U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2006-5016

In cooperation with the Illinois Department of Natural Resources, Office of Water Resources 

and the U.S. Army Corps of Engineers, St. Louis District

Suspended-Sediment Yields and Stream-Channel 

Processes on Judy’s Branch Watershed in the 

St. Louis Metro East Region in Illinois

Suspended-Sediment Yields and StreamChannel Processes on Judy’s Branch 

Watershed in the St. Louis Metro East 

Region in Illinois

By Timothy D. Straub, Gary P. Johnson, Donald P. Roseboom, and Carlos R. Sierra

In cooperation with the Illinois Department of Natural Resources, 

Office of Water Resources and the U.S. Army Corps of Engineers, 

St. Louis District

Scientific Investigations Report 2006–5016

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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Cover Photos:

Top Left: Bank retreat in Judy’s Creek approximately 300 feet downstream of bank-rod BR123 (photo taken looking at the right bank on 

November 28, 2000).

Top Right: Bank retreat in Judy’s Creek upstream of bank-rod BR123 and downstream of bank-rod BR124 (photo taken looking upstream 

on July 5, 2004).

Bottom Left: Bank retreat in Judy’s Branch at bank-rod BR102 (photo taken looking upstream on March 7, 2002). Note exposed bank rod 

with orange flag and 3-foot long silver soil probe included for scale. 

Bottom Middle: Loess bank in Judy’s Branch near bank-rod BR199 (photo taken looking at left bank on May 16, 2001)

Bottom Right: This tree in Schoenberger Creek (bluff watershed in the region) originally was located on the top of bank; however, a rotational bank failure caused the tree to grow at an angle. Subsequent bank retreat left the tree in its current location and orientation in the 

stream channel (photo taken looking upstream on July 2, 2001).
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................4

Purpose and Scope ..............................................................................................................................4

Description of the Study Area ...........................................................................................................4

Geology..........................................................................................................................................4

Alluvial Soil Deposits over Glacial Till .............................................................................5

Colluvial Deposits ...............................................................................................................6

Loess Cliffs...........................................................................................................................6

Climate...........................................................................................................................................6

Streamflow......................................................................................................................................................6

Suspended-Sediment Yields ........................................................................................................................9

Data Collection......................................................................................................................................9

Analysis and Results ............................................................................................................................9

Stream-Channel Processes .......................................................................................................................11

Data Collection....................................................................................................................................11

Analysis and Results .........................................................................................................................11

Bank Rod .....................................................................................................................................15

Cross Section..............................................................................................................................17

Bank-Retreat Sediment Yield...................................................................................................18

Bank Stability..............................................................................................................................21

Model Development .........................................................................................................22

Model Simulation..............................................................................................................23

Summary and Conclusions.........................................................................................................................24

Acknowledgments.......................................................................................................................................26

References Cited..........................................................................................................................................26

Appendix A: Weight and coarse-sieve analysis data for bed-sediment samples collected 

on riffles near bank rods and soil borings in Judy’s Branch watershed, in the 

St. Louis Metro East region in Illinois .........................................................................................29

Appendix B: Soil-boring analysis for Judy’s Branch watershed in the St. Louis Metro East 

region in Illinois...............................................................................................................................33

Appendix C: Atterberg Limits for Judy’s Branch watershed in the St. Louis Metro East 

region in Illinois...............................................................................................................................39

Appendix D: Bank-failure types for Judy’s Branch watershed in the St. Louis Metro East 

region in Illinois...............................................................................................................................41

Figures

1–2. Maps showing—

 1. Location of A) Judy’s Branch watershed and the St. Louis Metro East region

 in Illinois and B) the maximum extent of major glaciations............................................2

 2. Judy’s Branch watershed in the St. Louis Metro East region in Illinois.......................3
iv

3. Photograph of typical bank type with cohesive alluvium, a thin alluvial sand lens, 

 and glacial till at Judy’s Branch watershed, in the St. Louis Metro East region in 

 Illinois..............................................................................................................................................5

4. Graph showing grain-size distribution for different representative soils found in 

 Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.............................5

5. Map showing location of streamflow and suspended-sediment stations in Judy’s 

Branch watershed, in the St. Louis Metro East region in Illinois, and stream 

 network used for analysis of bank-rod data ............................................................................7

6. Graph showing streamflow and suspended-sediment concentrations for a storm 

 event on July 19, 2001, at Route 157 on Judy’s Branch watershed, in the St. Louis 

 Metro East region in Illinois ......................................................................................................10

7. Map showing location of cross sections and bank rods for Judy’s Branch 

 watershed, in the St. Louis Metro East region in Illinois......................................................13

8. Diagram showing example of survey data including cut and fill indicators at xs8 

 in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.......................14

9. Map showing location of soil borings in Judy’s Branch watershed, in the St. Louis 

Metro East region in Illinois ......................................................................................................15

10. Photographs showing bank retreat through time for BR104_204 in Judy’s Branch, 

 in the St. Louis Metro East region in Illinois...........................................................................16

11–14. Maps showing—

 11. Annual bank-retreat values from bank rods in Judy’s Branch watershed, in the 

 St. Louis Metro East region in Illinois...............................................................................18

 12. Annual estimated reach-retreat values from bank rods in Judy’s Branch water

 shed, in the St. Louis Metro East region in Illinois.........................................................19

 13. Annual cut or fill values from resurveyed cross sections in Judy’s Branch 

 watershed and Cahokia Canal, in the St. Louis Metro East region in Illinois............20

 14. Annual estimated reach cut or fill values from resurveyed cross sections in 

 Judy’s Branch watershed, in the St. Louis Metro East region in Illinois....................21

15. Graph showing average-annual suspended-sediment yield for each station 

 (July 2000 through June 2004) and estimated average-annual suspended-

 sediment yield from bank retreat (June 2000 through June 2004), in Judy’s 

 Branch watershed, in the St. Louis Metro East region in Illinois .......................................22

16–18. Diagrams showing–

 16. Conceptualized modeled streambank showing all failure surfaces attempted 

 for one bank type in Judy’s Branch watershed, in the St. Louis Metro East 

 region in Illinois....................................................................................................................22

 17. Factor of safety with respect to the river height as measured from the 

 streambed on the recession limb of the hydrograph in Judy’s Branch 

 watershed, in the St. Louis Metro East region in Illinois ..............................................24

 18. Factor of safety with respect to bank height for a saturated bank and 1.5 feet 

 river level and 70 degrees bank angle for streambank types in Judy’s Branch 

 watershed, in the St. Louis Metro East region in Illinois ..............................................25
Tables

1. Precipitation values at the National Oceanic and Atmospheric Administration 

 (NOAA) station at Edwardsville, Illinois, July 2000 through June 2004................................6

2. Streamflow and suspended-sediment stations used in the study and 

 corresponding drainage areas, Judy’s Branch watershed, in the St. Louis Metro 

 East region in Illinois ....................................................................................................................7

3. Mean daily flow for July 2000 through June 2004 and individual years at 

 suspended-sediment stations in Judy’s Branch watershed, in the St. Louis Metro 

 East region in Illinois ....................................................................................................................8

4. Peak instantaneous streamflow for July 2000 through June 2004 and individual 

 years for the Route 157 station, in Judy’s Branch watershed, in the St. Louis Metro 

 East region in Illinois ....................................................................................................................8

5. Peak instantaneous streamflow for July 2000 through June 2004 and individual 

 years for the undeveloped headwater station, in Judy’s Branch watershed, in the 

 St. Louis Metro East region in Illinois........................................................................................8

6. Peak instantaneous streamflow for July 2000 through June 2004 and individual 

 years for the urban tributary station, in Judy’s Branch watershed, in the St. Louis

 Metro East region in Illinois ........................................................................................................8

7. Streamflow and suspended-sediment concentrations for a storm event on July 19, 

2001, at Route 157 on Judy’s Branch watershed, in the St. Louis Metro East region 

 in Illinois .........................................................................................................................................9

8. Sediment yield for July 2000 through June 2004 and individual years for each 

 station, in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois ........12

9. Cross-section information near bank rods in Judy’s Branch watershed, in the 

 St. Louis Metro East region in Illinois......................................................................................12

10. Stream-channel changes at resurveyed cross sections in Judy’s Branch 

 watershed, in the St. Louis Metro East region in Illinois......................................................14

11. Bank-retreat data from bank rods in Judy’s Branch watershed, in the St. Louis 

 Metro East region in Illinois ......................................................................................................17

12. Sediment-yield results for different types of data for Judy’s Branch watershed, 

 in the St. Louis Metro East region in Illinois...........................................................................19
vi

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Weight and Mass

ton per day (ton/d) 0.9072 metric ton per day

ton per day (ton/d) 0.9072 megagram per day (Mg/d)

ton per mile per year (ton/mi-yr) 0.5637 megagram per year per kilometer

ton per year (ton/yr) 0.9072 megagram per year (Mg/yr)

ton per year (ton/yr) 0.9072 metric ton per year

Pressure

pound per square foot (lb/ft2) 0.04788 kilopascal (kPa) 

Density

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter (kg/m3)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD29).

Conversion Factors
Abstract

Judy’s Branch watershed, a small basin (8.64 

square miles (mi2)) in the St. Louis Metro East 

region in Illinois, was selected as a pilot site to 

determine suspended-sediment yields and streamchannel processes in the bluffs and American 

Bottoms (expansive low-lying valley floor in the 

region). Suspended-sediment and stream-channel data collected and analyzed for Judy’s Branch 

watershed are presented in this report to establish 

a baseline of data for water-resource managers to 

evaluate future stream rehabilitation and management alternatives. The sediment yield analysis 

determines the amount of sediment being delivered 

from the watershed and two subwatersheds: an 

urban tributary and an undeveloped headwater (primarily agricultural). The analysis of the subwatersheds is used to compare the effects of urbanization 

on sediment yield to the river. The stream-channel 

contribution to sediment yield was determined by 

evaluation of the stream-channel processes operating on the streambed and banks of Judy’s Branch 

watershed. Bank stability was related to hydrologic 

events, bank stratigraphy, and channel geometry 

through model development and simulation. 

