HomeMy WebLinkAboutAPA2652General Technical Report PNW-109
July 1980
Influence of Forest and
Rangeland anagement on
nadromou s Fish Habitat in
estern meri
PLANNING FOREST ROADS
TO PROTECT
SALMONID HABITAT
CARL TON S. VEE and TERRY D. ROELOFS
(J SE
A1'4 A J)R 0ttllOUS FIS:t,l tiABIT AT
Pf�OCi RAM
U.S. Department of Agriculture Forest Service
Pacific Northwest Forest and Range Experiment Station
ABSTRACT
The construction and existence of forest roads, landings,
and decking areas may have significant effects on anadromous fish
habitat. Major ·effects discussed in this paper are increased
sedimentation from transportation netw o rks, the hindrance to fish
migration of drainage structures, and possible changes in water
quality from road stab ilization ad ditives. Guidelines and
recommendations to decrease or eliminate ad verse effects are also
given.
KEYWORDS: Fish habitat, water quality, sedimentation, road
building (forest/log ging) .
USDA FOREST SERVICE
General Technical Report PNW-1 09
INFLUENCE OF FOREST AND
RANGELAND MANAGEMENT ON
ANADROMOUS FISH HABIT AT IN
WESTERN NORTH AMERICA
William R. Meehan , Technical Editor
4. Planning Forest Roads to Protect Salmonid Habitat
CARL TON S. VEE AND TERRY D. ROELOFS
Humboldt State University, Arcata, California
1980
PACIFIC NORTHWEST FOREST AND RANGE EXPERIMENT STATION
Forest Service, U.S. Department of Agricul ture Portland, Oregon
Preface
This is one of a series of publications summarizing knowledge
about the influences of forest and rangeland management on anadrornous
fish habitat in Western North America. This paper addresses the ef-
fects on fish habitat of naturally occurring watershed disturbances
and sets the scene for future discussions of the influences of human
activities.
Our intent in presenting the information in these publications
is to provide managers and users of the forest and rangelands of
Western North America with the most complete information available
for estimating the consequences of various management alternatives.
In this series, we will summarize published and unpublished
reports and data as well as the observations of resource scientists
and managers developed over years of experience in the West. These
compilations will be valuable to resource managers in planning uses
of forest and rangeland resources, and to scientists in planning
future research. The extensive lists of references will serve as a
bibliography on forest and rangeland resources and their uses for
Western North America.
Previous publications in these series include:
1. "Habitat requirements of anadromous salmonids,"
by D. W. Reiser and T. C. Bjornn.
2. "Impacts of natural events," by Douglas N. Swanston.
TABLE OF CONTENTS
INTRODUCTION . .
SEDIMENTATION
Controlling Sedimentation Through Planning
and Design . . . . .
Road Construction and Maintenance .
ROAD STABILIZATION ADDITIVES
ROADS AND FISH MIGRATION . . .
Types of Culverts . . . . . . . .
Water Velocity in Culverts
Culvert Outfall Barriers
Structures for Debris Control .
SUMHARY ..
LITERATURE CITED
1
2
4
6
8
9
. . 13
16
• • 20
. 22
. 23
23
INTRODUCTION
A forest transportation
system can have significant
effects on anadromous fish and
their habitats. Often, the
effects have been adverse.
Examples of adverse changes
caused by forest roads, log
sorting, and log-storage areas
include increased sediment and
organic debris in streams,
changes in water quality and
quantity, formation of physical
barriers to the movement of
adult and juvenile fish, and
increased human access to
previously remote or isolated
areas.
This report describes how
elements of a forest
transportation system cause
environmental changes that
affect anadromous fish habitat
and provides guidelines for the
design, construction, and
maintenance of these facilities
to minimize adverse effects.
In the first publication in
this series, Reiser and Bjornn
have discussed habitat
requirements of anadromous
salmonids; we will limit our
discussion to effects on the
fish and their habitats that
directly stem from forest roads,
log sorting, and log-storage
areas.
l
SEDIMENTATION
The fact that forest roads
cause increased erosion and
sedimentation cannot be
disputed. Increased sediment in
streams after construction of
roads can be dramatic and long-
lasting. The incremental
sediment contribution per unit
area from roads is often many
times that from all other land-
management activities, including
:tog•skidding and yarding .. Based on total area, however, both
roads and logging appear to
contribute eroded material
nearly equally. Gibbons and
.Salo (1973) reviewed over 25
articles on the impact of timber
harvesting on stream environments
and concluded that forest roads
are the primary initiator of ero-
sio~ caused by human activities.
The primary mechanisms by
which sediment from roads
reaches streams are mass soil
movement and surface erosion.
Because forests and steep
terrain seem, for the most part,
to go together, mass-movement
erosion is the predominant mode
2
of sediment transport from
forest roads. Swanston and
Swanson (1976) described four
main types of mass movements
common to Western forest lands.
Soil creep, slump-earthflows,
debris avalanches, and debris
torrents are differentiated
mainly by speed of travel and
shape of the failure surface.
The construction of roads across
some slopes can initiate or
accelerate slope failure--from
several to hundreds of times,
depending on such variables as
soil type, slope steepness,
presence of subsurface water,
and road location (Anderson
1971, Larse 1971, Swanston 1971,
Swanson 1975, Swanston and
Swanson 1976).
The construction of a
road, landing, or log-sorting
area on a hillslope is a severe
and concentrated disturbance.
Such construction can initiate
mass movements of soil by
overloading the slope from
improper fill construction,
undercutting an already
marginally stable slope, and
impeding or changing surface
and subsurface runoff regimes
(Larse 1971, Burroughs et al.
1976). Table 1 shows how
severely roads can increase
erosion rates as indicated by
the rate of debris-avalanche
erosion in four widely separate
watersheds in Western Canada
and the United States (Swanston
and Swanson 1976). The values
shown are only for debris
avalanches and do not include
amounts from other road-
associated mass or surface
events.
