soils derived from other parent materials.
The higher the quartz content of the parent material, the greater the
potential erosion hazard of the resultant soil.
Other factors exerting considerable influence include nature of the
vegetative cover, especially as it controls amount of organic matter in
the soil, and climatic conditions as modified by elevation and aspect.
In addition, soil chemical properties undoubtedly influence erodibility
to an as yet unknown extent.
Site erosion potential should influence the selection of the sil-
vicultural system. A suitable silvicultural approach may be anything from
partial thinning to clearcutting and replanting. Although clearcutting
may be suitable on stable sites, selection cutting may be necessary to
provide the soil protection necessary in highly erodible areas.
The factors contributing most to increased soil erosion following
logging are exposure of bare mineral soil and surface soil compaction from
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mechanical disturbance. Studies have generally indicated that clear-
cutting with tractor logging is the most destructive of all the logging
systems (wheel skidding is also often severe) when considering com-
paction of soil. Skyline yarding, in all cases, is less severe than
high lead yarding. Grapple yarding systems are intermediate between
skyline and high lead or jammers, as they combine features of each.
Balloon yarding is substantially less severe than skyline yarding.
Helicopter yarding probably results in the least compaction because it
transports logs free in the air over most of the logged areas.
Broadcast burning also can increase surface erosion, primarily
through the removal of protective vegetation and litter. Sufficiently
hot fires may also cause changes in surface soil properties. Perhaps
the most serious of these are the breakdown of water-stable aggregates
and lowering of organic matter content. The overall influence on moisture
properties of the soils is minor since severe burns usually cover a very
small portion of the total surface of a slash-burned area.
Mass Soil Movement
PHYSIOGRAPHY
Soil mass movements range widely in surface configuration, speed of
movement and volume of material involved. Such movements may take the
form of spectacular landslides and mud flows, or the more subtle, slower,
downward creeping movement of an entire hillside. In terms of principal
processes, however, dominant forms are classified by Swanston (1970, 1974)
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into three groups according to controlling features and principal move-
ment mechanisms. These groups overlap geologic and physiographic
boundaries and are controlled primarily by slope gradient, soil depth,
soil water content and specific soil physical characteristics.
Debris Movements
Mass movements produced by instantaneous failure in shallow residual
or alluvial soils overlying an impermeable surface is the group of most
widespread occurrence. It includes debris slides, debris avalanches and
debris flows. Movement may be triggered by surface loading, increased
soil water levels, or a removal of mechanical support. Debris slides are
the rapid downward movement of unsaturated, relatively unconsolidated
soils and forest debris by sliding or rolling, and are differentiated
from debris avalanches largely by soil water content. Debris flows in-
volve the rapid downslope movement of water-saturated soil and debris
by true flow processes. These types of mass movement are the dominant
process in such diverse areas as the maritime coast of Alaska (Bishop
and Stevan 1964; Swanston 1969, 1970) and the dryer intermountain
areas of Utah, Idaho and Montana (Croft and Adam 1950).
Debris avalanches are also of frequent occurrence in southern
California (Corbett and Rice 1966; Rice, Corbett, and Bailey 1969) dur-
ing the rainy season, and Dyrness (1967) has observed them on the
western flank of the Cascades following the Christmas storm of 1964.
This group is strongly affected by timber harvesting activities. Road
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construction is the most damaging activity, largely through disruption
of the natural balance of forces on the slope by cut and fill activities.
Obstruction of slope drainage and local saturation of roadfills are
also important initiators. Destruction of surface vegetation and
deterioration of anchoring roots by land conversion and clearcut logging
have also been linked with accelerated debris avalanche and debris flow
occurrence (Swanston n.d.).
Creeps, Slumps and Earthflows
Another group of mass soil movements includes soil creep, slumping,
and earthflows resulting from quasi-viscous flow and progressive failure
of weathered pyroclastics, sandstones, and shales. In areas of extremely
deep, cohesive soils, a combination of creep, progressive slumping, and
earthflows may involve an entire watershed. In such areas, slumps and
earthflows occur in zones of concentrated subsurface drainage. Slumping
involves the downward and backward rotation of a soil block or group of
blocks with small, lateral displacement. Earthflows frequently incor-
porate much larger masses of soil which move downslope through a
combination of flows and slumping. Slumping and earthflows are common
to most unstable areas of western North America but are especially
important as an erosion process in the Northern Coast Ranges of
California (Kojan 1967), where large volumes of sediment are being
added annually to some streams by slumping and earthflow activity.
The direct affect of timber harvesting operations on this group
has not yet been clearly identified. Road building is probably the
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most damaging activity. Road construction in active or dormant creep
and slumping areas is likely to accelerate or reactivate the soil mass,
largely through alteration of the balance of forces acting on the slope.
Timber removal probably exerts an impact through alteration of the nat-
ural slope hydrology, producing unstable conditions during critical
storm periods (Swanston n.d.).
Dry Ravel, Dry Creep and Sliding
The remaining group includes dry ravel or dry creep and sliding of
coarse, cohesionless materials on steep, sparsely vegetated or recently
denuded slopes. This is a common erosion process on unvegetated over-
steepened slopes throughout the mountainous region of the western states,
caused by loss of frictional resistance between individual soil particles
due primarily to freeze and thaw and wetting and drying cycles. In areas
characterized by steep slopes, coarse textured soils, and extended summer
droughts it may be a particularly important process. It constitutes the
dominant process of soil mass movement during the dry summer season in
the San Gabriel Mountains of southern California (Krammes 1965). This
type of movement involves the mechanical sliding or rolling of indi-
vidual particles or aggregates under the direct influence of gravity.
Principal effects of timber harvesting activities on this group
are removal of surface vegetation and construction of artificial em-
bankments and road, exposing bare mineral soil to rapid weathering and
cycles of freezing and thawing and wetting and drying.
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SLOPE STABILITY
Two main variables should be considered in preparing a classifi-
cation of mass movement (Varnes 1958): (l) the type of material
involved, which usually is apparent on inspection or with preliminary
borings and (2) the type of movement, which usually can be determined
by a short period of observation or by the shape of the slide and
arrangement of debris.
Varnes (1958) grouped the variables affecting slope stability into
(1) those tending to reduce shear strength and (2) those increasing
shear stress ( Table 4- ). This method was used by Bishop and Stevens
(1964) to examine factors causing landslides in southeast Alaska.
Factors Influencing Shear Strength
The initial composition and structure of parent material plays an
important role in shear strength. Glacier-worn granite slopes fre-
quently offer little support for soil or vegetation. Weak geologic
structure, bedding structure, compacted glacial till in a wetted state
and metamorphics are critical factors in some areas.
Fracturing and weathering characteristics of rock also may produce
a weak foundation for the soil mantle. Some areas with diorite rock
have weathered sufficiently to produce a thin mantle of small angular
blocks overlying the unweathered surface. Soil filtering into these
fissures gradually forces these blocks apart by freezing and thawing.
This action, combined with gravity acting on steep slopes, produces a
soil mantle weak in shear strength. Granites that disintegrate into
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TABLE 4
FACTORS CONTRIBUTING TO INSTABILITY OF EARTH SLOPES
(After Varnes 1958) Taken from: Gray 1969
Factors that Contribute to High Shear Stress
Factors that Contribute to Low Shear Strength
A. Removal of Lateral Support
1. Erosion - bank cutting by streams and
rivers
2. Human agencies - cuts, canals, pits, etc.
B. Surcharge
1. Natural agencies - wt of snow, ice and
rainwater
2. Human agencies - fills, buildings, etc.
C. Transitory Earth Stresses - earthquakes
D. Regional Tilting
E. Removal of Underlying Support
1. Subaerial weathering - solutioning by
groundwater
2. Subterranean erosion - piping
3. Human agencies - mining
F. Lateral Pressures
1. Water in vertical cracks
2. Freezing water in cracks
3. Swelling
<4. Root wedging
A. Initial State
1. Composition - inherently weak materials
2. Texture - loose soils, metastable grain
structures
3. Gross structure - faults, jointing, bedding
planes, varving, etc.
B. Changes Due to Weathering and Other Physico-
Chemical Reactions
1. Frost action and thermal expansion
2. Hydration of clay minerals
3. Drying and cracking
4. Leaching
C. Changes in Intergranular Forces Due to Pore Water
1. Buoyancy in saturated state
2. Loss in capillary tension upon saturation
3. Seepage pressure of percolating groundwater
D. Changes in Structure
1. Fissuring of preconsolidated clays due to
release of lateral restraint
2. Grain structure collapse upon disturbance
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soils that are high in sand content and low in shear strength occur on
the mainland and parts of some islands in southeast Alaska (Bishop and
Stevens 1964).
Varnes lists three ways in which pore water may reduce soil shear
strength:
l) Buoyancy in the saturated state decreases effective
intergranular pressure and friction.
2) Intergranular pressure due to capillary tension in
moist soil is destroyed upon saturation.
3) Seepage pressures of percolating groundwater result from
viscous drag between liquid and solid grains,
In cohesionless soils, significant pore pressures usually are not
developed. A compacted cohesionless soil tends to increase in volume
as it shears. Volume increase is opposed by a saturated but draining con-
dition. Hence, a resistance to shear is developed. In contrast to
cohesionless soils, cohesive soils consistently lose shear strength
with addition of water, despite a complex and variable relationship to
soil water.
Timber removed from a cohesionless soil will cause a reduction in shear
strength in proportion to the change in weight because there is a change in
the force normal to the slide plane.
Gradual deterioration of the root networks follows the timber harvest.
The tenacious hold of root hairs and fine roots to soil particles is grad-
ually lost. Loss of continuity in the network of tree roots near the soil
surface may weaken the soil mantle. With a discontinuous root network on
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the slopes, strong anchor points that resist shear cannot absorb additional
shear stress from weakened adjoining areas.
Factors Influencing Shear Stress
Glaciation is evident throughout some parts of the Pacific Northwest,
in particular the Puget Sound Area, northern Idaho and Alaska. During
the latest glacial period, glaciers carved steep U-shaped valleys. Erosion
has not acted long enough to moderate the glacial slopes to more stable
forms. Consequently, the soils on which many logging operations are con-
ducted are derived from glacial deposits laid down on very steep or over-
steepened slopes. Earthquakes, not uncommon in some parts of southeast
Alaska, may trigger unstable slopes to move.
Faulting or uplifting can tilt the earth's surface, contributing to
formation of oversteepened slopes. Faulting or uplifting may also steepen
stream gradients. Tributary torrent streams may then produce and main-
tain oversteepened ravine slopes. Heavy rains develop shear stresses with-
in the soil profile by adding the weight or driving force of water to
the soil mantle and vegetation. The weight of vegetation is a significant
part of the shearing force in the soil mantle.
Gray (1969) listed the possible ways vegetation might affect the
slope stability as follows:
l) Mechanical reinforcement from the roots. Indirect evidence re-
ported in the literature suggests that this may be the most
important effect of trees on slope stability. Presumably deep-
rooted species of trees or woody shrubs whose roots penetrate
through the soil mantle to bedrock would enhance stability the
most. Conversely, removal of such a vegetal cover with subse-
quent rotting and deterioration of the roots would have the
most serious consequences.
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2) Surcharges. At first glance this would appear to increase
shear stress, but the effect is largely negated by a concom-
itant increase in shear strength due to the confining effect
of the surcharge. Furthermore, Bishop and Stevens (1964)
estimate that the surcharge due to the weight of the forest
(spruce and hemlock) amounts to only 50 psi. This is equiv-
alent to a layer of soil only six inches thick. Although
the surcharge will have little effect on the calculated fac-
tor of safety, it will affect creep rates to some extent.
3) Wind throwing and root wedging. Strong winds blowing para-
llel to the slope will exert an overturning moment on the
trees. This can lead to so-called wind throwing of trees
which creates localized disturbances in the soil mantle.
Wind throwing is a fairly common occurrence in some forests,
but it normally affects only aged and diseased trees. The
total down slope force created by a wind blowing through a
forest and hence its overall effect on slope stability has
never been evaluated. The effect of root wedging, an alleged
tendency of roots to penetrate a soil, thereby loosening
it up or opening cracks and fissures, likewise is presently
unknown. Judging by evidence reported in the literature,
particularly the observation by Bishop and Stevens (1964),
the beneficial effects of root systems on slope stability
far outweigh any possible adverse effects.
4) Modification of soil moisture distribution and pore pressure.
Trees transpire water through their leaves and this in turn
depletes soil moisture. Soil moisture depletion produces
negative pore water pressure, which as seen previously is
conducive to slope stability. A forest can also intercept
moisture either in the crowns of trees or in the ground
litter.
Gray developed three principal equations that can be used to deter-
mine the influence of a key variable, such as piezometric level on slope
stability. These three equations concern, (l) factor of safety of the
slope, (2) allowable height of piezometric level, and (3) the maximum
rate of planar depth creep. Gray concluded that as the piezometric level
approaches the surface of the soil layer, the creep rate accelerates
markedly. Swanston (1967) also had good results in calculating the
critical piezometric level in a drainage basin in southeast Alaska.
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Dyrness (1967) showed the relationship between the occurrence of
mass movement events and certain site characteristics in the H.J. Andrews
Experimental Forest.
FOREST OPERATIONS
The primary effect of timber harvesting on the accelerating soil mass
movements is a lessening of the mechanical support of the slope, chiefly
by roadbuilding, logging and slash burning.
Roadbuilding has been identified as the greatest single cause of
recent soil mass movements in the western states (Swanston and Dyrness
1973). This subject is explored extensively in a recent report by the
EPA (1975) but a few points will be mentioned here. Road construction
disrupts the basic equilbrium of steep slope forest soils through alter-
ation of slope drainage, slope loading, and slope undercutting. The
first includes interception and concentration of surface and subsurface
flow by ditching, bend cutting and massive roadfills. This encourages
saturation, active pore water pressure development and increased unit
weight in road prisms, side-cast materials and soils upslope and down-
slope from the road cut. Poor drainage and plugged culverts can greatly
magnify these problems by ponding water on the inside of the road. Slope
loading by massive fill and side-casting greatly increases the weight of
the soil material, resulting in increased gravitational stress along the
slope below the road. Slope undercutting by benching along on over-
steepened slope removes support for the upslope soil.
Cutting of trees alone does not greatly increase surface soil erosion
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as long as ground cover is maintained, however; on steep slopes cutting
may cause debris accumulation and loss of the mechanical support from
rooting structures of trees and other vegetation. Several investigations
in the western states have linked increased occurrences of debris flows
to logging after high-intensity storms.
The deterioration of stabilizing root systems seems to play an
important part in this increased activity. Accumulation and flow of
debris in steep ravines, both logged and unlogged, has also been cited
as a major factor in mass soil movements (Swanston and Dyrness 1973).
Bishop and Stevens (196-4) have shown a direct correlation between
timber harvesting and accelerated soil mass movements in Alaska follow-
ing heavy rains in the fall of 1961. More detailed work in this area
by Swanston (1967, 1969, 1970) has shown that sections of almost every
logged slope exceed that natural angle of stability of the soils (+34°).
The majority of debris avalanches and flows developed on slopes greater
than 34° and are especially frequent around a critical angle of 37°.
Above this critical contour sliding is imminent, with the destruction or
disruption of any cohesive forces acting to hold the soil in place.
Below the critical contour is a zone of decreasing instability.
A study by Rothacher and Glazebrook (1968) found that in the national
forest of Region 6 on highly erosive granodiorite soils, slopes over 40
percent cannot be clearcut without considerable soil loss from numerous
slides.
Dyrness (1967) investigated accelerated soil mass movements on the
west flank of the Cascade Range following heavy rains in the winter of
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1964-65. He reported that out of 47 recorded debris avalanches, debris
flows, earthflows and slumps, 72 percent were directly associated with
roads and 17 percent with logging.
Kittredge (1948) observed that in the coast ranges near San Francisco
many slides occur in wet years on the heavily grazed, grassland-covered
clay soils, but that similar slides do not occur on the same soils in
the eucalyptus plantations more than 25 years old. Gray (1969) con-
cluded that there was a definite relationship between clearcutting and
mass soil failures and pointed out that "there has been no rational at-
tempt to predict what will be the factor of safety of a natural slope
against sliding, before and after clearcutting."
Croft and Adams (1950) attributed increases in soil mass movement
following high-intensity storms in the Wasatch Mountains to loss of me-
chanical support by root systems of trees and plants, chiefly by logging
and burning. They concluded that before modern day land use landslides
were rare and possibly absent from their study area.
Fire is an effective management tool in conjunction with logging
slash and also to prepare the site for planting or seeding. It is
an effective agent for accelerating dry creep and sliding and may
indirectly influence soil mass movement on already unstable slopes. At
its worst fire removes or destroys all protective vegetation. This can
lead to mechanical unravelling of the slope and progressive deterioration
of root systems. In southern California, as well as in the Wasatch
Mountains of Utah, fire has been directly linked to massive increases
in dry ravel or debris avalanching (Swanston and Dyrness 1973).
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Krames (i960, 1965) reported that in October 1959, a wildfire swept
through the Los Angeles River watershed and debris movement began al-
most immediately after the fire passed. Great quantities of debris
moved downslope and into stream channels. The increase in the production
of sediment by mass soil movement was from 10 to 16 times greater than
normal.
Corbett and Rice (1966), and Rice, Corbett, and Bailey (1969) re-
ported that soil slippage was increased by brush conversion from native
chaparral vegetation to grass at the San Dimas Experimental Forest,
California. The converted area contained about five to seven times as
many soil slips as the control area.
SUMMARY
High soil-moisture content and steep slopes are common to most of
the recent accelerated mass movements of soil on forest lands. Local
bedrock type, climate and basic soil characteristics determine the in-
dividual failure mechanisms. External factors, including parent material
structure and rooting structure of trees and understory vegetation, af-
fect stability conditions on some sites.
The site characteristics which control mass soil movement include
particle size distribution, angle of internal friction, soil moisture
content and angle of slope. Shallow coarse-grained soils low in clay-
size particles have little or no cohesion, and frictional resistance
determines the strength of the soil mass.
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Parent material structure is a critical factor in the stability of
many shallow-soil slopes. Highly jointed bedrock slopes with principal
joint planes parallel to the slope, and sedimentary rocks with bedding
planes parallel to the slope, provide little mechanical support. They
create avenues for concentrated subsurface flow and active pore water
pressure development as well as ready-made zones of weakness and poten-
tial failure surfaces independent of the overlying material.
Vegetative cover in general helps control the amount of water reach-
ing the soil and the amount held as- stored water. Root systems of trees
and other vegetation may also increase shear strength in unstable soils.
This is particularly true when roots anchor through the soil mass into the
parent material, and provide continuous long-fiber cohesive binders to the
soil mass proper and across local zones of weakness within the soil mass.