The average suspended-sediment yield from 

two upland subwatersheds (drainage areas of 0.23 

and 0.40 mi2) was 1,163 tons per square mile per 

year (tons/mi2-year) between July 2000 and June 

2004. The suspended-sediment yield at the Route 

157 station was 2,523 tons/mi2-year, near the outlet 

of Judy’s Branch watershed (drainage area = 8.33 

mi2). This is approximately 1,360 tons/mi2-year 

greater than the average at the upland stations for 

the same time period. This result is unexpected 

in that, generally, the suspended-sediment yield 

decreases as the watershed area increases because 

of sediment stored in the channel and flood plain. 

The difference indicates a possible increase in yield 

from a source, such as bank retreat, and supports 

the concept that land-use changes increase streamflows that may in turn result in higher rates of bank 

retreat. Utilizing both bank-rod data and resurveyed 

cross-section data, it was determined that approximately half of the suspended-sediment yield at 

Route 157 during July 2000-June 2004 came from 

bank retreat. 

Given that bank retreat can be a substantial 

portion of the sediment yield, understanding bank 

stability processes is important. Bank stability can 

be assessed mathematically by computing the factor 

of safety, which is defined by the ratio of the shear 

strength (resisting force) along the failure surface 

and the shear stress (driving gravitational force). 

Once the factor of safety falls below one, the bank 

theoretically becomes unstable. Bank-stability 

conditions were related to hydrologic events, bank 

type, and channel geometry through model development and simulation. The most common type of 

bank in the watershed consists of cohesive alluvial 

soil deposits overlying a stiff glacial till. A stability chart for different bank types was developed 

using a bank-stability analysis. Banks steeper than 

70 degrees and higher than from 10 to 11.5 feet 

(depending on bank type) become at risk for mass 

failure in the watershed under conditions that pro- mote saturation of the bank and a sudden drop in the 

river level. 

Suspended-Sediment Yields and Stream-Channel 

Processes on Judy’s Branch Watershed in the St. Louis 

Metro East Region in Illinois

By Timothy D. Straub, Gary P. Johnson, Donald P. Roseboom, and Carlos R. Sierra 
Figure 1. Location of A) Judy’s Branch watershed and the St. Louis Metro East region in Illinois and B) the maximum extent of major 

glaciations (modified from Grimley, 2000).

   Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Figure 2. Judy’s Branch watershed in the St. Louis Metro East region in Illinois.

Introduction 
Introduction

Judy’s Branch1 watershed, a small basin (8.64 

mi2) in the St. Louis Metro East region in Illinois, is 

affected by land-use changes in the bluffs draining 

to the American Bottoms (expansive low-lying valley floor in the region) (figs. 1 and 2). In the 1800s, 

much of the forest and prairie in the watershed, 

which includes the upland bluffs, was converted to 

agricultural land. Since the 1940’s, urbanization 

in the uplands has caused increased streamflows 

to the river that can result in higher erosion rates. 

Erosion of the upland bluffs has resulted in the loss 

of private land, and deposition of sediment in the 

American Bottoms has resulted in increased flooding. The U.S. Army Corps of Engineers, St. Louis 

District (USACOE-STL) East St. Louis and Vicinity 

Ecosystem Restoration and Flood-Control Project 

has a goal to reduce sediment yield to the American 

Bottoms by 70 percent (U.S. Army Corps of Engineers, 2003a). In 2000, the U.S. Geological Survey, 

Illinois Water Science Center (USGS-IWSC); the 

Illinois Department of Natural Resources, Office 

of Water Resources (IDNR-OWR), and USACOESTL began a cooperative investigation to analyze 

suspended-sediment yields and stream channel 

processes in Judy’s Branch watershed. This information will be helpful to water-resource managers 

in analysis of river rehabilitation and watershedmanagement alternatives like those proposed in 

Watson and Eom (2003) to help control erosion in 

the upland bluffs. Methods and analyses of this 

study can potentially be applied to similar watersheds in the Midwest with bluffs and an extensive 

valley floor. Judy’s Branch is similar to other 

bluff watersheds in the Mississippi and Illinois 

River watersheds and the data and analysis may 

be of benefit to regional and national studies by 

furthering the knowledge of hydrologic and sediment process in these type of watersheds. Minimal 

hydrologic and sediment data have been collected 

on small-scale watersheds such as Judy’s Branch. 

The information from this study will help advance 

understanding of regional and temporal variations 

of suspended-sediment yield and stream-channel 

processes. 

Purpose and Scope

Sediment and stream-channel data collected 

and analyzed for Judy’s Branch watershed in the 

St. Louis Metro East region in Illinois are presented 

in this report to document a baseline of suspended1

 Spelled Judys Branch on some maps.

sediment yields and stream-channel processes that 

can be used by water-resource managers to evaluate 

future stream rehabilitation and management alternatives. The sediment-yield analysis determines 

the amount of sediment delivered from the watershed and two subwatersheds: an urban tributary and 

undeveloped headwater (primarily agricultural). 

The analysis of the subwatersheds is used to compare the effects of urbanization on sediment yield. 

The stream-channel contribution to sediment yield 

was determined by evaluation of the stream-channel processes operating on the streambed and banks 

of Judy’s Branch watershed. Bank-stability conditions were related to hydrologic events, bank type, 

and channel geometry through model development 

and simulation. Precipitation, streamflow, and 

suspended-sediment data were analyzed on a yearly 

basis, with a year defined as July 1 through June 30. 

Description of the Study Area 

The study area consists of two distinct topographic areas: a bluff region and the American 

Bottoms (figs. 1 and 2). The bluffs consist of hills 

shaped by streams incised into loess, alluvium, and 

stiff glacial till. The American Bottoms forms part 

of the Mississippi River flood plain, which contains 

many canals, lakes, and swamps with low relief. 

Judy’s Branch flows into Cahokia Canal.

Geology

Knowledge of Quaternary geology and the 

depositional sequences underlying Judy’s Branch 

watershed is crucial to understanding the interac- tion among sediment and stream-channel processes. 

Sediments in the St. Louis Metro East region were 

deposited primarily during the pre-Illinoian, Illinoian, and Wisconsinan glacial stages of the Pleistocene Epoch; and the Holocene Epoch, which are 

characterized by alluvial processes. The margins of 

glaciation and their location with respect to the St. 

Louis Metro East region are shown in figure 1. Further information on the geology and soil deposits 

is included in the following: the “Stream-Channel 

Processes” section of this report, Grimley (2000), 

Grimley and others (2001), and Willman and others 

(1975).

Dominant bank types for Judy’s Branch watershed are as follows: 1) banks composed of alluvial 

soil deposits overlying stiff glacial soils (glacial till) 

with the presence or the absence of sand-and-gravel 

layers between the two deposits, with and without 

vegetative cover and trees; 2) banks composed of 

normally consolidated mixed colluvial and alluvial 

 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
soils in which a glacial till soil horizon 

is buried; and 3) high loess cliffs (bluffs) 

and other bank types, such as shale and 

siltstone outcrops, and banks composed 

of fill material from past coal mining and 

urban development. Fill deposits from 

coal mines generally consist of silty sandand-gravel with fragments of brick, wood, 

and other debris. 

Alluvial Soil Deposits over Glacial Till

Alluvial soil deposits over stiff glacial 

till (fig. 3) may include sand-and-gravel 

layers between the alluvium and the 

glacial till. Vegetative cover, including 

trees, may be present. The alluvial soil 

deposits consist of normally consolidated, 

medium-to-soft clayey silt. Alluvial 

soils at Judy’s Branch watershed generally contain approximately 30-percent 

clay and the rest silt, with trace amounts 

of sand (fig. 4) (methods for determining grain-size distributions are discussed 

Figure 3. Typical bank type with cohesive alluvium, a thin alluvial sand 

lens, and glacial till at Judy’s Branch watershed, in the St. Louis Metro East 

region in Illinois.

Figure 4. Grain-size distribution for different representative soils found in Judy’s Branch watershed, in the St. Louis Metro East region in 

Illinois.

Introduction 
in the “Stream-Channel Processes” section of this 

report). Although the grain-size distributions for 

most of the samples collected are consistent with 

these percentages, some samples had substantially 

greater sand content. Sand-and-gravel layers within 

the alluvial soil deposits commonly occur at the 

interface between the clayey-silt alluvial deposits 

and the glacial till. Sand layers also are present 

within the alluvial stratigraphy and likely were 

deposited as bars. 

Glacial till consistently crops out at the base 

of the banks and is sometimes found at mid-bank 

height. The glacial till strength probably varies with 

the amount of time exposed to water. Weathered 

till has soft-to-medium consistencies, whereas the 

intact till has stiff-to-hard consistencies. Glacial till 

has low clay content (20 percent), and most of the 

till consists of silt. The glacial till is similar to the 

loess (wind-blown silt) in terms of grain-size distribution (fig. 4). In some areas, the glacial till contains sand, gravel, and cobbles, but the subsample 

shown in figure 4 does not include particle sizes 

greater than 2 mm. Although the coarse material in 

the till constitutes a small proportion of the particlesize distribution, this material can be vital in distinguishing one deposit from another (Drew Phillips, 

Illinois State Geological Survey, written commun. 

2002). 

Colluvial Deposits

Colluvial deposits are generally loose soil 

material that accumulates at the base of a hill. The 

material is moved to the base of the hill by gravity 

in the form of bank failure or is washed downslope 

by rain. These deposits are of softer consistencies 

than the cohesive alluvial deposits. These deposits 

are usually clayey silt mixed with some sand and 

organic matter. 

Loess Cliffs

Although loess deposits constitute most of the 

surficial materials of the Judy’s Branch watershed 

and the upland bluffs of the St. Louis Metro East 

region, seldom do these deposits control bank stability and erosion of the streambanks. Loess cliffs 

generally are formed at appreciable distances away 

from streams.

Loess has a high strength when dry but low 

strength when wet. The decrease in strength results 

primarily because of the dissolution of the calcium 

carbonate that holds silt particles together. Also, 

the dry loess mass has a high magnitude of suction 

forces holding the silt together because of capillary 

effect (Terzaghi and others, 1996).

Climate

The study area has a temperate, humid, conti- nental climate. Long-term daily climatic data are 

available for the National Oceanic and Atmospheric 

Administration (NOAA) station at Edwardsville, Ill, 

approximately 1.5 mi north of the study area. The 

average annual precipitation is 40.21 in. from calendar year 1971 through 2000. The average annual 

precipitation is 45.90 in. from July 2000 through 

June 2004 (table 1). 

