Proceedings of the Advanced 

Seminar on Sedimentation, 

August15-19, 1983, 

Denver, Colorado 

G. Douglas Glysson, Editor 

U.S. GEOLOGICAL SURVEY CIRCULAR 953 

1987 
Department of the Interior 

DONALD PAUL HODEL, Secretary 

U.S. Geological Survey 

Dallas L. Peck, Director 

Library of Congress Cataloging-in-Publication Data 

Advanced Seminar on Sedimentation (1983; Denver, Colo.) 

Proceedings of the Advanced Seminar on Sedimentation, 

August 15-19, 1983, Denver, Colorado 

(U.S. Geological Survey Circular 953) 

Includes bibliographies 

Supt. of Docs. No.: I 19.4/2:953 

1. Sedimentation and deposition-Congresses. 2. Sediment 

transport-Congresses. 3. River channels-Congresses. 

4.Sediments (Geology)-United States-Congresses. 

I. Glysson, G. Douglas. II. Title. III. Series: 

United States. Geological Survey. Circular 953 

QE57l.A25 1983 551.3'5 85-600102 

Free on application to the Books and Open-File Reports Section, 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 
CONTENTS 

Page 

Introduction, by G. Douglas Glysson _____________________ 1 

Summaries of the presentations _________________________ 2 

Modeling _ _ _ _ ___ _ _____ _ _ _ _ _ _ _ _ _ _ _ _ __ ____ _ _ _ _ _ _ _ _ _ _ 2 

Modeling water-discharge and sediment-concentration hydrographs at surface mine sites in 

Pennsylvania, by Lloyd A. Reed ______________ 2 

Preliminary investigation of the physical basis 

of soil erosion parameters in the PrecipitationRunoff Modeling System (PRMS), by William 

P. Carey and Andrew Simon __________________ 3 

Reducing sediment sampling frequency at 

streamflow gaging station Rio Grande at Otowi 

Bridge near San Ildefonso, New Mexico, 

by David H. Marshall ________________________ 4 

Comparison of digital modeling techniques which 

simulate sedimentation processes in an agricultural watershed, by Leslie D. Arihood _______ 6 

Instrumentation ----------------------------------- 7 

Measurement of suspended sediment in surface 

waters: A discussion of new technologies that 

will operate continuously and unattended, 

by Marvin C. Goldberg _______________________ 7 

Instrumentation for automatically monitoring 

sediment concentration and particle sizeA progress report, by James H. Ficken ________ 8 

Progress report on testing of the Sedigraph 

particle size analyzer, by Bill Matthes _ _ _ _ _ _ _ _ _ _ 8 

The Dynatrol test site, Madison, Wisconsin, 

by Gerald Goddard __________________________ 9 

Determining sediment concentration with a fluiddensity cell, by J. V. Skinner __________________ 10 

Monitoring streambed changes and sediment 

concentrations using the acoustic velocity 

meter, by Antonius Laenen ___________________ 10 

Mud and debris flows ------------------------------ 12 

Geobotanical evidence of debris flows on Mount 

Shasta, California, by Cliff R. Hupp and W. R. 

Osterkamp --------------------------------- 12 

Downstream dilution of lahars from Mount St. 

Helens, Washington: Defining the boundary 

between debris flow and hyperconcentrated 

streamflow, by Thomas C. Pierson and 

Kevin M. Scott ------------------------------ 16 

Stream channel adjustments to 1980 lahars and 

subsequent stormflow, Mount St. Helens, by 

Holly A. Martinson and David F. Meyer ________ 17 

Erosional development of the North Fork Toutle 

debris avalanche deposit, by David F. Meyer 

and Richard J. Janda _________________________ 19 

Sediment transport ________________________________ 21 

Erosion and landform modification at a low-level 

III 

Page 

Summaries of the presentations-Continued 

radioactive waste disposal facility near Sheffield, 

Illinois, by John R. Gray _____________________ 21 

Estimating long-term sediment discharge-which 

method to use? by Thomas H. Yorke ___________ 22 

Sediment budget of the tidal Potomac River and 

estuary, water years 1979-81, by R. Edward 

Hickman and James P. Bennett _______________ 24 

Effects of the proposed Cooper River rediversion 

on sedimentation in Charleston Harbor, South 

Carolina, by Glenn G. Patterson _______________ 26 

Sediment chemistry ------------------------------- 26 

Determination of lake sedimentation rates by lead210 and cesium-137, by I. G. Yang ___________ 26 

Inorganic partitioning in sediments, by Arthur J. 

Horowitz ___________________________________ 27 

Transport of suspended sediment and associated 

chemical constituents in the Lower Mississippi 

River, Louisiana, by Charles R. Demas and 

Philip B. Curwick --------------------------- 28 

Suspended sediment: Transport and chemistry 

of organic carbon, by E. Michael Thurman ______ 29 

Channel morphology ------------------------------- 30 

Sediment impacts from coal mining, northeast 

Tennessee, by Waite R. Osterkamp, William P. 

Carey, and Cliff R. Hupp _____________________ 30 

Unit hydraulic geometry-An indicator of channel 

changes, by Rhea P. Williams _________________ 31 

Channel adjustment to man-induced stress in west 

Tennessee, by Andrew Simon and Clarence H. 

Robbins ------------------------------------32 

Contrast in stream channel response to major 

storms-Examples from two mountainous areas 

in California, by K. Michael Nolan and Donna C. 

Marron _____________________________________ 33 

Effects of dam construction on channel geometry 

and bed material in Bear Creek, Denver, Colorado, by R. F. Hadley and W. W. Emmett _____ 35 

Sediment storage and discharge in steep unstable 

terrain, by Richard J. Janda __________________ 35 

Bedload __________________________________________ 37 

Variability in measured bedload transport during 

constant and slowly changing water discharge 

conditions, by William P. Carey _______________ 37 

Some characteristics of fluvial processes in rivers, 

by William W. Emmett, Luna B. Leopold, and 

Robert M. Myrick --------------------------- 38 

Measurement of bedload discharge in nine Illinois 

streams with the Helley-Smith sampler, by 

Julia B. Graf -------------------------------- 39 

List of Attendees -------------------------------------- 41 
ILLUSTRATIONS 

Page 

FIGURE 1. Graph showing hydrographs of water discharge and suspended-sediment concentration computed by PRMS ------- 3 

2. Diagram showing types of botanical evidence of debris flow--------------------------------------------------- 13 

3. Map showing location of the study areas on Mount Shasta, Calif. ---------------------------------------------- 14 

4. Diagram showing representative cross section of Ash Creek near Military Pass, Calif. --------------------------- 16 

5. Graph showing dominant fluvial processes, Pine Creek and South Fork Toutle River, 1980-81 -------------------- 18 

6. Graph showing dominant fluvial processes, Pine Creek and South Fork Toutle River, 1981-82 ____________________ 18 

7. Graph showing drainage integration, with time, of the upper North Fork Toutle River basin, above 

the N-1 debris retention structure -----------------------------------------------------------------------20 

8. Diagram showing Dekaport divisor system ----------------------------------------------------------------- 23 

9. Diagram summarizing the use of botanical evidence to date recent flow events along Smoky Creek, 

northeastTennessee -----------------------------------------------------------------------------------32 

10. Diagram showing schematic representation of positive feedback between physical processes in 

northwestern California ________________________________________________________________________________ 34 

11. Graph showing variability of 120 consecutive bedload samples ------------------------------------------------ 37 

12. Graph showing theoretical and sampled distributions of relative transport rates -------------------------------- 37 

13. Graph showing variability of 120 consecutive bedload samples after smoothing --------------------------------- 38 

TABLES 

Page 

TABLE 1. Information on rills and gullies used in PRMS subroutine ---------------------------------------------------- 3 

2. Summary of debris flow dates at sites on Whitney and Bolam Creek, Calif. ---------------------------------- ___ 15 

3. Summary of debris flow dates on Mud Creek, Calif. --------------------------------------------------------- 15 

4. Summary of debris flow dates on Ash Creek, Calif. ---------------------------------------------------------- 15 

5. Correlation coefficients and standard errors of estimate of relations between the logarithms 

of water discharge and concentrations of sediment, sand, silt, and clay in suspension for the 

Schuylkill River at Manayunk, Penn. _____________________________________________________________________ 24 

6. Measured and estimated suspended-sediment discharges of the Schuylkill River at Manayunk, 

October 1, 1953, to September 30, 1979 -------------------------------------------------------------------25 

CONVERSION FACTORS 

For use of readers who prefer to use metric units, conversion factors for terms used in this report are 

listed below: 

Multiply 

inch (in.) 

square inch (in.2) 

foot (ft) 

foot per second (ft/s) 

square foot (ft2) 

cubic foot (ft3) 

cubic foot per second (ft3/s) 

mile (mi) 

square mile (mi2) 

acre 

acre-foot (acre-ft) 

ton (t) 

ton per square mile (t/mi2) 

gallon (gal) 

ounce (oz) 

by 

2.540 

6.452 

0.3048 

0.3048 

0.09294 

0.02832 

0.02832 

1.609 

2.590 

0.4047 

1,233. 

0.9072 

0.3503 

3.785 

28.35 

to obtain 

centimeter (em) 

square centimeter (cm2) 

meter (m) 

meter per second (m/s) 

square meter (m2) 

cubic meter (m3) 

cubic meter per second (m3/s) 

kilometer (km) 

square kilometer (km2) 

hectare 

cubic meter (m3) 

megagram (Mg) 

megagram per square kiloliter (L) 

gram (g) 

meter (Mg/km2) 

The use of brand names in this report is for identification purposes only and does 

not imply endorsement by the U.S. Geological Survey. 

lV 
Proceedings of the Advanced 

Seminar on Sedimentation, 

August 15-19, 1983, Denver, Colorado 

Introduction 

By G. Douglas Glysson 

On August 15-19, 1983, the Water Resources Division of the U.S. Geological Survey (USGS) sponsored an advanced seminar on sedimentation at the 

National Training Center in Lakewood, Colo. Topics 

discussed included modeling, mud flows and debris 

flows, sediment transport, sediment chemistry, 

channel morphology, instrumentation, and bedload. 

This Circular presents summaries of the 27 presentations given at the seminar plus one additional summary that was not presented. 

The term sedimentation encompasses the processes of erosion, entrainment, transportation, 

deposition, and the compaction of sediments (Vanoni, 1975). Historically, the Water Resources Division (WRD) has primarily limited its efforts to the 

study of the transport and deposition processes. 

Some geomorphologic studies have been conducted, 

the majority of the work being done in the WRD's 

national research program. 

Several major events over the past few years have 

brought increased public awareness to the sedimentation problem. Notable are the eruption of Mount 

St. Helens, Wash., dioxin in the sediments at Times 

Beach, Mo., and the rapid erosion of the offshore 

islands off the coast of Louisiana. Not so noticeable 

have been the introduction of new chemicals as 

pesticides and fertilizers, and the seepages and 

direct erosion from waste-disposal sites. 

In order to adequately assess our Nation's water 

resources, the WRD has, over the last several years, 

expanded its field of study to include all five processes of sedimentation. The division is investigating the ro]e sediment plays in the transport and 

deposition of certain chemicals. The sediment particles may sorb these chemicals from the water and 

release them back into solution, depending on the 

physical and chemical environment. The WRD is 

also studying the effects that the sedimentation processes have on the ecosystem of our nation's waterways. 

In an effort to improve the effectiveness of the 

division's expanding sediment program, the Quality 

of Water Branch organized an Advanced Seminar on 

Sediment, which was held August 15-19, 1983, at the 

USGS National Training Center in Lakewood, Colo. 

The objectives of this seminar were (1) to bring 

together the division's research, district, and headquarters personnel who are actively engaged in geomorphology or sedimentation-related studies to 

discuss mutual problems, and (2) to provide a forum 

for the effective transfer of sediment-related technology. The purpose of this Circular is to present 

summaries of the presentations made at the seminar. 

It is hoped that, by presenting these summaries, the 

technology transfer process can be extended to 

those who were unable to attend the seminar. 

REFERENCE CITED 

Vanoni, V. A., 1975, Sedimentation Engineering: American 

Society of Civil Engineers Manual of Engineering Practice 

No. 54, 745 p. 
Summaries of the Presentations 

Modeling 

Modeling Water-Discharge and Sediment-Concentration Hydrographs 

at Surface Mine Sites in Pennsylvania 

By Lloyd A. Reed 

Rainfall, water-discharge, and suspended-sediment data were collected at several surface mine 

sites in the bituminous coal fields of Pennsylvania. 

These data were used to refine the Precipitation 

Runoff Modeling System (PRMS) of Leavesley and 

others (1983). PRMS is a modular design modeling 

system developed to evaluate the impacts of various 

combinations of precipitation and land use on water 

discharge and sediment yields. PRMS computes 

hydrographs of water discharge and suspended-sediment concentration for small and large basins 

affected by single or multiple land uses. The subroutine described here runs on a Tektronix 4051 

computer and calculates water discharge and suspended-sediment concentration hydrographs for 

storms up to 24 hours in duration. 

The model begins with observed precipitation and 

calculates precipitation excess and the sediment dislodged during the storm. Observed rainfall at 5-

minute increments is stored in a 288-unit array by 

the model user. Precipitation excess is computed for 

each 5-minute increment by subtracting infiltration, 

calculated by the Green Ampt/Philip infiltration 

model (Green and Ampt, 1911) from total precipitation. Sediment dislodged from the mined area during each 5-minute increment is computed in two 

steps. A relation between precipitation intensity and 

suspended-sediment concentration that varies linearly with soil erodibility is used to calculate a suspended-sediment concentration (as a ratio). The 

suspended-sediment concentration is multiplied by 

the precipitation excess to determine the tons of 

sediment dislodged from each acre for each 5-minute 

increment. 

After the values of precipitation excess and sediment production are calculated and stored in arrays, 

PRMS moves to a routing subroutine and routes the 

2 

water and sediment from the mined area, producing 

a hydrograph of water discharge and sediment concentration. The precipitation excess and sediment 

production from the first 5-minute period are 

recalled and divided into 1-minute intervals. PRMS 

distributes the precipitation excess and the sediment from the first interval onto the mined area. The 

precipitation excess and sediment distributed on the 

mined area is accumulated in rills and gullies, and 

equations for open-channel flow and sediment deposition are used to route the water and sediment from 

the mined area. The size and number of rills and 

gullies used by PRMS were selected after inspection 

of several regraded surface mine sites. 

The rills and gullies, which ranged in size from 

just noticeable to several inches wide, were classified from 1 to 4. Small rills (class 1) joined and formed 

larger rills, or discharged directly to larger rills and 

gullies; large rills joined and formed gullies, or discharged directly to gullies or to the diversion channel. Thble 1 lists information about the rills and 

gullies used in this PRMS subroutine. 

After PRMS distributes the precipitation excess 

and sediment production from the first minute of 

rainfall over the disturbed area, it is accumulated in 

the four classes of rills and gullies in proportion to 

the direct drainage areas listed in table 1. The depth 

of water in each class of channel is calculated and an 

equation for open-channel flow is used to compute 

the velocity of water. The velocity is multiplied by 

the depth and width and by the number of outlets to 

determine the water discharge from each class of 

rills and gullies. Sediment deposition in each class of 

channel is calculated on the basis of the particle 

settling velocity of the sediment and the depth of 

water in the channel. Sediment deposition in each 

class of channel is subtracted from the original 
TABLE 1.-lnforrnation on rills and gullies used in PRMS subroutine 

Class Direct Total 

rill drainage drainage Channel 

or area area area gully (ft2) (ft2) (ft2) 

1 25,000 25,000 7,500 

2 16,000 41,000 5,000 

3 2,000 43,000 320 

4 871 43,560 80 

amount, and the sediment remaining in suspension 

is routed with the water discharge from the channels. Sediment is routed in proportions equal to the 

water discharge: If 10 percent of the water in a rill or 

gully is discharged, then 10 percent of the sediment 

remaining in suspension is also discharged. After 

water and sediment discharge have been calculated 

for each class, the water and sediment are routed to 

the next class or to the diversion terrace. 

The diversion terrace is divided into four equal 

segments, each receiving 25 percent of the water and 

sediment discharge from the mined area. Water and 

sediment are routed through the four segments of 

the diversion terrace: segment 1 discharges to segment 2, segment 2 to 3, segment 3 to 4, and segment 

4 discharges from the mine site. The water discharge 

and suspended-sediment concentrations from segment 4 are plotted at !-minute intervals. 