In some extremely steep shallow soils in the western United States, root
anchoring may be the dominant factor in maintaining slope equilibrium of
an otherwise unstable area.
The three major types of mass soil movements are:
1) Debris slides, debris avalanches and debris flows, produced
by instantaneous failure in shallow soils overlying an im-
permeable surface. These soils are usually of coarse texture
and low in clay content.
2) Creep, slumps and earthflows, resulting from quasiviscous
flow and progressive failure of deeply weathered materials.
Speed of movement ranges from a barely perceptible creep to
high velocity slumps and earthflows.
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3) Dry ravel, dry creep and sliding, involving downslope move-
ment of single particles and thin sheets of coarse, cohesion-
less material on steep sparsely vegetated slopes.
Since roads are often an important factor in causing mass movement,
the problem is to determine means of minimizing their effect. The most
obvious means is to reduce road mileage to an absolute minimum. In
steep, mountainous terrain, this may be done by the use of skyline and
possibly balloon logging methods. In many areas, it is possible that
improvements in road location may appreciably reduce the frequency of
mass soil movement. Unstable soils and land forms should be identified,
and the route selected should avoid these areas.
Channel Erosion
Stream sediment is generally assumed to be derived from two erosional
processes: surface erosion and channel erosion. Mass soil movement is
considered by some as a third form of erosion. The total sediment load
for a stream is recognized to be composed of suspended material or wash
load, usually derived from surface erosion, and bed load, primarily der-
ived from channel erosion. The total amount of sediment in a stream
depends on physical characteristics of the watershed and climatic variables.
The quantity of suspended material in a stream at any time primarily
depends on the rate at which fine particles become available from the
watershed. It is a function of such factors as intensity, quantity and
distribution of rainfall; soil type; vegetation cover; and relief.
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Bed load in a stream is mainly derived from gully erosion, stream-
bank erosion and channel degradation. The quantity of bed load in a
stream at any time depends on the hydraulic characteristics of the flow
and soil surface (Leaf and Henderson 1966).
Vegetation may protect a streambank in at least three ways (Parsons
1963). Perhaps the most important of these is the reduction of water
speeds and tractive forces at the soil surface to a value below that re-
quired to entrain particles. Second is the protection given to the bank
material as a buffer against ice, logs and other transported materials.
Third, close-growing vegetation will contribute to bank stability, within
a narrow range of conditions, by inducing deposition. Subsequent to a
rare flood that has caused damage but not complete destruction to the
vegetative cover, the deposition that occurs in minor floods helps to
maintain the bank.
Logging debris in the streams can divert stormflow from the channel
to the road and/or the streambank, resulting in excessive erosion. Rice
and Wallis (1962) reported that 13 percent of 3,000 feet of stream
channel measured showed severe logging disturbance. In most cases, bull-
dozers had scoured or filled the former channel. Buffer strips of
vegetation were found to be effective in reducing logging debris in the
stream channel and stabilizing the streambanks.
Suspended Organic Material
Several forest practices can introduce living and dead particles of
vegetation into streams. This organic debris is also contributed nat-
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urally and through the stream system in somewhat the same way as the in-
organic materials, such as silt or gravel. Coarse debris of this type
may have a relatively long period of residence in or near the channel
awaiting slow decay and weathering. Some of it moves much more rapidly
through the system and some is incorporated in the beds and banks of the
channels. In all cases the material eventually decays. This decay of
materials can degrade water quality by decreasing dissolved oxygen in
the water and by releasing organic solutes during leaching.
Lammel (1972) described the natural debris accumulation in five small
streams in western Oregon. He found that total residue increased after
clearcut logging in all streams except one with a wide (50 m) buffer strip.
Clearcutting increased residue volume 1,2 times over what it had been
prior to logging near the stream with a light buffer strip. Residue vol-
ume was about 3.3 times greater along a stream where conventional high
lead logging was used with no buffer strip.
Meehan et al (1969) noted that the number of large pieces capable
of jamming two Alaska streams increased during four years of patch cutting.
One watershed was about 20 percent logged and debris in the stream channel
increased by 23 percent. In the second watershed, about 25 percent of the
area was logged and debris in the stream channel increased by 60 percent.
Debris in an unlogged watershed nearby increased about 7 percent during
the same period.
Directional falling of trees can prevent debris accumulation in the
streams. Froehlish (1973) reported that logging, especially at the tree
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falling stage, can produce large changes in debris loads. When the dir-
ection of falling was controlled by tree pulling, the quantity of mat-
erial reaching the channel was reduced to a very small amount. On steep
and broken ground tree pulling can be used to advantage. Buffer strips
were found to be effective barriers even when they were not continuous
or of large widths.
Burwell (1970) also noted that falling trees uphill using a truck-
mounted donkey and climber to attach the line, prevents breakage and
distributes limbs and tops on slopes instead of in stream bottoms. Sav-
ings such as increased safety, lessened breakage, reduction of slash to
eliminate burning and enable quicker regeneration, and reduction of ex-
pensive creek cleaning may more than offset initial additional costs.
Log or debris dams are common in the salmon spawning streams of
southeast Alaska, and often affect streamflow and streambed topography
(Helmers 1966). Log-debris dams intensify streambed instability, es-
pecially during floods, and can reduce salmon production in otherwise
favorable areas by increasing gravel movement which reduces egg and
larvae survival. Debris dams may also affect spawning salmon as a mig-
ration barrier. Chapman (1962) reported that when debris was not removed
from a stream after logging, spawning salmon decreased by 75 percent
because of the migration barrier.
In summary, logging, especially at the tree falling stage, can pro-
duce large changes in debris loads. Care exercised during logging to control
the direction of falling and protect streams can reduce debris accum-
ulation in the streams . Buffer strips have been found to be effec-
tive debris barriers.
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Dissolved Organic Materifd
The storage of logs in freshwater streams as well as saltwater
estuaries and bays can result in the deposition of large quantities of
bark and wood residue on the bottom near log dump sites and log raft
storage areas. In addition to bark and wood accumulation, leachates
diffuse out of the logs into the water. Some of the leachates are toxic
to fish and other aquatic organisms. The taste, color and odor of the
water can also be degraded due to high concentrations of organic solutes.
The quantity of bark lost from logs during handling in the water is
highly dependent on the particular activity (Hansen 1971). As shown
in Table 5, free-fall dumping of Douglas-fir logs resulted in an average
bark loss of 17 percent. Vertical hoisting removed 8 percent of the
bark. But during rafting and storage only 5 percent of the bark was lost.
Similar studies of ponderosa pine indicated that cumulative losses for
both unloading and storage were approximately 6 percent (Hansen 1971).
Although limited data is available it has been suggested that losses of
bark from bundled logs is likely to be lower than that of non-bundled
logs because of the reduction of log surface area exposed to abrasion
(Hansen 1971). It is anticipated also that bark losses may be larger
for storage areas subject to strong waves or current action in contrast
to storage facilities in sheltered waters.
The rate at which bark sinks when placed in water is governed by
bark density, water absorption rate and particle size. Laboratory data
collected by Schaumburg (1970) indicated that small particles of ponderosa
pine bark tends to sink faster than the larger particles. Also, in
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general, ponderosa pine bark tends to sink faster than Douglas-fir bark.
The area of the bottom covered by bark tends to be highly variable
depending on the method used for dumping, the length of time the dump
site is in use and the degree of flushing action. Pease (1974) reports
that bark may cover the bottom within a radius of 50-200 feet of the
dump site. Currents can result in bark being deposited on beaches where
its aesthetic impact is often significant.
Table 5. Douglas-fir bark loss during log handling operations.
(After Hansen 1971)
Activity
Land Handling and Transport to
Dump Site
Free-Dumping
Vertical Hoisting
Rafting and Storage
Average Percent Bark Loss
18 - 25
17
8
5
The State of Alaska (1971) has inventoried all log handling and stor-
age facilities in Alaska, and Ellis (1973) has reported on inspections of
log dump facilities located in Alaska. Facilities examined included sale
area dump sites, storage areas for log rafts, mill storage, and sorting
sites. Several of the sites in Alaska had been used intensively for two
to five years and then abandoned. Others had been in continuous use for
several years. The quantity of logs dumped and handled at the various
sites inspected ranged from 10 to well over 150 million board feet.
With but few exceptions, large quantities of bark, fragments of wood,
steel bands, and broken sections of wire rope on the bottom were found in
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the immediate vicinity of the dump site. The area covered by debris
tended to be highly variable, but in general, the concentration de-
creased at locations further removed from the dump site. In areas
characterized by large accumulation of bark and debris, the popu-
lations of marine organisms were considerably smaller than those of
adjacent areas free of debris. Somewhat lower quantities of debris
were present at dump sites subject to the flushing action of moderate
tidal currents. A wide variety of marine organisms were found to re-
side in areas free of debris.
Hansen et al (1971) showed that log debris from rafting and dump-
ing sites caused physical damage to estuarine habitats in Alaska. They
found that the bottom of a dump site, which had been abandoned for
seven years, was covered with two feet of decomposing organic debris.
Marine animals were scarce there but abundant in adjacent areas.
The biodegradation of bark on the bottom in the vicinity of log
dump sites results in the consumption of oxygen from overlying waters
(Schaumberg 1973; Pease 1974). The increased oxygen demand required for
bark decomposition is reported to range from 30 to 70 percent greater
than that of areas free of large deposits of bark (Hansen 1971). Oxygen
concentrations below 6 rag/liter, have been reported in log storage
waters, particularly those which have been used for an extended period
of time and not subject to vigorous flushing action (Schaumberg 1973;
Pease 1974). Due to the complex chemical composition of bark and to the
low water temperature at many storage sites, the rate of bark decomp-
osition is low at many dump sites in the Pacific Northwest.
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Schaumberg (1973) reports that leachates from logs in water storage
contains mostly organic substances which exert both a chemical and bio-
chemical oxygen demand. The leachates are primarily tannins and lignin-
like substances which impart a brownish color to the receiving water.
The added color can be aesthetically undesirable.
Narver (1970) concluded that soluble organic materials such as
woodsugars, tannins, and lignin-like substances leached from logs can
produce a considerable COD (chemical oxygen demand) along with yellow and
brown colors in water. Ponce (197-4) noted that the concentration of
organic material needed to produce toxic effect was so high that oxygen
depletion probably would be responsible for death of guppies and steel-
head trout fry long before the leachate had effect.
Schaumberg (1973) has reported on the results of laboratory studies
of the leaching of sections of both ponderosa pine and Douglas-fir logs.
His data indicates that more color-producing and soluble organic sub-
stances are produced from ponderosa pine logs than from comparable Douglas-
fir logs. When held in non-flowing water, leachates emerged at a rel-
atively constant rate for a period of up to 80 days. When immersed in a
flow-through system, however, the rate of leaching was substantially
higher at the outset but declined after 20 to 30 days. No studies were
conducted on high rate flow-through systems characteristic of some streams
and estuaries.
Pease (1974) reported higher leachate concentrations and lower levels
of dissolved oxygen for log storage sites in Alaska. Higher leachate
concentrations were observed at sites subject to low rates of tidal
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flushing action and longer periods of log storage. Also, leachate concen-
trations tended to be highest in layers of water within the interspaces of
log rafts.
A study by Graham (1970) on the quantity and properties of substances
leached from logs floating in water and the rate of leaching of these sub-
stances, reported that ponderosa pine logs contributed measurably greater
quantities of soluble organic materials and color-producing substances than
Douglas-fir logs. Leaching rate appeared to be affected by the concentra-
tion of soluble organic materials in the stagnant holding water. In flowing
water, the leaching rate was nearly constant. Extrapolation of laboratory
test data to field conditions resulted in a prediction that 800 pounds of
COD per day would be contributed by approximately eight million board feet
of floating logs to a typical log storage facility.
Schaumberg (1973) reports that leachates are relatively non-toxic to
salmon and trout fry for exposure periods of up to four days. Pease (1974)
reports that it required 12 hours for the most toxic wood leachates (spruce)
to kill one-half of the test fish. As indicated above, leachate concentra-
tion tends to be highest in localized areas in close proximity to log rafts.
As Pease (1974) points out, it is doubtful that mature fish would remain in
an area of high leachate concentration for a period of 12 hours before de-
tecting the higher concentration and low oxygen concentration and swim away.
Consequently, although log leachates are toxic to fish, it is doubtful un-
der normal circumstances that large kills of mature fish are to be expected.
Leachates, on the other hand, can reach more highly-concentrated lev-
els near the bottom where bark and wood fragments concentrations are higher.
In such circumstances they have an impact on the number and diversity of
benthic organisms (Pease 1974). Log storage in reproduction areas
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or where the benthic zone is critical at some stage of an organisms life-
cycle, can result in significant adverse effects.
Atkinson (1971) studied the acute toxicity of Douglas-fir, ponderosa
pine and hemlock logs to Chinook salmon and rainbow trout in fresh water.
He found that hemlock leachate was not measurably toxic to trout and
salmon fry after a 96-hour period. His leachate solution was composed
from water soaked with a small hemlock log for several days. He did find
that 20 percent by volume of Douglas-fir leachate was toxic after 96 hours.
Buchanan (1970) tested the toxicity of spruce bark, hemlock bark
and barite ore to Dungeness crab and shrimp larvae. He found that spruce
bark had the highest toxicity of these three materials tested. He de-
fined EC^Q as the concentration of barite ore, hemlock bark or spruce
bark that produced a designated effect on 50 percent of the test animals.
When cessation of swimming was used as a criterion of toxic effect, the
24-hour ECc0's were 43 and 190 mg/1, respectively. Hemlock bark proved
to be the least toxic.
Buchanan and Tate (1973) tested the acute toxicity of sitka spruce
and western hemlock bark to pink salmon fry, pink shrimp adults and larvae,
and Dungeness crab larvae. The 96-hour EC^Q'S for spruce bark leachates
to larval shrimp, adult shrimp and larval crabs, with death as the cri-
terion, were 415, 205 and 330 mg/1, respectively. Using loss of swimming
as the criterion of toxic effect, the 96-hour EC50's for larval shrimp
and larval crabs were 155 and 225 mg/1, respectively. Spruce bark part-
icles were found to be two to six times more toxic than leachates to
shrimp larvae.
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Dissolved Inorganic Material
Soil properties and vegetative characteristics that influence the
hydrologic stability of the forest floor can be altered when forests are
clearcut and the logging residue burned. An immediate effect of such
treatment is the baring of the soil surface, thereby making it vulnerable
to the impacts of overland flow and raindrop splash during storms. The
interception and shading effects of the forest cover are negligible for
several years following clearcutting and burning.
As water runs over the surface of the soil, plant nutrients are
dissolved and removed from the site. In addition, the soil which is
eroded includes attached nutrients, which are also lost from the site.
The amount of the surface runoff, the amount of eroded material or sed-
iment produced by this runoff, and nutrient loss must be considered when
evaluating the effects of clearcutting and burning forest lands.
Slash, a common by-product of a clearcut logging as well as other
timber harvesting techniques, is sometimes deposited directly in stream
channels. In general, the large material is removed or disposed of.
Finely divided material, however, such as needles, leaves and broken twigs,
may remain. This material can be responsible for a reduction in dissolved
oxygen (DO) concentration (Narver 1971).
Chemical nutrients in the stream are but one aspect of the interface
between the forest and the stream. The utilization of chemicals by
stream biota is undoubtedly also related to other changes in the stream
following timber harvest. Additional solar energy adsorbed by the stream,
resulting from reduction of cover over the stream increases the production
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of aquatic plants. The structure of the community of organisms and their
metabolic rate may change due to elevated stream temperature. Sedimen-
tation and organic materials may alter the nutrient supply of the stream.
Decomposition of organic materials deposited in the stream utilizes dis-
solved oxygen from the stream water—sometimes reducing the concentration
to levels critical for the survival of aquatic organisms.
NUTRIENTS
Cycling of nutrient elements between atmosphere, plants, soil and
water is one of the most important processes in a forest ecosystem. The
nutrient cycling process may be altered by logging and burning (Fred-
ricksen 1971) or by complete destruction of the vegetation covering a
watershed (Likens et al_ 1970). The degree to which the nutrient cycling
process is disrupted depends on the nature of the soil and how it was
affected by the treatment, the soil microflora and fauna, the degree of
vegetation removal and the precipitation pattern (Brown et_ al^ 1973).
Following logging, nutrient concentrations in stream water are
governed by three characteristics that describe a watershed, i.e., soil,
vegetation and climate. Vegetation characteristics such as species com-
position influence the rate of nutrient uptake, and the rate of revege-
tation after a watershed disturbance influences the rapidity with which
recycling begins and nutrient loss diminishes. Several characteristics
of the soil such as porosity and texture, determine the pathway and
the rate of water movement in or over soil. These same characteristics
also influence soil credibility and the tenacity with which the nutrients
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are held in the soil matrix. The form, chemistry, amount and intensity
of precipitation influence the ra'te of leaching.
Clearcutting tends to deplete the nutrients of a forest ecosystem
by:
1) reducing transpiration and thereby increasing the amount
of water passing through the system;
2) simultaneously reducing root surfaces capable of removing
nutrients from the leaching water;
3) removal of nutrients in forest products;
4) adding to the organic substrate available for immediate
minerali z at i on;
5) in some instances, producing a microclimate more fav-
orable to rapid mineralization.
These effects may be significant with other types of forest harvesting,
depending on the proportion of the forest removed. Loss of nutrients
may be accelerated measurably in cutover forests where the soil micro-
biology leads to an increase of dissolved nitrate in leaching waters
(Bormann et_ al_ 1968).
Clearcutting on sites having one or more of the following soil
features may be particularly vulnerable to excessive nutrient losses:
shallow to bedrock; thin layers of unincorporated humus overlaying in-
fertile mineral horizons; and coarse skeletal soils on steep terrain
(Pierce et_ al_ 1972).
Major losses of nutrients from terrestrial ecosystems result from
two processes: (l) particulate matter removal accomplished by erosion
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and transportation in surface drainage water, and (2) solution removal
accomplished by dissolution and transportation of solutes by surface and
subsurface drainage water (Bormann et_ al 1969).
The vegetation on a small watershed-ecosystem in Hubbard Brook Experi-
mental Forest was cut in order to determine the effects of removal on nutrient
cycles. Bormann et_ al_ (1968), reported that relative to undisturbed eco-
systems, the area denuded exhibited accelerated loss of nutrients: nitrogen
lost during the first year after cutting was equivalent to the amount annually
turned over in an undisturbed system, and losses of cations were 9,8,3 and
20 times greater for Ca++, Mg++, Na+ and K+, respectively, than similar losses
from comparable disturbed systems.
