U.S. ENVIRONMENTAL PROTECTION AGENCY
CONTRACT NO. 68-01-6403
HYDROLOGIC BASIS
FOR
SUSPENDED SEDIMENT CRITERIA
Christopher C. Clarkson, P.E.
Dale E. lehnig
Stanley V. PI ante
Robert S. Taylor, P.E.
W. Martin Williams
Camp Dresser & McKee
7630 Little River Turnpike, Suite 500
Annandale, Virginia 22003
November 1984
Revised May 1985
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TABLE OF CONTENTS
Chapter Page
EXECUTIVE SUMMARY v
1.0 INTRODUCTION 1-1
2.0 SEDIMENTATION PROCESSES 2-1
2.1 Geomorphology 2-1
2.2 Sediment Transport Mechanics 2-1
2.3 Methods of Prediction and Analysis 2-2
2.4 Spatial and Seasonal Variations 2-16
2.5 Rates of Erosion and Sediment Loading 2-33
2.6 Impacts of Anthropogenic Suspended Sediment 2-33
2.7 Summary 2-36
3.0 IMPACTS OF SUSPENDED SOLIDS ON AQUATIC LIFE 3-1
3.1 Introduction 3-1
3.2 Effects of Suspended Sediment on Phytopiankton 3-3
and Zooplankton
3.3 Effects of Suspended Sediment on Macroinvertebrates 3-5
3.4 Effects of Suspended Sediment on Salmonid Fish 3-7
3.5 Effects of Suspended Sediment on Other Fish 3-14
4.0 A FRAMEWORK FOR SUSPENDED SEDIMENT CRITERIA TO PROTECT 4-1
AQUATIC LIFE
4.1 Introduction 4-1
4.2 Regional Bases for Criteria 4-2
4.3 Combining Biology and Statistical Hydrology 4-12
4.4 Additional Factors That Must Be Considered 4-25
5.0 CONCLUSIONS AND RECOMMENDATIONS 5-1
5.1 Conclusions 5-1
5.2 Methodology Recommendation 5-1
5.3 Future Work 5-2
6.0 BIBLIOGRAPHY 6-1
APPENDICES
A. Tolerances of Fish to Suspended Solids (Turbidity) A-l
and Sediment
B. Soil Conservation Service Land Resource Region B-l
Descriptions
i
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LIST OF TABLES
Table Page
2-1 Sediment Process Models 2-3
2-2 Relation of Air Mass Types to Sediment Yields 2-24
2-3 Suspended Sediment Discharge from Conterminous United 2-32
States
3-1 Percent Increases in Number of Drifting Macroinverte- 3-6
brates Caused by Additions of Known Amounts of
Suspended Sediment
3-2 Observed Mortalities of Species Relatively Insensitive 3-8
to Suspended Kaolin
3-3 200-hr LCX Estimates, Equations, and Coefficients of 3-8
Determination for those Species Tested Longer than 200-hr
3-4 Summary of Effects of Suspended Solids on Salmonid Fish 3-10
3-5 Patterns of Reproductive Timing and Movement Among 3-15
Warmwater Fishes
3-6 Effects of Suspended Solids on Non-Salmonid Fish 3-16
3-7 Some Effects of Turbidity on Selected Fish Species 3-19
3-8 LC10, LC50 and LC90 Values for Spot, with Increasing 3-21
Duration of Exposure to Fuller's Earth
3-9 LC10, LC50 and LC90 Values for White Perch, with 3-23
Increasing Duration of Exposure to Fuller's Earth
3-10 Lowest Fuller's Earth Concentration Causing 100-Percent 3-24
Mortality in a 24-hour Exposure for Five Estuarine Fish
3-11 LC10, LC50 and LC90 Values Determined for 24-hour 3-25
Exposure of Estuarine Fish
ii
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LIST OF FIGURES
Figures Page
2-1 Comparison of Bed Transport Formulae 2-5
2-2 Instantaneous Sediment Rating Curve for Niobrara River 2-7
near Cody, NE
2-3 Seasonal Adjustment to Discharges of Sediment in Clay 2-8
and Silt Sizes, White River Near Kadoka, SD
2-4 Approximate Average Variation of Coefficient of Sediment 2-9
Discharge with Elapsed Time After Beginning of a Rise,
White River near Kadoka, SD
2-5 Comparison of Different Sediment Concentration Relation- 2-10
ships with Timing of Runoff Hydrograph
2-6 Variation in Suspended Sediment Concentration with 2-11
Hydrograph for a Low Intensity Storm
2-7 Variation in Suspended Sediment Concentration with 2-12
Hydrograph for a High Intensity Storm
2-8 Sediment Rating Curve for the Powder River at Arvada, WY 2-14
2-9 Relative Erosion as Related to Mean Annual Temperature 2-17
and Precipitation
2-10 Seasonal Relationships of Sediment Concentration and 2-19
Water Discharge
2-11 Sedihydrograms for Rivers Influenced by Different 2-20
CIimates
2-12 Effect of Land Use on Sedihydrogram for Two Sites 2-22
in Maryland
2-13 Relation of Air Mass Types to Sediment Yield 2-23
2-14 Generalized Sediment Transport and Yield Conditions 2-26
Associated with Common U.S. Air Masses
2-15 Suspended Sediment Concentration Versus Water Discharge 2-28
for Four Atlantic Coast Rivers
2-16 Suspended Sediment-Water Discharge Relations for a 2-29
Piedmont Stream
2-17 Drainage Areas and Locations of Sediment Sampling 2-31
Stations
1 i 1
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LIST OF FIGURES
Figures Page
2-18 Comparison of Suspended Solids Concentrations in 2-35
Roanoke River at Scotland Neck, NC, Before and After
Kerr Reservoir Completion
2-19 Comparison of Suspended Sediment Concentrations in 2-37
the South River, SC, Before Entering and After Leaving
Two Large Reservoirs
4-1 Physiographic Regions, Case 1 4-3
4-2 Physiographic Regions, Case 2 4-4
4-3 Regionalization by Principal Drainage Basin 4-5
4-4 Map of Drainage Basins 4-6
4-5 Regionalization by SCS Land Resource Units 4-8
4-6 Average Annual Precipitation for Conterminous U.S. 4-9
4-7 Average Annual Runoff for Conterminous U.S. 4-10
4-8 Average Annual Number of Days with Thunderstorms 4-11
4-9 Distribution of Runoff, by Region and by Season 4-14
4-10 Seasons of Lowest Flows 4-15
4-11 Seasons of Highest Flows 4-16
4-12 Typical Flow-Duration Curve 4-18
4-13 Hypothetical Concentration-Duration Plot of Adverse 4-19
Effects Response for Exposure of a Fish to Suspended
Sol Ids
4-14 Hypothetical Daily Record of Suspended Solids 4-22
4-15 Number of Times a Given Concentration is Exceeded for 4-23
a Given Number of Days
4-16 Relationship of Suspended Solids Adverse Effect Level 4-24
to Likelihood of Occurrence of a Given Suspended Solids
Concentration
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EXECUTIVE SUMMARY
• The objective of this report 1s to discuss factors that are important to
the development of criteria for suspended matter In the water column.
Since the interest is in criteria for suspended matter in.general,
regardless of origin, no distinction is made between wastewater solids,
commonly referred to as 'suspended solids,' and suspended matter of
other origin, such as erosion or channel scour, which is often referred
to as 'suspended sediment.'
• The term 'criteria' 1s used 1n this report in the context of the pro-
tection of aquatic life. The protection of other uses—such as contact
recreation, navigation, water supply, etc.—is beyond the scope of the
study.
• Several factors that are important to the development of a water quality
criterion for suspended sol ids/turbidity are examined in this report.
These factors include regional, physiographic, and seasonal considera-
tions, and related hydrologic phenomena. Particular emphasis is placed,
1n Chapter 4, on statistical hydrology (frequency-intensity relation-
ships) and on the combination of hydrologic information with biological
Information as a means of formulating criteria.
• Most suspended solids in a river can be attributed to nonpoint sources.
Some nonpoint source suspended sediment is natural in origin and is
nearly impossible to control. Most nonpoint source solids result from
man's alteration of the environment--e.g., agriculture, mining, and
urbanization. Although most cultural sources could be controlled,
political and economic considerations render effective control problem-
atic. The relative contribution of natural and anthropogenic sources of
suspended sediment may shift In favor of the former during high flow
periods when sediment in the water column due to natural erosion and
channel scour may be high.
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• The natural solids loading to a waterbody will vary from site to site,
depending upon physiographic factors (slope, soil type, type of ground
cover, etc.) and upon rainfall and runoff. Anthropogenic nonpoint
source loadings will also vary strongly with the rainfall and runoff
characteristics of a particular area. Point source loadings may be
proportionately large during dry weather periods, although the con-
comitant low flows and low velocities may mean that suspended solids
will settle rapidly and be cleared from the water column. During wet
weather periods, point source loadings may remain constant, yet become
insignificant compared to nonpoint source loadings added to the system.
Given these considerations, it is apparent that seasonal and regional
criteria are indicated that take into account the significance of
natural and cultural nonpoint source loadings.
• Water quality criteria typically specify concentrations in the water
column that will protect aquatic life from adverse effects. While this
approach is applicable to suspended sediment concentrations 1n the water
column, it may not be sufficient, for two reasons. First, a water
column concentration for solids would provide protection from possible
adverse physical effects on the biota, but would not necessarily protect
against possible chemical effects due to toxics sorbed to the solids
particles. Second, a water column criterion ignores possible effects
(smothering of habitat, and chemical effects due to sorbed toxics) if
the suspended matter settles from the water column. The question of
sediment criteria is now under review by the Criteria and Standards
Division (OWRS). The question of adverse effects due to toxics sorbed
to suspended sol Ids 1s complex, and should be considered in the develop-
ment of criteria for suspended matter.
• Hydrologlc events are particularly Important to the generation of sus-
pended sediment in a water body. The historical record may be analyzed
to characterize seasonal suspended sediment concentrations in a water
body.
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• Comparatively little quantitative information is available that is
descriptive of the effects of sediment on the biology of a water body.
Even less is known about the effects of suspended sediment. The avail-
able data might suffice for initial investigations into the development
of criteria, but a much more extensive data base eventually will be
required in order to develop criteria that are as refined as those for
some toxic chemicals, and that take into consideration the collective
biota of a stream, and the different life stages of that biota.
• The effects of sustained exposure to suspended sediment may be of
greater concern to adult forms than exposure to short pulses of sus-
pended matter. This may not be true of other stages of the life cycle.
Storm related pulses of suspended matter may be of little consequence to
the biota. However, such pulses may resuspend sediment and carry it
downstream until velocities subside and the solids settle out. Such
resettlement may have adverse consequences for the biota.
• A procedure is discussed in Chapter 4 whereby the analysis of hydrologic
phenomena and biological effects may be combined to frame criteria
protective of aquatic life. This is a non-specific discussion, however,
and only sets out a framework for the joint consideration of regional,
seasonal, and biological factors.
• Equally as important as the specification of criteria for suspended
solids is the establishment of a protocol for the enforcement of such
criteria. In many cases the load and concentration attributable to a
point source of suspended sol Ids will be small compared to background
levels. Background levels will certainly have to be taken into con-
sideration and in many cases may render criteria meaningless. For those
cases where background levels do not dominate, criteria might be
appropriate.
vi1
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1.0 INTRODUCTION
The purpose of this report is to investigate hydrologic/sediment load
relationships that might be used to establish a water quality criterion for
suspended sediment. The approach to development of criteria for suspended
sediment is somewhat different from that for toxic chemicals because toxics
concentrations will be low during high flow periods, while sediment con-
centrations will be high.
Suspended sediment in a stream is derived from point source discharges,
nonpoint sources, and the resuspenslon of bottom deposits. High flows may
scour the channel and resuspend a considerable amount of material. During
dry weather periods, the volume of sediment entering a river system is
reduced, velocities decrease, and suspended matter settles out.
Erosion and sediment transport are natural processes resulting from the
interaction of many physical variables that can be described by, but are
not limited to, the travel of water on the surface of the earth. The
degree of erosion is a function of (1) the frequency, Intensity, and
distribution of precipitation; (2) the chemical and physical properties of
the soil; (3) soil cover; and (4) the topography of the area, which both
influences and is influenced by the erosion process.
Natural rates of soil loss depend on the characteristics of a particular
region. A severe disruption in events may have a significant impact on the
environment. The disruption can be caused by natural phenomena such as
Infrequent but severe storm events or by such activities as rapid urbani-
zation or widespread clearing for agricultural purposes. The influence of
man on sediment loadings may be seen in cropland erosion, mining, construc-
tion, and other activities.
The specific effects of sediment on aquatic organisms depend on sediment
characteristics and concentrations. Material that 1s suspended in the
water column decreases light penetration and may affect photosynthesis and
primary production. Suspended sediment also acts directly on some aquatic
life, through abrasion, by clogging gills, and by inhibiting feeding
1-1
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activity. Settled sediment may modify and render habitats unsuitable for
certain organisms. If large amounts of sediment settle, the habitat and
its resident biota may be smothered.
The variability of factors influencing suspended sediment necessitates the
development of criteria on a regional and perhaps seasonal basis. The
hypothesis to be examined in this report is that a comparison of regional
and seasonal variations in aquatic life cycles to regional and seasonal
variations in hydrology and suspended sediment loads offers a promising
approach to the development of suspended sediment criteria and standards.
The following sections of this report outline a possible basis for
establishing criteria. Chapter 2 presents a discussion of the factors
influencing suspended sediment loads and the mechanics of sediment
transport; a review of previous studies on observed spatial and temporal
variations of sediment concentrations; a review of various methods for
predicting and analyzing sediment loads; and a discussion of the impacts of
urbanization on sediment concentrations.
Chapter 3 discusses the impacts of suspended sediment on aquatic life.
Aquatic life is discussed by category: primary producers and zooplankton,
macroinvertebrates, salmonid fish, and other fish. Categories are based on
similarity of species and, in particular, reproductive and life cycle
stages. Attempts are made to relate life cycle stages and respective
tolerances of aquatic life category to sediment concentrations under
seasonal and regional patterns.
In Chapter 4, several aspects of hydrologic regions and seasons are dis-
cussed, and an approach is proposed by which hydrologic data and toxicity
data may be considered jointly in order to develop criteria. In this joint
approach, the treatment of hydrologic data is based on an analysis of the
number of events of a given intensity and duration rather than the
customary type of analysis that is based on the cumulative duration of a
given flow rate.
1-2
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2.0 SEDIMENTATION PROCESSES
2.1 GEOMORPHOLOGY
Geomorphology is the study of the configuration and evolution of landforms.
Hydrogeomorphology is the science of landform evolution as governed by the
hydrologic cycle. The interaction between geomorphology and the hydrologic
cycle is significant, for the topographic structure of the earth's surface
not only affects the motion and storage of water after a rainfall, but in
turn is affected by it.
In the hydrologic cycle, overland flow occurs when the rate or quantity of
rainfall exceeds the amount of precipitation that can be Intercepted by
vegetation, or that is lost to infiltration and evaporation. Surface flow
occurs due to energy gradients causing a conversion of potential to kinetic
energy. When the surface flow velocity exceeds a critical value, erosion
of the local surface material occurs.
The extent of erosion and the topographic characteristics of the land are
related to the climate and the geology of the region. The permeability and
strength of surface materials are characteristic of the geology; the
intensity, duration, and distribution of precipitation are characteristics
of the climate and meteorology; and the geology and meteorology combined
determine the dynamic relationships between vegetation, roughness, and
surface slope.
Geomorphology Involves dynamic activities in which the land surface is in a
slow but continuous state of change. The thermodynamic approach is to
envision the drainage basin as striving toward a state of compromise
between a uniform distribution of energy expenditure and a minimum total
rate of work. The degree of erosion, sediment transport, and sediment
deposition reflects the dynamic state.
2.2 SEDIMENT TRANSPORT MECHANICS
Sedimentation Involves the processes of erosion, entrapment, transport,
deposition, compaction, and cementation of sediment particles. The removal
of soil particles from their environment is called erosion. Erosion occurs
2-1
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when shear forces caused by flowing air or water, or by the impact of rain-
fall, are greater than the gravitational and/or cohesive forces which hold
soil particles in place. Entrainment is the process in which eroded soil
particles become part of the flow. Transport is the conveyance of sediment
particles within the flow regime. The nature of movement and concentration
of suspended sediment depends on the size, shape, and specific' gravity of
the sediment particles in relation to the turbulence and velocity distri-
bution in the channel. Sediment will remain in suspension until gravita-
tional forces exceed uplift from vertical components of velocity in the
water discharge, at which point deposition of particles onto the land
surface or channel bed will occur. Compaction results from the weight of
successive layers of deposited sediment.
The reader is referred to Sedimentation Engineering (ASCE, 1975) for a
comprehensive discussion on sedimentation including the theory of particle
characteristics and behavior.
2.3 METHODS OF PREDICTION AND ANALYSIS
Many formulas have evolved over the past 50 years to predict sediment
behavior, concentration, and yield. Most theories address individual
aspects of sedimentation such as bed load movement theory or suspended
sediment distribution in a given channel cross-section. Other relation-
ships link sediment load with hydraulic relationships. Unfortunately, many
of these are predictive equations or annual estimates and were developed
for engineering purposes such as estimating reservoir siltation and channel
morphology as opposed to estimating concentrations in suspension. Examples
of models for sediment processes are illustrated in Table 2-1.
Methods of predicting sheet erosion on overland areas can be estimated
using the Universal Soil Loss Equation and adaptations of the Musgrove
Equation (ASCE, 1975). The Universal Soil Loss Equation computes the
average annual soil loss (tons per acre) from a specific field based on
soil erodibility, rainfall, topographic, crop management, and conservation
practice factors. The Musgrove Equation computes average top soil loss in
tons per acre based on an erodibility factor for the soil, soil cover
factor, land slope, slope length, and the 30-minute, 2-year frequency
2-2
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Table 2-1. Sediment Process Models
(Source: USGS 1982)
Empirical/component
method
Conceptual
simulation
Statistical
Process
Regression/correlation
Probabilistic
Stochastic
Erosion
llorton, sheet-erosion equation.
ARS, universal soil-loss
equation.
Musgrave, soil-toss equation.
Ellison, soil-splash equation.
Dragoun, sheet-erosion equation.
Negev, sediment-erosion-
transport model
ARS upland erosion model.
Hydrocomp, simulation
programing.
Anderson, sediment-yield equation,
fleming, suspended-load design curves.
SCS, gully erosion equation.
Beer and Johnson, gully growth
equation.
Thompson, gully advance equation.
Frequency analysis of
sediment-yield trans-
port and deposition.
Transport
Schulits, computer programs
for bedload formulas.
Du Boys, transport formula.
Einstein, bedload function.
Colby, modified Einstein
method.
Blench, regime equation.
Laursen, transport theory.
Inglis-Lacey, transport formula.
Toffaleti, transport formula.
Sediment-rating curves.
Random generation of sedi-
ment data.
Sakhan, Riley, and Renard,
simulation of sediment
transport with stochastic
transfer at the streambed.
Deposition
Fall velocity theory.
Sediment suspension/deposition
theory.
Density current theory.
Ackerman and Corinth, reservoir
sedimentation equation.
Thomas, U.S. Army Corps of
Engineers reservoir sedi-
mentation modeL (Also
simulates transport.)