Table 1--Debris-avalanche erosion in forest, clearcut, and roaded areas (Swanston and Swanson 1976).
Period of
Site record
Year Percent
Stegualeho Creek, Olympic Peninsula
Forest 84 79
Clearcut 6 18
Road right-of-way 6 3
Area
Km 2
(Fiksdal 1974)
19.3
4.4
0.7
24.4
Slides
Number
25
0
83
108
Debris-avalanche
erosion
71.8
0
ll 825
71.8
Rate of debris-avalanche
erosion relative to
forested areas
X
X
l.O
0
165
Alder Creek, western Cascade Range, Oregon (Morrison 1975)
Forest 25
Clearcut 15
Road right-of-way 15
Selected Drainages, Coast
Forest 32
Clearcut 32
Road right-of-way 32
H. J. Andrews Experimental
Forest 25
Clearcut 25
Road right-of-way 25
70.5
26.0
3.5
Mountains,
88.9
9.5
1.5
12.3
4. 5
0. 6
17.4
s .vi. British
246.1
26.4
4.2
Forest, western Cascade
77.5 49.8
19.3 12.4
3.2 2.0
7
18
75
100
Columbia
29
18
ll
Range,
31
30
69
45.3
117 .l
15 565
(O'Loughlin 1972,
ll. 2
24.51/
2 82.5-
Oregon (Swanson and
35.9
132.2
l 772
X
X
X
l.O
2.6
344
and personal communication)
X 1.0
X 2.2
X 25.2
Dyrness 1975)
X 1.0
X 3.7
X 49
Calculated from O'Loughlin (1972, and personal communication), assuming that the area in road
construction in and outside clearcuttings is 16 percent of the area clearcut.
In addition to sediment
originating from mass erosion
associated with roads, erosion
from road surfaces also
contributes sediment to streams.
Surface erosion from fill and
cut slopes, road surfaces, and
drainage ditches can severely
affect streams below the right-
of-way (Burns 1970, Brown and
Krygier 1971, Larse 1971,
Gibbons and Salo 1973,
Farrington and Savina 1977).
Although this type of erosion
is difficult to measure,
investigations in specific soil
types and climatic conditions
have given some idea of the
soil loss from forest roads
(Fredriksen 1965, Megahan and
Kidd 1972). For example, Haupt
(1959) found that road-fill
slopes were the primary source
of sediment moving downslope.
Packer and Haupt (1966) assessed
losses by surface erosion from
forest roads in the northern
Rocky Mountains and presented
guidelines to reduce surface
erosion and sedimentation.
3
CONTROLLING SEDIMENT A liON
THROUGH PLANNING
AND DESIGN
Larse (1971) pointed out
that the most important steps to
minimize the impact of road
construction on streams usually
occur during reconnaissance,
planning, and route selection,
rather than during or after
construction. He and others
have also repeatedly pointed out
that problems can be reduced by
including specialists such as
geologists, soil scientists,
fisheries biologists, and
hydrologists on the planning
team. Key environmental
problems and constraints are too
often overlooked when routes are
located and roads designed by
one person. Numerous guides for
reducing and controlling erosion
from roads have been devised
(Trimble and Sartz 1957, Haupt
1959, Packer and Haupt 1966,
Gonsier and Gardner 1971, Larse
1971, Burroughs et al. 1976,
4
Megahan 1977). Larse (197l)l/
summarized guidelines for route
selection to minimize erosion as
follows:
• Plan roads to take maximum
advantage of natural log
landing areas.
• Take advantage of benches,
ridge tops, and the flatter
transitional slopes near
the ridges and valley
bottoms. Avoid midslope
locations on steep,
unstable slopes. Grades
of 14-16 percent are
practical for low-use
roads.
• Locate valley-bottom roads
to provide a buffer strip
of natural vegetation
between road and stream.
Position roads on the
transition between the toe
slope and terrace to
protect the road slopes
from flood erosion. Roads
should not be built in
valley bottoms if
encroachment on the
stream will result.
• Locate ridge-top roads to
avoid headwalls at the
source of tributary
drainages.
• Vary road grades, when
possible, to reduce road-
surface erosion and flows
from culverts and drainage
ditches.
• Select stream crossings
carefully to take advantage
of the best drainage.
l/ For more detailed
recommendations refer to Larse
(1971).
In addition, where stream
protection for fisheries is
important, the recommendation
by Farrington and Savina (1977)
that no roads be built in a
stream's inner gorge should
probably be added to the above
six recommendations. Farrington
and Savina's recommendation may
be considered merely an
extension of Larse's third
guideline, however.
After the route is
selected, positive measures to
reduce erosion should be
incorporated into the road
design and construction. The
following recommendations by
Larse (1971, see footnote l)
summarize good erosion-control
measures that should be built
into forest roads:
•
•
•
•
Within limitations
necessary for type and
volume of traffic, fit
roads to terrain with
minimum of road width.
Minimize excavation with a
balanced earthwork design
whenever possible. Bench
or terrace and drain
natural slopes to provide
a sound foundation for
embankments.
Design rolling grades to
reduce surface water
velocity and culvert
requirements, but avoid
coinciding horizontal and
vertical curves that
concentrate surface runoff.
Design cut and fill slopes
as steep as possible
consistent with the
stability and strength of
soil and rock formations.
Round·tops of cut slopes to
reduce sloughing and
surface ravel.
•
•
•
•
•
Use retaining walls, with
properly designed drainage,
to reduce excavation,
contain bank material, and
prevent stream encroachment.
Vary ditch and culvert
requirements depending on
topography, road gradient,
soil erodability, and
expected intensity of
rainfall.
Place culverts to avoid
discharge onto erodible
slopes or into streams.
Install cross-drainage
culverts immediately up-
grade of headwalls and
stream crossings to
prevent ditch sediment
from entering the stream.
Design drainage structures
to accommodate the flow of
streams based on at least
a 25-year flood frequency
(50 years for large
permanent bridges and
major culverts), with due
consideration given to the
possibility of bedload and
debris restricting flow
capacity of the structure.