Streamflow

Knowing the properties of streamflow is important when quantifying sediment yields and streamchannel processes. Automated streamflow-gaging 

equipment and suspended-sediment samplers were 

installed at three stations in the watershed in June 

2000 (table 2 and fig. 5). Measurements of discharge are made with current meters and acoustical flowmeters based on methods adapted by the 

USGS-IWSC. These methods and streamflow-computation methods are described in Rantz and others 

(1982), and Cutshaw and others (2004).

The mean daily streamflows for the study 

period (July 1, 2000, through June 30, 2004) and 

individual years are presented in table 3. The daily 

mean streamflow is the average of all the instantaneous flows (collected at 5-minute intervals for each 

station). These daily mean streamflows are then 

averaged over the time period of interest to obtain 

the mean daily streamflow. The mean daily streamflow for a given time period is useful in comparing 

Table 1. Precipitation values at the National Oceanic and Atmospheric Administration (NOAA) station at Edwardsville, Illinois, July 2000 

through June 2004.

Precipitation at Edwardsville, Illinois (inches) 

Average Annual

July 2000-June 2004

Total 

July 2000-June 2001

Total 

July 2001-June 2002

Total 

July 2002-June 2003

Total

July 2003-June 2004

45.90 45.19 57.23 34.16 47.03

   Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Table 2. Streamflow and suspended-sediment stations used in the study and corresponding drainage areas, Judy’s Branch watershed, 

in the St. Louis Metro East region in Illinois.

[mi2, square miles]

Station (fig. 5) Station Number Drainage Area (mi2)

Urban tributary 05588710 0.23

Undeveloped headwater 05588700 .40

Route 157 05588720 8.33

Figure 5. Location of streamflow and suspended-sediment stations in Judy’s Branch watershed, in the St. Louis Metro East region in 

Illinois, and stream network used for analysis of bank-rod data.

Streamflow 
Table 3. Mean daily flow for July 2000 through June 2004 and individual years at suspended-sediment stations in Judy’s Branch 

watershed, in the St. Louis Metro East region in Illinois.

[ft3/s, cubic feet per second]

Station (fig. 5)

Mean Daily Flows (ft3/s)

July 2000-June 2004 July 2000-June 2001 July 2001-June 2002 July 2002-June 2003 July 2003-June 2004

Urban tributary 0.31 0.29 0.40 0.24 0.33

Undeveloped headwater .40 .32 .59 .23 .48

Route 157 7.67 6.45 11.14 4.56 8.52

Table 4. Peak instantaneous streamflow for July 2000 through June 2004 and individual years for the Route 157 station, in Judy’s Branch 

watershed, in the St. Louis Metro East region in Illinois.

[ft3/s, cubic feet per second]

Time Period Date Time Peak Streamflow (ft3/s)

July 2000–June 2004 08-24-2001 2:25 2,540

July 2000–June 2001 07-18-2000 21:35 1,500

July 2001–June 2002 08-24-2001 3:00 2,540

July 2002–June 2003 06-26-2003 2:25 654

July 2003–June 2004 05-27-2004 20:10 1,700

Time Period Date Time Peak Streamflow (ft3/s)

July 2000–June 2004 06-11-2002 15:45 155

July 2000–June 2001 07-18-2000 20:05 99

July 2001–June 2002 06-11-2002 15:45 155

July 2002–June 2003 06-10-2003 17:40 48

July 2003–June 2004 05-27-2004 18:20 107

Table 5. Peak instantaneous streamflow for July 2000 through June 2004 and individual years for the undeveloped headwater station, in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

[ft3/s, cubic feet per second]

Table 6. Peak instantaneous streamflow for July 2000 through June 2004 and individual years for the urban tributary station, in Judy’s 

Branch watershed, in the St. Louis Metro East region in Illinois.

[ft3/s, cubic feet per second]

Time Period Date Time Peak Streamflow (ft3/s)

July 2000–June 2004 06-11-2002 16:10 107

July 2000–June 2001 07-18-2000 20:30 58

July 2001–June 2002 06-11-2002 16:10 107

July 2002–June 2003 06-26-2003 :50 32

July 2003–June 2004 05-27-2004 19:35 52

   Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
the relative magnitudes of flow among other time 

periods of the same length. This comparison is 

important when determining the flows available for 

transporting sediment and affecting stream-channel 

processes. 

The lowest mean daily flow during the study 

period occurred between July 2002 and June 2003. 

The highest mean daily flow during the study period 

occurred between July 2001 and June 2002 (table 

3).

The peak-instantaneous streamflow for the 

study period and individual years are presented for 

each of the three stations in tables 4-6. The peak 

instantaneous streamflow when compared to the 

mean daily flow for a given time period can give 

an indication of the flashiness of the stream in the 

watershed. The term flashiness reflects the fre- quency and rapidity of changes in streamflow, especially during storm events (Baker and others, 2004). 

In other words, flashiness can indicate how the peak 

for a storm event compares to the average flow. The 

greater the discrepancy between the two values, the 

greater the flashiness of the stream. Also, as with 

the mean daily flows for a given time period, the 

peak streamflow is important when determining the 

flows available for transporting sediment and affecting stream-channel processes. The variation in peak 

streamflow and mean daily flow values is similar 

(tables 3-6).

Suspended-Sediment Yields

Suspended-sediment data are useful in quantify- ing the sediment yield from Judy’s Branch water- shed. The following sections describe suspendedsediment data collection and analysis. 

Data Collection

At continuous-record sediment stations (table 2 

and fig. 5), suspended-sediment concentrations were 

determined from samples collected with depth-integrating, isokinetic samplers at single-vertical locations, and/or with automatic water samplers collecting samples from a fixed point. Periodic cross 

sections are obtained at various verticals with depthintegrating, isokinetic samplers to compare to and 

adjust the single-vertical samples and/or the fixed 

point samples to compute the mean suspended-sediment concentration at the cross section.

Because of the small drainage areas of the 

data-collection sites, the hydrograph for storm 

events are relatively short duration (hours), and, 

therefore, logistically difficult to sample by USGSIWSC personnel or local observers. Stage-weighted 

event, suspended-sediment samples were collected 

by electronically connecting the automatic suspended-sediment collector to the streamflow station. 

When possible, USGS-IWSC personnel collected 

depth-integrated samples using isokinetic samplers 

to compare and adjust the fixed-point samples to 

compute the mean suspended-sediment concentration at the cross section. All suspended-sediment 

samples were collected following protocols outlined 

in Edwards and Glysson (1999). 

Analysis and Results

Methods used in the computation of sediment 

records are described in Guy (1970) and Porterfield 

(1972). During periods of rapidly changing flow, 

samples are collected more frequently (generally, 

multiple times on the rising and falling limbs of the 

storm hydrograph) (fig. 6). Certain streamflow conditions cause the shear stress to be higher on the rising limb than on the falling limb of the hydrograph, 

causing larger sediment transport on the rising 

limb than on the falling limb at a given flow depth 

(Julien, 2002). This pattern can be seen in Judy’s 

Branch watershed at Route 157 (fig. 6). Also, as 

noted in the “Stream-Channel Processes” section, 

mass failures can occur on the falling limbs in 

flashy streams. The slump material may stay near 

the bank and then be transported downstream on the 

next rising limb of a storm, causing increased sediSuspended-Sediment Yields 

Table 7. Streamflow and suspended-sediment concentrations 

for a storm event on July 19, 2001, at Route 157 on Judy’s Branch 

watershed, in the St. Louis Metro East region in Illinois.

[ft3/s, cubic feet per second; mg/L, milligrams per liter]

Time

Streamflow

(ft3/s)

Concentration

(mg/L) Sample Method

7:37 6.6 226 Estimated Sample

8:17 93 2,120 Estimated Sample

8:46 267 3,330 Estimated Sample

9:11 503 5,800 Automatic Sample

9:27 583 13,200 Depth-Integrated Sample

9:48 574 6,680 Automatic Sample

10:33 371 1,640 Automatic Sample

11:17 382 1,800 Automatic Sample

11:31 480 7,530 Automatic Sample

11:42 578 9,990 Depth-Integrated Sample

12:03 731 16,200 Automatic Sample

13:50 389 4,500 Estimated Sample

17:46 119 872 Estimated Sample

22:34 39 450 Estimated Sample
ment concentrations on the rising limb as compared 

to the falling limb. Also, during low-flow periods, 

sediment can be deposited in the river channel and 

then again be transported during the rising limb of 

the next storm. Lastly, the higher of the two flood 

peaks has higher resulting sediment concentration 

(fig. 6 and table 7). In general, the higher the flood 

peak, the higher the peak sediment concentration at 

a given location. 

The computed sediment discharges for days 

of rapidly changing flow or concentration were 

computed by the subdivided-day method (timedischarge weighted average) (Guy, 1970 and Porterfield, 1972). Therefore, for those days when the 

published sediment discharge value differs from the 

value computed as streamflow (ft3/s) times mean 

suspended-sediment concentration (mg/L) times 

0.0027 (conversion factor to tons/day), the sediment 

discharge for that day was computed by the subdivided-day method. For periods when no samples 

were collected, daily discharges of suspended 

sediment were estimated on the basis of streamflow, suspended-sediment concentrations observed 

immediately before and after the periods, and suspended-sediment concentrations for other periods of 

similar streamflow. The sediment load for a given 

day was calculated by the product of the sediment 

discharge and 1 day. The daily suspended-sediment 

loads from July 1 through June 30 of the following 

year were then summed and divided by the number 

of days in a year and by the drainage area of the 

watershed to obtain the suspended-sediment yield 

(table 8). 

The suspended-sediment yield from the undeveloped headwater and urban tributary were 1,204 

and 1,122 tons per square mile (tons/mi2-year) 

(table 8) for the study period. Suspended-sediment yields from a fully developed urban watershed 

are expected to be less than that of an undeveloped 

watershed given less source of sediment supply in 

an urban environment (Wolman, 1967) (assuming 

the stream channel is not of an appreciable size 

or substantially eroding). Note that for the first 3 

years of the study, the urban tributary had a higher 

suspended-sediment yield than the undeveloped 

headwater. The suspended-sediment yield from the 

Figure 6. Streamflow and suspended-sediment concentrations for a storm event on July 19, 2001, at Route 157 on Judy’s Branch 

watershed, in the St. Louis Metro East region in Illinois

10 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
urban tributary may have been less if it were not 

for demolition and reconstruction of a substantial 

number of buildings in the watershed that increased 

the amount of exposed soil surface available for erosion. Building demolition and reconstruction was 

essentially complete before the fourth year (July 

2003 through June 2004) of data collection.

