GUIDELINES FOR REVIEW OF
ENVIRONMENTAL IMPACT STATEMENTS
VOLUME IV
CHANNELIZATION PROJECTS
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF FEDERAL ACTIVITIES
JULY 1976
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FINAL REPORT
GUIDELINES FOR REVIEW OF
ENVIRONMENTAL IMPACT STATEMENTS
VOLUME IV
CHANNELIZATION PROJECTS
Contract No. WA 76X-116
22 July 1976
Submitted to:
U.S. Environmental Protection Agency
Office of Federal Activities
4th and M Streets, S.W.
Washington, D.C. 20460
Attn: Mr. William Dickerson
Project Officer
Submitted by:
Curran Associates, Inc.
Engineers and Planners
182 Main Street
Northampton, Massachusetts 01060
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PREFACE
This volume presents detailed guidance for the assessment
of the primary impacts of channelization projects.
In its current form, this volume is intended to serve as a
supplement to the Environmental Protection Agency's 309 Review Manual
and existing assessment techniques related to water resources
projects. In toto, these documents provide the detailed framework
for the Environmental Protection Agency's review of channelization
project environmental impact statements.
As additional or refined review techniques and assessment pro-
cedures become available, this document will be reisssued or revised
as necessary. Note, however, that only the numbered copies are
on the distribution list for revised materials.
Comments and suggestions regarding this document should be
directed to the attention of the Director, Office of Federal Acti-
vities (A-104), Environmental Protection Agency, Washington, D.C.
20460.
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CONTENTS
Page
Preface ii
List of Illustrations iv
I. Introduction I- 1
II. Channelization Project Review II- 1
II.A. Pre-EIS Activity II- 1
II.B. Review of Draft EIS II- 2
II.B.I. Project Description II- 4
II.B.2. Relationships of Project to II- 5
Land Use Plans, Policies, and
Controls for the Affected Area
II.B.3. Probable Impact of Proposed 11-15
Project
II.B.4. Alternatives to the Proposed 11-24
Project
II.B.5. Probable Adverse Impacts that 11-25
Cannot be Avoided
II.B.6. Relationship of Short-Term 11-26
Uses to Long-Term Productivity
II.B.7. Irreversible and Irretrievable 11-27
Commitments of Resources to
Proposed Project
III. Project Rating III- 1
IV. Identification and Assessment of Project Impacts IV- 1
IV.A. Review of Hydrology and Water Quality IV- 1
Impacts
IV.A.I. Sources of Impacts IV- 1
IV.A.2. Review of Impact Quantification IV-11
IV.A.3. Assessment of Impacts IV-33
IV.B. Review of Aquatic Ecology Impacts IV-49
IV.B.I. Sources of Impacts IV-49
IV.B.2. Review of Impact Quantification IV-55
IV.B.3. Assessment of Impacts IV-65
IV.C. Review of Terrestrial Ecology Impacts IV-69
IV.C.I. Sources of Impacts IV-69
IV.C.2. Review of Impact Quantification IV-77
IV.C.3. Assessment of Impacts IV-83
111
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LIST OF ILLUSTRATIONS
Figure
1-1 Channelization Review Process
II-1 Separation of Impact Categories
IV-1 Hydraulic Effects of Channel Straightening
(Cutoff) and Related Environmental Considerations
IV-2 Hydraulic Effects of Channel Widening and Deepen-
ing, and Related Environmental Considerations
IV-3 Map of the United States Showing the Four Major
Major Groundwater Provinces
Table
II-l Channelization Review Checklist
II-2 Hydrology and Water Quality Impacts
II-3 Aquatic Ecology Impacts
II-4 Terrestrial Ecology Impacts
III-l Standards, Criteria and Regulations Related to
Channelization Projects
III-2 Rating Channelization Projects
IV-1 Conditions Favoring Low Potential Contributions
to Erosion and Sedimentation.Problems Within a
Channel Modification Area
IV-2 General Ranking of Soil Types With Respect to
Erosion Resistance and Compaction
IV-3 Suggested Water Velocities Not to be Exceeded in
Various Soil Types
IV-4 Comparative Sediment Yield From Bare and Seeded
Road Cut on the H.J. Andrews Experimental Forest
in Western Oregon
IV--5 Influence of Forest Cover on Control of Sediment
Yield by Erosion
IV-6 Average Range of Water Quality Criteria Adopted
by States for Selected Constituents and General-
ized Water Use Categories
IV-7 Mitigative Measures and Probable Effects
IV-8 General Tolerance of Representative Benthic
Macroinvertebrates to Pollution
IV-9 Overview of Channel-related Land Uses and Potential
Impacts on Terrestrial and Aquatic Systems
Page
1-3
11-19
IV- 3
IV- 5
IV-31
II- 6
11-21
11-22
11-23
III- 2
III- 4
IV-16
IV-2 2
IV-2 3
IV-2 5
IV-2 5
IV-3 6
IV-39
IV-60
IV-71
IV
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I. INTRODUCTION
The development of water resources continues at a high level
in response to the need for flood control, drainage, irrigation,
navigation, and other purposes. Federal and federally assisted
channel modification projects to meet these needs have, since the
early 1940's, involved the planning for and development of 34,240
miles of waterways.1 Many of the projects have not yet been con-
structed and are presently in various stages of planning, design,
and implementation. Concurrently, pressures for conservation and
preservation have been increasing because of concerns for the
ecological, historical, aesthetic, and recreational values of our
natural resources. There is also a growing awareness that these
resources are rapidly being lost to development of all kinds.
Channelization projects often engender conflicts between develop-
ment and preservation interests, in that the commitments of freely
flowing streams, adjacent wetlands, and riparian areas to ecological
change may be long-lasting and in some cases irreversible.* From
an ecological standpoint, the worst thing that can happen to a 2
stream is impoundment, and the second worst thing is channelization.
The range of possible impacts is very broad. Total numbers,
weight, and average size of fish in channelized reaches of Missouri s
Blackwater River are known to have been drastically reduced in com-
parison with unchannelized portions of the stream. Seemingly
inconsequential shifts in benthic species composition that accompany
channel construction may ultimately have major repercussions through-
out higher trophic levels. Terrestrial ecosystems can be equally
vulnerable to damage, either directly or indirectly, from channel-
ization. Channelization in the Caw Caw Swamp in North Carolina vir-
tually eliminated the watershed's wetlands, and with them the
cypress trees, furbearers, waterfowl, and other swamp biota, be-
cause of rapid drainage afforded by the pipe and channel network.
Although dramatic ecological changes usually receive the greatest
attention, similar impacts of varying severity are likely to occur
as a result of all channelization projects. A complete assessment
of resource commitments in terms of natural stream, land, and altera-
tion of riverine ecology is thus essential for weighing the benefits
of channelization against the project's impacts.
Often the basic question of whether a given channelization
project should proceed at all sparks the most controversy and cannot
be adequately answered using traditional methods of analyzing bene-
fits and costs. Intangible costs, relating to the maintenance of
environmental values, take on greater significance as the supply
of the affected resources declines. Natural streams are being
altered and impacted not only by channelization projects but also
*The term "channelization projects" in this document includes most
stream modifications from the largest to the small watershed work
type, but does not focus in depth on creation of completely new
Canals where no stream existed previously, as in areawide irrigation
projects.
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by impoundments, highways, bridges, development of flood plains,
introduction of wastewater effluents, and a host of other influences.
The weighing of impacts that involve long-term resource commitments
needs to be examined very carefully in the context of overall
environmental goals and objectives, with consideration given to
other land and water resource development activities expected to
occur during the planning period for a channelization project.
Planning must also be conducted relative to the fate of the project
after its useful economic or structural life ends. It is clear,
for example, that some channels constructed decades ago and since
abandoned still exhibit the effects of channelization in significant-
ly reduced populations of fish and other aquatic organisms. The
abandonment, dismantling, or continued maintenance of a channel
should be consistent with environmental safeguards used during pro-
ject construction and operation.
«
EPA's involvement in the channelization development process
steins from the mandates of the Federal Water Pollution Control
Act (FWPCA), as amended, the National Environmental Policy Act
(NEPA) of 1969 and the Clean Air Act Amendments of 1970.*
Under the FWPCA, EPA has authority and responsibility for
effecting national water quality goals specified by the law. In
particular, channelization projects may affect EPA authority under
Sections 208, 303, 313, 402, and 404 of the FWPCA. The relationship
o f channels to these sections of the FWPCA is addressed in more
detail below.
In view of the legal jurisdiction of, and special expertise
within EPA, Section 102(2) (C) of the NEPA obligates Federal agen-
cies to obtain comments from EPA wherever an action related to
air or water quality, noise abatement, solid waste management,
generally applicable environmental radiation criteria and stan-
dards, or other provisions of the authority of EPA are involved.
Section 309 of the Clean Air Act Amendments of 1970 gives EPA
the explicit legal mandate to comment in writing on the environ-
mental impact of any matter relating to EPA's duties and respon-
sibilities. To implement these responsibilities, the EPA manual
Review of Federal Actions Impacting the Environment3 (hereafter
referred to as the "309 Review Manual" has established detailed
policies, responsibilities, and administrative procedures for the
Agency's review of Federal actions impacting the environment. This
manual provides that, where an environmental impact statement (EIS)
*A listing of other relevant legislation, Executive Orders, and
Office of Management and Budget circulars and bulletins may be found
±n Basic Documents Concerning Federal Programs to Control Environ-
mental Pollution From Federal Government Activities, U.S. EPA, Office
of Federal Activities, February 1975.
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has been sent to EPA for comment, EPA's comments on the EIS
shall also constitute its comments for purposes of the Section 309
review. Furthermore, it is EPA policy to use the Section 309
process in conjunction with EPA's other authorities to: (a) pro-
vide technical assistance to Federal State, regional, and local
governmental entities; (b) assist the environmentally-related
activities of EPA and other Federal, State, regional, and local
entities; and (c) assist Federal agencies in meeting the objectives
of the National Environmental Policy Act.
Because the 309 Review Manual does not provide guidance for
applying the Section 309 review process to specific types of pro-
jects, the Office of Federal Activities, in conjunction with the
EPA program and regional offices, has prepared a series of
detailed review guidelines for several major project categories.
As one of the documents in that series, this guideline provides
detailed information for applying the EPA EIS review process to
channelization projects. Figure 1-1 illustrates the 309 review
process Chapters II and III of this guideline expand the manual s
guidance for implementing the EPA policy described above. Chapter
IV supplements the manual by providing a synthesis of the possible
hydrological, water quality, aquatic and terrestrial ecology,
and other impacts associated with channelization projects. Infor-
mation on the analysis and assessment of such impacts is also
presented. Finally, a detailed bibliography is provided to permit
the reviewer to explore specific problem^areas in .greater depth.
REVIEW GUIDELINE: VOLUME IV
JHAPTEJR |J
CHAPTER IV
II CHECK LIST
OWNNEUZATIONn AREAS***
REVIEW [ I
PROCESS
GUIDANCE
I I CHECK LIST
II OF IMPACTS
DETAIL EO
IDENTIFICATION
QUANTIFICATION
AND ASSESSMENT
OF IMPACTS
CHAPTER J'.L-
STANOARDS. CRITERIA
AND POLICY
PROJECT RATING
309 REVIEW MANUAL
REVIEW OF
FEDERAL ACTION
AFFECTING THE
ENVIRONMENT
Figure 1-1. Channelization Review Process
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REFERENCES CHAPTER I
1. Arthur D. Little, Inc. and Philadelphia Academy of Natural
Sciences, Report on Channel Modifications, Volume I, submitted to
the Council on Environmental Quality, U.S. Government Printing
Office, March 1973, p. 1.
2. Funk, J. L. and C. E. Ruhr, "Stream Channelization in the
Midwest," E. Schneberger and J. L. Funk, eds., Stream Channel-
ization; A Symposium, American Fisheries Society Special Publi-
cation No. 2, 1971.
3. U.S. Environmental Protection Agency, Review of Federal
Actions Impacting the Environment, Transmittal, March 1, 1975.
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XI. CHANNELIZATION PROJECT REVIEW
As described in the 309 Review Manual, the EPA EIS review
process consists of pre-EIS activities, review of Draft EIS's,
pre-final EIS liaison, review of Final EIS's, and post EIS follow-
up. Guidance for the review of channelization projects is given
in the following subsections in terms of these five review phases.
While it is recognized that unique situations within each region
may dictate emphasis on one phase over another, all phases of
the review process should be conducted to the fullest extent of
the region's resources. In any case, it should be kept in mind
that the goal of the review process is to maximize the effective-
ness of the EPA involvement in channelization projects. Generally,
this is accomplished when the EPA involvement: (1) reflects the
total environmental responsibilities of EPA, especially in those
cases where the basic nature of the EIS indicates a need for a
coordinated multi-program response; (2) is part of a continued
working relationship with the originating agency to.: assist in improvina
EKe7ir~p~roject~ planning and design processes; (3) focuses sharply
on environmentally unsatisfactory actions; (4) lends EPA support
to projects having beneficial impacts on the environment; and
(5) providing" federal agency officials background material for use
in~developing "ah EIS_;JT6]L review EIS prj£ .dra.ft program files .for
previous projects of a similar nature (noting any chanaes in EPA's
positions).
II.A. Pre-EIS Activity
"Pre-EIS activity" is a generic term which includes pre-EIS
coordination within EPA as well as coordination and information
exchanges with Federal, State, and local agencies responsible
for project planning or licensing. Pre-EIS activity within EPA
involves the coordination of EIS review with other BPA actions which
may affect the impoundment project, such as discharge permits
(NPDES), review of 404 permits, non-point source management
under Sections 208 and 303, Federal facilities pollution control
under Section 313, flow augmentation determinations under Section
102(b)(3), and sole-source aquifer determinations under Section
1424 Ce) of the Safe Drinking Water Act of 1974. Additionally,
EPA positions expressed previously on the project or project site,
as might be contained in reviews of earlier EIS's, Congressional
correspondence, or other agency statements, must be considered
in developing a consistent EPA position.
External pre-EIS activity includes a wide range of activities
outlined in the 309 Review Manual: .(1) review of an applicant's
environmental report or agency pre-draft EIS; (2) review of negative
declarations; (3) participation at agency meetings involving the
project; (4) substantive discussions with agency officials responsible
for a proposed action . Cwith emphasis on alternatives- and/or mitigation
measures'); C5T reyiew'of Jbasin plans (Level B studies); (6) site
Visits. In order to fully realize such opportunities for pre-EIS
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liaison it is important that EIS Coordinators maintain frequent
and regular contact with appropriate field agencies. EIS Coordina-
tors should understand planning processes and associated outputs
that might be useful in determining an early environmental assess-
ment of developing projects. Brief descriptions of the planning
processes of the Corps of Engineers, the Soil Conservation Ser-
vice, the Water Resources Council, the River Basin Commissions, and
the Fish and Wildlife Service may be found in the Appendix to
Volume III, Impoundment Projects, of the EIS Review Guidelines
Series.
Pre-EIS liaison with Federal agencies may also be formalized
through fl) a memorandum of understanding or (2) through protocols
developed by the Federal agency. A memorandum of understanding,
such as that developed with the Nuclear Regulatory Commission (NRC)
contains provisions for joint preparation of an EIS for projects
requiring an NRC license and a new source NPDES permit from EPA.
Under such an MOU, EPA bears responsibilities both as an EIS
preparer (as issuer of the new source permit) and EIS reviewer
(of the EIS on NRC's licensing action). In order to ensure an
even-handed and consistent EPA approach in discharging these duties,
the MOU establishes procedures requiring close coordination between
the agencies at the EIS preparation stage. This specialized
form of pre-EIS liaison is necessary in those circumstances in which
EPA is involved in granting a permit to a facility that is being
licensed by another Federal agency. MOU's analogous to that between
EPA. and_NRC_ will probably, be. d^Ye_lQp_ed_wlth .the_.a jiumber of other
agencies in the near future.
A more general type of arrangement is the pre-EIS protocol
established by the Soil Conservation Service. In the early stages
of planning, the SCS writes to EPA's regional offices to seek con-
sultation on matters within EPA's area of responsibility and special
expertise (see section 650.10(a) (6) of the SCS NEPA regulations).
It is the responsibility of the EIS coordinator to ensure that the
region is responsive to the SCS request for technical assistance
as the planning process is initiated.
Pre-EIS activity is extremely important in preventing poten-
tial environmental problems from being realized. It is at the
very early pre-EIS stages of project development that environmental
problems are most susceptible to EPA-recommended mitigation
measures. Similarly, the consideration of project alternatives
is most practical when done before any single alternative becomes
entrenched in the minds of project planners. The EIS review function
is one of the few Agency programs by which EPA practices prevention,
rather than abatement, of environmental problems. To secure the
greatest benefit from this program, effective pre-EIS liaison is
essential.
II.B. Review of Draft EIS
EPA's purpose in review of EIS's is to ensure that proposed
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Federal actions are carried forth in a manner consistent with the
attainment of national environmental goals and policies. The
Administrator has specific responsibilities under Section 309 of
the Clean Air Act to review proposed Federal actions and/ if he
determines any such action to be unsatisfactory from the stand-
point of public health, welfare, or environmental quality, to
publish his determination and refer the matter to the Council on
Environmental Quality.
In order to carry out these objectives, it is essential that
the EPA reviewer assess the impacts related to air, water, noise,
solid waste management, and other environmental areas within
EPA's jurisdiction. Review of the EIS should indicate whether that
document adequately identifies, quantifies, and evaluates the im-
pacts associated with the proposed project and various alternatives
tq_it,,
The effective assessment of the environmental impacts of a
proposed channelization project must begin with an understanding of
the project setting, as described by appropriate physical,
chemical, and biological parameters, and the changes in those
parameters that would be induced by the project. Beyond that point,
the effective assessment must describe the interdependencies and
cause-and-effect relationships among these parameter changes which
will bring into focus the environmental setting of the channelized
stream. The effective assessment allows the reader to compare
alternative environmental settings "with-and-without" the channel-
ization project, and other intermediate alternatives that will
effect project purposes with lesser amounts of environmental
damage than channelization.
The first task of EPA's EIS reviewer is to determine if the
EIS provides the effective assessment described in the paragraph
above. The reviewer should consider both the material presented
in the EIS and the material presented in reference documents.
According to the Council on Environmental Quality (CEQ) guidelines
for preparation of impact statements1, "Highly technical and
specialized analyses and data should be avoided in the body of the
draft impact statement. Such materials should be attached as
appendices or footnoted with adequate bibliographic references."
In what follows, then, the term "EIS" is used in the generic sense
of "EIS and referenced technical documents," provided that, first,
the EIS contains adequate summaries of the methodologies and results
of the various technical analyses, and, second, the detailed re-
ports describing these methodologies and results are available.
The reviewer should note that the foregoing does not preclude
the requirement that the EIS itself should contain sufficient "in-
formation, summary technical data, and maps and diagrams, where
relevant, adequate to permit an assessment of potential environ-
mental impact by commenting agencies and the public."1
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A systematic review procedure is necessary to insure that
all significant primary impacts have been considered and that the
assessments of the types of impacts can be combined into a single
assessment of the project. The CEQ Guidelines (1500.8) have defined
the major analysis categories to be included in an EIS:
(1) Project description;
(2) Relationship to land use plans/ policies, and controls
for the affected area;
(3) Probable impact of the project;
(4) Alternatives to the project;
(5) Probable adverse impacts which cannot be avoided;
(6) Relationship between local short-term use of man's
environment and the maintenance and enhancement of long-
term productivity;
(7) Irreversible or irretrievable commitments of resources;
{8) Other interests and consideration of Federal policy
affecting the project decision.
The following review guidance is structured along these lines.
II.B.I. Project Description
The reviewer should be able to place the proposed channelization
project in its appropriate environmental context. The amount of
detail should be, following CEQ guidelines, "commensurate with the
extent and expected impact of the action and with the amount of
information required at the particular level of decision-making
(planning, feasibility, design, etc.)." The reviewer should have
an accurate appreciation of the purpose of the project, the socio-
economic character of the area in which the project is to be con-
structed/ and the scope of other projects or activities (Federal
or non-Federal) which may be affected by the proposed action. CEQ
guidelines mandate a comprehensive portrayal of the area to be
affected by the project before the proposed action takes place.
Investigations of project background, site characteristics,
and discussions with interested parties may support descriptive
data included in the EIS and, in turn, may also suggest__to the re-
viewer additional sources of information that will foster'
a better understanding of the project.
The description of the channelization project's purpose should
be detailed enough to provide an explanation of the project's main
features, their separate and contributing functions, and the modi-
fications to the environment that these features entail. This des-
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crip-Live effort should help to define the geographical area
of Concern for the proposed action. The project's scope may
embrace several different kinds of environments (e.g., rural
and urban, forested and cultivated, recreational and commer-
cial, etc.) and it should be clear to the reviewer from the EIS
how and if the proposed action impinges on these diverse
areas. Furthermore, the spatial as well as the temporal nature of
environmental consequences of the proposed action should be clear
to the reviewer.
As an aid in checking the completeness of the EIS, a review
checklist for channelization projects is given in Table II-l.
Since no single checklist can be applied to all situations, the
reviewer is cautioned to utilize the technical review information
in Chapter IV to determine which, and to what extent, each of
the checklist items apply to the specific project under review.
II.B.2. Relationships of Project to Land Use Plans, Policies, and
Controls for the Affected Area
EPA's particular interest in reviewing a channelization project
under this criteria centers on the consistency of the project
with the requirements of the Federal Water Pollution Control Act,
in particular sections 208 and 303. Under guidelines recently
issued as 40 CFR Parts 130 and 131, States are to assume responsi-
bility for development and implementation of water quality manage-
ment plans to meet the goals of the FWPCA mandated by section 208
and 303:(1) the determination of effluent limitations needed to
meet applicable water quality standards, including the require-
ment to at least meet existing water quality (303); and (2) develop-
ment of State and areawide management programs to implement abate-
ment measures for all pollutant sources (208) .
All States have developed a river basin planning process con-
sistent with Section 303(e) of the Act. The basin planning program
has resulted in the development of plans setting out effluent limita-
tions needed by point sources to meet existing State water quality
standards (Phase I Water Quality Management Plans). Under 40 CFR
Parts 130 and 131, States must consider revisions to water quality
standards to meet the "fishable, swimmable" criteria of Section 101
(a) (2) of the Act. The revised plans (Phase II Water Quality
Management Plans) should consider all available means to meet water
quality standards including effluent limitations for point sources
and management of non-point sources.
Section 404 of the Act establishes a permit program for the
disposal of dredged or fill material into navigable waters. Guide-
lines (40 CFR Part 230) pursuant to this section of the Act specify
applicability of permit requirements in a like manner to all dis-
charges of dredged or fill material proposed by members of the general
public and Federal agencies including the .Corps of Engineers. The
'SPA's role in implementation of the Act includes (a) consultation
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Table II-l. Channelization Review Checklist
Review the Project Environmental Setting
Issue; What is there now? What are the baseline conditions?
Physical
- Topography
- Soils and geology
'Stability (slides and slump)
- Fluvial geomorphology (e.g. patterns of deposition and erosion,
character of the stream and its valley)
- Climate
- Flows, floods (highest and lowest, recurrence intervals)
- Erosion and sediment production, deposition
- Geohydrological
aquifer location and extent
recharge characteristics
- Water quality
existing uses
existing levels of water quality parameters
- Rainfall-runoff/snow - snow melt characteristics
- Estuaries
- Floddplains and wetlands
Cultural
- Land use
commercial, industrial, residential
forestry
mining
agricultural
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Table II-l (continued)
. recreational
aesthetic: wilderness, scenic, open space, parks, unique
physical features, historical and archaeological sites
Biological (flora and fauna)
- Aquatic
endangered species
unique ecosystems
-"- fish and shellfish, including migration routes and spawn-
ing areas
benthic organisms
insects
microfauna, microflora
aquatic plants
- Terrestrial
endangered species
unique ecosystems
range and habitat, migratory patterns, barriers, and
corridors
vegetation: trees, grasses, shrubs, crops
- Wetlands
relation to aquatic, terrestrial habitat
type and value
IT. Review the Project Characteristics
Issue: What is this project for? What will it do? What does
it look like?
Physical
- Construction techniques
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Table II-l (continued)
- Auxiliary systems: access roads, low-level weirs,
drop structures
Functions
- Single purpose
flood control
drainage
irrigation
diversion of water to control erosion and/or sedimentation
recreation enhancement
-- fish and wildlife protection
water supply
insect and pest control
- Multi-purpose
Economics
- Demand studies: bases for project need
- Supply studies: ways to meet identified needs
alternative projects
.. structural
.. nonstructural
- Project life
- Benefit/cost analysis
- Application of Water Resources Council Principles and
Standards
Operating and maintenance characteristics
- Schedule and characteristics of maintenance programs
- Design
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Table II-l (continued)
water level control structures
mitigation features (structural and nonstructural)
III. Review Environmental Impacts of Project
Issue; How will completion of this channelization project
(described in II above) affect the environment
(described in I above)?
- Review the predicted effects of the proposed channel on
the environmental characteristics of the river basin:
Physical, cultural, biological, (I above).
- In particular, review:
Projected changes in water quality parameters resulting
from channelization
.. in the channelized reach
.. in downstream reaches
Projected changes in uses (e.g. aquatic biota, water
supply, recreation) resulting from changes in water
quality parameters or destruction of habitat.
.. in the channelized reach
.. in downstream reaches
Projected changes in land use, such as a shift from low
intensity (agriculture) to high intensity (industry)
uses on the flood plain.
.. effect on wetlands, aquatic and terrestrial habitat
.. effect on water quality management planning
.. effect on air quality maintenance planning
- Review estimation and predictive modeling techniques for:
applicability to the scope of the proposed project
technical validity
predictive reliability
- Review alternatives
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Table II-l (continued)
design
.. channel location and dimensions
.. channel construction methods
.. channel lining, bank protection, gradient variation
.. operating policy
structural
.. upstream impoundment
nonstructural
.. no project
.. floodplain management
- Review mitigation measures
change in maintenance activities
design modifications
IV. Review Project Impacts for Consistency with Federal
Environmental Policy
Issue: Does the severity of the environmental impacts
(described in III above) of the project render it
inconsistent with the objectives, standards, or
implementing procedures of Federal environmental
policy?
- Review EPA legislative authority
Is project consistent with legislated environmental
objectives and policies?
Is project consistent with regulations implementing
environmental objectives and policies?
Will the project lead to standards violations?
- Review consistency of project with environmental planning
efforts
Is project consistent with State Water Quality Manage-
ment Plans?
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Table II-l (continued)
Is project consistent with Air Quality Maintenance Plans?
In particular, review consistency of project with environ-
mental requirements most likely to be affected by channeliza-
tion projects.
Water quality standards
.. flow requirements
.. water quality criteria
.. designated water quality uses
.. anti-degradation policy
Section 313 (Federal facilities pollution control)
Section 404 (Dredge and Fill). If disposal of dredged
or fill material is involved, review for compliance
with 404(b) Guidelines (40 CFR Part 230).
.. wetlands
.. municipal water supplies
.. fisheries and shellfish beds
.. wildlife
.. recreational areas
Administrator's Decision Statement on Wetlands
Review project under related Federal environmental require-
ments
Conformance with NEPA requirements and CEQ Guidelines
Conformance with Water Resources Council's Principles and
Standards (if applicable)
Conformance with:
.. Coastal Zone Management Act
.. Endangered Species Act
.. Fish and Wildlife Coordination Act
11-11
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Table II-l (continued)
.. National Historic Preservation Act
Review project in terms of mitigation measures (including
alternative projects and delayed construction) which could
reduce the adverse environmental effects of the project
Mitigation measures available to reduce adverse effects
should be fully utilized.
11-12
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with the District Engineer of the Corps of Engineers on interpre-
tation of the guidelines, (b) review and comment on permit applica-
tions, and (c) implementation of Section 404(c) in appropriate cases.
Section 404(c) authorizes the EPA to deny or restrict the use of any
defined disposal site upon determination that discharge of material
to the site would have an unacceptable adverse effect on municipal
water supplies, shellfish beds and fishery areas (including spawn-
ing and breeding areas), wildlife, or recreation areas. In cases
where channelization projects planned by Federal agencies necessi-
tate the disposal of dredged, excavated, or fill materials in
navigable waters or adjacent wetlands, such coordination, review,
and comment are necessary in conformance with 40 CFR Part 230.
Another piece of Federal legislation relevant to both land
use and water resource planning is Section 701 (Comprehensive
Planning Assistance Program) of the Housing Act of 1954 as amended,
administered by the Department of Housing and Urban Development
(HUD). The land use element of Section 701 establishes policies,
standards and studies of "where, when, and what kind" of growth
is compatible with urban programs. An Interagency Agreement
between the Department of Housing and Urban Development and the
Environmental Protection Agency (March 24, 1975) encourages
coordination between the land use provisions of Section 701 and
those of Section 208 of the FWPCAA. This agreement addresses not
only the need for consistency between the two agencies' planning
guidelines and procedures but also specific issues as, for example,
efficient design of treatment plants and the control of point and
nonpoint sources of pollution.
Major factors relating to water quality planning which should
be considered during the planning or EIS review of channelization
projects are as follows:
Waste Discharges. Stream channelization projects on waterways
into which wastewater is being discharged may affect assimilative
capacity of those waters, thus requiring the imposition of more
stringent effluent limitations or relocation of the wastewater
outfalls. Modification of existing outfalls, manholes, and sewers
may be required by channel or project construction.
Channels carrying highly saline irrigation return flows from
cultivated lands typify special examples of "nonindustrial" waste
discharge. The draining of swamps, ponds, and ditches which have
long served as receptacles for agricultural runoff and associated
sediments, fertilizers, pesticides, herbicides and other pollutants
in effect introduces new point sources of pollution into the basin's
waterways.
Alteration of Flow Regime. Because the formulation of a basin
plan will specify a stated or assumed range of flows for different
river reaches, the proposal to channelize a section of stream may
induce unanticipated or unscheduled changes in flow. Altered
flows may increase or decrease pollutant loadings at impoundments
11-13
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and natural storage areas. Because channels possess the ability
to reduce flooding alongside specified stream segments or to drain
headwater marshes, they may, perforce, have a profound effect upon
patterned intensities of land development in the basin.
2
EPA policies and procedures, however, specify that states develop
basin planning processes which "provide for the preparation of an
annual state strategy" as well as "guide decision-making over a
five to ten year span of time." Thus the insertion of a proposal
to construct a channelized section of stream should be reviewed in
the context of strategies adopted by a state's water pollution and
land use control plans and regulations.
Alteration of Preproject Water Quality. A channel project
may have an influence upon water quality both in the region through
which it passes and downstream from that area. Some of the
effects are traceable to: increased volumes of pollutants from up-
stream agricultural or silvicultural activities, increased turbidity
resulting from both short-term construction activities and long-
term channel-bank instability, reduced aeration potential along
channelized reaches of the stream course, reduced oxygen content
traceable to warmer water temperatures, reduced in-channel treat-
ment time resulting from substrate removal and more rapid flow-
through, reduction of pollutant filtering capacity by removal of
riparian and floodplain vegetation, and other factors.
Basin plan formulation, areawide wastewater management strate-
gies, and the discharge-permit system all focus on the identifi-
cation, evaluation, and control of sources of degraded water quality.
The influence of a proposed channel section on established water
quality standards, therefore, may be reason for revising plans for
the project's dimensions, restricting activities that introduce
pollutants to the watercourse, or introducing remedial measures to
restore water quality to preproject status. EIS review should
include an evaluation of those measures proposed in the channel
project's plans to mitigate or correct anticipated sources of de-
graded water quality.
Alteration of Water and Related Land Use. Stream channel con-
struction or modification may have important implications because
of possible direct or indirect effects on water use or related
land use. For example: drainage of swamps and marshes may increase
the development potential of areas in or adjacent to such lands;
such drainage may also diminish aesthetic values and biotic pro-
ductJ.vity; irrigation channels may result in changed allocation
schedules for waters in adjacent areas causing impacts upon exist-
ing land or water uses; or creation of channels to constrain flood
flows in one area may increase flood hazards in downstream areas.
Addilional examples may be drawn from those instances where the
focus is principally on the proposed benefits to recreation or
fish and wildlife propagation programs.