Determine the extent and
type of fish habitat
before selecting criteria
for structure design.
Bridges and arch culverts
are preferred in streams
with migratory fish.
Where culverts are used,
gradient should be less
than l percent, and a
constant minimum flow of
5-6 inches should be
provided at maximum
velocities of 6-8 ft/s
during low-water stages.
Scouring at the outlet can
be eliminated by energy
dissipaters, such as heavy
rock riprap, weirs, or
gabions.
5
•
•
•
•
6
Avoid channel changes and
protect embankment with
riprap, masonry headwalls,
or other retaining
structures. Align large
culverts with the natural
course and gradient of the
stream. Design the
placement of large culvert
inverts lower than the
natural streambed.
Floatable debris during
high streamflow can plug
small culverts and restrict
flow at larger culverts
and bridges, causing
severe road embankment,
streambank erosion, or
channel changes. Trash
racks, if properly
designed, constructed, and
maintained, can reduce
culvert plugging. Trash
racks can sometimes be
barriers to fish movement;
other measures to insure
culvert or bridge survival
should be considered.
Most forest roads should
be surfaced. The type of
surface will usually be
determined by traffic,
maintenance objectives,
desired service life, and
the stability and strength
of the road foundation
material.
Provide for vegetative or
artificial stabilization
of cut and fill slopes in
the design process.
Prior to completion of
design drawings, field
check the design to assure
that it fits the terrain,
drainage needs have been
satisfied, and all critical
slope conditions have been
identified and adequate
design solutions applied.
ROAD CONSTRUCTION
AND MAINTENANCE
A challenge to the
roadbuilder is to construct the
designed facility with a minimum
of disturbance, without damage
to or contamination of the
adjacent landscape, water
quality, and other resource
values. Some of the most
severe soil erosion can be
traced to poor construction
practices, insufficient
attention to drainage during
construction, and operations
during adverse weather
conditions.
Construction operations
can be conducted in most terrain
and climatic conditions if the
roadbuilder takes precautions
to minimize soil erosion and
stream sedimentation. Good
technical engineering work will
not itself control erosion
during construction, but work
must be deliberately planned,
scheduled, and controlled so
that different phases are
performed under optimum con-
ditions. When soil moisture
is excessive, earthwork
operations should be suspended
and measures taken to weather-
proof the partially completed
work. Work within or adjacent
to streams and water channels
should not be attempted during
periods of high streamflow,
intense rainfall, or migratory-
fish spawning.
The clearing of debris
underlying, supporting, or
mixed with embankment or waste
material is a common cause of
road failure and mass soil
movement. The necessary slope
bonding, shear resistance, and
embankment density for maximum
stability cannot be achieved
unless organic debris is
disposed of before embankment
construction is started. Woody
debris must also be removed from
all drainage channels and
headlands above or at the source
of drainage courses.
Although many techniques are
commonly practiced to minimize
erosion during construction, the
most meaningful are related to
how well the work is planned,
scheduled, and controlled by the
roadbuilder and those responsible
for determining that work satis-
fies design requirements and land-
management objectives.
Planned regular maintenance
is necessary to keep roads in
good condition, but maintenance
is too often neglected or
improperly performed, resulting
in deterioration. The vast
network of existing forest
roads, many of which have only
light or intermittent use,
present real problems as fuel
and other maintenance costs
increase.
To build and use a road re-
quiring no maintenance is neither
practical nor economical. Mainte-
nance requirements and expense
related to traffic use can and
should be considered in planning
and design to insure that the
completed road can be maintained
most economically. Where soil
erosion and sedimentation are of
concern to the forest manager,
the additional expense of
constructing a road with proper
attention to its stability and
proper drainage can generally be
amortized in a few years by
lower cost of upkeep.
Suggested maintenance
practices to prevent or control
erosion and stream sedimentation
are presented by Larse (1971,
see footnote l):
• Blading and shaping should
be performed to conserve
existing surface material.
•
•
•
Road inlet and outlet
ditches, catchbasins, and
culverts should be kept
free of obstructions.
Slide material should be
removed promptly when it
obstructs drainage systems.
Herbicides should not be
used where they might
contaminate water courses.
7
ROAD STABILIZATION
ADDITIVES
The use of various
chemicals to improve bearing
capacity and quality of running
surface of forest roads has had
a varied history in the Western
United States. Probably the
most common additive applied on
forest roads is some type of oil
to minimize dust. Freestone
(1972) estimated that 200
million gallons a year of waste
crankcase oil were added to
rural roads in the United
States. The amount of other
waste and nonwaste oils applied
to rural roads in the United
States, including forest roads
in the West, is unknown.
In addition to oils, other
chemical compounds used to improve
forest road quality include sodium
chloride, calcium cloride, hydrated
lime, and waste pulpmill liquors.
Commercial formulations especially
designed for road stabilization
also are being used more commonly
on forest roads. Unfortunately,
we know even less about the use of
chemical stabilizers on forest
roads than we do about road oil.
8
Most of the published informa-
tion on road stabilization with
chemicals is for the Eastern
United States and Canada (Duncan
1965, Gayer 1965, Paterson et al.
1970), and we have never found
the question of water-quality
impacts addressed.
Because of the increasing
cost and decreasing availability
of high-quality surfacing rock,
the use of various road-
stabilizing additives on Western
forest roads can only increase.
With increased use, surface and
subsurface runoff from oiled and
chemically treated roadways
could certainly cause localized
water-quality problems that
could affect fish and their
habitat. Little research has
been done that can allow us to
guess at the consequences of
increased road-additive use.
Burger (1973) studied the
acute toxicity and long-term
effects of Chevron PS-300~1 road
oil, a commonly used dust-control
agent, on juvenile coho salmon
(Oncorhynchus kisutch (Walbaum)).