Water and sediment-discharge hydrographs can 

be computed for a storm of 24 hours or less in duration. The results for one storm are shown on figure 1. 

Rainfall during the storm was 1.20 in., and the precipitation excess was 0. 90 in. The measured sediment discharge was 0.58 ton, and the sediment 

discharge calculated by the model was 0. 75 ton. The 

measured and calculated water discharges were both 

about 4,300 ft3. 

Number Width 

of of each Channel 

outlets outlet discharges 

per acre (ft) to 

275 0.5 Class 2 rills 

50 1.0 Class 3 rills 

tl 1.5 Class 4 rills 

4 2.0 Diversion terrace 

REFERENCES CITED 

Green, W. H., and Ampt, G. A., 1911, Studies on soil physics; I. 

Flow of air and water through soils: Journal of Agricultural 

Research, v. 4, p. 1-24. 

Leavesley, G. H., Lichty, R. W., Troutman, B. M., and Saindon, 

L. G., 1983, Precipitation-runoff model system: User's manual, U.S. Geological Survey Water-Resources Investigations Report 83-4238, 207 p. 

0 

z oo 

z~ <{IJ) 

. a: 0.75 !llw 

~11. 

Uf-

~l!j 

z"-

-u 

~~ w u 0.50 Uz Xw • zw 

_a: oC!l 

f-<1: 

<I: :I: f-U 

ii:!!! u 0 0.25 Wa; 

a:w 

ll.f-<1: 

~ 

TIME, IN MINUTES 

;i 

0 

24,000~ 

~ffi 

~!:: U-' 

Za: 

Ow 

un. 

f-!/l 

16.000 ~ ~ ::Ea: 

CiQ 

W-' 

!ll::! 

o::E 

~~ z 

~ !/) 

:::> 

!/) 

FIGURE 1.-Water discharge and suspended-sediment concentration hydrographs computed by PRMS. 

Preliminary Investigation of the Physical Basis 

of Soil Erosion Parameters in the 

Precipitation-Runoff Modeling System (PRMS) 

By William P. Carey and Andrew Simon 

Simulation of upland soil erosion by PRMS currently requires the user to estimate two rainfall 

detachment parameters and three hydraulic detachment parameters. One of the rainfall parameters (a 

coefficient) and all three of the hydraulic parameters 

are directly related to the erosion properties of the 

3 

surface material. The remaining rainfall parameter 

(an exponent) is related to the damping effect of 

surface-water depth on raindrop impact. 

At present these five parameters must be estimated by calibrating simulated results with 

observed data collected either on small upland plots 
or at a downstream gaging station. Neither method 

provides a physical basis for estimating or transferring parameters. In order to provide a starting point 

for further research on the physical basis of these 

parameters, a preliminary assessment of the status 

of modeling of upland soil erosion is being conducted. 

Although progress has been slow in relating measurable soil parameters to rainfall detachment, studies by Meyer and Harmon (1979) and Meyer (1981) 

have shown that a portable rainfall simulator can be 

used to evaluate the coefficient in the rainfall detachment equation. Various intensities of rainfall are 

applied to a soil under the same cover conditions. 

The relation between erosion rate and intensity is 

generally log-linear, and thus the coefficient in the 

rainfall detachment equation can be determined. 

The ratio of the coefficients quantifies the relative 

erodibility of different soils or the relative erosion 

from different cover conditions for a given soil. 

A value for the exponent in the rainfall detachment equation is difficult to choose because it 

depends on the ratio of surface-water depth to raindrop diameter. A reformulation of the rainfall 

detachment equation based on the work of Mutchler 

and Larson (1971) would provide a damping term 

that would not require a user-supplied parameter. 

The three hydraulic detachment parameters consist of one exponent and two coefficients. Foster and 

Meyer (1972) stated that if the bed shear stress is 

large compared to critical shear stress, then the 

initial value of the exponent can be set at 1.5. The two 

coefficients in the hydraulic detachment equation 

are functions of the soil's resistance to erosion by 

flow. Research into the relation between these coefficients and measurable soil properties has not 

yielded results that can be easily applied in a modeling study. Most studies of cohesive material have 

focused on the relation between critical tractive 

force and soil properties; however, Ariathurai and 

Arulanandan (1978) successfully correlated cation 

exchange capacity and sodium adsorption ratio with 

an erosion rate coefficient. 

We cannot yet make recommendations concerning 

methods to evaluate the hydraulic detachment 

coefficients in PRMS. Further research is needed on 

the relations between these model parameters and 

soil properties and on the general applicability of the 

methods developed primarily for agricultural 

applications. 

REFERENCES CITED 

Ariathurai, R., and Arulanandan, K., 1978, Erosion rates of 

cohesive soils: Journal of the Hydraulics Division, American 

Society of Civil Engineers, v. 104, no. 2, p. 279-283. 

Foster, G. R., and Meyer, L. D., 1972, Mathematical simulation of 

upland erosion by fundamental erosion mechanics, in Present and prospective technology for predicting sediment 

yields and sources: Proceedings of the Sediment Yield 

Workshop, Oxford, Mississippi: U.S. Department of Agriculture, p. 190-207. 

Meyer, L. D., 1981, How rain intensity affects interrill erosion: 

Transactions of the· American Society of Agricultural Engineers, v. 24, no. 6, p. 1472-1475. 

Meyer, L. D., and Harmon, W. C., 1979, Multiple-intensity rainfall simulator for erosion research on row sideslopes: Transactions of the American Society of Agricultural Engineers, 

v. 22, no. 1, p. 101-103. 

Mutchler, C. K., and Larson, C. L., 1971, Splash amounts from 

waterdrop impact on a smooth surface: Water Resources 

Research, v. 7, no. 1, p. 195--200. 

Reducing Sediment Sampling Frequency at Streamflow Gaging Station 

Rio Grande at Otowi Bridge near San lldefonso, New Mexico 

By David H. Marshall 

Suspended-sediment samples currently are collected daily at 16 stations that are operated by the 

New Mexico District of the U.S. Geological Survey. 

Less frequent sampling would reduce costs for the 

existing network and would free resources to expand 

the data-collection network. The purpose of this project is: (1) to develop and test a technique to estimate 

4 

daily suspended-sediment concentration using records of discharge, climate, and suspended-sediment 

concentration; (2) to determine the best sampling 

schedule that, when coupled with the estimation 

technique, would provide accurate estimates of daily 

suspended-sediment concentration and yearly total 

suspended-sediment load; and (3) to estimate the 
number of years of daily records necessary to define 

the relation of suspended-sediment concentration to 

water discharge at a particular station. 

Study of the conditions at the Rio Grande at Otowi 

Bridge began with an analysis of trend in the yearly 

mean suspended-sediment concentration. A doublemass curve was used to determine when a change 

took place in the relation between suspended-sediment discharge and water discharge. The graph of 

cumulative annual water discharge versus 

cumulative annual suspended-sediment load showed 

a linear relation with obvious breaks in slope. 

Annual mean concentrations were grouped for years 

when the double-mass curve had a constant slope, 

and the Kruskal-Wallis test (Canover, 1971) was performed to see if the groups were similar. The test 

showed that the groups differed at the 99-percent 

significance level, so the data were selected from the 

most current group having a constant slope, 1973 to 

present. 

The model developed to predict daily suspendedsediment concentration contains both a deterministic and a probabilistic component. The deterministic component estimates the increase in 

suspended-sediment concentration caused by a rising stage or precipitation. The probabilistic component estimates the decline of suspended-sediment 

concentration after an increase, given the cause of 

the increase and the suspended-sediment concentration the day of the increase. 

Flow on the Rio Grande follows a yearly cycle. 

Spring runoff from snowmelt begins in April, peaks 

in June, and ends in late July or early August. Flow 

in July through September typically has very rapid 

increases and declines from intense, short-duration 

thundershowers. Releases from Abiquiu Reservoir 

cause rapid increases in stage followed by sustained 

flow. The plot of daily suspended-sediment concentration versus discharge formed a hysteresis loop 

in which concentration was higher on the rising 

stage of spring runoff than on the falling stage (for 

the same discharge). The discharge-concentration 

hysteresis loop and the hysteresis loop formed by 

Froude number and discharge appeared to be very 

similar. The relation of the Froude number to suspended-sediment concentration is used in both the 

deterministic and probabilistic components of the 

model. 

The deterministic component uses rainfall data 

from five rain-gage stations in the basin and the 

velocity and hydraulic depth calculated from discharge records from the Rio Grande at Otowi 

5 

Bridge. Rainfall depths were grouped according to 

the travel time the rainfall runoff needed to reach 

Otowi Bridge, and the groups then were summed. 

The summed depth was correlated with the increase 

in suspended-sediment concentration, and a line was 

fitted to the data using the median of the slopes 

formed by the origin and the data points. This relation is used to estimate the increase in suspendedsediment concentration for a given rainfall depth. 

Increases caused by a rising stage were estimated by 

correlating the increase in concentration with the 

velocity squared divided by hydraulic depth, and a 

line was fitted to the data using the median slope. 

Velocity was determined by using a discharge 

weighted velocity for a rise on day n of: 

V = An ~ 1 V2n ~ 1 + (M) (D..d)g 

n An~ 1 Vn ~ 1 + (M) (gD..d)112 

where 

n = day of the rise, 

V = discharge weighted velocity, 

A = cross-sectional area, 

M = increase in cross-sectional area 

(An - An~1), 

D..d = increase in mean depth 

(dn - dn ~ 1), and 

g = acceleration of gravity. 

The velocity of the rise is assumed to be celerity 

velocity of a wave of the depth of the river. This 

undoubtedly overestimates actual velocity, but it is 

only used to separate the rises for different discharges. 

The probabilistic component is estimated using a 

Markov model (Karlin and Taylor, 1975). The Markov 

process was estimated by first grouping the suspended-sediment concentration data by the time 

since the latest increase and by the type of increase. 

Five groups were used: (1) 1 day after a 1-day storm; 

(2) 1 day after a 2-day (or longer) storm; (3) 2 or more 

days after a storm; (4) 1 day after a rise in stage; and 

(5) 2 or more days after a rise in stage. The range in 

concentration was broken into 50 intervals, or state 

spaces. The concentrations were paired for day nand 

day n + 1 and, after being grouped, were sorted by 

state spaces for day n. Only pairs where the concentration on day n + 1 was lower than day n were 

used. The mean of the concentrations for day n + 1 

for each state space was calculated. All the state 

space means were joined using an arctangent function to make the model continuous. A lower limit of 

suspended-sediment concentration was calculated 
by estimating the lowest boundary of velocity 

squared divided by hydraulic depth and measured 

concentration. This acts as an absorbing state; that 

is, once the concentration falls to this level, it will 

remain constant (for a given velocity squared/ 

hydraulic depth) until an increase takes place. 

The model is exploratory and was developed to 

determine if the technique is feasible. Many variables affecting concentration were not used, and 

actual field conditions were not properly estimated. 

To assess accuracy, the model was developed using 

data from the 1979 and 1980 water years and tested 

using data from the 1981 water year. The calculated 

yearly suspended load was 76.5 percent of the measured load, and daily extimated suspended-sediment 

concentrations were reasonably close to measured 

concentration for all days when no precipitation 

occurred. Using observations of suspended-sediment concentrations when precipitation occurred 

(138 points), the estimated yearly load was 91.8 percent of the measured load, and daily concentrations 

were very close. 

Future work on the model will be needed to better 

estimate rising stage velocity, to develop a better 

assessment of rainfall relations, and to account for 

seasonal changes. The data base will be increased 

one year at a time to observe convergence of the 

estimated parameters. Other sampling schemes will 

be studied to optimize accuracy with the fewest possible samples, and recommendations for reduced 

sampling will be developed. 

REFERENCES CITED 

Canover, W. J., 1971, Practical nonparametric statistics: New 

York, John Wiley, p. 229-237. 

Karlin, Samuel, and Thy lor, Howard M., 1975, A first course in 

stochastic process: New York, Academic Press, p. 45--116. 

Comparison of Digital Modeling Techniques which Simulate Sedimentation 

Processes in an Agricultural Watershed 

By Leslie D. Arihood 

The Precipitation-Runoff Modeling System 

(PRMS) and Areal Non point Watershed Environmental Response Simulation (ANSWERS) models 

are evaluated for their accuracy, applicability, and 

practicality in simulating water and sediment runoff 

from a midwestern agricultural watershed. The 

models' applicability and performance were analyzed 

in light of the watershed's characteristics, storm patterns, and runpff characteristics. 

Model design should be able to incorporate the 

specific characteristics of the Hooker Creek watershed, Indiana. Sediment production is mostly from 

the flood plain and areas close to the flood plain. The 

drainage network has developed in a manner such 

that runoff is rapid. The steady-state hydraulic conductivity of soil is reached within 5 minutes after 

water is pooled on the soil surface. Soils near the 

stream and soils in the uplands have different capacities to infiltrate, hold, and drain water. 

Sediment transport is influenced greatly by 

source material and rainfall intensity. About 90 percent of suspended sediment is less than 0.062 mm in 

diameter, reflecting the fine-textured soils of the 

6 

watershed. Rainfall intensity strongly influences 

suspended-sediment concentration and discharge; in 

fact, sediment discharge from storms having a similar maximum intensity can be adequately described 

by a straight-line arithmetic plot of mean daily storm 

discharge and sediment discharge. 

Differences in each model's structure and concepts 

of hydrologic processes are important in determining the model's usefulness and applicability. The 

PRMS is capable of simulating several storm and 

nonstorm periods whereas ANSWERS can simulate 

only one storm period per run. ANSWERS' grid 

system is well suited to the Hooker Creek drainage 

network. Overland flow planes can drain directly to 

adjacent overland flow planes or to the beginning of a 

stream and continue to maintain the actual watershed slope. The PRMS has a subsurface reservoir 

contributing to streamflow whereas ANSWERS can 

simulate subsurface flow only by tile drains. 

ANSWERS can simulate infiltration from surface 

pools until they dry, but PRMS simulates infiltration 

only during rainfall. 

ANSWERS' data collection is simplified by 
providing some sources for data in the documentation and by referencing sources that are easily 

obtained. Data for ANSWERS that must be collected from the watershed, such as discharge and 

rainfall, are commonly collected by Districts and do 

not require significant increases in data-collection 

expertise. 

Instrumentation 

Measurement of Suspended Sediment in Surface Waters: A Discussion of New 

Technologies That Will Operate Continuously and Unattended 

By Marvin C. Goldberg 

Timely and accurate data on particle size distributions and mass concentrations of suspended 

sediment in natural water bodies are used by the 

U.S. Geological Survey and other agencies concerned with water quality and stream hydrology. 

Obtaining this data adequately and efficiently would 

be made easier if a device were available which could 

analyze the sediments automatically and unattended 

in situ. The analyzer, ideally, would be able to 

extract the sample from the cross section and measure the particle size/mass distributions. It should 

have a range of 1 to 1, 000 micrometers in hydrodynamic size and from 50 to 500,000 parts per million 

in concentration. It should make the measurements 

accurately and reliably, without operator attention, 

for a period of at least 2 weeks. 

There are several technologies currently used for 

particle size measurements. These include sieving, 

sedimentation, gravimetry, elutriation, turbidimetry, light obscuration, electrozone measurements 

(Coulter-type sensors), doppler-shifted light scattering, acoustic echoing, holography, microscopy, Xray fluorescence, photon correlation spectroscopy, 

elastic light scattering, and attenuation of transmitted energy from a beam, where the beam can be 

visible light, X-ray, beta-ray, gamma-ray, or ultrasonic. 

Only sieving, visible light beam attenuation, single-particle obscuration of a light beam, electrozone 

devices, and back-angle light scattering can measure 

sizes over the range desired. Of these, the singleparticle obscuration and electozone methods require 

many sensors operating in parallel and, in both 

7 

cases, each sensor contains a small orifice through 

which the particles must flow. Adding a way to automatically unclog the orifices introduces a degree of 

complexity which is undesirable in a field-sited particle sensor. Automatic sieving instruments are 

mechanically quite complicated, and for long-term 

reliability, electronic complexity is preferable to 

mechanical. 

The techniques remaining are light-beam attenuation and light scattering. Of these two methods, light 

scattering has the advantages of being relatively 

insensitive to large concentration changes and being 

easy to combine with depolarization measurements, 

for extending the low end of the size range. 