Both the regional context and the scheduling phases of a proposed
11-14
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channel project may embrace ramifying effects extending outside
the project area or scope which must be addressed in an EIS. A
marsh or a fishery resource, for example, may have values associated
with migratory bird flyways or anadromous fisheries, which are
especially important during specific seasons. Or the marsh may
produce food for upstream or downstream fisheries. These resources
have productive utility in and of themselves, and they also
have significance as attractors of consumers, both people and wild-
life, residing outside of a watershed area. Moreover, channel con-
struction may serve as either a stimulant or depressant to regional
development and growth patterns thereby influencing planning fac-
tors for wastewater treatment and other service facilities. Such
influences are often project schedule-related and need to be con-
sidered in an appropriate temporal context by local, state, and
regional (e.g. Water Resources Council "level B" studies) water
resource planning agencies and by the EPA in both planning and
review phases of a project.
In summary, an important part of both the EIS and its subse-
quent review is the assessment and evaluation of the complex changes
in existing and/or proposed programs, plans and policies for land
or water use which are directly caused, or induced, by channel-
building.
II.B.3. Probable Impact of Proposed Project
Review of the probable impact of the proposed project should
include the determinations that all potentially significant impacts
have been identified, that they have been adequately quantified
(within the limits of state-of-the-art techniques and commensurate
with the expected severity of the impact), and that the impacts
have been measured against applicable standards, criteria, and
regulations.
So that impacts stemming from channelization may be viewed
from the differing perspectives of persons reviewing projects with
different purposes in a variety of settings, a brief overview of
channelization projects and potential environmental impacts is
presented in the sections which follow.
Project Purposes. A comprehensive study of stream channeliza-
tion in the United States was recently (1973) completed by Arthur
D. Little, Inc. and the Philadelphia Academy of Natural Sciences
for the Council on Environmental Quality. That study reported that
nearly 200,000 miles of the more than 3 1/2 million miles
almost 6 percent of the nation's waterways have been modified
since the land was first colonized and that nearly 130 million acres
(200,000 square miles) of wetlands have been drained. But the
study also points out that most of this channel work was completed
in response to locally perceived problems and was independent of
the regional and national framework planning programs which now
precede most channelization projects. The report states that:
11-15
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It was not until a tardy recognition of federal responsi-
bility and federal capacity to transcend localized prob-
lems and consider water on a hydrologically interdepen-
dent and unified basis that solutions to the persistent
problems of poor drainage and flood damage prevention
really began to be solved.3
Impacts traceable to stream modification are not solely due
to purposeful channelization. Highway relocations, stream and river
crossings, upstream impoundments, and even such natural events as
floods have all caused modification of streamflows, channel morphe-
me try and alignment not dissimilar from that caused by channeliza-
tion projects.
Stream channelization projects as herein considered are those
involving deliberate modification of existing natural channels,
rather than the building of completely new channels where none
had before existed as, for example, in areawide irrigation pro-
jects. And the major navigational improvements on large rivers,
though admittedly involving channelization, also fall outside of
the scope of the EPA review process here being anticipated. Pur-
poses of those projects most often reviewed by EPA regional offices
include: flood control, drainage improvements, the provision of
recreational benefits, and the control of insect and other pest
populations.
Flood control and drainage projects, the most common under-
takings for which channels are proposed, vary considerably in
scope and complexity. They may be as simple as removing snags and
other obstructions along a stream course or as complex as straighten-
ing, enlarging, and lining the channel; they may involve a few
hundreds of yards of stream or river course or tens of miles.
Benefits often expected to ensue from these kinds of projects
include, in addition to those identified directly by the project's
principal purpose (e.g., flood control or improved drainage):
increases in land values and agricultural productivity, improvements
in the ability of a stream to hold water within its banks, increases
in streamflow capacities, stabilization of stream banks, provision
of outlets for land treatment measures (e.g., grassed waterways,
tile drains, and diversions), decreases in flooding and sediment
damages, and enhancement of recreational opportunities.
Characterization of Adverse Impacts. During the course of
two congressional hearings'*, held during the spring and summer
of 1971 on the subject of environmental impacts of stream
channelization, the following summary of "complaints" about
channelization were aired:
Artificial channels may cause:
..destruction of game and waterfowl habitat, and also trout
(i.e., coldwater) streams;
11-16
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..increases in upstream erosion and downstream flooding;
..pollution of downstream lakes and reservoirs;
..encouragement of farmers to drain wetlands and bring
unused wetland under cultivation;
..drainage of swamps, destroying their ability to act as "giant
kidneys" and remove silt, organic wastes and toxic chemicals
from the stream;
..acceleration of the release of water which might other-
wise percolate into and recharge groundwater reserves;
..encouragement of the development of flood plains, which
leads to further demands for flood protection works; and
..destruction of vast areas of wildlife habitat (in the southern
U.S.) which nullifies federal investments in wetland areas
(in the north of the United States).
Additional undesirable effects of stream channelization were
identified at the hearings by the National Audubon Society; they were:
..the lowering of water tables;
..elimination of flood plains which serve as recharge areas
for aquifers
..elimination of wildlife cover and soil-holding vegetation
along stream banks
..increases in water temperature and turbidity;
..elimination of desirable sport fishing
"in short, the conversion of beautiful streams that are rich in
natural life into sterile and unsightly ditches."S
Though the adversarial positions which characterize controver-
sies arising from stream channelization projects are of necessity
and purposefully either "black" or "white," such arguments have
the positive effect of sharpening the critical viewpoints and appraisals
of those concerned with such projects.
Natural streams are very complex systems when viewed in the
context of their ecology and interactions with terrestrial and wet-
land environments. A great abundance of different habitats is
formed by a myriad of current, light, and substrate conditions which
support a diverse array of flora and fauna. Naturally occurring pools,
riffles, and riparian vegetation in small streams provide many
niches or microhabitats, each of which has characteristics suitable
for specific biota but collectively affording food, shelter, and
iving space for numerous kinds of organisms. Meanders, oxbows,
11-17
-------
and other features of larger or mature streams cause considerable
variability in velocity and nature of the streambed which may not
be initially apparent to the casual observer. The interdependences
among all forms of life that make up a particular biological
community are incompletely understood. However, a basic lesson
of ecology that has been learned from all forms of human modifications
of natural systems is that introduction of artificial uniformity
is likely to invite ecological reactions, whether predictable
or unanticipated.
The environmental issues raised by channelization projects ulti-
mately involve the ecology and biota, even though they are often
addressed first in terms of physical, hydrological.and water quality
impacts. The EPA, then, in carrying out its functions to manage
and protect the environment, must focus on water quality, pesti-
cides, solid waste, and land use considerations as they relate to
biota, whether human, plant, or animal. In order to accomplish
the EIS review with this emphasis, the cause and effect relation-
ships among various channel-related activities and impacts should
be followed through. For instance, the fundamental alteration of
watershed hydrology due to channelization for flood control or
drainage will not only affect water quality response and aquatic
habitat but also change the development or use potential of adjacent
lands. In the eastern half of the country and particularly in the
Southeast this change has often been manifest in the drainage and
destruction of riparian and even upland marshes and swamps, the
decimation of bottomland hardwoods by drainage and groundwater
table lowering, large-scale clearing for agriculture, or both. Look-
ing again at the aquatic environment after these changes have
occurred, streamflows during dry periods are apt to have been
reduced and pollutants (sediments, pesticides, fertilizers, etc.)
introduced to the channelized watercourse with agricultural land
runoff. Then, both the hydrological and water quality conditions
resulting directly and indirectly from channel construction would
influence the aquatic biota. Certainly many other impinging factors,
including erosion and sedimentation, channel realignment,
proposed maintenance programs, and others, also have to be considered
in a similar fashion. It is important to maintain a broad ecological
perspective in assessing channelization or other water resource
projects and realize that damage _to__natura_l__strearns and their
biota always have the "potential for adversely affecting the human
environment and quality of life.
Impact Categories. A format for categorization of probable
impacts stemming from channel-building and subsequent stream modi-
fication has been adopted in Chapter IV and is shown below in Figure
II-l. In that chapter the techniques for impact identification,
quantification, and assessment are discussed in sufficient detail
to alert the reviewer to the nature and the interrelatedness of
potential impacts.
11-18
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Hydrology and Water Quality
Impacts (Section IV.A)
Terrestrial Ecology ^ ^ Aquatic Ecology
Impacts (Section IV.C) Impacts (Section IV.B)
Figure II-l. Separation of Impact Categories
As is true for all EIS's a separation of impact categories
should not be construed as anything more than an organizational aid
in the approach to impact evaluation and review. Impacts which
might be identified as primarily those affecting aquatic ecology
(for example, the removal of a stream's substrate and its resident
benthic organisms resulting in changes in both the morphometry of
the stream and such physical-chemical parameters as dissolved
oxygen (DO) content/ reaeration potential and stream temperatures)
will also have an impact upon the stream's hydrological character
and its water quality. Similarly, impacts considered as those princi-
pally affecting water quality (e.g., an increase in water tempera-
ture and decrease in DO resulting from removal of shade-producing
vegetation) will also have related impacts on terrestrial and aquatic
ecosystems. Therefore the interrelatedness, iterative nature, and
potential for magnification of impacts must be explicitly apparent
in the EIS and comprehensively evaluated in the review process.
It follows from the discussion above that an evaluation of
not only "primary" but significant "secondary" impacts should be
part of an EIS and therefore subject to EPA review. Though channel-
ization projects are, in essence, water resource management projects
there may also be related and significant impacts on air quality,
noise standards, pesticide dissemination/ and solid waste genera-
tion all areas falling within the scope of EPA's review responsi-
bility.
Identification, Quantification and Assessment of Impacts. Cate-
gorization of natural systems or impacts upon them, as earlier im-
plied, is an over-simplification of complex interdependencies for
which hierarchical orders, degrees of relatedness, and even cause-
and-effect relationships are sometimes only vaguely perceived.
The approach taken in Chapter IV aims to assist the reviewer in
grasping the more important and identifiable relationships among
hydrologic, water quality, and ecological impacts. The cross-
references found throughout those sections should be used whenever
further and related discussion in another part of the chapter might
be helpful.
In a sequential and engineering sense the impacts stemming from
11-19
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channelization may ordinarily be viewed as beginning with purpose-
ful changes in the hydrologic regime of a stream. The altered flow
patterns of a stream may, for example, induce such water quality
effects as a reduction in reaeration potential or increased erosion
and turbidity, or in an estuary saltwater incursion. Water
quality impacts, rather than hydrologic impacts, may appear from
some perspectives in the project area to be the initial impact
as when, for example, unperceived increases in a stream's velocity
shorten in-stream treatment time and result in obviously degraded
water quality at specific observation points downstream from a
channelized reach of stream. Because of the number of perspectives
from which impacts are viewed within a project area, as well as
the differing and subjective values of those assessing impacts,
the distinction between hydrologic and water quality impacts is
not always easy to make. Hydrologic effects, even though they can
sometimes be quickly identified and often quantified, nonetheless
have little significance in channelization impact assessments un-
less and until they have a measurable impact upon the water
quality and the ecosystems in, or related to, the modified stream.
Notwithstanding the fact that project purposes usually and
implicitly require or involve a change in the hydrologic regime
of a stream, the reviewer should recognize the iterative nature of
all impacts. A change in stream velocity, for example, may result
in stream bank undercutting and destroying bank-side vegetation
which, in turn, will result in increased water temperatures, and
a degraded fish habitat. These results will, in turn, further
influence the flow regime and water quality. But, in the example
given, stream impacts traceable to and initiated by the undercutting
of bankside vegetation is, for purposes of these guidelines, a
separable category of impacts and is assigned to "terrestrial ecology
impacts."
Tables II-2, II-3, and II-4 which follow illustrate both the
separability and relatedness of impacts which may result from
channelization. Each of the impact categories is analyzed indi-
vidually in the tables.
The reviewer should be aware that the tables do not contain
all of the impacts attributable to channelization, nor all of the im-
pacts specified in the tables pertinent to each of the projects
which will be reviewed. The tables should be used by the reviewer
as a guide to Chapter IV to gain insight into the kinds of acti-
vities and resulting impacts which should be evaluated in a repre-
sentatively comprehensive EIS. In addition, they should aid in
locating descriptions of particular impacts and technical references
that may be useful in completing the assessment.
Aside from those obvious impacts measurable in such terms as
loss of stretches of free-flowing stream and areas of natural
streamside vegetation, there are subtly incremental and cumulative
impacts which are, in many cases, time dependent. The alteration
of downstream water quality, or the accumulation of silt, sand,
gravel or boulders in downstream localities, are examples of those
11-20
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Table II-2. Hydrology and Water Quality Impacts
REVIEW OF
HYDKOLOGY
WATi;R
QUALITY
IMPACTS
Changes in Hydraulic
Parameters
IMPACTS ATTRIBUTABLE TO;
Changes in Watershed
Land Use
Construction and Main-
tenance
Sources of
Impacts
(Section
IV.A.I)
IV-2 to IV-5
-Channel straightening
-Levees and channel
confinement
-Alteration of channel
cross-section
-Clearing and snagging
-Channel lining and
protection
-Related water re-
source development
IV-6
-Changes in land cover
and effects on
hydrology
-Runoff- and land use-
related pollution
-Effects on downstream
flood hazards
IV-10 to IV-11
-Potential effects on
groundwater quality
IV-6 to IV-7
-Equipment types and
construction methods
-Sediment-generating
activities
-Other pollutants and
sources
IV-8 to IV-10
-Alteration of ground-
water discharge/
recharge
-Conditions favoring
minimal effects on
groundwater
-Influent versus eff-
luent conditions
-Effects of land
drainage
Revic-w of
Quantifi-
cat.i on
(Section
IV.7\.2)
IV-11 to IV-17
-General data require-
ments for impact
quantafication
-Approaches to estima-
tion of downstream
hydrologic effects
-Hydrologic effects on
waste assimilation
-Evaluation of channel
erosion and sedimen-
tation potential
-Influence of sub-
strate on purifica-
tion capacity
IV-19 to IV-21
-Evaluation of runoff/
water quality/land
use interactions
IV-18 to IV-19
-Evaluation of ther-
mal regime changes
from bank clearing
IV-21 to IV-25
-Relevance of project
scale, soils, topo-
graphy, climate, &
vegetative cover
variables
IV-26 to IV-30
-Evaluation of pollu-
tion from major con-
struction activities
IV-30 to IV-33
-Methods and consider-
ations for ground-
water impact quanti-
fication
Assessment
of
Impacts
(Section
IV.A. 3)
IV-37 to IV-40
-Assessment of assimi-
lative capacity
changes and down-
stream effects
-Measures to mitigate
adverse hydraulic
and water quality
impacts: discussion
and table
IV-34 to IV-37
-Basis for assessment:
water quality cri-
teria and standards
IV-40 to IV-41
-Assessment of land
use impacts related
to channelization
-Assessment of poten-
tial pollution from
land use activities
I
IV-41 to IV-48
-Purposes of assess-
ing construction
and maintenance
impacts
-Reduction of erosion
and sedimentation
-Nature and schedules
for maintenance
-Disposal of exca-
vated material
-Protection of
groundwater
-------
Table II-3. Aquatic Ecology Impacts
REVIEW OF
1UATIC
JOLOGY
IMPACTS
Habitat Alteration by
Riparian Vegetation
Removal
IMPACTS ATTRIBUTABLE TO;
Habitat Alteration by
Channel Excavation and
Maintenance
Habitat Alteration by
Changes in Land Use &
Water Quality
Sources of
Impacts
(Sect Lon
IV.B.I)
IV-50 to IV-51
-Effects of instream
debris removal
-Effects of riparian
vegetation removal
on temperature,
erosion potential,
and habitat diver-
sity
IV-49
-Basic ecological prin-
ciples underlying im-
pact identification
IV-51 to IV-54
-Turbidity and sedimen-
tation impacts
-Reduction of available
aquatic habitat
-Relationship of velo-
city to habitat
diversity
-Effects of groundwater
changes and drainage
on aquatic ecology
-Ecological effects of
channel maintenance
IV-54 to IV-55
Land use changes due
to flood protection
or drainage functions
Changes in nutrient,
sediment, pesticide,
and other pollutant
loads; ecological
implications
Review of
Impact:
Quantafi-
cation
(Section
IV.B.2)
IV-56 to IV-57
-Basic data require-
ments for character-
izing aquatic
habitat
-Ecological effects of
altered temperature
patterns (see also
Section IV.A.2)
IV-57 to IV-62
-Quantification of hab-
itat gains and losses
-Relevance and need for
fisheries, benthic in-
vertebrate, and aqua-
tic plant data
-Approaches to evalua-
tion of suspended
solids and sedimenta-
tion impacts
-Tolerance of benthic
organisms to pollu-
tion (Table IV-9)
-Consideration of im-
pacts on fish spawn-
ing and anadromous
species migration
IV-62 to IV-64
IV-64 to IV-65
Baseline data require-
ments for impact
prediction (water
quality, land use,
etc.)
Uncertainties in
impact quantification
-Possible shifts of
species abundance
-Approaches to evalua-
tion of ecological
impacts of hydrologic
modifications and
creation of back-
waters (due to chan-
nel realignment)
Assessment
of
Impacts
(Section
IV.B. 3)
IV-65 to IV-68
-Applicability of critena"to eco'iogi'cal "impact assessment
-Judgment of adequacy of EIS with respect to ecological
impact evaluation
-Assessment of thermal regime changes
-Assessment of suspended solids and sedimentation impacts
-Assessment of habitat changes for which no explicit
criteria exist
-Applicability of mitigation measures
11-22
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Table II-4. Terrestrial Ecology Impacts
REVIEW OF
"ERRESTRIAL
:OLOGY
Riparian Habitat and
Land Use
IMPACTS ON;
Wetland Habitat and
Land Use
Upland Habitat and
Land Use
Sources of
Impacts
(SecLion
IV.C.I)
IV-70 to IV-72
Streambank clearing;
terrestrial and
aquatic ecology
considerations
Effects of groundwater
changes
-Effects of major con-
struction activity
on terrestrial
ecosystem
-Possible indirect
effects on riparian
habitat and land use
IV-72 to IV-75
-Wetland drainage and
alteration of inun-
dation patterns
-Impacts on bottom-
land hardwoods
-Impacts of spoil
disposal
-Impacts of drainage
facilities tribu-
tary to main
channel
IV-75 to IV-77
-Impacts of ancillary
structures and land
treatment (upstream
impoundments, crop-
ping practices, etc.)
-Regional considera-
tions beyond project
area
Review of
Impac t
Quantifi-
cation
(Seel ion
IV.C.2)
IMPACTS DEPENDENT ON:
Project Dimensions
IV-77 to IV-80
-Basic data requirements for im-
pact estimation (project
dimensions, environmental
settings, land use inventory
etc.)
-Approaches to classifying
wetlands
-Approaches to evaluating impor-
tance of wetlands
-Evaluation of impacts on urban
and recreational lands;
aesthetic considerations
Land Use and Ecological Value
IV-80 to IV-83
-Adequacy of time frame for evalu-
ating land use changes and impacts
-Categorization of land uses
-Economic, social and ecological
criteria relevant to land use
and terrestrial habitat
Assessment
of
Impacts
(Sect ton
IV.C. 3)
IV-83 to IV-86
-General approach for terrestrial impact assessment
-Assessment of wetland and riparian impacts and interrelation-
ship with aquatic ecological effects
-Regenerative potential of impacted areas; rare and
endangered species
-Assessment of land use impacts
-Applicability and assessment of mitigative measures and
alternatives
TT
-------
impacts which are often cumulative in nature. On the other hand,
impacts stemming from such temporary activities as construction
or periodic maintenance! are only episodic and may therefore be of
lesser significance.
But the reviewer should take note that though an identified
impact (e.g., diminished trout population due to reduction in
gravel riffles which are prime reproductive habitats) may be small,
in combination with other minor impacts (e.g. incorporation of
additional agricultural runoff and aesthetic degradation) the
combined effect may be of major significance.
Traditionally the modification of fish and wildlife resources,
vegetation, and other elements of an ecosystem has been equated with
losses, or gains, in hunting, fishing, and other recreational
activities. However, this sort of trade-off analysis in an EIS should
also include an accounting of those intangible values associated with
rivers and streams in their natural states. And among these values
there may be included areas of unique or special ecological or
geological value.
It should be recognized that adequate assessment techniques do
not exist for all impacts, even those which can be accurately
identified and quantified. For example, subtle changes in water
quality (e.g. in temperature, salinity, or other parameters) may
occur as the result of a channel project and thus violate the Statewide
ant [.degradation policy established in conformance with 40 CFR 130.10 (a)
(5) and 131.1,1 (e), even when numerical water quality criteria are not
Violated. Such changes may have environmental significance when viewed
along with the many other influences on basin water quality.
3,1.D.4. Alternatives to the Proposed Project
Where adverse environmental impacts will occur if the proposed
action is taken, it is important to review if and how the initiating
and responsible agency has explored and objectively evaluated the
environmental impacts of all reasonable alternative actions,
vparticularly those that might enhance environmental quality
or avoid" some or all of the adverse environmental effects" of
a project. Alternatives to the proposed action can be presumed to
exist in those situations where disagreements and conflicts over the
use of available resources remain unresolved.
The reviewer should review the alternatives included in the EIS
to assure that they are reasonably comprehensive and that the
evaluations of their environmental benefits, costs, and risks are
comparable with the conclusions on the proposed action. Alternatives
may be thought of either as project-related modifications or project
replacements.
One purpose of both the EIS and the ElS-review process is to
avoid premature rejection of any and all alternatives or options which
might result in an environmental impact significantly reduced from
that of the proposed action.
Alternatives to be reviewed should include:
TT-24
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..no action (i.e., foregoing the project), and
..rescheduling of proposed channel construction.
In addition the reviewer should consider the applicability of
the following types of alternatives to channelization:
..change in scope, design, or magnitude of the proposed
project;
..change in location of portions or all of the project;
..alternative nonstructural methods of accomplishing the
project's functions (Example: consideration of
nonstructural techniques for providing flood protection,
e.g., flood plain zoning, relocation of buildings,
floodproofing, etc.);
..alternative structural methods of (or project components
for) achieving the purposes (Example: consideration of
such techniques as: digging relief drains or wells
instead of constructing channels to solve drainage
problems; or building a separate flood flow channel instead
of channelizing a natural channel to contain floodwaters);
..compensatory or mitigating measures (Examples: consideration
of limiting construction activities to one side (i.e., not
both, sides) of a natural channel; or construction of bank
covers or wings to restore fish habitat.
All reasonable and feasible alternatives should be included in
the EIS and should be reviewed in sufficient detail to identify:
, .the degree of increase or decrease of impacts as
contrasted with those anticipated for the proposed actions;
.,the adequacy of impact assessments for proposed actions;
,.the adequacy of impact assessments for each alternative; and
..the effective mitigation of impacts by each alternative over
the proposed project's lifetime.
The reviewer's task will be to determine which of the alternatives
could be recommended as less environmentally damaging than the
proposed action but which substantially meet project purposes and
objectives. In some cases the alternative proposed by the originating
agency may have been judged the most acceptable for economic or other
reasons even if other courses of action offer a lesser threat to the
environment. However, EPA's assessment and recommendations should be
based primarily on the environmental merits and drawbacks of each option.
II.B.5. Probable Adverse Impacts that Cannot be Avoided
Where all mitigating measures have been taken, the probable
11-25
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adverse impacts that cannot be avoided will be the basis for the
overall assessment and rating of the project. Probable adverse
environmental impacts to be considered include: water and air
pollution, undesirable land use patterns, damage to fish and wildlife
habitat, threats to health, and all other consequences specified in
section 101 (b) of the National Environmental Policy Act.
The reviewer should appraise this section of the EIS as a
summary of those adverse impacts which are unavoidable results of the
proposed action (as earlier identified for review in Section II.B.3
of these guidelines). The reviewer should also find in this section,
as contrasting data, identification of the mitigating or compensating
measures proposed for reduction of the adverse impacts specified.
In essence the review process should insure that "the kinds of
adverse impacts which cannot be reduced in severity or which can be
reduced to an acceptable level, but not eliminated" are identified
in the EIS.
II.B.6. Relationship of Short-Term Uses to Long-Term Productivity
Reviewers should note the stipulation in CEQ guidelines which
states that "this section should contain a brief discussion of the
extent to which the proposed action involves tradeoffs between the
short-term environmental gains at the expense of long-term losses, or
vice versa, and a discussion of the extent to which the proposed action
forecloses future options." Of particular importance are those
projects which "narrow the range of future uses of land and water
resources or pose long-term risks to health or safety".
Channelization impact assessments should be reviewed to determine
relationships between such project resources (both natural and
cultural) and project elements as:
..intrinsic values of natural and free-flowing streams in the
project area, and those benefits estimated from enhancement
of agricultural productivity and/or flood protection of
developed areas, etc.;
..anticipated duration of short-term and long-term impacts-both
beneficial (e.g. to flood-prone and water-saturated areas) and
adverse (e.g. to water quality, noise standards, air quality,
etc.), and estimate of time for regeneration of the watershed's
renewable resources to preproject status:
..anticipated demand schedules for benefits from proposed and
induced actions compared with the anticipated life of the
project;
..justification for project implementation, as proposed, rather
than deferral of action in order to preserve future options;
11-26
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..consistency with federally funded projects in flood
hazard areas (i.e. review of Executive Order 11296).
II.B.7 Irreversible and Irretrievable Commitments of
Resources to Proposed Project
The intent of this section of the EIS is to identify
those unavoidable impacts induced by the projects and the
"extent to which they curtail" the potential uses of the
environment. And the term "resources" refers not only to
the labor, funds, and materials committed to a project but
also to the natural and cultural resources affected by the
proposed action.
The reviewer should note the adequacy and comprehensiveness
with which the EIS addresses such elements of the proposed
channelization as:
..induced growth which forecloses alternative uses of
land in the watershed;
..losses of irreplaceable historical and archeological
resources or populations of rare biological species;
..ecological, social, and aesthetic values associated
with those sections of a stream or its riparian
environment which will be lost as a result of channel
modification; and
..the impacts of conversion of those areas required for
project facilities (basins, outlets, levees, etc.) and
easements (flowage, right-of-way, etc.) from prior
open and/or productive uses.
11-27
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REFERENCES CHAPTER II
1. 40 CFR Part 1500 - Preparation of Environmental Impact
Statements - Guidelines.
2. 40 CFR Part 130.1.
3. Arthur D. Little, Inc. and Philadelphia Academy of
Natural Sciences, Report on Channel Modifications,
Volume I, submitted to the Council on Environmental
Quality, U.S. Government Printing Office, March
1973, p. 60-61.
4. U.S. Congress - (1) House of Representatives, Subcommittees
on Conservation and Natural Resources - Committee on
Government Operations - Hearings on Stream Channelization,
92nd Congress, 1st session (4 pts.J; C2J U.S. Senate
Subcommittee on Flood Control - Rivers & Harbors,
Committee on Public Works - Hearings on the Effect of
Channelization on the Environment, 92nd Congress,1st"
Session.
5. Senate Hearings, p. 214.
11-28
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III. PROJECT RATING
The basis for the EPA comments on the environmental impact
of channelization projects is quite broad. As stated in the
Clean Air Act, Section 309(a), EPA comments on "...any matter
relating to duties and responsibilities granted pursuant to this
Act or other provisions of the authority of the Administrator..."
The NEPA, section 102(2) (C) states "...the responsible Federal
official shall consult with and obtain the comments of any Fed-
eral agency which has jurisdiction by law or special expertise
with respect to the environmental impact involved."
The above mandates have been interpreted to mean that the
EPA comments should be related to the impact of projects on water
quality/ air quality, solid waste management, noise, radiation
control, and pesticide and other toxic substances use and control.
Water quality concerns include protection of beneficial water
uses, wetlands, aquatic life and habitat, and water-related wild-
life. Comments related to land use, terrestrial wildlife, aesthe-
tics, recreation, and other areas must be related to areas of ex-
pertise. It is proper to discuss agricultural or other land de-
velopment a channelization project may induce if it will aggra-
vate an already serious air or water pollution problem. It is
also proper to evaluate the potential for downstream development
in floodprone areas as a result of flood control functions of a
channel as well as the extent to which projects benefits assigned
to flood control include such projected development.
If an EPA reviewer has special insight on a project, such as
that resulting from an on-site inspection or discussion with com-
munity leaders, it is appropriate to make comments on matters
falling outside of EPA's specific areas of jurisdiction. The
EPA policy is that such comments are for information only and
are not used to justify the assigned EPA rating. Furthermore,
such comments must include a statement to the effect that final
determination on the matter is deferred to the Federal agency
w.Lth the appropriate jurisdiction.
The specific basis for the EPA assessment of environmental
impacts consists of the standards, criteria, EPA policy decisions,
and consistency requirements with other EPA program responsibili-
ties as shown in Table III-l.
As detailed in the 309 Review Manual, the EPA rating scheme
i& different for draft EIS's, final EIS's, and pre-Clean Air Act
Amendments EIS's. At the draft stage comments shall be desig-
nated by an environmental impact rating of LO (Lack of Objections),
ER (Environmental Reservations), or EU (Environmentally Unsatis-
factory) , Category 2 (Insufficient Information), or Category 3
(Inadequate). If a draft EIS is assigned a Category 3, normally
III-l
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Table III-l. Standards, Criteria and Regulations
Related to Channelization Projects
Standards
..Latest version of primary drinking water standards
prepared by EPA pursuant to the Safe Drinking Water Act
(PL 93-52'3)
..Water Quality: State adopted water quality standards
consisting of water quality criteria and plans for the
enforcement and implementation as referenced in 40 CFR
Part 120.
..Air Quality: National primary and secondary ambient air
quality standards as specified in 40 CFR Part 50
Criteria, Regulations and Policy
..Criteria for Water Quality/ Volume I (Proposed) U.S.EPA,
October 1973
..Water Quality Information, Volume II (Proposed), U.S.
EPA, October 1973
..Information on Levels of Environmental Noise Requisite to
Protect Public Health and Welfare with an Adequate Margin
of Safety, U.S. EPA, March 1974
..Regulation for the Disposal and Storage of Pesticides and
Pesticide Containers, 40 CFR Part 165
..EPA Policy to Protect the Nation's Wetlands, Administrator's
Decision No.4
..Navigable Water, Procedures and Guidelines for Disposal of
Dredged or Fill Material, 40 CFR Part 230
..Latest regulations prepared by EPA pursuant to Section 1424
(e) of the Safe Drinking Water Act regarding Federal
projects in a recharge area of an aquifer designated as
a sole source aquifer
..Amended FIFRA Act. The Federal Environment Pesticide Control
Act of 1972 (FEPCA)
..Thermal Processing and Land Disposal of Solid Waste Guidelines
40 CFR, Parts 240, 241
Consistency with Other EPA Programs
..Areawide Waste Treatment Management Planning Areas ("208"
Plans), 40 CFR Part 126
..Water Quality Management Basin Plans ("303(e)" plans),
40 CFR Part 131
..National Pollutant Discharge Elimination System,
40 CFR Part 125
..State Air Implementation Plans, 40 CFR, Parts 50 and 51
III-2
-------
no rating will be made on the environmental impact of the pro-
posed project or action since a basis does not generally exist
on which to make such a determination. When there is a basis
i:or assessing the environmental impact of a proposed action,
such as independent documents or on-site surveys, such a rating
may be established at the discretion of the principal reviewer
after consultation with OFA.
At the final stage, no alpha-numeric designations are made
since only the project impact is considered and not the complete-
ness of the EIS. The project impact rating assignments for the
final EIS consist of: Lack of Objection, Environmental Reser-
vations and Environmentally Unsatisfactory. A rating assignment
of Unresponsive Final Impact Statement can be made if the final
EIS has not responded adequately to comments made by EPA on the
draft EIS. Such comments may also be offered if new environmental
concerns have been brought to the EPA's attention since the re-
view of the draft EIS and the originating agency does not ade-
quately evaluate these factors in the final EIS. In the case of
projects which were authorized prior to passage of the Clean Air
Act Amendments (December 31, 1970), the determination of Environ-
mentally Unsatisfactory shall not be used. Instead, the final
EIS comment should present EPA's substantive comments on the pro-
ject, omitting both reference to Section 309 and use of the term
"Environmentally Unsatisfactory."