The 96-hour TL 5 o for fish weigh-
ing 274/lb and 22/lb were 1350
and 1500 parts per million, re-
spectively. Long-term (30-53
days) effects of exposure to
road oil included reduced growth
rates, increased susceptibility
to disease, and histological
abnormalities of liver and spleen
tissue.
~/ The use of trade,
firm, or corporation names in
this publication is for the
information and convenience of
the reader. Such use does not
constitute an official
endorsement or approval by the
U.S. Department of Agriculture
of any product or service to
the exclusion of others that
may be suitable.
A study of runoff from
rural roads by Freestone (1972)
indicated that 99 percent of
road oils left the roadway. How
much was lost by volatilization,
adhesion to vehicles, dust
transport, biodegradation, or by
rain runoff, however, could not
be determined. The effect of
heavy metals in the road oils
may be more important than the
effect of the oil itself.
Clearly the location of the road
relative to waterways, method of
application, occurrence of rain
after application, and other
factors are important in
evaluating the possibility of
significant contamination of
fish habitat.
Our search of the
literature produced nothing on
the effects of road-
stabilization chemicals on fish
or their habitat. A fairly
extensive literature is
available on the effects of
sodium chloride and calcium
chloride on water quality, but
only in their use as deicing
agents (Struzeski 1971).
Deicing salts are applied at 10
to 20 times the rate used for
road stabilization. The method
and season of application are
also different for the two
purposes; the deicing literature
is therefore of little value for
inferring water-quality impacts
from increased use of this
chemical for road stabilization
in western forests.
Little is known about the
consequences of increased use of
road oil and stabilizing
chemicals, and we are not even
sure there are deleterious
effects to anadromous fish or
their habitat under current
application practices. The
likelihood of increased use of
road-stabilizing additives in
western forests, however,
indicates that the effects on
water quality deserve future
research.
ROADS AND FISH
MIGRATION
Salmon (Oncorhynchus spp.),
steelhead (Salmo ga1rdneri
Richardson), and other anadro-
mous fish require unobstructed
access to upstream spawning areas.
Road culverts can be barriers to
migration, usually because of
outfall barriers, excessive water
velocity in the culvert, insuffi-
cient water in the culvert, lack
of resting pools below culverts,
or a combination of these con-
ditions (fig. l).
The incorporation of fish
passage facilities must be based
on an assessment of habitat
quality and access. Natural
barriers downstream or
immediately upstream from the
site may preclude the need for
fish passage facilities. In one
National Forest, standard
policy is to provide fish
passage when l/4 mile or more of
good-to-excellent fish habitat
exists above the pipe. Usually,
a knowledgeable fisheries
biologist must be consulted to
assess the habitat.
9
(l 0
,P
t? ~ /)
J
p j) ;1
fl j) i)
c> cl ,t:J
?1 <>o c 0 0
0
Figure 1--Culvert conditions that
block fish passage (after Evans
and Johnston 1974). A--Velocity
too great, B--Flow in thin stream
over bottom, c--No resting pool
below culvert, D--Jump too high.
10
A
B
Jl v
c
'0 a...r-.
D
0 v
"' 75 0
C \So ~ ~~-~ 6 <J
C) <:l 0
G
0
~"'(_ ----------, ~-0
b 0
0 0
Because bridges usually
cause less disturbance to
streams than culverts, they are
often preferred for assuring
fish passage. Where concrete
foundations and piers are
constructed, however, bridges
have created problems, such as
scour and lowering of
streambeds. Construction of
anti-scour weirs, sills, and
aprons may be required to
prevent changes in the
streambed.
Log bridges should not
cause serious problems for fish
passage if properly constructed
and maintained. Where log
bridges have caused problems, it
is usually because there is
insufficent stream channel
clearance to accommodate high
flows. Bridge and earth
abutments then either wash out,
causing damage to the stream
below, or remain in place,
catching debris and forming a
debris barrier to migration.
Unfortunately, building
bridges on low-volume forest
roads often proves to be
uneconomical or impractical, and
culverts become necessary.
Forethought can greatly reduce
or eliminate the barrier effects
a particular culvert can have;
sometimes culverts must be
substantially redesigned. Most
obstructions, however, can be
easily prevented if the
potential is recognized during
planning.
If culverts are deemed
necessary for crossing a stream,
the road designer should be
aware of several factors that
affect the fish and also of the
choices of drainage structure
and location. The first
question is whether or not the
stream above the proposed
culvert is used by anadromous
fish. If not, the culvert
design problem is reduced to
the typical one of adequate
discharge capacity. If the
answer is yes, however, then the
designer must know which species
are in the stream, their life
history, and the season or
seasons of migration. For fish
to overcome obstacles in their
migration, the following
conditions are necessary:
• A resting pool should be
present immediately below
the obstacle. This allows
the fish to conserve
energy and obtain a good
start at overcoming the
obstacle.
• Individual jumps should not
be too high. The lower the
jump, under water
conditions that occur when
migration takes place, the
less difficulty the fish
will have in passing over
the obstacle. In general,
a single vertical jump of
1 foot can be negotiated by
resident adult trout. If
a series of jumps is
required, however, a half
foot at each is preferable.
Salmon and steelhead can
normally negotiate single
jumps of 2-3 feet without
difficulty. In a series,
however, individual jumps
should not be over a foot
high.
ll
•
•
In general, 6 inches is
minimum water depth for
resident trout; 1 foot is
required for salmon and
steelhead. Maximum
allowable velocities
should be around 4 feet
per second (ft/s) for
trout and 6 ft/s for
salmon and steelhead.
These maximum velocities
vary with distance and
fish species . .Y
If swimming distance is
over 50-100 feet in a
difficult passage, resting
pools may be required
enroute. This applies to
culverts and bridge
aprons in particular. The
need is determined by
examining the average
swimming ability of the
least capable species
using the stream relative
to water velocities and
distance for passage
through the structure.
llunpublished report,
"Fisheries handbook of
engineering requirements and
biological criteria. Useful
factors in life history of most
common species," by M. c. Bell.