The U.S. Geological Survey uses hydrodynamic 

sizes as a size parameter. Few methods can accurately measure both size and mass in a single measurement, thus mass is commonly approximated by 

multiplying an average density (2.65 g/cm3 ) times 

the determined volume of the particle. Light-beam 

attenuation and light scattering techniques can be 

combined with sedimentation procedures to provide 

a hydrodynamic size measurement. A particle-sizing 

instrument developed in our laboratory, incorporating right-angle scattering, depolarization ratios, and 

back-angle scattering, has demonstrated better resolution in the small size range with smaller samples 

than gravimetric sedimentation and equal 

capabilities with larger particles. The instrument is 

mechanically quite simple, produces a signal that is 

readily digitized, and is adaptable to being incorporated into a field-sited particle analyzer. 
Instrumentation for Automatically Monitoring Sediment 

Concentration and Particle Size-A Progress Report 

By James H. Ficken 

The Instrument Development Laboratory, located 

at the Gulf Coast Hydroscience Center in Mississippi, has procured several new instruments to 

evaluate their capabilities to measure suspendedsediment concentration and particle-size distribution. Two Markland Ultrasonic Suspended-Solids 

Meters have been procured to evaluate the meter's 

capability to measure suspended-sediment concentrations in the range of 5,000 to 70,000 mg/L. 

Daily sediment loads at two sites, estimated using 

the output of the Markland meters, will be compared 

to estimates made from routine daily sediment-sample analyses. 

A Dynatrol instrument (a vibrating U-tube) will 

be evaluated for its capability to measure the density 

of a water-sediment mixture at a field site. The density can be related to sediment concentration 

provided corrections are made for variations in density because of dissolved solids and temperature. 

A Markland sludge gun, an infrared transmissometer, detects and measures the absorption or 

scattering of infrared light by water-sediment mixtures. This instrument was evaluated for its ability 

to measure concentrations of sediment in water-sediment mixtures. 

A Micromeritics Sedigraph 5000D was procured 

for the particle-size analysis of sediment. Analytical 

determinations from this instrument were compared 

with determinations from the standard pipet 

method pertinent to measurement accuracy and 

analytical costs. 

The Instrument Development Laboratory at the 

Hydrologic Instrumentation Facility is working with 

districts and the Interagency Sedimentation Project 

to evaluate the instrumentation mentioned above. 

Reports will be given by the following individuals: 

1. Bill Matthes of the Iowa District will report on 

the work they are doing with the Micromeritics 

Sedigraph. 

2. Dave Marshall of the New Mexico District will 

report on their progress to date on operating 

the Markland Ultrasonic Suspended-Solids 

Meter. [Not included in this report] 

3. Dallas Childers of the Vancouver, Washington, 

Subdistrict will report on their application of 

the Markland Ultrasonic Suspended-Solids 

Meter. [Not induded in this report] 

4. Gerry Goddard of the Wisconsin District will 

discuss characteristics of the site at which the 

Dynatrol is planned to be installed. 

5. John Skinner of the Federal Interagency Sedimentation Project will discuss the Dynatrol. 

Progress Report on Testing of the Sedigraph Particle Size Analyzer 

By Bill Matthes 

A Sedigraph model 5000D, manufactured by 

Micromeritics Instrument Corporation, was 

assigned to the Iowa District for testing the potential of the unit as an alternative to the pipet method. 

The Sedigraph measures the sedimentation rate of 

particles, dispersed in a liquid, that range in size 

from 1 to 100 J.Lm. The instrument determines, by 

means of a finely collimated beam of X-rays, the 

concentration of particles remaining at decreasing 

8 

sedimentation depths as a function of time. Analysis 

time is reduced by continuously moving the sedimentation cell so that the effective sedimentation 

depth is inversely related to the elapsed time. A 

built-in solid-state computer solves Stoke's law and 

synchronizes the cell movement with the equivalent 

spherical diameter on the x-axis of the recorder, 

corresponding to the elapsed time and instantaneous 

depth. The logarithm of the difference in transmit-
ted X -ray intensity is electronically generated, 

scaled, and plotted linearly as a "cumulative mass 

percent" on the y-axis. 

The experiments ·were designed to supply information on the degree of operator training, time of 

analysis, effects of varying concentration on analysis, reproducibility of results, effects of changing 

cells, and comparison of results with the pipet 

method. 

The test materials consisted of seven fluvial sediment samples from various sites around the country 

(DeLaney and Schroder, 1979). 

Operator training: The training of qualified operators for the Sedigraph is less demanding and not as 

critical as for the traditional pipet method. About 40 

hours of on-the-job training would bring operators to 

acceptable competence. 

Time comparison: Sample preparation time for 

either the pipet or Sedigraph methods is the same. 

The time of analysis per sample is 20 minutes for the 

Sedigraph and approximately 40 minutes for the 

pipet in the range of 2 to 62 J.Lm. One operator and 

one unit could analyze approximately 3,500 prepared 

samples per year. 

Effect of varying concentration: The concentration of the sample does not have to be ascertained before the analysis; rather, the sample is 

diluted until the concentration meets the operational 

limits. The effects of varying sample concentration 

were tested by starting with a very turbid solution 

and diluting with 10 mL diluted dispersing agent 

after each run. Negligible differences were noted 

between runs. 

Reproducibility: A minimum of two analyses were 

obtained on each sample, and nearly identical results 

were obtained on most samples with as many as 

eight repetitions. 

Effect of interchanging cells: During normal operation, cell windows will have to be replaced for various reasons. Results indicated no significant differences using two different cells. 

Comparison of results: In general, the best agreement between methods was obtained for samples 

having 50 to 60 percent of the material finer than 1 

J.Lm. For samples having a more uniform distribution 

of particle sizes, the results are acceptable. The 

largest differences were noted in samples containing 

65 to 70 percent material larger than 10 J.Lm. These 

differences are significant and work is still being 

done to resolve this discrepancy. 

Choosing the Sedigraph for an alternate method 

will depend largely on its reliability, availability, 

reproducibility, and comparability with other methods. With the exception noted, the Sedigraph 

appears initially to fulfill these criteria adequately. 

REFERENCE CITED 

DeLaney, B. M., and Schroder, L. J., 1979, Preparation of reference material for particle-size analysis of silts and clays: 

U.S. Geological Survey Open-File Report 79-1590, 14 p. 

The Dynatrol Test Site, Madison, Wisconsin 

By Gerald Goddard 

The Willow Creek storm-sewer basin is located in 

the west-central part of the city of Madison, Wis. 

The gaging station was operated in cooperation with 

the City of Madison and the Dane County Regional 

Planning Commission to determine the nutrient, 

sediment, and water loadings to Lake Mendota. 

Continuous discharge and water-quality data have 

been collected since October 1973. 

Willow Creek drains an area of 3.15 mi2 , of which 

about 30 percent is impervious. The basin is primarily residential with some small areas of commercial development and is considered fully developed. 

9 

The drainage network consists of enclosed storm 

sewers of various sizes along with natural and concrete-lined open channels. 

The gaging station is located about 200 ft downstream of the storm-sewer outlet along a dredgedopen channel. The control at the station consists of a 

6-ft-wide Parshall flume installed in a broad-crested 

concrete weir. Over 9 years of record, the maximum 

observed instantaneous discharge was 754 ft3/s and 

the minimum was 0.01 ft3/s. The average discharge 

was 2.38 ft3/s. Willow Creek is very flashy in regard 

to discharge, as is typical of urban streams and 
storm sewers. The stage can change up to 4ft within 

15 to 20 minutes, which corresponds to a change in 

discharge of about 750 ft3fs. 

Suspended-sediment samples have been collected 

since October 197 4 using a U.S. PS-69 pumping 

sampler. Suspended-sediment concentrations have 

ranged from less than 10 mg/L to a maximum of 

5,450 mg/L. The maximum daily load was 319 tons. 

Annual suspended-sediment yields ranged from 80 

to 293 tons/mi2 • Rapid changes in sediment concentrations of 2,000 to 3,000 mg/L can occur within 

15 to 20 minutes. This will provide a good test of the 

response time of the Dynatrol in monitoring changing sediment concentrations. 

The Dynatrol will also be evaluated with regard to 

its response to particle size. Particle size of the suspended sediment at the gaging station is mostly in 

the silt and clay size ranges. The amount of silt size 

particles in the samples ranged from 15 to 78 percent, the clay size particles ranged from 21 to 72 

percent, and the sand size particles ranged from 1 to 

74 percent. 

The Dynatrol will be tested to see how closely it 

monitors sediment concentrations throughout a 

storm event. To check the accuracy of the Dynatrol, 

samples collected at the outlet of the unit will be 

analyzed for sediment concentration, dissolved solids, and specific conductance. Sieve analyses will 

also be made. Temperature and specific conductance 

will be recorded using a minimonitor. 

The variation in discharge and sediment concentration at this site should provide a wide variety 

of situations to evaluate the Dynatrol. Storms varying in rainfall amount and intensity are relatively 

frequent under normal conditions. This site is also 

located within one-half mile of the Wisconsin District 

Office, so close surveillance and frequent inspections 

are possible. 

Determining Sediment Concentration with a Fluid-Density Cell 

By J. V. Skinner 

The combination of a commercial density cell 

(Dynatrol) and a special electronic circuit shows considerable promise as a sediment-concentration 

meter. The cell consists of a U -shaped tube that is 

attached to an electromagnetic vibrator and a watersampling pump. As sediment particles move through 

the tube, they are forced to vibrate and thereby 

· increase the mass of the oscillating system. As the 

sediment concentration increases, the vibrational 

period also increases. 

The electronic circuit performs three functions: it 

sustains the vibration of the tube, accurately measures the vibrational period, and digitally displays 

the measurement after a preset time interval. 

The relation between concentration and vibrational period has been established in a series of laboratory tests. Results indicate that for accurate 

measurements, the period reading must be corrected for water temperature and dissolved solids. 

Monitoring Streambed Changes and Sediment Concentrations 

Using the Acoustic Velocity Meter 

By Antonius Laenen1 

Acoustic velocity metering (AVM) systems have 

been operational to0ls for the measurement of 

streamflow since 1965 (Laenen and Smith, 1982). 

These systems measure the traveltime of a sonic 

1This paper was not presented at the seminar. 

10 

pulse transmitted diagonally across a stream in both 

directions to determine stream velocity along an 

acoustic path. This paper points out some acoustic 

applications that may be useful in the measurement 

of sediment and its transport and describes our 

experiences with the AVM system. 
The measurement of stream depth by acoustic 

means is certainly not new. Fathometers, used routinely to define stream bottom profiles, use a single 

transducer to transmit an acoustic pulse to a reflecting surface (stream bottom) and then time the backscattered signal to obtain a measurement of depth. A 

sub-bottom profiler, another widely used device, is 

useful in locating well-defined surfaces beneath less 

consolidated bottom material. This device uses a 

trailing hydrophone to listen for reflected signals 

originating from a source some lateral distance away. 

An AVM system uses only the direct signal 

between transducers to define the velocity component of the moving water between. Signals are also 

reflected from the streambed, and these (if 

monitored indirectly by oscilloscope) can be used to 

measure streambed changes in the vicinity midway 

between transducers. These phenomena have been 

documented (Laenen, 1983) and verified on the Cowlitz River in Washington by oscilloscope photography. This study showed that depths measured by 

scaling signal times off oscilloscope photos were 

within 0.3 ft of sounded depths and that this point 

measure was a good index for the cross section. AVM 

systems presently used do not recognize reflected 

signals, and other signal-recognition techniques 

need to be explored before an AVM system could 

monitor reflected signals automatically. Signal-correlation analysis, yet to be tried in stream-based 

acoustic systems, is the most likely method now 

available to make measurement by acoustic reflection a viable tool. 

The measurement of sediment concentration by 

ultrasonic means is also not a new idea. Physical 

equations defining the relation of signal attenuation 

to particle size and concentration were derived in the 

early 1940s. Flammer (1962) concluded, "the [ultrasonic] method for determining sediment size and 

concentration seems adaptable to continuously 

recording and automatic field installations." 

The acoustic attenuation of signals propagated in 

the stream determines how well an AVM system will 

operate. Signal strength is affected by the particulate matter present in the acoustic media, and signal 

11 

attenuation during normal AVM operation may be a 

reasonable indicator of the relative magnitude of the 

sediment concentration along the acoustic path. 

Equations by Urick (1967) indicate that significant 

signal attenuation should occur for the frequencies 

and the path lengths used in AVM systems, enough 

attenuation to provide information regarding sediment concentration. Oscilloscope photographs of 

signals from AVM systems now in use indicate this is 

indeed so. 

To date, there has been no formal study to document the effect of sediment concentration on signal 

attenuation in existing AVM systems. Equipment 

has been designed and built to record changes in 

signal strength, and a program to explore the relation between this signal strength and sediment concentration is a reasonable approach. 

The speed at which the acoustic signal travels in 

a stream is affected by the density of the watersediment mixture. If temperature and specific 

conductance are known and density gradients do not 

bend the acoustic signal significantly, then 

relative density changes will be indicated by the 

changing traveltime of the acoustic pulse. The 

accuracy and practicality of this scheme has yet to be 

tested; however, noticeable changes in speed of 

sound and associated sediment concentrations have 

been documented. Problems in this approach include 

the derivation of a modulus of elasticity value for the 

water-sediment mixture. Definition of modulus 

values could entail a difficult and involved laboratory 

analysis. 

REFERENCES CITED 

Flammer, G. H., 1962, Ultrasonic measurement of suspended 

sediment: U.S. Geological Survey Bulletin 1141-A, 48 p. 

Laenen, Antonius, 1983, Measuring water surface and streambed 

elevation changes with the acoustic measuring system: 

American Geophysical Union, Water Resources Research, 

v. 19, no. 5, p. 1317-1322. 

Laenen, A., and Smith, W., 1982, Acoustic systems for the measurement of streamflow: U.S. Geological Survey Water-Supply Paper 2213, 26 p. 

Urick, R. J., 1967, Principles of underwater sound [2d edition]: 

New York, McGraw-Hill, 384 p. 
Mud and Debris Flows 

Geobotanical Evidence of Debris Flows on Mount Shasta, California 

By Cliff R. Hupp and W. R. Osterkamp 

Geobotanical data, including increment cores and 

cross sections from trees growing on and near 

debris-flow deposits, were collected in the vicinity of 

Mount Shasta, California, during July of 1982 and 

1983. Evidence of debris flows is common in the 

valley sections along most streams draining Mount 

Shasta, especially those which head at an alpine 

glacier. This evidence usually appears as depositional terraces at levels above the present stream 

channel. In some cases, past debris flows have 

degraded the valley section and were deposited further downstream. 

Debris flows destroy or damage the vegetation in 

or near their paths, but nearly all surfaces created 

by debris flows now sustain reestablished woody 

vegetation. Recent surfaces along six streams have 

been dated dendrochronologically to provide magnitude and frequency information of debris-flow 

activity in the vicinity of Mount Shasta. Floods and 

debris flows can have various effects on woody vegetation, including partly felling trees, scarring stems, 

and creating bare areas where seedlings can become 

established. The effects are recorded in the wood, 

and the age of the geomorphic event is measured in 

years by the annual growth increments. 

Trees that survive a debris flow provide highly 

accurate dates. Effects of a debris flow are manifested in several ways, usually as deformation of the 

stem or wood anatomy. These deformations are of 

four basic types (fig. 2): (1) eccentric annual growth, 

(2) suppression and release sequences, (3) adventitious sprouting along the parent trunk, and (4) 

corrasion of the stems by debris transported in the 

debris flow. The analysis of cross-dated cores and 

cross sections of stems bearing one or more of these 

deformations ultimately yields a date for a particular 

event. All of these lines of evidence were employed 

for debris-flow dating at Mount Shasta. In areas 

where a debris flow removed vegetation, a minimum 

age was obtained by dating the reestablished trees. 

Often the age structure of the tree stands on ter12 

races indicated that the trees began growing shortly 

after the deposition. 

Whitney-Bolam, Ash, and Mud Creeks were the 

most intensively studied drainages (fig. 3). Study 

sites were selected to facilitate determination of the 

down-valley extent of any particular debris flow. 

Field routine consisted of: (1) determination of depositional terraces, through ground traverses, 

topographic maps, and aerial photography; (2) 

removal of increment cores, cross sections, and 

wedges from trees growing on or near the debrisflow terraces using increment borers and hand saws; 

and (3) analysis of wood samples for age and ring 

pattern. 