The general criteria for assigning the Environmental Reser-
vations, Environmentally Unsatisfactory, or Category 3 ratings
are given in Table III-2. The reviewer should note that these
criteria are intended to be used as guidelines rather than strict
rules. The decision regarding the impact of each project must
incorporate all the mitigating factors for that particular pro-
ject. The sensitivity of the environment to the changes imposed
by the channelization project, as well as the effectiveness of
mitigating measures, must be taken into account.
III-3
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Table III-2. Rating Channelization Projects
Category EU; Environment:ally iTnaafci
General Criteria
(from 309 Review Manual)
a. Where it is highly probable
that a violation of standards
will occur.
1. Federal, State, and local
standards are included;
includes EPA regulations and
and guidelines.
Projects which as "an initial
step do not violate standards
but inherently create signi-
ficant pollution problems
in related areas."
Specific Criteria
for Channelization
.Violations of water quality
standards, including
noncompliance by Federal
facilities with requirements
for pollution abatement and
control (section 313);
..violations of water quality
criteria for the uses
designated in standards;
..violations of flow require-
ments required by water
quality standards;
..violation of State anti-
degradation provision or
EPA's anti-degradation policy;
..violation of State mixing
zone policy.
.violation of informational
guidelines, such as those for
non-point source control (304
(e)).
.Unacceptability under FWPCA
Section 404, i.e. channelization
projects for which EPA has
denied a permit under 404(c)
for reasons relating to water
supply, shellfish beds and
fishery areas, wildlife, or
recreational areas.
.Projects which, with high
probability, will lead to
undesirable growth rates
adversely affecting the
attainment of air quality goals
in critical Air Quality mainte-
nance areas or water quality
goals established through State
Water Quality Management
Plans (Section 208,303).
III-4
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Table III-2. (continued)
b. Where a Federal agency violates
its own substantive environ-
mental requirements.
c. Where there is a violation of an
EPA policy declaration
.Projects which will not "stand
alone," i.e. those for which full
realization of benefits strong]£
implies further system develop-
ment which, taken as a whole,
would lead to standards violation
or "undesirable growth rates"
described above.
.As applicable
.Violation of EPA's Statement
of Policy on Protection of
Nation's Wetlands (38 FR 10834).
Where there are no applicable
standards or where applicable
standards will not be
violated but there is
potential for significant
and severe environmental
degradation:
1, which could be mitigated by
other feasible alternatives;
or
2. which related to EPS's area
of jurisdiction or expertise
.Where adverse environmental
effects are beyond EPA's
jurisdiction and expertise
(e.g. historic site, wild and
scenic rivers), but there exists
a feasible alternative (i.e. ono
that would substantially
accomplish project purposes)
which would significantly reduce
adverse environmental effects.
.Where severe adverse environments
effects are within EPA's
jurisdiction and expertise but no
standards violations are
expected, e.g. either no standard
exists for a particular water
quality parameter, or considerabl
uncertainty regarding project
environmental effects exists.
.Where aquatic biota, water
supply, or recreational areas
are threatened, but no 404 permit
is involved.
III-5
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Table III-2. (continued)
category 3: Inadequate
General Criteria
(from 309 Review Manual)
a. Insufficient information to
permit a reasonable review
of project features, thus
precluding evaluation of
project effects on EPA standards
regulations or policies.
ThH_EIS_ fails tg__adequately_ consider
important p_roject features which
EPA.believes, have, a"significant
impact on the envirojunent. (e.g.
(if .certain project components are
no.t_co_vered.in a broad based EIS
and .±he_.Agency^s_ intent is not ~to
prepare subsequent EIS's on these
componentsji_. _
Specific Criteria
for channelization
.Inadequate description of
water quality parameters
and their effects on uses
(e.g. aq.uatic biota, water
supply); either for the
channelized area or downstream
reaches.
.Inadequate description of
project operation, purposes,
benefits and costs, construction
techniques, resulting growth
patterns, and other features
necessary to allow comparison of
project effects with area Water
Quality Management Plans (and,
perhaps, Air Quality
Maintenance Plans).
Projects which may provide
comparisons with Water Quality
Management Plans, but are
inadequate for determining
local effects on water quality,
aquatic biota, or other areas
of EPA jurisdiction and
expertise.
-------
Table III-2. (continued)
Environmental Reservation?
General Criteria
(from 309 Review Manual)
a. Reservations exist concerning
the environmental effects of
certain aspects of the
proposed project.
Specific Criteria
for channelization
.Rare natural resources are
directly or indirectly destroyed
by operation or construction
of the project and these
resources are unprotected by
Federal or state regulations.
.Long-term effects of proposed,
actions are_estimated_by EPA to
be serious but" have riot been
adequately considered.
III-7
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IV. IDENTIFICATION AND ASSESSMENT OF PROJECT IMPACTS
The purpose of this chapter is to furnish more detailed
information and sources of information on the impacts of channeli-
zation projects. Impacts are discussed in three broad categories
(hydrology/water quality, aquatic ecology, and terrestrial ecology),
but the reviewer should recognize that substantial interdependence
exists among these groups. Under "Sources of Impacts," impact-
producing activities and situations in which particular effects
are likely to occur are described. "Review of Impact Quantifica-
tion," focuses on the methods that may be used to estimate the
magnitude of various impacts. The "Assessment of Impacts,"
sections address the relationship of impacts to pertinent environ-
mental standards, criteria, and regulations, and describe oppor-
tunities for mitigating project impacts. Tables II-2, II-3 and
I1-4 provide a detailed reference to discussions of impacts and
should be used freely in locating specific material in this
chapter.
IV.A. Review of Hydrology and Water Quality Impacts
Alteration of watershed hydrology is inherent in channeliza-
tion activity. The changes that take place may affect not only
water quality, but also aquatic and terrestrial ecosystems. Be-
cause of the strong interrelationships among impacts in these
various categories, the review guidance on hydrologic impact
sources and quantification provided in this section is also rele-
vant to discussion of aquatic and terrestrial ecology impacts
(IV.B. and IV.C.).
The construction phases of a channelization project give rise
to increased pollutant loadings, primarily from work directly
in the stream and from erosion of disturbed areas. Changes in
water quality response of the stream result from the modified
hydraulic characteristics of the channel following construction
as well as from alteration of land uses in the watershed, both
upstream and in the vicinity of the channelized segment. An
understanding of the intimate relationships between hydrology
and water quality characteristics in streams is essential to
identification and prediction of impacts. The following des-
criptions of these relationships should enable the reviewer to
ascertain, for a given channelization project, whether water
quality impacts have been properly treated, and to comment on
deficiencies in the EIS concerning evaluation of probable impacts
not considered. The guidance presented herein^-may be supplemented
by reference to the cited technical publications or through
appropriate program offices within EPA.
IV.A.I. Sources of Impacts
Although direct construction phase impacts associated with
channelization projects may persist for a relatively short time,
on the order of months or years, the basic changes in stream hy-
drology brought about by channelization will endure for far
IV-1
-------
longer periods. The water quality implications of channeliza-
tion stem directly from the resulting hydrologic modifications
and perhaps indirectly as well from overall changes in water-
shed land use and development. Therefore, adequate review and
assessment of environmental impacts demand that the two perspec-
tives, of time and geographical area that influences or is
influenced by the project, be carefully considered. The des-
cription of hydrologic and water quality impact sources which
follows is divided into several general categories, all of
which must be examined spatially and temporally.
Changes in Hydraulic Parameters. The basic purposes of
channelization necessitate that hydraulic characteristics be
altered to increase the efficiency of water passage. This
objective may be met in several ways. Channel straightening,
accomplished by realignment or cutting off meanders, results
in shortening the channel length and an increase in the slope
of the stream bed in the dhannelized reach. Consequently,
water velocities through the segment can be expected to be
greater, with a corresponding decrease in depth or stage for
a given flow. For some distance upstream and a lesser distance
downstream from a shortened channel, the surface profile would also
be lowered below that which would have occurred without channeli-
zation. In this situation, depicted in Figure IV-1, the stream
gradient is unstable, and there exists a tendency for erosion of
material from the channel bed and banks and increased deposition in
downstream reaches. Downstream flood stages may increase as a
result of this type of channelization project because of not only
the increased hydraulic capacity but also the loss of flood storage
capacity previously afforded by the longer natural channel and
adjoining flood plain. Changes in water depth and turbulence in
the channelized reach will have an effect on reaeration, and the
decrease in travel time may result in more rapid transport of pollu-
tant loads to downstream sections of the watercourse. For this rea-
son, it is important that existing waste sources and water quality
in the project area be adequately identified and described in the
EIS. If an areawide waste treatment management (Section 208)
plan has been prepared for the area, it may contain information on
nonpoint sources of pollution.
Also, levees may be incorporated in a channelization project
in order to confine river flow to a definite width and protect
adjacent flood plain areas from inundation. Spoil material from
channel excavation may be used as fill material for levee construc-
tion. Hydraulically, levees act to (a) increase velocity and river
stages through the section during floods, (b) increase the maximum
discharge at all points downstream, (c) decrease the time of travel
of the flood wave, (d) decrease surface slope of the stream for
a distance upstream", and (e) reduce valley storage. By preventing
flooding of low-lying areas, groundwater recharge associated with
overbank flooding and ponding of water will be decreased. During
times of flooding, water flowing over the flood plain is slowed by
friction from contact jwith__the soil surface,, trees, shrubs and _other
vegetation, and all except the very fine solids settle out. The
contact with vegetation allows the absorption of minerals, nu-
trients, and other pollutants that may be present in the water.
TV-9
-------
B .
=;.^iu^^jnanneiTr vi
Profile
__ Water surface
f^*t
E ~~f ~~~ Channel bottom
Genera1 Hydraulic Effects
Shortened channel length and
reduced channel storage
Increased velocity in affected
portion due to increased
gradient (B-E)
Decreased depth of flow from
A to F
Figure IV-1.
Source:
Potential Environmental Considerations
Change in reaeration, section AF
(may or may not be greater than
total reaeration formerly provided
in longer channel)
Change in total amount and type of
aquatic habitat, section BGE, resulting
from loss of riparian vegetation and
pool-riffle sequence of unchannelized
stream
Tendency for increased channel and
bank erosion (downcutting) for some dis-
tance above and below cutoff
Increased flood stages in downstream
sections
Increased sediment deposition in
downstream sections
Reduction of groundwater recharge
Hydraulic Effects of Channel Straightening (Cutoff)
and Related Environmental Considerations
Adapted from Schwab, G.O., R.K. Freuert, T.W. Edminster,
and K.K. Barnes, Soil and Water Conservation Engineering,
Second Edition (New York: John Wiley and Sons, Inc.),
1966, p. 344.
IV-3
-------
The capability of flood plains to remove suspended material will
be reduced in a leveed or channelized reach, resulting in greater
sediment transporfto downstream sections. Dissolved and absorbed
constituents would similarly pass through such a channel instead
of being .deposited on the flood plain.
Modification of an existing channel may be undertaken to
increase channel capacity. Alterations may entail (a) increasing
the channel cross section (width and/or depth) and (b) decreasing
resistance to flow.Generally, for the same increase in cross-
sectional area, deepening will be more effective than widening
in terms of hydraulic efficiency. Figure IV-2 illustrates some of
the general effects of channel deepening and widening. Resis-
tance to flow, or the "roughness" of a channel section, may be
decreased most simply by removing trees, stumps, vegetation, debris
and other obstructions that have accumulated. This method will
probably have a greater hydraulic effect on a small stream than
on a large stream. Low-flow regimes can also be affected by
channelization, particularly if land drainage is improved and
groundwater contributions to discharge are thereby reduced. If
the channelization project necessitates removal of trees along the
banks which formerly shaded the stream, the thermal regime may
also be altered. With a substantial increase in exposure of the
water surface, it is probable that diurnal temperature fluctuations
will increase, due to greater warming during the day but also faster
radiational cooling at night.
In special circumstances, channel lining with rock rip-rap,
concrete, vegetation, or other materials may be utilized to pro-
vide channel bottom and bank stabilization, and at the same time
enhance the hydraulic efficiency of the channel. Water quality
considerations in this context are basically the same as for
channel straightening: changes in travel time and factors affect-
ing reaeration. Installation of a smooth, uniform channel in which
water is deeper and less turbulent than in the natural stream is
likely to adversely affect assimilative capacity in the altered
segment. In unlined channels, the potential for bank erosion and
increased turbidity also exists. Noncohesive soils may be more
susceptible to erosion than fine-grained, cohesive materials.
In some cases, channelization will comprise only a part of
a more comprehensive land and water resources program in a water-
shed. Impoundments, retarding basins, sediment pools, and other
structures will modify flow regimes and water quality to some
degree. Retention of sediment behind dams or low weirs will result
in the discharge of clearer water which will tend to erode the
stream bed and banks and pick up a new suspended sediment load.
Possible reduction of flood peaks or augmentation of low flows
wouLd also affect flow conditions in a downstream channelized
reach. Natural water temperatures below impoundments may be re-
duced in the warm months due to deep, cold water releases or possibly
increased if surface waters exposed to solar radiation are discharged,
The reviewer should consult EPA's guidelines for review of EIS's
on impoundment projects! for further description of these impacts.
IV-4
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Natural water surface (low flow)
Existing channel and banks
Excavation on
one or both
sides
channel
cross-section
Channel water surface
(low flow)
Widening of Existing Channel
General Hydraulic Effects
Increased cross-sectional area
through which flow occurs.
Decreased water depth at
normal and low flows.
Reduced frequency of overbank
flooding.
Greater uniformity of velocity.
Potential Environmental Considerations
Greater exposure of water surface to
atmosphere.
Increased solar radiation and warming.
Loss of aquatic habitat, including
loss of cover for fish and loss
of stream bank vegetation.
Alteration of erosion-deposition
patterns.
Natural water surface
water surface
Existing channel bottom-'
New channel bottom f
Deepening of Existing Channel (Profile)
General Hydraulic Effects
Potential Environmental Considerations
Reduced water surface elevations. Change in sediment transport capacity.
More uniform gradient, due to Alteration of substrate.
elimination of pool-riffle Alteration of riparian wetlands and
sequence. vegetation.
Lowering of water table. Loss of aquatic habitat for some species
Figure IV-2. Hydraulic Effects of Channel Widening and Deepening,
and Related Environmental Considerations
-------
Changes in Land Use. Land use patterns can have a marked in-
fluence on watershed hydrology and water quality. Channel modi-
fications may contribute to changes in land use over the life of
the project, as when land drainage or flood protection is provided.
However, projected conditions of land use both in the immediate
area of channel improvement and in a broader region of possible
influence may have relevance to the identification and assessment
of environmental impacts. In the first place, land uses in the
upstream watershed affect hydrology and stream flow. Reductions of
forest cover due to silvicultural or agricultural activities,
urbanization, or other development tend to increase the volume
and decrease the time of concentration of surface runoff, causing
increased flood peaks downstream. This effect depends on the ex-
tent of such land use changes relative to total watershed area,
and may be highly significant on small watersheds. Channel modi-
fications, which generally increase flood stages in downstream reaches,
would have the effect of augmenting flood levels even further if
upstream watershed practices and activities increased runoff.
Therefore, consideration must also be given to flood plain land uses
below a channelization project, where flood hazards may increase.
Inputs of pollutants, including sediment, agricultural chemi-
cals, and possibly municipal or industrial wastes, may change as
land use patterns in a watershed are altered. Within the area
afforded flood protection or drainage benefits by channelization,
potential pollution will be related to the expected changes in land
use. It is likely that conversions of additional land to agricul-
tural use will cause some increase in sediment, nutrients, and dis-
solved solids loads to the channel. However, this may not occur
if the project simply improves productivity of existing agricul-
tural lands without stimulating new agriculture. Secondary effects
on water quality may be experienced if channelization leads to
development of adjacent flood plain areas. Land conservation measures
that: are integral components of federally assisted small
watershed projects may counteract possible water quality degrada-
tion from land use changes.
Construction and Maintenance Activities. Channelization can
involve a variety of construction activities and maintenance prac-
tices having the potential to directly or indirectly affect water
quality. Because project construction necessitates work directly
in the stream and in low-lying adjacent riparian areas, sediment
will usually be the principal pollutant. The types of construction
equipment utilized in channelization vary depending on the size of
the project, nature of construction specifications, and design
features. On small projects actual excavation would normally be
accomplished by dragline or power shovel situated on the stream
bank. For larger projects, self-loading scrapers, and bulldozers
may be utilized. Often work areas will be dewatered by construction
of coffer dams or diversion of streamflow. Shaping of channel
banks and placement of excavated material for berms or levees will
involve grading machinery as well as soil compaction equipment such
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as vibrators, sheep"s-foot rollers, and other devices. Although
not addressed in detail in these guidelines, channel deepening
and widening projects in estuaries and harbors for the purpose of
boating or shipping access are undertaken with barge-mounted mechani-
cal or hydraulic dredging equipment. Generally, equipment working
in the streambed rather than from the banks poses a greater threat
to water quality.
Excavation and earthmoving, removal of snags and other debris,
clearing of access and haul roads, and other activities can accelerate
soil erosion and result in the introduction of significant quanti-
ties of sediment to a watercourse. Suspended solids and turbidity
are important in that they are very noticeable forms of pollution;
however, conditions favorable to the production of sediment may
also cause the introduction or the release of other pollutants
that are absorbed on solid particles or present in the runoff
water. These may include organic, oxygen-demanding matter, chemi-
cal pollutants such as petroleum products, pesticides, fertilizers,
metals, and construction chemicals, and biological pollutants
(bacteria, fungi, and viruses) from the soil or due to improper
sanitation on the construction site. Generation of sediments and
runoff-related pollutants should decline rapidly following completion
of construction and installation of erosion protection and site
restoration measures. Over the longer term, periodic maintenance
of the channel involving removal of in-stream debris, aquatic vege-
tation, and terrestrial vegetation that is encroaching on the channel
banks, repair of bank protection, or redredging may be required.
As a basis for insuring that potential construction and
maintenance impacts on water quality have been identified, the re-
viewer should determine whether all major activities logically
required for installation of the project are discussed in the EIS
project description or other sections. In addition, a concise des-
cription of construction timing, phasing, and extent of operations
should be presented.
Groundwater. Groundwater effects from channelization result
from changes to the streambed and through modifications of flood-
plain and wetland recharge areas.
Changes to the streambed may affect its potential as a re-
charge area, by modifying any or all of several variables related
to recharge.potential. These variables include:
..time of water residence in the channel.,
..depth of channel (e.g. above or below the water table),
..slopes and elevations of the groundwater (piezometric) surface and
stream gradient,
..and the transmissivity of sediments (in the channel bed and ad-
jacent banks) to groundwater flow.
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Transmissivity is a measure of infiltration and groundwater-move-
ment potential and is itself dependent upon variables such as:
..permeability and porosity characteristics of the banks and channel
bed,
..accumulated silt and clay in the channel bed, for example, which
will impair infiltration or recharge by the channel; colloidal
material in the water may reduce aquifer transmissibility.
A channelized reach of stream, as contrasted with a natural
stream segment, will often result in a shorter length of time during
which a given volume of water is in contact with the land surface
thereby decreasing infiltration and the channel's potential to act
as an influent stream. (Influent conditions occur when stream
beds serve as groundwater recharge areas; "effluent" conditions occur
when groundwater discharges to streams, as in most perennial streams
where groundwater contributions to streamflow are equivalent to
"base flow".) Both infiltration from the channel to groundwater
reserves, or transfer of volumes in the opposite direction may be
simultaneous effects observed at different places along a channel
or stream, or they may occur at the same place at different times,
for example, during drought conditions or after storms.
Although the effects of channelization on groundwater have
been extensively reported in monographs and journals, it is diffi-
cult to draw generalizations about predicting those effects. The
ADL report, in its assessment of "watertable changes and stream
recharge" across the U.S., makes the following observations:
A proper factual assessment of the effects of channel
modification on groundwater levels and the capacity of
drainage areas to recharge streams is seriously hampered
by lack of data. While effects are generally assumed
or predictable, specific situations are extremely
difficult to document with accuracy . . . Each localized
situation presents such high variability and measure-
ment has been so scattered, that no conclusive ground-
water and surface flow data are found that can be directly
related to drained lands and adjacent downstream flows.
The report goes on to state that, of the 42 channel projects studied,
only 13 appear to have had "an uncertain and mixed cause-and-effect
relationship" on adverse lowering of groundwater levels or on the
capacity of drainage areas to recharge streamflow. Another 20 pro-
jects were "unimportant" in modifying groundwater levels. The
conditions characterizing channelization projects which had mini-
mum effects on groundwater included:
- a short channelized segment relative to the impacted groundwater
basin;
- a small adjacent zone-of-influence in channels relative to natural
inflow to such zones;
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- a floodplain which is narrowly confined and/or has relatively
steep gradient;
- a high average rate or precipitation, distributed over all seasons;
- the channel traverses bedrock outcrops or has a bed of rock/gravel;
- an absence of opportunity for post-project and off-channel drainage
extensions;
- the presence of upstream storage which acts to minimize low flow
conditions and to recharge watershed aquifers;
- channel flow which is ephemeral under natural conditions;
- control structures exist in the channel to regulate drainage and
flow;
- construction/maintenance activities are predominantly clearing
and snagging (instead of excavation).
For example, the use of in-channel control structures, such as low-
level weirs and dams may serve to transform channels into channelized
resorvoirs. If the channels are unlined, the effect of water reten-
tion in the channel may serve to replenish groundwater reserves,
to raise groundwater levels, and to irrigate plant root zones in
adjacent bank areas. Channels are then similar to what are termed
"influent" streams. Without such control structures, an unlined
channel, if dredged in the water table, will act as a drain and lower
the water table. Lining the channel with impermeable material may
also negate the drainage effect, but some drainage may be necessary
to prevent uplift, or "floating", of the channel lining.
Vegetational changes will also affect the amount of water
available for groundwater recharge. For example, differing species
of vegetation, especially such phreatophytes (water-seeking plants)
as saltcedar, greasewood, mesquite, and alfalfa exert a seasonal
influence on groundwater recharge rates. Losses from evapotranspira-
tion resulting from changes from forest land to crop land will also
result in decrease in water for recharge.
Floodplains and Wetlands. Channelized segments may diminish
that, potential recharge to aquifers which otherwise occurs in flood-
plains by denying access to these over-bank areas by normal flood
volumes. This has been a critical issue in some areas such as
the Kissimmee River Control Project of Central Florida.3 Similarly,
drainage of wetlands associated with channelization projects directly
lowers the water table and also greatly reduces the wetlands' re-
charge potential. The physical changes in surface/groundwater
conditions that may be caused by channelization can also have an
effect on plant cover; the riparian and wetland vegetation that exists
along a stream or channel will respond to changes in groundwater levels,
Bottom land and wetland fauna may be gradually eliminated in favor
of upland vegetation associations by lowering groundwater levels
IV-9
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alone, or the process may be accelerated by conversion of the lands
to other than natural open space uses. In most cases the drainage
functions of channels will have a much greater impact on groundwater
levels and groundwater quality than will the physical modification
of the streambed itself, particularly where tributary drains and other
facilities will be installed in conjunction with the main channel
for drainage of upland as well as riparian areas. Any changes in
vegetative cover initially induced by land drainage and reduction
of groundwater recharge may in turn affect groundwater by retarding
or enhancing runoff or because of differing consumption and evapo-
transpiration rates. The cause-effect relationships among channel-
ization, groundwater, and vegetation can be complex and underscore
the difficulties of determining the nature of effects on groundwater
hydrology.
Effects on Groundwater Quality. Water quality impacts on
groundwater resulting from channelization activities may result
from the channelization work itself, including wetlands drainage,
and from the shifts in land uses or intensities brought on by channeli-
zation. During both the construction and maintenance phases there
may be appreciable disturbances to the groundwater regime in the
project vicinity. Interception, augmentation, or diminution of ground-
water flows by: (1) excavation of the channel itself or by
collecting drains, (2) the placement of spoil on top of recharge
areas, and (3) the ponding of waters in temporary or permanent
sediment basins are typical of those impacts which should be
assessed. The existence of such impacts may be explicitly stated in
the EIS or may have to be deduced by the reviewer.
The effects of shifts in land use or intensities different from
pre-channelization conditions, will also affect groundwater quality.
For example, the drainage of the wetlands in a Florida watershed
resulted in increasing available pasturage, occasioning an increased
density of cattle and subsequent pollution problems with animal
wastes in the waterways of the project. Changes in agricultural
practices, the quantity and character of domestic or industrial
wastewater discharges are the principal sources of impacts on ground-
water quality. The pathways of pollutants which enter the ground-
water because of the presence of channels depend upon whether the
channel is receiving or discharging groundwater at specified times
or places. Measured concentrations of pollutants and nutrients in
groundwater are obtainable from water quality analyses. But the
chemical modification of these pollutants (e.g. denitrification of
nitrates) while in aquifers, and their interaction in channels (or
other water bodies) with waters from other sources are not well
understood.
The depletion of groundwater reserves subsequently may cause a
reduction of instream flows which is of special concern during
periods of low flow. This can have the following effects upon water
quality:
IV-10
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..prevention of in-channel oxidation and dilution of organic
chemicals,
..raising water temperatures (especially in the summer) thereby
reducing the dissolved oxygen content of the waters,
..degrading water quality aesthetics (e.g. sight and odor),
..increasing the rate of accumulation of sediment, litter and
debris in the channel thereby diminishing hydraulic efficiency.
IV.A.2. Review of Impact Quantification
A wide range of techniques may be used to quantify hydrologic
and water quality impacts of channelization. Since careful investi-
gation of flows and hydraulic response is usually required for the
proper design and functioning of a channel, these factors are likely
to be covered in some detail, if not in the EIS then in corres-
ponding technical engineering and planning reports for the project.
Methods presently used by Federal agencies can provide reliable
characterizations of existing and postproject hydraulics. In many
cases too, probable effects on water quality and waste assimilation
can be interpreted from knowledge of a channel's hydraulic behavior
under various flow conditions. However, the water quality analysis
is apt to be complicated by many factors outside of actual channel
modification, including changes in land use and other water resources
development projects in the watershed or basin. Impact prediction
becomes more speculative as uncertainties in future land use and
wastewater sources are introduced. Nevertheless, the consequences
of possible development and land use can often be described, at least
qualitatively, in terms of their pollution potential or effect on
watershed hydrology. It is important that the interactions between
the direct effects of channelization and the indirect influences
of land use be addressed in impact estimation. The major subdivi-
sions of this section therefore complement each other in some ways,
illustrating the interrelatedness of different sources of impacts
and the need for a sufficiently broad view of a channel project.
Changes in Hydraulic Parameters. Because the hydraulic regime
of a channel has relevance to many of the impacts that are likely
to occur, adequate quantification of flow conditions is basic to
impact evaluation. Of primary interest are the changes in stream
geometry, flow, depth, substrate and other characteristics due to
channel modification, relative to the existing situation. The
starting point for impact quantification is, therefore, a thorough
description of hydrology and water quality in the area to be affect-
ed by channelization.
Basic Hydrologic and Water Quality Characteristics. Existing
flow characteristics in the project area must be described sufficiently
to indicate the nature and extent of flooding, drainage or other
problems to be rectified by channelization. For purposes of design,
high flows are usually most important, but normal and low flow re-
gimes are also of interest for water quality management. Flood
IV-11
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discharges in and downstream from the reaches where channel improve-
ments are proposed should be related to frequency of occurrence/
stream stage, and the flood plain areas subjected to inundation.
The- low-flow characteristics should be similarly quantified, as, for
example, the average minimum consecutive 7-day flow to be expected
once in 10 years, which is normally used for interpretation of
state water quality standards and the design of wastewater treat-
ment facilities. In the absence of fairly long historical records
of discharge (such as those provided by USGS stream gauging sta-
tions) , high water marks from previous flood events and field measure-
ments of velocity, depth, and cross-sectional characteristics may
be used to construct stage-discharge relationships, water surface
profiles, and other hydrographic information.
Other attributes of the existing stream environment are funda-
mental to the evaluation of impacts of channelization and must
be described, quantitatively where possible, in the EIS. Pertinent
elements include:
- Length and normal width of stream(s) in the proposed project
area
- Velocity and depth at representative cross-sections and travel
times through the reach, particularly for the low-flow
condition
- Location, type, height, and density of woody vegetation along
both stream banks
- River bottom composition including location and linear extent
of various substrate types (silty, sandy, gravelly, etc.)
- Sediment yields from upstream drainage area
- Present water quality and classification
- Point and nonpoint sources of wastewater discharges
The physical stream characteristics are important because of
their relationship to water quality and assimilative capacity. The
extant to which assimilative capacity must be considered is primarily
a function of present and projected water uses and wastewater dis-
charges in the watershed. For example, some of the Soil Conserva-
tion Service small watershed projects implemented under Public
Law 566 are located in areas receiving no municipal or industrial
discharges. In more developed watersheds, however, water quality
implications of channel modifications may be important.
Detailed descriptive and quantitative information on surface
watrr qualty, present and probable future waste loads, and assimi-
latJve capacities may be contained in state or other water quality
surveys, the 303(e) basin plan, and the 208 areawide waste treat-
ment management plan if one has been prepared for the area. Re-
sults of any site-specific investigations that have been conducted,
TTT_ 1 ">
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either during project planning or as part of State or Federal water
quality management programs, may have relevance to estimation of
channelization impacts.
Quantification of impacts due to channelization is rarely a
simple, straightforward procedure. The direct implications of altered
hydrographic behavior on downstream flood stages can be identified
and quantified fairly accurately using tested methods of hydraulic
and hydrologic analysis. The validity of estimates of water quality
impacts, on the other hand, hinges on the proper interpretation
of the altered stream flow and channel conditions. In evaluating
the treatment of hydrology-related water quality impacts in an
EIS, the reviewer should keep in mind the potential significance
of various physical features of the existing stream and proposed
channel project. For instance, oxygen transfer or reaeration in a
stream or channel generally increases with velocity and is inverse-
ly related to depth. Irregularities in the channel bottom, such
as gravel, rocks and other obstructions create turbulence and in-
crease reaeration. The nature of the benthic community, whose pro-
ductivity depends heavily on the type of substrate, is also a very
important factor in the self-purification ability of the stream.
Downstream Hydrologic Effects. A quantitative analysis of the
post-project hydrographic regime should be presented with detail
sufficient for comparison with preproject conditions. Such an
analysis must take into account other identifiable influences on
streamflow in the watershed, particularly upstream reservoirs which
may reduce peak flows and possibly augment low flows through the
channelized section. In considering potential downstream effects
due to an increase in hydraulic efficiency in a channelized reach,
estimates of downstream flood stages corresponding to design peak
discharges are required. The Soil Conservation Service guide,
Planning and Design of Opgn Channels,4 recommends that where
downstream effects of channel improvement are significant, the analysis
should be carried downstream to the point where effects on flood
stages have been dissipated. These predictions are critical be-
cause of the possibility that channel modification may ultimately
contribute to the need for further protective measures downstream.
Problems may arise particularly if downstream flood plain areas are
being, or are expected to be, converted to more intensive uses
susceptible to flood damages.
Methods appropriate for quantifying effects on downstream flood
flows vary with complexity of the stream network, extent of reser-
voir and other influences on flow, and the location and scope of the
proposed project. Basic operational techniques normally used by
Federal agencies involved in planning and design of channel improve-
ments range from computation of surface water profiles to hydrologic
flow or storage routing methods. Various Federal agency and other
publications^~^delineate the predictive techniques most frequently
used in practical planning and design application. Data on:
channel cross-sections, roughness, slope for the stream or channel
sections of interest, and, for the routing methods, inflow hydro-
graphs are required. Most of this data will have been collected
IV-13
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during project planning as it is essential to the design of channel
improvements. The reviewer needs to ensure, nevertheless, that
potential effects on downstream flood patterns have been quantified.
If this information is lacking from the EIS, a request for more
quantitative data is reasonable and should be made in the re-
viewer's comments. Description of the extent and characteristics
of floodplain areas that would be affected should accompany the
analysis of changes in downstream flood stages. As a general guide,
impacts on flood stages will probably be most significant in
reaches immediately downstream from a channel project, decreasing
as flow contributions from larger drainage areas are added.
Hydrologic Effects on Waste Assimilation. Although much more
difficult to quantify, water quality and other benefits may be
associated with overbank flooding, primarily the removal of a por-
tion of a stream's suspended solids load, nutrients, and other
dissolved materials. By confining a stream to an artificial
channel, sediments and other pollutants that normally settle out
on adjacent floodplains would be conveyed downstream adding to the
sediment load. Obviously a trade-off between sediment/flooding
damages and the natural purification ability of a stream is in-
volved. It is important that the potential impacts of channelization
on the natural role of floodplains in removing sediment and other
impurities be recognized, even if the magnitude of effects on water
quality cannot be easily estimated.