Submitted to Fish.-Eng. Res.
Program, Corps of Eng., North
Pac. Div., Portland, Oreg.
1973.
12
•
•
Fish are often near
exhaustion after passing
over or through a difficult
obstacle and require a
resting area upstream. If
one is not available, the
fish are often swept
downstream over the
obstacle and must again
exert the energy to
surmount it.
Three hydraulic criteria
are important. The most
desirable culvert
installation is one that
causes no sudden increase
in water velocity above,
below, or through the
culvert. Culverts are best
located where the stream
reach is of similar
alignment above and below
the culvert for several
hundred feet. And, the
culvert gradient should be
as near zero as possible.
When these three conditions
are not met, problems in
fish passage may occur.
i
\
" ___ \
TYPES OF CULVERTS
Three types of metal
culverts are commonly used on
western forest roads.
(Cylindrical concrete culverts
generate extremely high water
velocities because they are
smooth inside. Internal
velocities may be many times
those in corrugated metal
culverts of the same diameter
and gradient. Concrete culverts
are thus not suitable for fish
passage.)
A B
a-• () c. . 0 0 ~ I> c
0 0
0
Metal culverts, classified
by shape, are standard corru-
gated round, standard corrugated
pipe-arch, and structural plate-
arch (fig. 2). The first two may
be prefabricated, as is usual for
the smaller sizes (up to 60 inches
diameter and 72-x-44-inch span
by rise) , or may be of multiplate
design. Type three culverts are
always of multiplate design be-
cause they are so large and
usually fabricated on site.
Figure 2--Typical cross sections of the
most commonly used metal culverts on
forest roads. A--Corrugated round
metal culvert, B--Corrugated pipe-
arch metal culvert, c--Structural
plate-arch with concrete footings
(also available in semicircular
cross section) •
c
.o6 a.oo"···~o •o
0
0 "
13
The structural steel arch
set in concrete footings (fig.
2c) is the most desirable
culvert type for fish because
the natural stream is left
undisturbed. Little contracting
in width occurs at either end of
the culvert, and no signficant
changes in velocity. Where
concrete footings are not
practical, split wide-flanged
buried steel footings have been
used recently in place of con-
crete footings. Disadvantages
of this installation are mainly
increased cost of installation
and the high fill needed. Many
fisheries biologists believe
that the arch type is the only
acceptable culvert where fish
passage is required (Evans and
Johnston 1974).
Pipe-arch culverts (fig. 2b)
are less desirable than the
structural steel arch, but they
can usually be installed to
allow fish passage. Fabricated
in smaller sizes, they can be
used in smaller, lower fills
where structural steel arches
would not fit. Where pipe
arches are used, the gradient
must be kept below 1 percent to
minimize water velocities.
During periods of low flow, the
water in culverts with this
shape may be spread so thin
across the bottom that fish
passage is impossible. Baffles
may then be needed to increase
the flow depth through the pipe-
arch (baffle systems are
discussed in more detail later).
14
Although the standard
corrugated round culvert (fig.
2a) is the type most commonly
used on western forest roads,
it is the least desirable for
fish passage. Because the
width constriction from stream
channel to culvert is usually
severe, the gradient of the
tube must be at or near zero
percent to minimize water
velocities through the pipe.
This type of culvert is also
most likely to be installed
with its outfall above the
tailwater elevation, producing
an outfall barrier (fig. 1).
Elevated outfalls of this type
are to be avoided or mitigated
by some means.
Thousands of streams have
had culvert crossing with
little or no thought to the
effects on fish populations.
One poorly installed culvert
can affect the fish population
of an entire small stream
drainage. Poor culvert design
and location can still be
ranked among the most devastating
problems for fish habitat in west-
ern forests.
Some general considerations
for culvert installation are:
• Avoid installation of
round culverts where fish
passage might be difficult.
Install either open-arch
culverts or bridges,
especially if culverts
longer than 100 feet are
required or where the
stream gradient is steep
(>2 percent).
•
•
•
•
•
A single large culvert is
better than several small
ones, because it is less
likely to become plugged
and carries water at much
lower velocity.
Diameter of culverts must
be adequate to pass maximum
flows. Washing out of
culverts and their earth
fills, besides damaging
the road, is also a source
of sedimentation.
Place the entire culvert
length slightly below
normal stream grade to
reduce fish passage
problems and prevent a
lowered streambed. Strive
for an installation
gradient at or near zero
percent; otherwise, avoid
round culverts.
The two most important
considerations for fish in
culverts are the maximum
acceptable water velocity
and the minimum acceptable
water depth for the
species.
Because streams used by
salmonids often fluctuate
widely with occasional
high peak flows, an
acceptable practice on
construction projects has
been not to require flow
conditions suitable for
fish passage during the 5
percent of the year when
flow peaks are highest
(Evans and Johnston 1974).
These flood peaks are
unusually high and normally
short. Fish normally do
not migrate during peak
flows, so little disruption
of fish migration occurs.
The practice often results
in substantial savings in
construction costs for fish
passage. The aim,
therefore, should be to
insure fish passage during
•
•
95 percent of a year, or 90
percent of the time on a
6-month basis. Any
structure for fish passage
must function through a
sufficiently wide range of
flows to accommodate the
period of migration.
Avoid baffling of culverts
if possible or use a larger
culvert, a reduced gradient,
or both. Baffles normally
require additional mainte-
nance and occasionally
cause debris accumulations.
Baffles are sometimes neces-
sary with high water veloci-
ties or in correcting fish
passage problems at existing
culverts.
Where culverts are
installed in stream
sections with steep
gradients, improve resting
pools, cover, and bank
projection along the
stream for several hundred
feet above and below the
culvert. Maintaining a
stable stream bottom
through the culvert-
influenced area is
essential.