Trees selected for dendrochronological analysis 

were either growing on a terrace with their root flare 

indicating germination after surface deposition or 

bore obvious deformation indicative of debris-flow 

damage, or both. 

Detailed field notes were taken which described 

the character and location of debris-flow terraces, 

the location and type of botanical evidence for each 

tree sampled, and field date of the debris flow (when 

possible). About 425 trees were analyzed. Results of 

tree-ring analyses are summarized in tables 2, 3, 

and 4. 

Most dendrochronologically datable debris-flow 

terraces occur relatively low in the valley section. 

Usually two or three terraces were found below the 

major stream incisement at all sampling sites. An 

example of this is shown in figure 4, a representative 

cross section of Ash Creek. As a rule, recent small 

debris flows were identified at high elevations on the 

mountain or low in the valley section; large debris 

flows were usually identified at low elevations or high 

in the valley section (fig. 4). Evidence of old small 

debris flows is rare, probably owing to the likelihood 

of being washed out by subsequent larger debris 

flows. Much evidence suggests cyclic scour and fill 

sequences along given reaches. Recent debris flows 

which can be traced downvalley indicate a fining of 
D 

FIGURE 2.-Types of botanical evidence of debris flow. A, Eccentric growth after tilting. B, Tree cored for minimum age. C, Release 

after passage of debris flow. D, Scar and callus growth after corrosion of stem by debris flow. 

the clasts downslope, from very coarse lahars to 

hyperconcentrated floods. 

Tree-ring dating was useful for dating surfaces as 

old as 500 years. However, considerable geomorphic 

and stratigraphic data indicate many debris flows 

that are much older. These data have not been thoroughly analyzed yet, but the literature has shown 

that a widespread pyroclastic deposit is about 9,200 

years old. This deposit is distinctive and was used as 

a marker bed for relative ages of older deposits and 

as an indicator of areas with no recent debris-flow 

activity. Exposures of debris-flow stratigraphy, 

especially in cut banks, indicate periodic large 

13 

events both before and since the pyroclastic deposit. 

The unsorted to reverse grading which may be typical of debris-flow deposits can be seen in these 

exposures. 

Recent and ancient debris flows on Mount Shasta 

represent a major surficial geomorphic agent. These 

flows, along streams and down valleys, may be the 

most significant geomorphic process; they have contributed to the formation of large alluvial fans. 

Dendrochronologic and stratigraphic analyses may 

allow for estimation of the magnitude and frequency 

of debris flows on Mount Shasta. 
4JD30i-' ______________ __.:1~22;,...1~5_' -------r------------------; 

i:::.~~ 

~ 

CAUFORNIA 

I I 

I I I 

5 MILES 

I 

5 KILOMETERS 

FIGURE 3.-Study areas (sites 1-12, see tables 2--4) on Mount Shasta, Calif. 

14 
TABLE 2.-Sumrnary of debris flow dates at sites on Whitney 

Creek and Bolam Creek, Calif. 

Event a Upper Whitney Bolam Whitney Creek Whitney Creek on 

Creek Creek below US 97 Juniper Flats 

(1) (2) (3) (4) 

A 1974 

B 1;~2b c 1952c 

1;;5c,d 

1952 

D 1935 1935b 1935c,d 

E 1924 

F 1840 1840c 

G 1790 

H 1670 1670c 

aA, Tree age, ring anomalies; B, tree age; C, tree age, corrasion 

scar; D, tree age, ring anomalies, corrasion scars; E, corrasion scars; 

F, 5ree age, ring anomalies, corrasion scars; G, tree age; H, tree age. 

Probably a flood, not a debris flow. 

~Site of major deposition for event. 

Event 

A 

B 

c 

D 

E 

F 

Historically documented. 

TABLE 3.-Summary of debris flow dates on Mud Creek, Calif 

Event a Damsite Pipeline RD13 CA 89 

(5) (6) (7) (8) 

A 1977 1977~ B 1974 1974 1974 

c 1967c 1967c 

D 1964 1964 

E 1962 

F 

1924d 

1950 

G 1924 1924b,d 1924b,d 

H 1910 

1;;ld 1881b,d I 1881 

J 1880 1;~ob 

aA, Tree age, ring anomalies, corrasion scar; B, tree 

age, ring anomalies; C, adventitious sprouts from a flood 

(no debris flow), tree age; D, tree age; E, tree age, 

corrasion scars; F, tree age; G-H, tree age, corrasion 

scats; I, tree age, ring anomalies; J, tree age. 

Site of major deposition for event. 

~Probably a flood, not a debris flow. 

Historically documented. 

TABLE 4. -Summary of debris flow dates on Ash Creek, Calif. 

a Upper Ash Creek Military Pass Ford Old Mill Site 

(9) (10) (11) 

1977b,c 1977 

1962c 1962 1962 

1939 1939 

1900 1900c 

1800 1800 1800c 

1725 1725c 

aA, Tree age, corrasion scars; B, tree age, ring anomalies, corrasion scars; C, tree age, ring anomalies, corrasion scars; D, tree 

ageB ring anomalies; E, tree age; F, tree age. 

Historically documented. 

cSite of major deposition for event. 

15 
(Not to scale) 

FIGURE 4.-Representative cross section of Ash Creek near Military Pass, Calif. 

Downstream Dilution of Lahars from Mount St. Helens, Washington: 

Defining the Boundary Between Debris Flow and Hyperconcentrated Streamflow 

By Thomas C. Pierson and Kevin M. Scott 

Mudflows and debris flows (collectively termed 

lahars in volcanic terrain) behave as non-Newtonian 

fluids. Hyperconcentrated streamflow, on the other 

hand, is thought to behave as a Newtonian fluid. 

Although the transition from one type of fluid to the 

other has significant implications for the mechanics 

of flow and sediment transport, the sediment concentration boundary separating them has only been 

arbitrarily defined. Several lahars occurring at 

Mount St. Helens since the catastrophic eruption on 

May 18, 1980, have transformed from debris flow to 

16 

hyperconcentrated streamflow. These flows 

provided the opportunity to describe the change in 

flow properties as the boundary was crossed and to 

correlate changes in character of the deposits with 

this transition. 

An explosive eruption on March 19, 1982, caused 

nearly instantaneous melting of a large volume of 

snow in the Mount St. Helens crater. Subsequently, 

a flood of roughly 3,200 acre feet of water and hot 

volcanic ejecta cascaded down the north flank of the 

volcano, eroding and incorporating enough addi-
tional rock debris into the flow to transform it into a 

debris flow within 1.2 miles of the creater breach. 

This lahar, with an initial peak discharge estimated 

to be in excess of 490,000 ft3/s, entered the North 

Fork Toutle and flowed 17 miles downstream (moving 

in two surges) as a coherent debris-flow slurry. Flow 

velocities, computed from superelevation in bends, 

varied between 13 and 30 ft/s. Sediment concentrations of peak flow deposits were experimentally determined from reconstituted samples and 

showed a progressive downstream decrease from 

about 90 to 79 percent by weight. The deposits, 

which remained liquefied for more than a day, were 

typical of debris-flow deposits: poor sorting (sorting 

coefficient of2. 0 to 5. 0 phi units), lack of stratification 

within depositional units, matrix-supported clasts 

rather than openwork structure, and relatively low 

silt and clay contents (7 to 15 percent by weight). 

Between 17 and 25 miles downstream from the 

crater, the character of the deposits changed progressively to a lahar-run out facies, consisting of 

poorly stratified, moderately well sorted (sorting 

coefficient of 1.1 to 1. 6 phi units) beds of noncohesive, 

openwork sand (predominantly coarse) with occasionallenses ofpumire gravel. These beds commonly 

exhibited both normal and reverse grading. At four 

gaging and observation stations located 30, 36, 45, 

and 50 miles downstream, observers noted that the 

flow was no longer a coherent slurry, but rather sand 

suspended in muddy water-hyperconcentrated 

streamflow. Grab samples, observed deposition of 

coarse sand (deposits drained immediately), and formation of 8-ft-high standing waves confirmed a 

change in fluid properties. Progressive downstream 

changes at peak flow were observed (with respect to 

stations mentioned above) in suspended-sediment 

concentration (not measured, 71, 67, and 61 percent 

by weight), discharge (34,000, not measured, 23,000, 

and 16,000 ft3/s), and temperature (16.5, not measured, 12.5, and 10.8°C). Mean velocity did not 

change significantly but remained between 13 and 20 

ft/s. The sedimentology and stratigraphy of deposits 

from the May 18, 1980, South Fork Toutle River 

lahar and deposits from several prehistoric lahars in 

the Toutle River valley show trends very similar to 

those of the March 19, 1982, deposits. 

Dilution of the debris flow by deposition of coarser 

particles and incorporation of additional water from 

the river resulted in the transition from a one-phase 

slurry (trapped pore water transported within a 

framework of particles) to a two-phase hyperconcentrated fluid (coarser particles freely suspended in a 

mixture of water and fines). For the March 19, 1982, 

lahar, this sediment concentration threshold was 

crossed at between 76 and 79 weight percent solids. 

Samples from the recessional limb of the May 18, 

1980, North Fork Toutle River Lahar indicate that 

the threshold for that lahar (mudflow) was bracketed 

between 72 and 84 weight percent solids. This 

boundary is, however, dependent on the particle-size 

distribution of the slurry. Past experimental work 

has indicated that silt- or clay-rich mixtures make 

the transition at considerably lower sediment concentrations. 

Stream Channel Adjustments to 1980 Lahars and Subsequent Stormflow, 

Mount St. Helens, Washington 

By Holly A. Martinson and David F. Meyer 

The South Fork Toutle River, flowing west from 

Mount St. Helens, and Pine Creek, flowing southeast, are two river systems altered by lahars generated during the May 18, 1980, eruption. During 

water years 1980-82, the volume of sediment eroded 

or deposited by fluvial processes has been comparable to or greater than volumes eroded or deposited at 

channel cross sections by the May 18, 1980, lahars. 

Reaches of comparable slope have adjusted similarly, although the magnitude of storage changes 

17 

has not been proportional to discharge, nor have 

trends or patterns of adjustments persisted through 

time. These large-scale changes reflect the response 

of disturbed channels to the statistically large 

streamflows that have occurred since the eruption. 

The largest changes in sediment storage occurred 

during water year 1981 at all measured sections, in 

part due to ubiquitous lateral instability and pervasive widening by channels by 30 feet or more 

during water year 1981 (fig. 5). The additional down-
~ 

w 

w 

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~ 

z 

0 

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w 

~ 

w 

w 

u.. 

~ 

z 

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EXPLANATION 

~ Aggradation and widening 

~ Downcutting and widening 

\I Downcutting, no widening 

SOUTH FORK 

TOUTLE 

DISTANCE, IN FEET X 103 

FIGURE 5.-Dominant fluvial processes, Pine Creek and South Fork Toutle River, 1980-81. 

I 

I EXPLANATION 

6. Aggradation, no widening 

~ Aggradation and widening 

\I Downcutting, no widening 

fQ1 Downcutting and widening 

0 Widening 

0 No change 

SOUTH FORK 

TOUTLE 

DISTANCE, IN FEET X 1 0 3 

FIGURE 6.-Dominant fluvial processes, Pine Creek and South Fork Toutle River, 1981-82. 

18 
cutting of channel incisions in the steep, uppermost 

reaches caused a net loss of sediment from storage. 

For example, in upper Pine Creek, cross-sectional 

area at surveyed sites increased by 790 to 2,600 ft2 . 

In moderate-slope reaches, area changes of as much 

as 750 ft2 reflected net storage losses or gains. Channel aggradation dominated at these sites, but erosion 

of higher terraces and the valley walls contributed to 

a net loss of sediment in storage measured at about 

half the sites. In low-slope reaches of the South Fork 

Toutle River the channel incised, but increases in 

cross-sectional area of as much as 5,400 ft2 were 

mainly caused by increases in channel width. 

During water year 1982, changes in storage averaged one-fifth the magnitude of changes during 

water year 1981, and the pattern of response commonly was reversed (fig. 6). Eighty percent of measured cross sections in the high-slope reaches of 

upper Pine Creek filled, with a net gain in storage. 

Channels incised at 90 percent of the measured sections in moderate-slope reaches (lower Pine Creek 

and middle South Fork Toutle River), lowering the 

bed by as much as 5 feet, and causing a net loss of 

storage. Widening was negligible at Pine Creek, 

except near the mouth, but continued as a dominant 

process in the middle reaches of the South Fork 

Toutle River. The channel aggraded and widened in 

the low-slope reaches of the lower South Fork Toutle 

River. 

Therefore, high flows caused by storms of water 

year 1981 had a "first flush" effect. Subsequent discharge of comparable magnitude during water year 

1982 did not have proportional effects on the channels. At some sites, the largest changes in storage 

occurred during high flows caused by the first significant storm of water year 1981. 

Erosional Development of the North Fork Toutle River Debris Avalanche Deposit, 

Washington 

By David F. Meyer and Richard J. Janda 

In 3 years following the May 18, 1980, eruption of 

Mount St. Helens, the chaotic, hummocky topography of the massive debris avalanche deposit in the 

North Fork Toutle River has been significantly 

altered by mass wasting and fluvial processes. This 

deposit initially covered about 23 mi2 with an average of 150 feet of poorly sorted, low cohesion, primarily sand-size debris. Three major and nine minor 

tributaries were impounded by the avalanche 

deposit, and numerous closed depressions existed on 

its surface. For erosion to proceed, a through-flowing drainage had to develop. 

Erosional development of each area on the avalanche deposit involves a four-step sequence of 

events: (1) drainage integration by fill and spill of 

closed depressions (fig. 7), (2) channel incision and 

extension, (3) channel widening, and (4) alternating 

scour and fill. However, even reaches experiencing 

aggradation show a net decrease in sediment storage 

because bank erosion more than compensates for 

aggradation on the bed. These processes deliver 

annually 2-3 x 107 tons of suspended sediment and 

a large but as yet unquantified amount of bedload to 

the North Fork Toutle River. This extreme load 

19 

creates major sediment-management problems 

along the lower Toutle and Cowlitz Rivers. 

Drainage integration was initiated by lahars generated by compaction, dewatering, and possibly liquefaction of the avalanche deposit during the 

morning and afternoon of May 18, 1980. Further 

integration proceeded quickly because areas on and 

upstream from the avalanche deposit receive 60--130 

inches of precipitation annually. Surface runoff and 

ground-water seepage filled depressions, causing 

breaching and cutting of incipient channels. Breach 

flows surged downstream, sometimes as debris 

flows, until contained in larger depressions. The first 

significant discharge from the avalanche deposit to 

the North Fork Toutle River occurred on August 27, 

1980, when a 284-acre-foot lake near Elk Rock (10 

miles northwest of the crater and 5 miles upstream of 

the distal end of the avalanche) breached, generating 

a peak flow of about 16,000 ft3/s. Some breaches were 

caused by eroding away earthen impoundments 

rather than the fill-spill process. The largest breach 

of this type occurred on February 20, 1982, when the 

North Fork Toutle River breached the impoundment 

of Jackson Creek Lake, releasing about 2,000 acre-ft 
of water. In addition to natural breaches, 37.9 mi2 of 

drainage integration was brought about by constructing controlled outlets to South Fork Castle, 

Coldwater, and Spirit Lakes. Spillways were constructed at the first two lakes during summer of 

1981, and a pumping scheme was installed at Spirit 

Lake in autumn 1982. 

Streams resulting from initial drainage integration quickly eroded deep narrow channels because of 

the generally steep initial slope (0.00~.055) and 

the readily erodible character of the avalanche 

deposit. New channels commonly incised 16 feet or 

more in response to breaching flows and storm runoff 

early in water year 1981. 

During the last three quarters of water year 1981, 

marked incision occurred only upstream of Elk 

Rock. Nearly all sediment eroded from incising 

120 

(/) 

w 

::::!100 (!) ::::;! z w i= a: 

<( 80 ~ 

::l 80 a: 0 1- (/) z 

~ 0 

60 u <(- 60 z w u; a: <( <( al 

(!) LL. 

z 40 40 0 i= 1- ::l z al w a: u 1- a: z 20 20 ~ 0 

u 

WATER YEAR 

FIGURE 7.-Drainage integration, with time, of the upper North 

Fork Toutle River basin, above the N -1 debris retention structure. Vertical portions of the line represent breaching of ponds 

and lakes; heavy lines represent controlled breachings. Arrows 

represent major runoff-producing storms. 

reaches was carried through the Elk Rock reach to 

and beyond the distal end of the avalanche deposit. 