Farnham, Beer, and lleinemann, regres-
sion analysis of reservoir sedimenta-
tion.
Stall and Bartellj, correlation of reser-
voir sedimentation and watershed
factors.
Einstein, bedload function.
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rainfall. These relationships are limited in the areal extent used for
application.
Many formulas have been developed to determine the discharge of bed
sediment under steady uniform flow. Sedimentation Engineering (ASCE, 1975)
presents a number of these formulas, including:
DuBoys, 1879
Meyer-Peter, 1948
Schoklitsch, 1935
Shields, 1936
Meyer-Peter and Muller, 1948
Einstein-Brown, 1950
Einstein Bed Load Function, 1950
Laursen, 1958
Blench Regime Formula, 1966
Colby, 1964
Engelund-Hansen, 1967
Inglis-Lacey, 1968
Toffaleti, 1969
The formulas are based on various governing relationships and incorporate
several flow and sediment characteristics including depth of flow; mean
velocity; bed slope; shear stress; friction factors; particle size,
distribution, and specific weight; and fluid temperature. The accuracy of
prediction is dependent upon the ability to properly identify the governing
parameters. Figure 2-1 shows a comparison between several bed sediment
prediction formulas and observed sediment discharge as a function of water
discharge for the Colorado River. It can be seen that the ability to match
observed data varies considerably between formulas.
The estimation of sediment discharge above the bed is generally based on
sediment and flow observations at gaging stations. The U.S. Geological
Survey (USGS) determines suspended sediment concentrations for many water
quality stations throughout the country from samples collected using depth
integrated samplers. Mean concentrations in the cross-sections are obtain-
ed by taking samples at several vertical locations or by applying a coeffi-
cient to a single sample (Guy, 1970; Porterfield, 1972). For periods when
no samples are taken, estimates of daily suspended sediment loads are based
on water discharge or sediment concentrations immediately prior to or after
2-4
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SEDIMENT TRANSPORTATION MECHANICS
WATER DISCHARGE, cu.ft. p«r MC.pir (t.
Figure 2-1. Comparison of Bed Transport Formulae
(Source: ASCE, 1975)
2-5
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the period. Records of particle size distribution of the suspended sedi-
ment and bed material are also kept by the USGS.
The relationship between sediment discharge rate and flow at a cross-
section may be depicted in a sediment rating curve. Colby (1956) developed
sediment rating curves for six gaging stations in the United .States in
order to study the possible applications of these curves to the estimation
of sediment discharge. An example of an instantaneous sediment discharge
plotted against instantaneous water discharge for the Niobrara River in
Nebraska is shown in Figure 2-2. Colby noted monthly variations in the
sediment-discharge relationship and developed seasonal adjustment factors,
an example of which, for White River, South Dakota, is shown in Figure 2-3.
An example of similar adjustment coefficients to account for variations in
suspended sediment concentrations with a rising discharge hydrograph is
shown in Figure 2-4.
Unfortunately, the timing of sediment concentrations does not always
correspond with discharge. A comparison of different relationships of
sediment concentration with the timing of runoff hydrographs is shown in
Figure 2-5. The relationship of sediment concentration to the hydrograph
has been characterized by Colby (1956):
If the distance of travel from the point of erosion is short or
the stream channels contain little flow prior to the storm runoff,
the peak concentration of fine material usually coincides with the
peak flow, or somewhat precedes it. Peak concentrations of fine
material early in the runoff is consistent with the idea that
loose son particles at the beginning of a storm will be eroded by
the first direct runoff of appreciable amount. However, the flow
from one tributary of a stream or from one part of a drainage area
may be markedly lower or higher in concentration than the rest of
the flow, and the time of arrival of such unrepresentative flow
may determine the peak of fine-material concentration. The peak
of the concentration of fine material may even lag far behind the
peak of the flow, 1f the fine material originated far upstream and
1f, just before the storm runoff, the stream channel contained
large volumes of water having low sediment concentrations.
Figures 2-6 and 2-7 illustrate the variation in suspended sediment concen-
tration to water discharge for rising and falling hydrographs.
2-6
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instantaneous water discharge,in cubic feet per secono
Figure 2-2.- - Instantaneous Sediment Rating Curves for Niobrara
River Near Cody, Nebraskav^CSource: Colby, 1956)
2-7
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Figure 2-3. Seasonal Adjustment to Discharges of Sediment,in Clay and Silt Sizes,
White River Near Kadoka, SD. (Source: Colby, 1956)
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I 1 ' ' I I 1 I L.
0 5 10 15 20 2530 35 40
DAYS AFTER BEGINNING OF RISE
Figure 2-4. Approximate Average Variation of Coefficient of Sediment
Discharge (fines) With Elapsed Time After Beginning of a
Rise, White River Near Kadoka, SD. (Source: Colby, 1956)
2-9
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Relationships With Timing of Runoff Hydrograph
(Source: Guy, 1970)
2-10
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STORM OF OCTOtER 3, IM7
P10E0N ROOST CREEK
WATERSHED 17
NEAR
HOLLY SPRINGS, MISSISSIPPI
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Figure 2-6. Variation in Suspended Sediment Concentration With
Hydrograph for a Low Intensity Storm
(Source: ASCE, 1975)
2-11
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Figure 2-7. 'Variation in Suspended Sediment Concentration With
Hydrograph for a High Intensity Storm
(Source: ASCE, 1975)
2-12
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Colston (Overton and Meadows, 1976) developed a regression model to predict
instantaneous variations of suspended solids concentrations as a function
of water discharge and time elapsed since the start of the storm. The
correlation coefficient obtained from the regression was found to be 0.76.
It is important to note that models developed by optimizing coefficients,
unless otherwise tested, are specific to the area and to the ranges of data
used in the optimization.
A sediment rating curve developed for the Powder River in Wyoming was
developed by Langbein and Maddock (Linsley, et al., 1975) as shown in
Figure 2-8.
Hadley and Schumm (1961) compared mean annual sediment accumulation with
rock type and drainage density in a New Mexico-Arizona study area. Hadley
and Schumm also correlated mean annual sediment accumulation to relief
ratio in 26 basins in the Cheyenne River basin with good results. It was
found, however, that relief ratio was not a good measure of erosion rates
in basins with two distinct types of topography.
The U.S. Army Corps of Engineers Hydrologlc Engineering Center has
developed several computer programs written in FORTRAN to analyze processes
of sedimentation. The first, entitled "Suspended Sediment Yield" (HEC,
1968), performs a complete suspended sediment transport study at a specific
stream gaging station (USGS, 1968). The program has the capability of
performing the following options:
1. The weighted average size distribution and the unit weight of
suspended sediments can be computed.
2. If the user desires, the program will compute the relationship
between the logarithms of instantaneous sediment loads and the
logarithms of the corresponding flows. The resultant regression
equation and correlation coefficients are also determined.
Logarithmic relationships are used to compensate for non-1Inearity
in the relationships between discharges and suspended sediment
concentrations; regressions based on low versus high flow may
differ.
3. Multiple correlations of the logarithms of mean daily sediment
loads against the logarithms of mean dally flows and elapsed time
from previous peak flows can be developed. The regression based on
2-13
-------
Suspended sediment discharge in tons per day
Figure 2-8. Sediment Rating Curve for the Powder River at Arvada, WY
(Source: Linsley et al., 1975)
2-14
-------
elapsed time from previous peak flow is introduced to compensate
for temporally varying sediment load relations as caused by
significant bank and channel erosion and landslides due to major
floods. These conditions can cause temporary sediment concen-
trations of 10 to 20 times greater than expected concentrations.
4. The daily load equation (from part 3) can be applied to measured
daily flows to estimate annual suspended sediment load.s.
The program "Deposit of Suspended Sediment in Reservoirs" (HEC, 1967a)
determines the distribution and location of sediments deposited in a
reservoir, sediment inflow loads, the trap efficiency of the reservoir, and
size distributions of passing sediments. Size ranges of sediment are
routed through sections of the reservoir and deposition of sediment is
computed as a function of sediment size, reservoir temperature, inflow
variation, reservoir configuration, and mode of reservoir operation. An
inflow-duration relationship is used to describe inflow variations of flow
and sediment.
The program "Reservoir Delta Simulation" (HEC, 1967b) computes profiles for
sediment deposits from bed load forming the delta at headwaters of the
reservoir based on total bed load and reservoir cross-section.
The Stanford Sediment Model developed by Neger in 1967 ties suspended
sediment production and transport processes with the runoff dynamics of the
Stanford Watershed Model (Gregory and Walling, 1971). The determination of
suspended sediment, divided into wash load and bedload components, is
controlled by model parameters that must be estimated or established by
optimization from observed data. Gregory and Walling point out that
considerable improvements could be made to the model by Including flood
plain deposition and seasonal effects.
0n1sh1 and Wise (1982) developed the Instream Sediment-Transport Model
(SERATRA), an unsteady, two-dimensional finite element computer program to
simulate sediment transport, dissolved contaminant transport, and parti-
culate transport (contaminants adsorbed by sediment) based on advection,
diffusion, and decay for each of three sediment size fractions. Required
input Includes geometric configuration; particle settling velocities,
2-15
-------
densities, and diameters; critical sheer stresses for sediment scouring and
deposition; diffusion coefficients; contaminant degradation and decay
parameters; and initial condition and inflow concentrations and discharges.
Other models have been developed to simulate erosion, transport, and
deposition of suspended sediments in estuaries. One such model, SEDIMENT
II (Ariathurai, et al., 1977) was developed under the Dredge Material
Research Program of the U.S. Army Corps of Engineers between the U.S. Army
Engineer Waterways Experiment Station and the University of California at
Davis. SEDIMENT II is a two-dimensional finite element model which
requires expressions for rates of erosion and deposition from previous
experimental studies.
2.4 SPATIAL AND SEASONAL VARIATIONS
Soil cover is affected by climate, geology, and meteorology, all of which
in turn are causative factors in seasonal and spatial variations in
suspended sediment.
The amount of erosion can be related to climate or mean annual temperature
and rainfall as shown in Figure 2-9. Erosion 1s minimal at temperatures
below freezing, at rainfall and temperature conditions producing dense
vegetation, and at temperatures high enough to yield low runoff due to
evapotransporation. Maximum erosion occurs at temperatures and rainfall
causing-high runoff and/or poor vegetation cover.
In 1958 Langbein and Schuiran (Gregory and Walling, 1971) related annual
2
sediment yield to annual precipitation for basins on the order of 3,500 km
in the United States. The relationship shows that sediment yield is
maximum for about 30 cm of annual precipitation and a mean annual tem-
perature of 10°C, but 1s smaller for greater annual precipitation. The
variation due to precipitation can be explained by the interaction of
vegetation and rainfall with runoff and erosion. Langbein and Schumm
developed similar relationships of mean annual sediment yield versus
precipitation for other mean annual temperatures.
2-16
-------
Figure 2-9. Relative Erosion as Related to Mean Annual Temperature
and Precipitation (Source: Guy, 1970)
2-17
-------
For many streams the greatest concentrations of suspended sediment occur
during spring runoff. Many streams in the northern and eastern United
States carry an average of 70 to 90 percent of the annual sediment load
during the spring runoff (Guy and Norman 1970). Streams in the Pacific
Northwest, on the other hand, may have highest concentrations during winter
storms. Relationships of instantaneous sediment concentrations to water
discharge can vary on a seasonal basis as shown in Figure 2-10.
Rainwater's Hydrology Atlas of 1962 indicated sediment concentration ranges
over the conterminous United States (Rainwater, 1962). Although based upon
mean annual measurements of stream discharge and sediment load, the atlas
gives a general idea of sediment concentration patterns in the United
States. The eastern United States and the Pacific Northwest exhibit the
lowest sediment concentrations, the middle of the country has higher sedi-
ment loads, and the arid southwest has the most concentrated loads. It Is
quite apparent that average sediment concentrations are much lower below
dams than above.
Wilson (1972, 1973, 1977) has published several papers on sediment yields
in the United States as a function of mean annual rainfall and climate.
The data used to analyze sediment yields represent monthly sediment and
water discharges over periods of at least 3 to 5 years. Data affected by
upstream regulation of flows were disregarded.
In these analyses the "sedihydrogram" (SHG - Figure 2-11), a log-log plot
of mean monthly sediment yield (tons/mi ) versus mean monthly water yield
p
(tons/mi ), was defined in order to illustrate sediment data on a seasonal
basis. Seasonal variations in the sedihydrograms appeared to occur in two
basic patterns. The first pattern (represented by the Eel River SHG in
Figure 2-11) 1s typical for areas along the West Coast, which has a medi-
terranean climate regime. The mediterranean climate exhibits hot sunmers
with little rainfall, and wet winters with a lot of rainfall.
The other two SHG's in Figure 2-11 are typical of a continental climate
regime, which is found throughout the conterminous United States (except on
the West Coast). A continental climate is typified by relatively wet
2-18
-------
LONG TOM RIVER BELOW FERN RIDQE DAM
SEDIMENTATION DATA
Figure 2-10. Seasonal Relationship Between Sediment Concentration, Sediment Load,
Discharge, and Precipitation for Fern Ridge Dam, Oregon.
(Source: Thomas, 1970)
-------
10 000.
nooi ftOl
™ I I I I mil
Sediment yield as a function of climate in US rivers
RUNOFF: MILLIMETRES PER MONTH .
r i r i n?f—i i i miiIf—r i mm?—r-rr
2 i ooo
<
D
a
~>
x
V*
z
2 .00
z
$ 10
a
Q
z
&
-<¦'
/ / i ' /
/ ¦ / U / -
hilLl i ¦ i i niii^ i ?¦ i i mil/'
'I''
10 H» 1000 10 000 100 OOO
MEAN MONTHLY WATER YIELD: TONS/SQUARE MILE
1 I I I
w
Z
c
I
oat z
0.00)
6!
s
o
z
04001
040001
1000 000
Figure 2-11.
Sedihydrograms (SHG) for Rivers Influenced by
Different Climates (numbers denote months, i.e.,
l=January, Source: Wilson, 1977)
2-20
-------
summers; often with short, intense thunderstorms. Winters are generally
cold and dry in the west, mild and humid in the east.
In addition to climate, factors such as land use, lithology, soil type, and
vegetation also affect sediment yields. In Figure 2-11, the Paria River in
Arizona and the Tradewater River in Kentucky are both areas with a con-
tinental climate. The SHG's are different because the runoff from sunrner
thunderstorms in the semi-arid west is not hindered by vegetation, and
sediment is flushed into the streambeds. In the east, less runoff is
carried into streams during short storm events, so a corresponding sediment
increase is not observed.
Figure 2-12 illustrates the effect of land use on the SH6 for two sites in
Maryland. The agricultural site (Monocacy River) 1s fairly well vegetated
and hence the summer sediment peak is not so pronounced. In the nearby
urban area (Anacostia River), the summer sediment discharge peak is higher
than that of winter.
Wilson (1977) presents an unrefined model which relates types of air mass
to water yield and sediment concentration, and ultimately to sediment
yield (Figure 2-13). Table 2-2 sums up the relationships in Figure 2-13.
The air mass abbreviations in Table 2-2 stand for:
mT - maritime tropical, dominant summer air mass in east
cP - continental polar, dominant winter air mass over north-central
portions of the country
mPa - eastern U.S. 1n winter; mixture of mT and cP
mPb - central U.S. 1n summer; mixture of mT and cP
mPc - maritime polar, dominant air mass of Pacific Coast in winter
cTu - western U.S. in summer (except coast)
mTs - Pacific coast in summer.
2-21
-------
tUNOW: MRllMlTCtS K1 MONTH
Figure 2-12. Effect of Land Use on SHG for Two Sites in Maryland
(dashed line is for Anacostia River, solid line is
Monocacy River). (Source: Wilson, 1972)
2-22
-------
Figure 2-13. Relation of Air Mass Types to Sediment Yield
(Source: Wilson, 1977)
2-23
*> - * '
-------
Table 2-2. Relation of Air Mass Types to Sediment Yields
(Source: Wilson, 1977)
Air mass controls of water yield or runoff (W), suspended sediment concentration (Q, suspended sediment yield (S)
Air mass
W
C
S
mT (summer)
Moderate; limited by loss
to soil, plants, despite
much rain
Low;limited by plant
cover despite high storm
energy, frequency
Low; limited by low W, low
to moderate C; vulnerable
to vety poor lapd use
practices
cP (winter)
Low during time of snow
cover; after cP is gone
melt W can be large
Very low, especially
while snow on ground
Very low, laigest when W
is large
mPa (winter
east)
Very large if melt or
rain is large, soils wet
Low, especially whQe
snow on ground
Moderate; largest when W
is large
mPb (summer)
Low-moderate; limited by
loss to soil, plants
Low-moderate, limited
by plant cover, few
storms
Low-moderate; very
vulnerable to improper land
use practices
mPc (winter
west)
Very large if melt or
rain is large, soils
wet
Moderate to high from
riin; low from melt
Moderate to very large,
especially when heavy rains
follow dry season
cTu
(modified
summer)
Limited by little rain,
dry soils
Very high due to poor
plant cover, intense storms
Low if li' very low.
otherwise moderate to very
large
mTs
(stable
Virtually none, except from
antecedent conditions
Limited due to rare
storms
Low because rain, runoff
limited
summer)
-------
Figure 2-14, based on regression analysis of 100 basins in the United
States, illustrates the use of air masses on the SHG. In conclusion,
Wilson writes:
Where sediment yield data are absent or inadequate, it may be
useful to evaluate the climatic variables occurring in a g.iven
basin and to rough out the probable SHG for that basin. This will
be facilitated if the general shape of the SHG can be approximated
by using data obtained from a gauged stream with the same climatic
regime.
Given the approximate SHG, it will be possible to identify seasons
In which field measurements will be especially critical 1f sedi-
ment transport relationships are to be established and sediment
yield is to be predicted with some accuracy. Sampling will be
most important when sediment movement 1s large and variable. This
situation will occur most commonly during periods when sediment
concentrations are large, but runoff Is not. In terms of the SHG,
periods plotting above and to the left of other periods will be of
most interest. In Figure 2-14, months which are expected to plot
in the vicinity of cTu and mPb would properly be the focus of
rather intensive sampling, in order to capture the inherent
variability of sediment transport, and to estimate the large
volume of sediment transport expected to occur.
In contrast, comparatively little sampling would be needed for
periods in which there 1s little sediment movement. These months
plot towards the bottom of the SHG. Similarly, during high flow
periods when sediment transport is relatively steady, it should be
possible to evaluate sediment yield with only a few samples.
These periods will plot to the right of the SHG. For all periods
of Interest, samples taken early 1n the season will be more
Important than those taken later, because of the fact that the
early flows tend to be the more turbid.
These procedures outlined above have not been applied, nor worked
out in detail. However, 1t seems reasonable to expect that by
recognizing seasonal patterns 1n sediment transport relationships,
fairly reliable sediment yield estimates could be made based on a
small number of carefully planned samples (perhaps only a few
dozen), provided that runoff quantities can be estimated with some
accuracy. Extensive data gathering efforts, such as the daily
sampling often employed In the USA, are not essential unless
extremely accurate transport curves are needed. Rather, a more
limited sampling program can normally provide effective results,
with consequent savings of limited funds and manpower.