Normal and low-flow regimes also need to be evaluated for a
channel modification project. Discharge estimates should reflect
any existing and anticipated influences on flow through the channel,
such as flow regulation by upstream impoundments, diversions for
water supply or irrigation, alteration of groundwater/stream
interactions, or other water management projects. Channelization
may have beneficial or adverse impacts on natural degradation and
assimilation of pollutants, depending on the resulting flow charac-
teristics. Techniques for quantifying these impacts may range from
judgmental estimates based on channel dimensions, slope and other
factors for short channel modifications on small streams to more
detailed analyses involving estimation of reaction coefficients
and modelling for larger projects where water quality is an impor-
tant issue. For either approach, a clear description of channel
geometry and its effects on discharge should be provided, at least
for a representative low flow. In essence, the EIS must present
data sufficient to determine how the length, width, slope, bottom
composition, and water velocity and depth in a channelized section
will differ from preproject conditions.
In the case of channel straightening, passage of water through
the section will be more rapid, thereby reducing residence time. Al-
though the effects of a channel on travel time cannot be directly
measured in the planning phase, estimates of average velocity and
channel dimensions will permit accurate determinations. Because of
the need to design channels so that excessive deposition of suspended
material will not occur during low flows or scour at high flows, the
IV-14
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planning agency should have developed estimates of postproject velo-
city patterns for the reach to be channelized. The magnitude of
the change in travel time is related to the change in channel length
and slope, bottom roughness, and cross-sectional area. Oxygen-
demanding wastes as well as bacteria and other pollutants will be
borne through such a channel more rapidly with less time for puri-
fication, thus increasing oxygen demand and water quality degrada-
tion downstream.
When channelization follows an existing stream alignment, changes
in cross-sectional area and bottom characteristics are the major
factors that may affect the water quality response of the stream.
Anticipated low-flow conditions in the channel, including average
water depths and widths should be quantified in the EIS and contrasted
with existing flow parameters. In addition, expected alterations
of the stream bed must be described. Generally, for example,
destruction of rocky riffle areas will have a more significant
adverse effect on natural purification than will the excavation of
alluvial silt and mud. Clearing, snagging, and removal of other
obstructions should be described in terms of the areas affected.
Elimination of debris that enhances turbulence may contribute to
lowered reaeration. On the other hand, increasing the bottom width
of a channel will cause a reduction of water depth and exposure of
a greater water surface area to atmospheric reaeration. If detailed
field studies of oxidation and reaeration constants have been performed
in connection with basin planning or other studies, this information
would facilitate prediction of the impacts of channel improvements.
Otherwise, careful comparison of qualitative data on channel charac-
teristics for pre- and postproject conditions should be made. De-
tailed water quality modelling would not, in most cases, improve
materially the estimation of water quality impacts that can be
performed by descriptive and semiquantitative methods. Exceptions
might be the projects on larger streams where channel geometry is
to be modified significantly over long stretches and where numerous
waste discharges enter the project area or upstream watercourses.
Hydraulic Influences on Channel Stability and Erosion. The
hydraulic changes accompanying channelization necessarily lead to
differences in erosion and sedimentation patterns within, upstream,
and downstream from a project area. The soils and geology of the lands
through which a channel may be constructed, the characteristics of
the suspended and bed load, and velocity regime are the primary
determinants of bottom composition, unless some kind of channel
lining (rock, rip-rap, concrete, vegetation, or others) is used.
Table IV-1, based on field investigations of 42 channelization pro-
jects, provides initial guidance on conditions under which signifi-
cant erosion and sedimentation problems are not likely within a pro-
posod channel. Conversely, conditions deviating from those des-
cribed suggest the possibility of difficulties over the life of a
project, the need for special attention in the EIS and perhaps modi-
fication of project design.
3V-15
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Table IV-1. Conditions Favoring Low Potential Contri-
butions to Erosion and Sedimentation Problems Within a
Channel Modification Area
Short channelized reach relative to land-water system
Slight design gradient
Moderate design velocities
Moderate channel-bank design slope
Limited excavation
Limited realignment
Riprapping or concrete lining of critical areas
Seemingly stable channel beds
Banks stabilized by vegetation
Mitigation measures such as drop structures or sediment
traps in upstream storage reservoirs to reduce sediment
transport
SOURCE: A.D. Little, Inc., Report on Channel Modifications, Volume I,
for the Council on Environmental Quality, U.S. Government
Printing Office, Washington, D.C., March 1973, p. 163.
Quantification of the expected performance of a channel with
respect to aggradation and degradation is approached through sta-
bility analysis, which takes into account the factors of geology,
flow, and sediment transport. With respect to judging the differ-
ing potential for erosion in channels with different cross-sectional
dimensions, Chow-10 offers the following general rule:
When other conditions are the same, a deeper channel will con-
vey water at a higher mean velocity without erosion than
a shallower one . . . probably because the scouring is
caused primarily by the bottom velocities and, for the
same mean velocity, the bottom velocities are greater in
the shallower channel.
A qualitative assessment of bed stability and deposition
of suspended sediments and moving bed loads in alluvial channels
can be obtained by the method of permissible velocities.11 This
technique has been expanded and is currently being used by the
Soil Conservation Service12 for certain design situations. Basic
data requirements are the hydraulics and transport characteristics
of the channel and the character of the earth materials through
which the channel will pass (grain-size distribution, cohesiveness,
IV-16
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plasticity, etc.).
More detailed investigations of channel stability with respect
to sediment transport may be necessary when significant amounts of
sediment, either suspended or bedload, are introduced from upstream
sources that will affect erosion and deposition in the channelized
reach. Perhaps the most widely used empirical method for total load
computation was developed by Einstein. ^3 This prediction method
computes the equilibrium rate of scour and deposition based on
channel cross-section, sediment characteristics, and properties of
flow regimes. The method can be used in hand calculations for simple
channel cross-sections or short reaches to predict sediment dis-
charge rate. Since the rate of bedload sediment transport has been
shown to be strongly related to mean velocity, at least for materials
in the size range of medium to fine sand, the SCS makes use of this
relationship in channel stability design when applicable. Where
velocity characteristics may change considerably, as in the case
of straightening and shortening a stream channel, potential for
sediment erosion, transport, and deposition should be analyzed
for a distance upstream and downstream as well as in the project
area itself.
In special cases involving large projects or multiple influences
on sediment transport (such as impoundments), computer models
may be used for studying the short- and long-term effects of
reservoirs, levees, and channel modifications. The effect of
altering the frequency and duration of flow can be investigated in
terms of the response of the bed and water surface profiles. Such
a model developed for the Corps' Hydrologic Engineering Center14
includes predictions of: total bed material, volume and gradation
of material deposited, armoring of the bed surface, suspended sedi-
ment load and aggradation, and resulting bed geometry. In addition,
sediment outflow at the end of the modelled channel is calculated.
It should be noted that the use of computer models is comparative-
ly expensive and would be appropriate only for assessment of large
or complex projects or a series of projects in a basin.
The reliability of results obtained by any of the methods men-
tioned above depends on the type and amount of baseline data on
which sediment-related predictions are based. Data requirements
for channel planning purposes should, in general, be linked to the
scope of the project and the value of the resources that may be
affected. For many upper watershed projects, little or no quanti-
tative information on hydrology and sediment yields may exist.
Representative hydrological estimates are usually constructed, as
discussed earlier, without undertaking extensive field investiga-
tions. Measuring the sedimentation characteristics of a stream,
howcsver, is one of the most difficult tasks in an environmental
monitoring program. In many cases, estimation of the availability
of movable bed material within and upstream from a proposed channel
improvement, rather than actual field measurements of sediment
discharge rate, will be made for purposes of stability design. Data
descriptive of the geomorphology of deposits in the project area
should be included in the EIS. Knowledge of watershed land uses and
IV-17
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related sediment yields is also relevant to estimation of po-
tential erosion and sedimentation problems. Conditions dif-
fering greatly from those described in Table IV-1 may warrant
field measurements of sediment discharge. A good synopsis of
the methods for measuring suspended, bedload, and total sedi-
ment discharges is the report "Determination of Fluvial Sedi-
ment Discharges." 15
The reviewer should know that the techniques for predicting
sediment transport processes are for noncohesive sediments
(those which are not prone to flocculation or aggregation but
behave more like sand grains). The state-of-the-art for quan-
titatively estimating erodibility of fine-grained cohesive
materials is not as well developed; experience and judgment must
therefore be relied on more heavily in these situations.
Techniques in use for estimating channel stability are generally
applicable to analysis of bank stability as well, except that
additional forces must be considered. Methods from soil mechanics
for evaluating the effects of alternate wetting and drying,
seepage, slope, and other factors are normally used. As a general
rule, the vulnerability to erosion of unlined channel banks and
bottoms constructed in noncohesive sediments increases with de-
creasing grain size, into the sand range. Mixtures of silts and
clays cannot be categorized as easily, except that fine-grained
soils with high percentages of clay and high plasticity are often
more erosion-resistant than sandy material.
Changes in Channel Substrate. One other aspect that should
be addressed in the EIS is the probable change in substrate compo-
sition over time. In channels that follow an existing stream course
with no major changes in gradient, the bed may be very much like
that of the existing stream. However, if velocities are increased
such that some channel scouring will occur, the fine-grained frac-
tion of well-sorted sediments may be eroded, leaving coarser gravel
or cobbles as an "armor" against further erosion of the channel.
This possibility is sometimes anticipated and planned for in channel
design. Although difficult to quantify, the nature of the bottom
plays an important role in the self-purification of a stream or
channel. Besides physical influences of the substrate on turbu-
lence and reaeration, the character of the bottom is a significant
factor in determining the diversity and abundance of benthic organisms
that will inhabit a channel. The benthic organisms in turn consume
organic detritus and otherwise aid in removal of impurities from
the overlying water. Generally, clean stony bottoms will exhibit
a richer diversity of benthic fauna, both in numbers of species
and total biomass, than will silty reaches and pools.16 Section
IV.B., Aquatic Ecology Impacts, presents further information on
these relationships.
Changes in Temperature Regime. The issue of thermal regime
changes will not be important for all channel projects. Generally,
construction activities that necessitate removal of shade-producing
trees and vegetation from the banks of small streams are likely
to cause potentially significant changes in temperature patterns.
TW_ 1 O
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Cooper et al. 17 describe several techniques for estimating surface
water temperatures which can provide temperature profiles based on
stream geometry, inflows, outflows, inflow termperatures, and meteoro-
logic data. Brown, 18 however, has developed a prediction method
that focuses more directly on the probable effect of channelization,
that is, the maximum change in water temperature as a result of
clearcutting of streamside forests. Basic data requirements for
applying the method are: the boundaries of the proposed clearcutting,
minimum summer discharge and corresponding stream surface area and
travel time, and readily obtainable solar data. The reviewer
should note that shaded zones below cleared stream segments will
probably not cause any cooling of the stream once its temperature
has risen due to greater exposure to the sun.
The report, Temperature and Aquatic Life,19 provides a documented
summary of important effects of water temperature and changes on
chemical reactions, bacteria, fish, aquatic plants, and benthos
which should aid in reviewing the EIS treatment of the impacts
of thermal regime changes. From a water quality perspective,
chemical reaction rates geneally increase as temperature is increased
and oxygen solubility decreases, meaning that the decay of organic
substances will have a greater adverse effect on DO levels at ele-
vated temperatures. Section IV.B. further addresses the ecological
consequences of temperature alterations that should be considered
in the EIS.
Changes in Watershed Land Use. Basically, any changes in
land use can affect the quantity and quality of runoff, and thus
the hydrologic regime and surface water quality as well. However,
neither the prediction of future land use nor the estimation of
hydrology/water quality effects of a particular land use is an
easy task. For areas directly affected by flood control, drainage,
or other channel functions, the EIS must contain descriptions ade-
quate to quantitatively compare present and forecast (postproject)
land uses in terms of location, intensity, and the acreages involved.
Fertilizer and pesticide application rates and total loadings without
and with the project should be estimated for affected agricultural
lands, as should the ameliorating influences of any land treatment
and soil conservation practices to be undertaken adjunct to struc-
tural measures. The EIS should also discuss conversions of open or
lightly developed flood plain lands to more intensive residential
or other urban uses that may take place over the life of the project.
The projected course of land use and development in a water-
shed, whether or not influenced by channel modifications, is rele-
vant to the estimation of impacts. The greatest potential for sig-
nifjcant changes in hydrology and water quality exists when sub-
stantial conversions and alterations of land use and vegetative
cover are expected. From a hydrologic perspective, runoff rates
and volumes are closely related to land use. A general ranking of
runoff potential, from low to high, for different land uses on
a given land area (and soil type) might be: forest, meadow, close-
seeded legumes, small grains, row crops, residential with storm
drainage system, and commercial and business areas. Trends in
IV-19
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watershed land use toward removal of forests or urbanization
can thus be expected to increase flood discharges. Installation
of drainage facilities on agricultural land in conjuction with channel-
ization would have the same effect.
It is important, therefore, that hydrologic analyses reflect
probable changes in runoff rates and peak flows for future land
use patterns. The Soil Conservation Service20 has developed
methods for estimating the relationship of runoff to character-
istics of soil, land use, and land treatment practices such as
contour plowing or terracing. The methods have been designed
for use in watersheds where historical streamflow records do not
exist, since most SCS projects are located in ungauged watersheds.
Input requirements are rainfall, soils, vegetative cover, and topo-
graphic data, all of which are ordinarily available or readily
obtainable in enough detail to make preliminary estimates of run-
off for purposes of watershed planning.
On small watersheds that are undergoing or expected to under-
go significant changes in land use, hydrologic impacts can be
substantial, with peak flood discharges increasing in magnitude
by several times. Intensive silvicultural activity, conversion
of forest lands to agricultural use, and urbanization are the
major shifts that must be considered. The publication, Rainfall-
Runoff Relations on Urban and Rural Areas,21 illustrates the impacts
that various degrees of urbanization,as measured by population
density, can have on flood peaks. The reviewer should ensure that
the effects of land use changes over the life of the project have
been considered in hydrologic estimates.
The water quality aspects of land use present greater diffi-
culties for quantification. It does not necessarily follow, for
example, that more intensive agriculture on lands drained or pro-
tected from flooding by a channel oroject will lead to introduction
of greater amounts of pollutants to the watercourse. For agricultural
lands directly affected by channelization, the EIS should present
quantitative estimates of both existing and projected applications
(per unit area and total loading) of agricultural chemicals including
pesticides and fertilizers. Such values will only indicate the
potential for agricultural pollution; resulting effects on water
quality will be influenced by land treatment, agricultural chemi-
cal application practices, and other factors. The reviewer should
note also that agricultural lands are one of the largest contri-
butors of sediments to surface waters.
Uttormark et £l.22 present a thorough search and compilation
of data from literature on nutrient loadings of agricultural, forest
and urban runoff. Generally, nutrient content of urban runoff was
found to be highest, and from forests, the lowest. Tables 9, 11,
and 13 from this publication should be consulted for information
on the variability of nutrient export with land use, crop type, and
other factors. Statistical analyses of National Eutrophication
Survey data 23 also give some insight on probable effects of urban
and agricultural land uses on stream nutrient levels, for the region
east of the Mississippi River.
IV-20
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The basis for conclusions reached about changes in pollutant
inputs from affected lands should be apparent to the reviewer.
Unless important shifts in the kinds of crops grown, the acreages
under cultivation, or land management are foreseen, agricultural
pollutant levels are not likely to change considerably as a result
of project construction and operation. Conversion of flood-
protected areas to urban uses may be expected to cause an increase
in pollutants transported by stormwater runoff. In most cases,
detailed site-specific modelling or predictive methods will not
be feasible (or even reliable) for predicting these impacts;
therefore, descriptions of present and projected land uses become
particularly important and must be presented in enough detail to
permit judgments of the magnitude of probable impacts.
Construction and Maintenance Activities. The quantification
of hydrological and water quality impacts traceable to construction
and maintenance activities is fundamentally related to the scale
of the project. Lengths and widths of channel projects may vary by
several orders of magnitude, for the scale of a project is deter-
mined not only by its purpose but by constraints imposed by channel
design standards and competing uses for land resources. It is im-
portant, therefore, that the EIS initially quantify the areal
impact of the proposed action. The significance of this impact
is measurable in acres of land allocated to the project and its
appurtenances and contrasted with resource values which will be
altered or destroyed by the channel, as, for example, miles of a
free-flowing natural stream or acres of timberland. In those cases
where the quality of the proposed channel is already seriously
degraded, as they may be in an urban flood improvement project
or previously modified stream, the reviewer should be sensitive
to potential benefits (e.g. aesthetics, warm water fishery, etc.)
that the project may provide.
In addition to overall project scale, impact variables are
introduced by the characteristics and constraints of environmental
conditions at the site. The significance of these characteristics
is related principally to their influence on sediment generation
and water quality impacts traceable to increased turbidity. These
environmental characteristics may be categorized as follows:
Topography - which may include sites which are nearly flat
and dry, flat and wet, or steeply inclined;
Climatic conditions - which include variations in temperature,
rainfall, and prevailing wind intensities
and direction;
Vegetative cover - including such diverse types as intensively
urbanized areas, forests and grasslands,
and sparsely vegetated steppes.
Soil types are classified by a number of systems on the basis
of grain size (texture), sorting and grading (structure) as well
as various engineering indices. (One commonly used system is the
IV-21
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"Unified Classification System"). 24 Of principal concern in
channel construction and maintenance is the susceptibility of soils
to erosion - both by channel flow (in unlined channels) and by
rainfall, wind, and/or gravity on exposed soils. Characteristics
of high resistance to erosion are not necessarily coincident with
those of compressibility (measuring resistance to the influence
of gravity). For this reason channel beds and channel banks of
the same material may generate sediment volumes differently
because forces acting on them are different. Table IV-2 below
shows the relative desirability of several soil types to erosion-
resistance and compaction, ranked from #1 (best) to #9 (worst):
Table IV-2. General Ranking of Soil Types
With Respect to Erosion Resistance and Compaction
Rank
Erosion Resistance
Compaction
1
2
3
4
5
6
7
gravels & gravelly sands
clayey gravels & gravel-sand-
clay mixtures
silty gravels & gravel-sand-
clay mixtures
clayey sands & sand-clay mix-
tures
well to poorly graded sands
with gravel
silty sands with gravel
inorganic clays of low
plasticity
inorganic clays of high
plasticity
clayey gravels & gravel-sand-
clay mixtures
clayey sands & sand-clay mix-
tures
inorganic clays of low plas-
ticity
silty gravels w/sand admixture
silty sands
inorganic silts with clay and
low plasticity
organic silts & clays of low
plasticity
inorganic silts & clays of high
plasticity
Peat and other organic soils-
Source: U.S.D.A., SCS, Engineering Field Manual for Conservation
Practices, 1973, p. 4-18.
-2 2
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Correlations of soil types with water velocities, on the basis
of erosion resistance, appear in several handbooks.25'26 In general,
the following table represents a consensus of these correlations.
Table IV-3. Suggested Water Velocities
Not to be Exceeded in Various Soil Types
Soil TextureMean Water Velocity (ft/sec)
Light, loose sand 1.25
Coarse clean sand or light sandy soil 1.75
Sandy loam 2.50
Silt loam, alluvial soil, average loam 3.00
Clay loam 3.75
Stiff clay, fine gravel, gravelly soil 4.50
Graded silt to cobbles 5.50
Shale, coarse gravel 6.00
Topography has an effect on the sediment generated by channel
projects because adjacent slopes and channel gradients influence
runoff volumes and stream or channel velocities. Channel projects
designed for drainage of wetlands are less frequently found in
regions of appreciable topographic relief than are flood flow channels
Another generalization is that areas at higher elevation often
have less soil cover susceptible to erosion than do low-lying areas.
An aid to estimation of the influence of topography on a channel
project is the comparison of parameters of the proposed channel
project with that of a nearby natural stream. To the extent that
the channel nearly conforms to natural grade and alignment the
comparison after the stabilization of construction-induced
impacts has been reached is a valid one. Hydraulic systems,
however, whether natural or man-made, are dynamic systems in vary-
ing, or relative, degrees of stability.
Topographic influences may also have a bearing on the areal
extent of a watershed or the variability of climatic conditions in
the watershed. These variables will influence flood hydrographs
and river stages, thus imposing constraints on construction and
maintenance schedules which, ideally, should coincide with low flow
periods.
IV-2 3
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Groundwater impacts are more easily anticipated and evaluated
in lowlands than in areas of relief, but in both areas the measur-
able effects upon water quality and ecosystems induced by construc-
tion activities will be delayed.
During construction and maintenance activities topographic
(e.g. gradient) influences at the site are relevant most especially
to soil stability in the channel and spoil disposal areas. The
cohesiveness of soils and rock strata and their resistance to erosion
are more critical, in terms of volumes of sediment entering the
channel, than any other measurable environmental parameter.
Climatic conditions are project variables to be identified
and quantified for construction-induced impacts. Rainfall is per-
haps the most significant of these variables both its seasonal
pattern and its intensity. Hydrographs of flows in comparable
streams within the project area are of assistance in anticipating
the frequencies and volumes of high flows which occur in response
to rainfall (and/or snow melt), as well as intervening periods of
low flow. Insofar as impacts of construction and maintenance are
concerned rainfall data has specific relevance to:
..the timing of construction and maintenance activities
so as to avoid periods of protracted rainfall or those of
high intensity,
..the scheduling of mitigating and/or preventive measures taken
to prevent soil erosion during rainy periods; or, if coffer-
dams or other construction aids are used, to augment or
divert low flows to maintain downstream water quality stan-
dards .
Table IV-4 illustrates and compares the yield of sediment from
a denuded and thereafter sodded road cut slope (i.e. similar to
a channel cut) in Oregon.
Except in areas of high aridity construction-induced impacts
on water quality resulting from wind erosion are insignificant.
In areas of high aridity loess and other fine soils in the region
which are disturbed or scarified may accumulate in the project's
channels and impair both hydraulic efficiency and water quality
standards. Or these same soils, disturbed at the project site,
may cause objectionable impacts on lands adjacent to the project.
Predictive methods for estimating soil and sediment loss by wind
erosion may be referred to if needed. 27,28
The influence of high temperatures during periods of construc-
tion and maintenance, especially to the extent that they coincide
with periods of low flow, may cause violation of water quality
standards, especially those of dissolved oxygen. Mucking and the
removal of accumulated debris during these periods -- especially
the removal of organic materials may cause not only the release
of pollutants to stream flow and the lowering of dissolved oxygen
IV-2 4
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content of the waters, but the generation of noxious odors in the
vicinity.
Vegetative cover, or the absence of it, at channel construction
sites will influence sediment generation. The reviewer will find
it helpful to estimate, in the area to be disturbed by construction,
acreages of different vegetative cover types which will be dis-
turbed or removed (e.g. forested land, grassland, sparsely vege-
tated areas, and urbanized areas). Techniques for estimating
sediment generation, under varying conditions and at sites with
differina_types_of_soil coyer have, been developed.29,30 Table IV-5
is illustrative of the influence of forest cover on erosion in
fifteen (15) sub-basins of the Potomac River.
Table IV-4. Comparative Sediment Yield From Bare
and Seeded Road Cut on the H. J. Andrews Experi-
mental Forest in Western Oregon
Condition
of Plot
Period of
Measurement
Sediment Yield
Kilograms/Hecta re
(Tons/Acre)
Bare
Seeded to Grass (1st year)
Seeded to Grass (2nd year)
9/58 to 9/59
9/59 to 9/60
9/60 to 9/61
23,370 (12.7)
7,728 ( 4.2)
4.232 ( 2.3)
Source: Wollum, A.G., "Grass Seeding as a Control for Roadbank
Erosion," USDA Forest Service Research Note 218, 5 pages
(1962).
Table IV-5. Influence of Forest Cover
On Control of Sediment Yield by Erosion
Percent of Land Area
With Forest Cover
Sediment Yield
Metric Tons/Sq.Km/Yr
(Tons/Sq.Mi/Yr)
20
40
60
80
100
140.00
70.00
31.50
15.75
7.70
(400)
(200)
( 90)
( 45)
( 22)
Source: Luss, Howard W. and Kenneth G. Rewbard, "Forest & Floods
in the Eastern U.S.," USDA Forest Service Research Paper,
NE-226, 1972, pp. 72-717"
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Distinctions Between Construction and Maintenance Activities.
Because of separable impacts the distinction between the construc-
tion phase and the operation/maintenance phase of a project is an
important one. Differentiation between the responsibilities of the
executing Federal agency (responsible for the EIS) and the local
sponsoring agency is statutorially though differently defined
by Federal agencies; even within the same Federal agency the
contractual obligations of that agency for separate projects may
vary. The EIS reviewer, however, need only be concerned with
these distinctions to the extent that the EIS specifies: 1) the
local sponsoring agency which will be a party to the operation/
maintenance agreement, and 2) defines the project-monitoring
program and operation/maintenance schedules. But and this should
be emphasized project operations and maintenance procedures
should be described in the EIS in the same detail as are installa-
tion (construction) procedures.
Initial considerations of impacts related to construction
and maintenance activities stem from the values placed on the pre-
project status of a proposed channelization i.e., whether the
channel (and its appurtenances) are to be installed in: 1) an un-
disturbed and natural watercourse (or portions thereof), 2) in a
previously modified watercourse, and/or 3) in areas where no defined
waterway had before existed. These impacts upon water quality and
hydrology, in a generalized but qualitatively significant sense,
are directly proportional to the lengths and widths of channel to
be re-aligned, modified, and/or newly built, for such dimensions
reflect the scale of land-disturbing activities.
The major impact problem or major pollutant from land-
disturbing activities is sediment generation and the subsequent
increase of turbidity in downstream waters. The reviewer's
prime focus, therefore, should be on those kinds of construction
and maintenance activities required by the project's definition
and purpose. These impacts are related to:
..the amount of land acreage to be cleared for the project's
construction;
..the area, volume, and other dimensions of all excavations
or fillings (i.e. berms, levees, and spoil disposal areas) ;
..the location of borrow pits, or quarries for rip-rap materials;
..the location of access roads, batch plants, stockpile yards,
etc. ;
..the specifications and details of road and bridge relocations
or requirements; and
..project schedule requirements for maintenance facilities or
procedures.
IV-2 6
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Aesthetic impacts, too, are related to these same scalable
values. But these impacts are more subjectively evaluated and there-
fore dependent upon such variables as the environmental setting of
the project (e.g. urbanized land, agricultural land, or wild land),
the aesthetic values of neighboring residents and others frequenting
the area, and upon such mitigative project elements as: landscape
plantings, artificial riffles, and the limitation of construction
activity to only one side of the channel.
The reviewer should find, in the EIS, sufficient details on
both the environmental setting of the project and the anticipated
construction and maintenance activities to be able, at least qual-
itatively, to appraise the environmental impacts of the various
stages of the proposed action.
Channel construction and/or maintenance usually begins with
such preliminary activities as clearing, grubbing and pest control.
Unwanted vegetation trees, shrubs, and grasses will be removed,
as will any existing structures found within the channel right-of-
way. Certainly the removal of rooted vegetation will bare soil
surfaces to accelerated erosion by wind and water, though the volumes
of surplus sediment thus generated will be less than during later
construction phases when excavation and levee-building may take
place.
The early stages of construction may also result in the genera-
tion and accumulation of miscellaneous pollutants, litter and
debris which could, if not removed, be transferred downstream when
water enters the channel. Impacts of this sort may be traceable to:
..wastes and spills of fuel and lubricants (from vehicles,
chainsaws, and stockpiles)
..applications of chemicals to reduce dust and stabilize
roadways,
..disposable containers and parts,
..scaffolding, discarded masonry forms, cleaning solvents, etc.,
..wastes from temporary sanitary facilities which are
improperly located or maintained.
Quantification of impacts due to the introduction of such pollu-
tants to both surface water and groundwater resources cannot be
precise, and the reviewer must be judgmental in determining whether
the EIS takes cognizance of their persistence, magnitude, and signifi-
cance (e.g., potential bioaccumulation).
The application of herbicides, insecticides and other target-
specific toxic chemicals (e.g., to reduce populations of black
flies) often accompanies the early stages of construction activity.
If pesticides are used, the reviewer should find in the EIS some
mention of the application rates of the intended chemicals and
TV- 2 7
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the expected impact of such practices, not only to the water
quality of the project and downstream areas, but to aquatic
and terrestrial ecosystems in the area. It is important that the
use and rate of application of such pesticides be consistent with
existing rules and regulations as promulgated by all agencies
with jurisdiction over the project site.
Significant impacts of early phases of project activities are
related to the denuding and compaction of soil. Denuded soil sur-
faces cause sediment to accumulate in the stream channel and degrade
water quality by increasing turbidity. And soil compaction
hinders the re-establishment of vegetation and decreases infiltration
potential, thereby increasing runoff. Though quantification of
these impacts is imprecise, the reviewer should critically note if
appropriate attention has been given to the following:
..Choice of equipment (e.g.: rubber-tired vehicles are less
soil-disturbing than cleated vehicles; cable-skidding of
logs by skidders bares less soil than does use of tractors)
..Timing of operations (e.g.: clearing during muddy seasons
induces aggravated erosion from runoff; removal of logs
skidded on snow causes less erosion than at other times)
..Roadway locations (e.g.: waterways-crossing should be kept
to a minimum to reduce erosion; sensitive soils and steep
slopes should be avoided; stabilized access roads should
be provided for all points where periodic clean-out opera-
tions are anticipated)
At the beginning of the major phase of construction activity
rough grading the generation of sediment will be exacerbated.
Draglines, shovels, graders, scrapers, skidders and other earth-
and log-moving equipment will remove sod, rooted vegetation, and/or
other layers which normally protect the subsoil layers from dis-
persal (i.e. accelerated erosion) by rainfall, running water, wind,
and gravity (on sloping surfaces). Erosion rates, by whatever
transport medium (wind, water, or gravity), can only be approximated
because of the variables involved. Sediment yield, however, is
inversely related to areal extent of vegetative cover. State-of-
the-art quantitative methods for erosion and sediment generation
can be found in the literature; several are summarized in EPA
reports issued under the authority of Section 304(e) of P.L. 92-
500.31
A number of predictive techniques for sediment production have
been proposed. These can be classified as: empirical, statistical,
or simulation methods; and they have application to the three
aspects of sediment involvement erosion, transport, and deposi-
tion. Empirical techniques are applicable to all three sediment-
related categories, whereas statistical and simulation methods have
been developed principally for transport and depositional processes.
(Summary discussions of all of these methods can be found in:
E.P.A.'s Methods for Identifying and Evaluating the Nature and Extent
of Non-Point Sources of Pollutants.52
-------
Both theoretical and regionally empirical formulae (based on
local geological, soil and meteorological conditions) are appli-
cable to the analysis of aeolian and fluid systems and their
effect upon erosion of sediments of different types. (Earlier
referenced publications and articles are sources for these formu-
lae. )33,34,35 The reviewer is advised to exercise the judgment
of experience in determining whether sufficiently critical and
analytical effort and expertise have been devoted in the EIS
to quantification of sediment generation and subsequent turbidity
effects.
It is important that the reviewer be informed about the
statutory limitations on construction-induced sediment loads
prescribed by state water quality agencies. Such limitations are
expressed in water quality criteria for turbidity, for example,
where they are usually measured in Jackson Turbidity units (JTU's);
they are usually established for specific stream segments and are
often expressed as maximum increases allowable within specified
periods.
Impacts induced by turbidity in water bodies and traceable
to construction/maintenance activities may include any of the
following:
..inhibiting the survival or degrading the habitat of
pelagic and benthic organisms,
..decreasing the rate of photosynthesis and production of
aquatic vegetation,
..increasing surface water temperatures (by increased ab-
sorption of solar radiation), and
..increasing the concentration, in areas of sediment accumu-
lation (e.g. lakes, reservoirs, deltas, shoals, etc.), of
pesticide residues and other chemicals absorbed by sediment
particles and oil films.