Channel widths in both incising and poised reaches 

commonly increased by about 100 percent. Bank 

erosion caused relatively dry debris slides and avalanches as well as occasional slumps, but banks generally remained steep and straight. Storm runoff 

volumes, peak discharges, and sediment delivery 

20 

were all low compared (per unit of precipitation) with 

events in water year 1982. 

Channel response on the North Fork avalanche 

deposit was quite different in water year 1982 for at 

least three reasons. First, annual precipitation and 

storm intensities were greater than in water year 

1981. Second, at least 20 mi2 of drainage area was 

gained through episodic natural integration and construction of controlled exits for Coldwater and South 

Castle Lakes. Fina1ly, an effluent ground-water 

table developed over much of the avalanche and 

greatly increased the banks' susceptibility to slumping and flowing. In some tributaries, slumping of 

saturated debris generated debris flows that were 

observed to flow for as much as 1.2 miles. Higher 

peak discharges and increased sediment delivery 

caused massive channel widening (up to 180 feet in a 

single 2-day storm). Locally, width increased to the 

point that flow depths were insufficient to transport 

imposed sediment loads. Within the Elk Rock reach, 

net changes in thalweg elevation were minimal, 

although complex cut-and-fill sequences as much as 

30 feet thick were evident following several storm 

periods. Even during periods of aggradation, channel widening in this reach eroded a greater volume of 

material than that deposited on the bed. Upstream 

and downstream of Elk Rock, large alluvial fans 

formed and considerable amounts of alluvium were 

placed in temporary storage. 

Erosional development of the avalanche deposit 

has also been influenced by volcanically generated 

debris flows, the largest of which occurred March 19, 

1982, during the initial explosive phase of a domebuilding eruption. This flow integrated drainage 

from the crater and the Pumice Plain north of the 

mountain with the North Fork Toutle River and was 

responsible for the largest peak discharge from the 

upper North Fork Toutle River since May 18, 1980. 

Although this flow caused considerable erosion and 

deposition on the avalanche, it merely accentuated 

fluvial landforms developed during the preceding 

winter storms. 

Despite these drastic changes in surface morphology, to date only about 5 percent of the original 

avalanche deposit has been eroded away. This unit is 

likely to cause persistent sediment management 

problems. 
Sediment Transport 

Erosion and Landform Modification at a Low-Level Radioactive Waste 

Disposal Facility near Sheffield, Illinois 

By John R. Gray 

Erosion and other processes of landform modification are being studied at a 20-acre low-level 

radioactive waste disposal site near Sheffield, IL. 

The primary objective of the study, along with concurrent studies on the saturated and unsaturated 

ground-water resources at the site, is to develop a 

data base on site hydrology and surface stability to 

develop criteria for future waste site selection. The 

determination of rainfall-runoff and runoff-sediment 

transport relations, and the comparison of these 

relations to those obtained from a nearby 

undisturbed basin, are specific study objectives. 

Runoff and sediment discharges are monitored in 

three watersheds comprising two-thirds of the site 

area, and in a 2. 7 -acre watershed in undisturbed 

terrain 0.3 mi south of the site. The effects of slope 

and land use on infiltration, runoff, and sediment 

yield are being evaluated at four plots ranging in size 

from 110 to 118 ft2 , two on the site and two on the 

undisturbed watershed. Three tipping-bucket and 

one weighing rain gage record the amount and intensity of precipitation. A micrometeorological station 

collects data for computing evapotranspiration. 

Land-surface altitudes are measured periodically at 

fixed locations onsite to quantify settling and compaction of fill materials. Photographs are taken 

periodically from reference points to allow visual 

comparison of vegetative and surficial changes over 

time. Surveys of ground-cover density are also made 

as one variable affecting the relation between rainfall and runoff. 

Preliminary results indicate that 34.6 inches of 

precipitation from July 1, 1982, through June 30, 

1983, produced 9.1 in. of runoff from the site, compared to 2. 0 in. of runoff from the undisturbed watershed. Evapotranspiration was computed to be 24.0 

in. at the site for this period. The balance of 1.5 in. of 

water infiltrated the subsurface. Peak sediment concentrations of 54,000 milligrams per liter (mg/L) 

were measured in 1982 compared to 30,000 mg/L in 

1981. The reduced concentrations came after erosion 

21 

control measures were implemented and a 75-percent vegetative cover was established on the site. 

Site sediment yields are still significantly greater 

than yields from the undisturbed watershed. A 0. 7-

in. rain on July 21, 1982, for example, caused 0.4 ton 

of sediment per acre to be transported from a 3.26-

acre area of the site, whereas no runoff resulted from 

the same storm at the undisturbed watershed. Analyses of samples for particle-size distributions show 

that silt- and clay-size particles make up over 95 

percent of the sediment load in the site. Slope 

appears to be a significant factor in the relation of 

rainfall to runoff and sediment transport in the 

undisturbed watershed. However, storm sediment 

yields obtained from plots of different slope on the 

site suggest that the rainfall-to-runoff and runoff-tosediment transport relations are less dependent on 

slope than on other factors, such as soil composition 

and compaction or antecedent soil moisture conditions. Significant differences in runoff between plots 

and larger gaged watersheds have been observed; a 

1.3-in. rain on June 29, 1983, induced 0.16 in. of 

runoff from the combined gaged site area compared 

to 0.01 in. of runoff from a site plot with a 14-percent 

slope. Measurements of sediment deposited in an 84-

ft3 stilling basin downstream from a gage indicate 

that less than 3 percent of total storm sediment 

discharge is retained in the stilling basin. 

More than 110 collapse holes formed on the site 

from December 1978 through December 1982. 

Although most collapse holes were less than 10 ft in 

diameter, two exceeded 20 ft in width, and one was 

estimated to be 16 ft deep. Over 70 percent of the 

holes formed along the edges of waste-disposal 

trenches. 

A modified bubble gage measures stage at one 

station. The device uses a gas purge system to transmit the hydrostatic pressure over an orifice anchored 

in the hub of a crest-stage gage to a differential-port 

pressure transducer. The transducer attenuates a 

regulated voltage from a battery as a function of 
pressure differential between its sensing port and 

atmospheric pressure at its reference port. The voltage is recorded and converted to engineering units of 

stage by a data logger. 

A dekaport divisor system was developed to 

obtain reliable data on runoff and sediment yields 

from plots (fig. 8). The system pumps runoff from a 

5.3-gallon primary collecting vessel through a 10-

port cone splitter housing, a subunit of a USGS cone 

splitter. The cone splitter housing divides pumpage 

into 10 equal parts. Discharge from one port is 

retained in a 55-gallon auxiliary collecting vessel for 

volumetric measurements and sample collection. 

Estimating Long-Term Sediment Discharge-Which Method to Use? 

By Thomas H. Yorke 

The accuracy of various methods for estimating 

long-term suspended-sediment discharge was evaluated by comparing the discharge measured at a longterm daily sediment station with the discharge estimated by 16 different methods. The flow-duration, 

suspended-sediment transport curve procedure 

(Miller, 1951; Colby, 1956) was used as the basis for 

all the methods; the differences between the methods were the types of curves, the dependent variable, and how the curves were plotted. The types of 

curves included a single annual curve, two seasonal 

curves (dormant and growing seasons), and three 

size-fraction curves (sand, silt, and clay). Relations 

between sediment concentration, sediment discharge, and water discharge were developed for each 

type of curve. The curves were computed as straight 

lines by a least-squares regression and hand drawn 

through average sediment-concentration or sediment-discharge values within specified water discharge intervals. 

Daily suspended-sediment discharge records for 

the Schuylkill River at Manayunk, Penn., were used 

as the base information for the analyses. The river 

drains 1,810 mi2 and traverses three physiographic 

provinces. Land uses range from anthracite mining 

in forested mountains in the headwaters to extensive 

agriculture and industrial cities in the middle and 

lower basin. More than 9. 9 million tons of suspended 

sediment was discharged by the river from 1954 to 

1979; annual sediment discharges ranged from 

107,000 tons in 1966 to 996,000 tons in 1972. The 

sediment was 6 percent sand size, 54 percent silt 

size, and 40 percent clay size particles. 

Major floods have a significant effect on the longterm sediment-discharge characteristics of the 

river; the highest annual sediment discharges from 

22 

1954 to 1979 occurred in 1955 and 1972, when floods 

generated by Hurricanes Connie and Diane in 1955 

and Hurricane Agnes in 1972 transported most of 

the annual sediment load. During the 26-year 

period, 25 percent of suspended-sediment discharge 

was transported in 11 days or 0.12 percent of the 

time; 50 percent was transported in 56 days or 0.59 

percent of the time. 

Only the 86 samples collected for particle-size 

determinations from 1954 to 1979 were used in the 

analyses. The water discharge at that time of sampling ranged from 1,800 to 73,600 ft3/s. The correlation coefficient and standard error of estimate of the 

relations between water discharge and concentrations of sediment, sand size, silt size, and clay 

size particles are indicated in table 5. Generally, the 

relations between sediment and water discharge and 

clay size particles and water discharge are better 

(lower standard error) than the relations between 

sand size particles and water discharge and silt size 

particles and water discharge. Also, the growingseason relations are as good as or better than either 

the dormant-season or annual relations. 

The average annual suspended-sediment discharge estimated by the 16 different methods ranged 

from 395,000 to 499,000 t/yr (table 6) compared to 

the measured average discharge of382,000 t/yr. The 

mean discharge estimated by the 16 methods was 

432,000 t/yr and the standard deviation was 29,000 

t/yr. The mean for the eight regression methods was 

452,000 t/yr and the mean for the eight group-average methods was 412,000 t/yr; the standard deviations were 26,000 and 14,000 t/yr, respectively. 

The positive bias of the estimates probably is 

caused by the use of only samples collected for particle-size determinations. These samples normally 
FROM 

PUMP\ 

DISCHARGE HOSE TO 

TEN-PORT CONE-SPLITTER 

GAGE SHELTER 

TEN-PORT 

CONE-SPLITTER 

AUXILIARY 

COLLECTING 

VESSEL 

SAMPLE TUBE 

SECONDARY 

COLLECTING 

VESSEL 

EX 

PORT 

PRIMARY COLLECTING VESSEL 

FIGURE 8.-Dekaport divisor system. 

23 

INTAKE PORT 

(CONNECT TO 

HOSE FROM PUMP) 
TABLE 5.-Correlation coefficients and standard errors of estimate of relations 

between the logarithms of water discharge and concentrations of sediment, sand 

size, silt size, and clay size particles in suspension for the Schuylkill River at 

Manayunk, Penn. 

Growing season sediment 

sand size 

silt size 

clay size 

Dormant season sediment 

sand size 

silt size 

clay size 

Annual sediment 

sand size 

silt size 

clay size 

were collected only when the concentrations of sediment were high. Expanding the data set to include 

water and sediment discharges for each October 15 

and April 15 in the 26-year period improved the 

accuracy of the estimated discharges appreciably. 

Long-term discharges estimated with relations 

between sediment discharge and water discharge 

were 345,000 and 391,000 t/yr for the regression and 

group-average techniques, respectively. These estimates were within -9.7 percent and + 2.5 percent 

of the long-term measured discharge, respectively. 

The analyses indicate that the following generalizations apply to estimating long-term sediment 

discharge for the Schuylkill River at Manayunk: (1) a 

single relation between suspended-sediment concentration or discharge and water discharge 

provides as good an estimate of long-term sediment 

discharge as individual relations for sand, silt, or 

Standard error 

Correlation of estimate 

coefficient (log units) 

0.85 0.22 

.87 .31 

.85 .26 

.73 -26 

.75 .26 

.84 .31 

.66 .32 

.75 .26 

.79 .25 

.85 .31 

.74 .30 

.74 .26 

clay size particles; (2) two seasonal relations 

between sediment concentration or discharge and 

water discharge provide a better estimate than a 

single annual curve; (3) curves hand drawn through 

average values of sediment concentration or discharge provide better estimates than straight lines 

computed by least-squares regression; and ( 4) relations between sediment concentration and water discharge provide a better estimate than relations 

between sediment discharge and water discharge. 

REFERENCES CITED 

Colby, B. R., 1956, Relationship of sediment discharge to streamflow: U.S. Geological Survey Open-File Report, 170 p. 

Miller, C. R., 1951, Analysis of flow-duration, sediment-rating 

curve methods of computing sediment yield: U.S. Department of the Interior, Bureau of Reclamation, 55 p. 

Sediment Budget of the Tidal Potomac River and Estuary, Water Years 1979-81 

By R. Edward Hickman and James P. Bennett 

Determination of the sediment budget of the tidal 

Potomac River and estuary involved two different 

types of studies: (1) the calculation of the loads entering from upland sources and shore erosion, and (2) 

the calculation of the amounts of sediment transported through the tidal Potomac River and estuary 

and passing between the tidal Potomac and the 

24 

Chesapeake Bay. Loads from the upper Potomac 

River basin, entering the tidal Potomac Chain 

Bridge, were calculated using standard U.S. Geological Survey methods. Although loads from shore 

erosion are included, their determination is not 

discussed. 

The loads from the local nonpoint sources are 
TABLE 6.-M easured and estimated suspended-sediment discharges of the Schuylkill River 

at Manayunk, October 1, 1953, to September 30, 1979 

Method of determination 

Sediment 

discharge 

(tons/ day) 

Difference 

(percent) 

Measured average annual sediment discharge 

Estimated average annual sediment discharges: 

382,000 

Regressions, concentration data 

Annual curve 

Seasonal curves 

Annual particle-size curves 

Seasonal particle-size curves Regressions, sediment-discharge data 

Annual curve 

Seasonal curves 

Annual particle-size curves Seasonal particle-size curves 

480,000 

444,000 

424,000 

424,000 

445,000 

Ll42,000 

462,000 

499,000 

25.7 

16.2 

11.0 

11.0 

16.5 

15.7 

20.9 

30.6 

Group average curves, concentration data 

Annual curve LI07,000 

395,000 

418,000 

401 ,000 

b.5 

3.LI 

9.4 

5.0 

Seasonal curves 

Annual particle-size curves 

Seasonal particle-size curves 

Group average curves, sediment-discharge data 

Annual curve 432,000 

409,000 

432,000 

404,000 

13.1 

7.1 

13.1 

5.8 

Seasonal curves 

Annual particle-size curves 

Seasonal particle-size curves 

introduced by streamflow leaving the local tributary 

watersheds (those downstream of Chain Bridge) and 

by overflows of the combined sewer system of the 

District of Columbia. The loads in the sewer overflows were estimated from daily volumes of overflow 

and mean concentrations developed by other studies. The loads from local tributary watersheds were 

estimated by calculating yields from five monitored 

watersheds and applying them to the remaining 

area. Yields were calculated for four of the 

monitored watersheds (three urban and one rural) 

by developing relationships between sediment concentration and streamflow. The yields calculated for 

the urban watersheds are 50 percent or less of values 

calculated using samples collected during 1959-62. 

This decrease is due in part to the imposition of 

effective sediment controls at construction sites and 

to the construction of two multipurpose impoundments. The yield calculated for the one rural watershed is in the range of the values for the urban 

watersheds and two to three times greater than 

yields reported for other rural watersheds in this 

area. This discrepancy is probably because most of 

the samples from this watershed were collected dur25 

ing a very dry period. 

The amounts of sediment being transported 

through the tidal Potomac and between the tidal 

Potomac River and Chesapeake Bay were calculated 

using a hybrid one-layer/two-layer box model which 

was continuously calibrated using observations of 

sediment and salt concentrations made throughout 

the tidal Potomac River and estuary and in the adjacent Chesapeake Bay. Transport between model elements was determined by solving the conservation of 

mass equation using an implicit finite difference 

technique. 

Results indicate that during the 1979--81 water 

years, 7.9 million tons of sediment entered the tidal 

Potomac River and estuary from upland sources, 

and that all of this was retained in the tidal Potomac. 