In a paper on river sediment 1n the Atlantic coast drainage, R.H. Meade
illustrated spatial and seasonal differences between four rivers draining
to the Atlantic (Meade, 1982). Two of the rivers, the Juniata (PA) and the
2-25
-------
10000
RUNOFF: MILLIMETRES f£R MONTH
T1 i in imT—i in "W—i i 111 ii If—i i 11 mi?—i i i i mif
-=jta
01
0
m
z
c
1
001 2.
0001
ja
m
v*
s
o
z
ooooi
_J0.0000l
n too iooo to ooo iooooo
MEAN MONTHLY WATER YIELD: TONS/SQUARE MILE
1000 000
Figure 2-14. Generalized Sediment Transport and Yield Conditions
Associated With Common U.S. Air Masses
(Source: Wilson, 1977)
2-26
-------
Yadkin (NC), carry more sediment in the summer than in the winter for a
given stream discharge. The other two rivers, the Merrimack (MA) and the
Edisto (SC), do not exhibit this tendency. For three of the four rivers,
it can be said that suspended sediment is postively related to stream
discharge. For all four, flows in winter are higher than those in summer
(this fact corresponds well, incidentally, with the sedihydrog'rams
developed by Wilson, 1977). The measured ranges of sediment concentration
for the Juniata, Merrimack, Yadkin, and Edisto Rivers are, respectively,
1-700 mg/1, 1-290 mg/1, 20-1900 mg/1, and 3-60 mg/1. The approximate
median concentrations in mg/1 are, In the same order, 25, 10, 85, and 7 for
winter (cool season) and 15, 9, 130, and 9 for summer (warm season).
Meade analyzed the graphs as per region:
The sediment-streamflow relations show some strong contrasts from
one river basin to another. In the two rivers in the northern
Atlantic states, sediment concentration is closely related to
streamflow during both seasons in the Juniata River (F1g. 2-15a),
but apparently only during the cool season in the Merrimack River
(Fig. 2-15b). The poorer relation between concentration and
streamflow in warm season and the generally low concentration
during most of the year 1n the Merrimack probably reflect the
lower sediment yields that are typical of the rivers of New
England and other areas that were intensely glaciated during the
most recent ice age. Concentrations are consistently highest and
Increase most sharply with streamflow 1n rivers of the southern
Piedmont (Fig. 2-15c); because of these consistently high concen-
trations, the sediment yields from the Piedmont are consistently
the highest per unit area of any physiographic province on the
Atlantic slope. In the southern Coastal Plain, by way of con-
trast, sediment concentrations are consistently low at all dis-
charges (F1g. 2-15d) and the sediment yields per unit area are
among the lowest on the Atlantic slope. The southern Coastal
Plain Is typically a lowlying area of permeable soil and poorly
consolidated bedrock 1n which, even though rainfall Is often more
intense than on the Piedmont, streams respond more sluggishly to
storms.
In an analysis of sediment problems 1n the Savannah River Basin, Meade
(1976) analyzed discharge versus suspended sediment concentration and
distinguished between two physiographic regions (Figure 2-16). Meade
concluded that a Piedmont stream can be expected to carry about 10 times
2-27
-------
1000 -
100 r
Ol
E
z
HI
2
Q
111
<0
Q
Ui
Q
Z
UJ
a.
en
3
W
10 r
cr
i
r
L
i
1000 L-
P
r
100 :
10
1 K
i r
P i
: C
Cr= Ad #
11 III
10
100
1000
10
100
1000
WATER DISCHARGE (m7s)
Figure 2-15. Suspended Sediment Concentration Versus Water Discharge
for.- A) Juniata River at Newport, PA; 8) Merrimack River
at Lowell, MA; C)Yadkin River at College, NC; D) Edisto
River near Girhans, SC. (Dark circles represent cool
season, open circles warm season. Source: Meade, 1982)
2-28
-------
500
100
SO
10
100 1000 10
WATER DISCHARGE (CUBIC M PER SEC)
. 1 1 1 1 1 1 1 1
1 l 1 1 1 1 1 L
•
-
1 1 1 L 1. 1 1 1
•
. • \
V -!•.
• • •
'
• •••
• ••JPnj
i i i t i i 11
too
1000
Figure 2-16. Suspended Sediment-Water Discharge Relationships for a
Piedmont Stream (left) and a Coastal Plain Stream.
(Source: Meade, 1976)
2-29
-------
the concentration of suspended sediment that a Coastal Plain stream would
carry at the same water discharge.
In 1973, Curtis, et al. published a pamphlet on fluvial sediment discharge
to the oceans. The nation was divided into 27 drainage basins which drain
into the oceans (Figure 2-17). The closed basins of the west (flows
totally contained inland) and the Great Lakes Basins were excluded from the
study. Sediment concentrations were calculated by dividing the average
annual sediment discharge (tons) by the daily average water discharge (cfs)
and converting units to mg/1. Sediment concentrations calculated by this
method ranged from 15 mg/1 In southern Florida to over 1600 mg/1 in parts
of California (see Table 2-3). Note that these values were 1n most cases
calculated from data near the coast, or close to the mouths of the rivers.
Upstream levels may be either higher or lower, depending upon upstream
characteristics. For example, the sediment concentrations may be very high
far upstream, but sedimentation in a series of reservoirs may reduce these
concentrations, resulting 1n lower sediment discharges downstream.
At a conference on sedimentation held in 1970, Thomas presented a paper
dealing with sedimentation in the Pacific Northwest. The paper covered
sediments in the Columbia River Basin, the portions of the Closed and
Klamath Basins located in Oregon, and the Washington and Oregon coastal
drainage systems.
Data indicate that sediment concentrations are generally low west of the
Cascades, averaging about 25 mg/1 1n times of low flow and from 200 to 300
mg/1 during flood periods, with a recorded maximum of 800 mg/1. Much of
the sediment 1s deposited in the many reservoirs and at other control
projects located in the region.
Sediment concentrations may be significantly higher in the smaller streams
east of the Cascades, where Increased agriculture has increased erosion
rates. No concentrations are given for these smaller streams, but exces-
sive sedimentation has been discovered where these small streams enter
reservoir waters. Again, widespread regulation of flows probably helps cut
down on sediment concentrations further downstream.
2-30
-------
hXWh- m
B R X fe*,A
i4r«°)sk
i V: , :i
' 6 *3V
j AKKAN^ij/r.' #
EXPLANATION
T -Daily i«din*nt (lotion
V — Ml«c»llon«out concentrations
Y/A~Non contributing aroa (closod batin)
[X]—Sourli, Red, Rainy, Oroat l.akos,
and Si. Lowr«n<« drainage
not Included In iKU report
20—Drainag* aroa nunbir
(So* table 4)
'^»s\v4 ,fp
0 100 200 30OKlL0M£TERS
Figure 2-17. Drainage Area and Location of Sediment Sampling Stations (Source:
Curtis et al., 1973)
-------
Table 2-3. Measured Sediment Concentrations
Selected River Basins
(Source: Curtis et al ., 1973)
for
Dniuit ir«
< Sao ftfuro I oad UM t for lecBUee. )
No.
Nib
Waior
diockar«o
Period
Gub4o Cubic v(
Souaro Souaro motor* foot roevrd
kUo- nitoa p*r por
Avoraoo annual mipinW irtiwwi-
Dlocfcarfo.
in thousands of
waa por rear
Momo
ton*
Short
ton*
Yi«4d. in
(An* por
aquoro kilo-
Mitrlc Short
u>na u>iu
Coneon*
viiiun
in miln>
Com*
P*r
litof
4. Ai
1. PimmmmM? 8oy to Praubocou Bir. 30,047
t. St. G*oro« Rivor to Cap* Cod B«y 54.134
J Capo Cod Mo* to Now York*
Coanocttcut Siato lino ............ 4141?
4. N«« Yort-ConnMimi Stato lino to
Capo May 50.Ml
5 Copo May to Com Hoary 2M4N1
~. Ma»oro Rivor at Trenton. N. J . 17 440
~. Suaquabaaaa Ri«*f at Harm barf.
P»' 42.419
c Potomac Rivtf at Potnt of Rocka,
Md ti.m
I Copo Hoary to Novao Rivor 73.1*9
o. Tor Ri»«r at Tarboro, N.C 1.141
7 Covo Sound to Block Rim .......... 71447
a. Pao Doo Rlvtr at Poo Doo. 1 C .. ZS.nlO
0. Soatoo River to Sopot* (aland ....... 102416
a. Ocoochoo Rivor near Cdoa. G* ... 4.M1
b Cdloto Riwr hit Glvhaaa. & C .. 7,971
• Alia ma ha Ri«*r to Copo Konaody 77,110
10. Copo Koaoody to Copo SaMo C2*467
ToUi or annual .......... 741,7(0
II Capo SoMo to Alligator Croat B16440
12. Pnci Mlvvr to Nn Rim .......... (T.IN
IX Apoiackieoia River 61400
a. AptucfewoU Rivor at Hamfcon
ehco. Flo 44J4I
14. W«u»po Crook to Pordido Rivor .... 14,77*
16 MuMt Boy - 114.727
a. Toabubw Rivor noor Jackaoa.
Mb 40.71*
h Alabama Rtvar ai Claibom*. Ala. M.iM
1*. Paacaouvla Rivor to Ptori Rivor ..... 61.0X2
a. Prart Rivor noor BooaJuao, La... 17.172
17 Miaaiaaipp* Rivor MJU.M
a Mtaoiaotpp* Rivor at Rod Rivor
UadiKf (mo toot I ......... tiOJII
b. AtcfcoJoJaya Rivor laoo tool) ..
I* VtnaillM. MmaoaUu. and Coieaaiou
Rivff* JWW
19 Sobino Riv«r to Rio Grand* ......... *74.93*
a. Bra too Ri«or at Richmond. Tot . 114.012
b Colorado Rivor at Coiumbua. Tfi. 100.171
c. Nuocoa Rivor n*or Throo Rivor*,
Too 40.404
d Arroyo Cderodo at Mrreodao, ToO
Rio Grando noar Browaavilto. I
To*.. North Floodway n«ar \ Hd
Sofcaotian. To«. J
Total or annual av*ra** ..... 4.M4JW
U.401
20.901
1.161
19.4M 9t9
TtiM 2J44
6.7*0
9.Ml
20.202 770
2.140
29.002 M
*410
It.&U 900
2.010
2.720
20.700
CII400
72t
2M
21.100
41,020
32.770
101400
1900 69
1904-00
1901 09
27400
1909 47
21.400
1907 6*
224*0
1900 04
1907 00
22400
9.000
207.1«0 10.100 209400
B. Golf of Mootoo
E0.000 71 2.000
20.10O 770 27400
20.000 7M 24,700
17400 1907 19
14406 7U U.I00
44.200 141* 04*200
14.200 1902 14
22.000 1902 09
19.700 KM 21400
4.000 1907 M
1401.000 IH.400 000.000
1.120.900
1000 09
*.790 900 10400
13*490 1.407 40.700
44.020 1900 40
41.070 |957 49
16.64
1901 62
Hd Ni 1900-01
1.729.200 2ft. I tO
c7T
471
440
11 9
394
20
1.179
i.aoo
21 0
42.2
32
700
M0
16 8
47 9
26
*70
1.070
19 2
58 0
11
5.262
5.K00
26.6
73 2
60
400
740
U.7
111
1.771
1.962
21.4
81 0
721
7M
2*9
41 4
1.101
1.500
1* 4
53 1
64
100
116
19.0
54 1
1.270
1.400
16 9
4* 2
" SO
401
442
17 S
16 2
*44
1.040
9 2
24.3
'*30
&6 M
41 4
* 1
212
....
19 1
21 1
1.7
7.7
&H0
640
7 6
21 6
26
122
124
4 2
11.9
16
114*4
14404
17 2
49.6
40
a 0
17 0
2 2
4 1
16
Ml
400
6.4
16 3
11
t&4
.190
4 II
19.6
16
157
171
3 S
10.1
HOT
I.OOO
24 4
70 4
" * 40
440»
4 900
54.4
1M
100
2424
2.454
44 *
120
i.W
402
116
tan*
i.500
44 6
127
"*oi
71
2.000
17 %
51
—
445
491
lt.O
31 S
....
1.229
1.166
N d.
N d.
....
14.1.QK0
17*.179
74 1
217 4
412
tO Colorado Rivor ........ — ....
o. Colorado Rivor at Mlcool C
Rodrtqwva. Moxko ...........
21 Tta Juaaa Rivor to Vmiur* Rivor ...
a. San Juaa Crook noar Saa Juaa
Capiairtno. Calif ............
b Santa Clara Rivor at Satlooy.
Calif
a Saa Jooo Crook to Paaadoro Crook ....
a. Soilnoo Riv*r noar Sprocket*.
Calif
23. San Pranotaco Boy
a. Saa Joaoala Rivor noar Vonwtte.
Calif
b. Conoumnoa Rlvrr at HMilia* B%r,
Calif
c. Sacramoato Rim at Sacramoata,
Calif
14. LonaitM Crook to Satfth Rtvor ....
a. Ruaalaa Rivor noar Guoniovttlo.
Calif
b. Eol Rivor at Scotia. CaJif
c. Mad Rivor at Areata. Calif
d. Klaiaath Rivor at Ortoaaa. Calif .
o. Trinity Rivor noar Koopa. Califa.
21. Orocon eoaotai aroa ...............
a. Siuolaw Rivor noar Mapioton. Orof
b. Slia Riv*r at Siia. Ong ......
e Routo Rivor at RayeoH, Oro# —
20. Columbia Rivor ....... ........
a. Columbia Rivor at Vancouver,
Waah
27. Naarilo Rivor to Nnokaack Rivor ....
a. Cfeofcalii Rlror at Portor, Wook .
b. Skykomtok Rivor at Monroo. Wtak
c. SaoQualmto Rivor noar Carna-
tion. Waah
d. Skaoit Rivor noor ML Vornon.
Waah
Total or aaaaal avoraco ...
414460
146,000
1.8
M
»4
100
0016 004
IM
*14400
146.000
1 *
*6
1946 49
0 A
m 4
0.016 04
1.434
21471
11.1*0
14
600
710
*00
2-11
M
171
too
IM7-M
a 5
44 3
211
190
4.121
1496
1900
4* 7
75 7
10 0
47 6
2*401
11.110
M
' 2^400
1.320
1.440
116
319
1440
10.747
4.167
19M 9t
511
6M
49.1
141
*111400
•46470
"mi"
30.400
1.261
VIM
204
76.4
110
16.000
11440
1950-41
.150
.1M
10
29.1
1.3M
510
1941—49
142
15*
101
296
40.941
21410
......
1947-49
2.404
2.719
40 4
no
M414
11410
1.191
41.100
01.521
67410
1.089
1.101
1480
2.471
1440
1960-49
4.111
4,86*
1,101
1.401
0.041
1.112
..
.....
1*U 69
10.411
29.346
3.101
*.410
....
I4M
4tt
.....
1907 69
2.441
24*1
1444
644*
....
2141*
*400
.....
1907 M
2.309
2.M1
108
310
....
7,420
2400
_
...
1900-09
4.907
6.4*7
071
1.919
4i.ni
JO09
140*
6J400
...
2.9*1
3400
00.1
196
41
1411
6M
.....
1900 0*
104
114
60.1
191.*
....
100
110
.....
1901 0*
19*
210
M2
1,097
....
6417
1.061
.. „
.....
1*11
592
66.1
11.1
.114
660,730
260400
7.901
2*1400
14.170
16.410
81 1
006
M
414.190
241.000
1M4 4*
9.704
10.4*7
164
44.4
60.790
19:410
"2411"
Mj'ob
1,071
4470
76.1
118
"*49
¦V1SI
14*4
......
.....
1901 40
116
117
14.2
97 9
....
1.140
*14
1907-49
244
20*
113
321
1.M1
401
I960 6*
201
290
168
4*1
Mil
2.0*1
......
.....
1*10
310
•104
41.1
11*
1417.941
411.410
14.1114
490,000
99.0712
99.0M.4
64.*
IM.6 101
' Throo dam* botwooa ccatloa and aovll o< I
* Trtbatary to Klamath Rivor.
2-32
-------
2.5 RATES OF EROSION AND SEDIMENT LOADING
Loehr, et al. (1979) have estimated nonpoint contributions of sediment to
surface waters, in million tonnes (1 tonne equals 1.1 tons) per year, as
follows:
Cropland
1,700
Pasture and range
1,190
Forest
232
Construction
179
Mi ni ng
54
Urban runoff
18
Rural roadways
2
Natural (background)
1,150
Total
4,525
Of these sources, agricultural accounts for about 65% of the total, cul-
tural activities account for 75%, and natural loadings account for about
25%. Novotny and Chesters (1981) estimate that over 4 billion tons of
sediment are delivered annually Into streams and rivers of the United
States, almost half of which originates from approximately 170 million
hectares of agricultural land.
Brant, et al. estimate that the average rate of natural erosion is 40
tonnes/km^/year; that agricultural erosion may range from 100 to 4,000
p
tonnes/knr/year; while sediment yields from urban developing areas may
reach values of 50,000 tonnes/km^/year.
The total sediment load in a stream may be divided ino bedload and wash-
load, where washload refers to the suspended fraction. Measurements of
sediment movement in lowland, largely agricultural areas indicate that
washload may account for 90% to 95% of the total sediment load (Novotny and
Chesters).
2.6 IMPACTS OF ANTHROPOGENIC SUSPENDED SEDIMENT
The impacts of urbanization and other development have been shown to both
accelerate and reduce natural erosion processes. Some of the most
significant Increases in suspended sediment have occurred by disturbing the
soil through agricultural, strip mining, and construction activities. On
2-33
-------
the other hand, many activities in the arid southwest reduce suspended
sediment through the introduction of vegetative cover for agriculture and
by trapping sediment in reservoirs. In addition to being a major pollutant
in itself, sediment serves as a carrier for other pollutants such as
adsorbed phosphorous, nitrogen, and other organic compounds, and for toxics
such as pesticide residue and metals.
Meade (1969) estimated that the conversion of forest land to farms in areas
around the Potomac and Susquehanna River basins near Washington, D.C.
caused about a tenfold increase in sediment yield. It is estimated that
logging activities in Oregon and California yield three times as much
sediment per unit area as forested land (Meade, 1969).
Camp Dresser & McKee (1983), in a study of the effects of urbanization in
Northern Virginia, compiled data on annual sediment loading rates ranging
from under one ton per acre per year (t/a/y) for naturally vegetated areas
to from one to three t/a/y for stabilized urban areas, and 50 to 100 t/a/y
for uncontrolled urbanizing areas.
In addition to overland soil loss, urbanization can cause Instability 1n
the stream channels themselves. Higher peak discharges and runoff volumes
resulting from developing areas increase the erosive forces on the channel
banks.
Man's activities affect sediment concentrations in different ways. It is
well known that construction/urbanization activities tend to increase
sediment concentrations many-fold. However, the construction of reservoirs
to harness hydroelectric potential and/or control flooding has brought
about a decrease in sediment concentrations in many places. Meade reported
(1982):
Two examples from the Atlantic drainage show the reduction 1n
sediment that can be caused by reservoirs on the principal rivers.