The suspended-sediment yield at the Route 157 

station (2,523 tons/mi2-year) is approximately 1,360 

tons/mi2-year larger than the average of the urban 

tributary and undeveloped headwater suspendedsediment yields. This result is unexpected in that, 

generally, the suspended-sediment yield decreases 

as the watershed area increases because of sediment being stored in the channel and flood plain. 

In general, the sediment-delivery ratio decreases 

primarily with the size of drainage area (Julien, 

2002). The sediment-delivery ratio is defined as 

the ratio of sediment yield and gross erosion on a 

watershed. The gross erosion amounts to the sum 

of the upland and channel erosion in a watershed 

(Julien, 2002). The increase in suspended-sediment 

yield seen in Judy’s Branch watershed indicates a 

possible increase in yield from a source, such as 

bank retreat, and supports the concept of the landuse changes causing increased streamflows that may 

result in higher rates of bank retreat. Stream-channel processes like bank retreat will be presented in 

the “Stream-Channel Processes” section and then 

compared to the suspended-sediment yields.

Stream-Channel Processes

Understanding the stream-channel processes 

operating on the streambed and banks of Judy’s 

Branch watershed can help determine the streamchannel contribution to sediment yield. In this 

study, bank retreat, streambed incision (lowering of 

the streambed elevation), and channel deposition 

(material filling any portion of the channel) were 

considered. 

Given that bank retreat can be a substantial 

portion of the sediment yield in a watershed, understanding bank-stability processes that lead to bank 

failure by mass wasting (collapse of all or part of 

the bank in mass) is important. Bank stability can 

be simulated by computing the ratio of the shear 

strength (resisting force) along a failure surface 

and the shear stress (driving gravitational force). 

Bank-stability conditions were related to hydrologic 

events, bank type, and channel geometry through 

model development and simulation.

Data Collection

To determine the sediment yield from bank 

retreat in Judy’s Branch watershed, bank rods 

were installed at 28 locations (fig. 7 and table 9). 

Steel rods driven horizontally into the river banks 

are measured from the end of the rod to the bank 

regularly and after large storm events (near or 

greater than the bankfull flow). Also, IDNR-OWR 

personnel have surveyed the majority of the stream 

channel and surrounding flood plain at approximately 300- to 500-ft intervals. Twenty-seven of 

the cross sections are used in this study, including 

16 that have been surveyed twice and, therefore, are 

referred to as resurveyed cross sections (figs. 7 and 

8, and tables 9 and 10). 

The grain-size distribution data for the stream- bed samples are presented in appendix A. The 

streambed samples were not analyzed for this study, 

but may be useful for studies concerning sedimenttransport modeling and stream rehabilitation such as 

Watson and Eom (2003).

Bank-stability data were collected by way of 

field visits, exploratory soil borings, in-situ tests, 

laboratory tests, and visual classification of samples 

obtained from both the borings and directly from 

the banks. A Geoprobe model 5400 was used 

to obtain continuous soil borings at six locations 

(fig. 9) with depths ranging from 20 to 24 ft below 

ground surface (appendixes B and C). Bank samples were taken at various locations from the different bank types (appendix C). 

Analysis and Results 

Bank retreat is composed of two components: 

bank erosion by hydraulic shear and bank failure 

by mass wasting. Bank erosion is the detachment, 

entrainment, and removal of bank material as individual grains or aggregates by fluvial and sub-aerial 

processes (Thorne and others, 1997). Bank failure 

is the collapse of all or part of the bank in mass, 

in response to bank instability processes (Thorne 

and others, 1997). In this study, stream-channel 

processes are considered as a combination of bank 

retreat, streambed incision (lowering of the stream- bed elevation), and channel deposition (material 

filling any portion of the channel). 

The maximum bank and streambed movement 

for the time period were determined at each resur- veyed cross section (table 10). Also, at all 27 cross 

sections, the bank height and angle were determined 

(table 9). Photos of bank retreat through time for 

BR104_204 (see fig. 7 for location) are shown in 

figure 10. The initial bank geometry (June 2, 2000) 

Stream-Channel Processes 11
Table 8. Sediment yield for July 2000 through June 2004 and individual years for each station, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois.

[tons/mi2-year, tons per square mile per year]

Station (fig. 5)

Station 

Number

Sediment Yield (tons/mi2-year)

07/2000–06/2004 07/2000–06/2001 07/2001–06/2002 07/2002–06/2003 07/2003–06/2004

Urban tributary 05588710 1,122 1,202 1,526 521 1,239

Undeveloped headwater 05588700 1,204 996 1,519 443 1,860

Route 157 05588720 2,523 1,709 4,872 637 2,875

Table 9. Cross-section information near bank rods in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois. Crosssection and bank-rod locations are shown in figure 7. 

[ft, feet; deg, degrees; ---, no data] 

Cross Section

CrossSection 

Map 

Number

Nearest

Bank 

Rod Map 

Number

Distance from 

Cross Section, 

(ft)

Bank Rod 

Installed 

on

Right Bank Left Bank

First 

Survey 

Date

Second 

Survey 

Date

Height

(ft)

Base

(ft)

Angle

(deg)

Height

(ft)

Base

(ft)

Angle

(deg)

7+41.74 (4) Ditch xs1 --- --- --- 19.9 41.0 25.8 10.5 21.9 25.7 10/1997 04/04/2002

7+41.74 (4) xs2 --- --- --- 9.5 11.7 38.9 8.8 9.3 43.5 10/1997 04/04/2002

188+43.73 (36) xs3 BR101 116 upstream Left Bank 13.3 25.7 27.3 12.1 26.4 24.6 10/1997 06/10/2002

182+94.9 xs4 BR102 235 upstream Left Bank 10.9 11.3 43.9 11.7 10.7 47.7 10/1997 04/04/2002

149+75.01(30) xs5 BR103_203 185 downstream Left Bank 12.4 17.5 35.3 12.9 3.1 76.5 10/1997 06/10/2002

2+76.48 (41) xs6 BR104_204 278 downstream Right Bank 12.9 15.9 38.9 10.7 49.1 12.3 01/1999 04/04/2002

2+76.48 (41)* xs6* BR105_205 42 downstream Right Bank 12.9 15.9 38.9 10.7 49.1 12.3 01/1999 04/04/2002

14+56.18 (46) xs7 BR199 160 downstream Right Bank 14.1 13.2 47.1 10.4 19.2 28.5 01/1999 04/04/2002

28+30.53 (53) xs8 BR106 50 downstream Right Bank 14.5 13.0 48.1 9.4 48.0 11.0 01/1999 04/04/2002

32+27.09 (54) xs9 BR106 465 downstream Right Bank 14.1 23.8 30.6 11.7 18.0 33.0 01/1999 04/04/2002

32+27.09 (54) (219) xs10 BR106 714 downstream Right Bank 4.0 7.9 26.6 7.4 7.9 43.0 01/1999 04/04/2002

--- --- BR107_108 --- --- --- --- --- --- --- --- --- ---

44+56.34 (60) xs11 BR109 9 downstream Right Bank 6.7 10.1 33.6 5.6 6.5 40.6 01/1999 04/04/2002

48+35.80 (62) xs12 BR110 110 downstream Right Bank 17.0 20.2 40.2 9.2 28.0 18.1 01/1999 04/04/2002

67+32.55 (72) xs13 BR111_211 71 downstream Right Bank 7.3 9.6 37.2 8.9 31.3 15.9 01/1999 04/04/2002

92+80.74 (86) xs14 BR125 20 downstream Left Bank 6.8 8.0 40.5 6.9 4.7 55.7 01/1999 04/04/2002

110+90.47 (94) xs15 BR112 102 downstream Left Bank 13.1 26.8 26.0 12.5 17.5 35.6 01/1999 04/04/2002

119+59.70 (99) xs16 BR113 126 downstream Right Bank 7.9 17.9 23.7 10.7 8.0 53.3 01/1999 04/04/2002

17+46.12 A (6600) xs17 BR114 181 downstream Left Bank 4.8 2.3 64.4 5.7 9.7 30.4 08/2000 ---

35+40.44 A (15100) xs18 BR115 12 downstream Left Bank 5.5 14.1 21.4 6.9 6.3 47.4 08/2000 ---

35+40.44 A (15101) xs19 BR116 35 downstream Left Bank 5.0 5.8 40.7 6.8 6.8 45.0 08/2000 ---

47+26.94 A (158) xs20 BR117_217 23 upstream Left Bank 7.3 12.3 30.6 13.5 13.5 45.1 08/2000 ---

66+00.18 A (17903) xs21 BR118 123 upstream Left Bank 2.9 2.0 55.3 5.3 7.8 34.1 08/2000 ---

66+00.18 A (17903) xs21 BR126 143 downstream Right Bank 2.9 2.0 55.3 5.3 7.8 34.1 08/2000 ---

14+52.13 Tr114(287) xs22 BR119 15 upstream Right Bank 5.4 3.1 60.2 9.2 14.3 32.7 02/1999 ---

14+52.13 Tr114(77) xs23 BR120 7 upstream Right Bank 9.0 6.3 54.9 7.1 19.9 19.6 02/1999 ---

24+01.22 Tr (118) xs24 BR121 5 downstream Left Bank 5.6 3.8 56.0 7.5 19.9 20.6 02/1999 ---

28+49.44 Tr (120) xs25 BR122 46 downstream Left Bank 5.4 4.6 49.7 9.9 16.3 31.2 02/1999 ---

30+14.24 Tr (211) xs26 BR123 5 upstream Left Bank 6.1 4.7 52.5 2.6 4.8 28.0 02/2002 ---

34+63.10 Tr A (212) xs27 BR124 286 downstream Left Bank 10.8 7.4 55.6 4.1 7.4 29.0 02/2002 ---

*

Cross section listed twice because it is nearest to two sets of bank rods. 

12 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Figure 7. Location of cross sections and bank rods for Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

Stream-Channel Processes 13
Table 10. Stream-channel changes at resurveyed cross sections in Judy’s Branch watershed, in the St. Louis Metro East region in 

Illinois. Cross-section locations are shown in figure 7.

[Negative values for bank retreat and fill minus cut indicate material removed; positive values for bank retreat and fill minus cut indicate materials deposited; 

Max., maximum; ft2, square feet; ft, feet; Elev., elevation; ---, not applicable]. 