The Potomac River at Chain Bridge supplied 56 percent of the incoming sediment, local nonpoint 

sources supplied 38 percent, and shoreline erosion 

supplied 6 percent. The tidal Potomac River and 

estuary also served as a sediment sink for the 

Chesapeake Bay during this period. The Chesapeake Bay contributed 13,200 tons more to the tidal 

Potomac than passed in the other direction. 
Effects of the Proposed Cooper River Rediversion on 

Sedimentation in Charleston Harbor, South Carolina 

By Glenn G. Patterson 

The rates of sedimentation and of resultant maintenance dredging in Charleston Harbor increased 

dramatically in the 1940s, following two major modifications to the harbor. One modification was deepening the navigation channels from 30 to 35 feet below 

mean low water; the other was the Santee-Cooper 

diversion project, which added an average of 15,000 

ft3/s of Santee River water to the Cooper River, 

increasing by many times the freshwater inflow to 

the harbor. The diversion brought additional sediment into the harbor and made the harbor a more 

efficient sediment trap by inducing a landward flow 

of salty water along the harbor floor. In 1966, plans 

were made to redivert most of the Santee River 

water back to its former channel, in order to reduce 

the rate of sedimentation in the harbor. 

The purpose of this investigation was to use existing information to determine the probable effectiveness of the proposed rediversion in reducing 

rates of sedimentation and maintenance dredging in 

the harbor. The approach was to estimate a sediment 

budget for the harbor and then estimate the effect of 

rediversion on the sediment budget. 

Major sources of sediment include erosion from 

the bed and banks of the upper Cooper River and 

sediment that originates in the Santee River basin 

and passes Pinopolis Dam with the diverted water. A 

number of minor sources, not directly affected by the 

diversion, contribute additional sediment. 

Between 1942 and 1953 most of the sediment that 

was dredged from the navigation channels returned 

to the harbor, resulting in a rapid rate of sedimentation on the harbor floor. Improvements in dredging 

and spoil disposal methods reduced the rate of runback of dredged sediment after 1953 to an estimated 

22 percent, but the rate of maintenance dredging has remained high (about 7 million cubic yards 

per year)-higher than can be accounted for by 

known sediment inputs. Inflow from the ocean by 

bottom currents may provide some of the additional 

sediment. 

Rediversion should reduce sediment loads in the 

Cooper River and diminish the sediment-trapping 

landward bottom current. The rate of maintenance 

dredging that will be needed following rediversion 

cannot be precisely estimated because of the uncertainties in the sediment budget, but it will probably 

be 40 to 75 percent less than the average during the 

period 1966--82. The reduction in the rate of maintenance dredging may be delayed by a decade or more 

by the need to remove previously accumulated sediment and may be partially offset by the effects of 

future channel deepening. 

Sediment Chemistry 

Determination of Lake Sedimentation Rates by Lead-21 0 and Cesium-137 

By I. C. Yang 

The natural and artificial radionuclides of 210Pb 

and 137Cs have been used widely for the determination of sedimentation rate in lakes, estuaries, and 

coastal regions. As 210Pb has a half-life of 22.26 

years, it is possible to date the sediment age up to 

150 years. The 210Pb method used for determining 

26 

sedimentation rates is based on the occurrence of 

excess 210Pb, a member of the 238U decay series. 

There is a continuous escape of 222Rn from the 

lithosphere and hydrosphere to the atmosphere, 

where it decays with a 3.8-day half-life and transforms into 210Pb through four short-lived daughters. 
The 210Pb is rapidly removed from the atmosphere 

by wet precipitation or dry fallout and provides a 

measurable flux to the earth's surface at a rate of 

approximately 3.2 to 6.5 disintegrations per minute 

per square inch per year (210Pb/in. 2/yr) depending 

on the location. From the water column, it is scavenged to the bottom sediments. There are three 

assumptions involved: (1) the influx of 210Pb to the 

sediment-water interface remains constant; (2) the 

sedimentation rate remains constant; and (3) no 

independent migration of 210Pb occurs once deposited. These assumptions have been verified by many 

authors (Koid and others, 1972; Thompson and others, 1975; Eakins and others, 1978). 

Cesium-137, with a 30-year half-life, was produced 

in the atmosphere as the result of nuclear weapon 

tests from 1952 to 1954, and more extensively in 

1963. The residence time of this nuclide in the air and 

water column is less than 1 year. Therefore, an 

appearance of 137Cs activity in the sediment column 

would indicate the onset of nuclear testing in 1952, 

and the maximum activity would correspond to the 

year 1963; activity would subsequently decrease to 

the present time. 

There are three methods used to measure 210Pb 

activity: (1) the gamma method, which is direct 

counting of sediment for the 46-ke V gamma activity 

from 210Pb by a Ge(Li) detector; (2) the beta method, 

which is separation of Pb from other radionuclides 

by ion-exchange columns, precipitation as PbCr03 , 

aging to ingrow the 210Bi daughter from 210Pb decay, 

and counting 210Bi beta particles on a low-beta gas 

proportional counter; and (3) the alpha method, which is chemical separation of 210Pb on a silver 

disk and counting 210Pb alpha particles by alpha 

spectrometer. The last two methods are capable of 

high sensitivity with gram-size samples, although 

many processing steps are involved, and a longer 

ingrowth time of daughter radioactivity is required. 

The first method is simple and fast, but less accurate 

than the others and requires large samples. 

Lake sediment cores from the Scofield Reservoir 

in Utah and the Lahontan Reservoir in Nevada have 

been dated by the 210Pb and 137Cs methods. The 

results from the Scofield Reservoir indicate that the 

top 4 in. of sediment yields excess 210Pb activity of 

30 picocuries per ounce (pCiloz) dry weight, decreasing to 7 /pCiloz at a depth of 30 in. The sedimentation 

rate was approximately 0.19 in./yr, comparable to 

the value of 0.22 in./yr obtained independently by 

the 137Cs method. The Scofield Reservoir has a bottom sediment thickness of 11.8 in., which corresponds to a lake history of approximately 60 years. 

At the Lahontan Reservoir, excess 210Pb activity 

profiles showed an inverse curve in the surface layer 

due to inverse sedimentation, probably caused by 

filter-feeding organisms. The excess 210Pb activity in 

the top 3.3 in. was 23 pCiloz and increased to 31 pCil 

oz between 3.3 and 6. 7 in. depth. Thereafter the 

activity gradually decreased to 15 pCi!oz at a depth 

of 18.5 in. The sedimentation rate was about 0.4 in./ 

yr compared to 137Cs-derived values of 0.5 in./yr. 

REFERENCES CITED 

Eakins, J. D., and Morrison, R. T., 1978, A new procedure for the 

determination of 21opb in lake and marine sediments: International Journal of Applied Radiation Isotopes, v. 29, p. 

531-536. 

Koide, M., Soutar, A., and Goldberg, E. D., 1972, Marine geochemistry with 210Pb: Earth and Planetary Science Letters, v. 14, p. 442. 

Thompson, J., Turekin, K. K., and McCaffrey, R. J., 1975, The 

accumulation of metals in and release from sediments of the 

Long Island Sound, in Cronin, L. E., ed., Estuarine 

research, vol. 1: New York, Academic Press, p. 28. 

Inorganic Partitioning in Sediments 

By Arthur J. Horowitz 

Historically, the Water Resources Division 

(WRD), as the name implies, has concentrated much 

of its water-quality efforts on the analysis of dissolved constituents. As a result, water quality tends 

to be evaluated on the basis of the kinds and concentrations of the various inorganic constituents 

found in solution. However, in most aquatic systems, 

27 

sediment (both suspended and bottom) contains 

many times the concentration of certain inorganic 

constituents than are dissolved in the water column. 

The strong association of numerous elements and 

compounds (arsenic, mercury, cadmium, lead, zinc, 

and others) with sedimentary material means that 

much of the distribution, transport, and availability 
of inorganic constituents in a given hydrologic system cannot be detected or evaluated solely through 

the sampling and analysis of water. Further, sediment can be viewed as a chemical reservoir that may, 

under certain physicochemical conditions, release 

chemicals into the water column or otherwise enter 

the food chain. Finally, several inorganic constituents can degrade or react with other constituents to 

form soluble and possibly more toxic forms (for 

example, the conversion of mercury to methyl mercury). Therefore, a comprehensive picture of water 

quality, which adequately describes the distribution, 

transport, and availability of inorganic constituents, 

requires chemical data on sediments. 

At the present time, the WRD lacks the 

capabilities, and the requisite field and laboratory 

procedures, to determine both the total (true) concentration of inorganic constituents, and their partitioning, in sediment. The term "total" means the 

actual concentration of a constituent in the sense of a 

series of analyses which yield results equal to 100 

percent and should not be confused with the term 

"totally recoverable." Partitioning involves both a 

physical and a chemical separation. The physical 

aspect refers to the analysis of various size fractions 

(such as sand, silt, clay sizes) or specific gravity 

fractions in order to ascertain constituent distribution within a particular sample and to facilitate intersample comparisons or to more readily ascertain 

spatial trends. The chemical aspect refers to the 

determination of the associations of in organics with 

other materials within a sample (such as humic 

acids, carbonates, ferromanganese oxides) and to 

the type of association (adsorption, complexation, 

substitution, and others). From these types of data, 

it may be possible to begin to identify sources and 

sinks, or the fate and possible effects of potentially 

toxic or environmentally necessary inorganic constituents. Similarly, such data will help in transport 

modeling, for estimating cycling rates, and for determining the availability of inorganics to ecological 

systems. 

A project to develop the procedures and techniques for dealing with inorganic-sediment associations has been established. Initial objectives include 

(1) adapting or developing methods for the determination of total concentrations in sediment for routine use in the WRD Central Laboratory System, (2) 

developing a size-fractionation method that does not 

alter chemistry, and selecting appropriate size 

ranges for routine analysis, (3) adapting or developing methods for inorganic-sediment chemical partitioning, and (4) providing guidelines on the use and 

interpretation of data generated by these methods. 

Transport of Suspended Sediment and Associated Chemical 

Constituents in the Lower Mississippi River, Louisiana 

By Charles R. Demas and Philip B. Curwick 

Suspended sediment transported by the lower 

Mississippi River is viewed both as a burden and an 

asset by the State of Louisiana. Sediment deposition 

and bed movement pose a constant navigational 

threat and mean millions of maintenance dollars 

spent each year on dredging. Further, diversion of 

sediment-laden Mississippi River water and sediment control measures in the Mississippi River 

Basin have accelerated the rate of erosion of the 

State's coastal wetlands and shoreline. Coastal erosion has enormous economic repercussions to the 

State by affecting offshore oil revenues and influencing the productivity of its vast nearshore fisheries. 

The State could, however, use sediment-laden Mississippi River water to maintain and reclaim coastal 

wetland area. 

28 

For this reason, the Louisiana District of the U.S. 

Geological Survey entered into a cooperative agreement with the State of Louisiana to perform a 4-year 

study to characterize suspended-sediment movement and attached chemical load of the lower Mississippi River from Tarbert Landing to Venice, La. 

(296 river miles). The specific objectives of the study 

are (1) to identify areas where suspended sediment 

and associated chemical load are deposited or resuspended with respect to variations in streamflow and 

suspended-sediment loads at the upstream boundary; (2) to determine selected chemical constituent 

loads in relation to suspended-sediment concentrations, particle size, and water discharge and 

relate them to bed sediment; and (3) to develop and 

test a one-dimensional numerical sediment trans-
port model and use it to predict sediment and chemicalloads for the study reach. 

Suspended sediment, bottom material, and 

attached chemical constituents will be sampled during several different rises in river stage during the 

course of the study. Suspended sediment will also be 

collected on a monthly basis. Instantaneous discharge measurements will be made concurrently 

with each sampling trip at selected sites. All suspended-sediment samples will be depth integrated 

at five or more equal discharge increments in a cross 

section. Suspended-sediment and water-quality 

samples will be collected using a P-63 point sampler . 

and a bag sampler. Bottom material will be collected 

with a Teflon-coated Shipek grab sampler. Data collection and site selection will be optimized with the 

aid of a numerical unsteady flow model and a onedimensional numerical sediment transport model. 

Fathometer tracings and continuous stage data will 

be collected at several sites to help calibrate the 

models. Suspended sediment and bottom material 

will be characterized according to particle size and 

associated chemical constituents. 

Suspended Sediment: Transport and Chemistry of Organic Carbon 

By E. Michael Thurman 

Suspended sediment transports 50 percent of the 

total organic carbon to the ocean, an important part 

of the global carbon cycle. Suspended or particulate 

organic carbon (SOC and POC) varies in concentration from micrograms per liter to milligrams 

per liter, depending on the type of river (Meybeck, 

1981). The concentration of suspended organic carbon follows the river continuum concept (Vannote 

and others, 1980); that is, concentrations are least in 

first- and second-order streams and increase downstream and with higher stream order. 

Suspended organic carbon consists of living biomass, detritus, and organic coatings on silt and clay. 

The importance of each of these sources varies with 

river and season. Small streams and rivers contain 

organic carbon of allochthonous origin, that is, from 

outside the riverine system. Large rivers have an 

autochthonous input from algae and aquatic organisms. The amount of autochthonous input is greatest 

in summer and fall and least in winter. 

The proportion of organic carbon in suspended 

sediment ranges from 0.5 to 40 percent. The least is 

found in rivers with greatest discharge, and the most 

is found in slow-moving rivers that drain wetlands 

and swamps. Thus, the concentration of SOC for all 

world rivers varies inversely with the concentration 

of suspended sediment (Meybeck, 1981). Because 

higher erosional rates dilute SOC and reduce primary production, SOC is less with higher suspended 

sediment; however, within a river system, SOC varies directly with suspended sediment in a log-log 

fashion (Nordin and Meade, 1981). That is, increased 

29 

discharge increases the concentration of suspended 

sediment, which increases SOC. This increased SOC 

usually peaks ahead of dissolved organic carbon and 

discharge. 

SOC has a longer residence time in rivers than 

dissolved organic carbon (DOC) has. Because sediment may exist for tens of years in streams to tens of 

thousands of years in flood plains of major rivers, 

SOC undergoes biological and chemical degradation 

over a much longer period than does DOC. The C/N 

ratio in suspended sediment is 10:1, which means 

that suspended sediment is considerably enriched in 

nitrogen compared to surrounding soils with a 25:1 

C/N ratio (Malcolm and Durum, 1976). Because suspended sediment concentrates nitrogen by ion 

exchange and also consists of coatings of living biomass, it is enriched in organic nitrogen compounds. 

This makes it a good substrate for bacteria, which 

colonize its surfaces. 

Bacteria attach themselves by pili (thread-like 

organs) and act as "microbial factories'' degrading 

organic matter aerobically in the suspended state. 

Here carbon dioxide and water are major products, 

and suspended organic carbon is converted to 

inorganic carbon. However, once sediment is deposited, oxygen may be depleted in interstitial waters. 

The bacterial community changes to anaerobic 

organisms, which convert POC to organic acids, 

methane, and carbon dioxide. This is characteristic 

of interstitial waters of sediment, where DOC 

increases to 50 to 500 mg C/L (Thurman, 1985). 

Suspended organic carbon on sediment behaves as 
an adsorbent for organic pollutants. It is well established that the percent organic carbon is a good 

prediction of equilibrium constants of organics 

(Schwarzenbach and Westall, 1981). Thus, sediment 

concentrates the least soluble of organic compounds, 

such as contaminants, and acts as a sink to store 

these contaminants in the flood plain of the river. 

REFERENCES CITED 

Malcolm, R. L., and Durum, W. H., 1976, Organic carbon and 

nitrogen concentrations and annual organic carbon load of 

six selected rivers of the United States: U.S. Geological 

Survey Water-Supply Paper 1817-F, 21 p. 

Meybeck, M., 1981, River transport of organic carbon to the 

ocean, in [Report of a workshop] Flux of organic carbon by 

rivers to the oceans: NTIS Report CONF-8009140, VC-11, 

p. 219-269. 

Nordin, C. F., and Meade, R. H., 1981, The flux of organic carbon 

to the oceans; Some hydrological considerations, in [Report 

of a workshop] Flux of organic carbon by rivers to the 

oceans: NTIS Report CONG-8009140, VC-11, p. 173-218. 

Schwarzenbach, R. P., and Westall, J., 1981, Transport of nonpolar organic compounds from surface water to groundwater; Laboratory sorption studies: Environmental Science 

and Technology, v. 15, p. 1360-1367. 

Thurman, E. M., 1985, Organic carbon in water, chapter 2 in 

Organic geochemistry of natural waters: The Hague, Martinus Nijhoff-Dr. Junk, p. 497. 