A before-and-after example Is provided by the data collected from
the Roanoke River at Scotland Neck, North Carolina, before and
after the completion of a large flood-control reservoir about 125
km uprlver 1n 1952 (Figure 2-18). Concentrations of suspended
sediment at equivalent water discharges were about an order of
2-34
-------
KERR RESERVOIR
LAKE GASTON
' ROANOKE
RAPIDS LAKE
Roanoke Rapids
Scotland Neck
ALBEMARLE
SOUND
50 km
_ 100
z
tu
s
5
ui
V)
O
Ui
O
10
9i
3
co
I Mill
1—I I I I I II
• #
% •
• •
• •
• •
•°0*o°
•
1945
o "
• •
CO o
o
<8 o o
o o o eg)
OOO o
1954
' i i i i i nl
100 1000
WATER DISCHARGE (m3's>
Figure 2-l£. Comparison of Suspended Solids Concentrations in Roanoke
River at Scotland Neck, NC, Before (dark circles) and
After (open circles) Kerr Reservoir was Completed in 1952.
Note: Lake Gaston and Roanoke Rapids Lake were not formed
until after 1954. (Source: Meade, 1982)
2-35
-------
magnitude smaller after the reservoir was completed than they had
been before. This suggests that Kerr Reservoir effectively
trapped about 90% of the sediment that the Roanoke formerly
carried past Scotland Neck.
An inflow-outflow example is shown in Figure 2-19. A pair of
reservoirs was completed in 1941 to generate hydroelectric power
from the waters of the lower Santee River of South Carolina. Data
collected between 1966 and 1968 showed that the water in the
tailrace just below the second reservoir carried only about a
tenth of the sediment that the river carried into the first
reservoir. Apparently the trap efficiency of these reservoirs is
about 90%. <
There is also evidence that large storms often flush previously deposited
sediment from the reservoirs, increasing sediment concentrations down-
stream. Another adverse effect sometimes caused by reservoirs is the
scouring of the channel below the dam. Meade cited an example of this
occurrence on the Savannah River in the southern Coastal Plain (Meade,
1982). Analysis showed that the larger sediment loads observed at a
downstream station after completion of an upstream reservoir were
attributable to stored sediment being eroded below the dam (sediment
previously stored in the bed, banks, etc.).
2.7 SUMMARY
The previous sections illustrate that the components or factors involved in
sedimentation are complex and that suspended sediment concentrations vary
both spatially and temporally.
Although each individual process 1n landform development is deterministic
in itself, the complexity of the Interrelationship between climate,
geology, the influence of vegetation, and the chance occurrence of
governing events on landforms is such that the exact instantaneous sediment
discharge 1s difficult to predict.
It is not unreasonable to assume, however, that particular basin character-
istics, although varying from one basin to another, will belong to a well
defined unique distribution as determined by local climate and geology and
that these characteristics are indices to hydrologlc behavior and sedi-
mentation. Regardless of geographic location, lithologically similar land
2-36
-------
Figure 2-19. Comparison of Suspended Sediment Concentrations in the Santee
River, SC, Before Entering (dark circles) and After Leaving
(open circles) Two Large Reservoirs. (Source: Meade, 1982)
2-37
-------
areas subjected to comparable climate exposure and land uses will display
similar suspended sediment concentrations.
2-38
-------
3.0 IMPACTS OF SUSPENDED SOLIDS ON AQUATIC LIFE
3.1 INTRODUCTION
In the discussion to follow, the effects of suspended sediment on aquatic
life have been divided into the general categories of lethal and sublethal
effects. Lethal effects are those which are directly associated with the
death of the biota. Such effects are generally not difficult to quantify,
as the endpoint is defined by the organism's death. Sublethal effects
include consequences of suspended sediment that may be harmful to biota in
terms of overall survival, such as effects on feeding and reproduction.
These cause-effect relationships are more difficult to assess in short-term
laboratory tests.
The lethal and sublethal categories provide a parallel to the ambient water
quality criteria that provide for the protection of aquatic life from acute
and chronic effects. The terms acute and chronic will not be used in this
report because these terms both imply health effects. Since suspended
sediment in a stream may have deleterious effects on aquatic life that are
not necessarily health effects, it was felt that the term 'chronic1 should
not be used.
Lethal effects are generally studied with regard to consequences to fish,
although suspended sediment may also be directly responsible for deaths of
zooplankton and macroinvertebrates. Suspended sediment acts directly upon
the gills of fish. The gill filaments and the secondary lamellae act as a
sieve that traps particles that subsequently clog the gill, resulting in
asphyxiation (O'Connor, et al., 1976). Sediment that has settled from the
water column may also have a lethal effect, smothering bottom-dwelling
organisms and f1sh eggs. The effects of sedimentation will not be dis-
cussed in detail in this report although they do have important conse-
quences to aquatic life.
Suspended sediment causes a variety of sublethal and other effects, Includ-
ing consequences to feeding, reproduction and physiological processes of
organisms. Feeding of zooplankton and macroinvertebrates may be inhibited,
eventually causing starvation. An increase in macroinvertebrate drift may
3-1
-------
be caused by increases in solids concentrations and sedimentation. Fish
are also affected by the loss of zooplankton and macroinvertebrates, which
are important constituents of fish diets. In addition, increased turbidity
inhibits fish feeding by obscuring prey from the view of sight-feeding
f i sh.
Suspended sediment may delay the development of fish eggs, and reduce the
growth of larval fish. Such sublethal effects put fish at a competitive
disadvantage. Other consequences of high suspended sediment concentrations
are reduced resistance to disease and damage to gill tissues. Gill damage
caused by suspended matter reduces the respiratory surface area and
interferes with oxygen-carbon dioxide transport. O'Connor, et al. (1977)
measured several parameters which change in response to interference with
oxygen-carbon dioxide exchange. High suspended sediment concentrations
evoked responses similar to those observed when fish are deprived of
sufficient oxygen: increased blood cell count, increased hematocrit, and
increased hemoglobin concentration in the blood. Increases in these
parameters raise the blood's oxygen exchange capacity.
Although sedimentation effects will not be covered in detail in this
report, it is important to recognize that habitat changes caused by the
scouring and filling of pools and riffles affect the success of species
propagation. Sediment deposition affects the permeability of gravel, water
circulation, and dissolved oxygen levels, which 1n turn affect the suita-
bility of an area for spawning. Loss of spawning grounds 1s a major
contributor to the decline of fish populations.
Several factors should be considered when the effects of suspended sedi-
ments are examined. Rogers (in O'Connor, et al., 1976) concluded that the
lethal effect of suspended sediment is dependent on particle shape and
angularity rather than on size. This relationship may result from angular
particles having a greater affinity for the gill surface, thereby causing
abrasions or anoxia. Other investigators have also documented varying
effects for different types of sediment suspensions (European Inland
Fisheries Advisory Committee, 1964; O'Connor, et al., 1976).
3-2
-------
The organic content of suspended sediments can influence the effect of
sediments on aquatic life. Sediments containing a large fraction of
organic material may significantly deplete dissolved oxygen as the organic
fraction decays. Toxics sorbed to sediment particles may also affect the
consequences of suspended sediment to aquatic organisms, and sorbed toxics
may be resolubilfzed when bottom sediments are resuspended. ..
The lethal effects of suspended sediment on fish species may be different
for different stages in the life history. Juveniles are generally more
susceptible to suspended sediment than are adults. Thus, 1t 1s Important
to consider the lifestage that 1s present during conditions of high flow
and increased suspended sediment concentrations.
The following sections contain information concerning the effects of
various suspended sediment concentrations and turbidities on aquatic life.
Both lethal and sublethal effects on primary producers, zooplankton, macro-
Invertebrates, and fish are included. The studies that are reviewed in
this report examine the effects of Inert particles on aquatic biota, and do
not include data on contaminated or highly organic sediments.
3.2 EFFECTS OF SUSPENDED SEDIMENT ON PHYTOPLANKTON AND ZOOPLANKTON
Although many studies report decreases in primary productivity because of
increases in suspended sediment 1n water bodies, there is a paucity of
information in the literature that quantifies changes in primary production
caused by known solids concentrations. Similarly, the effects on zoo-
plankton are rarely quantified, while the lethal concentration of suspended
sediment to zooplankton is essentially unknown.
Van Nieuwenhuyse (1983) studied the effects of turbidity and settleable
sol Ids on the productivity of benthic algae. The cause of increased
turbidity in the Alaskan streams, examined in this study, was sediment from
placer mining operations. Moderately mined streams, which generally
contained settleable solids concentrations less than 0.1 mg/1 (mean
turbidities below 200 NTU), exhibited nearly twice the productivity of
heavily mined streams. Settleable solids concentrations in heavily mined
streams averaged more than 0.2 mg/1.
3-3
-------
The impact of suspended sediments on net plankton (larger than 20 um) has
been studied by Buck (in Muncy, et al., 1979). Surface tows of clear ponds
(suspended solids concentrations less than 25 ppm) yielded plankton volumes
8 times and 12.8 times greater than in intermediately turbid and muddy
ponds, respectively. Ponds with suspended sediment concentrations between
25 ppm and 100 ppm were considered intermediately turbid, whf>e muddy ponds
had concentrations of more than 100 ppm suspended solids.
Monsettleable solids concentrations of 10 mg/1 did not inhibit the growth
of the algae Scenedesmus abundans. Friant, et al. (1980) observed the
effect of nonsettleable solids concentrations of 10 mg/1 in a 7 day
experiment, and concluded that there was no significant change in light
transmission or growth of Scenedesmus abundans.
Photosynthesis 1n vascular aquatic plants is inhibited because of decreased
light penetration caused by sediments. Furthermore, sediments that settle
onto the leaves of aquatic plants may further reduce photosynthesis. Robel
(in Muncy, et al., 1979) reported an inverse correlation between turbidity
and production of sago pondweed (Potamogeton pectinatus). While the
qualitative effect of suspended sediment on vascular plants is understood,
there are few studies that correlate known sediment concentrations with
measured effects.
Increased concentrations of suspended sediments also stress zooplankton.
McCabe and O'Brien (1983) studied the effects of suspended silt on feeding
of Daphnia pulex. Both filtering and assimilation rates were severely
depressed at low concentrations of suspended silt and clay. A turbidity of
only 10 NTU decreased filtering rates, and assimilation was decreased by
more than 55 percent.
Arruda, et al. (1983) studied the effects of sediment on ingestion and
rates of incorporation of algae by Daphnia sp. They observed a 70%
decrease in efficiency when Daphnia, exposed for 1.5 hours, were fed in
solutions containing 10 mg/1 of sediment. There was an 85 percent reduc-
tion in the ingestion and incorporation rates when sediment levels were as
low as 100 mg/1. Ingestion rates of Chlorella vulgaris by Daphnia parvula
3-4
-------
and pulex were decreased by 95 percent when suspended sediment con-
centrations were increased from 0.0 mg/1 to 2,451 mg/1.
3.3 EFFECTS OF SUSPENDED SEDIMENT ON MACROINVERTEBRATES
Much of the information concerning the effects of suspended sediment on
freshwater macroinvertebrates deals with macroinvertebrate drift. The term
"drift" refers to the downstream transport of insects and other inverte-
brates in flowing waters. Rosenberg and Snow (1975) contend that drift and
the subsequent decrease in standing crop is caused by sedimentation rather
than suspended solids, although drift 1s often correlated with increases in
suspended matter.
A study in which sediment was added to a river in Indiana showed increased
invertebrate drift with increased suspended sediment concentrations
(Gammon, in Rosenberg and Snow, 1975). Gammon reported that the numbers of
drifting macroinvertebrates increased 1n a roughly linear fashion with
increases in sediment concentration up to 160 mg/1. However, he did not
attempt to explain decreases in numbers of invertebrates drifting at the
two highest sediment concentrations tested (Table 3-1).
Sediment additions to riffles on the Harris River, Northwest Territories
(Canada) revealed that concentrations as low as 100 mg/1, for a 15 minute
duration, caused increased drift of a mixed Invertebrate population, and a
loss of 0.04 to 0.5 percent of the standing crop (Rosenberg and Wiens,
1975). Sediment concentrations of 250 mg/1 (15 minute exposure time)
caused a 2.6 percent loss of the standing crop of the macroinvertebrate
population made up of Chironomidae, Ephemeroptera, Slmuliidae, and
Hydracarina.
McFarland and Peddicord (1980), and Peddicord (1980) studied the effects of
suspended kaolin on some marine and estuarlne macroinvertebrates in labora-
tory aquaria. Several species were shown to be relatively Insensitive to
suspended clay concentrations as high as 100 g/1. These species, which had
10 percent or less mortality during exposure times of 5 to 12 days, were:
3-5
-------
TABLE 3-1
Percent Increases in Number of Drifting Macroinvertebrates Caused by
Additions of Known Amounts of Suspended Sediment.
ADDED SOLIDS
(mg liter ±)
% INCREASE
IN NUMBERS DRIFTING
18.6
25.9
54.3
32.0
84.3
45.7
104.7
89.5
135.5
118.5
154.5
101.7
271.3
88.8
SOURCE: Gammon, in Rosenberg and Snow, 1975.
3-6
-------
sea urchin (Strongylocentrotus purpuratus), Japanese clam (Tapes japonica),
hermit crab (Pagurus hirsutiusculus), an isopod (Sphaeroma pentodon), mud
snail (Nassarius obsoletus), blue mussel (Mytilus edulis), and two species
of tunicates (Mogula manhattensis, Stye!a montereyensis) (Table 3-2).
Estimates for lethal concentrations of suspended kaolin for X percent of
the animals, commonly known as the LCX, were made for some of the estuarine
and marine species (McFarland and Peddicord, 1980). Time-concentration
studies showed the tunicate Ascidia ceratodes to be one of the most sensi-
tive species tested. The estimated 100-hour LCX values were: LC10 =
7 g/1, LC20 = 13 g/1, and LC50 = 38 g/1. Estimates of 200-hour LCX values
for those species tested longer than 200 hours are presented in Table 3-3.
Of those species whose responses are shown in Table 3-3, the tolerance of
the dungeness crab decreased the most rapidly with time. Further research
revealed that the mortality of dungeness crabs was associated with molting
(Peddicord, 1980). The 25-day LC50 for molting crabs was estimated as
9 g/1. After 25 days of exposure to 4 g/1, 20 percent of the crabs that
molted were expected to die (25-day LC20 = 4 g/1).
It is also important to recognize that sublethal responses to suspended
sediment may affect the organism's growth and metabolism. For example,
Sherk (in Rosenberg and Snow, 1975) reported that the pumping rates of
adult oysters were reduced by more than 50 percent in suspended sediment
concentrations of 0.1 g/1.
3.4 EFFECTS OF SUSPENDED SEDIMENT ON SALMONID FISH
The studies that are summarized in the following section deal primarily
with the effects of suspended sediment on the various life stages of the
salmonlds. The effects of suspended sediment on various life stages
encompassing the egg stage through the adult stage will be presented, and
will Include Information on several species. Salmonids generally migrate
to natal streams to spawn. For example, coho salmon (Oncorhynchus kisutch)
are anadromous fish, native to the northern Pacific Ocean. They migrate
from saltwater areas to natal streams to spawn from midsummer to winter,
depending on latitude. Entry into freshwater streams often coincides with
rises in streamflow (McMahon, 1983) and therefore often with high suspended
3-7
-------
TABLE 3-2
Observed Mortalities of Species Relatively Insensitive to suspended Kaolin.
Exposure time
ri Mortality
Species"
in days
at 100 g. L
Slrnni/\lot entrants piirptiraltts
9
0
(sea urchin)
Tapf> juiwnuu iJapanese claml
10
0
Pauurtn hi'rvmiusi ulus i hermit crab)
12
0
Sphtwnt/nu fientujoii (isopod)
12
0
.Vci.ssuriiis dhsu/ffiis (mud snail)
5
0
Wwi//n cdtitii iblue musseli i2.5 cmi
5
10
1/wi/im ctiuln iblue mussel) 110 cm)
II
10
WolmtUt »ianli(ith'n\i\ I tunicate I
12
9
Slvrla "ninlcrf\t'nsis (tunicate)
12
10
¦¦ Species grouped together were tested simultaneously in the same aquaria
'¦ Tested simultaneously in the same aquaria with Mvriltn t uhjurntuntii
SOURCE: McFarland and Peddicord, 1980.
TABLE 3-3
200-hr LCX Estimates, Equations, and Coefficients of Determination
for those Species Tested Longer than 200-hr.
Species
200-hr
LCX
in giL
Equations used
for estimates
Coefficient of
determination
r-
Vfvltlti.) (uhjorniunm "
LCI0 =
26
InY
=
22 3 - 3 59 InX
0 93
(coast mussel)
LC20 =
42
Y
=
lis - 0.349X
0.89
LC50 =
96
1 Y
=
0 020 - 1 93(1 X)
0 7J
Crimuoi: ntf/rnmat tiltiru
LCI0 =
16
InY
-
5.01 - 0.0113X
0 76
(spot tailed sand shrimp)
LC20 =
28
InY
=
5.04 - 0.00850X
0 87
LCJ0 =
.<0
InY
=
7% - 0.756 InX
0 98
Palaemun mat rodm t\ln\"
LCI0 =
24
InY
10.3 - 1.34 InX
0.71
(grass shrimp)
LC20 =
77
InY
=
4.94 - 0.00300X
0.%
LC50'
Cant er mounter
LC10 =
10
InY
=
6.37 - 0.766 InX
0 72
(dungeness crabi
LC20 =
18
InY
=
7.01 - 0.766 InX
0.%
LC50 =
32
InY
=
3 05 - 83.KI/X)
0.99
Seunthes succmea
LCIO =
9
Y
=
58.6 = 0.246X
0.88
(polychaetei
LC20 =
22
InY
=
4.51 - 0.00700X
0.92
LC50 =
48
InY
=
5.91 - 0.386 InX
0.91
Tested simultaneously in the same aquaria with 10-cm Mytilm ediihu
" Tested simultaneously in the same aquaria with Aniioi/ammariis cunfervu
-------
sediments. Older salmonids can survive high concentrations of suspended
sediment for considerable periods, and acute lethal effects generally occur
only if concentrations exceed 20,000 mg/1 (Sorensen, et al., 1977; Cordone
and Kelley, in Sigler, et al., 1984).
While direct and acute effects on fish are undeniably very important, the
effects of sedimentation and siltation of spawning grounds are also
critical for species propagation. Although the detrimental effects on eggs
at spawning grounds are widely known, quantities of sediment causing fish
to abandon redds are generally not documented.
Also important are those effects that may be categorized as sublethal, such
as turbidity effects on sight-feeding fish. Turbid water may obscure the
view of food, and thereby result in reduced growth rates for fish. The
studies and bioassays that are reviewed in the following section record the
direct effects of suspended sediment on fish, but may not reflect the
effects of sedimentation on reproduction. Using data from a literature
review by the European Inland Fisheries Advisory Coiranission (EIFAC, 1965),
Sorensen, et al. (1977) have summarized the effects of suspended sediment
on salmonld f1sh (Table 3-4). Effects on rainbow trout (Salmo gairdneri),
Pacific salmon (Oncorhynchus spp.), brown trout (Salmo trutta), cutthroat
trout (Salmo clarkii), Atlantic salmon (Salmo salar), and brook trout
(Salveilnus fontinalis) are Included.
3.4.1 EFFECTS ON EGG STAGE
Billard (1982) concluded that the presence of sediments in water does not
prevent fertilization of trout (Salmo gairdneri) eggs. Laboratory studies
were designed to expose eggs to sediment concentrations from 0 to 20 g/1
for 1, 10 or 20 minutes. The fertilization rate declined significantly
after the eggs were exposed for 10 minutes at 8°C to doses exceeding 1.2
g/1, probably because of clogging of the micropyle rather than the presence
of sediment in the medium in which the gametes meet.