15
WATER VELOCITY IN CULVERTS
Swimming ability of
salmonids increases with size
of the fish. Hence what species
uses the culvert has a bearing
on the allowable maximum
velocity. Specific velocity
limits for any anadromous
species cannot now be cited
with authority, but some general
guidelines are available for
adult fish. Metzker (1970)
reported that for trout up to
15 inches, eight ft/s should be
considered maximum for short
distances. Adult salmon can
travel through and sustain
velocities of 12 ft/s for short
distances. Metzker also pointed
out that the culvert velocity a
fish can overcome varies not
only with the fish's size, but
also with the distance between
resting pools below and above
the culvert. The Oregon State
Game Commission (1971)
recommended maximum water
velocities of 8 ft/s for adult
salmon and steelhead and 4 ft/s
for trout. The recommended
velocities in Oregon, however,
are for round culverts up
to 100 feet (30.5 m) in length.
16
Ul w
I
(.)
Water velocities in longer
culverts should not exceed
6 ft/s for adult salmon and
steelhead and 3 ft/s for
trout.
To aid road designers in
estimating the water velocities
through culverts, both the
Oregon State Game Commission
(1971) and the USDA Forest
Service (Evans and Johnston
1974) have produced series of
culvert velocity curves based
on Manning's equation (Chow
1959). The Oregon State Game
Commission curves are for round
metal culverts only, ranging in
diameter from 24 to 84 inches.
Gradients range from 0.25 to 5.0
percent. Figure 3 is an example
of the Oregon velocity curves
for a 72-inch culvert. Because
fish passage through culverts
normally occurs between a
minimum depth of 3 inches and a
maximum depth of two-thirds the
pipe diameter, the Oregon curves
cover only these depths.
40
~ 30
a: w
~ 20
LL.
0
I
b: 10 w c
3---
2 3 4 5 6
VELOCITY (FEET PER SECOND)
------Minimum depth for fish passage
·················· · Trout swimming ability
· · · · · · · · · Salmon-steelhead swimming ability
7 8
Figure 3--Velocity curves for a 72-inch
diameter round culvert (after Oregon
State Game Commission 1971) .
2
3
4
5
0 z
0
() w
Ul
a: w
(]._
f-w w
':!:.
>-f-u
0
....1 w >
iJi w
I
() z
~
....1
LL.
LL.
0
I
f-
Q.
UJ c
The USDA Forest Service
velocity curves are more
detailed than the ones for
Oregon; curves have been
provided not only for round
culverts (36-to 120-inch), but
also for concrete box culverts
(26-to 120-inch) and for
3-x-l, corrugated metal pipe-
arches (7 ft x 5 ft l inch to
16 ft 7 inch x 10 ft l inch,
span by rise). Also the USDA
Forest Service curves yield both
velocity and depth of flow for
any given discharge, culvert
gradient, and diameter. Figure
4 illustrates the format of the
USDA Forest Service curves for
a metal pipe-arch.
20
0
4
0 50 100 150 200 250 300 350
FLOW (CUBIC FEET PER SECOND)
% 1f2 '"' 1 1 112 2 3
4
00 50 100 150 200 250 300 350
FLOW (CUBIC FEET PER SECOND)
Figure 4--Velocity and depth-of-flow
curves for a 7-foot by 5-foot l-inch
pipe-arch (after Evans and Johnston
1974).
Salmonid spawning streams
in the West are often mountain
streams with steep gradients.
Even culverts placed on the same
grade as the original streambed
may exhibit water velocities
greater than migrating fish can
overcome; to control water
velocities in culverts then,
installing baffles may be
necessary.
Constructing a fish passage
facility through a culvert
essentially opposes the reason
for the culvert, which is to
discharge water downstream at
the highest possible rate with
the smallest culvert possible.
On the other hand, the structure
for fish passage attempts to
produce pockets of low velocity
in the culvert where fish can
rest momentarily. To provide
these low velocities, energy
dissipaters of some form are
required--normally, baffles or
small water barriers.
Baffle designs are probably
as numerous as the people
installing them. Little
information is currently
available on the hydraulic
principles of various types of
baffles. Additional applied
research in this field should
be encouraged. The best
information on baffle design is
in a Washington Department of
Fisheries report (McKinley and
Webb 1956); the principles are
sufficiently sound to be used
as present guidelines, pending
results of further research .
17
Certain general principles
have been developed through
long experience with baffles in
culverts:
• Avoid using baffles whenever
possible. Solve your fish-
passage problems preferably
through considerations of
bridges, arch culverts or
round culverts of
sufficient size, and
installations of low water
velocity at or below
streambed level.
• If higher velocities,
extensive distance, or both
are unavoidable in a round
or box culvert installation,
baffles will be necessary.
Baffles and resultant quieter
waters allow a fish to swim
in short spurts straight
through high velocities and
enter a rest area parallel
to the higher velocity flow.
112%B . I
1'2.5>% B
-~
oB% e.
•
•
A large single culvert pro-
vides better fish passage
than several smaller ones.
Where multiple units are
required, only one must be
baffled to pass fish. Select
the culvert for baffling based
on the route most likely to
attract fish. At such instal-
lations, provisions should be
made for diverting low flows
through the baffled culvert
only.
The baffle design
illustrated in figure 5 is
recommended for general use
by the California Region of
the U.S. Forest Service
(Evans and Johnston 1974).
For the design in figure 5
to be readily adaptable to
installations of various
sizes, the dimensions have
been given as percentages
of total width of the
baffled section. These
s
C:ULVEI<T WALL
Nor l.ES'OTfiAN 4 FEeT [
NOT MORE THAN f, A:.ET ~
~~
'/
__, 26% s\..-
CULVBZT WALL
Figure 5--Baffle-pattern arrangement for metal culverts (after Evans and
Johnston 1974). B equals clear width of box culvert, intercept width is
1 foot above invert (round or arch culverts) , and all baffles are 1 foot
high.
18
•
•
•
dimensions and angles of
baffles have been
determined through research
and should be adhered to.
Baffles should be a minimum
of 1 foot high and 5-6
inches v1ide.