In addition to accelerating erosion the activities of rough
grading will lead to compaction of some soils and sediment, especially
on clayey and organic sediments with high liquid limits. Soil
compressibility can be qualitatively assessed by reference to a
number of manuals.36 The inhibited re-establishment of grasses
and other vegetation intended to serve as sediment-decreasing ele-
ments may adversely effect downstream water quality. The reviewer
should note the possibility of this occurrence. The application
of fertilizers (especially nitrogen and phosphorus) on revegetated
areas to accelerate bank stabilization will, on the other hand,
have a potentially adverse effect upon water quality.
Accelerated erosion by wind and surface runoff on denuded slopes
and surfaces at channel construction sites, as has been implied/
can be mitigated by both vegetative cover and non-vegetative cover.
(Further discussion of these techniques will be found in Section
IV.A.3.)
IV-2 9
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The following generalizations are important as guidelines in
the review of impacts traceable to construction and maintenance
activities. Timing of construction and maintenance activities, as
well as their frequency, will have an influence upon the severity
of environmental impacts. The reviewer should be aware of seasonal
meteorological changes (rainfall patterns, runoff characteristics,
etc.) and land-use influences in assessing the adequacy of the
EIS discussion on these points. Construction impacts on project-
related environmental parameters are a "one-time" occurrence;
maintenance activities, on the other hand, are implicitly considered
to be recurring. The improvement of hydraulic efficiency by
periodic clearing and cleaning-out of the channel will be accomplished
only at the expense of some downstream effects on water quality.
The choice of emphasis, therefore, between improved project functions
(i.e. hydraulic efficiency) and amelioration of the impacts there-
by induced (i.e. degraded downstream water quality) is one involving
the same "tradeoff rationale" as that supporting the decision
to construct the channel in the first place. The evaluation
of net benefits resulting from the consideration of conflicting
goals therefore must be as clearly stated in the EIS as possible
both in regard to initiation of the project and in its main-
tenance.
It is important that schedules for inspections and procedures
for monitoring operations of the channel and its adjunct elements
(drains, culverts, etc.) be included in the EIS. Malfunction of
drains, accumulation of debris at points of channel constriction
(at bridges, culverts, drop structures, etc.), shoaling, and
bank-slumping or undercutting are examples of the sorts of problems
which should be anticipated, reported, and remedied quickly in order
to minimize impacts to downstream water quality and hydraulic
efficiency. Recurrent operations, such as the periodic removal of
vegetation growing on side slopes and in the channel, should also
be anticipated.and a schedule for such work should be estimated
in the EIS.
Changes in Groundwater jjevels. The reviewer's task of identi-
fying sources of impacts upon groundwater, though not a simple one,
is qreatly aided by published hydrologic studies of watersheds.
These are available, in areas where they exist, from the U.S.
Geological Survey, and from state geological surveys. Engineering
studies of municipal water supplies especially those derived
from wells are an additional source of information on ground-
water conditions in a project area.
The United States can be divided into four regions and at
least 24 sub-regions (see Figure IV-3) with regard to groundwater
characteristics and conditions. The four regions are:
(1) the East-Central "old rock" region,
(2) the Atlantic and Gulf Coastal Plain region,
(3) the Great Plains region, and
(4) the Western Mountain region.
IV-30
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To the extent that generalizations apply these areas
especially the sub-regions each contain rock types as well as
morphological and meteorological conditions which are relatively
homogeneous. Channel construction within each of these different
regions may be expected to encounter generally similar groundwater
conditions.
Figure IV-3. Map of the United States
Showing the Four Major Groundwater Provinces
Source: Meinzer, O.E., Hydrology, Dover Publications, 1942, p. 440.
Influences upon groundwater levels such as those caused by:
rates of precipitation, volumes of surface waters, infiltration
rates, pumped withdrawal rates, vegetation withdrawals, etc.
with or without the presence of man-made channels can only be
predicted if local meteorological (supply), geological (intake),
and hydrological (transport) conditions are known. Snow-melt and
rain, for example, will not recharge groundwater reserves until under-
lying frozen ground melts and becomes permeable. And only that
rainfall which occurs after a deficiency in soil moisture has been
satisfied will recharge groundwater reserves. Moreover, and in
addition to temporal variations, recharge potential differs still
more from place to place because of geological differences in
stratigraphic, topographic, and structural conditions.37 channels,
it is agreed, introduce new pressure-potential surfaces and new
sources of entry and exit for groundwater producing an imbalance
IV-31
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in the preproject ground and surface water system and leading
to new equilibrium conditions.
The flow of groundwater, following Darcy's Law, is calculated
from: 1) average sediment (or rock) porosity, 2) the cross-
sectional area through which flow occurs, and 3) the average vel-
ocity of flow (derived from Darcy's fundamental equation which
assumes a measurement of hydraulic gradient, and varies from one
foot/years to 10's of feet/day). Most, but not all, groundwater
movement is parallel to the bedding of permeable strata; it may
move up the dip of strata as well as down the dip. In areas of
artesian pressure the piezometric surface (coincident with the
hydraulic head) of an aquifer is above the land surface. Contour
maps of the piezometric surface of an aquifer will permit deduc-
tions about the horizontal directions of groundwater movement;
vertical groundwater movements between aquifers/ sometimes re-
sulting in recharge of one aquifer by another, depend upon dif-
ferences in the hydraulic heads of the two aquifer systems.
The coefficients of "transmissibility" or of "permeability",
terms applied to the permeability of a water bearing aquifer,
can be measured in the laboratory or in the field and thereafter
applied to the several methods and formulae used to model ground-
water movement. (The above coefficients are related terms, dif-
fering only in the dimensions defining their measurement.) Na-
tural aquifer materials have coefficients of permeability which
generally vary from 10 to 5,000. Thus in the formulae:
v = ~Y- where v = velocity of water flow
through an aquifer
Q = volume of water flow
or h = hydraulic head
1 = length of flow to be
measured
i = hydraulic gradient
A = cross section area of
aquifer
and P = coefficient of permeability
it can be seen that both velocity and volume of groundwater
flow bear a direct relationship to the permeability of the aquifer
being studied.
Commonly used methods and data that have application to
groundwater recharge studies in general include:
..lysimeter tests (to observe infiltration and percolation
rates);
..precipitation records/ from which runoff and evaporation
losses (i.e. amounts not infiltrating the subsoil) may be
subtracted;
IV-3 2
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..periodic tests of soil-moisture conditions below the in-
fluence of vegetation;
..charts of water table fluctuations in wells in equili-
brium or while being pumped combined with calculations
of "specific yield" for relevant aquifers (i.e., calcula-
tions of that specific volume of groundwater which is not
held by molecular attraction in the interstices of satu-
rated rock and the determination thereby of that volume
available for yield or exploitation);
..and measurements of the decrease in the flow of influent
streams (or unlined channels) between gaging stations -
a measured loss which is theoretically equal to the amount
of water added to (or recharging) groundwater reserves -
after losses due to evapotranspiration have been subtracted.
The last two techniques on the above list are those most com-
monly used for determining the excess of recharge over discharge of
groundwater volumes.
Channels are man-made intrusions, or interruptions, in the
natural hydrologic cycle of groundwater and surface water systems,
The water table responds three-dimensionally to changes caused
by such disturbances of hydraulic gradients; lateral components
of these gradients develop and the directions of groundwater
movement change. And because channels, unlike wells, are not
points on a contoured pressure surface, but are instead complex
surfaces of a pressure system independent of and intersecting
those of the natural groundwater system, the interaction between
the two (i.e. the pre-project hydraulic system and the system
which is in a state of nonequilibrium induced by flow in the
channel) requires complex mathematical analysis and approximation,
(Several of these analytical techniques are available as refer-
ences.) 38,39,40,41
It is unlikely, however, that the EIS reviewer will find
technical analyses of groundwater conditions in the EIS document.
But, results of such analyses, which make possible predicted
changes in groundwater levels, may be included in the EIS, as
well as references to studies supporting these findings. In
cases where groundwater impacts are judged to be critical, the
reviewer in regional EPA offices should contact EPA headquarters
for assistance in evaluating both the studies undertaken and the
conclusions reached.
IV.A.3. Assessment of Impacts
An assessment of hydrology and water quality impacts should
relate identified and quantified impacts to appropriate environ-
mental standards and criteria and also determine the need,
IV-33
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applicability, and effectiveness of alternative mitigative
techniques. Alternatives to the proposed project in terms of
project scope, location, or alternative means of meeting water
resource objectives should be addressed in the EIS. In many
cases the reviewer will not be able to relate specific predicted
values for various water quality parameters to the applicable
numerical criteria. Instead the assessment may have to be some-
what judgmental, basing assessments on the scope of the project
and the subjective characterizations of the affected resources
in order to be able to estimate whether water quality standard:.
will be violated or whether impacts of an unacceptably high
level will result from project implementation.
Both direct inputs of pollutants due to construction, TIU-. i - * o -
nance, or land use changes and indirect effects on assimilative
capacity and pollutant transport should be evaluated.
Water Quality Standards. Criteria and standards of water
quality are essentially those established by state environmental
agencies. The categorization, specificity, comprehensiveness,
and rules for exceptions to these statutorially defined standards
vary appreciably from one state to another across the nation.
Most states have established minimal criteria for all waters
defining, in broad terms, universally objectionable pollutants
which may be found in public waters. They include:
sludge, residues, and other settleable materials - in
amounts that are unsightly, create odors, or otherwise
degrade water quality;
floating debris - that which is waste-derived and in
amounts creating unsightly conditions and impairing
normal water usage;
material attributable to waste-generating activities - in
amounts creating unsightly conditions, odors, or otherwise
degrading water quality;
oils and greases - in visible amounts on water surfaces;
and toxic, corrosive or deleterious materials - in amounts
harmful to human or biological uses of water and otherwise
interfering with water usage.
Criteria are specified for relevant constituents - depending,
in most instances, on: 1) an adopted classification of public
waters (in terms of named bodies of water or reaches of a stream
OJ river), and 2) existing and projected uses of those waters
(e.g., raw water supply, recreation, aquatic life, etc.). Such
criteria are defined as maximum values allowable, for degrading
IV-3 4
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constituents - or minimum values required, for beneficial
constituents (e.g., dissolved oxygen), and they normally state
the average, or mean values not to be exceeded by a given per-
centage of the samples taken over a specified period of time.
Thus, because criteria are subject to a wide range of specifi-
cations (even within a state), the assessment of water quality
parameters must necessarily be in the context of local regula-
t i ons.
A list of project-related activities which may occur during
construction, operation, and maintenance phases follows:
Land-Pi sturbing Activities Structure-Building Activities
- clearing and grubbing
- levee-building
- excavation
- sediment and debris
removal
- bank stabilization
- machine operation
Vegetation-Removal
- brush-cutting and mowing
- tree-felling
- grazing
- in-channel or channel-bank
revetments
- masonry and grouting
- bridge erection
- machine operation
Miscellaneous
- sanitary waste generation
- pesticide application
Many of the activities listed above will cause impacts to
the same water quality parameters, though some more severely
than others. It is not of practical aid to the reviewer, there-
fore, to associate specific water quality parameters or consti-
tuents with the separable impact-inducing activities of a channel
project.
Table IV-6 lists most of those constituents which are rele-
vant and critically appraised in channel projects. As earlier
noted the constituent criteria are not universally applicable to
all U.S. waters - or even to all waters within a state. There-
fore, for the reviewer's guidance, only a range of significance
is indicated, values below which (or above, in the cases of min-
imum standards), if anticipated, should arouse the critical con-
corn of the reviewer. Listed also in Table IV-6 are those water-
use categories usually found in conjunction with stream channel-
ization projects and to which the criteria, in general, are ap-
plicable. The table should not be construed as interpretive of
any state's established standards but simply as a convenient
reference; applicable criteria should be sought by the EIS re-
viewer from the appropriate water quality agency in the project
area.
IV-35
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Table IV-6. Average Range of Water Quality Criteria*
Adopted by States for Selected Constituents and Generalized Water-Use Categories
nstituents
Public Water
Supply Intake
Wildlife and
Aquatic Life
Body Contact
Recreation
Livestock &
Irrigation
ssolved Gases
Dissolved Oxygen
4-5 mg/1 or
60-75% saturation
4-5 mg/1 - warm-
water fish, 5-7
mg/1 coldwater fish*
3 mg/1
ysical-Biological
Turbidity
Clarity
Fecal Coliform
25-50 JTU above
background or base
flow values
1000-2000/100 ml
25-50 JTU, warm-
water fish, 10 JTU
coldwater fish*
4-feet visibility
of secchi disk*
100-200/100 ml*
1000/100 ml
kalinity
pH (or alkalinity
as CaC03)
amical Constituents
Chloride
Sulfate
T.D.S.
Mercury
Lead
Zinc
6.0 - 9.0
6.0 - 9.0'
(20 mg/1)
250-500
100-500
mg/1*
mg/1*
250-500 mg/1
.0005-.005 mg/1*
.05-1.0 mg/1*
.5-5.0 mg/1*
sterisk indicates water use for which constituent is most critical. Data on organic compounds and
ssticides not listed because of diversity of specifications in state regulations.
JRCES: Annotated Compendium of "State Water Laws," appearing in: Environment Reporter, Bureau of
National Affairs, Washington, D.C.,1973-76; U.S. EPA, Proposed Criteria for Water Quality, Vol.
Oct. 1973; National Academy of Sciences & National Academy of Engineering, Environmental Studi<
Board, Water Quality Criteria-1972, A Report of the Committee on Water Quality Criteria,
Washington,D.C., March 1973, (EPA-R3-73-033).
-------
On the single but important subject of contamination by pes-
ticides and/or petroleum products the reviewer is advised that
the EIS should cite not only those standards applicable to water
quality but to the marketability or acceptability of fish, shell-
fish, and other aquatic products from an impacted area. Aqua-
tic organisms, in particular, are well known for their ability to
magnify the taste of petroleum in their flesh and to concentrate
levels of pollutants which are toxic to higher orders of life.
Changes in Hydraulic Parameters. The importance of the hydro-
logic and water quality impacts caused by changing the alignment,
dimensions, gradient, or bottom composition of a watercourse must
be assessed in the context of the land and water uses within,
upstream, and downstream from the proposed project area. In-
formation contained in Proposed Criteria for Water Quality, Vol-
ume 1,42 should be used in conjunction with state water quality
standards as primary references on the acceptable levels of vari-
ous constituents for major water uses. In addition, the proposed
project must be reviewed in light of water quality management
programs initiated under the 1972 FWPCA Amendments, particularly
areawide waste treatment management planning and the state basin
planning program.
If the review indicates the likelihood that assimilative
capacity in the proposed channel will be decreased due to removal
of riffle areas or channel realignment, existing and probable
waste discharges and water uses will influence the importance
of the impacts. On a headwater stream that does not receive any
point source wastewater discharges and is protected under the
state's antidegradation policy, the water quality implications of
reduced assimilative capacity may not be significant. In water-
sheds where numerous pollution sources exist, however, any re-
duction in the purification ability of a stream may jeopardize
the attainment of water quality standards. Thus, an assessment
has to include consideration of present and probable future water
quality in order to identify potential problems. Downstream
water uses are equally relevant. The increased hydraulic effi-
ciency of a channel will normally cause more rapid transport of
water and associated pollutants to downstream sections. In the
case of nonconservative constituents for which assimilation is
time-dependent, such as biochemical oxygen demand/dissolved
oxygen and fecal bacteria, water quality degradation may persist
further downstream. If erosion and turbidity in the channelized
reach have been identified as probable impacts, increased sedi-
ment transport to and deposition in downstream reaches may also
occur. When these kinds of problems are expected, the reviewer
should base his assessment on the nature of stream uses below
the proposed project, paying particular attention to water supply
and recreation which may be adversely affected by water quality
impacts of channelization.
IV-37
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Regarding effects on downstream flood potential caused by
channelization, the reviewer should ensure that the impacts have
been addressed and that the conclusions reached in the EIS are
substantiated by adequate hydrological analyses, as discussed
in Section IV.A.2. A basic concern is that channelization in
an upstream portion of a watershed may contribute to the need
for structural flood protection measures further downstream and
cumulative impacts on stream ecosystems.
Numerous mitigative measures and alternatives may be applic-
able to channelization to reduce hydrologic and water quality
impacts. Table IV-7 describes several techniques that may aid in
reducing the impacts of channelization. They may be necessary
for engineering or channel stability reasons or used for miti-
gating identified water quality impacts. In either case, the
effects of a particular mitigative technique may not always be
entirely beneficial. Possible drawbacks of various impact abate-
ment methods are also included in the table.
The key to minimizing water quality, ecological, and other
environmental impacts is the preservation or restoration of
diversity in the channel, whether in flow velocity, shape, sub-
strate, or other characteristics. The need for and use of impact-
mitigating features within a proposed channel should ordinarily
be viewed with consideration of the length of channel alteration,
the value of the water resource for fishing, recreation, or other
uses, and assessment of the significance of expected impacts.
When assessing mitigative measures proposed in the EIS, the re-
viewer should be cognizant of the overall effects, both bene-
ficial and adverse, of the particular modifications and make
sure they have been addressed. Incorporation of facilities or
techniques described in Table IV-7 into the design will usually
increase project costs. Therefore, the nature of the impacts as
quantified in the EIS or as perceived by the reviewer should be
cited to support comments on possible ways of minimizing adverse
effects.
Construction of ancillary facilities to alter water depths,
velocity, or sediment transport in a channel, such as grade con-
trol structures, low-level weirs, pools and riffles, or sediment
basins, may help to reduce water quality problems by decreasing
sediment loads in and downstream from the channel and perhaps
increasing the assimilative capacity of the channelized section.
However, impacts on aquatic habitat and migratory species may be
associated with these measures and have to be assessed as well.
A variety of materials, ranging from vegetation to smooth
concrete can be used for protecting the channel bottom and banks.
Control of scouring and erosion is essential in those parts of
a channel where soils cannot withstand the design velocities.
Grade control structures can be used in combination with direct
bank and channel protective measures. Use of concrete lining,
IV-38
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Table IV-7. Mitigative HeasureE and Probable Effects
Mitigative Measures
Applicable Situations
Problems to be Mitigated and
Other Probable Effects
Grade Control Structures
Drop Spillway
Chute
Rock-armored sections
Cascade structures
Low-Level Weirs, or Dams
(Concrete, rock or
gabion)
Pool-riffle Sequences
(Vertical Meanders)
Sediment and Debris
Basins in Channel
One-sided Channel
Construction
Change in Channel
Cross-section
Random Rocks
Wing or "V" Deflectors
For channels with excessive
slopes or those for which so.il
and stability analyses suggest
excessive erosion under design
flow condition. (Especially
cut-offs or channel realignment.)
Drop spillways may not be feas-
ible on larger streams.
For widened or otherwise alter-
ed channels where water depths
would be reduced substantially
especially those in subhumid
or arid regions.
Reduction of potential for
channel erosion.
Increase in water depth.
Increase in velocity diversity.
For channels wliore natural
pools and riffles would be
modified or eliminated by con-
struction or where addition of
such variations would be de-
sirable. Dcsiqri mriy take ad-
vantaqe of varying credibility
of soils within channel align-
ment (e.g. riffles in erosion-
resistant stretches).
For channels subjected to sub-
stantial inputn of suspended
or bcdload loilimcnt-; or debris
from upstream or in-channcl
sources. Upstream impoundments
(existing or proposed) may also
trap sediments.
For channels that will follow
existing alignment, where exist-
ing banks and riparian vegeta-
tion are stable, or where land
uses needing protection or
drainage are concentrated on
one side of a channel.
Creation of aquatic habitat.
Improvement of groundwator
recharge.
Inhibition of terrestrial
(phreatophytc) vegetation
growth, perhaps reducing
maintenance requirements.
Collection of sediment and de-
bris (which) may negate val-
ue of aquatic habitat crea-
tion .
Possible hindrance of upstream
fish migration.
Increase in channel stability.
Protection against meander
development.
Reduction of sediment from
channel and bank erosion.
Enchanccmont of rcaoration.
Creation of greater substrate,
velocity, and depth diversity
Reduction of sediment trans-
port to downstream reaches.
Requirements for periodic
maintenance md disposal
of sediments.
Provision of rcutiny areas
and shelter for fish.
Possible substratum instabil-
ity unsuitable for bcnthic
colonization.
Reduction of loss of riparian
vegetation and shade cover.
Reduction of amount of
excavated material requir-
ing disposal.
Preservation of aquatic
habitat and cover.
For most channels, within limits Reduction of loss of riparian
of hydraulic and soil constraints. vegetation and shade cover.
Adjacent land values and uses Reduction of amount of ex-
must be considered. cavated material requiring
disposal.
For any channel.
For most channels.
Increase in turbulence and
reaeration at lower flows.
Provision of stable and
greater area of substrate
for benthic organisms.
Provision of cover and refuge
from high water velocities
for fish.
Protection of bank from erosion
(particularly on curves).
Provision of cover and refuge
from high water velocities
for fish.
Introduction of more diverse
velocity patterns.
Cause scouring of holes pro-
viding deeper water and
cover.
IV-39
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grouted rip-rap, or other smooth, homogeneous materials is not
desirable from a water quality standpoint, because such a sub-
strate will not be conducive to maintaining an abundance and
diversity of benthic organisms or to inducing significant tur-
bulence and reaeration. Linings of this type are normally
necessary and feasible only for channels traversing heavily
developed areas where adjacent land is either unavailable or too
costly for construction of a trapezoidal-shaped earth channel.
Although such linings will eliminate or significantly reduce
channel erosion, it is important that their aesthetic and water
quality implications be brought out in the EIS. In addition,
impervious materials used for channel and bank protection will
prevent groundwater recharge and bank storage, which may be an
important consideration if the channel is located in an aquifer
recharge area or if groundwater contributes substantially to the
baseflow of the existing stream.
All channel banks should be protected from erosion. Herba-
ceous cover that can be maintained regularly by mowing is one of
the most common stabilization measures, as discussed in greater
detail below. Well-graded coarse stone or rock rip-rap will pro-
vide a high degree of erosion resistance in steep channel sec-
tions through erodible soils, and is often used for a distance
upstream and downstream from channel structures or at transitions.
A gravel and cobble bottom would cause turbulence and vertical
mixing beneficial to reaeration; however, because the nature of
the channel bottom depends on the water velocity and sedimenta-
tion characteristics, the probable effects of channel aging on
the ultimate bottom composition of rip-rapped or gravel-armored
reaches should be addressed. It is possible, for instance, that
fine-grained silts and clays or other sediments will, over a
period of time, cover and reduce the roughness of the channel
bed. These changes would have ecological as well as water quality
significance.
Changes in Watershed Land Use. The influences of watershed
land uses on hydrology and water quality can be great and are
often more important than the direct effects of channelization.
The major issues are not only the hydrologic/water quality con-
cerns discussed herein but they also range to basic ecological
questions in the regional or national perspective concerning
drainage of wetlands, conversion of bottomland hardwood forests
to other uses, development of natural flood plains, and cumula-
tive impacts of all resource development activities, discussed
further in Section IV.C.
With respect to the relationship of hydrology and land use,
the reviewer should assess the degree that trends in land use,
in both the project area and the watershed, have been sufficiently
described, and whether hydrologic data and predictions used for
channel design have been modified to include probable effects of
land use changes on runoff and peak flows. Effects of urbanization,
TT V A f\
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silviculture, agriculture, drainage, and upstream flood storage
capacity are of primary interest, in particular on smaller water-
sheds where hydrologic response may have a significant influence
on channel design and operation.
Water quality/land use interactions should be assessed pri-
marily for the project area of influence and secondarily for
the watershed in general. Salient points in the review include
the adequacy and completeness of:
- existing and projected land use descriptions in project
area of influence;
- descriptions of existing and projected fertilizer, pes-
ticide and other pollutant loads in project area of
influence;
- discussion of consistency of project-related land uses and
pollutant loads with applicable plans and planning pro-
grams (208 areawide waste treatment management planning,
303(e) basin planning, and others);
- conclusions concerning effectiveness of any land treat-
ment measures in reducing erosion and introduction of
sediment to the watershed and channel;
- conclusions concerning the overall effect of the channel
and related land uses on water quality.
Construction and Maintenance Activities. Construction and
maintenance activities, by their very nature, will produce hydro-
logical and water quality impacts. These impacts will occur both
in the channel (at the site and also upstream and downstream from
it) and adjacent to the channel. Tree and vegetation removal,
excavation, the building of levees and the disposal of spoil,
the installation of outlets, spillways, culverts, etc., and the
construction of travelways and access roads adjacent to the
channel typify those activities which should be addressed in
the review process.
The purposes of assessing these impacts are:
(1) To relate all unavoidable impacts to appropriate envi-
ronmental standards and criteria,
(2) to determine the significance of identified and quanti-
fied impacts, and
(3) to assure the use of feasible methods for avoiding or
mitigating pollution stemming from construction and
maintenance.
IV-41
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The water quality standards and criteria applicable to con-
struction and maintenance activities of channelization are the
same as those applicable to other potentially degrading activi-
ties in waterways. (See Table IV-6). The sole distinction in
applying these standards is that, because of the episodic timing
and nature of construction and maintenance activities, a degree
of flexibilityor even an exceptionmay be incorporated in the
state-specified criteria for certain impacting activities. Ari-
zona, for example, exempts from water quality standards those
impacts resulting from the mechanical maintenance of irrigation
systems; Vermont makes an exception to its criterion for tur-
bidity if a temporary pollution permit or an executive order has
previously been obtained; and other states specify that measur-
able turbidity standards may be either absolute (as defined by
Jackson Turbidity Units), or above background or base flow con-
ditions, or averaged over specified time periods. It is important
therefore that the review of such impacts not only be within the
context of the appropriate and applicable water quality criteria
but also be coordinated with the agencies having jurisdictional
authority in the project area.
The anticipation of pollution expected to result from con-
struction and maintenance is more certain than is the quantifi-
cation of the resultant impacts. The reviewer should be informed
not only of the location, magnitude and scope of the activities
proposed, but also of the instream criteria and standards which
are relevant. The reviewer will then have to make a before-the-
fact judgment on the anticipated severity or criticality of anti-
cipated impacts. Such judgments should be, if the occasion war-
rants, translated into appropriate comments in the review of the
EIS. Of special concern, for example, may be the impact of sedi-
ment generation and resultant turbidity on a coldwater fishery
for such sensitive species as smallmouth bass, trout, and other
salmonids.
An important reason for assessing impacts on water quality
during the construction and maintenance phases of a project is
to assure the use of all feasible methods for reducing or avoid-
ing pollution with mitigating or alternative measures. The
scheduling and timing of operations, for example, or the location
of access facilities or temporary sediment basins may be among
the mitigating measures which could or should be proposed.
(Further discussion of impact-reducing measures will be found in
subsections on this topic which follow.)
Potential Mitigating Measures During Construction and Main-
tenance Operations. Alternatives to be discussed in the sections
following are applicable only to the functional and separable
elements of a channel project and not to the concept of channeli-
zation in its entirety. Alternatives, in the latter sense, as
they might be proposed for a flood reduction or drainage project,
are briefly discussed in Chapter II.
IV-4 2
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Though the reviewer is not expected to assess the specific
hydraulic design features of a project, the provision of such
features to control channel stability - or the absence of them -
should be apparent in project specifications. Such provisions
may include features:
- to increase capacity of flow through specific reaches,
- to maintain optimum channel depth where there is a tendency
for the channel to degrade or aggrade,
- and to prevent bank erosion.
The erection of structures in or alongside the channel is
undertaken not only to prevent destabilizing the banks but to
guide channel flow so that sediment deposition, for example,
occurs in designated areas.
Bank erosion may be prevented by the placement, at critical
points, of revetments of various designs. Prevention may also
be accomplished by controlling, with upstream impounding struc-
tures and release schedules (e.g., at sediment basins, sills,
weirs, dams, drop basins, etc.), an appropriate sediment volume-
to-capacity ratio in critical channel reaches. The control of
channel flow and alignment is usually undertaken with "training
structures" (e.g., groins, pile dikes, jacks, etc.) at critical
deflecting points where channel scour, for example, will aid in
sediment transport and thus maintain hydraulic efficiency.
The assessment of project features designed to insure channel
stability is relevant to reduction of sediment generation and
therefore to both the construction and maintenance phases of a
project. But because the EIS does not usually include pertinent
design analyses the reviewer's judgment and comments on the ade-
quacy of the treatment of these topics in the EIS must be criti-
cally inferential rather than specific.
It is also important that consideration be given in the review
process to those aspects of a project which may be remedial in
nature - the repair of banks and scour holes, for example, or
the accommodation within banks of flows in excess of an earlier
designed capacity (e.g., irrigation return flows added to channel
volumes subsequent to the project's initiation). In such cases
the reviewer should note the possibility that proposed remedies
may simply shift problems to other areas. Measures taken to pre-
vent scour, for example, may subsequently cause the channelized
stream to erode laterally; or the construction of a straightened
channel (to replace a meander curve) may cause the accumulation
of sediments at its downstream end without, at the same time, pro-
viding sufficient stream capacity beyond that point to transfer
these sediments to a more appropriate area of deposition.
IV-4 3
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The exposure of denuded and disturbed soils (on berms, spoil
banks, or the banks of unlined channels) and the resultant in-
crease in erodibility, especially during seasons of high inten-
sity rainfall, can be mitigated by the prompt planting of vege-
tation on these areas or by the application of several kinds of
nonvegetative mulches to retard runoff-produced erosion. On
berms, spoil areas, and banks where grasses requiring periodic
mowing are to be established, the reviewer should be aware that
such maintenance is not feasible on slopes in excess of 3:1.
Seeding or mulch application during construction should, moreover,
be scheduled on a continuing basis rather than at the end of all
project construction activity.
The reviewer should also note the appropriateness of vegeta-
tional material selected for bank stabilization in terms of its
germination period (in the case of herbs and grasses) and the
inclusion of perennial species, as well as its adaptability to
site conditions. The selection of specific materials will
usually be governed by local climatic conditions; county agricul-
tural agents are sources of information on such subjects.
Soil conditioning by physical compaction (e.g., sheep's-foot
roller) or the replacement of a loose soil with one more easily
compacted may be an alternative to mulching in some areas.
Scarification of slopes with horizontal furrows, or the con-
struction of berms, terraces, or diversion channels (on the tops
of channel cuts) may be alternative or supplemental to the appli-
cation of runoff-retarding materials during construction and main-
tenance operations.
Removal of bankside vegetation during construction or main-
tenance phases may be justified in terms of increased hydraulic
efficiency but this activity may also have several adverse effects,
one of which may be that of destabilizing soil in the area. In
some cases vegetation may overhang the channel thus shielding
the water from solar radiation and thus restricting water temper-
ature increases and thereby maintaining high levels of dissolved
oxygen. Bankside vegetation, in addition, may enhance terres-
trial and aquatic habitats. The reviewer should appraise project
values in light of the possibility that these conflicting impacts
can both stem from vegetation removal. (See Sections IV.B. and
IV.C.)
Rodent burrows in channel banks and berms may impair the hy-
draulic functioning of these features of the project. Discourage-
ment of such animal activities may have to be a part of maintenance
procedures and should probably be accomplished physically (e.g.,
blocking burrows with stones, trapping or shooting the animals)
rather than with poisons which may find their way into the water
system.
IV-4 4
-------
Entrance of cattle and other animals into channels, culverts,
etc. should be carefully controlled. In some grassed channels
for intermittent and predictable flows grazing animals may help
to control vegetation and thus provide inexpensive maintenance.
But channel banks steeper than 2:1 will deteriorate from animal
traffic as will water-saturated banks of even gentler slopes.
The reviewer should note from the description of existing and pro-
jected land uses adjoining the project the potential problems
associated with unrestricted movement of livestock.
The reviewer should be particularly concerned with points of
channel curvature, or other changes in alignment, to insure that
undercutting and other flow-induced and impinging erosive forces
will not cause either slumping or sediment deposition at these
points before as well as after the project is placed in operation.
In addition to nonstructural measures it is common to also find
structural measures employed at these critical points along a
channel. Such measures may include, in channels both lined and
unlined, revetments of various design and combinations -- pilings,
bulkheads, permeable jetties, retards, gabions, emplaced rocks,
riprap, skeletal frames, etc. The reviewer should determine
that the points of vulnerability to erosive channel forces have
been identified and that the specifications of project design pro-
vide reasonable (i.e., efficient and economical) remedial measures
at these points.