Large increases of nutrient levels in a small stream in the Hubbard Brook
Watershed after forest cutting and three successive summers of herbicide
application were reported by Likens et_ al_ (1970). The results of this study
while in an artifically created situation have raised several questions about
the impact of clearcutting on both productivity of forest soil and the quality
of water from clearcut watersheds. Nitrate concentrations were 41 fold higher
than the undisturbed condition the first year and 56 fold higher the second
year. The nitrate concentration in stream water exceeded, almost continuously,
the health levels recommended for drinking water. Sulfate was the only major
ion in stream water that decreased in concentration after deforestation.
Average stream water concentration increased by 417 percent for Ca++, 408
percent for Mg , 1,558 percent for K+, and 177 percent for Na+ during the two
years subsequent to deforestation.
Reinhart (1973) reported that for the two years following clearcutting
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in New Hampshire, about 85 Ibs/acre of nitrate-N and 80 pounds of Ca
were discharged in streamflow. Losses after cutting amounted to about 2
percent of the N capital available in the ecosystem and -4 percent of the
Ca. Losses in the central and southern Appalachians were far less. The
difference between the New Hampshire and other results seems to be as-
sociated with the nature of podzol soils. Pierce et_ al_ (1972), noted
that substantial changes in ion concentration were found in all streams
draining clearcut areas in the White Mountains of New Hampshire. Indi-
cations are that clearcutting on shallow, infertile, podzolized soils can
result in nutrient losses for several years after exposure.
Fredriksen (1971) studied the nutrient release after clearcut logging
of an old-growth Douglas-fir forest in the Oregon Cascades. Following
timber harvest and slash burning, loss of nutrients cations increased 1.6
to 3.0 times the loss from the undisturbed watershed. A surge of nutrients
that followed broadcast burning contained concentrations of ammonia and
manganese that exceeded federal water quality standards for a period of 12
days. Annual nitrogen loss following burning averaged 4.6 Ibs/acre and
53 percent of this was organic nitrogen contained in sediment. Inorganic
nitrogen dissolved in the stream made up the remaining part. Annual loss
of nitrogen from the undisturbed forest was very small: 0.16 Ibs/acre.
Later, Fredricksen (1972) noted that even though 170 and 135 cm of water
passed through this Douglas-fir ecosystem, for the two years of the study
period the ecosystem conserved nitrogen effectively as indicated by an
average annual dissolved nitrogen outflow of 0.5 Kg/ha from an annual
average input of 1.0 Kg/ha in precipitation. There was a small annual
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net loss of phosphorus (0.25 Kg/ha). Average annual net losses of calcium,
sodium, magnesium and potassium were: 47, 28, 11, and 1.5 Kg/ha, re-
spectively. Silica loss of 99 Kg/ha-yr was the largest of all constituents
and came entirely from within the forest system.
Brown, et_ al_ (1973), studied the effect of clearcut logging and
slash burning on nutrient losses from small watersheds in the Oregon
Coast Range for two years before and for two years after logging. No
change in the concentration or yield of nitrate nitrogen, phosphorus or
potassium was observed after logging in a patch cut watershed. In a
clearcut logged and burned watershed, maximum nitrate nitrogen concentra-
tions increased from 0.70 to 2.10 mg/1. Nitrate nitrogen concentrations
returned to prelogging levels by the sixth year after logging. Yield
of nitrate nitrogen increased from 4.94 to 15.66 Kg/ha the first year
after treatment. Potassium concentration increased markedly after burn-
ing from about 0.60 to 4.40 mg/1 but returned to prelogging levels within
two months. Phosphorus concentrations were unchanged.
In the larch and Douglas-fir forest type of western Montana, water-
sheds were clearcut and the logging debris broadcast burned (DeHyle and
Packer 1972). They report that logging and burning temporarily impaired
watershed protection by increasing overland flow and soil erosion. The
soils were developed from the Belt formation and occurred on gentle to
steep slopes. Vegetal recovery returned conditions to near prelogging
status within four years. The increase in plant nutrient losses, which
occurred in the sediment and the overland flow during the denuded period,
represented a small fraction of the available nutrients on these sites.
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Marks and Bormann (1972) found that forest regrowth tended to min-
imize nutrient losses from the ecosystem and thus promote "a return to
steady-state cycling characteristic of a mature forest." They sampled
stands of pin cherry which revegetated the site following clearcutting
and found, among other things, that the standing crop at age 14 held
about 180 Ibs/acre of N and 160 pounds of Ca. They estimated that the
annual uptake of N in the 4- and 6-year old stands was about 50 percent
greater than in the more-or-less mature, undisturbed ecosystem at Hub-
bard Brook. Perhaps equally important is the shading of the forest floor
by new vegetation and the resulting decrease in surface temperature and
rate of organic matter decomposition.
In summary, nutrient losses from most of the forest of the North-
west after clearcutting appear to represent minor short-term problems,
both in terms of the terrestrial and aquatic systems. Rapid revegeta-
tion and heavy deep soils tend to preclude significant nutrient loss.
However, where (l) shallow or erosive soils exist, (2) revegetation is
not rapid, or (3) the impacts become cumulative, the effects, particularly
those associated with water quality, could be significant.
OXYGEN
The character and productivity of aquatic ecosystems in streams is
significantly influenced by the concentration of dissolved oxygen (DO).
Several forestry practices change the DO concentration, particularly
in small streams, either directly or indirectly. Changes in stream
temperature brought about by the removal of streamside vegetation,
139
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increases in nutrient concentrations as a result of harvesting, and the ac-
cumulation of logging debris in the stream are some of the more important
factors which effect DO concentration.
Dissolved oxygen, like temperature, is a primary regulator of biologic
activity in an aquatic ecosystem. Dissolved oxygen present at any time
in a stream is a function of the water temperature (Churchill et_ al 1962),
which limits the saturation concentration; and channel characteristics,
such as slope, roughness and cross-section, which control the rate of
oxygen exchange between water and air.
Aquatic microorganisms also influence the amount of oxygen in stream
water. These organisms utilize organic materials in the stream as an
energy source and extract oxygen from the water in the process. Organic
material can be characterized by the amount of oxygen required by micro-
organisms for decomposition. This amount is called biochemical oxygen
demand (BOD).
The dissolved oxygen content and the velocity of flow of the intra-
gravel water influences the well-being of embryos or alevins in spawning
streams. Coble (1961) planted fertilized trout eggs in a stream and
measured permeability, apparent velocity and dissolved oxygen. About
one month after hatching he found a positive correlation between velocity
and survival and between dissolved oxygen and survival. He observed also
that high dissolved levels of oxygen and high stream velocity usually oc-
curred together.
Hermann et_ al (1962) also reported that growth and food conversion
rates of juvenile coho salmon decreased slightly with reduction in
HO
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dissolved oxygen of surface water from 8.3 to 5 mg/1 and decreased abrupt-
ly with further reduction. Many fish died and the survivors lost weight
at dissolved oxygen levels of 2.1-2.3 mg/1.
Leaves from deciduous forests may produce an organic oxygen demand in
otherwise unpolluted streams (Slack and Feltz 1968). Although the rate of
litter production from a deciduous forest is greatest during the autumn leaf
fall period, leaves are part of the continuing load of organic detritus which
streams ultimately deposit in deep pools, reservoirs, or other receiving
bodies. Organic detritus stored in bottom sediments is an almost constant
supply of organic material to a stream.
The uptake of oxygen by tree leaves extends over relatively long per-
iods. In laboratory studies, Chase and Ferullo (1957) showed that after one
year, maple leaves demanded about 750 mg 02/g of their initial dry weight,
but oak leaves and pine needles required about 500 mg 0?/g of their initial
dry weight. The oxygen uptake was rapid; by day 100, maple had achieved
about 70 percent, and oak and pine had achieved about 55 percent of the de-
mand exerted in one year.
Forest practices can influence the amount of oxygen in streams in sev-
eral ways. Clearcutting alongside a stream may increase stream temperature,
thus lowering the saturation concentration. In one extreme case, maximum
temperatures increased from about 57°F to about 85°F and the saturation
concentration dropped from 10.26 ppm to 7.44 ppm (Brown 1972).
Logging debris often accumulates in one channels of clearcut water-
sheds, particularly if logs are yarded across the stream channel. Once
in the stream, debris can influence oxygen levels in two ways: (l) Finely
divided debris, such as needles, leaves, small branches or bark
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contains large amounts of simple sugars which are leached rapidly and con-
sumed by the microorganisms. These materials exert a high BOD. (2) The
restriction of water by debris dams reduces reaeration. Ponding also
increases stream surface area and accentuates temperature increases.
The impact of Douglas-fir needles and twigs, western hemlock needles
and red alder leaves on dissolved oxygen and thus on the quality of moun-
tain stream water was studied by Ponce (1974). The mean COD (the total
quantity of oxygen required for completely oxidizing the material), 90-
day BOD, and BOD rate coefficients were, respectively, 454 mg 02/g,
110 mg 02/g, and 0.125 for Douglas-fir needles, 947 mg 02/g, 110 mg 02/g,
and 0.056 for Douglas-fir twigs, 570 mg 02/g, 200 mg 02/g, and 0.049 for
western hemlock needles, and 888 mg 02/g, 286 mg 02/g and 0.047 for red
alder leaves. Toxicity of a leachate extracted for each species was de-
termined on guppies and steelhead trout fry. The concentration of material
needed to produce toxic effects was so high that oxygen depletion prob-
ably would be responsible for death long before the leachates.
Hall and Lantz (1969) studied the effects of logging on the habitat
of coho salmon and cutthroat trout in coastal streams of Oregon. They
reported a substantial reduction in the DO concentration of the surface
and intragravel water of the clearcut watersheds. DO concentrations from
late spring through most of the summer were too low to support salmon and
trout in one third of the stream available to the salmonids. Juvenile coho
salmon placed in live-boxes survived less than 40 minutes. The lowest
oxygen concentration reported, 0.6 mg/1, was observed in a pool dammed by
debris. During this period, oxygen concentration of the control stream
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and the stream draining the patch cut watershed remained at levels near
saturation. Upon the removal of large debris from the channel and es-
tablishment of a free-flowing condition, the DO concentration rapidly
returned to near prelogging conditions in the surface water. Intra-
gravel oxygen concentrations, however, remained about 3.0 mg/1 lower
than the prelogging concentrations for the next two years and continued
to decline over the next four years to levels less than 2.0 mg/1 at
several locations. Part of the decline of intragravel oxygen concentra-
tions can be attributed to long-term BOD of organic material included
in the gravel. It was concluded that the major problem, however, was
associated with reduced circulation because of sedimentation of the
gravel bed.
The storage of logs in water produces leachates with a significant
quantity of high BOD substances. Atkinson (1971) found that the highest
BOD, 2.36 g/ft^ of log submerged surface area, was exerted by leachates
from a ponderosa pine log stored with the bark removed. The study also
included Douglas-fir and western hemlock.
In summary, logging debris and increased water temperature can lead
to serious decreases in the oxygen concentration of stream water. How-
ever, dissolved oxygen levels can be improved during logging if shade
is maintained and debris is kept out of the stream channel. Buffer strips
can aid in controlling debris accumulation, and where these strips con-
tain large trees they may serve as interceptors for debris sliding down-
hill. One benefit of a buffer zone along the stream is that it dis-
courages logging across or through the stream channel. Improved logging
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techniques such as skylines, balloons and helicopters have been used to
log near streams and at the same time minimize debris accumulation in the
channel (Brown 1972).
Thermal Pollution
Stream temperature, as a water quality parameter subject to modifica-
tion by silvicultural practices, is of prime importance to aquatic eco-
systems. Thermal pollution, especially in coastal Oregon, has gained much
attention. The streams and rivers of this area provide a habitat to
valuable anadromous and resident fish species. Temperature increases can
have a profound influence on dissolved oxygen, disease, increased comp-
etition from undesirable species and vitality. Direct mortality and an
increase in stream eutrophication potential can also result from increased
stream temperature.
Daily temperature variation in undisturbed streams is approximately
2.2° C (4° F) or more. This value has been observed to increase to about
5.6° C (10° F) or higher when all shade along the stream has been removed.
In instances where the natural stream temperatures are already in the
upper range of fish requirements, the removal of streamside vegetation and
exposure of the stream to direct solar radiation can raise temperatures
above the tolerance limits of most salmonids.
Silvicultural practices can change or influence the non-climatic fac-
tors which affect the amount of heat received at the stream surface. These
factors include:
1) Vegetation
-------
2 ) Physiography and Hydrology
a. topography
b. stream channel characteristics
c. inflow of surface and groundwater
d. area, depth and velocity of the stream
VEGETATION
Increases in stream water temperature are caused primarily by in-
creased exposure of the stream to direct solar radiation as a result of
removing streamside vegetation (Brown 1966, 1967, 1970). Shade removal
may increase radiation loads by six to seven times (Brown 1970). Air
temperature and the cooling effects of evaporation are much less import-
ant than solar radiation in controlling temperature on small, unshaded
streams. Brown (1970) found that solar radiation accounted for over 95
percent of the heat input during the midday period in midsummer.
Shading is highly dependent on the type of vegetation along stream
banks. A mature stand of conifers, with much of the lower bole free of
limbs, may offer only partial shade, whereas a younger stand of trees with
well-developed crowns may provide much more shade. Understory species,
such as hardwoods or brush, generally provide very adequate shade for
small streams.
Spacing of vegetation also affects light intensity, If vegetation
is not spaced closely enough, the stream may not be effectively shaded
even though the vegetation is of sufficient height. Tables 6 and 7
show how tree density or stocking affect the light intensity (Resler n.d. ).
-------
Table 6. Stand density effects on light intensity.
(After Resler n.d. )
Stem density
Canopy closure
Basal area
Percentage of Fully
Stocked Stand Removed
0
25
50
75
0
25
50
75
0
25
50
75
Light Intensity
(% of open)
8
14
26
55
4
6
16
43
10
15
27
52
Table 7. Spacing effect on light intensity.
(After Resler n.d.)
Spacing (ft)
4x4
6x6
7x7
9x9
PHYSIOGRAPHY AND HYDROLOGY
Tree
(number/acre)
2721
1210
889
538
Light Intensity
15
16
36
60
Since the angle of the sun varies with latitude, vegetation that shades
the stream effectively at the higher latitude is less effective at lower
latitudes. Consequently, at lower latitudes, vegetative cover should gen-
erally be taller to provide adequate shade.
At certain times of the day, the topography on the south side of an
146
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east-west oriented stream is effective in shading the stream without
any vegetative cover. But on north-south oriented streams, vegetative
cover is needed on both sides of the stream. At midday, the vegetation
which overhangs or is immediately adjacent to the stream is the most
effective. Later in the day when the declination of the sun has changed,
vegetation further from the stream can also provide shade.
Temperature change is directly proportional to the area of stream
exposed and the duration of exposure, and indirectly to the volume of
water. The temperature change will be higher for wider streams with
shallow water than narrow streams with deep water. Brush or hardwoods
can effectively shade small narrow streams, whereas conifers or taller
vegetation are needed to fully shade wide streams.
The stream gradient has a direct influence on the flow speed, The
higher the flow rate, the shorter the exposure time. Therefore, fast-
flowing streams heat up less rapidly than slow-flowing, low gradient
streams.
The type of stream bottom or channel can strongly influence stream
temperature. Rocky bottoms act as a heat sink storing the sun's energy.
As a consequence, stream temperature does not rise nor cool as rapidly.
In contrast, gravel, sand or coarse fragments will both heat and cool
more rapidly,
FOREST PRACTICES
The temperature change brought about by logging is directly pro-
portional to the amount of exposure to solar radiation the stream
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surface experiences, and the heat load applied to the surface area.
Recent studies suggest that stream temperatures are most subject to
change during periods of low flow after removal of a high percentage
of streamside vegetation. Therefore, any silvicultural activity that
exposes a large area of the stream surface to sunlight can cause sub-
stantial changes in water temperatures, especially during low flow
periods.
Studies on stream temperature changes following logging have been
conducted on the H.J. Andrews Experimental Forest in the Oregon Cascades
for more than a decade (Anderson 1973). Levno and Rothacher (1967)
reported large temperature increases in two experimental watersheds after
logging. The shade provided by riparian vegetation in a patch cut water-
shed was eliminated by scouring after large floods in 1964. Subsequently,
mean monthly temperatures increased 7-12°F from April through August.
Average monthly maximums increased by 4°F after complete clearcutting on
a second watershed. The smaller increase in the completely clearcut
watershed was the result of shade from the logging debris that accumulated
in the channel.
Brown and Krygier (1970) have recorded one of the largest changes
in stream temperature after clearcutting in Oregon's Coast Range. Two
patterns of clearcutting were used. A 750-acre watershed was patch cut
with three small clearcuts covering about 25 percent of the watershed,
Clearcut boundaries were separated from perennial streams by buffer strips
50 feet to 100 feet wide. A second watershed of 175 acres was completely
clearcut. They found no increase in temperature attributable to logging in
1-48
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the patch cut watershed, where buffer strips continued to provide shade
for the stream. In contrast, an increase of 1-4°F in monthly mean maximum
temperature was observed after complete exposure of the clearcut water-
shed. There was an annual maximum rise of 28°F on this small stream when
discharge dropped to .001 cubic feet per second in late summer.
Studies were conducted by Brown et_ al_ (1971) on Steamboat Creek of
the Oregon Cascades to determine the effects of logging on stream temper-
atures and to determine the effectiveness of varying densities and types
of streamside vegetation for temperature control. They found that remov-
ing all shade from a stream course could increase water temperature 10°F
and more, whereas the differences in stream termperature due to natural
causes varied by approximately 4°F. Exposing 150 feet of one small stream
increased the water temperature 13°F. They also recorded the impact of
various degrees of shade reduction on stream temperature, including clear-
cutting with buffer strips.
Hall and Lantz (1969) noted that temperature increased progressively
as the stream progressed through a clearcut. Temperature decreased about
6°F as the water passed through a somewhat shaded area of the stream
channel, where streamside vegetation had been less severely affected by
logging. They also found that slash burning increased the stream temper-
ature from 55°F to at least 82°F. On a watershed where the fire was sep-
arated from the stream by a buffer strip, no significant increase in
temperature associated with slash burning was observed.
Patric (1969) compared the effect of two clearcutting patterns on
water quality. Temperatures were unaffected by clearcutting the upper half
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of one watershed. Clearcutting the lower half of the second watershed
increased stream temperatures by up to 7°F.
Greene (1950) studied the effect of clearcutting on trout streams.
He reported that maximum weekly temperatures recorded during May on a
non-forested stream were 13°F higher than those recorded on a nearby
forested stream. He noticed also that the maximum temperature dropped
from 80° to 68°F after the non-forested stream meandered through 400 feet
of forest and brush cover.