3.4.2 EFFECTS ON LARVAL STAGE
Steel head (Salmo gairdneri, anadromous trout) fry were exposed to tur-
bidities of 38 to 49 NTU for 14 to 19 days (Sigler, et al., 1984). The
3-9
-------
TABLE 3-4
Summary of Effects of Suspended Solids on Salmonid Fish (Data taken from Review in EIFAC, 1965)
Pish
(Species)
Rainbow Trout
(Salmo gairdneri)
Pacific Salmon
(Oncorhynchus)
Ef feet
ConcentratIon
of Suspended
Solids
Source of
Suspended
Materials
Comment
Survived one day
80,000
ppm
Cravel washing
Killed in one day
160,000
ppm
Gravel washing
50% mortality in 3 1/2 wks
4,250
ppm
Cypsum
Killed in 20 days
1000-2500 ppm
Natural sediment
Caged in Powder River,
Washington
50% mortality in 16 wks
200
ppm
Spruce flbre
70% mortality in 30 wks
1/5 mortality in 37 days
1,000
ppm
Cellulose fibre
No deaths in 4 wks
553
ppin
Gypsum
No deaths in 9-10 wks
200
ppm
Coal washery waste
20% mortality in 2-6
90
ppm
Kaslln and diato-
Only slightly higher
months
maceous earth
mortality than control
No deaths in 8 months
100
ppm
Spruce fibre
No deaths in 8 months
50
ppm
Coal washery waste
No increased mortality
. 30
ppm
Kaslln or diato-
maceous earth
Reduced growth
50
ppm
Wood fibre
Reduced growth
50
ppm
Coal washery waste
Fair growth
200
ppm
Coal washery waste
"Fin-rot" disease
2 70
ppm
Diatomaceous earth
"Fin-rot" disease
200
ppm
Wood fibre
"Fin-rot" disease
100
ppm
Wood f ibre
Sytnptons after 8 months
exposure
No "fin-rot"
50
ppm
Wood fibre
Reduced egg survival
(Siltat ion)
F.Rgs in gravel
Total egg mortality
1000-2500 ppm
Mining operations
Powder River, Oregon
in 6 days
(Not specifically rain
bow trout eggs)
Survived 3-4 wks
300-7 50
ppin
Silt
Finger 1ings
(2 300-6500 ppm
for short
periods each
day)
-------
TABLE 3-4 (contd)
Summary of Effects of Suspended Solids on Salmonid Fish
Fish
(Spec les)
Brown Trout
(Salmo trutta)
Cutthroat Trout
(Salmo clarkii)
Atlantic Salmon
(Salmo salar)
Brook Trout
(SalvelInus fontl-
nalis)
Ef feet
ConcentratIon
of Suspended
Sol Ids
Source of
Suspended
Ma t e r i a I s
Reduced survivlal of eggs (Silting)
Supports populations (Heavy loads) Glacial silt
Avoid during migration
Do not dig redds
Reduced populations to
1/7 of clean streams
Abandon redds
Sought cover and stopped
feed ing
No effect on migration
No effect on movement
(Muddy water)
(Sediment in
gravel)
1000-6000 ppm China-clay waste
(If silt is
encountered)
35 ppm
Several thou-
sand ppm
(Turbidity)
Comment
Eggs in gravel
Spawn when silt is
washed from spawn-
ing hods.
Yuha River, California
Water must pass through
grave I
Two hours exposure
River Severn, British
lsl es
SOURCE: Sorensen, et al., 1977.
-------
turbidity, which was produced through the addition of fireclay and
bentonite to water in laboratory channels, caused the fish to exhibit
avoidance reactions. Although the turbidities examined were not lethal to
the fish fry, steel head in turbid-water channels were consistently smaller
than fish in clear-water channels.
Sigler, et al. (1984) compared the responses of coho salmon (Oncorhynchus
kisutch) fry in turbid-water channels (22-86 NTU) to responses of fry in
clear-water channels. The fish that were exposed to the suspended fireclay
and bentonite over an 11 to 15 day period were significantly smaller than
the control fish in clear-water channels.
3.4.3 EFFECTS ON JUVENILES
Juvenile coho salmon were subjected to elevated concentrations of suspended
sediment to test the threshold turbidity level that elicited avoidance
(Bisson and Bilby, 1982). The juveniles did not avoid moderate turbidity
increases, but exhibited significant avoidance when turbidity exceeded 70
NTU. Bisson and Bilby (1982) thought that the fish may have been avoiding
turbid water in order to maintain a view of potential food items, since
overall visibility and background contrast are key factors in food
selection for juvenile coho salmon.
Stober, et al. (1981) determined the 96-hour LC50 of volcanic ash for coho
smolts and presmolt coho. Results of the static bioassays showed 96-hour
LC50 values of 18,672 mg/1 and 28,184 mg/1 for presmolt coho and coho
smolts, respectively. Additional bioassays revealed 96-hour LC50 values
for coho smolts of 2,118 mg/1 and 29,580 mg/1 using bentonite and mudflow,
respectively.
The effects of sediment on the arctic grayling (Thymallus arcticus) have
been studied, mostly with regard to placer mining sediment effects.
Several studies which investigate the effects of placer mining sediments on
juvenile grayling are sumnarized below.
McLeay, et al. (1983) studied both lethal and sublethal effects of placer
mining sediment on grayling young of the year. Using recycle test tanks
3-12
-------
with a water temperature of 15°C, arctic grayling survived for 4 days in
250,000 mg/1 inorganic fines and for 16 days in 50,000 mg/1 Inorganic
fines. When the water temperature was decreased to 5°C, fish survived for
4 days in concentrations less than 10,000 mg/1. McLeay, et al. (1983)
observed a 10 percent mortality (over 4 days, 5°C) in sediment concen-
trations of 20,000 mg/1, and a 20 percent mortality in tanks containing
100,000 mg/1 sediment (4 day exposure, 5°C). The data suggest a decrease
in lethal tolerance for fish acclimated to colder water, which implies a
possible seasonal effect. Tests to determine 96-hour LC50 values (15°C)
revealed values more than 50,000 mg/1 for overburden and over 100,000 mg/1
for paydirt.
Sublethal effects studies showed no effect on gill histology after 4 days
exposure of grayling to 100,000 mg/1 or less (McLeay, et al., 1983).
However, stress tests showed Increased plasma glucose values In 24-hour
tests (15°C) using 50 mg/1 of overburden sediment. In contrast to the
results of gill histology studies by McLeay, et al. (1983), La Perrlere, et
al. (1983) reported that microscopic examination of gill tissue of young-
of-the-year grayling showed mucus secretions with embedded sediment
particles in as short as 12 hours when suspended solids were greater than
800 mg/1.
Simmons (1984) found that gill tissues of grayling appeared normal in
96-hour exposures to 170 mg/1 placer mining sediments. When the concen-
tration was increased to 1,205 mg/1, a moderate amount of gill damage was
observed.
3.4.5 EFFECTS ON ADULTS
Alexander and Hansen (1983) examined the effects of the addition of sand
(effective concentration of 80 ppm) on the brook trout (Salvelinus
fontinails) population of a small stream (Hunt Creek, Michigan). Adults,
as well as juveniles, were collected during the stream survey. The study
was conducted over a 5-year period, and showed the effects of sedimentation
as well as Increased suspended solids loading. Although the trout popula-
tion changed gradually, a 51 percent decrease in total number of trout was
observed over the 5 years.
3-13
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3.5 EFFECTS OF SUSPENDED SEDIMENT ON OTHER FISH
Non-salmonid species are affected by suspended sediment in the same ways
that salmonids are affected. The effects of suspended solids on primarily
freshwater species will be discussed first, and will be followed by a
discussion of the effects of suspended sediment on estuarine (and often
anadromous) species. Both lethal and sublethal effects will be discussed
together with the sediment concentrations (if known) that elicit the
response.
The spawning seasons of temperate, warmwater fish are generally definable
in timing and duration. The majority of warmwater riverine fish focus
their reproductive activities on brief intervals during the late spring and
early summer rainy season (Table 3-5). In the native state, turbid con-
ditions occur briefly during freshets and floods, and spring rains are a
stimulus for spawning. Altered watersheds have caused increases in river-
ine sediment loads during much of the year, and rivers carry especially
heavy silt loads during the spring rainy season.
Gammon (1n Sorensen, et'al., 1977) published a review of the effects of
suspended solids on f1sh. His review of material pertaining to non-
salmonid fish is summarized in Table 3-6. Muncy, et al. (1979) reviewed
the literature concerning the effects of suspended solids on the repro-
duction and early life of warmwater fish. The literature review resulted
in several lists which categorized f1sh as tolerant or intolerant of
suspended solids, and fish for which conflicting information was found.
These lists are reproduced 1n Appendix A.
3.5.1 EFFECTS ON FRESHWATER FISH
Effects on Egg and Larval Stages
Yellow perch (Perca flavescens) are frequently found in freshwater lakes
and rivers, but may also be found in estuarine salinities as high as
13 ppt. They are most common in clear water and numbers decrease with
increasing turbidity (Krieger, et al., 1983). Suspended sediment concen-
trations of 100 to 500 mg/1 reportedly delayed hatching of yellow perch
3-14
-------
TABLE 3-5
Patterns of Reproductive Timing and Movement Among Warmwater Fishes.
Family
Spawning Season
Duration of Season
Movement
Petromyzontldae
Late spring
Brief
Upstream to tributaries
Acipenseddae
Early to late spring
Brief
Upstream, orten extensive
Polyodonddae
Lata spring
Brief
To shoal areas within
large rivers
Leoisosteidae
Late spring
Brief
Inshore to weedy places
Ami 1dae
Late spring
Brief
Inshore to weedy places
Clupeidae
Late spring
Brief
Some anadrony
Hiodontidae
Late spring
Brief
Inshore?
Umbridae
Late spring
Brief
Limited movement to
streams, ponas, marshes
Esocidae
Early to late spring
Brief
Inshore to flooded areas
Cyprinidae
Primarily early to
late spring, some
in sunnier
Brief for most,
protracted for
some
Upstream among fluviatile
species, inshore move-
ment among others
Catostomidae
Early to late spring
Brief
Upstream in many
Ictaluridae
Late spring to summer
Usually brief, pro-
tracted for some
None or limited inshore
movement
Apnredooerldae
Early spring
Brief?
Not known
Percopsiaae
Late spring
Brief
Limited upstream or
Inshore movement
Cypr1nodont1dae
Late spring to summer,
pemaos year-around
1n some
Extended
Very limited. If any
Poec1l11dae
Most wanner months?
Extended
Very limited, if any
Atherinidae
Late spring & sumter
Probably brief
Not known
Gasterosteidae
Late spring & summer
Extended
None or very limited
Perc1chthy1dae
Late spring
Brief
Inshore, some anadromy
Centrarchidae
Late spring & sunrar
Brief to extended
Inshore
Perddae
Etheostomatlnae
Early to late spring
Brief
To shallow water
Perdnae
Early spring
Brief
To shallow water
Sclaenldae
Late spring to summer
Often lengthy
Not known
SOURCE: Muncy, et al., 1979
3-15
-------
TABLE 3-6
Effects of Suspended Solids on Non-Salmonid Fish (Data Collected from Gammon, 1970).
Fish
(Species)
Effect
Concentration
of Suspended
Solids
Source of
Suspended
Materials
Comment
Mixed fish popu-
lations
Decrease in occurence
Turbidity in-
crease
Mixed fish popu-
lations
Perch
(Perca flavesiens)
European Pike Perch
(Lucioperca lucio-
perca)
Zebra
(Brachyolanio rerior)
Barbel
(Barbus fluviatills)
European eel
(Anguilla angullla)
Smallmouth bass
(Micropterus dolo-
mieui)
Critical levels affect-
ing populations
High egg mortality
High egg mortality
Earlier egg hatch and
no Increase In egg
mortality
Decreased migration
Increased migration
Successful nesting,
spawning, hatching
100-300 ppm Industrial
(Silting)
England, Scotland,
and Wales fisheries
(Silting)
18,000-30,000 Limestone dust
ppm
(Increasing
turbidity)
(Increasing
turbidity)
(Sporadic
periods of
high turbidity)
Fry died within A
hours at 74,800
SOURCE: Sorensen, et al., 1977.
-------
eggs by 6 to 12 hours (Wang and Tatham, in Muncy, et al., 1979). Mortali-
ties of yellow perch larvae were significant at sediment concentrations of
500 mg/1 and 1,000 mg/1 (Auld and Schubel, in Muncy, et al., 1979).
Turbid water (250-2,350 JTU) caused a loss of orientation in smallmouth
bass fry. Larimore (in Muncy, et al., 1979) stated that losses of
smallmouth bass fry during floods could be caused by simultaneous rapid
changes in turbidity, light, velocity, and turbulence.
Effects on Juveniles
Heimstra, et al. (in Muncy, et al., 1979) reported that the movement
activity of juvenile largemouth bass was reduced in turbidities of 14-16
JTU for 30 days. Bass in turbid water also showed a high incidence of
"coughing," a reaction which helps fish cope with limited amounts of
sediment deposition on the gills.
Effects on Adults
The feeding rates of bluegill (Lepomis macrochirus) are decreased in turbid
water (Gardner, 1981). The fish were acclimated to the turbid water for 24
hours before being fed for a period of 3 minutes. The feeding rates of
bluegill were calculated for three turbidity levels (60, 120 and 190 NTU)
and 1n clear water (control). Fish in clear pools ate an average of 41
prey each in a 3-minute period, while f1sh in the highest turbidity ate 22
prey per fish. Bluegill feeding rates declined from about 14 prey per
minute in the control to 11, 10 and 7 per minute 1n pools of 60, 120, and
190 NTU, respectively. Vlnyard and O'Brien (in Muncy, et al., 1979) noted
that turbidities as low as 30 NTU reduce the reaction distances of bluegill
for all prey sizes.
Production of largemouth bass (Micropterus salmoides), bluegill (Lepomis
macrochirus), and redear sunfish (Lepomis microlophus) was lower in turbid
ponds than in clear ponds. Buck (In Rosenberg and Snow, 1975) found that
production 1n clear (less than 25 mg/1) ponds was 180.9 kg/ha, while pro-
duction 1n Intermediately turbid (25-100 mg/1) and turbid (more than 100
mg/1) waters averaged 105.3 kg/ha and 32.8 kg/ha.
3-17
-------
Wall en (in Sorensen, et al., 1977) tested the reactions of several warm-
water fish to turbidity. He found that most of the experimental fish
survived more than 100,000 ppm turbidity for a week or longer, but these
same fish died at turbidities of 175,000 to 225,000 ppm. Lethal tur-
bidities caused death in 15 minutes to 2 hours of exposure. Some effects
on selected fish used in Wall en's study are listed in Table 3-7.
3.5.2 EFFECTS ON ESTUARINE FISH
The reproductive cycles of many of the estuarine fish are such that they
migrate up freshwater streams to spawn during the late spring and early
summer. This is generally the period of high flow, which is accompanied by
increased turbidities and high sediment loads.
Several publications contain information about sediment effects on several
estuarine species. Muncy, et al. (1979) reviewed the literature pertaining
to the effects of suspended sediment on warmwater species, including those
estuarine species whose reproductive strategies are to spawn in freshwater
or nearly freshwater areas. O'Connor, et al. (1976, 1977) investigated
both lethal and sublethal responses of several estuarine species to sus-
pended solids, some of which will be included in the following section.
Effects on Egg Stage
Striped bass (Morone saxatilis) migrate to fresh or nearly freshwater to
spawn. Spawning may begin in mid-February in the southern portion of the
striped bass range, whereas in the extreme northern portions of the range,
spawning may not begin until June or July (Bain and Bain, 1982). Suspended
sol Ids concentrations of 100 to 500 mg/1 delayed hatching of striped bass
eggs by 4 to 6 hours (Wang and Tatham, in Muncy, et al., 1979). Morgan, et
al. (1983) reported significant developmental delays at sediment loads of
800 mg/1 or more, and concentrations of 2,000 mg/1 caused developmental
delays of 12 to 15 hours.
A suspended sediment concentration of 5,250 mg/1 delayed hatching of white
perch (Morone americana) eggs by 24 hours (Morgan, et al., 1983). Con-
centrations as low as 100 to 500 mg/1 caused a 4 to 6 hour delay (Wang and
Tatham, in Muncy, et al., 1979).
3-18
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TABLE 3-7
Some Effects of Turbidity on Selected Fish Species (Data from Wallen, 1951)
Species
Turbidity at First
Adverse Reaction
Turbidity at
First Death
Golden Shinner
(Notemigonus crysoleucas)
Mosquitofish
(Gambusia affins)
Goldfish
(Carassius auratus)
Carp
(Cyrinus carpio)
Red Shinner
(Notropis lutrensis)
Largemouth Black Bass
(Micropterus salmoides)
20-50,000 ppm
40,000
20,000
20,000
100,000
20,000
50-100,000 ppm
80-150,000
90-120,000
175-250,000
175-190,000
101,000 (average)
SOURCE: Sorensen, et a!., 1977.
3-19
-------
Effects on Larval Stage
Auld and Schubel (in Muncy, et al., 1979) reported significant mortalities
of striped bass larvae in suspended sediment concentrations of 500 mg/1 and
1,000 mg/1. Morgan, et al. (1983) determined a 24-hour LC50 of 20,417 mg/1
sediment, and a 96-hour LC50 of 6,292 mg/1 for larval striped bass. Fifty
percent of the white perch larvae reportedly survived sediment concentra-
tions of 67,000 mg/1 for 24 hours (24-hour LC50 = 67,000 mg/1), while the
48-hour LC50 was found to be 6,900 mg/1.
Effects on Juveniles and Adults
O'Connor, et al. (1976) tested the responses of several estuarine species
to various suspended sediment concentrations. Fish that were tested were
collected from the Patuxent River estuary, Maryland. The life stages of
the fish being exposed to the sediment concentrations were not specified
for many of the species tested. Thus, the results of these studies will be
presented as effects on juveniles and adults.
O'Connor, et al. (1976, 1977) studied the effects of suspended sediment on
spot (Leiostomus xanthurus), an estuarine-dependent species that lives 1n
the estuary during its juvenile period. Static bloassays yielded the
following 24-hour lethal concentrations for fuller's earth and natural
sediment (from the Patuxent River, Maryland):
Sediment LC (g/1)
LC10 LC50 LC90
Fuller's earth 13.08 20.34 31.62
Natural sediment 68.75 88.00 112.63
Increasing duration of exposure times caused an overall reduction of LC10,
LC50 and LC90. These values are shown in Table 3-8. Exposure to the sub-
lethal concentration of 1.27 g/1 fuller's earth for 5 days did not result
1n significant changes in the hematological parameters that were measured
(hematocrit, hemoglobin concentration, blood cell count).
3-20
-------
TABLE 3-8
LC10, LC50 AND LC90 Values for Spot,
With Increasing Duration of Exposure to Fuller's Earth
Duration of
Bioassay (h) LC10 LC50 LC90
12 27.56 42.36 65.12
18 21.07 33.06 51.87
20 a
24 13.08 20.34 31.62
48 1.13 1.90 3.17
aNot tested.
SOURCE: O'Connor, et al., 1976.