Vannote, R. L., Minshall, G. W., Cummins, K. W., Sedell, J. R., 

and Cushing, C. E., 1980, The river continuum concept: 

Canadian Journal of Fisheries and Aquatic Sciences, v. 37, 

p. 130-137. 

Channel Morphology 

Sediment Impacts from Coal Mining, Northeast Tennessee 

By WaiteR. Osterkamp, William P. Carey, and Cliff R. Hupp 

Extensive data, including water and sediment discharges, channel morphologies, bed- and bankmaterial characteristics, and botanical evidence of 

flow events, have been collected since 1981 from the 

Smoky Creek, Crabapple Creek, and Louse Creek 

basins, northeast Tennessee. Most basins of the area 

have been heavily impacted by coal-mining 

activities. 

Crabapple Creek and Louse Creek drain adjacent 

basins of 1.1 and 4.4 mi2 , respectively. By 1981 about 

7 percent of the Louse Creek basin had been disturbed by surface mining, much of it having occurred 

prior to 1971. The Crabapple Creek basin has 

remained relatively undisturbed since lumbering 

prior to World War II. Preliminary data from the 

Crabapple Creek basin indicate annual suspendedsediment yields of less than 86 t/mi2 , whereas casual 

observations suggest substantially higher yields 

from the Louse Creek basin. Marked differences 

between the two basins are also apparent in channel 

characteristics, particularly morphology. Crabapple 

Creek has a relatively stable, well-armored channel 

26ft wide that is closely lined by a mature population 

of trees and shrubs. Analyses of coal content in bank 

material for the period 1981 to 1983 averaged less 

30 

than 1 percent, suggesting little fluvial transport 

and deposition of coal. In contrast, Louse Creek has 

a 69-ft-wide anabranching channel with numerous 

gravel and cobble bars that are being stabilized by 

sycamores and alders. Most of these trees are less 

than 25 years old, and suggest stabilizing channel 

conditions following deposition of coarse material 

and channel widening during mining. Coal content of 

bank-material samples from along Louse Creek 

averages 2.3 percent. Along channels below active 

coal mining, coal content often ranges from 5 to 10 

percent. 

Smoky Creek drains a basin of about 31 mi2 . 

Upper Smoky Creek and major tributaries have 

high-gradient, subalpine channels that are generally 

either well armored or formed on bedrock. The 

stream valley is progressively more alluvial in the 

downstream direction, having bottom-land widths 

up to 820ft near the confluence of Smoky Creek with 

the New River. Extensive strip mining began in the 

basin about 1940 and has continued with varying 

intensity to the present. Since 1978 the annual suspended-sediment yield measured at Smoky Creek at 

Hembree, in the central part of the basin, has averaged about 2,280 t/mi2 • Over 90 percent of the sus-
pended sediment is in the silt-clay size range. Yield 

data from Smoky Creek above Hembree, about 2.5 

mi upstream from the Hembree gage and with a 

drainage area of 8.1 mi2 , are not available, but suspended-sediment concentrations during peak discharges appear to be greater than at Hembree. 

Channel-morphology data are being collected 

from nine monumented sections in the Smoky Creek 

basin and are supplemented with stratigraphic and 

botanical observations in the central part of the 

basin. Preliminary results indicate a general 

sequence of (1) channel widening and aggradation by 

movement of coarse bed material in the upper 

reaches of the drainage net below active mining; (2) 

eventual movement of the bed material into the 

upper and central parts of the Smoky Creek channel, 

the coarsest sizes being the least mobile; (3) incisement of recent deposits, channel narrowing, and 

reestablishment of woody vegetation along upland 

reaches following cessation of mining; and ( 4) continuing bank erosion, possible channel widening, 

aggradation, and reworking of mobile bed material 

as it is transported downstream during high-flow 

events. Upland areas above Bills Branch near 

Hembree (drainage area of 0.66 mi2), for example, 

were mined principally in 1975. Parts of Bills Branch 

channel, which was mostly cut into bedrock, apparently had substantial aggradation. Recent cross-section measurements indicate that much of the 

previously deposited debris has been incised and 

transported downstream, and degradation of 

remaining coarse alluvium is continuing. At Smoky 

Creek above Hembree, similar measurements show 

recent aggradation, presumably by deposition of 

material derived from tributary basins such as that 

of Bills Branch. Section data, stratigraphic evidence, and botanical observations at Smoky Creek at 

Hembree and along lower reaches show that in 

recent years substantial bank erosion has occurred. 

At a site 0. 6 mi. downstream from the Smoky Creek 

at Hembree gage, botanical evidence shows that flow 

events deposited 30 and 3 in. of debris, respectively, 

in 1977 and 1983 (fig. 9). During the last 25 years 

there has been at least 72 ft of lateral channel migration and accompanying bank erosion at the same 

site. 

Unit Hydraulic Geometry-An Indicator of Channel Changes 

By Rhea P. Williams 

Water-discharge and sediment-transport data collected at selected sites and surveyed river reaches in 

the western United States were used to evaluate 

hydraulic variables of the energy equation to evaluate channel changes at stream sections. The coefficients and exponents of hydraulic-geometry 

relations were based on unit discharge rather than 

on total discharge. Unit hydraulic geometry has 

greater application to defining channel changes than 

conventional analysis. The unit hydraulic-geometry 

relations were used to infer sectional competence of 

coarse-sediment discharge and expected channel 

31 

changes and to define quasi-equilibrium of nearbankfull streams. 

Results of this study suggest that long-term projections of coarse-sediment transport initially 

involved an evaluation of past hydraulic changes in 

the stream reach. Although the primary analysis 

used streamflow measurements, slope-area techniques can be used to analyze ungaged reaches. The 

methods described are applicable to a broad range of 

stream conditions and provide techniques for evaluating natural changes and cultural influence on 

stream reaches. 
C> 

a 

SMOKY CREEK 

POINT BAR SYCAMORE 

IN 1983 

0 0 

0 

FIGURE 9.-Diagram summarizing the use of botanical evidence to date recent flow events along Smoky Creek, northeast Tennessee. 

Channel Adjustment to Man-Induced Stress in West Tennessee 

By Andrew Simon and Clarence H. Robbins 

Alluvial stream channels are dynamic geomorphic 

systems that are continuously adjusting to altered 

energy inputs. In west Tennessee, channel modifications have caused drastic channel adjustments in 

32 

plan and profile. More specifically, these modifications in conjunction with land-use practices have led 

to accelerated downcutting and headward degradation, downstream aggradation, accelerated scour, 
and bank instabilities. Channel straightening creates a steepened profile and thus a heightened 

energy condition within the channel. Channel 

responses to this induced stress are, therefore, similar in type but greater in magnitude than those 

changes caused by dredging or clearing. 

Large-scale channel instabilities and adjustments 

are apparent in the Obion River and the South Fork 

Forked Deer River whereas the nonchannelized 

Hatchie River, flowing through similar deposits, 

continues to exhibit characteristics of stability. 

Channel slope, defined as the primary dependent 

variable (Mackin, 1948), proved to be a sensitive and 

descriptive parameter essential in determining 

channel adjustment. Although channel slope is generally considered to be one of the most difficult 

hydraulic variables to define, the rejuvenated fluvial 

systems of west Tennessee manifest readily measurable variations. 

Adjustments in profile to man-induced slope 

increases are described by inverse exponential functions of the basic form S = ae-bt where S is some 

function of channel slope, tis the number of years 

since the completion of channel work, and a and b are 

coefficients unique to the reach. These equations 

define response times for particular reaches or for 

entire rivers. 

The length of time required to attain some quasiequilibrium condition is a function of the magnitude 

and extent of the imposed disturbance. The adjusted 

profiles are similar to the predisturbed profile gradients where no alteration to channel length took 

place. Where channels were straightened by constructing cutoffs, slope adjustments trended toward 

a profile with lower gradients. 

REFERENCE CITED 

Mackin, J. H., 1948, Concept of the graded river: Geological 

Society of America Bulletin, v. 59, p. 463-511. 

Contrast in Stream Channel Response to Major StormsExamples from Two Mountainous Areas in California 

By K. Michael Nolan and Donna C. Marron 

Studies in two mountainous areas of California 

illustrate basic differences in the effects of major 

flood events on the morphology of stream channels. 

Widespread catastrophic storm effects in northwestern California contrast with localized stormrelated effects in the Santa Cruz Mountains of westcentral California. 

Major storms in northwestern California trigger 

widespread debris sliding along inherently unstable 

colluvial streambanks. Streamside failure is particularly widespread in this area because of positive 

feedback effects between physical processes (fig. 10). 

These effects are responsible for triggering additionallandsliding downstream of initial failure sites. 

The massive amount of colluvium deposited in these 

gravel-bed channels by landslide activity overwhelms the sediment transport capacities of channels and results in massive channel aggradation and 

major increases in channel width throughout entire 

drainage basins. The effects of these large volumes 

of colluvium on channel geometry are exacerbated 

33 

by persistent mass movement processes, such as 

creep and earthflow, that supply sediment to highorder channel on an annual basis. Widespread channel changes resulting from recent storms in northwestern California have lasted for decades and may 

last for decades longer. 

In contrast, major channel changes associated 

with storms in the Santa Cruz Mountains occur only 

locally. Most storm-related channel changes are no 

more severe than those associated with moderate 

events. Catastrophic channel changes are limited to 

localized areas with exceptional mass movement in 

the form of debris flows and debris avalanches that 

are triggered by high pore water pressures caused 

by locally intense precipitation. The moderate volumes of colluvium introduced elsewhere are transported with little affect on channel geometry 

because much of the colluvium is characterized by 

relatively small grain sizes (sand), because channel 

gradients are generally steep, and because channels 

usually do not contain large quantities of alluvium 
.. 

- LANDSLIDE 

,, , 

AGGRADA- ..__..1'-- LANDSLIDE 

DAM OR 

TION r- DEBRIS JAM 

,, n 

STREAM 

DEFLECTION 

... 

-

BANK 

EROSION 

'----------"'1 LANDSLIDE --

-

,, 

DEBRIS 

FAN 

,, 

GULLYING 

FIGURE 10.-Schematic representation of positive feedback 

between physical processes in northwestern California (after 

Colman, 1973). 

prior to major storms. The relatively coherent bedrock found in the area limits streambank erosion. 

Streamside failure due to undercutting is therefore 

relatively limited, and the positive feedback found 

between hillslope and stream channel processes in 

northwestern California does not occur to any great 

extent in the Santa Cruz Mountains. Major channel 

changes associated with storm events are therefore 

limited to localized areas that receive maximum precipitation intensities. 

The contrast in channel response in the two study 

areas is the result of interactions between naturally 

occurring physical processes operating in the 

respective areas. Although cultural activity may 

cause the impacts of any given storm event to be 

disproportionately large, these activities do not 

34 

alter basic process interactions. A more delicate balance exists between processes in northwestern California than in the Santa Cruz Mountains. This 

suggests that it would be easier for cultural 

activities to cause storms to have disproportionately 

large impacts on stream channels in northwestern 

California than in the Santa Cruz Mountains. 

The contrast in channel response occurs despite a 

similarity in the magnitude and frequency of sediment transport in both areas. The effectiveness of 

flood events in shaping channel morphology in these 

mountainous areas is therefore independent of the 

magnitude and fre.quency of sediment transport and 

is best judged on the basis of impact duration. Channel morphology present in most stream reaches at 

any given time in northwestern California reflects 

the effects of individual storms and the length of 

time available for moderate post-flood flows to modify flood effects. In contrast, channel morphology in 

the Santa Cruz Mountains reflects the effects of both 

moderate and extreme flow events. Where overwhelming volumes of sediment have been introduced 

to channels during previous storms, channels tend to 

flow through alluvial channels that are relatively 

wide and fiat. Elsewhere, channels tend to be Vshaped and relatively steep, and presumably reflect 

effects of moderate events at least as much as effects 

of extreme events. Since the localized effects generated by any one storm can persist longer than the 

recurrence interval of the storm itself, channel morphology throughout the area probably reflects the 

effects of multiple storms. 

The key to understanding why persistent stormrelated effects in northwestern California are more 

widespread than those in the Santa Cruz Mountains 

lies in identifying the physical processes operating 

on hillslopes and stream channels in each area, as 

well as assessing how these processes interact. 

Study of this interaction not only provides information describing the effects of major floods on the 

morphology of stream channels, but also provides 

information on the role of various hydrologic events 

in shaping general basin morphology. 

REFERENCE CITED 

Colman, S.M., 1973, The history of mass movement processes in 

the Redwood Creek basin, Humboldt County, California: 

paper presented in lieu of M.S. Thesis, University Park, 

Pennsylvania State University, 180 p. 
Effects of Dam Construction on Channel Geometry 

and Bed Material in Bear Creek, 

Denver, Colorado 

By R. F. Hadley and W. W. Emmett 

The objective of the study is to determine the 

downstream effects on channel geometry and 

characteristics of bed material caused by construction of a flood-control dam and reservoir on 

Bear Creek near Denver, Colo. This is a "backyard" 

project that requires 2 or 3 days a year in the field for 

surveys, data collection, and analysis. 

Bear Creek originates on Mount Evans along the 

Continental Divide, west of Denver, and flows eastward out of the mountains onto the plains where it 

joins the South Platte River in the Denver metropolitan area. The drainage area of Bear Creek is 

approximately 260 mi2 ~ most of which lies in the 

mountains. There are two streamflow gaging stations on Bear Creek with more than 50 years of 

record. One is at Morrison where the stream leaves 

the mountains, and the second is at Sheridan near 

the mouth. The mean annual flow at Morrison is 53 

ft3/s and is 38.8 ft3/s near the mouth. Before the 

flood-control dam was constructed, there was generally a snowmelt peak in the spring and occasional 

flood peaks from summer thunderstorms. 

The channel was relatively unregulated before 

1979 except for diversion of flows for irrigation of 

about 12,000 acres. In July 1979, a flood-control dam 

constructed by the U.S. Army Corps of Engineers 

near Morrison was completed and impoundment of 

Bear Creek Lake began. Since the closure of the 

dam, the flow in Bear Creek has been regulated and 

peak discharges have been reduced. 

In March 1977, five cross sections were surveyed 

and monumented on Bear Creek in Bear Creek Park 

between South Lamar Avenue and South Sheridan 

Boulevard in a reach about 700 feet long. The study 

reach is about three-fourths mile upstream from the 

gaging station near the mouth of Bear Creek. The 

five cross sections have been surveyed three times, 

twice before the dam was closed in 1977 and 1978 and 

once after dam closure in 1982. Bankfull width of the 

five cross sections ranged from 37 to 62 feet and 

averaged 46.2 feet in 1977 before dam closure. The 

mean bankfull depth ranged from 1.2 to 2.4 feet and 

averaged 1.6 feet. In 1982 the bankfull width ranged 

from 43 to 76 feet and averaged 54.8 feet. The mean 

bankfull depth ranged from 1.8 to 3.0 feet and averaged 2.5 feet. In the study reach, the gradient has 

decreased from 0.421 to 0.316 percent. Although the 

channel has become wider and deeper since the dam 

closure, the most obvious change is the large 

increase in depth. Changes in width probably have 

been restricted by the dense vegetation growth 

along the banks that confine the flow. 

Cross sections 1 and 2 are located in a pool, cross 

sections 3 and 4 are located on a riffle, and cross 

section 5 is at the upstream end of a second pool. In 

1977 the median diameter of bed material in the pools 

was 0.48 mm, and the median diameter of bed material on the riffle was 4. 6 mm. 

Sediment Storage and Discharge in Steep Unstable Terrain 

By Richard J. Janda 

Storage of readily erodible sediment in and adjacent to stream channels profoundly influences fluvial 

sediment discharge, particularly in steep unstable 

terrain. Most recent hydrologic and geomorphic 

investigations by the U.S. Geological Survey have 

emphasized transport processes; storage of sedi35 

ment, however, is commonly an equally important 

aspect of long-term movement of sediment drainage 

basins. Sediment discharge in headwater reaches of 

humid steepland streams is commonly supply limited, whereas downstream reaches are more likely to 

be transport limited. The impact of some land-use 
changes on sediment discharge and the geomorphic 

significance of storms of a given magnitude can be 

properly documented only if changes in storage are 

considered along with changes in transport. The 

initial locations, volume, and physical characteristics of stored sediment, and the changes in these 

parameters while in storage, are all matters of interest (Dietrich and others, 1982). The sedimentation 

impact of two comparable floods on a river may differ 

greatly if the recurrence interval of the floods is less 

than the time required to recharge streamside sediment storage areas. 