Helvey (1972) studied the first year effects of wildlife on water
yield and stream temperature in north central Washington. He reported
that maximum daily stream temperature was increased by as much as 10°F
during late summer when streams were exposed to direct insolation. Levno
and Rothacher (1961) report that the first year after slash was burned on
a 237-acre clearcut watershed in the Cascade Range of Oregon, average
maximum temperature increased 13°, 14° and 12°F during June, July and
August, respectively.
Chapman (1962) checked comparable logged and unlogged drainages in
Oregon's Alsea River Basin and found temperatures to be as much as 10°F
greater in logged areas where riparian vegetation was completely removed.
Meehan et al (1969) reported a maximum increase in summer stream
temperature of only 9°F after clearcutting on two watersheds near Hollis
on Prince Wales Island, Alaska. The cool, generally overcast climate
of southeast Alaska is probably the main reason for this relatively small
change in stream temperature after logging. Meehan (1970) also noted
that temperature increases after clearcutting in this region do not
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normally approach lethal limits for fish populations. However, the in-
direct effects of temperature increase, particularly in the case of
resident fish populations, are not known. Salo et al (1973) examined
the effects of logging on small streams in the Thorn Bay area of south-
east Alaska. They found that stream temperatures increase much more
rapidly in clearcut-logged than in unlogged study areas, and maximum
stream temperature was reached 2.5 hours after peak solar radiation.
Swift and Messer (1971) measured the influence of six forest-
cutting treatments on stream temperatures of small watersheds in the
southern Appalachian Mountains. Where forest trees and all understory
vegetation were completely cut, maximum stream temperatures in summer
increased from the normal 66° to 73°F or more. Some extreme treatments
raised temperatures more than 12°F above normal. Where stream bank
vegetation was uncut or had regrown, summer maximums remained unchanged
or declined from temperatures measured under uncut mature hardwood
forest.
Water-temperature records through September 1968 were summarized
by Blodget (1970) for 120 streams in the north coastal subregion of Cal-
ifornia. He presented current and historic stream temperatures for
correlating periodic and thermograph records and for analysis of the
factors affecting these temperatures. The summary data for each site
is useful in providing guidelines for the establishment of thermal water-
quality guidelines.
Brazier and Brown (1973) defined the characteristics of buffer
strips that are important in regulating the temperature of small streams
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and described a method of designing buffer strips that are intended to
minimize changes in temperature and at the same time minimize the amount
of commercial timber left in the strip to provide the necessary shade.
The results led to several interesting conclusions about designing buffer
strips for temperature control purposes.
l) Commercial timber volume alone is not an important criterion
for water temperature control. The effectiveness of buffer
strips in controlling temperature changes is independent of
timber volume.
2) Width of the buffer strip, alone, is not an important cri-
terion for control of stream temperature. For the streams
in this study, the maximum shading capability of the average
strip was reached within a width of 80 feet; 90 percent of
that maximum was reached within 55 feet. Specifying standard
100 to 200 foot buffer strips for all streams, which usually
assures protection, generally will include more timber in the
strip than is necessary.
3) Angular canopy density is correlated well with stream-
temperature control. It is the only single criterion the
forester can use that will assure him adequate temperature
control for the stream without overdesigning the buffer strip.
Increases of suspended sediment can alter aquatic environments by
changing the spectral properties of streams and heat radiation. Suspended
sediment can alter the rate of temperature change in river waters. This
is particularly significant in deep rivers and lakes where thermal strati-
fication of the water produces a stratification of the silt load.
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WATER TEMPERATURE CRITERIA FOR FISH
The most significant implication of the warming of small headwater
streams is the potential degradation of water quality for trout habitat.
Fishery managers generally agree that water temperatures for trout should
remain consistently below 70°F and that optimum trout production occurs
in streams which do not exceed 68°F, even for short periods of time
(Stroud 1967). Trout can exist temporarily in warmer waters, but the
physiological stress may reduce their resistance to predation and disease
or inhibit their feeding and reproduction, any of which could eventually
eliminate the fishery (Brett 1956).
Brett (1956) noted that the upper and lower limits of temperature
which a fish can withstand define the extremes of its tolerable environ-
ment. Lethal temperatures and thermal tolerances vary from species to
species. Salmonids have the lowest thermal tolerance, with the maximum
upper lethal short term exposure temperature barely exceeding 77°F.
The following table summarizes information taken from the 1975
preliminary draft publication entitled Quality Criteria for Water to be
published by U.S. Environmental Protection Agency, Washington, D. C.
TABLE 8. Maximum weekly average temperatures for growth and short-
term maxima for survival for juveniles and adults during
the summer (Centigrade and Fahrenheit).
Fish Species Growth3- Maxima13
Rainbow Trout 19 (66) 24 (75)
Brook Trout 19 (66) 23 (73
Coho Salmon 18 (64) 24 (75)
Sockeye Salmon 18 (64) 22 (72)
Largemouth Bass 32 (90) 34 (93)
Bluegill 32 (90) 34 (93)
a — Calculated according to equation: Maximum weekly ave. temp, for
growth = optimum for growth + 1/3 (ultimate incipient lethal temp.-
optimum for growth).
b — Based on temperature (°C) = 1/b (LCG10 TBffi(Min. )-a)- 2°C,
acclimation at the maximum weekly ave. temp, for summer growth, and
data in Appendix II-c of Water Quality Criteria, 1972 (NAS, 1974)
153
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SUMMARY
Silvicultural practices and logging can significantly increase the
temperature of small streams. Shade removal affects solar radiation and
may increase radiation loads by six to seven times (Brown 1970). Tem-
perature increases from 6 to as much as 28 F have been reported. The mag-
nitude of the increase is dependent upon stream characteristics such as
flow, surface area exposed to sunlight, and the amount of radiation received
from the sun.
Increases in the temperature of small streams can be prevented during
and after logging by leaving a protective strip of vegetation alongside the
stream to provide shade. The efficiency of this strip in controlling water
temperature has been demonstrated in several studies (Brown and Krygier
1970, Brown et_ al 1971, Swift and Messer 1971). Various guidelines for the
protection of streams in logged watersheds have recommended buffer strips
for temperature control (Federal Water Pollution Control Administration
1970, Lantz 1971, Society of American Foresters, Columbia River Section,
Water Management Committee 1959, and USDA n,d. ). These are discussed in
Chapter 5.
One approach to managing water temperature is to predict the temper-
ature changes that might result from various Silvicultural systems and size
of cutting units. Brown (1966, 1969) has developed a technique by using
an energy budget for predicting temperature changes of small streams once
the streamside vegetation has been removed.
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CHAPTERS
PLANNING AND MANAGEMENT
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PLANNING AND MANAGEMENT
Previous sections of this report have outlined background information
for the region, described the forest practices utilized in the Pacific
Northwest, and presented research summaries concerning the impacts of
such forest practices on water quality. This section presents a summary
of planning and management methods which represent the state-of-the-art
for preventing water pollution from logging, residue management and
reforestation. The purpose of this report is to summarize existing
knowledge and technology, not to develop new methods.
Most of this section is based on, or has been excerpted from, the
literature concerning water quality and forest management. However, a
small percentage of the information presented, by necessity, results
from the objective synthesization of available knowledge for the specific
purposes of this report. In general, only the information directly re-
lating logging, residue management and reforestation to water quality
protection, and, in some cases, to fisheries, is presented.
Timber harvest has certain features that relate to water quality
protection, as follows:
o the activity is dispersed and distributed over
time
o physical, biological and chemical factors vary considerably
from site to site and from subregion to subregion, resulting
in widely varying water pollution potentials
o levels and types of quality control relative to timber
management cover a wide range within the region
155
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o the knowledge and field testing of methods for reducing
water quality impacts vary significantly within the four-
state study area
o the values and uses of similar water bodies differ from one
subregion to another
These basic characteristics result in a greater potential for im-
proving the quality of runoff from timber harvest areas through inter-
disciplinary planning than through remedial measures (e.g., catch basins).
Certain standard requirements for timber harvesting can also be beneficial
for water quality purposes, if the intrinsic qualities of the subregions
are considered and the standards set accordingly. This section of the
report includes subsections on information requirements, predicting
effects, planning, sensitive areas and facilities location and silvi-
cultural logging systems.
Information Requirements
Regardless of the planning/management approach to be utilized, an
early investment in information gathering is required, Unless the informa-
tion is already available, this represents a significant expenditure of
time and money. For maximum usefulness, the information collection should
begin a few years prior to the timber harvesting or road building. Such
information might include basic data (e.g., stream flow and water quality),
and/or existing reports for review purposes. It should be limited to that
required by the planning methodology or management techniques envisioned.
156
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Information requirements vary according to the specific use antici-
pated, and can be categorized as follows:
1) planning
2) prediction
3) impact monitoring
PLANNING
The following basic types of information (re: water quality) are
generally required:
o topography
o soils and erosion hazards
o geology
o aquatic and/or marine biology
o water quality
o silviculture
o hydrology and geohydrology
o meteorologic
o engineering constraints
o logging system alternatives
o residue management alternatives
o institutional constraints (applicable laws)
In some instances, particularly involving small landowners, it may
be prohibitive to adequately consider all the information types mentioned.
Under such circumstances, the following six categories may suffice for
site-specific planning:
157
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o soil types, slopes and erosion hazards
o applicable state and federal water quality standards
o existing water quality and the fisheries to be affected
o silvicultural alternatives (clearcutting, selection cutting,
etc. )
o logging system alternatives
o residue management and reforestation options
Federal land management agencies, such as the U. S, Forest Service,
most state land agencies and some private forest management organizations,
have compiled a considerable amount of information relating to forest
lands within their jurisdictions. Such agencies also have expertise
available to generate additional information for planning purposes, if
necessary. However, not all agencies or landowners have this capability
and may have to depend on outside sources or special studies. Table 9
presents a general list of potential information sources by category.
This does not include private organizations that .may be available, if new
studies are required.
One important requirement for forest land planning is an inventory
of the land systems involved. Wertz and Arnold (1972) have outlined the
requirements for such an inventory, which is presented as Table 10.
In addition, the "System Outline" for the land base portion of an
integrated environmental inventory as proposed by Wertz and Arnold (1972)
is presented as Table 11.
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Table 9: Categories and Potential Sources of Information
Concerning Forest Management and Water Quality
Potential Sources
Soils
Geologic
Information Categories
Topographic U. S. Geological Survey
Adjoining landowners (i.e., private, USFS,
BLM)
Local planning and zoning agencies
Private mapping and aerial photography
organizations
Agricultural Stabilization and Conservation
Offices (USDA)
U. S. Soil Conservation Service
U. S. Forest Service (PNW & Intermountain
Experiment Stations)
County agricultural extension agents
U. S. Geological Survey
Adjoining landowners (i.e., private, USFS,
BLM)
Local planning and zoning agencies
Universities
U. S. Geological Survey
State mining or geologic agencies
Universities
Adjoining landowners (i.e., private, USFS,
BLM)
State fish and game agencies
National Marine Fisheries Service
U. S. Fish and Wildlife Service
U. S. Geological Survey
U. S. Environmental Protection Agency
State environmental agencies
State water administration agencies
Universities
State forest resource agencies
Universities
U. S. Forest Service
County extension agents
Local forest management associations
Adjoining landowners (i.e., private, BLM)
Hydrologic and Geohydrologic U. S, Geological Survey
State water administration agencies
Universities
Water user organizations
Aquatic and/or Marine
Biology
Water Quality
Tree Species, Forest Types
and Stand Densities
Meteorologic
National Weather Service (U. S. Department
of Commerce)
Universities
County agricultural extension agents
159
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Table 10
(Adapted from: R. J. Alvis 1971)
Taken from: Wertz and Arnold 1972
THE LAND SYSTEM
I. Land components
A. Lithology
Kind and character of the bedrock.
B. Climate
Kinds, magnitudes, and frequencies of climatic occurrences.
C. Age
The time required to reach the present stage of development
of lands.
D. Soils
The unconsolidated portion of the earth's land surface which can
support plant growth.
E. Geologic structure
The arrangement, internal features, and shape of rock forma-
tions.
F. Landform
The shape and configuration of units of the earth's surface.
G. Plant ecology
Plant community identification and relationships with other
elements of the environment.
II. Land system
A conceptual device which achieves an integrated overview of
the relationships between geologic and climatic history, soils
and plant ecology, as an aid in understanding land resources.
A. Relations of components to land system
Basic Components Lithology Geologic Structure Climate
(Independent)
TIME
Manifest Components Soils Landforms Plant Ecology
(Dependent, related)
160
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Table 11
Taken from: Wertz and Arnold 1972
SYSTEM OUTLINE
LAND BASE PORTION Of INTEGRATED
ENVIRONMENTAL INVENTORY
Category
VII
Nam*
Eatis for Delineation
Sii* Rang*
Principal Application
Physiographic Basic Elements 1000s of sq. Nationwide or broad
Province Structure, lithology, climate. miles regional data summary.
First order stratification.
VI Section Basic Elements 100s to 1000s
Structure, lithology, climate. of sq. miles
Second order stratification.
Subsection Basic Elements 10s to 100s of
Structure, lithology, climate. sq. miles
Third order stratification.
Landtype Manifest Elements 1 to 10s of
Association Soils, landform, biosphere, sq. miles
First order stratification.
IV
III Landtype Manifest Elements 1/10 to 1 sq.
Soils, landform, biosphere. mile
Second order stratification.
II Landtype Manifest Elements 1/100 to 1/10
Phase Soils, landform, biosphere. sq. mile
Third order stratification.
I Site Represents integration of all Acres or less
environmental elements. Units
are generally not delineated
on map.
Broad regional sum-
mary. Basic geologic,
climatic, vegetative da-
ta for design of indi-
vidual resource inven-
tories.
Strategic management
direction, broad area
planning
Summary of resource
information and re-
source allocation.
Comprehensive plan-
ning, resource plans,
development standards,
local zoning.
Project
plans.
development
Provides precise under-
standing of ecosystems.
Sampling will be for
defining broader units,
for research, and for
detailed on-site project
action programs.
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Certain basic hydrological and meteorological information is useful
for water quality planning on forest lands as follows:
1) Annual (year-round) hydrographs for key locations for at least
two years
2) Peak flow records for major flood flows for at least five
consecutive years
3) Stream order definitions
4) Precipitation, including snow, preferably as isohyetal maps
(annual average yield and maximum precipitation)
5) Critical event precipitation patterns (e.g., high intensity or
long duration storms)
6) Erosion rates and sediment yields
In areas where streams or lakes present important forest values or
may be affected by forest activities, limnological and stream habitat
information is required. Base line aquatic life information involves a
minimum of one-year data collection prior to the planned watershed dis-
turbance. The frequency and seasonal variation of the sampling will
depend on the life cycle of the species being monitored.
The U. S. Forest Service Northern Region has prepared a publication
entitled "Lake Habitat Survey" (1974). This publication outlines guide-
lines for such surveys and is recommended as a basic reference for lake
habitat information collection.
Platts (1974) presents an inventory method for aquatic systems in a
publication entitled "Geomorphic and Aquatic Conditions Influencing
Salmonids and Stream Classification," which should be generally applicable
in the Northwest. Platts collected the following information:
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1) Stream, pool and riffle widths to the nearest foot
2) Four stream depths at equal intervals across the stream
to the nearest inch
3) Ratings, locations and features of pools
4) Stream channel surface material classifications
5) Cover, conditions and types of streambanks
6) Channel elevations and gradients
7) Geologic process groups and geomorphic types
8) Stream order
9) Whether the watershed was disturbed or undisturbed
10) Fish species, their numbers, and the length of fish
occurring in selected streams between transects
The data requirements for planning are considerably different than
for impact monitoring, particularly when the impact data is to be used
in court as part of a legal proceeding. The most important character-
istic of planning information is its comprehensiveness, which is required
to establish the basic character of the area in question. Trends and
unique or special intrinsic qualities require emphasis as opposed to the
specificity required in impact monitoring. Planning involves general
constraints and the avoidance of problem areas, so specific data are not
as important as comprehensive data. Trend projections and broad scope
statistical analyses are particularly useful in planning.
The reader is referred to "Three Approaches to Environmental
Resource Analysis," a report prepared by the Landscape Architecture
Research Office of the Graduate School of Design, Harvard University (1967).
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The three planning approaches presented have general applicability to
land use planning, and include planning method articles by G. Angus Hills,
Phillip H. Lewis and Ian L. McHarg.
PREDICTION
The use of prediction techniques including computerized mathematical
models, is discussed later in this section. Such analysis tools can be
very useful if adequate data is available as input to models or methods,
which have been developed for, or adapted to, the specific problem and
project area under study. However, computerized models (not all models
are computerized) have limitations including:
1) high initial cost for developing a new model, which may
be prohibitive for a once-only use
2) the need for specialized personnel to develop, adapt and
operate the model
3) the need for specific data inputs
However, when such models can be effectively utilized the accuracy and
consistency of predicting water quality related impacts can be maximized.
One of the most important considerations is the prior assembly of adequate
input data.
The type of data required for prediction models generally varies
somewhat from that required for planning and impact monitoring. The
consistency of the data collection and analysis procedures is of secondary
importance for planning information, provided the trends are reflected.
Prediction methods, however, usually require very specific types of data
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and analysis, since computer programs or analytical procedures are
developed assuming a specific type of data input. Occasionally, a
nonspecified but similar type of available data can be utilized through
program revision, provided the necessary data relationships can be
defined, but this is the exception and not the general rule. Consequently,
if such models are to be used, their data requirements must be determined
well in advance.
The data most often required for models related to water quality and
silviculture generally fall into one of the following categories:
1) hydrology
2) water quality
3) erosion rates and sediment yields
4) precipitation
5) aquatic or marine biology
6) cover type and density
Certain considerations are important for each of the above types
of data, including:
a. length of data collection period required for
adequate significance
b. collection pattern or sampling network
c. critical periods requiring sampling (e.g., spawning)
Hydrologic
Hydrologic models involving frequency of occurrence, e.g., peak
flood flows, require a minimum of three to five years of data, preferably
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ten to fifty years. For this reason, it is advisable to use existing
streamflow gaging stations with long-term records, if such are available.
The location of data collection stations should reflect the normal and
altered situations.
Simulation models generally require more types of data but can in-
volve shorter time periods. Most hydrologic data is collected continuously.
Water Quality
Water quality data collection is often coordinated with hydrologic
data collection networks, but continuous data is not usually taken for
water quality prediction modeling purposes. "Grab" sampling for select
parameters at critical periods is the most common, although not always
adequate, approach.
The water quality parameters generally significant to silvicultural
activities include:
1) dissolved oxygen and biological oxygen demand
2) nutrients
3) temperature
4) turbidity and/or suspended solids
Erosion Rates and Sediment Yields
Models to describe erosion processes are based either on empirical
equations or are constructed from first principles using Newton's laws
of motion, the laws of viscous forces, and some of the basic concepts of
fluid mechanics. Because of the complexity of developing models from
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first principles, most of those that have been developed, including the
equation developed "by Megahan (1974), are of an empirical basis.