Cross 

Section

CrossSection

Map 

Number

Cut

(ft2)

Fill

(ft2)

Fill 

minus

 Cut

(ft2)

Streambed 

Max. Elev. 

Change (ft)

Maximum 

Right Bank 

Retreat (ft)

Maximum 

Left Bank 

Retreat (ft)

Reach

Characteristic Comment

7+41.74 (4) Ditch xs1 0.0 143.8 143.8 1.1 3.3 10.1 Straight

7+41.74 (4) xs2 31.6 19.4 -12.2 .0 -5.1 2.3 Straight

188+43.73 (36) xs3 321.4 28.5 -293.0 -1.1 4.1 -24.4 Straight Debris Jam

182+94.9 xs4 23.6 14.2 -9.4 -.7 1.3 -1.3 Straight

149+75.01(30) xs5 15.9 3.3 -12.6 -.3 -1.3 .9 Straight

2+76.48 (41) xs6 42.7 47.0 4.3 -.2 -2.9 7.1 Meandering

2+76.48 (41) xs6 42.7 47.0 4.3 -.2 -2.9 7.1 Meandering

14+56.18 (46) xs7 40.9 41.7 .8 1.3 -2.5 2.9 Meandering

28+30.53 (53) xs8 53.4 41.5 -12.0 -.7 -6.9 6.8 Meandering

32+27.09 (54) xs9 42.0 51.2 9.2 -.6 -1.4 -3.2 Straight

32+27.09 (54) (219) xs10 42.9 31.4 -11.6 -.3 4.1 -2.4 Meandering

44+56.34 (60) xs11 .2 5.5 5.3 -.3 -1.2 -3.4 Straight

48+35.80 (62) xs12 91.4 13.4 -78.0 -.1 -3.3 -6.3 Meandering Old Mass Failure Eroding on Left 

67+32.55 (72) xs13 20.0 25.2 5.2 .0 -2.6 2.6 Straight

92+80.74 (86) xs14 25.5 26.9 1.4 .0 5.5 -1.3 Meandering

110+90.47 (94) xs15 13.5 5.1 -8.4 -.1 -1.0 -1.1 Straight

119+59.70 (99) xs16 89.8 2.4 -87.4 -1.0 -3.5 -7.5 Straight Root Wad

Total --- 897.5 547.5 -350.3 --- --- --- --- ---

Figure 8. Example of survey data including cut and fill indicators at xs8 (fig. 7, and tables 9 and 10) in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois. Vertical scale is exaggerated four times that of the horizontal scale.

14  Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
is steeper than 70 degrees and higher than from 

10 to 11.5 ft. These values are the criteria for the 

banks to become unstable as noted in the “Model 

Simulation” section. Although, for example, the 

cross section (xs6) nearest BR104_204 (fig. 7 and 

table 9) indicate that the bank angles are 47.7 and 

38.9 degrees. The geometry of xs6 is nearly 280 ft 

upstream of BR104_204 and is not representative of 

the banks at the bank rod. Of the 27 cross sections 

nearest the bank rods, only one has a bank angle 

greater than 70 degrees (table 9). 

High maximum bank retreat on the left bank 

is indicated on cross-sections xs3, xs12, and xs16 

(table 10). These changes result from either tree 

jams or apparent erosion of a previous bank failure. 

Also, high maximum bank retreat on the right bank 

is evident in cross-section xs8 (fig. 8), but an equal 

amount of deposition on the left bank may indi- cate that the retreat results from lateral migration 

and hydraulic shear as opposed to bank instability. 

Many of the resurveyed cross sections have simi- lar properties. The maximum streambed elevation 

changes range from –1.1 ft (material removed) to 

1.3 ft (material deposited). These changes do not 

represent substantial movement (usually character- ized by multiple feet of movement), but monitoring 

of streambed-elevation changes is critical in deter- mining bank stability.

Bank Rod

The bank-retreat values from the bank-rod 

locations (fig. 11 and table 11) were annualized 

by dividing by the years of data collected. After a 

detailed stream reconnaissance, the annual bankretreat value at each bank-rod location was assigned 

to a representative stream reach (fig. 12). Note that 

Stream-Channel Processes 15

Figure 9. Location of soil borings in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.
Figure 10. Bank retreat through time for BR104_204 in Judy’s Branch, in the St. Louis Metro East region in Illinois. View looking 

downstream towards the Route 157 bridge that can be seen in the background. Photo on June 2, 2000, was taken by U.S. Geological 

Survey volunteer Dave Straub.

16 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
physical variation is present that cannot be represented with this methodology, but more detailed 

bank-rod monitoring was beyond the scope of the 

study. To obtain the annual volume of sediment 

contributing from the reach, the annual bank-retreat 

value is multiplied by the reach length and the average bank height at approximately the 1.5-year flow 

event. This annual volume is converted to sediment 

load by multiplying it by an approximate unitweight of soil (115 lbs/ft3

, reference discussion and 

data for soil borings in the “Bank Stability” section 

and appendix B, respectively) and then converted to 

tons (units used in the annual suspended-sediment 

load calculations). The annual sediment load is then 

divided by the stream miles to obtain sediment yield 

per linear increment (table 12).

Sediment yield calculated using bank-rod data 

equals 1,354 tons/mi-year (table 12) for the stream 

reach analyzed upstream of Route 157 (8.33 mi of 

stream–blue, green, orange, and red highlighted 

lines in figure 12). The bank-rod data were adjusted 

to the full stream network upstream of Route 157 

(20.2 mi of stream – dark black stream line in figure 

12), after the values were adjusted using the resurveyed data (discussed in the “Bank-Retreat Sediment Yield” section).

Cross Section

At each of the 17 resurveyed cross sections 

(table 10), the cut (material removed) and fill 

(material deposited) were determined (fig. 8 and 

table 10). This area was annualized by dividing 

by the number of years between the survey dates 

(fig. 13 and table 11). Note that xs1 is in Cahokia 

Canal, which is outside of Judy’s Branch watershed. 

Results at Cahokia Canal are not used to determine 

bank-retreat sediment yield in this study, but indicate that fill may be coming from sediments in other 

bluff watersheds like Judy’s Branch watershed. 

Stream-Channel Processes 17

Table 11. Bank-retreat data from bank rods in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois. Bank-rod 

locations are shown in figure 7. 

Bank Rod Installation Date

Bank Retreat as of July 05, 2004 (feet)

Total Annual

BR101 June 1, 2000 2.07 0.51

BR102 June 1, 2000 12.12 2.97

BR103_203 June 1, 2000 .41 .10

BR104_204 June 1, 2000 8.40 2.06

BR105_205 June 1, 2000 2.30 .56

BR106 June 1, 2000 8.22 2.01

BR107 June 1, 2000 4.37 1.07

BR108 June 1, 2000 4.77 1.17

BR109 June 1, 2000 .67 .16

BR110 June 1, 2000 1.28 .31

BR111_211 June 1, 2000 2.12 .52

BR112 June 1, 2000 .92 .23

BR113 June 1, 2000 5.82 1.43

BR114_214 June 1, 2000 1.81 .44

BR115 June 1, 2000 1.45 .36

BR116 June 1, 2000 1.75 .43

BR117_217 June 1, 2000 2.35 .57

BR118 June 1, 2000 2.32 .57

BR119 June 1, 2000 3.47 .85

BR120 June 1, 2000 .77 .19

BR121 June 1, 2000 .52 .13

BR122 June 1, 2000 .97 .24

BR123 June 1, 2000 2.27 .56

BR124 June 1, 2000 9.54 2.34

BR125 November 21, 2000 3.75 1.03

BR199 November 21, 2000 9.15 2.52

BR126 March 7, 2002 1.25 .54
The annual area of cut or fill then was assigned to 

a representative reach (fig. 14). Note that physical 

variation is present that cannot be represented with 

this methodology, but more detailed cross-section 

resurveying was beyond the scope of the study. The 

annual area was converted to sediment load by multiplying it by the length of the reach and an average 

unit-weight of soil (115 lbs/ft3) and then converted 

to tons (units used in the annual suspended-sediment load and bank-retreat calculations). The 

annual sediment load is then divided by the stream 

miles to obtain sediment yield per linear increment 

(table 12). Sediment yield calculated using crosssection data equals 652 tons/mi-year (table 12) for 

the stream reach analyzed upstream of Route 157 

(4.45 mi of stream–red, orange, and green highlighted lines in figure 14). 

Bank-Retreat Sediment Yield

Suspended-sediment yield at Route 157 was 

2,523 tons/mi2-year (fig. 15 and table 8). It is 

assumed that 1,163 tons/mi2-year of the suspendedsediment yield (average of the urban tributary and 

undeveloped headwater) comes from smaller watersheds within Judy’s Branch watershed with negligible stream channels (in other words, the sediment 

sources are overland and gully). This assumption 

leaves a minimum of 1,360 tons/mi2-year that must 

come from others sources in the watershed such as 

bank retreat. 

Bank-retreat sediment yield, estimated with 

bank-rod data, was 1,354 tons/mi-year for 8.33 mi 

of stream-channel length (assuming none of the sediment is stored in the channel). There are 20.2 mi 

of stream-channel length, upstream of Route 157. 

Figure 11. Annual bank-retreat values from bank rods in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

18 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Table 12. Sediment-yield results for different types of data for Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

[tons/mi-year, tons per mile per year]

Type Sediment Yield (tons/mi-year) Length of Stream Reach (miles)

U.S. Geological Survey

Bank-Retreat Rods (6/2000-7/2004)

 Bank-Rod Data to Route 157 1,354 8.33

 Bank-Rod Data to mouth 1,413 8.64

Illinois Department of Natural Resources

Cross-section Resurvey Data 

(10/1997–6/2002 and 1/1999–6/2002) 652 4.45

Stream-Channel Processes 19

Figure 12. Annual estimated reach-retreat values from bank rods in Judy’s Branch watershed, in the St. Louis Metro East region in 

Illinois. Gaps represent riprap reaches.
Multiplying 1,354 tons/mi-year times 20.2 mi and 

then dividing by the drainage area (8.33 mi2) results 

in 3,283 tons/mi2-year. From resurveyed cross-section data (table 10), it can be roughly estimated that 

for every ton of material removed from the channel, 

0.61 ton is stored in the channel. The exact percentages of stored sediment from bank retreat, upland, 

and gully erosion are not known. To obtain the 

lowest estimate of bank-retreat sediment yield, it is 

assumed that all the stored sediment is from bank 

retreat. Multiplying 3,283 tons/mi2-year by 0.39 

gives a sediment yield of 1,280 tons/mi2-year from 

bank retreat (fig. 15). 