276/5
3-21
-------
White perch exposed to fuller's earth for various times showed a reduction
of LC10, LC50 and LC90, with increasing duration (Table 3-9). Lethal con-
centrations of fuller's earth and natural sediments were determined for
24-hour exposures (O'Connor, et al., 1976). The results were:
Sediment LC (g/1)
LC10 LC50 LC90
Fuller's earth 3.05 9.85 31.81
Natural sediment 9.97 19.80 39.40
Particle size and shape probably caused the variation in the lethal effect
to species (O'Connor, et al., 1976). The influence of particle size has
been discussed previously in the Introduction to this chapter.
O'Connor, et al. (1977) studied the sublethal effects of suspended sediment
on white perch. Adult fish were exposed to 0.65 g/1 fuller's earth for 5
days. Fish exposed to sublethal concentrations of suspended solids showed
the same hematological responses as fish deprived of sufficient oxygen.
White perch showed significant increases in red blood cell count, hemo-
globin concentration and microhematocrit. Examination of the gill tissues
of exposed white perch revealed many mucus cells on the gills and swelling
of the secondary lamellae.
Several other estuarine species were tested in bioassays using fuller's
earth. The results of these tests, which determined lethal concentrations,
are summarized in Tables 3-10 and 3-11. Both menhaden and blueflsh
exhibited 100 percent mortality at relatively low concentrations (1.2 g/1
and 0.8 g/1, respectively) of fuller's earth (Table 3-10). The LC10, LC50,
and LC90 for fuller's earth were calculated for bay anchovy, Atlantic
silverslde, mumrnichog and striped kilUfish (Table 3-11). Of these fish,
the bay anchovy and Atlantic silverside were the most sensitive to
suspended fuller's earth.
3-22
-------
TABLE 3-9
LC10, LC50 and LC90 Values for White Perch,
with Increasing Duration of Exposure to Fuller's Earth
Duration of
Bioassay (h) LC10 LC50 LC90
12
32.07
41.00
52.41
18
a
20
7.91
14.99
28.38
24
3.05
9.85
31.81
48
0.67
2.96
13.06
aNot tested.
SOURCE: O'Connor, et al., 1976.
276/4
3-23
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TABLE 3-10
Lowest Fuller's Earth Concentration Causing 100-Percent
Mortality in a 24-Hour Exposure
for Five Estuarine Fish
Species
Age
Individuals
Test Conditions
Class
(No.)
Salinity
(ppt)
Temp.
(°C)
Concentration
fuller's earth (g/1)
Menhaden
0+
30
5.5
25-2
1.2
Menhaden
1+
60
23.6
22-2
0.8
B1 uefi sh
1+
26
20.0
22-2
0.8
Weakfish
0+
47
20.0
22-2
6.8
Weakflsh
0+
20
5.5
25^2
8.2
Striped Bass
2+
31
5.5
25^2
16.6
Croaker
1+
17
5.5
25-2
11.4
SOURCE: O'Connor, et al., 1976
276/6
3-24
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TABLE 3-11
LC10, LC50, AND LC90 Values Determined
for 24-Hour Exposure of Estuarine Fish
Species
Lethal
Concentration (g/1
fuller's earth)
LC10
LC50
LC90
Bay anchovy
2.31
4.71
9.60
Atlantic silverside
0.57
2.40
10.00
Mummichog
24.47
39.00
62.17
Striped killifish
23.77
38.18
61.36
SOURCE: O'Connor, et al., 1976
276/7
3-25
-------
O'Connor, et al. (1976) classified several estuarine fish species according
to their toleration of suspended solids. The groups were:
1. Class I: Suspension-Tolerant Species. The concentration of
fuller's earth required to attain the 24-hour LC10 value is equal
to or in excess of 10 g/1. Tolerant species were the murranichog,
striped killifish, and spot.
2. Class II: Suspension-Sensitive Species. LC10 values for 24-hour
exposure to fuller's earth were between 1 and 10 g/1. The sensi-
tive species were white perch, bay anchovy, juvenile menhaden,
striped bass, croaker, and weakfish.
3. Class III: Highly Sensitive Species. Twenty-four-hour LC10
values were less than or equal to 1 g/1 of fuller's earth. Highly
sensitive species were Atlantic silverside (24-hour LC10 value
0.57 g/1), juvenile bluefish, juvenile menhaden and young of the
year white perch. Juvenile bluefish and juvenile menhaden failed
to survive in concentrations of 0.8 g/1 for more than 18 hours.
Young-of-the-year white perch suffered 100 percent mortality in
0.75 g/1 fuller's earth in 20 hours.
3-26
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4.0 A FRAMEWORK FOR SUSPENDED SEDIMENT CRITERIA
TO PROTECT AQUATIC LIFE
4.1 INTRODUCTION
As shown in Chapter 2, cultural, geologic and meteorologic factors
influence suspended sediment concentrations in a water body. A cause and
effect interplay exists between geology, climate, and hydrology, which
influence topography, soil cover, and land use. Regions of similar geology
exposed to similar climate and meteorology for equal amounts of time will
display similar patterns of hydrologic response and sedimentation.
Aquatic life cycles may be related to temperature and hydrologic condi-
tions. A national single level criterion for suspended solids may not be
appropriate due to regional and seasonal variations in aquatic life and in
naturally occuring sedimentation processes. Regional and seasonal criteria
should be considered that are based on a consistent methodology and unit of
measure. Incorporation of region and season into criteria ultimately will
require a detailed understanding of hydrology, of how the normal life cycle
of the resident biota proceeds in concert with hydrologic phenomena, and of
how the 'toxicity' expressed by suspended sediment is governed by hydro-
logic phenomena.
The concept of identifying hydrologlcally similar basins based on relation-
ships between landform characteristics and the controlling factors of
climate, geology, and vegetation is not novel. Quantitative geomorphology
was revolutionized 1n 1945 when Horton (1945) introduced his system of
stream ordering and laws of drainage composition. Horton's work was
supplemented by Langbeln (1947), Strahler (1957), Smart (1972) and others.
Important considerations in defining regions for suspended sediment
criteria should include (1) physiographic province; (2) annual rainfall
distribution; (3) climate; (4) watershed boundaries as indicators of hydro-
loglcally controlled ecosystems; and (5) political jurisdictions in which a
suspended solids criteria is implemented and enforced. The following
sections present possible approaches for regional and seasonal delineation.
4-1
-------
4.2 REGIONAL BASES FOR CRITERIA
4.2.1 APPROACHES
Several approaches to regionalization are discussed below. These
approaches include physiographic province, principal drainage basin, land
resources, climate and hydrology, ecoregion, and political jurisdiction.
4.2.2 REGIONALIZATION BY PHYSIOGRAPHIC PROVINCE
The identification of regions- by physiography is based on physical
description and geologic characteristics. Advantages include the ability
to address isolated areas of geomorphic similarity for sedimentation and
the ability to distinguish aquatic life habitats, as in coastal plain
versus Piedmont variations. Disadvantages are mainly due to the degree or
number of physiographic regions to establish and the lack of precision in
defining regional boundaries. An example of a general classification by
broad physiography is shown 1n Figure 4-1. A more distinct classification
is shown 1n Figure 4-2.
4.2.3 REGIONALIZATION BY PRINCIPAL DRAINAGE BASIN
Regionalization by principal drainage basin allows delineation of isolated
ecosystems. Contributing sources of runoff and pollution from tributaries
can be easily monitored and controlled. Watershed management can be
applied for optimum multi-purpose water resources planning. Disadvantages
result from physiographic variance within major drainage basins. Figure
4-3 illustrates an example of regionalization by major drainage basin.
The Office of Water Data Coordination (OWDC) was established within the
U.S. Geological Survey to coordinate water data acquisition and distribu-
tion after the United States Bureau of the Budget Circular A-67 was Issued
1n 1964 (U.S. Geological Survey, 1970). OWDC divided the conterminous
United States Into 79 principal geographic units (Figure 4-4). The units,
divided by drainage basin, can be used to provide a basis for regional-
ization 1n establishing suspended solids criteria that can be Integrated
with the national network of data acquisition.
4-2
-------
Pacific Northwest
Sierra Nevada
Great Basin
Rocky Mountains
Great Plains
Central Plains
Appalachian Mountains
Gulf/Atlantic Coastal Plain
Figure 4-1. Physiographic Regions, Case 1
-------
-p=»
I
4^
Hi^Dakota-Minnttoia Drift
anH 1 / r"
Hora
ofiSS! .
rpvJ^M^'orado n
} \ Pl<"eaui
a°d Rang^_Aj
Principal Island} oi
HAWAII
PHYSICAL SUBDIVISIONS
£dwm H Hammond
1%5
Albtn Iqu4l Aim CrO|«vlion
SCA41 I 17 000 000
ALASKA PHYSICAL DIVISIONS
Figure 4-2. Physiographic Regions - Case 2
(Source: Miller et al., 1962)
-------
See teit for key to drtinege besin numbers
&im Map Compiled end Drawn by
WATER INFORMATION CENTER Inc.
Source. U.S. Cotsi end Geodetic Survey
Aeroneulict! Planning Chert AP-t
Figure 4-3. Regionalization by Principal Drainage Basin
(Source: Miller et al., 1962)
-------
U S GEOLOGICAL SURVEY
OFFICE OF WATER DATA COORDINATION
••iu s INDEX MAP OF DRAINAGE AREAS
Figure 4-4. Office of Water
(Source: USGS,
Data Coordination, Map of Drainage Basins
1970)
-------
4.2.4 REGIONALIZATION BY LAND RESOURCES
The Soil Conservation Service (SCS) of the U.S. Department of Agriculture
(USDA) produced an atlas containing 20 land resources regions encompassing
broad patterns of soils, climate, natural vegetation, water resources,
topography, and land use (Soil Conservation Service, 1963). The emphasis
for establishing the regions was based on combinations and intensities of
problems in soil and water conservation. The distribution of the regions
is given in Figure 4-5 and descriptions of each can be found in Appendix B.
4.2.5 REGIONALIZATION BY CLIMATE AND HYDROLOGY
Difficulties exist in trying to establish regionalization based on climate
and hydrology due to the dynamic nature of each. The Water Atlas of the
United States (Miller et al., 1962), Climatic Atlas of the United States
(Environmental Science Services Adminstration, 1968), and Technical Paper
40 (Weather Bureau, 1963). provide national distributions of climatic data
including precipitation, normal daily temperatures, evaporation, sunshine,
solar radiation, and wind characteristics. Average daily and annual values
of these records can be used as a guide for establishing regions based on
climate. Characteristics that can be used as guidelines Include average
precipitation (Figure 4-6), runoff (Figure 4-7), number of days with
thunderstorms (Figure 4-8), and seasonal patterns of runoff which can be
used as a basis for seasonal Identification as discussed in the following
section.
4.2.6 AQUATIC EC0REGI0NS
Studies conducted at the EPA Environmental Research Laboratory in
Corvallls, Oregon, have focused on the 'aquatic ecoreglon,' in which least
disturbed streams provide examples of the best chemical, physical, and
biological conditions that can be expected in a given ecoregion. An
aquatic ecoreglon is defined primarily on the basis of topography, soil
type, vegetation, and land use.
Water quality objectives for background and uncontrollable anthropogenic
suspended sediment, based on these studies, would provide some controls on
settled sediment as well. Where appropriate, these studies might provide a
4-7
-------
-------
Figure 4-6.
Average Annual Precipitation for Conterminous U.S.
(Source: Miller et al., 1962)
-------
-Pk
I
I—»
o
tar lar its* «' «r ¦' mr
Figure 4-7. Average Annual Runoff for Conterminous U.S.
(Source: Miller et al., 1962)
-------
!»• | jo* !!»• HO* 106' 100- *>' «¦' »* »" n• to' f
Fi gure
4-8.
Average Annual Number of Days With Thunderstorms,
for Conterminous M'.S. (Source: Miller et al., 1962)
-------
good starting point for the establishment of criteria for suspended sedi-
ment, although criteria suggested by the studies may be overly stringent
(from the standpoint of protection of aquatic life) and overly difficult to
attain.
4.2.7 POLITICAL BOUNDARIES
National water quality criteria are essentially recommendations, and are
not enforceable by law. Enforcement comes into being when criteria are
incorporated into a state standard. Each of the bases for regionalization
discussed above ignores political boundaries and, as a practical matter,
may not adequately address the water body that crosses state lines. Given
that the statutes of adjacent states may not incorporate the same uses or
standards for conventional and toxic pollutants in a common water body, it
is likely that differences in approach will maintain for a suspended
sediment standard as well. Although regionalization within a state should
be encouraged, using one of the bases discussed above, it is inevitable
that state boundaries will be a factor in the development of suspended
sediment criteria.
4.3 COMBINING BIOLOGY AND STATISTICAL HYDROLOGY
4.3.1 INTRODUCTION
As seen in Chapter 3, complex cause and effect relationships exist between
concentration of suspended sediment and impact on specific life stages of
specific forms of aquatic life. The attention given sediment effects on
aquatic life has been small compared with the effects of toxic chemicals on
aquatic life and, as a consequence, the database on sediment effects is
sparse. Size of the database notwithstanding, we do know that the response
of aquatic life to suspended sediment is rather complex.
Previous studies of ammonia (Wu, et al., 1982), copper (Brown and Wang,
1984), and cadmium (Wang and Carter, 1984) have shown that both the
concentration of exposure, and the duration of exposure, are Important to
the ability of aquatic life to withstand toxic pollutants. The information
in Chapter 3 suggests that the same is true for suspended sediment. In the
remainder of Chapter 4, we will discuss, on a hypothetical basis, the tie
4-12
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between hydrologic events and the duration-concentration response of
aquatic life, and combine the two phenomena into a procedure for the
establishment of criteria for suspended sediment. Since sediment levels in
a stream are strongly related to seasonal rainfall and streamflow (Chapter
1), hydrology provides a good starting point for the formulation of
criteria.
4.3.2 SEASONAL GENERATION OF SUSPENDED SEDIMENT
Because rainfall and streamflow follow seasonal patterns, suspended
sediment concentrations in a stream follow seasonal patterns. The fact of
seasonality argues strongly for seasonal criteria.
One approach to establishing criteria within regions is by calendar season.
A disadvantage to the calendar definition is that hydrologic seasons and
stages in the life cycle do not necessarily coincide with calendar seasons.
Seasons might better be defined as portions of the water year (October
through September), where distinctions such as rainy season and dry season
would be more conducive to analysis than an analysis by calendar season.
Seasons based on trends in the water year could be region or even site
specific and would present a logical framework for blending hydrology and
toxicity into water quality criteria for suspended sediment.
Defining criteria by month would provide even finer resolution to accom-
modate temporal variations in hydrology and life cycle. However, the
existing database on biological effects 1s not large enough to support this
degree of refinement, and the specification of monthly criteria would prove
to be complex, cumbersome, unwieldy, and unnecessary.
4.3.3 HYDROLOGY
Since rainfall and runoff are the dynamic governing agents 1n the produc-
tion of sediment and high suspended solids concentrations, 1t is logical to
base criteria on seasonal patterns of runoff. Figures 4-9, 4-10, and 4-11
illustrate temporal variations in runoff across the country.
The type of information presented in Figure 4-9 is generated at numerous
river gages maintained by various state agencies and by the U.S. Geological
4-13
-------
-F*
l
Figure 4-9. Distribution of Runoff, by Region and by Season
(Source: Miller et al ., 1962)
-------
•4^
I—•
cn
Figure 4-10. Seasons of Lowest Flows
(Source: Miller et al., 1962)
-------
I
~—*
cr>
Figure 4-11. Seasons of Highest Flows
(Source: Miller et al., 1962)
-------
Survey (US6S). Streamflow may be translated into a suspended sediment
loading by various means (sediment rating curves, site-specific or regional
empirical relationships; or by direct measurement at a few USGS stations),
so for the remainder of this discussion we will use streamflow as a
surrogate for suspended solids concentration.
The daily stream gage data used to develop Figure 4-9 may be reformatted to
develop the flow-duration curve for a given gage. The flow-duration curve
(Figure 4-12) shows the proportion of days during a period of record that a
given level of flow is recorded, and may be used to show the cumulative
time over which a given flow (or sediment level) is exceeded. While such a
curve will suggest frequency of violation that might be expected once a
criterion is set, it will not be particularly helpful in actually setting
criteria because it depicts cumulative events of a given duration rather
than the duration of individual events.
4.3.4 TIME-CONCENTRATION TOXICITY RELATIONSHIPS
The 'toxicity' of suspended solids to aquatic life is discussed in Chapter
3. The information in Chapter 3 was selected to illustrate the fact that
the effect evoked by exposure to a given pollutant depends upon the length
of exposure, and also upon the life stage of a particular organism. The
duration of exposure is significant with toxic chemicals as well. Although
there are substantial data bases available to document the toxicity of
chemical pollutants, the data base descriptive of the. effects of suspended
sol Ids on the biota is very sparse. The duration of exposure information
of Chapter 3 points out a fallacy to basing criteria on a single number,
such as a 96-hour LC50, and illustrates the need to consider the importance
of duration of exposure, species, and life cycle stage as well.
A hypothetical study of a given suspended material and a given f1sh might
generate a plot such as Figure 4-13. The figure shows that a given effect
is seen after a 40-day exposure to 1.0 units of sediment, or to a 12-day
exposure to 2.0 units. The specific design of experiments needed to
generate such a curve is properly the domain of the toxicologist and is
beyond the scope of this report. Regardless, it 1s important to note that
a single value criterion, such as a 96-hour LC50 (which in Figure 4-13
4-17
-------
z
o
5.0
4.0
3.0
2.0
1.0
0.0
TYPICAL SPRING
CONDITIONS
TYPICAL SUMMER
CONDITIONS
0 20 40 60 80 100
PER CENT OF TIME CONCENTRATION IS EXCEEDED
Figure 4-12. Typical Flow-Duration Curve
4-18
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5.0
4.0
3.0
2.0
REGION OF ADVERSE EFFECTS
1.0
REGION OF NO EFFECT
0.0
10 20 30
DAYS OF CONTINUOUS EXPOSURE
40
Figure 4-13,
Hypothetical Concentration-Duration Plot of Adverse
Effects Response for Exposure of a Fish to
Suspended Solids.
4-19
-------
corresponds to a concentration of 4.0 units), may not be sufficient because
it does not adequately protect against longer periods of exposure, and may
overprotect during short periods of exposure.
Figure 4-13 also suggests that a fish may be able to withstand a heavy
exposure for a short period of time, without effect. The 'no' effect'
region is important in two ways: first, it suggests that a single extreme
rainfall event, an outlier, with its resultant heavy suspended sediment
load, may not be of consequence to a given fish, and that isolated extreme
events may be of little importance in setting criteria. Second, it
provides a tie to Figure 4-12, the flow duration curve. If the
concentration-duration curve shows no effect for a 12-day exposure to 2
units, and the flow-duration curve suggests that this period of exposure
will not occur, then one type of conclusion may be drawn. If on the other
hand the concentration-duration relationship shows there will be a problem
with a 1 unit exposure for 30 days, and the flow-duration curve shows that
this combination is likely to occur, decisions will have to be made as to
what level of protection to incorporate into a criterion, and/or what might
be done to reduce the sediment load.
The question of what might be done to control sediment is important. Most
sediment in a river is derived from nonpoint sources, or from the resus-
pension of bottom sediment. To the extent that suspended sediment is
attributable to point sources, urban runoff, poor agricultural land man-
agement, or activities such as logging, construction, or placer mining,
controls may be feasible. Otherwise, the sediment in a river is a back-
ground presence which may fluctuate with hydrologic events, but which is
beyond easy means of control.