Typically, one or two constants appear in such equations, or models,
that are characteristic of a particular soil type. Before the models
can be applied, it is necessary to conduct simple erosion experiments
and evaluate the constants for each soil type under consideration. Once
experimental data are available from a range of soil types, the constants
for untested, but similar, soils (or an area under study) can be
approximated.
Meteorology
As with erosion processes, models designed to predict meteorological
conditions can be founded on first principles or can be simply descriptive
of the processes observed. Most of the emphasis in micrometeorology in
ecology has been directed toward energy balance models which can be used
only to predict or to describe the energy budget of relatively simple
ecosystems. Information on surface absorptivities and emissivities of
the many surfaces present is required. However, these models are limited
in scope and at present hold little promise of application to water
pollution problems.
Aquatic or Marine Ecosystems
The most commonly used models of aquatic ecosystems are based on mass
and energy flow from the lower to higher trophic levels of the system. A
typical aquatic model might require data concerning aquatic plants (as
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the first trophic level invplved in fixing radiant energy), benthic
organisms, herbivores, and at least one level of carnivores.
Typically, these models require information on the rate of transfer
of energy from one level to the next. Rates may depend on several factors,
including the biomass available at other trophic levels and constants
characteristic of feeding rates, reproduction, mortality, etc. Of the
models discussed in this report, this type requires the largest investment
of time and effort, and the widest range of specialists, to obtain the
data necessary to characterize a particular aquatic or marine ecosystem.
Collection of the data must be by specialists and relate to the specific
requirements of the model.
Plant Competition
Models that could be used to predict the rate of revegetation of
forested areas subjected to logging would be of enormous value for pre-
dicting erosion rates, stream sedimentation and the concentration of
organic pollutants in surface waters. Unfortunately, a limited amount of
research has been conducted in this area. They are mentioned here only
as a type of model that may be available in the future.
IMPACT MONITORING
Since this report concerns the prevention of water pollution, the
after-the-fact monitoring considerations are of secondary importance and
will not be dealt with in detail. A brief discussion is presented, however,
because of the significant value for future planning of field data
168
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concerning the cause-effect relationships between actual logging opera-
tions and water quality in a given subregion. Such information is in-
valuable, particularly if the individuals responsible for data collection
and analysis coordinate closely with the foresters and engineers in the
field and the planners responsible for future prescriptions.
Monitoring the water quality or aquatic life impact of silvicultural
practices presents a complex array of problems which are usually best
assigned to specialists. This would include biologists of various types,
hydrologists and water quality specialists. The parameters that lend
themselves most to routine monitoring include temperature, turbidity
and suspended solids, dissolved oxygen and specific conductance. Analy-
sis of biological properties such as coliform or dissolved organic and
inorganic chemicals usually requires sophisticated instrumentation and
specific sample handling methods.
Detection of the impact of silvicultural practices is generally
evaluated by sampling upstream and downstream from the activity to be
monitored. If it is reasonably certain that the parameters measured
should be unaffected through that reach of the stream, except by the
monitored activity, then samples so compared should be useful. Base
level monitoring, before the activity begins, is necessary. Inflow
conditions, travel time, stream-channel characteristics, and biologic
conditions affect the location, frequency and type of sampling.
Water Temperature
Water temperature can be measured to establish the effects of canopy
169
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removal which would reduce shading or increase the solar loading on the
small streams. Sampling location should be shaded so solar radiation does
not affect reading of the sensor. Maximum and minimum temperatures are
important along with the duration of the exposure, particularly for
maximum temperatures.
Suspended Sediment
The measurement of suspended sediment is useful in determining
the impact of silvicultural practices on the physical condition of the
stream. There is a stratification within the stream with larger materials
near the bottom and smaller materials near the surface. Consequently,
depth-integrated samples are usually taken for most accurate results.
Bed load data may also be useful, but involves more complex instrumentation.
Dissolved Oxygen
Organic debris that ends up in the stream channel as a result of
timber-felling or yarding can consume dissolved oxygen in the decomposition
process. Several portable meters are available for field measurement of
dissolved oxygen.
Dissolved oxygen is also a function of water temperature, so both
parameters should be measured. Low temperature water usually maintains
a higher oxygen concentration than warmer water. The most critical period
for dissolved oxygen is during warm summer months when biological activity
is high and water temperatures are also high.
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Specific Conductance
Specific conductance is a measure of the electric current carrying
capacity of water. Increasing values of specific conductance indicate
an increasing load of dissolved ions; low values of specific conductance
generally indicate very clean, pure water.
Specific conductance meters must be -calibrated using standard
solutions for the approximate range of values of the stream water in
question. It is corrected to a standard temperature of 25°C, usually
internally within the meter.
Predicting Effects
BACKGROUND
Predicting the water quality related effects of a timber harvest
activity can take various forms. The simplest approach might involve
comparing research information applicable to the area (as has been
summarized in the previous section "Impact of Forest Practices on Water
Quality") with the various facets of the proposed project. The most
sophisticated method would involve the use of specific "models" or
"equations," which mathematically approximate the processes anticipated
(e.g., erosion/sedimentation). Such models serve at least two purposes:
(1) they facilitate a better understanding of the process involved, and
(2) they are useful in predicting the impacts of a given practice or
operation, provided the development, adaptation and use are reasonably
correct, and the input data is sufficient (data needs have been previously
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discussed). Many such models have been programmed for computer application,
which allows rapid comparison between various management assumptions.
The models available vary in their usefulness as predictive tools,
but many are presently suited for such use. Regardless of their limita-
tions computer models, which incorporate current knowledge of a particular
phenomenon, should give results at least as good as the alternative
analysis methods that depend on the same data and knowledge of relation-
ships. The value of the computer models is in the rapidity with which
results can be obtained. However, in many circumstances, experienced
field personnel, sensitive to water quality, and knowledgeable of the
specific study area, can accurately "project" the impacts of a range of
forest activities. The value of such capability should not be under-
estimated.
Methods for predicting the effect of forest practices on various
environmental factors are applicable to water quality, aquatic ecosystem
analysis, growth rates expected given certain stand and environmental
variables, and the influence of various levels of fire intensity on site
productivity. All prediction methods being used or developed have the
same essential character — given a set of conditions, a prediction may
be made, with some degree of certainty, about the effect of specific
practices.
One of the first prediction methods used was that of statistical
analysis which provided the basis for some of the earliest models used.
Multiple regression has been used extensively to predict the influence of
several independent variables on a single dependent variable; for example,
the effect of soil nutrients, soil moisture and temperature on tree growth.
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Over the years, many deterministic models have also been used in
forestry. Prediction of the board or cubic foot volume of a tree is
based on a geometric model of log size and shape.
These are but a few examples of two broad classes of models which
have been, and will continue to be, used for predictive purposes in
forestry.
The rapid increase in the use of models has led to some confusion
in concepts and terminology. The term "model" is often thought to mean
"computer model." To others, "model" implies a geometric representation
of a particular object or system. Still others speak of "flow models,"
which trace the movement of information through an organization, or
material through a set of processes. It is noted that to many the
term "model" implies a mathematical equation.
"Simulation models," frequently but not necessarily used in con-
junction with a computer, are designed to simulate or mimic a particular
phenomenon. Many phenomena are of such complexity as to defy the
straightforward application of mathematics. In such instances, computer
simulation is adopted.
The most critical step in the application of modeling is comparing
the model prediction with the behavior of the real system, sometimes
called verification. Modeling has been justified on occasion for the
clarity and definitive it can bring to a problem, but the test of any model
is its predictive capability. Model precision is governed by many
aspects of the total process, including available data, the precision
of relationships between variables, and the degree to which the problem
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can be defined. Several models of both a stochastic and deterministic
nature are described in subsequent sections. For the most part, these
models are expressed in deterministic form. It is emphasized that many
of the parameters included in equations are determined by the conditions
of specific forest sites.
SOIL EROSION
The prediction of soil erosion involves a complex interaction of
variables; consequently, the development of models for analysis is diffi-
cult. Wooldridge (1970) has urged caution in the use of such models :
...frequently their greatest value is in the manipulation
of the various factors to see if they give realistic
estimation for soil loss and relationships between factors,
However, in many situations such models, if available and applied correctly,
can be useful for prediction.
Smith and Wischmeier (1962) have developed an equation to predict the
average soil loss in tons per acre. Although this equation is primarily
intended for agricultural land, it provides insight into the soil erosion
process and may, upon modification, be useful for predicting erosion for
bare soils resulting from logging road construction or vegetation removal.
Another expression of soil erosion similar to the Wischmeier equation
was developed earlier by Musgrave (1947). At this time, the Musgrave
equation has not been adapted for use in the west. Dissmeyer (1971)
developed an equation to evaluate the effect of disturbance on suspended
sediments and surface water, and alternative methods for reducing erosion
and sedimentation. This method, the "First Approximation of Suspended
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Sediment" (FASS) has been used primarily in the southeast and considers
gully and channel erosion.
Megahan Erosion Model
A model, or equation, has been developed by Megahan (1974-b) that
may be used to predict surface erosion (not mass erosion) from water-
sheds which have experienced reading and logging, A negative exponential
equation containing three parameters was derived to describe time trends
in surface erosion on severely disturbed soils (primarily the road
system). This "model" is most appropriate on Idaho Batholith soils, and
is presented as equation 1.
Et = V - S0(e-kt-l) 1.
E+ = the total erosion since disturbance
(tons/mi )
E = the erosion rate to be expected after a
long period, assuming no major disturbance;
this value is an estimate of the long-term
norm for the site (tons/mi day )
S~ = the amount of material available to be
eroded at time zero after disturbance
(tons/mi^)
k = an index of the rate of decline of erosion
following disturbance; this can be thought
of as an index of the recovery potential
for the site in question (day )
t = days of elapsed time since disturbance
Data from four different studies of surface erosion on roads con-
structed from the granitic materials found in the Idaho Batholith were
used by Megahan to develop the equation parameters. Two of these
studies, Deep Creek and Silver Creek, involve erosion from the entire
road prism (cut slopes + roadbed + fill slopes). The other two studies,
in the Bogus Basin and Deadwood River areas, were located on double-
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lane forest roads and designed to measure erosion on road fill slopes only.
Plotted data from these studies were used to determine En, SQ, and k. The
long-term erosion rate (En) determined in the Deep Creek data was validated
by comparison with average sediment yields for Ditch Creek in the Silver
Creek study area.
It was found that the erosion rate for undisturbed lands on the Idaho
^
Batholith averages about 0.07 ton/mile/day. For the first year after
disturbance, erosion rates per unit of area involved in road construction
were three orders of magnitude greater than those on similar undisturbed
land, and after almost forty years they are still one order of magnitude
greater. According to Megahan, "The potential for damage by such accele-
rated erosion should be apparent." The study found that, "By far the
largest percentage of soil loss occurs within one to two years after
disturbance." And that, "Erosion control measures must be applied im-
mediately after disturbance to be effective."
Rainfall intensity data were used to illustrate that variations in
erosion forces, as indexed by a rainfall kinetic energy times the maximum
30-minute rainfall intensity, "the erodibility index," were not the cause
of the time trends in surface erosion. Although vegetation growth can be
an important factor in reducing accelerated erosion, it did not cause the
rapid erosion decreases found in the cases studied. The evidence suggests
that surface armoring was a dominant factor causing the time trends in
surface erosion. The significance of time trends in surface erosion is
discussed in the paper.
Other studies, including those by Anderson (1972) and Frederickson
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(I970b), have found decreasing time trends in sediment from poorly
logged areas in California and in Oregon, respectively.
The Megahan equation is a tool that, with refinement and adaptation
to specific sites, has significant potential for estimating soil losses
from reading and logging systems proposed on the Idaho Batholith, or other
similar credible soils, primarily in subregions 8, 9, 10, 11, 12 and 13.
The principles and methods used in developing the equation have applic-
ability to varying degrees on erodible soils throughout the northwest.
It does require field data from logged areas of a similar character
in order to determine the basic parameters of the soil/hydrologic zone
in question.
WATER TEMPERATURE
Increases in stream water temperature are caused primarily by
increased exposure of the stream to direct solar radiation as a result
of removing stream side vegetation (Brown 1966, Brown and Krygier 1967,
and Brown 1970a). Shade removal may increase radiation loads by six to
seven times (Brown 1970). Air temperature and the cooling effects of
evaporation are much less important than solar radiation in controlling
temperature on small, unshaded streams. Brown (1970) found in western
Oregon that solar radiation accounted for over 95 percent of the heat
input during the midday period in midsummer.
Several silvicultural practices can change or influence the non-
climatic factors which affect the amount of heat received at the stream
surface. These factors include:
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1) vegetation
2) topography
3 ) stream channel characteristics
4) inflow of surface and groundwater
5) area, depth and velocity of the stream
Stream side shade is the most important factor influencing changes in
water temperature over which the land manager has some control. By main-
taining vegetative cover of such height and density as to adequately shade
the stream during periods of maximum solar radiation, water temperature
increases can be prevented and/or minimized as necessary to meet manage-
ment goals. The replacement of vegetation after clearcutting along streams
may be an acceptable means of rapidly reestablishing vegetation that could
adequately provide shade protection and thereby reduce increased stream
temperatures. Another approach to reducing the impact of clearcutting
along stream sides and the resultant changes in temperature could be
accomplished through predicting what temperature changes might occur by
regulating the silvicultural system and the size of cutting units.
Brown (1966, 1969) has developed a technique (using an energy budget)
for predicting temperature changes of small streams once the stream side
vegetation has been removed. This technique is only briefly described in
this report. The general equation for the energy budget takes the form,
Brown (1969):
AS = QNR± QE ± Qc ± QR ± QA
where AS = net change in energy stored
QNR = net thermal radiation flux
QE = evaporative flux
Qc = conductive flux
QH = convective flux
QA = advective flux
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The sign is positive for energy added to the stream and negative
for energy losses. The budget techniques used for temperature prediction
evaluate the net change in the energy level of the stream (AS). Net
thermal radiation is the difference between total incoming and total
outgoing all-wave thermal radiation. This flux can be measured directly
with a net radiometer.
The predicted water temperature change is then a function of the
heat applied and the volume of water heated.
Tw = A xAS x 0.000267
F
where T = predicted temperature change (°F)
AS = change in energy storage
(Btu/ft2 min-1)
A = surface area of study section (ft^)
F = discharge ( cfs)
0.000267 = constant converting discharge from
cfs to pounds of water per minute
On unshaded stretches, net all-wave radiation is the predominant
energy source during the day; evaporation and convection account for
less than 10 percent of the total energy change. Conduction of heat
into the stream bottom is an important energy balance component only on
shallow streams having a bedrock bottom. Up to 25 percent of the energy
absorbed by such a stream is transferred into the bed. Therefore, the
maximum daily stream water increase is estimated by:
AS = QNR
A xAS
AT =—F x 0.000267
The above equation can be used to predict what temperature increase
might occur on the site. The impact that such increases can have down-
stream is predicted by the following mixing ratio formula (Brown 1970a):
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T = Dm Tm + Dt Tt
Dm +Dt
where T = temperature of the main stem after the
tributary enters
^m = discharge of main stem before tributary
enters
t = discharge of tributary
™m = temperature of main stem before
tributary enters
t = temperature of tributary
Brown's technique would have general applicability wherever temper-
ature increases due to vegetation removal along streams are a potential
problem. It was developed in western Oregon and has its greatest potential
applicability in subregions 3, <4, 5, 6 and 7,
PEAK FLOW ACCENTUATION AND CHANNEL EROSION
The U. S, Forest Service, Region 1, has developed a procedure (water
yield increase analysis procedure) for predicting increases in water yield
and peak flows due to timber management (or vegetation manipulation). The
procedure includes methods for locating, sizing and phasing timber manage-
ment activities to assure that the percentage of flow increase remains
within acceptable limits as determined by channel stability and soil
erosion hazards.
This procedure is explained in "Forest Hydrology: Part II, Hydrologic
Effects of Vegetation Manipulation," U.S.D.A. Forest Service, and is
summarized as follows:
l) Determination of the normal annual runoff for the subject
watershed from SCS and USGS information.
2) Determination of the allowable increase limits for annual
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yield and periods of maximum channel impact peak flows as
affected by (a) soil erosion hazard ratings, (b) stream
channel stability, (c) on-site analyses (stream bed inspection),
and (d) average annual peak flow patterns and departures.
3) Synthesization of the water yield, peak flows and channel
impact periods due to actual or potential vegetation mani-
pulation operations. Such water yield and hydrograph changes
are affected by: (a) equivalent clearcut areas and locations,
(b) evapotranspiration changes, (c) redistribution of snow
accumulation patterns due to timber management activities,
and (d) changes in interception patterns.
4) Synchronization of proposed harvest patterns, locations
and phasing in order to stay within the accepted yield and
peak flow limitations.
The guidelines, curves and functions (which must be developed
for each individual watershed) are based on the following:
1) geology
2) soil erosion hazards
3 ) mean annual runoff
4) stream order
5) hydrologic recovery rate
6 ) stream channel stability
7) hydrologic response
8) type of vegetation manipulation
9) past use or abuse by man
10) wildfire and flood history
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In proposing a matrix evaluation format, the publication lists the
following information needs: watershed size, soil types, soil mass
failure hazard, soil surface erosion hazard, geologic type, drainage
pattern, mean slope, habitat type, commercial timber type, channel stability,
stream order, basin orientation, stream gradient, on-site water use, off-
site water use, past watershed natural activities, past watershed man
activities, mean basin elevation, mean basin precipitation, mean basin
runoff, hydrologic condition, proposed method of logging and proposed
silvicultural treatment. An overall consideration is the conformance to
state water quality standards.
The report lists five alternatives for meeting established water
yield increase guidelines, as follows:
1) Increase or decrease the area or size of vegetation to be
removed
2) Modify the method of removal, i.e., clearcut vs. shelterwood
harvest
3) Collect additional soil, geology and hydrology data, i.e.,
refined input data
4) Modify the harvest by energy slopes to desynchronize the
increased water yield
5) Exceed guidelines after inclusion of mitigation such as
these measures: (a) sediment basins, (b) road stabilization,
(c) debris clearing, (d) bank stabilization, (e) progressive
revegetation, (f) high lead logging, etc., (g) buffer strips,
(h) channel stabilization, (i) eliminate spring logging, (j)
modify method of harvest
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The report presents a useful "Stream Reach Inventory and Channel
Stability Evaluation" procedure and form which is presented in Tables
12 and 13. The report also goes into detail concerning the calculation
of acceptable limits for increases in yields and peak flows, primarily
based on channel characteristics and soil/slope information.