It is important that the assessment of those measures pro-
posed to insure bank stabilization be made in the context of the
water quality standards established for the project area and for
an appropriate length of stream upstream and downstream from con-
struction sites. These criteria will include standards for: tur-
bidity, pH (occasioned, for example, by the use of some acidic
masonry construction materials in or adjacent to the channel),
nutrients (particularly N & P from fertilizers applied to vegetative
cover planted on exposed soils), pesticides and other toxic chemi-
cals, and solid wastes of various kinds.
The maintenance of hydraulic efficiency and water quality
requires that the accumulation of sediment and debris in the channel
be held to a minimum and that provision for its removal be incor-
porated in routine maintenance procedures.
The installation of basins, spillways, culverts, traps, weirs,
and other grade-control structures may be incorporated in the pro-
ject in order to decrease channel gradient, thereby protecting
channel materials from high velocity and erosive forces. At the
same time these structures will entrap and reduce sediment loads
(both in suspension and traction) moving down the channel; they
may also have the adverse effect of accumulating flood-borne
debris and trash.
It is important that project review assess the adequacy of these
structures as to type and scale, and their compatibility with site
IV-4 5
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configuration (i.e., channel width, maximum anticipated hydraulic
head and capacity, etc.). Maintenance procedures should, for example,
require the removal during or after floods of log jams at bridges
and other points of channel constriction. And cluttered trash
racks in front of culverts and spillways may cause the channel
waters to cover areas not intended to be flooded or to erode un-
protected areas beside wing walls. The reviewer is not expected
to review hydraulic engineering calculations, but he should compare
the range of channel flows anticipated with the dimensions of the
project elements so as to assess their effectiveness under opera-
tional conditions. It is important also to estimate the dimensions
of pools and basins which may form as a result of unintended reten-
tion of waters at these structures.
The reviewer may find that sediment basins (so defined in
project designs) have adjunct functions as well. These may include:
water aeration (as part of a pool-and-riffle section of the channel),
improvement to fish or wildlife habitat, retarding vegetation growth
in the channel, and/or aesthetic improvement (to relieve the mono-
tony of an artificial channel). In these cases the adjunct benefits
should be added to those derived from sediment removal and recog-
nized as enhancements in the impact assessment.
Scheduled removal of sediment, debris and trash from the
channel and inlets is a project maintenance requirement. The pro-
vision for enforcement of safety regulations or for physical
measures (e.g. fences, grills, cattle guards, flood gates, etc.)
restricting the entry or encroachment of humans, domestic animals,
or rodents into the environmentally sensitive or dangerous areas
of the channel, or appurtenances thereto, may also be a routine
requirement of those charged with maintenance.
The flow of some channels is seasonal and the schedule for
removal of accumulated materials can often be anticipated. And
in channels which pass through urban areas there is often a
predictable rate of accumulation of trash and rubbish which is not
only unsightly and odor-producing but degrading to water quality.
Maintenance procedures to minimize such impacts should be specified
in the EIS.
Project design and maintenance procedures outlined in the
EIS should encompass not only regularly scheduled monitoring surveys
of the project's functions but also provisions for repair and periodic
cleanout of the sediment-and debris-accumulating structures and
the convenient access for equipment to such locations.
Measures are frequently taken to intercept runoff across
bared soil and so to diminish the contribution of sediment to
waterways. They may also serve solely to collect flows emanating
from diverse sources and to prevent ponding of such waters. Such
measures, by restricting runoff flows from proscribed areas (con-
struction sites, unstable soils, polluted areas, etc.) will divert
flows to waterways, chutes, drains, culverts, and other places
where their flow can be controlled.
IV-46
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Interceptors are effective during construction and operational
phases of a project. They may be either temporary (e.g. berms)
or permanent installations (e.g., subsurface tiles or drains); they
may intercept surface and/or subsurface flows. Seep or spring
lines and breaks in slope are typical sites chosen for the place-
ment of interceptors.
The comprehensive review of such measures and their effective-
ness requires that thexreviewer have information about the local drain-
age patterns, both surface and subsurface. Maps of regional and
project topography as well as maps showing groundwater flow
directions, elevations, and known points of groundwater outflow
are minimal requirements to satisfy these needs of the reviewer.
The review of measures taken to control surface and subsurface
flows is of particular significance in areas with complex surface
drainage patterns and/or areas with numerous natural outlets for
subsurface flows.
Excavated materials^ removed from channels must be disposed of.
The removal of such materials occurs during both the construction
and maintenance phases of a project. Utilization of the excavated
materials, or their other disposition, is a function of: the nature
of these materials, the requirements for adjunct project features
(e.g., berms and levees), and the constraints imposed by adjacent
land uses or topography.
The reviewer should find in the EIS specifications for:
the dimensions of the areas required for spoil disposal, character-
istics (e.g., organic content and compressibility) of the excavated
materials, and plans for stabilizing these materials (e.g., with
vegetation, retaining walls, terraces, etc.). Periodic maintenance
implies the removal of trash and debris, sometimes to off-project
sites, and it is important that the resultant impacts of such oper-
ations be assessed (e.g., as impacts to air quality, filling
wetlands, over-loading solid waste programs, etc.).
It is also important that all impacts associated with spoil
disposal be at least qualitatively assessed in the review process
and that the reviewer exercise both imagination and judgment in
determining if all alternatives have been addressed and if the miti-
gating measures proposed for pollution abatement are feasible.
Groundwater Protection. During construction, operation,
or maintenance of a channel project there may be disturbances to
the groundwater regime in the project vicinity. Typical of the
impacts which may have to be assessed are those which intercept,
augment, or diminish groundwater flows in the project area. These
may be caused by: 1) excavation of the channel itself or by
collecting drains, 2) the placement of spoil on top of recharge
areas, or 3) the ponding of waters (behind weirs, dams, or log-
jams) in temporary or permanent collecting basins. In some situa-
tions in marine coastal environments the excavation of a channel
may induce an outflow of fresh groundwater into the channel thereby
IV-4 7
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permitting the inland encroachment of underground saline waters.
The reviewer may find the existence or probability of such impacts
explicity stated in the EIS or their significance may have to
be deduced.
Remedies, mitigating measures and alternatives may be considered.
Some of these can be: 1) lining permeable channel banks to reduce
losses (outflow) to permeable strata and/or prevent inflow of
degraded waters (for example: from waters which have leached
undesirable quantities of soil minerals) from intercepted aquifers;
2) installation of subsurface drains or construction of off-channel
recharge basins to counteract the loss of natural areas where
groundwater recharge previously occurred; and 3) locating ponding
and recharge areas so that degrading influences on groundwater
quality and volumes are minimal.
None of the above-mentioned ameliorating measures, however,
are impact-free. When upstream sources of pollution exist and have
degraded surface waters that are thereafter induced, or allowed,
to recharge aquifers there should be critical concern about water
quality standards. The addition of non-consumptively-used water
from irrigated lands (i.e. "return flows" with high mineral salt
content) to channel flows is a related example of this same sort.
But, on the other hand, in a watercourse where water temperature
is of critical concern (for example, to sustain certain aquatic
species) the addition of appreciable groundwater flows which
normally have a temperature equivalent to the area's mean annual
temperature may be purposefully and beneficially induced to lower
the ambient water temperature. In water-poor areas the reviewer
should expect to find that evaporative losses which might affect
groundwater reserves have been considered. And where potential
recharge areas are being considered there should be concern about
the influence of abutting land-use practices.
In summary, the reviewer's task in assessing impacts on ground-
water resources will be focused on those affecting water quality
in both the surface and underground systems. Standards and criteria
for these inter-connected systems have been previously discussed
in this section and their importance to aquatic and terrestrial
ecosystems is to be found in subsequent sections (IV.B and IV.C).
TTT A Ft
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IV.B. Review of Aquatic Ecology Impacts
Aquatic ecology impacts are discussed in this section under
the broad categories of physical habitat alteration and changes
in land use and water quality. Since aquatic ecgsystem response
is closely linked to the nature and extent of hydrology and water
quality impacts, the reviewer should refer freely to the guidance
on sources and quantification of these impacts found in the pre-
vious section.
Although some of the impacts of channelization activities are
of relatively short duration, many ecological effects have been
observed to persist for long periods, even after cessation of all
maintenance activities. Channelization must be viewed as a long-
term commitment of environmental resources which is perhaps not
fully recoverable at least in the space of years or decades. In
reviewing the EIS sections dealing with ecological impacts, this
concept should be kept in mind.
IV.B.I. Sources of Impacts
Channelization can profoundly affect the ecology of a project
area. Channelization activities generally elicit substantial
alterations in the physical and chemical characteristics of
affected aquatic habitats. Clearing and snagging, removal of
obstructions, channel excavation, disposal of excavated material,
construction of ancillary facilities such as grade control
structures or sediment basins, and new hydrological regimes all
leave their mark on the ecology of the watercourse. The degree
to which various impacts will occur is a function of project-
specific features. Hence, project evaluation must be predicated
in large part on local and regional environmental and institutional
conditions.
Most of the ecological impacts of channelization can be related
to the introduction of uniformity into a naturally .diverse system,
whether by straightening, removal of obstructions or bank vegeta-
tion or any other actions. The theme of diversity recurs through-
out this section and is basic to impact evaluation.
Three basic ecological principles underlie the identification
and assessment of impacts: ^-3
1. The greater the diversity of the conditions in a locality
the larger is the number of species which make up the
biotic community.
2. The more the conditions in a locality deviate from normal,
and hence from the normal optima of most species, the
smaller is the number of species which occur there and
the greater the number of individuals of each of the
species which do occur.
3. The longer a locality has been in the same condition the
richer is its biotic community and the more stable it is.
IV-49
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The information contained in the following subsections should
help the reviewer to identify those impacts and sources of impacts
that need to be considered for channelization projects in various
settings and with various activities involved in the construction,
operation, and maintenance of the channel.
Habitat Alteration by Debris and Riparian Vegetation Removal.
Stream channelization projects frequently involve removal of in-
stream debris which acts as a flow retardant, and clearing of
bankside debris and vegetation which can retard flow during flood-
stage periods. Clearing of instream debris oftentimes constitutes
habitat destruction for some of the more important members of
the aquatic community. Debris-laden areas often serve as shelter,
feeding, and reproduction areas for fish, insects, and other
organisms. Roots, stumps, snags, and other obstructions are impor-
tant to the ecology of both cold- and warmwater streams; elimina-
tion of these elements from the ecosystem can adversely affect
the carrying capacity of a watercourse for fish species and may
reduce species diversity as well. Snagging operations are a
part of virtually all channelization projects where debris accumu-
lation affects hydraulic capacity and may be carried out apart
from or in conjunction with other channel modifications as well
as during channel maintenance.
Clearing of bankside vegetation may be deleterious to the
aquatic environment in several basic ways. First, the potential
for erosion of the stream or channel banks may be increased con-
siderably, especially if bank stabilization measures are not
included in the proposed project for all affected areas. Sedi-
ment eroded from unprotected or cleared channel banks may impact
on the biota in the project area and also affect downstream
habitat either as a suspended solids load or by sedimentation on
the stream bed.
Streambank vegetation and overhanging branches often produce
a mottled sunlight-shade pattern that is conducive to organisms
with differing preferences for light intensity, thereby contribu-
ting to habitat diversity. Elimination of riparian vegetation
for channel improvement works would decrease this aspect of
variability in the aquatic ecosystem. A great increase in rooted
aquatic and algal vegetation was observed in many sections of the
channelized streams investigated in the CEQ channel modification
study.44 increased light with the clearing of bankside vege-
tation and additional nutrients brought about by increased sedi-
mentation or changes in land use may both be partly responsible
for these changes. Such growths would greatly alter the channel
habitat and probably cause a decrease in species diversity.
The other potentially critical impact is the alteration of
thermal regimes when trees and other shade-producing vegetation
are removed. Maximum summer stream temperatures may be appre-
ciably increased following canopy destruction, but the diurnal
ronge of temperature variation may also be greater. In streams
where coldwater species are living close to their critical thermal
IV-50
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maxima during the summer months, further temperature increases
might preclude habitation of affected areas, particularly in
shallow waters and riffle areas under low-flow conditions.
Temperatures above the optimum range for trout may cause mortality,
decrease growth rates due to higher metabolism, or increase suscep-
tibility to disease. Fryer and Pilcher, 45 in studying several
species of trout and salmon, found that the progress of infections
was accelerated and mortality rates were greater at higher water
temperatures. Warmwater biota can also be affected, since higher
temperatures reduce the capacity for oxygen absorption. Tempera-
tures do not have to approach critical maximum limits for important
impacts to occur. Most organisms exhibit a temperature range
within which optimum growth and development take place and devia-
tions toward the extremes of this range may reduce productivity
without eliminating a species entirely.
For many streams, particularly those in unpolluted headwaters,
natural vegetation along the banks is an important source of
organic matter and nutrients for supporting aquatic life. Leaves,
terrestrial insects, and other inputs are contingent on the
maintenance of riparian vegetation, the removal of which could
contribute to a decline in the productivity of aquatic biota.
These impacts cannot be isolated from the related probable effects
on temperature, sediment production, and other environmental fac-
tors; rather, their interrelatedness with respect to the aquatic
ecology must be recognized.
Habitat Alteration by Channel Excavation and Maintenance.
Excavation of new or existing channels typically causes turbidity
and sedimentation due to the operation of construction equipment
directly in or adjacent to a watercourse, and temporary bank
instability may also lead to sloughage and erosion. Changes in
gradient and flow regime brought about by channel modification
may alter erosion and sedimentation patterns during the opera-
tional phase of a project. These physical changes can result in
severe impacts on aquatic ecosystems in the project area and in
downstream sections. Perhaps the most obvious effect is that of
marked habitat alteration in the reach which is directly affected
by dredging or excavation. Besides destroying resident benthic
organisms and perhaps fish, channel excavation may produce long-
lasting changes in the nature of the stream bed and banks which
will influence the diversity and productivity of aquatic life.
Replacement of a gravel substrate with an unstable sandy bottom,
for example, will probably eliminate many species of benthic
invertebrates that cannot live on sand and favor establishment of
a reduced faunal assemblage.
An even more fundamental consideration is the impact of
channelization on the total amount of aquatic habitat which can
act as a productive resource. Channel straightening will result
in the elimination of backwaters and meanders and a net reduction
in stream length. Substantial alterations of an existing channel,
such as the removal of shoals and creation of a uniform channel
bed, may also decrease the habitat available for native aquatic
organisms. Maintenance of aquatic habitat in stream sections
IV-51
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isolated by channel straightening may reduce losses, but sedi-
mentation often causes them to fill in rather quickly and com-
plicates effective management. Unless an adequate supply of
freshwater is circulated through an oxbow, little potential
exists for maintaining the aquatic environment in a condition
approximating that of the original stream prior to channeliza-
tion.
Both increased suspended and settleable solids can have
adverse effects on populations of aquatic organisms in the tribu-
tary systems where stream channelization is usually conducted.
High suspended solids loads can abrade fish gill filaments and
adversely affect feeding by reducing vision and olfactory sensi-
tivity.- If organic fractions of the suspended load are increased,
dissolved oxygen deficits may cause active avoidance of the
stressed areas by sensitive fish populations. These stresses may
be especially important for channelization or dredging activities
in or near estuaries where they may delay or bar the upstream
migration of anadromous salmonids or clupeids (shad, for example).
Suspended solids loadings can also have indirect effects on
fish populations by affecting other elements of the food web in
aquatic ecosystems. Turbidity increases can cause reductions in
primary productivity and the particulate materials can inhibit
the productivity of benthic macroinvertebrates, particularly
those which depend on trapping or filter feeding for their exis-
tence.
Downstream sedimentation can alter the physical characteris-
tics of the substratum, thus affecting habitat values. Sedi-
mentation of fine particulates can have adverse effects on
reproductive success of any or all fish populations which may
utilize the affected area for spawning. Sedimentation can smother
eggs, alevins, or frys by decreasing intragravel water flow and
dissolved gas exchange, and can render the bottom unsuitable for
redd or nest construction.
The hydraulic changes brought about by channel excavation
will influence the aquatic ecosystem over the long term, modifying
erosion and sedimentation processes and flow regimen. The pro-
bable erosional and depositional patterns discussed in Section
IV.A.I for channel straightening, widening, deepening, and other
modifications will have an impact on ecological diversity and
productivity, depending on the extent and environmental features
of the channel and stream segments that are involved. Species
that require clean gravel for spawning or as habitat would not
adjust well to areas where the flow regime resulted in deposition
of fine-grained sediments but might be benefitted where scouring
increased due to channelization. The tendency of a stream to
regrade following construction of a meander cutoff (Figure IV-1)
would, for example, result in degradation above and aggradation
below the shortened reach, with resultant effects on the benthic
communities.
Water velocity is one of the most important ecological features
IV-5 2
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of the stream environment, influencing in large measure the
bottom composition, erosion and sediment transport patterns,
and the kinds and abundance of aquatic organisms that may inhabit
a given area. Not only velocity but also differences in velocity
affect the ecosystem. A natural stream may exhibit a great diver-
sity of velocity patterns and "microhabitats ," both longitudi-
nally and laterally, due to the presence of meanders, vertical
variations in slope, obstructions, pools and riffles. Even a
single species depends on this habitat diversity; for example,
adult trout occupy habitat with velocity, substrate, and other
features that are often quite different from those characterizing
habitat for fry or fingerlings. Channel excavation and mainten-
ance very often introduce greater uniformity of velocity and
substrate characteristics, to the detriment of the aquatic species
inhabiting the reach. Channel projects that increase flow velo-
city and entail the removal of rubble, snags, and other cover are
likely to support fish populations much reduced from those prior
to channelization. Even strong-swimming fish such as trout which
actively feed in fast-moving water cannot maintain that position
for long and must have access to deep water or cover where
velocities are lower.
A variety of current regimes and patterns enables more species
to live in a given area than would be possible under channelized
conditions. The hydraulic effects of channelization may be
important under all flow conditions. Velocities associated
with flood discharges will be greater than the unaltered stream
because flow is confined to the channel instead of spreading
over adjacent flood plains. In the same channel, water depths
at low flows may be decreased if obstructions and debris have
been removed or the channel bottom widened. Diversity of species
in an aquatic environment contributes to stability and the ability
of the communities to withstand floods, droughts, and other
adverse natural occurrences.
Effects of channelization on groundwater and thus on surface
water hydrology have ecological implications as well. Reduction
of flooding frequency and modifications of the stream cross-
section by deepening, widening, and levee construction or land
disposal of excavated materials can decrease or eliminate riparian
flood plains as a part of the aquatic ecosystem. Some aquatic
species are floodwater spawners and utilize as breeding areas
flood plain ponds that are interconnected with the stream during
high water. Channelization can upset this important ecological
interrelationship between flood plains and rivers as, of course,
flood plain land use changes may also. Likewise, reduction of
overbank flooding would result in the transport to downstream
roaches of suspended solids, nutrients, and other constituents
normally removed by sedimentation on riparian areas.
Main channel excavation and related construction of field
drains for the purpose of improving drainage of agricultural
lands, riparian wetlands, or other areas are likely to decrease
groundwater recharge, accelerate runoff, and lower the ground-
water table in affected areas. The result may be a decrease in
IV-5 3
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base flow in the channel during dry periods when the majority
of discharge is supplied by groundwater. In some instances,
effects on groundwater levels can be sufficient to cause inter-
mittent flows in streams tributary to a channelized reach, even
in water-rich areas such as North Carolina.46 Obviously, impacts
on the aquatic ecosystem would be severe in this situation. The
subsections on groundwater in Section IV.A should be consulted
for further information on the physical and hydrologic conditions
under which problems of this sort may occur.
Realignment of a channel that results in creation of back-
water areas in the old stream bed may have important ecological
consequences. In the extreme, such areas would be drained or
converted to dry land thus eliminating aquatic habitat. More
commonly, however, reduction of water velocities will induce
establishment of a different species composition from that of
the stream environment. The aquatic habitat values associated
with backwaters will depend on the type of ecosystem which
develops in response to sedimentation, water levels and flow,
depths, water quality, and other environmental variables.
Ecological impacts of channel maintenance depend largely on
the nature and frequency of maintenance activities, which in
turn vary with project purposes, design and setting, and the
specific arrangements made for carrying out maintenance work.
Channel maintenance may consist of mechanical removal or herbi-
cide treatment of unwanted vegetation that has encroached on the
banks, removal of sediments and debris from the channel and sedi-
ment basins and repair of eroded banks, rip-rap, lining, and
ancillary structures. Once construction is completed, exposure
to natural forces causes adjustments of the channel bed and
banks to the new conditions. Indigenous vegetation may displace
or supplement grasses or herbaceous cover planted on the banks,
possibly contributing to their stability and erosion resistance.
The channel itself may aggrade and degrade at various locations
in response to the imposed hydraulics, and debris areas may be
formed. These factors of aging work toward restoring ecologi-
cal diversity and stability in the modified channel, but may
impede hydraulic efficiency. The maintenance activities men-
tioned above arrest the trend to ecological recovery of the
channel and cause recurring habitat instability. In general,
then, channel maintenance perpetuates ecological impacts but is
necessary to insure that the project serves the flood control,
drainage, or other purpose for which it was designed.
Habitat Alteration by Changes in Land Use and Water Quality.
Channelization usually allows more intensive or productive use
of existing agricultural or urban lands, and may additionally
induce changes in land use in areas that: (a) are readily be
drained or (b) receive flood protection by the project. The
aquatic ecology aspects of land use changes have already been
alluded to and relate basically to the role of flood plains as an
integral part of the aquatic ecosystem and potential changes
in water quality. Agricultural lands have been shown by many
IV-5 4
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studies to be greater contributors of pollutants such as sedi-
ments, nutrients, and pesticides, than are forests, grasslands,
and other natural vegetation associations. Similarly, urban areas
can produce a wide variety of polluting substances that may be
conveyed to waterways with storm runoff and through storm drainage
systems, or as wastewater treatment plant effluents.
The impacts of sediments on organisms and habitat stability
have been discussed earlier. Increases in nutrient loads from
agricultural or urban runoff may stimulate the growth of algae
and rooted aquatic vegetation in and downstream from a channel,
thereby altering primary productivity. Introduction of pesti-
cides is of concern not only because of potential toxicity
but also because of possible bioaccumulation and concentration
in aquatic organisms and species higher in the food chain. These
impacts may vary considerably, and may be negligible in certain
cases, depending on existing water quality, the probable nature
and extent of land use shifts in areas affected by a channel pro-
ject, and the use and effectiveness of land treatment measures
proposed for the watershed, if any.
IV.B.2. Review of Impact Quantification
A substantial amount of scientific literature has been developed
which relates to ecosystem structure and function in stream habi-
tats. Investigations have focused on a variety of natural streams
and those subjected to channelization at one time or another.
Although consistent qualitative changes are frequently observed,
such as reduction of fish standing crop or alteration of benthic
community composition and diversity, prediction methods for changes
which may occur due to channelization have not developed to the
point where reliable quantitative estimates can be made. The
difficulty arises from two fundamental factors: stream channels
and their ecosystems are quite heterogeneous, and no two channel-
ization projects are exactly alike.
Essential to ecological impact quantification is an under-
standing of aquatic ecology in the area to be altered and the
physical features and design of the channel, combined with pre-
diction of changes in hydrology and water quality (see Section
IV.A.2). Most EIS's will contain such information and analyses
in varying detail and comprehensiveness. Estimates of impacts
are usually based on general knowledge of ecological requirements
and interrelationships of the affected species and experience at
other projects in the region rather than sophisticated modelling
or other advanced techniques. Evaluation of impact quantification
therefore requires judgment as to the adequacy of the information
from which ecological conclusions are drawn, in terms of the
scope of the project and the overall environmental setting. The
manner in which hydrology and water quality issues are treated is
especially important; if the EIS description of these factors is
insufficient, then it is likely that estimates of aquatic ecology
impacts will be similarly deficient.
IV-5 5
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The guidance in this section should aid on conducting these
evaluations.
Habitat Alteration by Debris and Riparian Vegetation Removal.
Because of the complexity of aquatic ecosystems, predictions of
impacts may be largely quantitative or judgjaental although some
relevant factors can be described quantitatively. Information
presented in the EIS should cover basic clearing and snagging
operations from at least the perspectives of the affected stream
areas and the resulting differences of habitat from preproject
conditions that such work would cause. Thus, the reviewer should
expect the EIS to contain as fundamental data: the lengths and
locations of stream segments where debris removal or clearing
would be conducted, and the nature of the material to be removed.
Impacts will depend on the relationship of bankside vege-
tation and instream debris to the overall available habitat;
that is, clearing and snagging on a fairly wide and deep stream
will probably not be as ecologically damaging as on a small
stream where riparian vegetation and debris provide much or most
of the shelter suitable for fish populations. Also, relatively
permanent debris-laden areas formed, for example, by large trees
that have fallen into or near a stream may furnish very favorable
aquatic habitats as contrasted with temporary obstructions that
are vulnerable to washout during high water periods. The magni-
tude of impacts of debris removal will thus depend on the charac-
ter of the area to be altered. In general, the elimination of
cover due to clearing and snagging will almost always have an
adverse effect on fish populations, and should be recognized in
the EIS. The width and depth of the stream, the amount and type
of cover and habitat affected by clearing and snagging, and other
channelization activities in the affected areas are the princi-
pal variables the reviewer should expect to be addressed.
Clearing of streamside vegetation is one of several channeli-
zation activities that may cause an increase in suspended solids
loads. Impacts would be most severe during construction and
probably decline as new vegetation is established or bank pro-
tection measures are installed. As pointed out in the section
on quantification of construction and maintenance impacts, pre-
cise numerical estimates of turbidity or suspended solids concen-
trations may not be made in the EIS; rather, the reviewer's con-
cern should be to ensure that reasonable controls will be applied
in the construction phase to minimize erosion and sedimentation.
Resulting effects on the aquatic ecosystem will depend on the
types of organisms present and the area subjected to increased
turbidity. Many benthic invertebrates, such as the larvae of
caddisflies, many mayflies, and stoneflies, are typically associa-
ted with clean gravel substrates and are intolerant of sedimentation.
Trout and other species of fish cannot spawn successfully in
stream reaches where fine sediments cover the bottom. Sedimen-
tation from clearing and snagging may not be critical, for
instance, if the stream segments that would be affected are currently
-------
characterized by fine, unconsolidated, and unstable sediments and
a benthic community adapted to such conditions.
The effects of clearing bankside vegetation on water tempera-
tures will be greatest on narrow streams where trees form a closed
canopy or shade a significant portion of the water surface,
whereas impacts may be minor on wide streams. Temperature in-
creases of several degrees (C°) may result from removal of trees
along a shaded watercourse. Ecological implications of a given
change, however, are difficult to quantify. Brown 4 7 noted that
no mortality of coho salmon attributable to high temperatures
occurred in a clear-cut study stream even though temperatures
more than 8°F above the reported lethal limit for the species
(77°F) were recorded. He pointed out the present lack of eco-
logical information on the effects of high but sublethal tempera-
tures on stream organisms. It is, nevertheless, important that
the EIS contain information on existing water temperatures and
the probable impact of riparian vegetation clearing (see Section
IV.A.2). As long as regrowth of bankside vegetation is prevented
by channel operation and maintenance, the altered thermal regime
will persist. The EIS should relate anticipated changes to the
thermal requirements of species inhabiting the project area; this
is particularly important in the case of salmonids whose optimum
temperature range is lower than that of most other fish.
Habitat Alteration by Channej^ Excavation and Maintenance.
Relevant to all channelization projects is quantification of the
aquatic habitat in the project area and the nature and extent of
proposed modifications. Data on the following are essential:
- Total length and normal surface area of unaltered stream
and proposed channel.
- Length and location of pools, riffles, and various bottom
types under existing and channelized conditions.
A channelization project involving realignment of a stream
typically reduces (a) biological productivity because the new
channel is shorter with less overall habitat available and (b)
the carrying capacity for aquatic biota due to channel straighten-
ing and alteration of hydrologic and morphologic characteristics.
On the other hand, widening an existing stream channel may pro-
duce a net increase in the water surface area and habitat for
aquatic organisms. Reduced water depths, loss of riparian vege-
tation, and removal of instream obstructions and cover would,
however, detract from the ecological value of the added water
area.
Beyond quantification of habitat gains and losses, estimates
of aquatic ecosystem response should be contained in the EIS.
Methods for arriving at these estimates range from simple pre-
dictions based on a knowledge of the kinds of fish inhabiting
the area to detailed assessments based on quantitative surveys
of fish, benthic communities, and habitat. The level of detail
necessary for adequate estimation of impacts varies with the scope
IV-5 7
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and complexity of the project as well as the natural, scenic,
recreational, or commercial value attached to the stream and
fishery. Collection of baseline data on aquatic organisms re-
quires considerable time, effort, and skill. In quantitative
studies considerable numbers of samples may need to be taken in
order to obtain representative, reliable results. It is desirable
to sample many different types of habitats within the area of
interest. Because data requirements depend on the nature of a
project and probable impacts, specific guidance on what information
should be included in the EIS cannot be given. However, the
following descriptions should help in understanding the relevance
of various categories of biological data to a particular channel
project. Chapter 5 of the report by Cooper et al. 48 discusses
the time, personnel, and equipment requirements for aquatic
flora and fauna measurement techniques, and should be consulted
for supplemental guidance.
- Fisheries. As a minimum requirement for all channelization
projects, an inventory of the fish species inhabiting a proposed
project area should be conducted. Reliable information sources
include the state fish and wildlife agency and possibly the U.S.
Fish and Wildlife Service if involved in reconnaissance or field
investigations during project planning. Or, the channel plan-
ning agency may carry out such data gathering using its own
staff. The nature of any fish stocking or management programs
and data on fishing pressure and harvest should be included in
the EIS, if available and applicable. Data on fish populations
and production are important because:
(1) Fish are normally the major usable, renewable resource
of the aquatic ecosystem, and
(2) the condition of fish populations is an indication of
habitat conditions and cumulative productivity.
Besides being useful for estimation of impacts, quantitative
information on preproject fisheries as well as other biota is
valuable as a basis for comparative follow-up studies should
the channel be constructed.
- Benthic Invertebrates. A survey of benthic fauna may be
undertaken to furnish information supplemental to fisheries data.
Benthic invertebrates are the major food source of stream fish.
Generally, only very rough quantitative estimates are obtainable
and extrapolation of several sample results to a biomass esti-
mate for a stream segment is likely to lead to erroneous conclu-
sions. Difficulties in accurate benthic sampling are to some
extent inherent in the sampling methods which often have different
selectivity for different organisms, and in the wide variations
of organism abundance both spatially and temporally. For most
purposes, the types of organisms present, observations of their
relative abundance, and the nature of the substrates from which
samples were taken are of interest for impact quantification.
In particular, knowledge of benthic fauna common to the project
area and their habitat preferences can be related to the bottom
IV-58
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characteristics, velocity, and other conditions expected after
channel construction,
- Algae/ periphyton, and larger aquatic plants. Useful
measurements of phytoplankton in streams are complicated by pro-
blems of seasonal and diurnal differences as well as sampling
difficulties. Therefore, any quantitative estimates should be
described in terms of the probable limitations of the data.
Generally, phytoplankton populations are greater in the low-
gradient, quiescent reaches of a stream than in rapids and
riffles. Turbidity may also limit their abundance. For channeli-
zation projects that may indirectly cause increased nutrient loads
due to changes in agricultural or urban land uses, knowledge of
existing population distributions among the major groups of
algae (generally diatoms, green, and blue-green) may be helpful.
Aquatic macrophytes ordinarily do not occur in any abundance in
swiftly flowing water, but may be an important component of the
ecosystem in slow, meandering flood plain streams. Visual
observations or sampling may suffice to indicate types and distri-
bution in a project area. General descriptions of the location,
kinds, and abundance of weed beds should be included in the EIS.
Effects of Suspended Solids and Sedimentation. Suspended
solids can have adverse effects on all aquatic biota. The magni-
tude of ecological impacts is directly related to concentration,
although the size, angularity, and composition of the particles
also influence organism response. The duration factor is also
relevant, as most organisms can tolerate very high levels of
suspended solids for short periods of time, but will suffer
adverse effects if the conditions persist. Estimates of the
impacts should follow from quantification of suspended solids
loads associated with construction, maintenance, bank erosion,
land uses, and land treatment measures. Effects on primary
production due to reduction of light intensity are difficult to
quantify; construction-induced turbidity will probably not have
significant effects whereas a general longer-term increase in
suspended solids may cause a downward shift in productivity.