For those cases where there are natural and anthropogenic, point and
nonpoint, sources of sediment, it may be fruitful to look beyond the flow-
duration curve in order to distinguish natural from controllable sources.
In the course of developing the flow-duration curve, resolution is lost and
it is not possible to distinguish how long a particular concentration
persists. One can only say that a given concentration occurred for a
certain portion of the year.
4-20
-------
One way to obtain better resolution is to take the daily flow (sediment
concentration) record (Figure 4-14) and analyze this for various flow
windows, or periods of time, over which a given concentration persists.
Using the hypothetical example of Figure 4-14 to illustrate, for a con-
centration of 2 we have one 90-day exceedance, and two 10-day «xceedances.
For a concentration of 3, we have one 20-day, one 10-day, and one 5-day
exceedance. Continued evaluation would permit construction of the type of
plot presented in Figure 4-15, from which one 1s able to tell how many
times a given concentration and a given duration of sediment occurred in
the water body.
Combining Figure 4-13 and Figure 4-15 (Figure 4-16) provides a means for
the decisionmaker to relate toxicity data to hydrologic data. The upper
portion of Figure 4-16 enables an assessment of risk attached to a given
concentration, or period of exposure. For example, the figure shows that
fish can withstand a 12-day exposure to a concentration of 2 units, and a
concentration of 2 units is likely to be equalled or exceeded about 10
times. Translation of number of exceedances to percent of total record
provides an estimate of risk. For example, if this were a 20-year period
of record, there is a likelihood of 0.5 events per year where the con-
centration of 2 units or greater will be violated over a 12-day period.
Figure 4-16 also shows, for a 12-day period of exposure, that a concen-
tration of 1.0 will be exceeded 16 times, and a concentration of 3.0 will
be exceeded 6 times. A concentration between 1.0 and 2.0 lasting 12 days
will occur 4 times, but this 1s of no concern since a concentration less
than 2.0 will evoke no adverse effects. In contrast, a concentration
greater than 2.0 will evoke adverse effects, and a 12-day concentration
between 2.0 and 3.0 may be expected to occur 6 times for the period of
record. The significance of this Incursion Into the region of adverse
effects depends upon such factors as the severity of the adverse effect,
the time of year when these Incursions are likely to occur, and the most
sensitive stage of the life cycle that will be found for a given species
when these Incursions occur.
4-21
-------
5.0
i
ro
ro
Z
o
t-
<
£E
4.0
Hi
O
z
o
o
CO
9
_i
o
CO
o
Ui
Q
z
UJ
a.
(0
3
CO
3.0
2.0
1.0
0.0
X
X
.1.
X
X
X
X
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
I
N-20
N
TIME, days
Figure 4-14.
Hypothetical
Daily Record for Suspended Solids
-------
DURATION OF SPECIFIED CONCENTRATION, days
Number of Times a Given Concentration is Exceeded
for a Given Number of Days
4-23
-------
5.0
4.0
3.0
2.0
1.0
0.0
Ci < c2 < c3
REGION OF ADVERSE EFFECTS
REGION OF NO EFFECT
_L
10 20 30
DAYS OF CONTINUOUS EXPOSURE
40
Figure 4-16.
Relationship of Suspended Solids Adverse Effect Level
to Likelihood of Occurrence of a Given Suspended
Solids Concentration
4-24
-------
A water quality criterion for suspended sediment cannot be specified
without first defining what adverse effects are to be guarded against, and
for what types of organisms and life stages (so as to develop the equiva-
lent of Figure 4-13); and without first quantifying what the natural and/or
background levels of sediment will be on a seasonal and a site-specific
basis (since it would make no sense to specify a criterion that would
automatically be violated by background conditions). It may be difficult
to distinguish controllable anthropogenic loadings from background sources,
particularly so when the anthropogenic loading is small compared to the
background loading.
Since background concentrations will vary with hydrologic events, and since
the susceptibility to sediment varies with stage of the life cycle, it will
be necessary to specify seasonal criteria. Criteria will be most important
during average and during low flow periods when background levels are low
compared to anthropogenic contributions. High flow periods, many of which
might be considered to be outliers, extreme storm events, do not really
fall within the realm of criteria since the major natural sources of sedi-
ment (erosion and channel scour) during these periods cannot be controlled,
and controls on anthropogenic sources may not be adequate.
There are many statistical tests that might be used to identify outliers.
One possible test is found in the lognormal distribution. The flow in a
river tends to follow a lognormal probability distribution. Since sediment
levels are directly related to flow, we can also assume that sediment
levels are lognormally distributed. Specifying a probability level for
flows that are abnormally high provides a means for Identifying flows in
the historical record that represent extreme events during which sediment
levels cannot be controlled.
4.4 ADDITIONAL FACTORS THAT MUST BE CONSIDERED
The preceding section outlined how a statistical analysis of hydrology (and
sediment loadings, by association) could be combined with toxicity data as
an approach to specifying criteria for suspended solids. This discussion
is elementary, and does not address a number of problems and questions that
4-25
-------
must be considered in the development of criteria. Some of these questions
are Introduced below.
1. Adequacy of data base. A great deal of material is available in
the literature which is descriptive of the effects of suspended and
settled sediment on the biota of a stream. However, very little of
this includes enough detail to permit establishment of criteria.
If a procedure were to be used that Is analogous to the development
of criteria for toxic chemicals, a much more substantial database
on sediment effects would be required.
2. Definition of adverse effects. There are many adverse effects to
the biota of a stream that can be attributed to suspended sediment.
These may range from Inconvenience to sight feeding fish, to
lethality because of clogging of the gills. The fact that fish
persist in natural streams that carry an occasionally heavy sedi-
ment load suggests that lethality may not be a problem. Where
possible, fish may simply go elsewhere, and return when sediment
concentrations return to manageable levels. This also raises the
question of the need to distinguish between suspended sediment, and
settled sediment. How do we address the fact that suspended
sediment may not be a problem for a given fish, but may become a
problem when velocities decline and solids settle out to smother
breeding grounds, or eggs, or macroinvertebrates? How do we
address the fact that many fish and macroinvertebrates thrive when
the bottom Is covered by fine sediments?
3. Definition of sediment. The quality of a suspended sediment is
determined by such factors as particle size, mineral content, and
organic content. Particle size may vary with water velocity, and
will vary with physiographic region. To the extent that sediment
may have a direct physical effect on the biota, a consideration of
particle size is important. Particle size can be handled statis-
tically, and could be related to flow, and to duration of exposure
to various concentrations of suspended sediment. Toxic chemicals
may be sorbed to sediment particles, and may be tied up and
4-26
-------
rendered toxicologically inert. The extent to which toxics are
inactivated may depend upon the organic or the mineral content of
the sediment, and will differ from toxic chemical to toxic chemi-
cal. The question should be considered as to whether sediment
quality is important to the establishment of criteria, or whether
all sediments can be treated alike.
4-27
-------
5.0 CONCLUSIONS AND RECOMMENDATIONS
5.1 CONCLUSIONS
The previous chapters address the causes and impacts of suspended solids on
water quality. The following conclusions may be drawn:
o Suspended solids concentrations vary spatially and temporally due to
the complex cause and effect relationship between geology, topog-
raphy, climate, land cover, and runoff.
o The habitat preferences and life cycles of aquatic life may be
correlated with geology, topography, climate, and runoff.
o Suspended sediment affects different species of aquatic life
differently.
o The complexities of sedimentation Illustrate that a single national
criteria may not be appropriate.
o Regional correlations exist between the processes resulting in
sedimentation and species behavior that can be used as a basis for
criteria.
o Regional/seasonal relationships appear to be the most feasible
approach for setting natural condition hydrologic criteria.
5.2 METHODOLOGY RECOMMENDATION
The following elements are recommended in establishing suspended solids
criteria:
1. Identification of regions. SCS land resource units (Soil
Conservation Service, 1963) are recoranended as the basis for
spatial regional1zat1on. SCS land resource units are based on
climate, soils, topography, natural vegetation, water resources,
and land use--all factors involved in sedimentation.
2. Identification of seasons. Hydrologic seasons within each region
are recommended based on annual precipitation distributions.
3. Development of flow/sediment rating curves for rivers, lakes, and
estuaries. Statistical analyses must be performed on gaged sites
to develop flow-duration frequency curves. Rating curves relating
flow, sediment, and drainage area within seasons within regions in
natural drainage basins can be developed. Duration and frequency
for criteria will be based on species tolerance analysis. Long
term levels will reflect long term seasonal averages omitting
single event short duration large sediment loads. Short term
levels will consider single event conditions.
5-1
-------
4. Identification of short and long term tolerances of species or
families to suspended solids. Definition of short and long term
must be defined.
5.3 FUTURE WORK
Each of the four elements listed above under Methodology will require
individual attention. Elements 1, 2, and 3 are based on a detailed
analysis of the historical record of stream flow and sediment loading
patterns, soil types, and general physiography. From this, definitions can
be developed of regions, and of seasons within these regions, and specific
sediment load and duration relationships can be characterized.
Element number 4 may be approached in stages. In the first stage a
concerted effort should be made to search the literature for data that
would augment the time-concentration information presented in Chapter 3.
This would enable a first pass at the development of time-concentration
curves such as Figure 14-3, that could then be correlated with hydrologic
data, as an approach to sediment criteria (Figure 4-16). While this is
being done, attention must also be given to development of a methodology by
which time-concentration curves for a number of species or families or
individual fish, could be combined to produce a curve that is representa-
tive of all aquatic life.
The development of time-concentration relationships based on existing
information is an important first step, however, it is not likely that
sufficient data will be found to address element 4 adequately, and it will
be necessary to design and conduct bioassay tests that will enable a clear
understanding of the several factors—type of sediment, types of test
organism, water quality parameters, intensity and duration of exposure,
etc.—that are Important to the development of sediment criteria.
5-2
-------
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6-1
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6-8
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APPENDIX A
TOLERANCES OF FISH TO SUSPENDED
SOLIDS (TURBIDITY) AND SEDIMENT
SOURCE: Muncy, et al., 1979
-------
TABLE A-l
Warmwater Fishes which
and Sediment. Numbers
are Intolerant of Suspended Solids (Turbidity)
refer to references listed in Table A-4.
Species
Effect
Impact
through
Spawning General
Suspended solids
Sediment
Irhchvomyzon
castaneus
7
7
Acioenser
fulvescens
7 2!,29
7,27,29
Polvodon soachula
21 29
21,29
Lepisosceus
placoscomus
27
27
Amia calva 25
,30
25, 30
Hiodon tereisus
2-7,29
27, 29
Escx lucius 2k
,28.30
30
24,28 ,30
Esox raasauinoncv
L7 ,30
27. 30
Clinostosius
elor.zacus
8,30
8,30
Dicnda nufcila
29
29
Excelossum laurae
27.30
27 ,30
Exoeicssus
maxiliinzua
25
25
Hybopsis amblers
29,30
29
29,30
Hvbcosis dissimilis
27 ,30
27 ,30
Hvboosis x-ounccaca
8,27 ,30
8,27 ,30
Nocccis bieuctacus
7
7
Noccnis ricroDoeon
27 ,30
27, 30
27 ,30
Nocroois amis
5
5
Nocropis boops
29,30
29, 30
29,30
Nocroois comunus
7
7
Nocroois ecilias
27 ,29,30
27 , 29, 30
27 , 29 , 30
Nocropis hecerodon
8,13,30
8, 13, 30
8,13,30
Nocroois heceroleois
7,30
7, 30
Nocroois hudsonius
8,30
30
8
Nocropis rubellus
2,30
2, 30
30
Nocroois scramineus
7,8,30
7, 30
7,8
Nocropis cexanus
29
29
Nocropis copeka
8
8
A-l
-------
TABLE A-l
Warmwater Fishes which are Intolerant of Suspended Solids (Turbidity)
and Sediment. Numbers refer to references listed in Table A-4.
Species Effect Impact through
Spawning
General
Suspended solids
Sedioe
Notroois volucellus
30
30
Carpiodes velifar
29
29
Cycleptus elongatus
7,29
7,29
Erimyzon oblongus
30
30
Erimyzon aucetta
27,30
27, 30
27,30
Hypentelium nigricans
7,8,25,30
25, 30
7,25,]
Lagochila lacera
30
30
30
Minytrema oelanops
7,30
7, 30
Moxostoma carinatua
30
30
30
Moxostoma duquesnei
8,25,30
8, 30
8,25
Moxostoma valenciennesi
8,27.30
8, 27, 30
27,30
Ictalurus furcacus
5,7,30
5, 30
7,30
Noturus flavus
8
8
Noturns furiosus
30
30
Noturus gy-rinus
25,30
30
25,30
Nocurus miurus
7,25
7, 25
Noturus eraucmani
27
27
27
Pylodicri. s olivaris
30
30
30
Percoosis
omiscomayais
30
30
Fundulus notatus
30
30
Labidesches sicculus
30
30
Culaea inconstans
30
30
Aabloplites rupescris
29 .
29
Lepomis gibbosus
9,25,30
9, 25, 30
9
Lepomis megalotis
29,30
29, 30
Micropterus dolomieui 23,30
23,30
23, 30
23,30
Micropterus salaoides
23,30
23, 30
23,30
Ansmocrypta asprella
29,30
29,30
Anmocrypta clara
29
29
Amnocrvpta pellucida
27 .30
27 .30
A-2
-------
TABLE A-l
Warmwater Fishes which are Intolerant of Suspended Solids (Turbidity)
and Sediment. Numbers refer to references listed in Table A-4.
Species Effect Impact through
Spawning
General
Suspended solids
Sediment
Etheostoma
blennic^ses
30
30
Etheostoca exile
27, 30
2 7,30
Etheostoma tippecanoe
27
27
Etheostoma zonale
29
29
Perca flavescens 25,30
25,30
25,30
25,30
Percina caprodes
7,30
7
30
Percina cocelandi
2 7,30
2 7, 30
2 7,30
Percina evides
29,30
30
29
Percina maculata
30
30
Percina phoxocephala
2 7,30
2 7, 30
2 7,30
A-3
-------
TABLE A-2
Warmwater Fishes which are Tolerant of Suspended Solids and Sediment.
Numbers refer to references listed in Table A-4.
General Preference
Spades tolerance for curbid systems
Scaphirhvnchus albus
7
Dorosoma cepedianua
30
Hiodon alosoldes
25, 30
Carassius auracus
30
CouesiLS plumbeus
3
Cypririus carpio
19, 25,
30
Ericvmba buccata
5, 14,
30
27
Hybopsis Relida
5
Hybopsis (gracilis
5
27
Nocropis dorsalls
Nocropls lucrensls
7, 27
Orchodon microlepidotus
19
Fhenacobius mirabilis
7, 30
Phoxinus oreas
9
Piaephales promelas
7, 30
29
Piaephales visilax
7, 30
PlaRopterus ar(?eatissimus
5
Semotilus acromaculatus
7, 22
29
Catostomus commersonl
9, 30
Icciobus cyprinellus
7, 25,
30
Moxostoma erychrurum
30
Ictalurus cacus
30
Iccalurus melas
7
25, 30
Aphredoderus sayanus
30
Lepomis cyanellus
7, 30
Lepomis humilis
7 27
' » — ' »
30
Lepomls microlophus
29
Micropterus punctulatus
11. 23
, 30
Micropcerus treculi
18, 23
Pomoxis annularis
12, 26
, 30, 31
Pomoxis nigromaculatus
7, 12,
20, 25
Etheostoma stracile
7
Etheostoma nicroperca
30
Etheostoma nigrum
30
Etheostoma spectabile
7, 30
Stixostedion canadense
6, 25,
30
Aplodlnotus xrunniens
30
A-4
-------
TABLE A-3
Warmwater Fishes for which Contradictory Information was found on
their Tolerance or Intolerance to Suspended Solids and Sediment.
Numbers refer to references listed in Table A-4.
Species Tolerant Intoleranc
Caaooscosa anomaluc
Cllnoscomus funauloides
Hvbognachus nuchalis
Nctropis buchanani
N'ciropis spilopterus
Nocropis umbracilis
Pinepnales nocacus
Rhinichchvs acratulus
Carpiooes carpio
Ictalurus nebulosus
Iccalurus punccacus
Morone chrvsops
Lepomis gulosus
Lepomis aacrochirus
Echeostaaa flabellare
Stizoscedion vitreum
7
30
9
27
2, 7
30
7
30
30
7, 10
5, 29
7, 30
30
7
9
30
7, 30
5
20
30
7, 16,
17
4, 25,
20
25, 30
15
30
20
9, 30
25, 30
'9
1, 20,
25
27 , 30
A-5
-------
TABLE A-4
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A-6
-------
TABLE A-4 (Continued)
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29. Smith, P.W. 1971. Illinois streams: a classification based on their
fishes and an analysis of factors responsible for disappearance of
native species. 111. Nat. Hist. Surv. Biol. Notes No. 76.
A-7
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TABLE A-4 (Continued)
30. Trautman, M.B. 1957. The fishes of Ohio. Ohio State Univ. Press,
Columbus. 683 pp.
31. Vasey, F.W. 1971. Early life history of white crappie in Table Rock
Reservoir. Missouri Conserv. Comm. Proj. No. Mo. F-001-R-20/wk. PI.
07/Job 01/1. 23 pp.
A-8
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APPENDIX B
SOIL CONSERVATION SERVICE
LAND RESOURCE REGION DESCRIPTIONS
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LAND RESOURCE REGIONS
The United States (IB conterminous States) has been divided Into 156 major land resource
areas. These areas hare been delineated on the basis of similarities in relationships
to agriculture; the emphasis is on combinations or intensities of problems in soil and
water conservation, or both. They are characterized by particular combinations or
patterns of soils (including slope and erosion), climate, water resources, land use,
and kinds of farming. They are designated on the land resource region map by numbers
and names. They are not described in this Atlas, but their descriptions will be avail-
able in a later Soil Conservation Service publication.
The 156 major land resource areas have been grouped into 20 land resource regions,
designated on the map by large capital letters and names. In this grouping, the
objective has been to retain as much similarity as possible in agricultural relation-
ships within each region. Brief descriptions of these regions follow. In the interest
of brevity, the information about soils is given in terms of great soil groups, a high
category in the current soil classification system. Grief general descriptions of the
great soil groups in alphabetical order follow the descriptions of the 20 land resource
regions.
A NORTHWESTERN FOREST, FORAGE, AND SPECIALTY CROP REGION
This is a region of steep mountains and narrow to broad, gently sloping valleys and
plains. The annual precipitation ranges frcm £0 to 70 Inches over much of the region,
but it is 30 inches or less in sane valleys and as much as 200 Inches in some of
the higher mountains. All parts of the region have a pronounced dry season in summer.
The average annual temperature is 50° F. over most of the region, but it is A0° F. or
less in some of the mountains. The freeze-free season is more than 200 days in the
valleys, but the length decreases markedly with elevation In the mountains.
Reddish-Grown Lateritic soils, Yellowish-Brown Iateritic soils, Grown Forest soils,
Ando soils, Sols Bruns Acides, and Lithosols are the principal soil groups in the
mountains and uplands. Alluvial soils, Brunizems, Brown Podzolic soils, and Humic
Gley soils are extensive in the valleys.
The mountains are heavily forested, and lumbering is a major Industry in the region.