These procedures were developed primarily as a part of planning
programs for the Nea Perce and Panhandle National Forests. The "Forest
Hydrology, Part II" handbook details four variations of the procedure.
Currently, there is disagreement concerning the effects of clearcutting
on peak flows and channel erosion. Research has shown that water yield
and peak flows generally increase in areas of extensive vegetation
removal (Rothacher and Glazebrook 1968; Helvey 1972 and Anderson and
Hobba 1959). The important question concerns the effect of such increased
peak flows on channel erosion. This depends on the specific stream site,
but the general significance in the northwest is unknown. However, since
the procedure outlined above is directed toward minimizing the impact,
if no channel erosion potential exists the procedure would not be used.
While the methodology is still in the development stage, the basic approach
is sound. The subregional significance needs to be determined, but
channel erosion analysis should be included in forest management planning,
at least on a planning-unit basis.
AQUATIC OR MARINE ECOSYSTEM MODELING
Numerous models are available for predicting the effects of pollutant
discharges on a water body. Most of these models synthesize the
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Table 12
Taken From: Forest Hydrology, Part II
USDA Forest Service
R-l STREAM REACH UIVsTnOtT and CHAHHEL STABILITY EVAU1ATIQH
LOCATION
Forest
No.
Observer (s)________
Reach Description 4
Other Identification.
Aerial
Photo Ho.
Survey
Date
Coordinates
& Identification
P.W.I.
W/8 Ho..
INVENTORY MEASUREMENTS & ESTIMATES*
Stream Size Survey Date Width.
& Discharge At Maximum
Gradient X Sinuosity ratio.
Channel Flow Pattern
Soils Description
Landform and/or Geologic Type_
Vegetative Type
Number of debris Jans 4/or fish blocks/mile.
_. Upstream watershed Impacts (Types)_
Sire Composition of
Bottom Materials
(Total to 1001)
(1. Expos.
2. Large
3. Small
4. Large
Exposed bedrock....
boulders, 3' + Ms...
boulders, 1-3'.....
rubble, *"-12"....
Westher and Other Remarks
5. Small rubble, 3"-6"....
6. Coarse gravel, l"-3"
7. Fine gravel, 0.1"-!"...
8. Sand, silt, clay, muck... %
INSTRUCTIONS
Use a separate rating form for each length of stream that appears similar. Complete the Inventory Items
above using maps, aerial photos, and field observations and measurements. On the opposite side of this
psge, the channel and adjacent flood plain banks are subjectively rated, Item by Item, following an
on-the-ground Inspection. Circle only one of the numbers In parentheses for each Item rated. If actual
conditions fall somewhere between the conditions aa described, cross out the number given and below It
write In an Intermediate value which better expresses the situation. Don't key In on a single indicator
or a small group of Indicators but use them all for the most diagnostic value. The Indicators are Inter-
related so don't dwell on any one Item for long. Do the best you can and the pluses and minuses should
balsnce out. Keep In mind that each Item directly or Indirectly seeks to answer three basic questions:
(1) What are the magnitude of the hydraulic forces at work to detach and transport the various organic
and Inorganic bank and channel components? (2) How reslstent are these components to the recent atream-
flow forces exerted on them? (3) What Is the capacity of the stream to adjust and recover from po-
tential changes In flow volume and/or increases In sediment production? Use your Instruction booklet!
DEFINITION OF TERMS AHD ILLUSTRATIONS
Upper Bank - That portion of the topographic croas sectlc
from the bresk In the general slope of the surrounding Ian
to the normal high water line. Terrestrial plants & animals
normally Inhabit this area.
Lower Banka - The Intermittently submerged portion of the
channel cross section from the normal high water line to the
water's edge during the simmer low flow period.
Channel Bottom - The submerged portion of the channel croaa
section which is totally an aquatic environment.
H.«t> W«t*r Une
---Normal HighW»t«rLmtr — •
Ck»«n«l S»t»/.
«.na«HiaiDew«m
Stream Stafle - The height of water In the channel at the time of rating Is recorded on the top half of
this page using numbers 1 through 5. These numbers, as shown below, relate to the surface water elev-
ation relative to the normal high water line. A decimal division should be used to more precisely
define conditions, le. 3.S means 3/4ths of the channel banks are under water at the time of rating.
~*~^0&^* ~—5 • Flooding. The flood plain Is completely covered.
-fiir^ -4 - High. Channel full to the normal high water line.
-"* - Moderate. Bottom and % of lower banks wetted.
2 « Low. Bottom covered but very little of the lower banka wet.
1 - "Dry". Essentially no flow. Water may stand In bottom depressions.
Use an asterisk behind all estimates that could be measured but weren't.
184
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Table 13
Taken From: Forest Hydrology, Part II
USDA Forest Service
R-l STREAM CHANNE
LUATION FORM
CQ.
Item Rated
UPPER BANKS
lass Wasting
(Existing or Potential)
(Floatable Objects)
Dd:ik Protection
from
Vegetation
LOWER BANKS
Cl .mel Capacity
Bank Rock Content
%structions
Flov Deflectors
Sediment Traps
Cutting
Deposition
BOTTOM
lock Angularity
Brightness
Consolidation or
Particle Packing
Bottom Size Distribution
S. Percent Stable Materials
Scouring and
Deposition
Hinging Aquatic
Vegetation
Stability Indicators by Classes
EXCELLENT
No evidence of past or
potential for future mass
wasting Into channels.
Essentially absent from
immnhace channel area.
901 + plant density. Vigor
and variety suggests a
deep, dense root mass.
Ample for present plus some
increases. Fi.ak flows con-
tained. W/D ratio <7.
65% + with large, angular
boulders 12" + numerous.
Rocks, old logs firmly
embedded. Flov pattern
of pool & riffles stable
without cutting or
deposition.
Little or none evident.
Infrequent raw banks less
than 6" high aenerallv.
Little or no enlargement
of channel or point bars.
Sharp edges and corners,
plane surfaces roughened.
stained. Gen. not "bright".
Assorted sizes tightly
packed and/or overlapping.
No change In sizes evident.
Stable materials 80-1001.
Less than 5% of the bottom
affected by scouring and
deposition.
Abundant. Growth largely
moos like, dark green, per-
COLUMN TOTALS — - [
(3)
(2)
(T,
(1)
(2)
(2)
(4)
(4)
a)
tt>
(2)
(4)
(6)
(1)
GOOD
Infrequent and/or very small
Mostly healed over. Low
future potential.
Present but mostly small
twigs and limbs.
70-90% density. Fewer plant
species or lover vigor
deep root mass.
Adequate. Overbank flows
rare. Width to Depth (V/D)
ratio 8-15.
40 to 65%, mostly small
boulders to cobble 6-12".
Some present, causing
erosive cross currents and
minor pool filling. Obstruc-
tions and deflectors newer
and less firm.
Some, intermittently at
outcurves & constrictions.
Raw banks may be up to 12".
Some new increas in bar
formation, most from.
coarse gravels.
(P)
(6)
(4)
(6)
(2)
(4)
(4)
(8)
(8)
Rounded corners A edges,
surfaces smooth & flat.
Mostly dull but may have
up to 35% bright surfaces.
Moderately packed with
some overlapping.
Distribution shift slight.
Stable materials 50-80%.
5-301 affected. Scour at
constrictions and where
grades steepen. Seme
deooaition In oooLs.
Common. Algal forms in low
velocity & pool areas. Moss
here too and swifter waters^
(2)
<2!>
(4)
(8)
12)
(2)
FAIR
Moderate frequency & size,
by water during high flovs.
Present, volume and size
are both increasing.
50-70% density. Lower vigor
and still fewer species
form a *c
<5>
(6)
112)
:is)
(3)
— tn
POOR
Frequent or large, causing
sediment rearly yearlong OR
Imminent danger of same.
Moderate to heavy amounts,
predominantly larger sizes.
<507. density plus fewer
species & less vigor indi-
cate poor, discontinuous,
and shallow root mass.
121
(8)
12)
Inadequate. Overbank flows
common. W/D ratio >25.
^ 20% rock fragments of
gravel sites, 1-3" or lens.
Frequent obstructions and
deflectors cause bank ero-
sion yearlong. Sed. traps
full, channel migration
occur! n«.
(4)
(8)
(8)
Almost continuous cuts,
some over 24" high. Fall- p5)
ure of overhangs frequent, j
Extensive deposits of pre- 1
domlnately fine particles. 116)
Accelerated bar development.!
Well rounded in all dimen-
sions, surfaces smooth.
Predominately bright, 65T +,
exposed or scoured surfaces.
No packing evident. Loose
assortment, easily moved.
Marked distribution change.
Stable materials 0-20?..
More than 50% of the bottom
in a state of flux or change
nearly yearlong.
Perennial types scarce or
absent. Yellow-green, short
term bloom may be present.
14)
(4)
(8)
i&)
:24>
(4)
-*•[__
Add the values in each column for a total reach score here.(E. + C. + F. + P._
Reach siorc .n: OS-Excellent. 39-76-Cood, 77-114- Fair, 115+-Poor.
Rl-2500-5 (6/73)
-------
concentration of pollutants at critical locations, For a lake, reservoir or
marine environment, these locations may vary by depth and distance from
the discharge, or be primarily determined by critical aquatic or marine
life areas. For stream environments, the evaluation points are downstream
from the pollutant discharge, generally at critical locations such as
just above a community water supply or major tributary confluence.
Water quality or aquatic and marine ecosystem models can be very
beneficial for predicting the effects of silvicultural practices on water
bodies. Through reiterative analysis, alternative land use and management
schemes can be evaluated for water quality impact.
One of the most useful models for stream ecosystems was developed by
Chen and Orlob (1972). The data requirements for this model are very
specific and the program must be adapted to the particular stream involved.
This type model differs from the water quality types in that the biological
or aquatic life effects are examined as contrasted to water quality per
se. Essentially, the same model is available for lake, reservoir or
marine environments.
Planning
Planning is the process of analyzing and evaluating the implications
of potential future actions, followed by the selection of a plan that can
best realize desired goals. Planning is best summarized as the process
of forethought and strategy selection. It must be followed by implementa-
tion, meaning the transformation of the plan into action programs, projects
and performance criteria. Table 1-4 illustrates a basic planning methodology,
186
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PUBLIC
(REVIEW & INPUT)
Table 14
Basic Planning Methodology
nH
DETERMINATION OF CONDITIONS
Goals, Problems, Needs and Opportunities
(INFORMATION COLLECTION
| ANALYSIS]
FORMULATION OF
ALTERNATIVE PLAN ELEMENTS
|IMPACT PREDICTION]
DETERMINATION OF
PRIORITIES
AND OBJECTIVES
1
SYNTHESIS OF
ALTERNATIVE OPTIMUM PLANS
i^| SELECTION |
IMPLEMENTATION
Action Plans and Programs
Policies and
Performance Criteria
187
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which is most applicable to broad-scope public planning programs. However,
the same basic method, with greater or less emphasis on different elements,
would apply to site (or project) planning on private and public lands.
BASIC METHODOLOGY
Water quality planning on forest lands should be integrated into a
comprehensive planning effort and not treated as a separate process. The
planners responsible should be interdisciplinary and have the capability
to include the following considerations in the planning:
o aquatic biology and water quality
o forestry
o soils/geology
o hydrology and geohydrology
o fisheries and wildlife
o engineering
o economics
In addition, the planning should include consideration of the pertin-
ent federal, state and local laws, ordinances and requirements. For public
lands, the most efficient approach to accomplish this may be to utilize
interagency planning teams with representatives of fish and wildlife,
planning and environmental agencies. For nonpublic lands, formal inter-
agency planning teams may not be feasible. However, the interdisciplinary
nature of the effort is still important, and early involvement of state,
federal and local regulatory agencies can save time in the long run.
The planning methodology depicted in Table 14 should not be interpreted
188
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to imply that all elements of forest land planning must proceed simul-
taneously through this procedural logic. The basic data required for
decision making in certain planning areas may "be adequate much earlier
than in other areas, and the needs more critical. Most importantly,
some types of early decisions do not preclude other important planning
options. Once the information base is adequate for these limited-
committal decisions, it may be acceptable, and often desirable, to
initiate limited action early in the process, provided that proper plan
selection procedures are followed. For example, it may be desirable and
acceptable to revegetate the critical slope areas within a previously
logged watershed before finalization of a comprehensive land use plan
due to (a) critical water quality needs for early revegetation, (b)
program scheduling needs and early availability of manpower and/or funds,
and (c) important management options not being foreclosed by the action.
The following criteria should all be satisfied in order for such
early decisions to be advisable:
o other important management/planning options are not
precluded (or foreclosed),
o the information base is adequate for the type of decision
contemplated, and
o delayed action would result in adverse effects on the
basic physical resources involved
An important consideration affecting the desirability of such
early decision making would be the availability of financial or manpower
189
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resources now, that might not be available at the time of plan finalization.
The planning process must be a continuing program, not only to continue
the planning in new geographic areas, but to refine, revise or expand pre-
viously made planning decisions in response to new or feedback information.
The success of planning and implementation programs should be monitored
and evaluated continually.
The following discussion follows the methodology presented in Table 14.
Basic Information and Analysis
The first phases of a forest land use planning process should involve
(a) a determination of the conditions which will constrain the planning,
(b) tiie formulation of general goals, and (c) collection and analysis of
the information and data pertinent to the study. Some information required
for the planning will be available, but additional data may be necessary
(refer to the discussion under "Information Requirements").
A preliminary overview of the study area's intrinsic physical/environ-
mental, social and economic qualities is needed to determine the goals,
problems, needs and opportunities requiring emphasis. Public involvement
is advisable during this phase, which in effect is the first attempt to
set the direction of the study.
Alternative Plan Elements
During this phase, the planning study is divided into logically
separable elements (e.g., logging method selection), analyzed, and the
impact and implications predicted. Such impact prediction should include
environmental, social, economic and financial analyses. All such elements
and their impacts are interrelated, necessitating a reiterative type of
190
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analysis where the effects of one alternative and its mitigation measures
are taken into consideration in the analysis of other elements. The
number of interrelationships requiring separate analysis, however, can
usually be minimized to allow a reasonably simplified analysis procedure.
Where this is impossible, computer models, particularly -for impact pre-
diction, are valuable if available.
Priorities and Objectives
One of the most important planning phases involves the determination
of all the implicit and explicit objectives and priorities of the study.
These study "directives" must be understood by the planning team and
interested parties external to the planning effort. Public understanding
is important if the land involved is public, if public agency approval
is required, or if public resources are affected.
For water quality planning, recent national goals and objectives
have been established by Congress through the Federal Water Pollution
Control Act Amendments of 1972 (Public Law 92-500). In addition, all
states have enacted legislation that defines water quality requirements.
Additional requirements have been set through laws and regulations ad-
ministered by federal or state forest resource agencies. Many local
land use (planning and zoning) agencies also have water quality goals or
programs. These local water quality requirements are generally embodied
in local ordinances which are legally binding on private, state and
federal lands (P.L. 92-500, Section 313).
Goals, and the more specific objectives, should be outlined for each
land unit according to its characteristics and values in addition to the
goals mandated by federal, state and local laws. Throughout the planning
191
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process, choices and tradeoffs will be made according to value judgments
by the planning team. The criteria for choosing one alternative over
another should be explicit and formulated early in the process.
Synthesis
Once the potential elements of the final plan and the implications
are understood, alternative plans can be formulated, based on the alterna-
tive plan elements previously analyzed. Such alternative plans should
represent a range of methods to achieve various (possibly conflicting)
goals. Examples of such goals include resource conservation, regional
development, national economic stability, private economics and environ-
mental quality.
Selection
Once the alternative plans are examined, a selection can be made. The
final plan may be one of the alternatives examined, or a combination of
parts of various plans. The examination of alternatives can serve to stimu-
late thinking on entirely new approaches.
Implementation
Planning is no more than the means to an end — the initiation of
efficient, effective programs, projects or policies. Plan implementation
can involve, for example, broad or specific policies for guiding forest
management decisions, action plans such as a watershed rehabilitation plan,
financial or funding programs, and performance criteria by which to judge
the logging methods used within the project area.
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Public Involvement
Informing the interested public, and public agencies, throughout
the planning effort and encouraging their comments and involvement is
beneficial, and for public lands, necessary. In this way, individuals
(or agencies) are given the opportunity to express their values and
concerns and the planning process is strengthened through early exposure
to criticism and a broad spectrum of information. In the case of private
lands the need is often different, however, the involvement of the public
through various public agencies is usually required.
SITE SPECIFIC PLANNING
The "Basic Planning Methodology" shown as Table 14 has numerous
variations, including methods more applicable to small private forest
units or specific projects (site specific planning). The basic planning
logic should be similar, but differ in the emphasis placed in each element,
The following describes the major potential differences:
a) public input would probably be limited to the necessary
public agency approvals (for private lands),
b) the basic goals on private lands would cover a more
narrow range, with emphasis on economics,
c) alternative plan (and plan element) formulation would
be minimized, and
d) the "planning team" may consist of a forestry consultant
only (on small private land ownerships)
The basic need is for information review, including laws and regula-
tions, with an examination of alternatives before finalizing the plan or
project. Specialized information is required of the type and sources
listed in Table 9.
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Sensitive Areas and Facilities Location
Planning is the most important key to preventing water pollution from
timber harvesting, residue management and reforestation. The most important
consideration in such planning is avoiding or minimizing the soil and
vegetation disturbances on or affecting sensitive areas.
Such areas include:
o stream channels
o stream banks and water influence environs
o marine, lake or reservoir environments
o steep slopes or unstable soils
A complementary and equally important planning objective is the loca-
tion of facilities and layout of logging systems in a manner that not only
avoids and protects sensitive areas, but capitalizes on land that is (l)
the most stable, and (2) has a minimum potential for producing water
pollution impacts.
STREAM CHANNELS
Summary
Based on the available information, the following criteria for stream
channels would protect the quality of waters on, or affected by, timber
harvest areas:
o Utilize experienced fisheries management specialists and State
Fish and Game Department personnel to determine (l) the importance
194
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of the stream for fisheries and water quality, and (2) special
management requirements for stream channel protection.
o Remove all debris and residue attributable to timber harvesting
from below the high water level, except where such debris will
definitely improve stream channel structure.
o Avoid using construction equipment or skidding logs in or across
streambeds; yard across streams only if logs are fully suspended
above the stream channel.
o Fell and limb trees away from all streams and watercourses.
o Avoid channel alterations.
o Avoid locating landings, slash piles and other
facilities or residuals within any watercourse.
o For stream channels or watercourses in which flow is inter-
mittent and fish spawning or rearing is negligible:
a) remove slash and other timber harvest debris below the
high water level
b) hold surface disturbance to a minimum
c) minimize the operation of logging and construction
equipment below the high water level and allow such
operation only during no-flow periods and if down
stream fisheries will not be affected.
o Obtain written concurrence for a specific plan from state
water rights, fisheries and environmental agencies before
diverting water from, or altering, any stream.
o Provide for the protection and maintenance of stream side
vegetation (as discussed later).