Based on the discussion above, approximately 

half of the suspended-sediment yield at Route 157 

during July 2000-June 2004 came from bank retreat. 

The percentage from bank retreat probably would 

slightly increase if the amounts from each source 

that were stored in the channel could be determined. 

Figure 13. Annual cut or fill values from resurveyed cross sections in Judy’s Branch watershed and Cahokia Canal, in the St. Louis 

Metro East region in Illinois.

20 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Bank Stability

The bank-stability laboratory tests for the soil 

borings were performed at the Natural Resources 

Conservation Service (NRCS) soil mechanics 

laboratory in Lincoln, Nebraska. The tests consisted of routine grain-size distributions of both the 

coarse- and fine-grained material. Atterberg limits 

(plastic limit and liquid limit), torvane, unconfined 

compression tests, and consolidated undrained 

triaxial (CU) tests were done on cohesive soils. The 

results of the tests are presented in appendixes B 

and C. Results from the torvane and unconfined 

compression tests were not used in this study, so test 

methods are not discussed in this report. The CU 

test results are discussed in the “Model Simulation” 

section.

The USGS-IWSC tested samples in the laboratory collected from the banks. Tests for Atterberg limits and particle size by sieve analysis and 

hydrometer were completed on selected bank 

samples. Laboratory tests performed by both the 

NRCS and USGS-IWSC are made in conformance 

with the pertinent American Society for Testing and 

Materials (ASTM) (2000) procedures. Hydrometer 

tests and grain-size distribution tests were made in 

accordance with ASTM D422 and ASTM D2217 

specifications, respectively. ASTM D4318 specifications were used for Atterberg limit tests (appendix 

C). More detailed information on all the tests can 

be found in Terzaghi and others (1996). 

Stream-Channel Processes 21

Figure 14. Annual estimated reach cut or fill values from resurveyed cross sections in Judy’s Branch watershed, in the St. Louis Metro 

East region in Illinois.
Model Development

Bank failure in response to instability, as pre- sented in the “Bank Rod” section was observed at 

BR102, BR104_204, BR106, BR113, BR124, and 

BR199 (fig. 10 and table 11). A detailed discussion of bank failure types observed is presented in 

appendix D. Bank stability can be assessed mathematically by computing the factor of safety (Terzaghi and others, 1996). Factor of safety (FS) is 

defined by the ratio of the shear strength (resisting 

force) along the failure surface and the shear stress 

(driving gravitational force) and given as 

Once the factor of safety falls below one, the bank 

theoretically becomes unstable.

The simulation of the factor of safety computations using limit equilibrium was done with the 

bank-stability analysis software (SLIDE 3.0, 2005). 

The software searches for the critical failure surface 

through a user-specified region (fig. 16), considering river water confinement, pore-water pressures, surcharges, and layered banks. The software 

contains slope-stability analysis methods that are 

specified by the user. The U. S. Army Corps of 

Engineers (1970) and the Spencer (1967) methods 

were chosen for this study because they satisfy 

force equilibrium and may be applied to any shape 

of failure surface. More information about bankFigure 15. Average-annual suspended-sediment yield for each 

station (July 2000 through June 2004) and estimated averageannual suspended-sediment yield from bank retreat (June 2000 

through June 2004), in Judy’s Branch watershed, in the St. Louis 

Metro East region in Illinois.

 Shear Strength FS = ——————– .

 Shear Stress

Figure 16. Conceptualized modeled streambank showing all failure surfaces attempted for one bank type in Judy’s Branch watershed, 

in the St. Louis Metro East region in Illinois. 

22 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
stability methods may be found in Duncan (1996), 

Nash (1987), and U.S. Army Corps of Engineers 

(1970 and 2003b).

The consolidated undrained (CU) with porewater pressure measurement test was used to determine cohesive and frictional components of shear 

strength as outlined in Terzaghi and others (1996) 

and U.S. Army Corps of Engineers (2003b). Shear 

strength is represented by a Mohr-Coloumb failure 

envelope that relates shear strengths to either total 

or effective normal stress on the failure plane and is 

expressed in the case of total stresses as (U.S. Army 

Corps of Engineers, 2003b)

where:

c = cohesion intercept,

σ = total normal stress, and

φ = friction angle.

The undrained or total stress approach is necessary for analysis of short-term rapid loading of soil 

slopes, where dissipation of pore pressures is not 

allowed (U.S. Army Corps of Engineers, 1970 and 

2003b; Duncan, 1996). The strength parameters 

used for this analysis are those that occur when a 

large, sudden increase in load is brought on a soil 

mass. This action is similar to the conditions of 

excavated and built-up soils or slopes. The parameters to use for these cases are those obtained from 

an analogy with the “end of construction” condition 

for which the total stress approach applies. 

A storm event in which the bank becomes suddenly saturated reduces the negative pore-water 

pressure and increases the unit weight of the soil. 

Reduction of negative pore-water pressure during 

saturation after prolonged rain events is a critical 

factor in determining bank stability (Simon and others, 2000). Given the above conditions, the bank is 

considered acted upon by a rapid loading for which 

the prevailing conditions and strength parameters 

are consistent with the “end of construction” analogy. 

Laboratory results on clayey silt alluvium (ML) 

samples show an approximate value of cohesion 

intercept, c = 180 lb/ft2, and an angle of internal 

friction, φ =18o (appendix B). The colluvial banks 

are mainly composed of soft-to-very soft clayey 

silts and were considered to have a c = 100 lb/ft2

and a φ = 25o, back calculated from observations of 

failed bank geometry. The glacial till, which con- sists of stiff-to-very stiff overconsolidated clayey 

silts to silty clays, was assumed to have a c = 275 

lb/ft2 and a φ = 25o. The strength parameters for the 

glacial till are not as important as those parameters 

assigned for the bank materials above because the 

failure plane rarely crosses through the glacial till. 

The glacial till typically represents a boundary for 

failure planes or a base over which the sloping soil 

mass slides or rotates.

The cohesion incorporated by tree roots is Cr= 

205 lb/ft2, as determined by Simon and Collison 

(2001) as a typical value for sycamore trees. Root 

cohesion was considered for the upper 1.5 ft in this 

study for Judy’s Branch watershed. Tree surcharge 

was estimated assuming that the tree is a 30-ft long 

post with 2 ft diameter. The load was distributed 

over a 4-ft diameter base. 

The cohesion for the sand lens was determined 

to be negligible and the φ = 30o. These values were 

taken from typical strength values for loose cohesionless medium grained, poorly graded sands 

(Terzaghi and others, 1996). 

Model Simulation

The simulated bank types were alluvium over 

stiff glacial till with and without a sand lens (fig. 

16), alluvium over glacial till with a tree on top, 

and a bank consisting of colluvial deposits. Banks 

of 8, 10, and 13 ft in height were simulated for 

bank angles of 60, 70, and 80 degrees. Each of 

these combinations was simulated for five different 

stream-level heights. The glacial till was assumed 

to be at 1, 1.5, and 2 ft above the streambed for 8, 

10, and 13 ft banks, respectively. For every type, 

the banks were considered to be completely saturated except for the top approximately 2 ft of the 

bank (fig. 16). The water levels in the river var- ied from bankfull height to 1.5 ft depth to match 

the receding portion of a storm hydrograph. The 

combination of a saturated bank with receding 

water levels represents a flashy stream, during storm 

events, similar to that found in the urban setting in 

Judy’s Branch watershed. 

The results of the analysis for alluvium over 

glacial till (10 ft high and 70-degree bank angle) 

during the recession limb of the storm are shown in 

figure 17. Factor of safety degrades with the lowering of the river level when the alluvium remains 

saturated. 

Stability charts for all bank types and the 

condition where the stream level is at 1.5 ft and the 

streambank remains saturated are shown in figure 

18. Additional model runs were completed for bank 

angles other than 70 degrees. In order to know 

the factor of safety for bank angles other than 70 

degrees, a correction factor must be used. For an 

80-degree bank angle, the factor of safety for the 

given bank height must be multiplied by 0.9. For 

a 60-degree bank angle, the factor of safety for the 

given bank height must be multiplied by 1.2. 

Stream-Channel Processes 23

s = c + σ tan φ ,
The colluvial bank type has the lowest factor of 

safety. Also, this bank type becomes unstable at a 

bank height of approximately 9.8 ft. The alluvium 

over glacial till with sand-lens bank type has the 

second lowest factory of safety for bank heights 

less than 10.8 ft and the second highest for bank 

heights greater than 10.8 ft, and becomes unstable at 

a bank height of approximately 10 ft. The alluvium 

over glacial till with tree bank type has the greatest 

factor of safety for bank heights below 9.5 ft and 

the second highest between 9.5 and 10.8 ft, and the 

second lowest for bank heights greater than 10.8 ft. 

This bank type becomes unstable at a bank height 

of 10.3 ft. The alluvium over glacial till type has 

the greatest factor of safety for bank heights greater 

than 9.5 ft and the second highest between 8 and 9.5 

ft. This bank type becomes unstable at bank height 

of 11.5 ft. 

It can be interpreted from the analysis that the 

sand lens has a slight negative effect on the stability 

of the banks as compared to the alluvium over glacial till bank type. This effect results because sand 

lenses have little to no cohesion and mechanical 

strength is based only on frictional forces (Terzaghi 

and others, 1996). The simulation does not account 

for the sand lens allowing faster drainage of the 

bank, which can potentially increase bank stability. 

Summary and Conclusions

Judy’s Branch watershed, a small basin (8.64 

mi2) in the St. Louis Metro East region in Illinois, is 

affected by land-use changes in the bluffs draining 

to the American Bottoms. Judy’s Branch watershed 

was selected as a pilot site to determine suspendedsediment yield and stream-channel processes of 

streams draining the bluffs. In 2000, the U.S. 