The biological impacts of sedimentation are perhaps more
readily discernible than impacts of suspended solids. Proper
quantification entails identification of areas that will be
affected both in and downstream from a channel project. For
both the periphyton (or Aufwuchs) and benthic invertebrates,
substratum stability is one of the main determinants of abundance
and diversity. Table IV-8 categorizes several groups of bottom-
dwelling macroinvertebrates according to their general tolerance
to pollution, which would include effects of sedimentation of
inorganic solids or organic matter. Although there may be
exceptions, the organisms are listed in the usual order of
disappearance below pollution sources. The morphological struc-
ture of benthic fauna is an important factor in this pattern:
Species with complex appendages and exposed complicated
respiratory structures, such as stonefly nymphs, mayfly
nymphs, and caddisfly larvae, that are subjected to a
IV-5 9
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Table IV-8.
General Tolerance of Representative
Benthic Macroinvertebrates to Pollution
Sensitive
Intermediate
Tolerant
Stonefly nymph
Mayfly nymph
Hellgrarnmite or
Dobsonfly larvae
Caddisfly larvae (Trichoptera)
(Plecoptera)
(Ephemeroptera)
(Megaloptera)
Black fly larvae
Scud
Aquatic Sowbug
Snail
Fingernail clam
Damselfly nymph
Dragonfly nymph
Bloodworm or midge
fly larvae
(Simuliidae)
(Amphipoda)
(Isopoda)
(Gastropoda)
Leech
Sludgeworm
Sewage fly
larvae
Rat-tailed
maggot
(Sphaeriidae)
(Zygoptera)
(Anisoptera)
(Chironomidae)
(H'irudinea)
(Tubificidae
(Psychodidat
(Tubifera-
Eristalis
Water-Quality Improving
Water Quality Deteriorating
SOURCE: Sinclair, op. cit., p. 22-4.
-------
constant deluge of settleable particulate matter soon
abandon the polluted area because of the constant preening
required to maintain mobility or respiratory functions;
otherwise, they are soon smothered.'49
In reviewing predicted impacts of suspended solids and sedi-
mentation on fish, both direct and indirect effects should be
considered. Gravel is probably the most commonly used substratum
for spawning of many species of fish found in running water.
Even many species which normally live over sandy bottoms move
to gravel areas in faster water to spawn. If the proposed pro-
ject area contains spawning areas of important fish species, the
degree to which the spawning sites will be altered or destroyed
and the resulting impacts on population levels of affected
species should be examined. Impact predictions should be based
on:
- the extent of the area used for spawning;
- an estimation of the number of eggs deposited within the
area, the proportion which hatch, and the survival rate
to reproductive maturity by species;
- knowledge of impacts on spawning habitat gained from
studies of other channel projects;
- knowledge of spawning frequency and timing;
- estimates of the magnitude, duration, and extent of
construction-generated turbidity and sedimentation;
- estimates of substrate composition with aging of the channel,
from the knowledge of channel gradient, geometry, flow, and
other hydrologic characteristics.
Channel construction, operation, and maintenance may similarly
have adverse effects on reaches of a stream used as a migratory
corridor by important fish species during specific times of the
year. Upstream migration for spawning is a behavioral trait
common to many species of fish, although the distances travelled
and the importance of the movements for reproductive success
vary widely depending on the size and type of stream, geographic
location, and numerous other factors. Disruption or blockage of
migration may be caused either by the creation of physical barriers
such as impoundments or grade stabilization structures, or by
creation of behavioral or physiological barriers such as exten-
sive turbidity and sedimentation. In general, the construction
phase of a project has the greatest potential to produce tur-
bidity conditions adverse to fish migrations, with spring and
autumn the critical periods for migration and spawning in most
temperate streams. Channelization conducted in coastal steams
or estuaries may especially impact on anadromous species that have
established annual runs into or through the proposed project
area. The reviewer should expect the estimates of these impacts
IV-61
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to include consideration of migratory frequency and periodicity,
the size of the migrating populations, and the timing and dura-
tion of construction and maintenance activities. It should be
noted that construction and maintenance may inhibit migratory
movements of fish and affect reproductive success for only a
relatively short period, whereas the presence of ancillary
structures could have an effect year after year.
Indirectly, suspended solids and sedimentation may be detri-
mental to resident fish populations due to their effects on
benthic communities which serve as a major food source for fish.
Generally, the types of organisms used extensively for food are
thos-e which are less tolerant of sediment and other forms of
pollution, as indicated on Table IV-8. Also, an overall decrease
in productivity of a channel bottom because of sedimentation may
be reflected in a corresponding change in fishery potential.
These interrelationships should be considered in the EIS.
Effects of Altered Hydrologic Conditions. Besides their
relevance to erosion and sedimentatzon, hydrologic conditions of
a channel have other major influences on the nature of the aquatic
habitat and its favorability for various kinds of stream-dwelling
organisms. Quantification of impacts necessitates an under-
standing of the physical changes caused by channelization and
interpretation of those changes with respect to habitat pre-
ferences and biotic requirements of the species involved. The
magnitude of ecological impacts will be related generally to
the reduction in diversity which can be brought about by channeliza-
tion. It is imperative that the EIS compare hydrologic regimes
of the existing watercourse and proposed channel- Estimation of
impacts should include quantification of the following:
- Dimensions of pools and riffles for unaltered and altered
channel (including proposed water level and grade control
structures, etc.)
- Abundance and distribution of important fish species in
the reach to be channelized.
- Water velocities in representative segments under channelized
conditions, for representative flow conditions.
- Water depths under channelized conditions, at least for
low flow.
- Changes in low flow regime due to drainage or alteration
of groundwater contributions.
Generally, elimination of pools and riffles will disrupt the
aquatic floral and faunal assemblages characterizing each habi-
tat. The nature of the aquatic community that develops in the
channelized reach depends on, among other things, the expected
velocity and depth patterns. High velocities produced by
channel shortening and decreases in roughness, for example, may
IV-6 2
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inhibit re-establishment of any of the indigenous fish species.
Under different circumstances of moderated flow velocities and an
unconsolidated, unstable substratum as might occur with widening
or deepening an existing stream channel, less desirable fish
species than those present prior to channelization may be favored.
Larger fish of most stream species seek out the cover afforded
by deep water; elimination of pools and deep holes formed at the
outside of meander bends reduces the amount of habitat suitable
for larger fish and can jeopardize the overwinter survival of
both fish and other organisms. Since low flow conditions impose
a variety of stresses on aquatic biota, any expected decrease
in discharge as a result of channelization will have adverse
effects which may be more severe if deep pools have been elimina-
ted from the affected reach.
The magnitude of aquatic ecological impacts associated with
reducing the frequency of flooding on riparian wetlands adjacent
to a channel depends on: (a) the existing amount of such habitat,
(b) frequency, duration, and area of flooding on a seasonal basis
with and without the channel, and(c) the species of fish and other
aquatic organisms that utilize the areas as foraging, spawning,
and nursery habitat. Generally, freshwater and coastal backwaters,
marshes, and bottomland lakes that are interconnected with a
stream and whose water levels fluctuate with river stage have
an expecially important influence on productivity of the aquatic
ecosystem, and are also vulnerable to drainage or major altera-
tion by channelization. Many species will inhabit riparian
wetlands at some period during their life cycles; therefore, de-
tailed guidance cannot be given. The principal considerations for
impact prediction are, as mentioned above, the area of wetland
habitat that will be altered, the nature of the alterations, and
the species that will probably be impacted. If these factors
are not fully discussed and quantified where possible in the EIS,
the reviewer should suggest the acquisition of further information
to permit an adequate assessment of impacts.
The cause-effect relationships among flow, cover, velocity,
depth, numerous other environmental variables, and ecological
response are not well understood when viewed collectively. Never-
theless, many post-construction case studies confirm that
channelization usually results in a reduction of species
diversity and/or productivity for fish, benthic invertebrates,
and other organisms. The reviewer should not expect the EIS to
contain detailed predictions of impacts on standing crops of fish
or benthic invertebrates, total production, or other ecological
measures. Rather, it is important to ensure that the EIS
establishes the nature and value of the biotic resources that
would be affected by the proposed action. Judgments of the
adequacy of ecological impact quantification should then be made
according to the EIS description and treatment of physical,
hydrologic, and other environmental variables that will be altered.
Ecology of Channel-Created Backwaters. The fate of oxbows, mean-
ders, or channels that are cut off from the main discharge by chan-
IV-6 3
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nel realignment must be addressed. Specifically, the EIS should
describe plans for channel design features that would influence
the hydrology of isolated backwater areas and forecast the probable
ecological changes that would take place over time. For example,
expected hydrologic conditions, sediment loads, water depths,
and similar factors should be analyzed to estimate the rate at
which the old channels will fill in. With this knowledge, pre-
dictions should also be made of ecological succession, from marsh
to swamp to meadow or some other sequence, and the time periods
involved. The possibility that stream cut-offs will be drained
by a channel, filled and reclaimed for agriculture or other uses
must also be evaluated, as such activity would destroy the aquatic
or wetland habitat.
As mentioned earlier, the inlets and outlets of a cut-off
stream segment would be subject to rapid sedimentation and could
be difficult to keep open without periodic maintenance.
Generally, the aquatic ecosystem in backwaters created by
channelization will change appreciably. Lentic species will
predominate, soft-bodied forms will tend to dominate the ben-
thic assemblages, and the backwater will be particularly susceptible
towards dominance by insects. In addition to sedimentation rates,
water level fluctuations and nutrient loadings are important
determinants of the ecology of cut-off meanders or oxbows. Pro-
visions for water level control in the cut-off and their effect
on water surface fluctuations should be detailed in the EIS. An
oxbow may serve as a trap for incoming nutrients with the result
that eutrophic conditions may occur which can reduce the diversity
of aquatic species. Therefore, nutrient levels in runoff reaching
the area, as well as expected flushing and sedimentation rates,
should be estimated to obtain an estimate of the potential for
eutrophication. Excessively high productivity can ultimately
cause adverse reductions of dissolved oxygen concentrations and
general water quality. Low rates of water exchange along with
high sediment and nutrient inputs will be most conducive to eutrophi-
cation of cut-off meanders. Terrestrial habitat implications for
waterfowl and other wetland species should also be considered,
as discussed further in Section IV.C.2.
Effects of Altered Land Use and Water Quality. Estimates of
probable land use patterns in the area of influence of a proposed
channel project and the resultant changes in pollutant loads should
form the basis for ecological impact quantification. There may
be considerable uncertainty in forecasting future land uses,
fertilizer and pesticide applications, urban runoff-related
pollutants, the application and effectiveness of land treatment
measures, and other water quality influences, which complicate
the prediction of ecological impacts. Generally, those projects
which involve drainage of agricultural lands or wetlands offer
the greatest potential for increasing pesticide residues in a
stream course, particularly in small streams during low-flow
periods.
IV-6 4
-------
Baseline data on pesticide and other pollutant loads from the
watershed and resulting concentrations in stream segments should
be presented in the EIS to establish existing water quality condi-
tions or problems. Increases in nutrients from agricultural or
urban runoff may affect the aquatic ecosystems by stimulating
growth of algae or rooted aquatic plants in the channel, especially
if water velocities are expected to be fairly low, the water is
shallow, and a silty substrate develops. These conditions, along
with increased exposure to light following bankside vegetation
clearing may all contribute to development of rooted aquatic and
algal mats on the channel bed. Ecologically, large populations
of algae and aquatic plants help induce a change in the faunal
associations, typically to the detriment of species that are
commercially or recreationally important.
Prediction of impacts must involve quantification of those
anticipated environmental conditions discussed above in order that
susceptible areas of the channel can be identified. It is likely
under the conditions described that fish species would shift to
a composition similar to that characterizing shoal areas further
downstream in the watershed. As examples, trout might be re-
placed by bass and perch, or the latter by carp and catfish.
Project and watershed specific inventories of fish species and
populations are, however, necessary to estimate distributional
changes.
IV.B.3. Assessment of Impacts
Assessment of aquatic ecology impacts should be viewed as a
synopsis of EPA's concerns from the perspectives of the agency's
legislative mandates, regulatory authority,-and responsibilities
for management and protection of the environment. Objective
criteria do not exist by which all of the potential ecological
impacts of channelization can be assessed. In some cases, there-
fore, reference may have to be made to other measures of the
importance and value attached to natural streams and their biotic
resources. These might include the extent of recreational
fishing use of the project area, the regional availability of
unaltered streams with characteristics similar to the project
area, the probability of cumulative losses of natural streams in
the region through water resource development activities, and
the presence of unique, rare or endangered fauna in the vicinity
of the proposed project. The guidance of this section should
alert the reviewer to (a) the applicability of criteria for water
quality protective of aquatic life, (b) considerations in assessing
ecological impacts for which less explicit criteria exist, and
(c) the need for and effectiveness of impact-mitigation measures.
Judgments should first be made as to the adequacy of identi-
fication, description, and quantification of probable impacts
in the EIS, aided by the discussions in Sections IV.B.I. and IV.
B.2. Any inconsistencies, insufficiency of baseline data, or
other aspects of the EIS that hinder a proper evaluation of im-
pacts should be noted and reflected in the project rating. Eco-
logical impacts should be viewed in as broad a context as possible,
IV-6 5
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in terms of overall and combined effects on aquatic biota and the
nature of the resource commitment. Water quality standards and
criteria only partially serve this approach, since impacts such
as loss of aquatic habitat or habitat modifications that produce
a shift in- species composition may not be specifically addressed
by the criteria. Thus, the reviewer must assess concurrently
the ecological implications of water quality impacts and the
physical and other changes brought about by channelization.
The assessment of thermal regime alterations should be based
essentially on the thermal criteria for growth and spawning of
commercially or recreationally important fish species inhabiting
the project area. Tables 5 and 6 and Appendix A in EPA's Pro-
posed Criteria for Water Quality, Volume I, (October 1973)
should be consulted, as well as applicable state water quality
standards relating to temperature alterations. The ecological
significance of clearing bankside vegetation and thereby in-
creasing maximum water temperatures and fluctuations depends on
(a) the magnitude of the expected temperature increase and (b)
the suitability of existing temperature patterns for the species
involved. For example, an upward shift in maximum temperatures
by "x" degrees in a stream whose thermal regime is currently
above the optimum for certain species may eliminate them, whereas
the same temperature change in a stream whose temperatures at
key periods are near optimum may stress the populations but not
eliminate them entirely. For projects where water temperatures
are likely to be increased by riparian vegetation clearing,
comments on the degree and significance of probable impacts
should be supported by specification of the relevant criteria.
The importance of the ecological impacts of suspended solids
generated during channel construction, operation, and maintenance,
and from changes in land use can be ascertained by relating
expected conditions to the criterion of 80 mg/1 as the maximum
acceptable total concentration of suspended solids in fresh water.
However, a complete assessment involves evaluation of other
factors, including the duration of sediment inputs and the
expected erosion and sedimentation patterns in, above, and below
the project area following channel modification. If there are
no reasons to expect that erosion and resulting turbidity will
persist after completion of the construction phase/ impacts may
be short-term and amenable to control by institution of proper
construction management practices.
Sediments that are deposited on the channel or stream bed
may be equally or more important than suspended materials with
respect to aquatic ecology. The relationship between suspended
and bed load sediments is dynamic in time and space; it does not
necessarily follow that no unacceptable impacts will result if
suspended solids concentrations are kept below a prescribed
value. For instance, an unstable channel bed made up of shifting
sand could exist under conditions of low suspended solids and
yet support few benthic fauna and be of no value as a fish spawning
area. This example emphasizes the importance of assessing ecological
IV-6 6
-------
impacts from a perspective encompassing the variety of changes
that may result from channelization; the reviewer should not
limit his evaluations to consideration of water quality para-
meters and criteria alone.
Other pollutants that may originate from lands affected by
the drainage or flood control functions of a channel, particularly
nutrients and pesticides, require special attention since they
are usually nonpoint in nature and thus may be difficult to con-
trol. The reviewer must assure that the EIS has examined the
issues of land use and related pollution potential adequately
in a geographic or area-of-influence sense and over a suitable
time period. Since accurate estimates of pollutant loadings
associated with induced changes in land use would be highly
speculative at best with effects difficult to separate from other
watershed influences, direct comparisons with appropriate cri-
teria probably cannot be made. Trends in agricultural and urban
land use in the basin, information on the present water quality
status in and downstream from the proposed project, and pro-
jections of future waste loads from all sources should be fac-
tored into an assessment of runoff-related pollutants and
resulting ecological impacts. Basin and areawide plans for
water quality management prepared under the 1972 FWPCA Amend-
ments should furnish supporting data for assessing the land use
and water quality issues of channelization from an ecological
perspective.
As was brought out previously, many of the ecological impacts
caused by channelization involve physical modification of habitat
elements such as velocity, cover, substratum, and light patterns
to which no explicit criteria can be applied. In these situa-
tions, the guidance contained in earlier sections should help in
determining whether the EIS has identified and appropriately
quantified probable impacts or, if not, in arriving at rough
estimates of the types of changes that would be likely. Impact
assessment then requires judgments of the importance and value
of the existing aquatic ecosystem and biota, and the degree to
which the resource would be committed or altered by the project.
Although a comprehensive enumeration of critical impacts on
aquatic ecology cannot be presented, the following types of
effects should be considered as serious and may warrant special
mitigation measures, alteration of the project design or loca-
tion, or selection of a nonchannel alternative for meeting water
resource development objectives:
- Adverse effect on habitat of rare or endangered species
- Significant disruption of spawning areas for commer-
cially or recreationally important fish species
- Significant destruction of cover and habitat essen-
tial to important species.
Inherent in channelization activities is the reduction of
IV-67
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environmental diversity which in turn reduces biotic diversity in
an aquatic ecosystem. Mitigation or rehabilitation measures in
general have the effect of restoring or preventing loss of ele-
ments of diversity in the environment that are sacrificed in the
course of channel modification. Table IV-7 describes those
techniques that may be incorporated into a channel design to
serve various purposes, including aquatic habitat enhancement.
Although these measures would produce notable benefits for fish
and other stream life in many cases, they also add to the project
cost and perhaps maintenance requirements.
In assessing whether mitigative measures have been adequa-
tely treated in an EIS, the reviewer should examine the reasons
for selecting or rejecting the measures that were considered and
the characteristics and extent of proposed mitigation in rela-
tion to the stream resource to be altered. Table IV-7 may be
used as a guide to both the beneficial and possible detrimental
aspects of mitigation techniques. Comments on the EIS should
be directed to the need and'desirability of maintaining reasonably
diverse habitat features for the survival of aquatic biota,
especially when values of scarcity, uniqueness or recreational
use are known to exist.
IV-68
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IV.C. Review of Terrestrial Ecology Impacts
The impacts upon terrestrial ecology, like those on aquatic
ecology discussed in the preceding section, may be categorized
either as changes in habitat or as changes in land use. Nonethe-
less and the same point has earlier been made there are
complex interrelationships between land and water systems so that
separation and classification of impacts in a wetland, for instance
is not always easily made on the basis of either the location or
nature of those impacts.
The conveyance of excess water, whether for flood control or
drainage, from one environment in which it occurs naturally
to another selected for convenience must be viewed in its appropriate
locational context. Intended land use is often the rationale
for such actions and, moreover, the definition of "excess" is not
always generally agreed upon by all concerned. Furthermore, lest
the problem of impact evaluation be oversimplified, there are wide
ranges of terrestrial conditions from pristine and undisturbed
to very much man-altered urban situations to which channelized
solutions are applied; resultant impacts, and the public responses
to them, differ greatly.
Terrestrial systems have been conventionally arranged for both
land use and habitat classification purposes as either upland,
riparian, or wetland. Each of these is differently defined in
terms of the land-water interfaces found there. The land use and
habitat characteristics are dependent upon the nature and dimension
of these interfaces. Impacts upon terrestrial ecosystems may be
further differentiated, for categorical purposes, on the basis of
their occurrence within either an arbitrarily restricted zone of
influence or within a more regional context; such distinctions may
also be considered as stemming from direct or indirect land modi-
fications.
The concept of recovery time for an impacted ecosystem is of
significance in the evaluation of terrestrial impacts. The recovery
of a channelized area's aesthetic values may occur over a period of
only a few years after which the raw scars may disappear. Ecologi-
cal impacts, on the other hand, are less easily assessed. And be-
cause of complex interrelationships these may range in severity
from permanent alteration or obliteration of ecosystems to subtle
local changes in amphibian species on a streambank, for example
which are barely distinguishable from evolutionary changes. The
reviewer, therefore, must be careful to differentiate between those
ecological impacts evaluated on short-term or easily observed evi-
dence and those which may become apparent only after carefully
studied changes in biological productivity of the trophic levels
of an impacted ecosystem.
IV.C.I. Sources of Impacts
Terrestrial impacts are most easily and obviously associated
IV-6 9
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with the construction activities responsible for alteration of
existing soils, vegetation and habitats alongside channelized sec-
tions. Clearing and grubbing, excavation and levee-building, dis-
posal of excavated spoil, channel relocation, and provisions made
for tributary junctions, culverts and access roads are all land-
disturbing activities resulting in the obvious alteration of land
bordering a project. And changes in flow regimes will have profound,
though not always obvious, influences upon riparian habitats, with
the result that resident species must react to changed nutrient
sources and levels. Land treatment measures, such as the building
of diversions, drains, and grassed waterways, or the institution
of contoured cropping programs in upland habitats some distance
removed from the channel will affect species composition of that
area|s plant and animal life. The reviewer will find in the
section which follows information on sources of impacts in areas
affected directly and indirectly by channelization. Table IV-9
provides an overview of land uses and impact considerations.
Impacts on Riparian Habitat and Land Use. The distinction be-
tween "habitat" and "land use" is blurred by the interrelationship
of defining criteria. Species diversity, ecosystem stability, and
carrying capacity are biological parameters dependent upon land
uses; land uses, on the other hand, whether they be recreational,
agricultural, or residential are associated with and reflective
of the biological productivity of the area in question.
Riparian habitats and land uses are closely associated with
the channelized water body. Changes to the streambank have an
effect upon water quality and aquatic ecology and, conversely,
changes in water quality and ecological parameters within the
stream influence habitats and land uses alongside channel banks.
As was described in the preceding section (IV.B) the clearing
of bankside vegetation induces not only accelerated erosion on
unprotected slopes but also changed patterns of light intensity
upon the water and temperatures within the stream. Such influences
may have impacts upon aquatic plant and animal life such that, for
example, coldwater species of fish are reduced or disappear, warm-
water species supplant coldwater species, shade-tolerant vegetation
is replaced by species preferring open sunlight, or whole popu-
lations of aquatic organisms are severely reduced by the absence
of protective cover or the depletion of nutrients (e.g. the detritus
derived from overhanging vegetation on which some aquatic organisms
depend) previously provided by riparian life.
Changes in water quality and hydraulic parameters, occurring
as a result of channelization, may bring about changes in species
composition of streambank vegetation. A change in groundwater
levels usually to lower elevations may be a strong influence
upon vegetational changes alongside channelized streams. Plant-
soil moisture relationships are thereby changed and plants more
tolerant of xeric conditions may invade the area, or growth rates
of existing species may be affected. Species more tolerant or
less tolerant of pollution levels may replace those which were
compatible with the preproject water quality parameters. Changes
in stream velocities may cause changes in bank stability and therefore
IV-70
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Table IV-9. Overview of Channel-related Land Uses and Potential
impacts on Terrestrial and Aquatic Systems
Impacts Measured Principally on;
Terrestrial Water Quality and Aquatic
Ecosystems:
Induced Land Use Changes to:
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in the kind and/or maturity of plants and animals preferring such
riparian niches. The height of flood waters, their frequency, and
duration will have additional influences upon both plant and animal
residents in riparian areas. Similarly, the construction of low-
flow notches or grade-control structures may change water levels
for specific stream segments with the result that riparian habitats
are either created or destroyed.
Riparian habitats exist for aquatic, amphibian and terrestrial
animals. Such habitats provide not only food for these species"
but shelter and protective cover. Disturbance or removal of this
habitat by excavation, burying with spoil materials, clearing,
or bank-stabilization measures introduces new factors in the
area's population dynamics as, for example, in changing predator-
prey relationships or limiting food supply. These impacts, though
not always easily identified as to specific cause and effect, should
be recognized as potentially significant influences on a terrestrial
ecosystem.
Insofar as impacts upon, or changes to, riparian environments
influence person-related activities {e.g. recreation, agriculture,
and urbanization) the distinction between direct and indirect
impacts is easier to perceive. The cutting-off of a meander,
for example, may induce an increase in recreational activities
(e.g. marinas and vacation homes) along the banks of the abandoned
meander. This, in turn, may have far-reaching effects upon other
socioeconomic supply and demand factors in the region as well as
on the ecology of both the channelized and abandoned stream seg-
ments. In another instance, the building of access roads for
construction and maintenance of the channel may open up previously
undisturbed lengths of streambank to fishermen, campers, or lumber-
ing operations. Again the impact may be principally an indirect
one, increasing in severity years after the project has been com-
pleted. Or, in an urban setting, the channelization of a stream
may result in a renewed emphasis on aesthetic values and water
quality when dumps, derelict or decayed buildings are exposed to
public view thus motivating concerted efforts to improve the en-
vironment alongside the channelized stream.
The reviewer should also note the potential impact of downstream
flooding which may be caused by the debouchment of the channelized
discharge into a stream channel section incapable of safely passing
the increased volumes of water.
Impacts on Wetland Habitat and Land Use. It has been recog-
nized by a growing percentage of the public in recent years that
wetlands have a uniquely and irreplaceably important value in
sustaining terrestrial and aquatic ecosystems. Because wetlands
are of such diverse types the nomenclature has traditionally em-
braced other terms still technically nonspecific such as:
meadow, marsh, pothole, swamp, and bog. Classification schemes
now being proposed are reportedly more precise and more acceptable
to both generalists and specialists.50 Wetlands may be coterminous
with other areas characterized as bottomlands and floodplains;
T1T_ -7 1
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they may also be found at higher elevations in association with
the headwaters of streams. Water levels of wetlands may be rela-
tively constant or vary seasonally; they may contain fresh,
brackish, or saline waters. But in any case their value is that
of a food source and nursery upon which ecosystems are essentially
dependent. In addition, wetlands serve as natural storage areas
for floodwaters, as recharge and discharge reservoirs for ground-
water volumes, as natural water-quality treatment systems for
the degradation of such hard-to-handle pollutants as oil and
chlorinated hydrocarbons, and for the removal of excessive amounts
of such eutrophying nutrients as phosphorus and nitrogen.
Wetland drainage can be expected to lower groundwater levels
as drained areas dry out. A shift in vegetational species will then
gradually occur, followed by a change in resident wildlife species
better adapted to the invading dryland vegetational types. In
many cases drainage projects have decreased the diversity of both
vegetational and animal species over extensive areas.51 it is
especially important for the reviewer to note, in this regard,
that wetlands are hospitable environments for many of the floral
and faunal species regarded as both rare and endangered.
Channels which pass through or alongside wetlands areas
may have the unintended effect, because of either channel design
or location of adjunct features (e.g., berms or spoil banks), of
restricting or preventing periodic inundation and replenishment
of adjacent wetlands. Such unintended effects may be extraneous
to the project's purpose but the reviewer should appraise the
likelihood of such occurrences and resultant damage to the nourish-
ment of wetland areas.
The issue of impacts to bottomland hardwoods was one singled
out for appraisal in the study52 of existing channelization con-
ducted for CEQ. That study found these impacts to be most serious
in lowland deciduous forest stands where water is in abundant supply
(i.e., wetlands) especially in the humid areas of the southern
states. And the impacts were traceable to induced changes in land
use which made the sequence of drainage, clear-cutting of bottom-
land forests, and conversion of the once-forested areas to agri-
cultural cropland an economically attractive undertaking. Though
the magnitude and extent of such inventoried land use changes are
now largely a matter of historical record and unlikely to be repeated
at anywhere near the same scale, the ecological implications are
clear and applicable even to the small-scale and indirect effects
which might occur today. Not only were soil-water conditions much
changed in these once-forested areas with resultant impacts on
elements of the hydrologic cycle (e.g., runoff and transpiration)
but soil stability was impaired, wildlife habitats were destroyed,
and diverse vegetation species were replaced by monocultured crops
(e.g., soybeans, rice, and/or corn).
Coincident with drainage and/or flood reduction measures which
have an impact upon wetlands may be the construction of access
IV-7 3
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roads, some of which may be along spoil banks. Construction and
subsequent use of these roads, in an area previously undisturbed,
by recreational and exploitative activities may be a serious source
of environmental impacts. Harvest and removal of timber in wetlands
and floodplains may result in increased volumes of runoff and
higher levels of both turbidity and nitrates in the waters of
nearby watercourses.
Wetlands, when drained, may become highly flammable. Dense
vegetational mats, no longer nourished by high water tables, may
die and dry out. In addition, the organic soils of wetlands may
include thick deposits of peat. Fires started in such areas may
not only destroy resident wildlife and their habitat but inhibit
the establishment of successional vegetative stages; fire, once
started, may also be beyond the capability of local authorities
to control.
Migratory birds, especially waterfowl, are notable users of
wetlands on a seasonal basis. Such areas may serve either as
transient resting places or as places of longer residence, depend-
ing upon their location along regional flyways.53 The reviewer
should note the significance of wetland disturbance or reduction
not only to the migratory patterns of birds but to those species
of aquatic life which have life cycles dependent upon natural
and seasonal fluctuations of water levels for spawning runs, the
development of eggs and juveniles, and then, at subsequent high
water levels, the re-introduction of new generations to the water-
ways of the region.
The emplacement of spoil and dredged materials in wetlands
adjacent to a channel will have the effect of destroying one kind of
habitat and replacing it with another. The environmental impli-
cations of spoil placement are dependent upon the relative signi-
ficance of the proportional changes in habitat composition in the
project's locale. The addition of nutrients derived from dredged
materials may add appreciably to the nutrient loading of the wetland
in which they are dumped.
Though wetland drainage projects are not undertaken for the
primary purpose of bringing additional land into cultivation54 but
rather to enhance the productivity of existing cropland, privately-
installed or non-Eederally supported tributary channels and
drains connecting with the main channels may, in fact, have this
result. The resultant effects are measurable not only as habitat
changes but as changes in land use. Oftentimes these changes are
not in type but in degree or intensity from poor pasturage, for
example, to good pasturage or from marginal timberland to exploitable
forestland. The reviewer should be careful lest these potential
effects be characterized either generally or simplistically, as'
solely beneficial or adverse. These effects should be judged in
the context of the project-specific antecedent conditions, existing
potential for the area's soil types, vegetational species and wild-
life species to be affected, predicted regional economic and land
IV-7 4
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use implications (e.g. for water quality), and other relevant
factors. It is important therefore that the reviewer find ade-
quate descriptive material in the EIS on terrestrial ecosystems
and the likelihood of induced land use changes so that resultant
impacts may be adequately assessed.
Impacts on Upland Habitat and Land Use. Terrestrial impacts
caused by channelization in upland areas may be as diverse as those
taking place in riparian and wetland areas. Structural elements
such as upland floodwater retention or retarding devices, check
dams, drop structures, and deflecting wings are as appropriate in
some upland situations as are land treatment measures in head-
waters areas under other circumstances. Though water quality con-
ditions in headwaters are generally of high order and upstream aquatic
biota more sensitive to degraded conditions than are the species
found farther downstream there are not the same differences in
degree of sensitivity between terrestrial ecosystems in upland and
bottomland areas; both systems are, in a general sense, equally
sensitive.
One other generalization to be made is that because of the
dendritic or branching tributary patterns of channelized systems
larger channels are usually found in the lowlands and smaller ones
in headwaters areas. Many smaller tributary channels are privately
(i.e. non-Federally) installed by landowners and drainage districts
during or after Federally-funded projects are completed.
Upland habitats, in general, may be classified as either agri-
cultural or forested lands. Habitat alteration as a result of the
implacement of structures can, in both cases, be characterized
and quantified in degree by the impact to acres of land cover,
species of wildlife and vegetation lost, and crop or timberland
productivity foregone as a result of the area occupied or impact-
ed by the structure.