195
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Discussion
In addressing the question of guidelines for applying forest practice
rules relating to Class II streams in the Northwest Forest Region of Oregon
(streams of little or no value for fish spawning or rearing, but which
affect downstream water quality), the Oregon Department of Forestry con-
cluded the following:
1• Positive preventive measures must be taken to keep the
material out of streams.
2. The greatest concern is the potential for 'sluice-outs' which
could carry material to Class I streams.
3. Stream clearance requirements can be relaxed where:
a. there is no 'sluice-out' potential,
b. 'sluice-outs' cannot reach Class I Streams.
4. Due to steeper gradients, low flows and narrow canyons
characterizing Class II streams, water quality problems,
particularly with regard to dissolved oxygen and temper-
ature, appear to be minimal.
5. Where cleanup is required, it should be done in a manner
least likely to create undesirable disturbance.
6. Presence of slash in streams can have a beneficial effect
on some streams, through the sediment trapping and shading
capabilities.
THE FOLLOWING GUIDELINE IS INTENDED TO AMPLIFY THE ABOVE POINTS:
Positive Preventive Measures
l) Trees should be felled away from Class II streams whenever
possible. Improper felling practice is probably the greatest
single contributor to debris in Class II streams. Because of
the usual time lag between felling and yarding, limbs and tops
which fall into streams may cause damage to water quality
which persists even after yarding.
196
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2) When it can be done, trees which do fall into streams
should be yarded out at least to a point above the high
water level before removing limbs and tops. Fine material
such as needles has a greater effect on dissolved oxygen
than does larger material.
3) Avoid yarding across Class II streams where possible, to
minimize disturbance of the bed and banks.
One of the most comprehensive assemblies of guidelines for stream
channel protection is being applied by the U. S. Forest Service Inter-
mountain and Northern Regions. Portions of these criteria are mitigative
measures and a selected few are listed for cases where some stream altera-
tion or disturbance is unavoidable.
Where channel changes are deemed necessary, natural
channel velocities shall not be increased in the affected
stream reach. This will be assured by installing drop struc-
tures, by constructing acceptable meanders, or by other
approved methods. Where drop structures are installed they
shall be designed to permit fish passage, if this is an
established occurrence,
Construction and other activities affecting channels
above spawning areas shall be deferred if they will ad-
versely affect eggs or alevins in the gravel.
During construction and other activities affecting
channels, areas containing anadromous fish redds shall
be protected.
When channel changes or alterations are the best
alternative, mitigating measures shall be provided to
foster replacement of the aquatic habitat to as near
natural condition as is possible.
When channel changes are unavoidable, new channels
shall be completed, including scour and erosion protection,
before turning water into them.
Log landings shall not be located adjacent to stream
channels or on areas where surface runoff will discharge
directly into the channel.
197
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Construction shall be avoided during wet season or other
undesirable runoff periods to minimize sedimentation directly
into streams. If construction is essential during such periods,
sedimentation damage will be minimized by installing debris
basins or using other methods to trap sediment.
STREAM BANKS AND WATER INFLUENCE ENVIRONS
Summary
One of the most important forest land areas to protect for water quality
purposes is the land adjacent to streams and watercourses. The values
of stream-side vegetation for various considerations has been discussed
throughout Chapter 4. In summary, retaining vegetation and minimizing
soil disturbance in such zones can significantly reduce water quality
impacts by:
o retention of stream shading and temperature regimes favorable
to salmonid fisheries
o minimization of drop impact, soil particle entrainment and
subsequent sedimentation from the zone immediately adjacent
to the stream during periods of high flow or intense rainfall
o interception and deposition of sediment, particularly the
larger particles, in the small rivulets resulting from
major storms
o reducing the risk of channel damage due to equipment operation,
skidding and slash piling in the stream
o aiding in the control and interception of debris
Based on the information available, the minimum buffer zone widths
(one-side) for protecting water quality would generally fall within the
198
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following range, depending on site characteristics, water quality
standards, fishery to be protected and streamflow:
1. Major perennial streams 40' - 200'
2. Minor perennial streams 20' - 50'
3. Important intermittent streams 10' - 30'
For discussion purposes, major perennial streams are defined as those
which flow year-round and have a minimum flow generally greater than
3 cfs. Minor perennial streams are defined as those which flow year-
round and have a minimum flow generally less than 3 cfs. Important
intermittent streams are defined as those which do not always flow year-
round, but which may be important for water quality downstream or in
some phase of fish rearing.
In most cases the optimum width will vary considerably along the
length of a stream, and generally be greater than the minimum. Considera-
tions in the determination of buffer zones include the following:
1) For temperature control the timber volume retained is
relatively unimportant. The important factors are angular
canopy density and shade provided. (See Brazier and Brown
1973. )
2) Some intermittent streams have been found to be important
for fish rearing (for Alaska see USDA Forest Service et al
n.d. ).
3) Site conditions immediately adjacent to the stream (e.g.,
slope) are particularly important when sediment interception
is an objective (see Trimble and Sartz 1957).
199
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4) The water quality values of buffer zones vary in significance
from stream to stream.
5) Selection cutting with minimum disturbance logging may offer
sedimentation values of similar or greater water quality value
than buffer zones with clearcutting and high disturbance logging
(Lantz 1971, Hornbeck 1967, Reinhart 1964).
Discussion
The question of "buffer zones" or "leave strips" has frequently been
discussed and examined by both researchers and practitioners, particularly
during the past five years. It must be stressed that this report deals
with such zones only insofar as they contribute to the protection of water
quality. Other important forest management goals, e.g., wildlife protection,
may also require the retention of the vegetation adjacent to streams. Such
requirements will not always coincide with the water quality requirements
for buffer zones. The primary point is that there are multiple needs for
maintaining vegetation along streams that should be analyzed separately
and then synthesized.
Some minimum requirements for buffer zones along spawning and rearing
streams are advisable in the subregions covered by this report. However,
such requirements may vary considerably from one subregion, or stream, to
another because of differences in topography, hydrology, meteorology,
silvicultural practices, soils, fisheries and geology. In one subregion
the primary objective may be to protect against temperature increases,
while in another, erosion and sedimentation may be most important.
200
-------
The ideal approach involves minimum requirements, based on a range
of stream classifications, that are subject to enlargement or optimization
through comprehensive interdisciplinary planning on a stream-by-stream
basis. The objectives of such planning and revision should be to achieve
a level of water quality protection that (l) adequately protects the
fishery, (2) meets state and federal water quality requirements, and (3)
provides an equal or greater protection than the minimum specified. With
this procedure, the differences in stream use and classification can be
recognized.
Different conclusions have been reached concerning the best approach
to determine buffer zone widths. Some have warned against the setting
of blanket optimum or minimum widths (Narber, Mason and Mundy 1973,
Streeby 1970). Others have recommended such optimum or minimum widths
(FWPCA 1970, Anderson 1973, Jones and Stokes 1972).
It has been suggested by Trimball and Sartz (1957) that a logging
road filter strip should be a minimum of "25 feet plus 2 feet for each
one percent of slope between stream and road." A curve was prepared
showing the relationship between degree of slope and the distance sediment
is carried by storm runoff.
Of major importance is the varying significance of temperature
increases and sediment interception from one subregion to another. In
the Idaho Batholith (Intermountain and Northern Idaho subregions), sedi-
ment interception by buffer strips has been found to be important (Haupt
and Kidd 1965). Due to the generally low water temperatures in these
mountainous areas, stream side vegetation for temperature control is
probably of less importance than in western Oregon.
201
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It has been concluded by Brown (1972) that,
"One popular alternative (.for minimizing sedimentation)
is a strip of vegetation between the road or harvest area
boundary and the stream. Such a strip is often called
a buffer strip. A "no-entry" zone is an excellent tech-
nique for protecting channel banks and the stream bed
during logging. But such a. technique is of little value
in handling erosion from side slopes above the buffer in
most of the mountainous West. Vegetative filtration of
soil materials borne in runoff water by a buffer strip
assumes that sheet flow similar to that occurring on
eastern agricultural soils is the predominant erosion
mechanism. In most forest watersheds, the highly
dissected topography and rough surface precludes such flow.
Water quickly finds its way into rills or channels. These
converge to form larger channels. Since channel flow
predominates eroded materials are carried through a buffer
strip."
Buffer zones offer protection from channel and surface erosion in the
area immediately adjacent to streams. They also intercept the sediment in
the small rills and rivulets which originate just above the buffer strip.
Large flows would not be significantly affected by buffer strips and
such sedimentation would have to be controlled by other means.
MARINE, LAKE OR RESERVOIR ENVIRONMENTS
Summary
The management for water quality purposes of estuaries, lakes or
reservoirs and the adjacent land and vegetation has not been the subject
of extensive research. Such shoreline management has most often been
practiced for esthetic, wildlife or recreational purposes rather than
water quality per se.
While the importance of shoreline protection to water quality is
202
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apparently greater for small to medium-sized streams than for estuaries,
lakes or reservoirs, this general rule can be expected to have exceptions.
Small fresh- or salt-water bodies, particularly shallow spawning or
rearing areas, can present a high potential for water quality degradation.
This depends on:
o exposure
o normal temperature regime
o hydraulic characteristics (flushing)
o soil/slope characteristics
o relative amount of the sensitive area affected
For example, a shallow, narrow estuarine area normally provided with
shade by tall trees along a steep, erodible shoreline to the south could
be subjected to dramatic thermal and sedimentation impacts if the vege-
tation is removed and the soil extensively disturbed. If such an area
is an important rearing area for fish, the biological impacts could be
severe. Since such areas are generally less active hydraulically than
streams, under certain conditions the potential for adverse effects could
be greater.
The following would tend to minimize the adverse effects of timber
harvesting and transport activities on the water quality of marine, lake
or reservoir environments:
o locate the important aquatic or marine habitat areas early
in the planning
o determine the width of vegetation needed as a "buffer zone"
203
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o use dry land storage and barging of logs whenever possible.
If storage in marine or fresh waters is required, minimize the
number of sites and the volume of logs (and time period)
stored
o avoid activity in the vicinity of important habitat areas,
bays and intertidal or shallow areas
Discussion
The U. S. Forest Service proposed the following three guidelines for
the Southern Chilkat Study Area, Tongass National Forest, which exerts a
significant influence on a productive marine environment:
o Consult a biologist prior to any developmental action along the
shoreline and estuarine areas.
o Give preference to dryland storage and barging in any logging
activity.
o Exclude any timber harvest within approximately a one-fourth
mile fringe of the shoreline except for salvage of blowdown,
insect, disease, or fire damaged timber.
The National Marine Fisheries Service (NOAA), Juneau, Alaska, has
recommended the following to reduce the adverse impact of fisheries from
log dumps and raft storage areas:
1. Maximize the distance between the mouths and intertidal chan-
nels of anadromous fish streams and the sites.
2. Maximize the distance between tide flats and subtidal beds
of aquatic vegetation and the sites.
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3. Use the steepest shores having the least intertidal sub-
tidal zone.
4. Minimize disturbance of the shoreline as a result of clearing,
road building and other activities that might produce silt or
otherwise disrupt the estuarine environment.
5. Minimize storage time for rafted logs before transport to
the mill.
6. Minimize the number of active dump sites arid log storage
areas in any given bay or bay complex.
7. Minimize the filling of intertidal and subtidal areas for the
construction of log dumps, fuel transfer facilities, equipment
loading ramps, etc.
8. Minimize the use of intertidal areas as a source of borrow.
9. Minimize interference with other established uses such as com-
mercial and sport fishing, hunting and anchorages for commercial
and recreational boats.
10. Whenever possible locate sites outside bays, along straits
and channels.
11. Locate dump sites in deep bays rather than in shallow bays.
Select bays without sills or other natural restrictions to
tidal exchange.
12. Locate dump site near mouths of bays rather than at heads of
bays unless the environment at the mouth of the particular bay
in question has some special significance.
13. Use the deepest water possible for booming grounds and log
raft storage areas.
14. Select sites that accomodate future timber development without
requiring continual relocation.
Recommendations on storage, handling and transportation of logs on
public waters were made by the Industrial Forestry Association (1971)
as follows:
1. Logs should be put into water by easy let-down means.
2. Logs should be bundled before being put into public water where
the log flow pattern of the operation makes it practical to
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accomplish log handling including sorting logs by species, grade,
use and specific destination prior to the time the logs are put
into the water.
3. Accumulations of bark and other debris from the land phase of log
handling of log dumps or mill sites should be kept out of the water.
<4. Keep the volume of logs stored in water and length of storage at
a minimum.
STEEP SLOPES AND UNSTABLE SOILS
Summary
Areas of steep slopes (those generally in excess of 50$, see Table 15),
or unstable soils present potential water quality problems that are best
avoided whenever possible. The most advantageous approach involves identi-
fying the sensitive soil and slope areas and allocating them to low distur-
bance uses. It is advisable to avoid road construction and minimize timber
harvest in such areas. Information pertinent to the study of erosion and
sensitive soils as affecting water quality can be found in Chapter 4.
The following summarizes the water quality protection criteria for
timber harvest, logging, residue management and reforestation:
o A land systems management plan, including programs for minimizing
soil loss, erosion and mass soil failure, should be developed for
all forest land units by experienced soil scientists, hydrologists
and geologists.
o Avoid skidding in ravines or V-notches.
o Limb logs before yarding if they are to be ground-skidded.
o Apply zone-sensitive saturation (max/min) and slope limits to each
type of logging used, particularly tractor logging.
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o Minimize soil disturbance through the use of aerial logging
methods such as skyline, running skyline, helicopter or balloon
systems in steep-sloped or unstable soil zones (e.g., the Idaho
Batholith).
o Consider the use of slash for soil protection purposes.
o Consider limiting logging to periods when snow cover can provide
protection to the soil and understory.
Discussion
In a report concerning the California Forest Protective Law, Jones
and Stokes Associates, Inc., has proposed certain standards to the Water-
shed Conservation Board that pertain to critical areas and the location
of facilities as follows:
The Board shall set permissible soil loss levels for the dis-
trict areas.
The Board shall monitor logging operations and shall report
individual and cumulative soil losses attributable to logging.
Permittee shall include an erosion control program in each
logging plan describing in detail the facilities and techniques
used to keep soil losses at permissible levels.
Permittee shall pay the cost of erosion monitoring.
The U.S. Forest Service and Alaska Departments of Fish and
Game and Natural Resources (n.d.) have outlined criteria for minimizing
erosion and sedimentation from steep slopes or unstable soil areas (in-
cluded with other fish habitat protection criteria).
The Oregon office of the Soil Conservation Service prepared a paper
entitled "Agronomy Practices Standards and Specifications for Critical
207
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Area Planting." These standards can be applied to an area of surface dis-
turbance with some modification for each site.
W.J. Kidd, U.S. Forest Service, in studies on the Idaho Batholith,
summarized his research on 569 intervals of 105 logging skidtrails as
follows:
1. Erosion is greater and rate of healing is slower on soil derived
from granite than on soil from basalt.
2. More soil is eroded from skidtrails unavoidably located in ravine
bottoms than from trails on sidehills.
3. Control structures that divert water off the skidtrail onto undis-
turbed forest floors are superior to those that only retard water
movement and filter out sediment along the skidtrail.
4. Any increase in spacing between control structures is accompanied
by increase in soil movement.
5. Optimum spacing between erosion control structures depends on the
percent of slope, whether location of the skidtrail is on a side-
hill or in a ravine, and the soil parent material.
Kidd concluded that proper treatment of bared skidtrails after logging
reduces the hazard of potential erosion. He also concluded that all types
of erosion control structures on skidtrails were generally ineffective in
ravine bottoms. Water diverting structures (log water bars and cross ditches)
are more effective than the sediment filtering methods (slash dams and lop-
ping and scattering of slash).
Gonsior and Gardner (1971) proposed design criteria for the improve-
ment of logging roads in areas subject to slope failure. Road design has
been dealt with in a previous report (EPA 1975).
The Tongass National Forest (1974) proposed as a means of reducing
soil disturbance to, "Utilize winter snow conditions and frozen ground to
minimize soil disturbance during timber harvest."
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Hopkins (1957) made the following observations concerning the minimi-
zation of soil disturbance:
Limb the logs before yarding. Be sure the loggers know the
location of the skidtrails. Then, they can place the trees so that
yarding crews can roll and skid the logs with a minimum amount of
soil disturbance.
Slash disposal is often considered soley as a method of reducing
fire hazard. Don't overlook the opportunity, however, for using
slash from tops and other debris to minimize or prevent erosion
damage. Slash and litter properly placed in skidtrails will lessen
soil movement and divert excess water out of trails; improperly
placed, it is ineffective, wasteful of effort, and may even increase
erosion. Place the material in good contact with the soil and
the larger pieces at such angles that they will lead water out of
the skidway at frequent intervals. Portable chippers, now in use
on two of the southern California national forests, will chip slash
and blow a mulch into old skidtrails and other bare and unstable
areas. In general, the combination of good road location, well-
placed waterbreaks, and slash placement in critical spots, will
provide effective erosion protection.
The Federal Water Pollution Control Administration (1970) published
Table 15 and recommended the following soil protection criteria.
Limb all logs before yarding in order to minimize disturbance
of soil and damage to reproduction and water quality.
Avoid tractor yarding on all saturated areas and on all slopes
steeper than 30 percent. On critical soils, limit crawler-tractor
yarding to slopes of less than 15 percent.
Minimize logging road construction on very steep slopes or
fragile areas by using skyline or balloon yarding systems.
Consider the use of helicopters, balloons, or modified cable
systems for logging of areas that would have high conventional
yarding costs or for fragile, sensitive areas.
Take all possible care to avoid damage to the soils of forested
slopes, and to the soil and water of natural meadows as well. Min-
imize this damage by operating the logging equipment only when soil
moisture conditions are such that excessive damage will not result.
Limit tractor-built firelines to areas where they will not
involve problems in soil instability.
209
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Table 15
RELATIVE EROSION HAZARD OF LOGGING AREAS
IN RELATION TO SITE FACTORS
Site Factors
High
Erosion
Hazard
Moderate
Erosion
Hazard
Low
Erosion
Hazard
Sedimentary
Acid Igneous and Metamorphic Basic Igneous
Parent rock
Granite, Sandstone,
dlorite, vol- schist, shale,
canic ash, slate, con-
pumice, some glomerates,
schists chert
(Lava rocks)
Basalt, ande-
site, serpen-
tine
Soil
a/
Light
textured,—
with little
or no clay
Medium textured, Heavy tex-
with consider- tured, largely
able clay clay and adobe
Mantle
stability
Slope
Precipita-
tion
Vegetation
and other
organic mat-
ter on and
in the soil
Unstable
mantles
(cutbank
stability
Class V)
Steep
(over 50%}
Heavy winter
rains or in-
tense summer
storms
None to very
little
Mantles of Stable mantles
questionable (Classes I, II
stability and III
(cutbank sta-
bility Class
IV)
Moderate Gentle
(20-50?) (0-20?)