Geological Survey, Illinois Water Science Center; 

Figure 17. Factor of safety with respect to the river height as measured from the streambed on the recession limb of the hydrograph in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

24  Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
the Illinois Department of Natural Resources, Office 

of Water Resources; and the U.S. Army Corps of 

Engineers, St. Louis District began a cooperative 

investigation to analyze suspended-sediment yields 

and stream channel processes in Judy’s Branch 

watershed. This information will be helpful to 

water-resource managers in analysis of river rehabilitation and watershed-management alternatives to 

help control erosion in the upland bluffs. Methods 

and analyses of this study can potentially be applied 

to similar watersheds in the Midwest with bluffs and 

an extensive valley floor. Judy’s Branch is similar 

to other bluff watersheds in the Mississippi and 

Illinois River watersheds and the data and analysis 

may be of benefit to regional and national studies by 

furthering the knowledge of hydrologic and sediment process in these types of watersheds. Minimal 

hydrologic and sediment data have been collected 

on small-scale watersheds such as Judy’s Branch. 

The information from this study will help advance 

understanding of regional and temporal variations 

of suspended-sediment yield and stream-channel 

processes. 

The sediment yield analysis determines the 

amount of sediment being delivered from the watershed and two subwatersheds: an urban tributary and 

an undeveloped headwater (primarily agricultural). 

The stream-channel contribution to sediment yield 

was determined by the analysis of stream-channel 

processes operating on the streambed and banks of 

Judy’s Branch watershed. Bank-stability conditions 

were related to hydrologic events, bank type, and 

channel geometry through model development and 

simulation.

The average suspended-sediment yield from 

two upland subwatersheds (drainage areas of 0.23 

and 0.40 mi2) was 1,163 tons/mi2-year between 

July 2000 and June 2004. The suspended-sediment 

yield at the Route 157 station was 2,523 tons/mi2-

year near the outlet of the watershed (drainage area 

= 8.33 mi2). This yield is approximately 1,360 

tons/mi2-year greater than the average of the upland 

stations for the same time period. This result is 

unexpected in that, generally, the suspended-sedi- ment yield decreases as the watershed area increases 

because of sediment stored in the channel and flood 

plain. The difference indicates a possible increase 

in yield from a source, such as bank retreat, and 

supports the concept that land-use changes increase 

streamflows that may result in higher rates of bank 

retreat. 

In this study, stream-channel processes were 

considered a combination of bank retreat, streambed incision (lowering of the streambed elevation), 

Figure 18. Factor of safety with respect to bank height for a saturated bank and 1.5 feet river level and 70 degrees bank angle for 

streambank types in Judy’s Branch watershed, in the St. Louis Metro East region in Illinois.

Summary and Conclusions 25
and channel deposition (material filling any portion 

of the channel). Utilizing both bank-rod data and 

resurveyed cross-section data, it was determined 

that approximately half of the suspended-sediment 

yield at Route 157 during July 2000-June 2004 

came from bank retreat. Bank-rod data and analysis collected in Judy’s Branch watershed also indicate that bank failure in response to bank instability 

occurred at six sites. Also, high maximum bankretreat values for resurveyed cross sections appeared 

to result from debris jams, erosion of colluvial 

deposits, or lateral migration of the stream channel. 

Data from resurveyed cross sections indicated the 

maximum streambed-elevation changes ranged from 

–1.1 ft (material removed – cut) to 1.3 ft (material 

deposited – fill). 

Given that bank retreat can be a substantial 

portion of the sediment yield, understanding bankstability processes is important. Bank stability can 

be assessed mathematically by computing the factor 

of safety. Factor of safety is defined by the ratio of 

the shear strength (resisting force) along the failure 

surface and the shear stress (driving gravitational 

force). Once the factor of safety falls below one, 

the bank theoretically becomes unstable. Different bank-stability simulations, as related to hydrologic events, and bank types and geometry were 

evaluated. The most common bank type is that of 

cohesive alluvial soil deposits overlying a very 

stiff glacial till. A stability chart for different bank 

types and geometries was developed. Banks steeper 

than 70 degrees and higher than from 10.0 to 11.5 

ft (depending on bank type) become theoretically 

unstable and mass failure may occur under conditions that promote saturation of the bank and a sudden drop in the river level. 

Acknowledgments

Mel Alison, Arlan Juhl, Rita Lee (of 

IDNR-OWR), and Debbie Roush and Michelle 

Kniep (of USACOE-STL) supported the format 

of this watershed study and use of advanced 

methodologies. They also assisted in data 

acquisition and facilitated communications with 

municipalities and interested groups. IDNROWR provided surveying assistance, including 

establishing control points and surveying channel 

cross sections. 

Roger Windhorn, from the U.S. Department 

of Agriculture, Natural Resources Conservation 

Service (NRCS) in Champaign, Ill., facilitated the 

correspondence and transport of soil-boring samples 

to the NRCS soil mechanics laboratory facilities in 

Lincoln, Nebraska. 

Technical assistance was also provided by the 

following USGS-IWSC employees: Robert Holmes 

(overall project oversight); Jennifer Sharpe (report 

illustration development); Perry Draper, Joe Norris, 

John Maurer (station installations and maintenance); 

and Angel Martin (report editing). 

References Cited

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2000, section 4, volume 04.08, Soil and rock (I): 

West Conshohocken, PA.

Baker, B.B., Richards, R.P., Loftus, T.T., and 

Kramer, J.W., 2004, A new flashiness index: 

characteristics and applications to midwestern 

rivers and streams: Journal of the American Water 

Resources Association, v. 40, no. 2, April 2004, 

p. 503-522, AWRA Paper Number 03095 available online at http://www.awra.org/jawra/papers/

J03095.html, last accessed October 2005.

Casagrande, A., 1948, Classification and identification of soils: Transactions of the American Society of Civil Engineers, 113, p. 901-991.

Cutshaw, S.R., Mills, P.C., Hogan, J.L., and Fazio, 

D.J., 2004, Water Resources Data-Illinois, Water 

Year 2004: U.S. Geological Survey Water-Data 

Report IL-04, 841 p.

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Journal Geotechnical Engineering, v. 22, no. 7, 

577-593.

Edwards, T.K., and Glysson, G.D., 1999, Field 

methods for measurement of fluvial sediment: 

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C2, 89 p.

Grimley, D.A., 2000, Quaternary geology of the 

St. Louis Metro East area, 63rd Annual Tri-State 

Field Conference, sponsored by the Illinois State 

Geological Survey: Illinois State Geological Survey Guidebook 32, 23-30.

Grimley, D.A., Phillips, A.C., Follmer, L.R., Wang, 

H., and Nelson, R.S., 2001. Quaternary and environmental geology of the Metro-East St. Louis 

area., Guidebook 33: Illinois State Geological 

Survey, Champaign, IL, p. 21-72.

26 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Guy, H.P., 1970, Fluvial sediment concepts: 

U.S. Geological Survey Techniques of WaterResources Investigations Report, book 3, Applications of Hydraulics, chapter C1, 55 p., accessed at 

http://water.usgs.gov/pubs/twri/.

Julien, P. Y., 2002, River Mechanics: Cambridge 

University Press, New York, NY, 434 p.

Nash, D., 1987, A comparative review of limit equi- librium methods of stability analysis, slope stabil- ity, edited by M.G. Anderson and K.S. Richards: 

John Wiley & Sons Ltd., New York, NY, chapter 

2, 41-55.

Porterfield, G., 1972, Computation of fluvial-sediment discharge: U.S. Geological Survey Techniques of Water-Resources Investigations Report, 

book 3, chapter C3, 66 p., accessed at http://water.

usgs.gov/pubs/twri/.

Rantz, S.E., and others, 1982, Measurement and 

computation of streamflow: Volumes 1 and 2: 

U.S. Geological Survey Water-Supply Paper 

2175, 631 p. 

Simon, A., Curini, A., Darby, S. E., and Langendoen, E. J., 2000, Bank and near-bank processes 

in an incised channel: Elsevier Science B.V., 

Geomorphology 35, 193-217.

Simon, A., and Collison, A., 2001, Scientific basis 

for streambank stabilization using riparian vegetation; proceedings of the Seventh Federal Interagency Sedimentation Conference, Reno, Nevada: 

V-47-V-54.

SLIDE 3.0, 2005, last accessed November 1, 2005, 

at http://www.rocscience.com/products/Products.

asp.

Spencer, E., 1967, A method of analysis of the 

stability of embankments assuming parallel 

interslide forces: Géotechnique, London, 17 (1), 

11-26.

Terzaghi, K., Peck, R. B., and Mesri, G., 1996, Soil 

mechanics in engineering practice. 3rd edition: 

John Wiley and Sons, Inc. New York, NY, 549 p.

Thorne, C.R., Hey, R.D., and Newson, M.D., 1997, 

Applied fluvial geomorphology for river engineering and management: John Wiley and Sons, 

Chichester, U.K., 376 p.

Thorne, C.R., 1998, Stream reconnaissance handbook: John Wiley and Sons, Chichester, U.K., 

133 p.

U.S. Army Corps of Engineers, 1970, Engineering 

and design – stability of earth and rock fill dams: 

Engineering Manual EM 1110-2-1902, Department of the Army, Corps of Engineers Office of 

the Chief of Engineers.

U.S. Army Corps of Engineers, 2003a, East St. 

Louis and vicinity, Illinois, ecosystem restoration and flood damage reduction project, general 

reevaluation final report with integrated environmental impact statement, St. Louis District.

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and design, slope stability: Engineering Manual 

EM 1110-2-1902, October 31, 2003, 205 p.

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design of Judy’s Branch: Colorado State Univer- sity, Department of Civil Engineering, Fort Collins, CO, 118 p.