Structures which serve to impound upstream water will have
an impact upon both surface and groundwater regimes. Upland areas
are often recharge areas by virtue of their elevation, and the
retention of water over aquifer recharge zones will increase
groundwater volumes in areas underlain by that aquifer. The in-
stallation of a structure with consequent impacts upon groundwater
levels may gradually change soil-moisture conditions so that vege-
tation changes take place and terrestrial ecosystems are affected.
In some situations an upland impoundment area may thus, in time,
be changed to become a wetland.
Impoundments of surface waters in upland areas will also have
an impact upon downstream wetlands and riparian areas as well as
in-channel aquatic ecosystems. The release of impounded waters may
or may not be on a predictable schedule. If streamflows are appreciably
diminished this will have ramifying effects on downstream ground-
water conditions and the terrestrial systems supported by such under-
ground resources.
IV-7 5
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Land treatment measures are undertaken in upland areas to
improve soil conditions and the vegetation growing thereon, reduce
erosion, improve drainage, and prevent flooding. These practices
are sometimes required as adjunct to and conditional for the
installation of structural features (e.g. channels) in a watershed
management project. Some of these measures are:
crop rotation practices
planting of cover crops
contour farming
-- crop residue utilization
field terracing
subsurface tiling
land grading
grassed waterways
farm ponds
fence row plantings
forestry improvement practices
wildlife area improvement
Upland land treatment measures, in many cases, are
arranged with local "cooperators" and their installation or imple-
mentation, in the strictest sense, is not the responsibility of the
initiating agency. Their net impact on systems is intended as
beneficial even though component negative impacts may be identified.
The reviewer should be especially sensitive to situations in
which dowhstream channelized flood protection, for example, is
contingent upon upstream flood management practices such as
floodplain zoning. The implementation of zoning restrictions is
beyond the jurisdictional authority of Federal channel-building
agencies. The issue raised in such situations, however, typifies
the classic "upstream-downstream" conflict and involves questions
of equity, compensation, etc. rather than those of ecosystem im-
pact assessment. Land use questions, particularly when a channel-
ized stream traverses jurisdictional boundaries, as it often does
when impacts to both upland and lowland areas can be anticipated,
are complex and seldom as easily resolved ^as third parties would
like them to be.
Though they apply equally to riparian, wetland, and upland
habitats the indirect terrestrial impacts of channelization may
be felt beyond the region of physical influence. Drainage of
wetlands, for example, may adversely affect migratory patterns
and even population statistics of waterfowl.55 The installa-
tion of upland impoundments, on the other hand, may have the
opposite effects on these same biotic systems extending beyond
the project's perimeter. In addition, land modification to terres-
trial habitats in any location may cause a shift in overland migra-
tion routes of animals, the impacts of which are felt at considerable
distances from the project itself. Impacts of this sort (direct and
indirect) are also measurable in human socioeconomic terms as
in the case of dislocation of corridors for transportation and
other utility services. Similarly, recreational opportunities and
development potential, even though not expressly specified as pro-
ject purposes, may have complex interactions with supply and de-
-------
mand factors measurable over wide areas. The reviewer, therefore,
should be sensitive to the possibility of indirect and induced
impacts which are subtle and/or cumulative and measurable only
in a regional context.
IV.C.2. Review of Impact Quantification
Guidelines for the quantification of impacts upon terrestrial
ecosystems and also for aquatic systems (see IV.B.2), must
necessarily be generalized because each project area is distinctive
and characterized by different dimensions, adjacent land uses, and
ecological values. Yet it is these distinctive categories (i.e.
project dimensions, land uses, and ecological values), quantifiable
for all projects, upon which the reviewer must focus. Changes in
these characteristics from pre-project to post-project status
(i.e. as envisioned and described in the EIS) should receive the
reviewer's attention.
In many cases only qualitative estimates, rather than quantita-
tive ones, can be made. This may be either because predictive tech-
niques for quantitative measurements in ecosystem changes,
for example are not sufficiently developed, or because induced
and indirect impacts of land use changes, for instance are,
in themselves, dependent variables.
Impacts Dependent Upon^ Project Dimensions. Descriptive material
in the EIS will, or should, contain definition of both lateral
and longitudinal dimensions of the project. The confines of the
project within which construction, operational, and maintenance
activities will take place therefore should be apparent to the EIS
reviewer.
Both the characterization of land cover and the current land
use practices which are to be directly affected by installation of
the channel and adjunct facilities (e.g. access roads, tributary
drains, borrow pits, spoil banks, etc.) should be described in the
EIS and if they are not, the reviewer should find the absence
of such information cause for critical comment. Areal coverage
should be definable and perhaps even classifiable according to a
systematized inventory. Though the EIS may not provide sufficient
areal distinctions nor details to allow the reviewer to identify
mappable categories of land cover, it should be sufficiently
explicit to allow the reviewer to estimate: 1) the relative sig-
nificance of different types affected by the project, and 2) the
proportional changes in these categories expected to occur after
the project is installed. From such approximate quantifications,
impacts may be estimated so that their significance can be evaluated.
A suggested inventory classification might include:
- agricultural and open lands - mining or waste disposal areas
- forest lands - urban lands
- wetlands - outdoor recreational facilities
IV-7 7
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The above classification can be adapted to reflect appropriate
regional categories of land uses, vegetational types, and the nature
of the land itself. The categories may be further refined to
emphasize significant sub-categories. Under agricultural land,
for example, distinctions may be made between: tilled, abandoned,
pastured or range land.
Impacts upon productive forest and cropland may be quantified
not only in acres gained or lost but in increased or decreased
yields e.g. bushels or cords per acres. (Many EIS's treat
this subject under "socioeconomic" rather than "environmental"
sections; quantification may also be addressed in EIS's when com-
paring "alternatives to the proposed action.")
The productivity of wetlands is difficult to assay only
one of the reasons being the ecological differences between wet-
land sites. Nonetheless the high productivity and ecological
values associated with wetlands are generally recognized by
ecologists and others. (Southern swamps, for example, are esti-
mated to yield an average gross primary energy production of 20,000
kilocalories/square meter/year an output ranking them with such
other extraordinarily productive ecosystems as those found at
coral reefs and in estuaries.)56
It is important that the EIS contain, however, sufficient
descriptive information on project-affected wetlands to make
possible assessments of impacts in terms of acres lost or
gained. And it will be of significant aid to the reviewer if
material is available in the EIS enabling the distinction between
types of freshwater wetlands.57 A generalized classification of
the sort still being used might be the following:
- Wet meadow: Vegetation is primarily grasses,
rushes and sedges; surface water
is present only seasonally.
- Marsh: Characterized by some open water,
and emergent vegetation.
- Swamp: Waterlogged soils with some
standing water; vegetation is
mostly woody shrubs and trees.
- Bog: Characterized by mats of sphagnum
moss in waterlogged soil; vege-
tation contains shrub thickets,
black spruce, tamarack and red
maple.
- Seasonally flooded flatland: Floodable land usually adjacent
to streams; often without sharply
distinctive vegetational character.
IV-7 8
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The reviewer who is able to make generic distinctions between
the above kinds of freshwater wetlands described in an EIS is there-
by enabled to better appraise a channel project's impacts upon
wetlands. Generalized criteria which may then be applicable to
impact measurements in wetlands are some of the following:
- Diversity and dominance of wetland types:
The greater the mix of wetland types in an area, the
higher the value attached to a wetland type of rare
occurrence; dominance of marshes and/or swamps, as con-
trasted with meadows and open water, results in greater
numbers of inventoried wildlife and vegetational species.
- Diversity of wetland biota:
Inventories of biota are indicative of wetland diver-
sity; the greater the diversity of wetland types, the more
diverse the- species of plant and animal life; diminished
diversity of wetland types will have a corresponding im-
pact on resident biota.
- Character of wetland:
The patterned arrangement of vegetation so as to cause
maximum interpersion of vegetational species and increase
the benefits of "edge effects" will enhance habitat
values and increase diversity of resident aquatic and
terrestrial species; -a concentric arrangement of vege-
tational growth around open water in a marsh, for example,
is less to be desired than a random interspersion of
clumps and thickets of vegetation throughout the marsh.
- Wetland site:
Wetlands associated with lakes and streams are more
valuable than isolated ones; and wetlands which are inter-
connected one with another increase habitat and species
diversity especially if they are of different types;
wetlands located in lowlands generally have a richer
substrate than those in the uplands.
- Wetland size:
Habitat utilization is correlatable with wetland size
small wetlands {less than 25 acres) are more valuable
on a per acre basis for waterfowl nesting than large
ones, and large ones are more attractive as resting
places for migratory waterfowl; diversity, in general,
is correlative with size; but the context and local, or
regional, frame of reference is of importance in adjudging
this wetland parameter.
IV-79
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- Adjacent land types:
Diversity of type of surrounding areas (forest, crop-
land, saltwater bay, etc.) increases species diversity
within the wetland.
- Wetland water chemistry:
Hard and/or alkaline waters produce a greater value and
diversity of nutrients than do soft or acidic waters.
The reviewer will usually have to be judgmental in assigning
relative and qualitative values to impacted wetlands. Such values
are also dependent upon interpretation of the descriptive environ-
mental data presented in the EIS and the local or regional signi-
ficance assigned to wetland areas.
It is important that the environmental values of wetlands not
be confused with commercial or income-producing classifications.-58,59
Impacts upon urban and recreational lands caused by channeli-
zation are often easier to quantify than those on other lands because
of social and institutional interests in lands of these types and
because of specifications, in project designs and plans, of the
options, variable consequences, and the detailed cost projections
of project installation. Terrestrial ecosystems in urbanized
areas are principally riparian and it is important that the
reviewer be able to identify and estimate the extent and dimension
of riparian habitats. (Even the numbers of trees may be estimated
in the EIS and a portion of the impact thereby more easily quanti-
fied.) The reviewer should be critical of scheduled removal
of vegetation and other natural materials (during construction
and maintenance) , especially that which is justified solely to
provide greater freedom of movement for equipment.
Riparian lands in urbanized areas not only have a special
value as wildlife habitat but more especially serve to enhance
aesthetic values. The textural (land vs. water) and landform
(elevational) contrasts are important aesthetic elements along a
streambank, as is the element of naturalness. Interference with
or disruption of these elements should be minimized if pleasing
landscapes are to be maintained in an urban environment. And the
reviewer's task is to be critical not only of impacts attributable
to unjustifiable lateral extension of the project but of physical
design standards which conflict with aesthetic standards.
Impacts Dependent Upon Land Use and Ecological Values. Most
channel projects are undertaken either: 1) to drain excess waters
from areas where the presence of such waters is inimical to present
land uses, or 2) to prevent the periodic incursion of flood waters
into areas where they will cause damage to existing property values.
Land use categorization therefore is an integral part of impact
quantification.
IV-80
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It is important that the EIS differentiate between existing
land uses and those forecast for post-project periods. Quantifi-
cation of the former is more easily accomplished than for the anti-
cipated future because of implicit and influential uncertainties.
Such uncertainties include: changes which might occur in volumes of
and market prices for agricultural products, growth-induced changes
in residential, commercial and industrial land development patterns
and optional plans and programs which may be instituted by local
and regional institutions. Moreover, the time frame within which
cumulative impact quantifications are to be estimated is usually
not specified, though such periods of analysis can be expected
to have relevance to the "useful" life of a project.60
,>
Categorization of land has already been touched upon in the
preceding subsection ("Impact Quantification Dependent Upon Project
Dimensions") where an inventory classification of land types was
suggested as a means of differentiating between and quantifying the
effects upon nearby lands. In addition to the categorization of
land types specific land uses may also be classified within a
project area or within an area which may feel the impact of
a channel project.
The rationale for categorization, whatever system, is to
quantify the impacts of a project so that a degree of impact
significance may be assigned the project. Pre- and post-project
assessments are thus possible and attention can then be focused
on critical categories as these are defined in a local or
regional context.
mat:
Land use categories may be classifiable under the following for-
Residential
(by zoning classification)
Commercial
Essentially free-standing
stores
Shopping Centers
Industrial
Light manufacturing
Heavy manufacturing
Transportation
Mass transit facilities
Highway
Others
Recreation
Intensive
Passive
Spectator-oriented
Public Utilities
Petroleum products
Water and sewer
Electric
Public & Historic Buildings
Agriculture
Extensive (pastured or mowed)
Intensive (tilled)
Forested
Vacant Land
Conservation restricted
Cleared but abandoned
Water Bodies
Lakes and impoundments
Flowing water
Wetlands
-------
The EIS may not contain inventoried land uses outside of the area
defined by a project's perimeter. The reviewer is advised that such
regionally relevant inventories may be available, however, in reports
of regional planning associations, river basin studies, Section 208
planning studies, transportation studies, and the like. It is
possible, therefore, that project-related land use impacts, as
described in or inferred from an EIS, may be better appraised in an
appropriate and critical context when compared with other published
documents on land utilization.
Criteria for land use impact quantification and evaluation, in
the final analysis, are both economic and ecological. Economic
criteria as they relate to terrestrial ecosystems are applied to
measures of productivity--anticipated increases (or decreases) in
yield or the expected changes-in land values reflected by "higher"
(or "lower") levels of "usefulness" to society. The reviewer is
cautioned that the emphasis on such measures heavily prejudices
impact quantification in favor of income-producing resources while
overlooking less easily quantifiable resources or values for which
measures of worth are less well understood or appreciatedJ61 Also
often overlooked as a result of this approach are the values of
future options.
The ecological values of terrestrial ecosystems have been
addressed in earlier parts of this sectionthe contribution of
riparian vegetation to water quality and aquatic ecosystems, the
nutrient values of wetlands, and the replenishing functions of
uplands. These values are not easily quantified in terms
customarily applied; they are dependent upon regional concepts of
scarcity, need and demand expressed by both measures of ecosystem
functions and definitions of politically oriented issues.
Wildlife habitat values, species diversity (of plants and
animals), and levels of productivity are elements which the reviewer
can only qualitatively appraise in areas adjacent to a channelized
stream. And project-related impacts which on balance are beneficial
and non-degrading ones may result from and be appraised for such
purposeful management programs as wildlife management, reforestation,
and water quality improvement (e.g. with land treatment measures).
Wildlife management programs that are on a put-and-take basis are
differently valued than are those emphasizing habitat improvement or
protection. And reforestation that has as its purpose the re-
establishment of growing stock in areas once ravaged by fire is
different from enhancement of watershed areas with plantations of
conifers. Land treatment measures in areas of high relief are more
significant than those in more gently rolling tilled areas. Impact
appraisal in such cases is subjective and it is the reviewer's task
to insure that such appraisals are reasonable, comprehensive, and in
the context of the project being addressed.
Impacts, including those related to project installation and
operation but induced and stemming from the encouragement or
IV-8 2
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introduction of new or intensified land uses, may be less easily
appraised. As was earlier noted these impacts, although traceable
to land-based activities, are in most cases transferred to water
systems. (See Table IV-9*) There the impacts can be quantified
in terms of the standards and criteria of water constituents or
water quality parameters. The reviewer's responsibility therefore
is to be sure that impacts traceable to land-based activities and
induced land changes are properly addressed as ecosystem impacts.
IV.C.3. Assessment of Impacts
An assessment of the anticipated impacts to terrestrial
ecosystems should relate identified sources and degrees of impacts
to the capacity and ability of the land and its biota to sustain
or recover from those impacts. Established or mandated limits to
terrestrial impacts are usually not quantified specifically but
instead are estimated in relation to resource scarcity, resource
demand schedules and projected cumulative impacts. Mitigating
measures as well as alternative means of meeting proposed project
objectives should be included in the EIS and reviewed in the assessment-
such measures to include changes in project scope and channel
dimensions as well as redesign or relocation of'project elements; and
project alternatives to include both structural and nonstructural
solutions to the water resource problem for which channelization is
being proposed. The reviewer's task in impact assessment therefore
involves judgment on both the adequacy of the definitions of
anticipated impacts described in the EIS and the comprehensiveness
of the considerations by the initiating agency to reduce these
impacts to minimum and acceptable levels.
Impacts on Biota. Ecological impacts should be considered in
as broad a context as possible. Interdependences of plants and
animals at the land-water interface are especially important in
sensitive riparian and wetlands environments. Species productivity
and diversity are dependent in such places on water quality, water
levels and soil or substrate conditions. Criteria exist for water
quality parameters on toxicity and pollutant loadings, for example,
which are pertinent to the productivity of marsh vegetation. The
reviewer's task therefore is to relate, wherever possible, quantifiable
impacts (see Sections IV.A.2 and IV.B.2) to resource values. Habitat
values for indigenous waterfowl, terrestrial animals, and vegetation
can be related to acreages and intensity of modification. But
judgmental assessments of relationships between direct or indirect
impacts and ecological productivity and diversity must be the basis
for the reviewer's critique in most instances.
Wetland drainage must be assessed not only for impacts on the
species composition of resident biota but for reduction of natural
flood storage and lowering of groundwater levels. Those impacts, in
turn, affect recharge potential, consequent low flow volumes in
streams, and eventually water quality parameters. Flood storage
effects must be assessed in the context of damage potential to areas
IV-8 3
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downstream from the impacted wetland.
Alteration of riparian areas may result in vegetation losses
with resultant effects on both animal habitats and food sources as
well as impacts upon components of aquatic ecosystems. Some of the
aquatic effects may be quantifiable estimates (e.g. turbidity values
and thermal effects) whereas most terrestrial effects will be less
well defined in the EIS (e.g. species productivity and nutrient source
availability). The reviewer should* assess the completeness of impact
identification and supporting baseline or inventory, data to determine
the significance of a channel's modification to existing (or potential)
environmental values. "Significance" may be related to acres of
riparian areas modified as a percentage of total streambank area or
to locations of impacted areas relative to the patterns of diversity
and productivity of similar environments in or near to the project
area.
Estimations of the regenerative potential of impacted areas
should be part of an assessment. Construction and maintenance
activities should be viewed therefore in the context of project
schedules, timing and frequency of occurrence, and scope of operations.
Activities scheduled during vegetative dormant periods, for example,
are less serious than at other times. Selective removal of
vegetation instead of clearcutting, and identification and
preservation of rare species result in less serious impacts on an
ecosystem. Distinctions between installation of some structural
elements (e.g. rip-rapping, berms, and abutments) and others less
environmentally disturbing (e.g. subsurface drains, and diversion
terraces) should be noted and related to the permanence and severity
of their impact.
Some rare and endangered species have their last refuge in
undisturbed wetlands. It is important that the EIS contain assurances
that species inventories at the project site have been compared with
lists of rare species compiled by the U.S.Fish and Wildlife Service
and the appropriate state agencies so that irreparable environmental
consequences are avoided.
The context in which impacts to migrating animal species are
evaluated often requires that relevant information of a regional
and even continental (in the case of some waterfowl)scale be
included in the EIS.
Impacts on Land Uses. Land use implications traceable to channel
modifications are both direct and indirect, immediate and induced.
Guidance for review of assessments of those impacts may be found in
Section IV.C.2.
The EIS may or may not make distinctions between site-specific
impacts and those felt beyond the boundaries of the project. However
they are addressed, both should be included. Recreation, agriculture,
commercial and residential uses of land are essentially related to
interwoven social, economic, and environmental values. These values
change and so, in response, do land uses, with notable changes in
IV-8 4
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emphases on: recreational styles and demand, crop selections and the
intensity of agricultural enterprise, land settlement or development
patterns. Boundaries of resultant impacts are seldom coincident with
project boundaries. The reviewer, in evaluating complex interactions
of value changes and land uses, and the impacts thereafter anticipated
must find in the EIS an overview of pattern changes that have already
taken place and data from which future changes can be estimated.
International grain market fluctuations, for example, may make soybean
cultivation on marginal land temporarily much more attractive than
the raising of hay. This sort of change in crop selection may have
impacts on sediment runoff, fertilizer application rates, and wildlife
habitat values. Impairment or improvement of fishing and hunting
opportunities at the project site may create changes in land use
intensitieseven on land somewhat removed from the project--with
resultant impacts on access roads, second-home development patterns,
and the provision of utility services. Local and regional population
projections may presage other kinds of land use changes. It will be
up to the reviewer to assess the comprehensiveness with which the EIS
evaluates such potential impacts.
The installation of a drainage channel may induce landowners and
other private interests to construct adjunct drainage facilities tying
in with the subsidized project. Both the EIS and the reviewer should
be sensitive to the likelihood that this may happen.
Flood management measures, both structural and nonstructural,
have land management implications. In the absence of local
development restrictions the installation of damage-reducing
measures may induce occupation of floodplains to a degree exceeding
the scope of designed protection. This possibility falls within the
purview of both the EIS and the reviewer of impact assessments.
The subject of aesthetics is closely related to land use.
Criteria applicable to assessments of impacts upon aesthetic values
do not exist. Nonetheless, local and regional standards may be
estimated from a consensus of reactions to similar projects and from
public discussions. Criteria also can be related to the degree of
change anticipated from preproject conditions, proximity of interest
parties to a project, and the areal extent or severity of a channel's
modification. It is important that attention by paid to the impacts
measured by aesthetic values because, though non-quantifiable, such
values are often firmly held and strongly defended.
Alternative and Mitigating Measures. Selection of alternative
measures is strongly influenced by economics. In addition,
engineering options include choices ranging from clearing and
snagging to deep channel excavation, with correspondingly ranked
impacts on lands adjacent to the channel. Levees, floodways, upstream
flood retention dams and land treatment measures are alternatives to
accomplishing the purposes of channelization in some cases and adjunct
to othersespecially where relocation or mitigcition of impacts is
desired.
Nonstructural measuresprincipally to reduce flood damagesare
IV-8 5
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classifiable as regulatory, technical-administrative, or economic-
financial. Each of these measures involves programs, policies, and
funding stratagems specifically tailored to project specifications
and institutional responsibilities. (An extensive discussion of
applicable nonstructural alternatives may be found in the ADL Report. )62
Mitigating measures aimed at alleviating impacts to terrestrial
systems are related to those affecting water quality and aquatic
ecology impacts (see Table IV-7, Section IV.A.3.) These measures are
specifically addressed in a number of relevant EPA publications 63
on the subject of land-disturbing activities. The reviewer should
also consider the need for substitution or enhancement of resources
outside of project boundaries when the proposed project destroys or
degrades resources of appreciable public value within the project
area.
Many mitigating measures have relevance to enhancement of
animal and vegetative habitat. Spoil banks, for example, instead
of being smoothed down or leveled may have value as animal habitats
when left undisturbed but planted with appropriate and soil-binding
vegetative materials. Restriction of excavation to one side of the
channel and the resultant distinction between habitats on opposite
sides of a channel may increase habitat diversity. The use of
bankside spoil to create or enlarge abutting wetlands may also be an
option.
The reviewer must be imaginative in appraising the environmental
data contained in an EIS, the impacts anticipated, and the opportunities
presented for impact mitigation. Value rankings attached to
terrestrial elements such as rare or valuable species of trees (e.g.
walnut and pecan) or wildlife species (e.g. ospreys or eagles) if
not explicitly enumerated in EIS inventories should be sought by the
reviewer as a guide to impact assessment.
IV-8 6
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REFERENCES CHAPTER IV
1. U.S. EPA, Office of Federal Activities, Guidelines for
Review of Environmental Impact Statements/ Volume III, Impoundment
Projects, November 1975.
2. Arthur D. Little, Inc. and Philadelphia Academy of Natural
Sciences, Report on Channel Modifications, Volume I, submitted
to the Council on Environmental Quality, U.S. Government Printing
Office, March 1973, p. 150.
3. Arthur D. Little, op. cit., Volume II, p. 15-15 and 15-16.
4. U.S. Department of Agriculture, Soil Conservation Service,
Engineering Division, Planning and Design of Open Channels,
Technical Release No. 25, revised March 1973, p. 1-3.
5. U.S. Department of Agriculture, Soil Conservation Service,
National Engineering Handbook; Section 4, Hydrology, Washington,
D.C., August 1972.
6. U.S. Department of the Army, Corps of Engineers, Routing of
Floods Through River Channels, Engineering Manual EM 1110-2-1408,
1960.
7. U.S. Army Corps of Engineers, HEC-1, Flood Hydrograph Package -
Users Manual, Computer Program 723 X6-L2010, Hydrologic Engineering
Center, Davis, California, January 1973.
8. U.S. Army Corps of Engineers, HEC-2, Water Surface Profiles -
Users Manual, Computer Program 723-X6-L202A, Hydrologic Engineering
Center, Davis, California, February 1972.
9. Chow, V.T., Handbook of Applied Hydrology, New York, McGraw-
Hill Book Company, 1964.
10. Chow, V.T., Open Channel Hydraulics, New York, McGraw-Hill
Book Company, Inc.,1969, p. 165.
11. Fortier, S. and F.C. Scobey, "Permissible Canal Velocities,"
Transactions of the American Society of Civil Engineers, Vol. 89,
1926, p. 940-956.
12. U.S. Department of Agriculture, Soil Conservation Service,
Technical Release No. 25, Chapter 6.
13. Einstein, H.A., "The Bedload Function for Sediment Transportation
in Open Channel Flow," USDA Technical Bulletin No. 1026, September
1950.
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14. U.S. Army Corps of Engineers, Scour and Deposition in Rivers
and Reservoirs, Hydrologic Engineering Center, Davis, California,
1974.
15. Subcommittee on Sedimentation, Interagency Committee on Water
Resources, Measurement and Analysj-s of Sediment Loads in Streams,
Report No. 14, "Determination of Fluvial Sediment Discharge,"
December 1963, 151 pp.
16. Hynes, H.B.N., The Ecology of Running Waters, University of
Toronto Press, 1970, p. 210.
17. Cooper, D.C., et al., Review of Environmental Impact Statements
Associated with Stream Channelization Projects, for the U.S.
Environmental Protection Agency (Contract No. 68-01-2905), October
1975.
18. Brown, G.W., Predicting Temperatures of Small Streams,
Water Resources Research, Vol. 5, No. 1 (February 1969), pp. 68-75.
Or: School of Forestry and School of Engineering, Oregon State
University, Studies on Effects of Watershed Practices on Streams,
U.S. EPA, Water Pollution Control Research Series, Grant No. 13010 EGA
February 1971, p. 15-24.
19. Technical Advisory and Investigations Branch, Technical Services
Program, FWPCA, Temperature and Aguatic Life, Laboratory Investigations
No. 6, Cincinnati, Ohio, December 1967, 151 pp.
20. USDA, Soil Conservation Service, National Engineering Handbook,
Section 4, Hydrology. See especially chapters 7-10.
21. Brater, E.F., and J.D. Sherrill, Rainfa.ll-Runof f Relations on
Urban and Rural Areas, U.S. EPA, Cincinnati, Ohio, National
Environmental Research Center, Office of Research and Development,
May 1975 (EPA-670/2-76-046).
22. Uttormark, P.O., J.D. Chapin, and K.M. Green, Estimating
Nutrient Loadings of Lakes from Nonpoint Sources, prepared for
Office of Research and Monitoring, U.S. EPA, Washington, D.C.,
August 1974 (EPA-660/3-74-020).
23. Omernik, J.M., The Influence of Land Use on Stream Nutrient
Levels, U.S. EPA, Office of Research and Development, Corvallis
Environmental Research Laboratory, Corvallis, Oregon, January 1976
(EPA-600/3-76-014).
24. U.S. Department of Agriculture, Soil Conservation Service,
Engineering Field Manual for Conservation Practices, Washington,
D.C., 1975, pp. 4-15 to 4-19.
IV-8 8
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25. Ibid.
26. Arthur D. Little, Inc., op. cit., Volume I, p. 162.
27. Skidmore, E.L. and N.P. Woodruff, Wind Erosion Forces in
the United States and their Use in Predicting Soil Loss",
Agricultural Handbook No. 346, U.S. Department of Agriculture,
ARS, April 1968.
28. Wischmeier, W.H. and J.V. Mannering, "Relations of Soil
Properties to its Erodibility", Bulletin of Soil Science Society
of America, 33 (1), 1969, p. 131-137.
29. Dissmeyer, G.E., "Evaluating the Impact of Forest Management
Practices on Suspended Sediment", Journal of Soil and Water
Conservation, 1973.
30. Wischmeier, W.H., "Estimating the Cover and Management Factor
for Undisturbed Areas," Purdue Journal Paper #4916, Purdue
University U.S.D.A. - ARS, 1971.
31. See especially four U.S. EPA publications:
(1) Processes, Procedures, and Methods to Control Pollution
Resulting from All Construction Activity (EPA-430/9-73-007),
(2) Processes, Procedures, and Methods to Control Pollution
Resulting from Silvicultural Activities (-010) ,
(3) Methods for Identifying and Evaluating the Nature and Extent
of Nonpoint Sources of Pollutants (-014), and
(4) Methods and Practices for Controlling Water Pollution from
Agricultural Nonpoint Sources (-015).
32. U.S. EPA 430/9-73-014, op. cit. pp. 46-77.
33. Wischmeier et al., op. cit., 1969.
34. Wischmeier et al. op. cit., 1971.
35. Dissmeyer, op. cit.
36. See especially: U.S. Department of Agriculture, Soil
Conservation Service/ Engineering Field Manual for Conservation
Practices, 1975, pp. 4-18 to 4-21.
37. Van Brahana, J., "Beneath the Tenn-Tom", Water Spectrum,
U.S. Army Corps of Engineers, Winter 1975-76, pp. 17-24.
38. Walton, W.C., Groundwater Resource Evaluation, New York,
McGraw-Hill Book Company, 1970.
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39. U.S. Department of Agriculture, Soil Conservation Service,
National Engineering Handbook - Section 18, Geology, April 1969.
40. U.S. Department of Agriculture, Soil Conservation Service,
Engineering Division, Groundwater Recharge, Technical Release
No. 36: Geology, June 1967.
41. Kashef, Abdel-Aziz I., "Groundwater Movement Toward Artificial
Cuts", Water Resources Research, Vol. 5, No. 5, October 1969.
42. U.S. EPA, Proposed Criteria for Water Quality, Volume I,
Washington, D.C., October 1973.
43. Hynes, H.B.N., op. cit., p. 210-211, citing Thienemann, A.,
"Bin drittes biozonotisches Grundprinzip," Archiv fur Hydrobiologie,
49, 421-422 (1954).
44. Arthur D. Little, Inc., op. cit./ Volume I, p. 211.
45. Fryer, J.L., and K.S. Pilcher, Effects of Temperature on
Diseases of Salmonid Fishes, U.S. Government Printing Office,
January 1974 (EPA-660/3-73-020), 119 pages.
46. Arthur D. Little, Inc., op. cit., Volume I, p. 241.
47. Brown, G.W., "Effects of Forest Management on Stream
Temperature," Proceedings of the Symposium on Interdisciplinary
Aspects of Watershed Management/ August 3-6, 1970, Montana State
University, Bozeman, Montana (New York: American Society of
Civil Engineers), pp. 93-103.
48. Cooper, et al./ op. cit.
49. Sinclair, R.M., Editor/ Training Manual - Freshwater Biology
and Pollution Ecology, U.S. EPA, Office of Water Program Operations,
National Training Center, Cincinnati, Ohio (EPA-430/1-75-005),
April 1975, p. 22-4.
50. Cowardin, L.M., V. Carter, F.C. Golet, E.T. LaRose, Interim
Classification of Wetlands and Aquatic Habitats of the United
States, U.S. Department of the Interior, Fish and Wildlife Service,
Washington, D.C., 109 pp. (in press-1976) .
51. Arthur D. Little, Inc., op. cit., Volume I, pp. 213-253.
52. Ibid., 2 volumes.
53. U.S. Department of the Interior, Fish and Wildlife Service/
Wetlands of the United States, Their Extent and Their Value to
Waterfowl and Other Wildlife, Circular 39, 1971/ 67 pp.
IV-90
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54. U.S. Department of Agriculture, Soil Conservation Service,
Watershed Protection Handbook, Part I, Chapter 6, Section 106.02,
1967.
55. U.S. Department of the Interior, Fish and Wildlife Service,
op. cit., 1971.
56. Odum, E.P., Fundamentals of Ecology, W.B. Saunders, Philadelphia,
1971, 546 pp.
57. Cowardin et al., op^ cit., pp. 17-72.
58. Gupta, T.A., and J.H. Foster, "Economic Criteria for Freshwater
Wetland Policy in Massachusetts," in American Journal of Agricultural
Economics, Volume 57, No. 1, pp. 40-45, 1975.
59. Larson, J.S., "Evaluation Models for Public Management of
Freshwater Wetlands," in Transactions of the 40th North American
WiIdli fe jand_ j
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