Calculate the relative
efficiency of the culvert
with and without baffles,
because the passage of
water through the culvert
will be impaired by the
baffle structures. Because
a large safety factor is
required, most culverts are
overdesigned for the
discharge conditions, and
the actual impairment of
the culvert's ability to
discharge is relatively
small. The ultimate
culvert size required is,
of course, a decision for
the engineer.
Construction materials for
baffles may be wood,
metal, or concrete,
depending upon the local
situation. Wood is
sometimes preferable
because it offers greater
resilience when hit by
moving objects and also can
be replaced more easily.
Concrete baffles may be
pre-cast and drilled or
grouted into place. Metal
baffles are normally
bolted onto the culvert
floor, using metal plates
for added strength.
"Most baffles are designed
to operate best when water
flow is just overtopping
them and their
effectiveness is inversely
proportional to the depth
of water over them."
(Gebhards and Fisher 1972).
•
•
•
Placing baffles properly in
a new culvert before its
installation is far less
expensive than trying to
alter an installed culvert.
For round metal culverts,
a minimum culvert diameter
of 5 feet is required to
provide a 4-foot-wide space
for baffle installation
(fig. 5).
Baffles may have value
other than controlling
velocity; for example, they
increase water depth in
the pipe to provide fish
passage during low flow
periods. Another example
would be to convert a
culvert with a steep
gradient into a series of
pools--in effect, creating
a modified fish-ladder.
19
CULVERT OUTFALL BARRIERS
Culverts can be
insurmountable barriers to
migrating fish when the outlet
of the culvert is so far above
the tailwater that fish cannot
enter the pipe; this condition
is termed an outfall barrier
( fig. 1) .
Where new culverts are to
be installed on streams with
migrating fish, every attempt
should be made to avoid
constructing an outfall barrier.
Putting a new culvert outlet
below the tailwater elevation is
sometimes not possible, or--more
commonly--an existing culvert
forms an outfall barrier.
20
One way to correct a
culvert outfall barrier is to
provide for one or a series of
low-head dams below the culvert
outfall (fig. 6). These dams
may be nothing more than hand-
placed rock "reefs" or wire-
basket gabions filled with
local rock, or concrete sills.
These downstream dams raise the
tailwater elevation and flood
the culvert. Access by fish is
not only enhanced, but water
velocity in the culvert is
decreased. The downstream dams
should not create outfall
barriers themselves and should
therefore be limited to about
1 foot in height or, for dams of
greater heights, have a pass-
through notch in the center.
Because the backflooding
decreases velocity and hence
discharge, a culvert of larger
diameter may be necessary to
handle peak flows. Also,
armouring the downstream side
of the low-head da~s may be
necessary to prevent scouring
from the cataracts formed.
In some streams, the range
of flows is so wide that it is
impossible not to have the
culvert outlet above tailwater
at some time. Also, where
severe fluctations in flow
require large culverts, problems
are sometimes encountered in
providing fish passage during
low flows because of the shallow
flow over the broad culvert
bottom. Then, stacked-or
multiple-culvert installations
can be used to provide fish
passage (fig. 7). Placing the
stacked culverts at different
elevations assures adequate
discharge capacity as well as
fish passage over a wider range
of flows. The lower, smaller
culvert would concentrate low
flows and assure fish passage
then. Note our previous
statements on the inhibitory
effects full culverts have on
fish passage.
Figure 6--Gabion or concrete sills can raise tailwater elevation to
facilitate fish entry into the culvert; this weir construction was
used to improve fish passage at the mouth of Gold Creek (after
Evans and Johnston 1974).
Figure 7--Fish passage may be provided in streams that have wide ranges
of flows by providing multiple culverts.
21
STRUCTURES FOR DEBRIS
CONTROL
The use of debris-control
structures--such as trash or
debris racks--is growing in
western forests. A partial
reason is the increased cost of
replacing culverts and washed-
out roadways; trash racks are
often mandated by forest
practice regulations.
22
Unfortunately, trash racks
are detrimental to fish passage.
The same freshets that often
bring debris downstream are
those in which many fish can
move up to spawning areas.
Although the protected culvert
may not be a velocity or outfall
barrier, a debris-laden trash
rack is almost always impassable
to fish. Debris-catching
structures on streams used by
migrating fish should be
avoided.
To compensate for the loss
of culvert protection from a
debris-catching structure, the
culvert should be large enough
to let the debris pass through
it. Passing debris through the
culvert is as valid an
alternative as intercepting it
above the inlet, and this
alternative should not be
overlooked. Of course,
increasing the culvert diameter
adds to its cost, and sometimes
increasing the diameter may not
be practical. On the other
hand, when debris can be passed
through the structure without
clogging, maintenance costs will
be lower than when debris is
intercepted and must then be
removed.
SUMMARY
. Forest road systems, along
w1th other forest-management
activities, can adversely
affect a stream's ability to
pro~ide spawning and rearing
hab1tat for anadromous fish.
Guidelines are available for
road construction and
maintenance with minimal impact.
on anadromous fish habitat.
Properly designed and placed
culverts and debris-control
structures can also help to
minimize the impacts on fish
habitat of forest road systems.
LITERATURE CITED
Anderson, H. W. 1971. Relative
contributions of sediment
from source areas, and
transport processes. In
Forest land uses and
stream environment,
p. 55-63. J. T. Krygier
and J. D. Hall, directors.
Oreg. State Univ.,
Corvallis.
Brown, George W., and James T.
Krygier. 1971. Clearcut
logging and sediment
production in the Oregon
Coast Range. Water Resour.
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Burger, Kenneth R. 1973. Acute
toxicity and long-term
effects of PS-300 road oil
on juvenile coho salmon,
Oncorhynchus kisutch. M.S.
thesis. Humboldt State
Univ., Arcata, Calif.
67 p.
Burns, James W. 1970. Spawning
bed sedimentation studies
in northern California
streams. Calif. Fish and
Game 56(4):253-270.
23
Burroughs, E. R., F. R.