Mainly snow Heavy snow or
with some light rain
rain
Moderate Large amounts
amounts
a
Soil texture refers to the size and distribution of the
mineral particles in the soil, the range extending from
sand (light texture) to clay (heavy texture).
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Silvicultural and Logging Systems Selection
The harvest or cutting method used has historically been based on
the silvics of the tree species present, the profitability of the system
used to extract the wood products, and the type of logging equipment
available in the region. However, the Silvicultural and logging systems
(and support facilities) directly effect water quality. By recognizing
this relationship, the water pollution potential of an area to be logged
can be reduced through the selection and layout of the Silvicultural and
logging systems.
SELECTION
Summary
To reduce the effects of timber harvesting on water quality, a few
general recommendations concerning selection should be followed:
1. Know the classes of stream within the cutting areas and the
degree of protection needed (see the Washington and Oregon
Forest Practices Acts 1974).
2. As a general rule, Silvicultural systems rank in the following
order regarding potential impact on water quality (most impactive
first).
a. clearcutting
b. seed tree
c. shelterwood
d. selection
(see Chapters 3 and <4)
211
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3. Choose the type.and size of logging equipment that will minimize
soil disturbance. Logging systems which have a much greater
range of potential impact than silvicultural systems, generally
rank in the following order (most impactive first):
a. tractor
b. high lead
c. skyline
d. running skyline
e. balloon
f. helicopter
(For additional information, refer to Chapters 3 and 4).
Discussion
Chapters 3 and 4 explain the various silvicultural systems including
advantages and disadvantages from a water quality standpoint and this
information will not be repeated here. A few points, however, will be
emphasized.
Rothwell (1971) has stated that:
"If clearcutting is employed, careful consideration should
be given in the logging plan to size and distribution, both
areal and temporal, of the cutting blocks. Generally speaking,
increasing the size of clearcut blocks and shortening the
cutting cycle will increase the potential for watershed damage.
Considering a watershed as a whole, large clearcuts and a
short cutting cycle concentrate the disturbance in area and
time and increase the impact on watershed values. Furthermore,
large cut blocks may create habitats that are difficult to
revegetate, thereby extending the recovery period.
Small cut blocks and longer cutting cycles may result in
the same total amount of disturbance, but distribution in
time and area reduces impact. In addition, residual vege-
tation maintains a forest environment and reduces and slows
runoff, erosion, and the amount of sediment entering streams."
212
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Harvesting with, small cut blocks requires careful examination as
total disturbance from roads and skid trails may increase the access
network and offset mentioned advantages.
The inherent characteristics of the selection system make it the
most desirable of the four silvicultural systems with regard to main-
taining high water quality when skillfully applied. The biggest drawback
from a water quality standpoint is the frequent return to the forest for
periodic or even annual cutting, resulting in small disturbances occurring
with greater frequency than with other silvicultural systems. Other
drawbacks, especially on westside areas (with the exception of some high
elevation fir—mountain hemlock types) and many eastside areas include:
o light requirements of some species e.g., Douglas-fir
o control of disease e.g., mistletoe
o terrain, species, tree damage, stand age
The selection of the logging system probably has more impact on water
quality than any other single factor. This is due to (l) the road density
requirements, which are largely set by the logging method and (2) the
surface disturbance resulting from the various methods- of transporting
logs to the landing.
lysons and Twito (1973) have enumerated some environmental and
silvicultural criteria for determining the type of logging method to be
chosen:
213
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Environmental and silvicultural criteria
Minimum landing area
Minimum access road density
capability to ya,rd extended distances
capability for uphill and downhill yarding
Minimum soil and water disturbance, including
soil compaction
Minimum impact of fish, wildlife and range habitat
Suitability for partial cuts and clearcuts
minimum damage to residual stand
Suitability for harvesting irregular-shaped settings
Suitability for clean yarding
Minimum energy consumptions and air pollution
Economic criteria
Minimum yarding cost
maximum production per man-day
maximum production per invested capital
minimum maintenance
Minimum sensitivity to yield per acre
minimum move-in cost
minimum set-up cost
Maximum return on stumpage
Minimum invested capital
Maximum reliability
Physical criteria
Minimum sensitivity to ground profile
Compatibility with the timber size
Minimum sensitivity to atmospheric conditions
Compatibility with health and safety codes
Compatibility with road restrictions
Helicopter and balloon logging disturb the watershed the least,
however, they are costly, more subject to climatic variables and present
some residue management and regeneration problems. They do offer
advantages in limited access or highly sensitive areas that might not
214
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otherwise "be subject to logging. One of the most advantageous logging
systems available is the running skyline. Its potential for use appears
to be much more extensive than helicopter or balloon logging (Burke 1975),
LAYOUT
Summary
Emphasis must be placed on avoiding or minimizing disturbances on
critical or sensitive areas. Proper timber management planning, however,
should also include the identification and utilization of the most stable
areas for locating logging facilities (e.g., landing) and systems (e.g.,
skidtrails ).
In most northwest subregions, the greatest potential for reducing
stream sedimentation related to silvicultural activities is in the mini-
mization of logging road and skidtrail densities. Much of the literature
concerning the Idaho Batholith, for instance, indicates that erosion and
sedimentation are heavily influenced by the extent of the area distrubed
by roads (Megahan and Kidd 1972 a and b).
Because of this relationship between density of logging roads and
sedimentation, one method offers significant advantages for water quality
protection. This is simply the reiterative layout on a topographic map
of alternative road systems with the concomitant harvest and logging
systems. This analysis allows the selection of a combination that
minimizes soil exposure due to cut/fill and road surfaces. Such road/
logging system selection should consider the following.
215
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o minimizing total road density and soil disturbance
o avoiding critical or sensitive areas
o taking advantage of stable areas
o long term harvesting plans for areas allocated to
intensive commercial timber use
o minimizing cut/fill surface area and ensuring that cut/fill
slopes are less than maximum limits set for each soil type.
In addition the following recommendations concerning the layout of the
silvicultural/logging systems and required support facilities (e.g. landings)
will reduce the adverse water quality impacts:
1. Design cutting areas and use logging systems that avoid yarding
across streams and minimize disturbance to stream bed and banks.
2. Use buffer strips of vegetation along streams to intercept
sediments and organic material, maintain normal water
temperatures and protect the stream from residue burning
and disturbance due to the operation of logging equipment.
3. Avoid logging of steep unstable slopes which have landslide
potential. Guidelines for identifying such areas are avail-
able for coastal Alaska (Swanston 1969), Oregon (Burroughs
et al 1974), and the Intel-mountain Subregion (Bailey 1972).
4. Develop general drainage plans jointly with all owners in
the vicinity of the operations.
5. Design with a minimum of roads.
6. Locate landings away from stream courses in well drained
areas.
7. Avoid falling trees into or across streams. Remove logging
debris from stream channels (see SAF 1959).
216
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8. Restrict cable logging to uphill yarding. Depending on soil
conditions, tractor or wheel skidding should not be used on
steep slopes and during or immediately after heavy rains or
snow melt periods.
9. Revegetate the area as soon as possible after logging.
Stabilize roads, skid trails and landings.
10. Periodically inspect drainage previously established through
proper construction of skid trails, landings, spur roads and
fire lines and maintain to avoid future site degradation
(SAF 1959).
11. Locate skid trails in tractor logging where they can be
drained and construct with discontinuous grades (SAF 1959).
12. Initiate and complete post-harvest operations as soon as possible
after logging.
13. Maintain good supervision of the personnel responsible for the
operations.
Discussion
Burke (1975) has stated that, "Improperly located and
constructed timber access roads and landings cause the
greatest adverse environmental impact of all activities
related to timber harvesting. It behooves the logging
engineer to consider all alternatives, both in location
and road standards, that:
1. Reduce amount of timber access road,
2. Reduce depths of cut and fill,
3. Eliminate necessity for steep, unnatural cut and fill
slopes,
<4. Eliminate necessity for steep road grades,
5. Reduce volumes of required excavation and embankment,
6. Eliminate indiscriminate sidecasting of excavated
materials on slopes, and
7. Reduce amount of right-of-way clearing required for road
or landing."
217
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The FWPCA (1970) proposed criteria for facilities location and
Hopkins (1957) stated the following as a guideline for locating
landings:
Locate landings in natural, level openings on firm dry
ground whenever possible. In moderate terrain this is easily
attained; in steep country, careful designation of landing
sites is necessary to minimize watershed damage. Often you
can make landings by widening the haul roads at some distance
from water courses. Cribbing built with cull or unmerchantable
logs and chunks on the downhill side will support a landing fill
and thus minimize excavation.
Certain models or procedures have been developed for locating timber
management facilities. Most of these "models" are based on economic
feasibility, but could have programs for minimizing water quality degra-
dation incorporated.
Such models concern facilities establishment (Gibson and Rodenberg
1974); helicopter refueling (Gibson 1974); helicopter landings (Egging
and Gibson 1974); running skyline design (Parson, Studier and Lysons
1971); activity scheduling (Carson and Burke 1972); mobile crane
yarding (Burke 1972); and access road alternatives (Burke 1974).
Since compacted soil areas are most often the critical sources of
erosion after logging, judicious location and design of skidroads and
trails is essential in order to decrease erosion potential. Dunford
and Weitzman (1955) suggest the following as general guidelines:
1. Do not yard logs along stream channels. Locate landings
so that logs are dragged away from streams rather than
through or across them.
2. Keep skidtrails well drained by diverting tl water into
areas where the sediment can filter out. It - especially
important that water bars and diversion ditches be installed
after logging. Frequent inspection is needed in rainy
periods to assure that the drainage checks are controlling
surface flow.
218
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3. Do not use tractors on steep slopes or wet ground. Tractor
operations should be limited to less rugged terrain and to
the dry seasons of the year. As a rough guide, 30 percent
slopes are considered a desirable maximum for tractor oper-
ation on many types of soil. Soils are considered too wet
when they contain water that can be squeezed out by hand.
4. Adapt logging equipment to logging conditions. On many
Forest Service timber sales, high lead cable logging is
specified on steep slopes.
Treatment of bare and compacted soil areas is essential. Since the
greatest deterrent to erosion is cover, the manager's first job after
disturbance should be to reestablish, as quickly as possible, a protective
covering of vegetation and litter. In areas of compaction or exposed
subsoil, natural revegetation may occur so slowly that seeding, ferti-
lizing and mulching are necessary.
After logging has been completed certain management activities are
usually required to complete the project and minimize long-term site
disturbance. These include residue management, site preparation,
regeneration, and stabilization (e.g., putting some of the roads and
landings "to bed"). These have been discussed adequately in Chapters 3
and 4, and in a previous report (EPA 1975), and very little will be added
here. An important overall consideration is the initiation and completion
of these operations as soon as possible after logging, to minimize the
period of high impact.
One important option involves the use of burning for residue disposal
and site preparation. The Western Forestry and Conservation Association
(1972) included the following, concerning prescribed burning, as to
information needed on this subject:
219
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1. Predictive models to enable the manager to select a burning
schedule for a given set of conditions, topography, and
other relevant factors, that will result in the minimum
environmental impact.
2. A knowledge of the conditions under which natural accumu-
lations of fuel occur, the rate of accumulation, and how
the organic material can be reduced without burning.
3. Decision models that will assist the manager in evaluating
the consequences of his selection from alternatives open
to him, including the calculation of the probabilities of
fire escape as part of the models.
<4. More intensive studies to determine the effects of fire
on forest ecosystems over time, and the effects of non-
burning as well.
The USDA Forest Service (1975) has recently published guidelines for forest
residue management for the Pacific Northwest which have applicability to
water quality.
Mechanical methods of site preparation during the last ten years
have included: scarification, stripping, and terracing (Packer 1971a).
These have been discussed in Chapters 3 and <4.
One notable accelerated reforestation program is being practiced by the
Weyerhaeuser Company. While seeding and other regeneration methods are used,
the program also involves soil surveys, winter planting, a system of seed
selection from similar sites and planning coordination between harvesting,
nursery planting and reforestation. Most importantly, containerized seedlings
are used on certain sites. Reforestation is generally accomplished within
one year.
Log landings are an important source of sediment and require post-
operation stabilization. The following procedures may be used;
220
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Landing fill, like road fill, is an accumulation of unstable,
loose soil highly susceptible to erosion. Cribbing, using cull
logs or seeding and mulching can impart a degree of stability to
the fill (.California Water Resources Board).
Upon abandonment, 'erosion-proof all landings by adequately
ditching or mulching with forest litter, as needed. Establish an
herbaceous cover on those areas that will be used again in
repeated cutting cycles and restock to coniferous species those
landings, located in clearcut areas, that will not be reused for
a long time, if ever (FWPCA 1970).
Oregon State Forest Practices Rules state: "Leave or place debris
and reestablish drainage on landings after use to guard against future
soil movement."
221
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NOTE
In addition to the following reference bibliography an annotated
bibliography has been prepared. It is available upon request to U.S.
Environmental Protection Agency, Region X, 1200 Sixth Avenue, Nonpoint
Source Section, Seattle, Washington 98101.
The annotated bibliography is 103 pages long and contains a capsule
write-up of many pertinent references. The coverage listed alphabetically
by author usually ranges from one or two paragraphs to a full page. It
is printed on standard white 8 1/2" x 11" paper.
222
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REFERENCE BIBLIOGRAPHY
-------
REFERENCE BIBLIOGRAPHY
Adams, Ronald S., 1969.
Ponderosa pine regeneration problems in the west coast
states. In Regeneration of Ponderosa Pine. R.K. Hermann
(ed.)5 Proc. Symposium held Sept. 11-12,1969- pp.12-18.
Alaska, state of, Department of Environmental Conservation,
Water Control Section, 1971.
Inventory of water dependent log handling and storage
facilities in Alaska.
Alexander, Robert R., 1972.
Partial cutting practices for old-growth lodgepole
pine. Res. Paper RM-92. Rocky Mountain Forest &
Range Exper. Sta. USDA.
Allen, E.J. I960.
Water supply watershed problems-Seattle Watershed. In
E.F. Eldridge (ed.), Proc. 7th Symposium water pollution
research. U.S. Public Health Serv., Reg. IX, Portland,
Oregon, pp. 15-17-
Allen, J.R.L., 1970.
The avalanching of granular solid on dune and similar
slopes. J. of Geology 78(3):326-351-
Anderson, D.A., 1969.
Guidelines for computing quantified soil erosion hazard
on on-site soil erosion. USDA Forest Service SW.
Anderson, Harold E., and George A. James, 1957.
Watershed management and research on salmon streams of
SE Alaska. J. Forestry 55(l):l4-17.
Anderson, H.W., 1951-
Physical characteristics of soil related to erosion.
J. Soil and Water Conserv. 6:129-133-
, 1954. .
Suspended sediment discharge as related to streamflow,
topography, soil, and land use. Transactions American
Geophysical Union 35(2):268-28l.
, 1957-
Relating sediment yield to watershed variables. Trans-
actions American Geophysical Union 38(6) :921-924.
, and Robert L. Hobba, 1959-
Forests and floods in the northwestern United States.
In symp. Hannoversch-Munden.
223
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and C. H. Gleason, 1960.
Effects of logging and brush removal on snow water run-
off. Extract of IASH Commission of Surface Waters.
Pub. No. 51, pp. 478-489.
, 1962.
Current research on sedimentation and erosion in Cali-
fornia wildlands. Rep. Pnbl., Assoc. Int. Hydrol. Sci.,
Gentbrugge 59:173-182.
, and J. R. Wallis, 1963
Some interpretations of sediment sources and causes,
Pacific Coast Basins in Oregon and California. Iri
Proc. Fed. Inter-Agency Sedimentation Conf., USDA Misc.
Pub. 970, pp. 22-30.
^,1970.
Principal component analysis of watershed variables af-
fecting suspended sediment discharge after a major flood,
Int. Assoc. Sci. Hydrol. Publ. 96:404-416.
, 1971.
Relative contributions of sediment from source areas
and transport processes. In James Morris (ed.), Proc.
of a Symposium--Forest land~~uses and stream environ-
ment. Oregon State University, Corvallis, pp. 55-63.
, 1972.
Major floods, poor land use delay return of sedimenta-
tion to normal rates. USDA Forest Serv. Res. Note
PSW-268, 4 p.
, 1974.
Sediment deposition in reservoirs associated with rural
roads, forest fires, and catchment attributes. Proc.
Int. Symposium on effects of man on erosion and sedi-
mentation. Int. Assoc. Hydrol. Sci., pp. 87-95.
Andre, J. E., and H.W. Anderson, 1961.
Variation of soil erodibiltiy with geology, geographic
zone, elevation, and vegetation type in northern Cali-
fornia wildlands. J. Geophys. Res. 66:3351-3358.
Archie, Steve, and David M. Baumgartner, (n.d.).
Clearcutting in the Douglas fir region of the Pacific
Northwest. Washington Woodland Council, 17 p.
224
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Arend, J.L. et al, 1954.
Tests at a portable wood chipper in utilizing logging
residue and in disposing of brush. USDA Forest Serv.,
Lake States Forest Exper. Sta., Pap. #30.
Atkinson, Sheridan William, 1971-
BOD and toxicity of log leachates. M.S. Thesis, Oregon
State University, Corvallis, 96 p.
Aubertin, G.M., and J. H. Patric, 1972.
Quality water from clearcut land. N. Logger 20(8):
14-15, 22-23.
Aulerich, D. Edward, K. Norman Johnson, and Henry Froehlich, 1974
Tractors or skylines: What's best for thinning young-
growth Douglas-fir? Forest Industries 101(11):42-45.
Axelton, Elvera A., 1974.
Pondersoa pine bibliography II, 1966-1970. USFS Gen.
Tech Report INT-12, 63 p.
Barr, D.J., and D.N. Swanston, 1970.
Measurement of creep in a shallow slide prone till soil.
Amer. J. Sci. 269, pp. 467-480.
Barrett, James W., 1968.
Response of ponderosa pine pole stands to thinning.
Res. Note PNW-77. Pacific NW Forest and Range Exper.
Sta. USDA.
, 1969.
Crop-tree thinning of ponderosa pine in the Pacific
Northwest. Res. Note PNW-100. Pacific NW Forest and
Range Exper. Sta. USDA.
Belknap, Raymond K., and John G. Furtado, 1967.
Three approaches to environmental resource analysis.
Landscape Architecture Research Office, Graduate School
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