Dairy farming is Important In the valleys with higher rainfall; grain crops, grass
and legume seeds, fruits, and horticultural specialties are grown extensively in the
drier valleys.
B NORTHWESTERN WHEAT AND RANGE REGION
This region consists mainly of smooth to deeply dissected plains and plateaus, but
it Includes seme mountain ranges. The annual precipitation ranges from about 10 to
20 inches; there is very little rainfall In summer. The average annual temperature
is 45° F.; the freeze-free season ranges frcm 120 to 160 days except in the mountains
where it is shorter.
Brown soils, Chestnut soils, Sierozems, Chernozems, and Brunizems, all derived mainly
from loess, are dominate over much of the region. Ando soils are conspicuous in
places where the parent materials consist mostly of volcanic ash. Lithosols occur on
the steep slopes underlain by basalt uid lava. Alluvial soils on the flood plains are
important for agriculture.
Wheat grown by dryfarmlng methods is the uajor crop over most of the region, but oats
and peas are important also. Fruit, mainly apples, is a major crop in the western
part. Grazing is the major land use in the drier parts, especially in the west.
B-l
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C CALIFORNIA SUBTROPICAL FRUIT, TRUCK AND SPECIALTY CROP REGION
This is a region of low mountains and broad valleys. It has a long, wars growing
season and low precipitation. The annual rainfall ranges froa 30 Inches to less
than 10 inches; very little occurs from late April through October. The average
annual temperature is 60° F. over most of the region, but it is as low as 45° F. at
some of the higher elevations. The freeze-free season averages 250 daya for much
of the region, but it ranges froa 150 days or less in same of the higher mountains
to more than 300 days in the valleys in the south.
Noncalcic Brown soils, Grumusols, and Brunizems are extensive on the uplands and
older terraces throughout the region, but Alluvial soils and Humie Gley soils oh
flood plains and alluvial fans are the most important soil groups for agriculture.
Many of the soils on flood plains and low terraces are affected to varying degrees
by Baits, so that skillful management is required for satisfactory crop yields.
This region has a vide variety of crops and agricultural enterprises. Citrus fruits,
other subtropical and tropical fruits, and nuts are major crops in the southern half.
Many kinds of vegetable crops, grown mainly under irrigation, are produced throughout
the region. Rice, sugar beets, cotton, grain crops, and hay are also important.
Dairying is a major enterprise near the large cities. Beef-cattle production on feed
lots and range is also important.
D WESTERN RANGE AND IRRIGATED REGION
This is a semidesert to desert region of plateaus, plains, basins, and many Isolated
mountain ranges. The annual precipitation is 10 inches or less over most of the
plains and basins, but it is slightly more on tte higher mountains. In the south-
eastern part the maximum amount of rainfall occurs during the warm season, but
elsewhere precipitation, is higher in the cool season. The average annual tempera-
ture for the region as a whole is 50° F., but it ranges froa 12° F. at the higher
elevations in the north to more than 70° Fi in seme of the lowlands in the south.
The freeze-free season ranges from less than 120 days in the north and in seme of
the higher mountains to more than 200 days in the south.
Sierozems, Desert soils, Brown soils, and Grumusols are entensive on the plains,
plateaus, and valleys throughout the region. Chestnut soils, Chernozems, and Gray
Wooded soils are on some of the mountain slopes. Alluvial soils, Soloneiz soils,
and Solonchak soils in the plains and basins and lithosols on the mountain slopes
are also important.
Much of the land in this region is used for range, but irrigation agriculture is
practiced where water is available and Boils are favorable. Feed crops for live-
stock occupy much of the irrigated land, but peaB, beans, and sugar beets are
grown in many places. Cotton and citrus fruit are important in southwestern
Arizona.
E ROCKY MOUNTAIN RANGE AND FOREST REGION
Rugged mountains dominate this region, but some broad valleys and high plateau rem-
nants are included. The annual precipitation ranges from 20 to LQ Inches over much
of the region, but it is less than 10 Inches in some valleys and 50 Inches or more
on some of the mountain peaks. The average annual temperature is L0° to £5°F. The
freeze-free season is 100 to 120 days in the valleys and basins, but the length
decreases to 60 days or less with increasing elevation In the mountains. Seme of
the highest mountains are covered by glaciers and have perpetually frozen ground.
Chestnut soils, Chernozems, and Brown soils are the dominant soil groups in the
valleys and on the lower mountain slopes. Gray-Brown Podzolic soils, Gray Wooded
soils, Podzols, and Alpine Meadow soils are on the upper mountain slopes and crests.
Lithosols are extensive on the steep mountain slopes, and Alluvial soils are im-
portant in the valleys.
Grazing Is the leading land use in both the valleys and the mountains, but lumbering
is important in some of the forested mountain areas. Recreational land uses are
important throughout the region. Irrigation agriculture is practiced in sane of
the valleys and dryfarming in others. Grain and forage for livestock are the main
crops; beans, sugar beets, peas, and seed crops are also grown where soils, climate,
and markets are favorable.
B-2
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F NORTHERN GREAT PLAINS SPRING WHEAT REGION
The fertile soils and the daninantly smooth topography are favorable far agriculture
In this region, but the low rainfall and the short growing season lapose severe re-
strictions on the crops that can be grown. The annual precipitation ranges from 11
to 24 inchest a large part of it occurs during the growing season. The average
annual temperature is £0°F. The freeze-free season ranges from 110 to 125 days,
increasing In length from north to south.
Chernozems and Chestnut soils are dominant over most of the region, but Brows soils
cover the western part. Lithosols on steep slopes, Solonetz soils, Solonachak soils,
and Humlc Gley soils on terraces and in depressions, and narrow bends of Alluvial
soils along the major streams are also Important.
The production of spring wheat by dryfamlng methods dominates the agriculture of
the region. Other spring grains, flax, and hay are also produced. Potatoes are
grown in many places, and sugar beets and corn are Important in the Red River Valley
in the east.
G WESTERN GREAT PLAINS RANGE AND IRRIGATED REG.
This is the section of the Great Plains where unfavorable soils, strong slopes, or
low moisture supplies make success at dryfarming very uncertain. The annual precipi-
tation ranges frco 11 to 20 inches, but it is highly variable frcn year to year. The
average annual temperature is £5°F. for the region as a whole, but It ranges from
£0°F. in the north to 60° F. in the south. The freeze-free season ranges from 105
days in the north to 180 days in the south.
Chestnut soils are dominant over much of the region, but Brown soils are Important in
the west. Lithosols on the more sloping parts of the dissected areas, Regosols on
sands, and Alluvial soils In bands on flood plains are also extensive. less extensive,
but Important locally, are Grumusols on heavy clay and Solonetz soils in depressions
and on terraces.
A large part of the region is in range, but some wheat is produced by dryfrarming
methods, mainly along the eastern margin. Irrigation agriculture is practiced
along sane of the major rivers. Forage and grain for livestock are the principal
crops on Irrigated land; potatoes, sugar beets, and vegetable crops are Important
locally.
H CENTRAL GREAT PLAINS WINTER WHEAT AND RANGE REGION
Soils, topography, and climate are more favorable for agriculture in this region +>"¦"
in the Great Plains to the west. The longer freeze-free season permits a greater
variety of crops to be grown than in the northern Great Plains. The average annual
precipitation is 25 Inches, but it ranges from 18 to 32 inches, increasing from north-
west to southeast. More rain falls in summer than in the rest of the year. The average
annual temperature la 50° to 55° F. The average freeze-free season 1b 180 days, but the
length ranges from 160 to 215 days, increasing frco north to south.
The Important soils in the northern part are in the Chernozem and Chestnut groups.
Reddish Prairie soils and Reddish Chestnut soils are extensive In the south,
lithosols on steep slopes, Regosols on deep sands, and Alluvial soils on flood
plains are common throughout the region.
Cash-grain fanning with wheat as the principal crop is the major agricultural enter-
prise on most of the better soils. Grain sorghum is grown in many of the drier areas.
In the southern part of the region where the freeze-free period exceeds 200 days,
cotton is grown extensively under irrigation from wells. The steeply sloping shallow
and sandy soils are used for range.
B-3
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I SOUTHWESTERN PLATEAUS AND PLAINS, RANGE AND COTTON REGION
This region consists of the warmer part of the southern Great Plains. The moderate
precipitation is accompanied by high temperatures, so that the precipitation effective-
ness is low. The average annual precipitation is 25 inches: usually much of it occurs
in spring and autumn. The average annual temperature is 67 F., and the freeze-free
season averages 2S0 days.
The soils on the deeper coarse- and medium-textured materials are mostly members of
the Reddish Chestnut and Reddish Prairie groups. Grumusols on limestones and marls
and IAthosols and Calcisols on hilly to steep slopes on all kinds of parent material
are also fairly extensive.
Range is the dominant land use over most of the region, but some wheat, other small
grains, and grain sorghum are grown where soils, topography, and moisture supplies
are favorable. In the southeastern part, cotton grown under irrigation is Important.
Citrus fruits and winter vegetables are grown along the lower Rio Grande Valley.
J SOUTHWESTERN PRADUES, COTTON AND FORAGE REGION
This region consists of the prairies and the timbered areas of eastern Texas. The
average annual precipitation ranges from 30 to 38 inches. The average annual
temperature 1b 65°F., and the freeze-free season ranges from 220 to 260 days.
Grumusols, Rendzinas, and LLthosols on limestone and chalks are the more extensive
soils in the region. Red-Yellow Podzolic soils, Planosols, and Reddish Prairie
Boils are also Important groups.
The region is intensively farmed. Cotton, grain sorghums, other feed grains, and
hay are important crops. Most of the more sloping areas in the western part of
the region are in open timberland, which is used for grazing.
K NORTHERN LAKE STATES FOREST AND FORAGE REG.
Poor soils and a cool, short growing season Impose severe restrictions on agriculture
in this region. The annual precipitation ranges from 22 to 32 inches; the heaviest
rainfall occurs during the growing season. The average annual temperature is £0°F.,
and the freeze-free season ranges from 110 to LiO days.
Podzols on sandy parent materials and Gray Vooded soils on the finer textured parent
materials are the dominant soils in the better drained areas. Bog soils, Humic Gley
soils, Iflv-Humic Gley soils, and Ground-Water Podzols occupy the wetter uplands and
depressions, IAthosols and rough Btony land are extensive on hills and low mountains.
A large part of this region 19 forested, and lumbering and recreation are the principal
uses. Mining is a major industry in all but the eastern part of the region. Forage
and some grains for livestock are the main crops cn the farmed areas. Potatoes are
Important locally.
L LAKE STATES FRUIT, TRUCK,'AND DAIRY REGION
This region consists of nearly level to gently sloping, glaciated plains. The soils
and climate arc favorable for agriculture. The average annual precipitation is 33
inches and is distributed fairly evenly throughout the year. The average annual
temperature ranges from 15° to 50°F. The freeze-free season is about 150 days,
except in narrow belts adjacent to the Great lakes where it is as much as 180 days.
Gray-Brown Podzolic soils are dominant throughout this region, but Humic Gley soils,
Low-Humic Gley soils, and Bog soils are fairly extensive in the level areas and
depressions.
The region has a wide variety of agricultural enterprises. Dairy farming la important,
especially near the larger urban centers. Canning crops, .com, soft winter wheat,
beans, and sugar beets are among the leading crops. Fruit growing is very Important in
a narrow belt adjacent to the Great lakes. Rural residences occupy much land near many
of the larger cities, and some farming is done on a part-time basis by people who earn
their main living in the cities.
B-4
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M CENTRAL FEED GRAINS AND LIVESTOCK REGION
Fertile soils and favorable climate make this one of the outstanding grain-proHucing
regions of the world. The annual precipitation ranges from 26 to L2. Inches; somewhat
more thanQhalf falls during the growing season. The average annual temperature is
£5° to SO F. The freeze-free season averages 170 dayB} it ranges from 150 days in the
north to 200 days in the southernmost parts.
Gray-Brown Podzolic soils in the east and Brunizems in the west are the dominant soils
of the region. Humic Gley soils and Bog soils in the wet lowlands and Alluvial soils
in bands along the major streams are also important.
Corn, soybeans, oats, and other feed grains are the most extensive crops of this
region. Hay, winter wheat, and a variety of'other crops are also grown. Much of
the grain is fed to beef cattle and hogs on the farms where it is grown, but large
amounts are shipped to other regions for use as livestock feed. Part is processed
for food products and for Industrial uses.
N EAST AND CENTRAL GENERAL FARMING AND FOREST REGION
This region is the borderland between the North and the South. It occupies the
Appalachian mountains, valleys, and dissected plateaus and the Ozarks. The annual
precipitation ranges from L2 to 5L inches, and the seasonal distribution is fairly
even. The freeze-free season averages 180 days, but it ranges from 150 days to 200
days.
Sols Bruns Acides are the more extensive soils on the sandstones and acid shales of
the mountain slopes and dissected plateaus. Red-Tellow Podzolic soils are on the
limestones and the more deeply weathered shales. Reddish-Brown Lateritic soils are con-
spicuous in some limestone valleys and basins, but their total area is small. Alluvial
soils along the many streams are of small total extent, but they are intensively used
for cropland throughout the region. ,
Small general farms are characteristic of much of the region, but there are large
dairy and livestock farms on some areas of the more favorable soils. Corn, small
grains, and hay are the most extensive crops. Tobacco is an important cash crop,
especially in the eastern two-thirds of the region. The steeply sloping areas,
amounting to nearly one-half of the region, are mainly in forests, which are used
both for recreation and timber production. A large part of the Nation's coal is
mined in this region.
0 MISSISSIPPI DELTA COTTON AND FEED GRAINS REGION
This region includes the flood plains and terraces of the Mississippi River south of
its confluence with the Ohio River. The average annual precipitation is 50 to 55
inches. The average annual temperature is 65°F., and the freeze-free season is 220
to 21.0 days Jong. Low-Humic Gley soils, Humic Gley soils, Alluvial soils, and
Grumusols are the extensive soil groups on the flood plains and low terraces. Red-
Tellow Podzolic soils are Important on the higher, silt-mantled terraces.
The soils throughout much of the region are naturally poorly drained and poorly suited
to crops, but they are well suited to crops and are highly productive if artificially
drained. Cotton, soybeans, corn, and hay are grown throughout the region. Rice in
Arkansas and Louisiana and sugarcane in Louisiana are Important crops locally. The
wettest areas that are not artificially drained remain in forest and are important
for hardwood-timber production.
P SOUTH ATLANTIC AND GULF SLOPE CASH CROP, FOREST, AND LIVESTOCK REGION
This is the traditional cotton region and consists of gently sloping to rolling
Southern Piedmont and upper Coastal Plain. The average annual precipitation ranges
from 15 to 55 inches; rainfall is considerably higher in midsummer than In the rest
of the year. The average annual temperature is more than 60°F. The freeze-free
season averages 2£0 days for the region as a whole, but it ranges from 220 to 290
days.
B-5
i
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Red-Yellow Podzolic soila are dominant throughout the region. Reddish-Brown lateritic
soils on basic rocks are conspicuous locally as are Grumusols on some marls or soft
limestones. Alluvial soils on the flood plains of the major streams are among the
better crop-suited soils.
Cotton is the main cash crop throughout the region, but the acreage in cotton has been
declining for many years. Peanuts and tobacco are also important, especially in the
northeastern part of the region. The acreage in improved pasture has been increasing,
and much of the more sloping land is being returned to forest.
R NORTHEASTERN FORAGE AND FOREST REGION
This region consists of relatively cool, humid plateaus, plains, and mountains. The
annual precipitation ranges from 35 to 15 inches; more than one-half falls during the
freeze-free season in most of the region. The average annual temperature is 4.0° to
45° F. The freeze-free season is 120 to 160 days over most of the region, but it is
somewhat less than 120 days in the higher mountains and aa much no 1R0 dnyo In n rvirrow
belt along the Atlantic Conot.
Sols Bruns Acides and Podzols, both commonly with fraglpans, are the dominant soils of
the region. Humic Gley soils, Low-Humic Gley soils, and Bog soils occupy the lowlands
and depressions. Stoniness imposes serious restrictions on the use of many of the soils
in this region.
The production of forage for dairy cattle is the principal land use of much of the farm-
land in the region. Fruit, tobacco, potatoes, and various vegetable crops are important
locally where markets, climate, and soils are favorable. The steeper lands are mainly
in forests, which produce significant amounts of timber. Recreational uses are
probably more important for much of the forested land in this highly urbanized region.
S NORTHERN ATLANTIC SLOPE TRUCK, FRUIT, AND POULTRY REGION
This region consists of the gently to steeply sloping Northern Coastal Plain, Northern
Piedmont, and Northern Appalachian Ridges and Valleys. The average annual precipitation
ranges from LO to £5 inches with only a slight maximum in midsummer. The average annual
temperature is 51°F., and the freeze-free season is about 180 days.
Soils on the steep slopes are mainly Sols Bruns Acides. On the gentle slopes Red-Iellow
Podzolic soils are dominant, but some soils, mainly on limestone materials, are members
of thB Gray-Brown Podzolic group.
Poultry and dairy farming are the leading agricultural enterprises in the region, but
fruit and truck crops are also important in many places. Many farms are operated on
a part-time basis by people who earn most of their living in the cities. Rural resi-
dences occupy some areas where the land is less favorable for farming. The encroach-
ment of urban areas onto farmland is a problem throughout the region. Steep slopes are
largely in forests, which are used both for timber production and for recreation.
T ATLANTIC AND GULF COAST LOWLANDS, FOREST AND TRUCK CROP REGION
This region consists of the low, nearly level parts of the Atlantic and Gulf Coastal
Plains.
The annual precipitation averages 50 inches in most of the region but falls off sharply
in the extreme western part. The average annual temperature is 65°F. The freeze-free
season ranges from 220 days in the north to 300 or more days in the south.
Icw-Humic Gley soils, Ground-Water Podzols, and Bog soils are dominant along the
Atlantic and Gulf Coasts east of the Mississippi River Delta. West of the Mississippi
River Delta, Grumusols and Planosols are the principal soil groups.
Most of the soils are too wet to be used as cropland without artificial drainage.
Drained areas are used mainly for growing truck crops and*cotton and, to seme extent,
for improved pastures. Sugarcane and rice are important crops in Louisiana and east
Texas. Undrained areas to the east of the Mississippi River Delta remain in forest.
B-6
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U FLORIDA SUBTROPICAL FRUTT. TRUCK CROP AND RANGE REGION
This region consists of the southern two-thirds of the Florida peninsula. The average
annual precipitation is in excess of 50 inches throughout the region. The average
annual temperature is above 70°F., and the freeze-free season ranges from 280 days in
the north to 365 days in the south. A large part of the region lies south of the
southern limit of annual frost.
Ground-Water Podzols, Iow-Humic Gley soils, and Bog soils are the dominant soil groups
on the flat lands, whereas Red-Yellow Podzolic soils and sandy Regosols are dominant on
the higher, more sloping ridges. There are extensive areas of Lithosols on coral lime-
stones in the southern part of the region.
Citrus fruits, other subtropical fruits, and winter vegetables are the major crops
throughout the region, but slightly more land is in pasture* than in crops. More than
two-thirds of the region is in forest or other native vegetation, much of which is
grazed. Beef cattle are the principal livestock, but dairying is important near the
larger cities. Sugarcane is a major crop locally in the south, arid its acreage has
been increasing rapidly in recent years.
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