The volume of temporarily stored modern 

alluvium along a river is commonly more than ten 

times its average annual total sediment discharge 

(Swanson and others, 1982b). Alluvium may be 

stored in bedforms, behind organic debris or landslide dams, and on bars and flood plains. Sediment 

discharge and channel characteristics might also be 

influenced by storage changes associated with 

streamside outcrops of glacial drift, lahars, colluvium, loess, residual soil, and unconsolidated bedrock as well as modern alluvium. The type and 

stability of storage are a function of stream order and 

terrain characteristics; vegetation plays a particularly prominent role. Storage in channels, flood 

plains, and alluvial fans may delay and attenuate 

peak downstream delivery of sediment introduced 

from hillslope disturbances. Conversely, increased 

peak-water discharge may cause the transport of 

stored sediment without increased hillslope erosion. 

Increased water and sediment discharge commonly 

lead to increased channel width, thereby setting up 

self-reinforcing (positive) feedback that further 

accelerates erosion. In fact, changes in channel 

width generally exert a more profound influence on 

storage than do changes in bed elevation in mountainous terrain. 

Examples of these processes are seen in the 

Oregon Cascades (Swanson and Fredricksen, 1982; 

Swanson and others, 1982a), the Coast Ranges of 

California and Oregon (Janda and others, 1975; 

Dietrich and Dunne, 1978), and the Mount St. 

Helens impact area of southwestern Washington 

(Meyer and Janda, in press). 

The Water Resources Division is often asked to 

assess the immediate and long-term sedimentation 

impacts of intense storms, changes in land use, and 

more exotic forms of disturbance. These assess36 

ments often must be performed in a short time and 

with limited funds. Nonetheless, before undertaking such projects, one should, as a minimum, assess 

qualitatively whether the system of interest is supply-limited or transport-limited. Preferably, one 

should develop in as quantitative terms as practicable a flow chart of the storage or landscape elements 

of interest and the transport processes that move 

sediment between elements. This procedure will 

help identify which storage elements and transport 

processes most need further documentation. If the 

system is supply limited, historical observation, 

time sequential aerial photographs, and stratigraphic techniques may provide more useful information than short-term transport studies. 

If we are to develop predictive capabilities, we 

shall have to make increased use of analytical models. However, existing sediment routing models will 

have to be improved by making them two-dimensional and by incorporating stochastic as well as 

deterministic elements within them. Calibration and 

verification of such models will require carefully 

selected long-term data sets. 

REFERENCES CITED 

Dietrich, W. E., and Dunne, T., 1978, Sediment budget for a small 

catchment in mountainous terrain: Zeitschrift fUr Geomorphologie supplement, v. 29, p. 191-206. 

Dietrich, W. E., Dunne, T., Humphrey, N. F., and Reid, L. M., 

1982, Construction of sediment budgets for drainage basins: 

U.S. Forest Service General Technical Report PNW-141, p. 

5--23. 

Janda, R. J., Nolan, K. M., Harden, D. R., and Colman, S.M., 

1975, Watershed conditions in the drainage basin of Redwood Creek, Humboldt County, California, as of1973: U.S. 

Geological Survey Open-File Report 75-568. 

Meyer, D. F., and Janda, R. J., Sedimentation downstream from 

the 18 May, 1980 North Fork Toutle River debris avalanche 

deposit, Mount St. Helens, Wash., in Proceeding of the 

Symposium, Mount St. Helens, 5 years later (in press). 

Swanson, R. J., and Fredricksen, R. L., 1982, Sediment routing 

and budgets: Implications for judging impacts of forestry 

practices: U.S. Forest Service General Technical Report 

PNW-141, p. 129-137. 

Swanson, R. J., Fredricksen, R. L., and McCorison, F. M., 1982a, 

Material transfer in a western Oregon forested watershed, 

in Edmunds, R. L., ed., The natural behavior and response 

to stress of western coniferous forests: Stoudsburg, Penn., 

Dowden, Hutchinson, and Ross, p. 233-266. 

Swanson, R. J., Janda, R. J., and Dunne, T., 1982b, Summary: 

Sediment budget and routing studies: U.S. Forest Service 

General Technical Report PNW-141, p. 157-165. 
Bedload 

Variability in Measured Bedload Transport During 

Constant and Slowly Changing Water-Discharge Conditions 

By William P. Carey 

Cyclic variations in bedload transport under constant water-discharge conditions are an inherent 

part of the bedload transport process. Although 

these cyclic variations have been measured extensively in the laboratory, similar information is not 

available from field measurements. The existing 

field data sets on cyclic variations generally consist 

of a small number of samples that yield little information about the nature of transport cycles. Collecting comprehensive field data on these variations is 

complicated by the restriction of constant or slowly 

changing water discharge. 

The sand-bed channels of western Tennessee are 

particularly suited to this type of sampling because 

they tend to hold their peak discharge for periods of 

up to several days and then recede slowly. During 

periods of sustained peak discharge, it is assumed 

that bedload transport has equilibrated with the flow 

conditions and that measured variability is indicative 

of the inherent variability in the transport process. 

During a 4-day period of slowly changing waterdischarge conditions, four sets of bedload samples 

were obtained at the same sampling point using the 

standard 65-pound Helley-Smith bedload sampler. 

The sample sets consist of 43, 50, 80, and 120 samples. Samples for the three larger sample sets were 

collected consecutively with approximately 3 minutes between samples. Water discharge was essentially constant during each sample set and varied 

less than 15 percent for the 4-day period. 

Individual measured transport rates exhibit large 

variations from one sample to the next, as shown in 

figure 11. These individual rates can be converted to 

dimensionless rates by dividing each individual in a 

set by the mean rate for the set. When these dimensionless rates are plotted as cumulative frequency 

distributions, they show good agreement with the 

theoretical probability distribution derived for the 

case of ripples on dunes (fig. 12). As the number of 

samples increases, the similarity between the 

sampled and theoretical distributions also increases. 

37 

FIGURE 11.-Variability of 120 consecutive bedload samples. 

LULU 

ali-

...J <{ 90 ...Ja: 

§o 

LULU 80 l-Ie:{<{ 

a:~ 70 

00 

LU~ 

> LU 60 a: I 

m~-

~~50 

Z...J 

<{ <{ 40 1-::J 

<{d 

ILU ---Theoretical 

- - - - - 1 20 consecutive samples 

1 3 5 

RELATIVE TRANSPORT RATE Qb/Qb 

FIGURE 12.-Theoretical and sampled distributions of relative 

transport rates. 
Probability distributions for the 80- and 120-sample 

sets closely app~oximate the theoretical distribution. This agreement between sampled and theoretical distributions has been verified by many laboratory investigations and by the few field data sets 

that have a sufficient number of samples. 

A plot of measured transport rates versus time for 

the 120-sample set shows that peak transport rates 

seem to occur at approximately equal intervals (fig. 

11). This cyclical trend is well documented in laboratory studies and has been shown to correspond to the 

passage of dune bedforms. By applying a smoothing 

technique to the same data set, these short-term 

cycles become very distinct and an oscillation 

appears of much longer term (fig. 13). The smoothing 

function, shown as the vertical axis of figure 13, is the 

summation of the individual bedload rates divided by 

the mean of all bedload rates measured during the 

period of sampling. This longer term oscillation has 

also been reported in laboratory studies and may be 

caused by groups of large and small dunes moving 

past the sampling point. Information on the frequency and length of bedforms was not obtained 

during the sampling period. 

FIGURE 13.-Variability of 120 consecutive bedload samples after 

smoothing. 

The data collected in this study are believed to 

constitute one of the most comprehensive sets of field 

observations on cyclic variability in existence today. 

These observations confirm the existence of at least 

two superimposed cycles occurring under conditions 

of constant or slowly changing water discharge. 

Some Characteristics of Fluvial Processes in Rivers 

By William W. Emmett, Luna B. Leopold, and Robert M. Myrick 

Fluvial processes in rivers have been studied 

extensively in the United States during the past 20 

years. This paper relates some older studies of scour 

and fill to some new studies for which detailed data 

on water-surface slopes and bedload-transport rates 

help to substantiate earlier interpretations. 

Although our discussion is based on data from three 

small rivers, the principles involved have transfer 

value to other rivers. 

As maximum values of water-surface slope shift 

from riffles during low flow to pools during high flow, 

a similar reversal in maximum values of stream 

power takes place; this reversal is reflected in measured values of bedload-transport rate. Both pool 

and riffle reaches are likely to contribute sediment to 

bedload, resulting in generalized scour during high 

flow. However, spatially variable bedload-transport 

rates require those reaches with the least available 

stream power during times of high transport rate to 

38 

temporarily fill as continuity in the sediment budget 

is maintained. Similarly, those reaches with the least 

available stream power during times of receding 

river stage become sinks for storage of the moving 

sediment. This process helps explain the sorting 

mechanism of sediment and the maintenance of poolriffle sequences in rivers. The volume of scoured 

material within its annual travel distance is, on average, equal to annual bedload, but this is only an 

approximation because all bed particles do not move 

at the same speed or travel the same distance. Scour 

is associated with dilation of the grain bed through 

the scour depth, but individual particles move intermittently and at a speed much less than that of the 

water. The volume of material scoured and moved 

may be large, but because of its low mean speed 

downstream, the entire volume does not move out of 

a long reach but, in effect, is shifted downstream 

only a limited distance. 
Measurement of Bedload Discharge in Nine Illinois 

Streams with the Helley-Smith Sampler 

By Julia B. Graf 

Samples collected with the Helley-Smith bedload 

sampler provide useful information about transport 

of sand-size sediment in Illinois streams. Bedload 

samples were collected from 1978 through 1981 at 

nine sites ranging in drainage area from 432 to 4,393 

mi2 . Sampling sites and years of sampling are: Vermilion River near Leonore (1980 and 1981), Spoon 

River near Seville (1981), La Moine River near 

Ripley (1981), Kishwaukee River near Perryville 

(1981), Green River near Geneseo (1978--81), Rock 

River near Joslin (1978--81), Edwards River near 

New Boston (1980), Henderson Creek near Oquawka 

(1978--81), and Kaskaskia River near Venedy Station 

(1981). The purpose of the sampling program was to 

provide information needed to estimate volume of 

sand-sized material entering the Mississippi River 

and two of its major tributaries, the Rock River and 

the Illinois River. 

All streams sampled drain flat to gently rolling 

terrain. Surficial materials in all drainage basins are 

composed largely of unconsolidated sediment deposited by processes related to Pleistocene glaciationloess, drift, till, and dune sand. Bedrock is exposed 

in places along some of the streams, particularly the 

Rock and Vermilion Rivers. Bed materials in all 

streams except the Vermilion River range from fine 

to coarse sand. The Vermilion River has a bed composed primarily of granule to cobble gravel. Median 

diameters of bed materials at sampling sites are: 

Vermilion River, 3.65 mm; Spoon River, 0.56 mm; La 

Moine River, 0.57 mm; Kishwaukee River, 0. 76 mm; 

Green River, 0.28 mm; Rock River, 0.67 mm; 

Edwards River, 0.53 mm; Henderson Creek, 0.38 

mm; and Kaskaskia River, 0.29 mm. 

The Helley-Smith samples provide the basis for 

bedload-discharge rating curves for the Rock and 

Kaskaskia Rivers and Henderson Creek. The 10 

samples from the Rock River, collected at flows ranging up to almost the peak discharge of record, yield a 

well-defined bedload transport curve. Data from 

Henderson Creek cover a much narrower range of 

flow conditions and show wide scatter. Sampling 

methods that changed over the 4-year sampling 

period may have affected results. Although a transport curve was developed from the data, additional 

sampling is needed to obtain a reliable curve. Only 

39 

three measurements define the Kaskaskia River rating curve, but these cover a range of flow conditions 

and fall on a straight line. Measured bedload discharges near Venedy Station are all much less than 

bedload discharges computed from hydraulic and 

channel characteristics, suggesting that a reservoir 

30.6 mi upstream of the site may be a significant 

factor in reducing bedload. 

The possibility of extending bedload-discharge 

rating curves or of developing curves for stations 

with few measurements was investigated by comparing measured bedload discharge with bedload 

discharge computed from hydraulic and channel 

characteristics for a range of flow conditions. Three 

theoretical or empirical methods were used for the 

computations. One bedload sample was collected in 

each of the Spoon, Kishwaukee, and Edwards 

Rivers. Comparison of computed bedload discharges 

with the one measured value made possible the 

selection of an appropriate method for computing 

bedload discharge for each of these streams. No one 

computational method best represents bedload discharge in these streams. No bedload discharge rating curve was developed for the La Moine River, 

because the two measured bedload discharges are 

not sufficient for development of a rating curve and 

do not agree well with the computed bedload discharges. Bedload discharges measured in the Vermilion River, which has a sand, gravel, and bedrock 

bed, were much lower than any computed bedload 

discharges. Large bed material grains or high flow 

velocities may have interfered with the operation of 

the bedload sampler. A paucity of movable bed material also may be a cause of low measured bedload 

discharge at that site. 

The dominant size of bedload in all streams 

sampled is in the range from 0.25 to 0.50 mm. Suspended sediment in all sampled streams is composed 

predominantly of silt- and clay-sized particles (less 

than 0.062 mm), with only a few percent of the sample being larger than the sampler bag mesh. Therefore, for most of these streams, the bedload sample 

probably contains very little sediment that was actually traveling in suspension. However, high percentages of sediment less than 0.25 mm in some bedload 

samples reflect significant suspended load of a size 
close to the sampler bag mesh size. Very high percentages of sediment less than 0.25 mm collected in 

Green River samples (30--54 percent) suggest that 

the very fine bed materials in that stream may be 

clogging the sampler. Because of this inferred clogging, samples were not used to develop a bedload 

discharge rating curve for the Green River. 

Suspended-sediment discharge was measured at 

40 

the same time as bedload for nine of the samples. The 

fraction of total sediment discharge that traveled 

within 3 in. of the bed ranged from about 0.1 percent 

to 10 percent. The bedload fraction was low for the 

Kaskaskia and Vermilion Rivers (0.4 and 0.1 percent, respectively) and was highest for the Kishwaukee and Rock Rivers and Henderson Creek (7 

percent, 5 percent, and 2-10 percent, respectively). 
LIST OF ATTENDEES 

Northeastern Region 

Leslie D. Arihood, Indianapolis, Ind. 

Gerald L. Goddard, Madison, Wise. 

Julia B. Graf, Urbana, Ill. 

John R. Gray, Urbana, Ill. 

Lloyd A. Reed, Harrisburg, Penn. 

Thomas H. Yorke, Harrisburg, Penn. 

Southeastern Region 

William P. Carey, Nashville, Tenn. 

Philip B. Curwick, Baton Rouge, La. 

John George (Regional Office), Atlanta, Ga. 

James H. Ficken (HIF), Bay St. Louis, Miss. 

Glenn G. Patterson, Columbia, S.C. 

Andrew Simon, Nashville, Tenn. 

Central Region 

John Costa, Lakewood, Colo. 

James E. Kircher, Lakewood, Colo. 

David H. Marshall, Albuquerque, N.Mex. 

Wilbur J. Matthes, Jr., Iowa City, Iowa 

In Che Yang, (Central Laboratory) Arvada, Colo. 

Western Region 

Dallas Childers, Jr., Vancouver, Wash. 

Richard J. Janda, Vancouver, Wash. 

Holly A. Martinson, Vancouver, Wash. 

David F. Meyer, Vancouver, Wash. 

K. Michael Nolan, Menlo Park, Calif. 

Thomas C. Pierson, Vancouver, Wash. 

Rhea P. Williams, Boise, Idaho 

Research 

William W. Emmett, Lakewood, Colo. 

Marvin C. Goldberg, Lakewood, Colo. 

R. Edward Hickman, Reston, Va. 

Arthur J. Horowitz, Atlanta, Ga. 

Cliff R. Hupp, Reston, Va. 

Waite R. Osterkamp, Reston, Va. 

John V. Skinner, Minneapolis, Minn. 

E. Michael Thurman, Lakewood, Colo. 

Headquarters 

G. Douglas Glysson, Quality of Water Branch 

41 
GPO 785-048/48015