Chalfant, and M. A.
Townsend. 1976. Slope
stability in road
construction. Bur. Land
Manage., U.S. Dep. Inter.,
Oreg. State Off., Portland.
102 p.
Chow, Ven Te. 1959. Open-
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p. 98-101. McGraw-Hill
Book Co., Inc., New York,
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65(1) :16-17.
Evans, William.A., and F. Beryl
Johnston. 1974. Fish
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A practical guide to
solving fish passage
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Farrington, Richard L., and Mary
E. Savina. 1977. Off-site
effects of roads and
clearcut units on slope
stability and stream
channels. Fox Planning
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For., Eureka, Calif.
Fiksdal, A. J. 1974. A
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Stegualeho Creek watershed:
Supplement to Final Report
FRI-UW-7404, Fish. Res.
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Fredriksen, R. L. 1965.
24
Sedimentation after logging
road construction in a
small western Oregon
watershed. u.s. Dep.
Agric. Misc. Publ. 970,
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Freestone, Frank J. 1972.
Runoff oils from rural
roads treated to suppress
dust. EPA Tech. Ser. EPA-
R2-72-054. Off. Res. and
Monit., Natl. Environ. Res.
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29 p.
Gayer, Richard J. 1965. Soil-
cement. Low cost
roadbuilding material.
Tech. Pap. Am. Pulpwood
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Gebhards, Stacey, and Jack
Fisher. 1972. Fish
passage and culvert
installations. Idaho Fish
and Game Dep.
Gibbons, Dave R., and Ernest o.
Salo. 1973. An annotated
bibliography of the effects
of logging on fish of the
Western United States and
Canada. USDA For. Serv.
Gen. Tech. Rep. PNW-10,
145 p. Pac. Northwest
For. and Range Exp. Stn.,
Portland, Oreg.
Gonsier, M. J., and R. B.
Gardner. 19 71 .
Investigations of slope
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Batholith. USDA For.
Serv. Res. Pap. INT-97,
34 p. Intermt. For. and
Range Exp. Stn., Ogden,
Utah.
Haupt, H. F. 1959. Road and
slope characteristics
affecting sediment movement
from logging roads.
J. For. 57(5):329-332.
Larse, Robert W. 1971.
Prevention and control of
erosion and stream
sedimentation from forest
roads. In Forest land
uses andstream
environment, p. 76-83.
J. T. Krygier and J. D.
Hall, directors. Oreg.
State Univ., Corvallis.
McKinley, W. R., and R. D.
Webb. 1956. A proposed
correction of migratory
fish problems at box
culverts. Wash. Dep.
Fish., Fish. Res. Pap.
1(4):33-45.
Megahan, Walter F. 1977.
Reducing erosional impacts
of roads. In Guidelines
for watershed management,
FAO conservation guide,
p. 237-261. Rome.
Megahan, W. F., and W. J. Kidd.
1972. Effects of logging
on erosion and sediment
deposition from steep
terrain. J. For.
70(3):136-141.
Metzker, Howard E. 1970. Fish
versus culverts: Some
considerations for resource
managers. USDA For. Serv.
Eng. Tech. Rep. ETR-7700-5,
19 p.
Morrison, P. H. 1975.
Ecological and
geomorphological
consequences of mass
movements in the Alder
Creek watershed and
implications for forest
land management. B.A.
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Eugene. 102 p.
O'Loughlin, C. L. 1972. An
investigation of the
stability of the steepland
forest soils in the Coast
Mountains, southwest
British Columbia. Ph.D.
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1971. Fish passage through
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9 p.
Packer, Paul E., and Harold F.
Haupt. 1966. The
influence of roads on water
quality characteristics.
Soc. Am. For. Proc.
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Paterson, W. G., H. W.
McFarlane, and W. J.
Dohaney. 1970. Industry
experience with forest road
stabilization methods and
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18, 52 p. Pulp and Pap.
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Reiser, D. w., and T. C. Bjornn.
1979. Habitat requirements
of anadromous salmonids.
In Influence of forest and
rangeland management on
anadromous fish habitat in
Western North America.
William R. Meehan, tech.
ed. USDA For. Serv. Gen.
Tech. Rep. PNW-96, 54 p.
Pac. Northwest For. and
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Struzeski, Ed. 1971.
Environmental impact of
high deicing. Water
Pollut. Control Res. Ser.
11040 GKK 06/71, 120 p.
Edison Water Qual. Lab.,
U.S. EPA, Edison, N.J.
Swanson, F. J. 1975. Impact of
clearcutting and road
construction on soil
erosion by landslides in
the western Cascade Range,
Oregon. Geology
(July 5):393-396.
Swanson, F. J., and Dyrness,
C. T. 1975. Impact of
clearcutting and road
construction on soil
erosion by landslides in
the western Cascade Range,
Oregon. Geology 3:Y93-396.
25
Swanston, D. N. 1971.
Principal mass movement
processes influenced by
logging, roadbuilding, and
fire. In Forest land uses
and stream environment,
p. 29-39. J. T. Krygier
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Oreg. State Univ.,
Corvallis.
Swanston, Douglas N., and
Frederick J. Swanson.
1976. Timber harvesting,
mass erosion, and steepland
forest geomorphology in the
Pacific Northwest. In
Geomorphology and
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Donald R. Coates, ed.
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Trimble, F. R., and R. s.
26
Sartz. 1957. How far from
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55(5):339-341.
The FOREST SERVICE of the U.S. Department of Agriculture is dedicated
to the principle of multiple use management of the Nation's forest resources
for sustained yields of wood, water, forage, wildlife, and recreation.
Through forestry research, cooperation with the States and private forest
owners, and management of the National Forests and National Grasslands, it
strives -as directed by Congress -to provide increasingly greater service to
a growing Nation.
The U.S. Department of Agriculture is an Equal Opportunity Employer.
Applicants for all Department programs will be given equal consideration
without regard to age, race, color, sex, religion, or national origin.