Willman, H.B., Atherton, E., Buschbach, T.C., Collison, C., Frye, J.C., Hopkins, M.E., Lineback, 

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References Cited 27
28 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Appendix A 29

Sieve Number Sieve Opening (mm) Material Retained (g) Cumulative Retained (g) Cumulative Percent Retained Percent Finer

Judy’s Branch, Riffle near BR102 (fig. 7)

3/4 19 9.5 9.5 0.9 99.1

1/2 12.5 75 84.5 7.9 92.1

3/8 9.5 48.5 133 12.4 87.6

4 4.75 279 412 38.3 61.7

12 1.7 242.5 654.5 60.9 39.1

20 .85 192 846.5 78.8 21.2

40 .425 189.5 1,036 96.4 3.6

60 .25 29 1,065 99.1 .9

140 .106 7.5 1,072.5 99.8 .2

200 .075 .5 1,073 99.9 .1

pan 1.5 1,074.5 100.0 .0

Judy’s Branch, Riffle near SB2 (fig. 9)

3/4 19 139.5 139.5 20.4 79.6

1/2 12.5 58.5 198 28.9 71.1

3/8 9.5 64.5 262.5 38.3 61.7

4 4.75 101 363.5 53.1 46.9

12 1.7 101 464.5 67.8 32.2

20 .85 48 512.5 74.8 25.2

40 .425 118 630.5 92.0 8.0

60 .25 47.5 678 99.0 1.0

140 .106 7 685 100.0 .0

200 .075 0 685 100.0 .0

pan 0 685 100.0 .0

Judy’s Branch, Riffle near BR199 (fig. 7)

3/4 19 0 0 0.0 100.0

1/2 12.5 29.5 29.5 3.8 96.2

3/8 9.5 28 57.5 7.5 92.5

4 4.75 136 193.5 25.2 74.8

12 1.7 299.5 493 64.3 35.7

20 .85 121 614 80.1 19.9

40 .425 81.5 695.5 90.7 9.3

60 .25 49 744.5 97.1 2.9

140 .106 21 765.5 99.8 .2

200 .075 .5 766 99.9 .1

pan 1 767 100.0 .0

Judy’s Branch, Riffle near BR106 (fig. 7)

3/4 19 103.5 103.5 12.4 87.6

1/2 12.5 68.5 172 20.7 79.3

3/8 9.5 62 234 28.1 71.9

4 4.75 145 379 45.6 54.4

12 1.7 212 591 71.1 28.9

20 .85 87.5 678.5 81.6 18.4

40 .425 109.5 788 94.8 5.2

60 .25 33 821 98.7 1.3

140 .106 8 829 99.7 .3

200 .075 0.5 829.5 99.8 .2

pan 2 831.5 100.0 .0

Appendix A. Weight and coarse-sieve analysis data for bed-sediment samples collected on riffles near bank rods and soil borings in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois, on November 21, 2000.

[mm, millimeters; g, grams; BR, Bank Rod; SB, Soil Boring]
Sieve Number Sieve Opening (mm) Material Retained (g) Cumulative Retained (g) Cumulative Percent Retained Percent Finer

Judy’s Branch, Riffle near BR109 (fig. 7)

3/4 19 36 36 7.1 92.9

1/2 12.5 51 87 17.3 82.7

3/8 9.5 65.5 152.5 30.3 69.7

4 4.75 112 264.5 52.5 47.5

12 1.7 154 418.5 83.0 17.0

20 .85 50.5 469 93.1 6.9

40 .425 22 491 97.4 2.6

60 .25 6.5 497.5 98.7 1.3

140 .106 4 501.5 99.5 .5

200 .075 .5 502 99.6 .4

pan 2 504 100.0 .0

Judy’s Branch, Riffle near BR111 (fig. 7)

3/4 19 122 122 21.7 78.3

1/2 12.5 77.5 199.5 35.5 64.5

3/8 9.5 48 247.5 44.0 56.0

4 4.75 82 329.5 58.6 41.4

12 1.7 115.5 445 79.2 20.8

20 .85 44.5 489.5 87.1 12.9

40 .425 44.5 534 95.0 5.0

60 .25 20.5 554.5 98.7 1.3

140 .106 4.5 559 99.5 .5

200 .075 .5 559.5 99.6 .4

pan 2.5 562 100.0 .0

Judy’s Branch, Riffle near BR115 (fig. 7)

3/4 19 22.5 22.5 4.3 95.7

1/2 12.5 45.5 68 13.1 86.9

3/8 9.5 46.5 114.5 22.1 77.9

4 4.75 116 230.5 44.5 55.5

12 1.7 124.5 355 68.5 31.5

20 .85 56.5 411.5 79.4 20.6

40 .425 63.5 475 91.7 8.3

60 .25 32 507 97.9 2.1

140 .106 8 515 99.4 .6

200 .075 .5 515.5 99.5 .5

pan 2.5 518 100.0 .0

Judy’s Branch, Riffle near BR116 (fig. 7)

3/4 19 0 0 0.0 100.0

1/2 12.5 7.5 7.5 2.2 97.8

3/8 9.5 14.5 22 6.4 93.6

4 4.75 50 72 21.0 79.0

12 1.7 102 174 50.7 49.3

20 .85 64 238 69.3 30.7

40 .425 60.5 298.5 86.9 13.1

60 .25 27 325.5 94.8 5.2

140 .106 6 331.5 96.5 3.5

200 .075 1.5 333 96.9 3.1

pan 10.5 343.5 100.0 .0

Appendix A. Weight and coarse-sieve analysis data for bed-sediment samples collected on riffles near bank rods and soil borings in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois, on November 21, 2000—continued.

[mm, millimeters; g, grams; BR, Bank Rod; SB, Soil Boring]

30 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Appendix A  31

Sieve Number Sieve Opening (mm) Material Retained (g) Cumulative Retained (g) Cumulative Percent Retained Percent Finer

Judy’s Branch, Riffle near BR117 (fig. 7)

3/4 19 28 28 5.4 94.6

1/2 12.5 35.5 63.5 12.3 87.7

3/8 9.5 37 100.5 19.5 80.5

4 4.75 117 217.5 42.3 57.7

12 1.7 150.5 368 71.5 28.5

20 .85 57 425 82.6 17.4

40 .425 50.5 475.5 92.4 7.6

60 .25 25 500.5 97.3 2.7

140 .106 7.5 508 98.7 1.3

200 .075 1 509 98.9 1.1

pan 5.5 514.5 100.0 .0

Judy’s Branch, Riffle near BR118 (fig. 7)

3/4 19 53.5 53.5 8.1 91.9

1/2 12.5 77 130.5 19.7 80.3

3/8 9.5 81 211.5 31.9 68.1

4 4.75 95 306.5 46.2 53.8

12 1.7 153.5 460 69.3 30.7

20 .85 68.5 528.5 79.6 20.4

40 .425 74 602.5 90.7 9.3

60 .25 30 632.5 95.3 4.7

140 .106 12.5 645 97.1 2.9

200 .075 2.5 647.5 97.5 2.5

pan 16.5 664 100.0 .0

Judy’s Branch, Riffle near BR119 (fig. 7)

3/4 19 20 20 2.4 97.6

1/2 12.5 34.5 54.5 6.5 93.5

3/8 9.5 19 73.5 8.8 91.2

4 4.75 72.5 146 17.5 82.5

12 1.7 154.5 300.5 36.0 64.0

20 .85 128 428.5 51.4 48.6

40 .425 279.5 708 84.9 15.1

60 .25 67.5 775.5 93.0 7.0

140 .106 25.5 801 96.0 4.0

200 .075 6 807 96.8 3.2

pan 27 834 100.0 .0

Judy’s Branch, Riffle near BR120 (fig. 7)

3/4 19 6.5 6.5 2.1 97.9

1/2 12.5 36 42.5 13.8 86.2

3/8 9.5 28 70.5 22.8 77.2

4 4.75 69 139.5 45.1 54.9

12 1.7 70.5 210 68.0 32.0

20 .85 20.5 230.5 74.6 25.4

40 .425 23.5 254 82.2 17.8

60 .25 32 286 92.6 7.4

140 .106 17 303 98.1 1.9

200 .075 0 303 98.1 1.9

pan 6 309 100.0 .0

Appendix A. Weight and coarse-sieve analysis data for bed-sediment samples collected on riffles near bank rods and soil borings in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois, on November 21, 2000—continued.

[mm, millimeters; g, grams; BR, Bank Rod; SB, Soil Boring]
Sieve Number Sieve Opening (mm) Material Retained (g) Cumulative Retained (g) Cumulative Percent Retained Percent Finer

Judy’s Branch, Riffle near BR122 (fig. 7)

3/4 19 140 140 25.7 74.3

1/2 12.5 40.5 180.5 33.1 66.9

3/8 9.5 30 210.5 38.7 61.3

4 4.75 57 267.5 49.1 50.9

12 1.7 86 353.5 64.9 35.1

20 .85 38.5 392 72.0 28.0

40 .425 63.5 455.5 83.7 16.3

60 .25 55.5 511 93.8 6.2

140 .106 19.5 530.5 97.4 2.6

200 .075 0 530.5 97.4 2.6

pan 14 544.5 100.0 .0

Judy’s Branch, Riffle near BR123-124 (fig. 7), Note: Piece of slag (94.5 g) regarded as a rock

3/4 19 27 27 2.0 98.0

1/2 12.5 43.5 70.5 5.1 94.9

3/8 9.5 48.5 119 8.6 91.4

4 4.75 148 267 19.4 80.6

12 1.7 250.56 517.56 37.6 62.4

20 .85 114 631.56 45.9 54.1

40 .425 143.5 775.06 56.3 43.7

60 .25 565 1,340.06 97.3 2.7

140 .106 22 1,362.06 98.9 1.1

200 .075 3.5 1,365.56 99.2 .8

pan 11 1,376.56 100.0 .0

Appendix A. Weight and coarse-sieve analysis data for bed-sediment samples collected on riffles near bank rods and soil borings in 

Judy’s Branch watershed, in the St. Louis Metro East region in Illinois, on November 21, 2000—continued.

[mm, millimeters; g, grams; BR, Bank Rod; SB, Soil Boring]

32 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Appendix B  33

Appendix B: Soil-boring analysis for Judy’s Branch watershed in the St. Louis 

Metro East region in Illinois 

Definitions for appendix B tables

Abbreviation/Symbol Definition

ft feet

USC Unified Soil Classification

UC or Qu Unconfined Compression tests

CU Consolidated Undrained triaxial shear tests

torvane torvane test

SB soil boring

USGS-IWSC U.S. Geological Survey­­—Illinois Water Science Center

USDA-NRCS U.S. Department of Agriculture—Natural Resources Conservation Service

w water content

% percent

LL liquid limit

PI plasticity index

G specific gravity

γd dry soil specific weight

lb/ft3 pounds per cubic foot

psf pounds per square foot

NP non plastic

c cohesion intercept

c’ effective cohesion intercept

Φ friction angle

Φ’ effective friction angle

Soil group symbols and typical names as established in the Unified Soil Classification (USC)

Soil Group Symbol Definition

ML Inorganic silt and very fine sand, silty or clayey fine sand, or clayey silt with slight plasticity

CL Inorganic clay of low to medium plasticity, gravelly clay, sandy clay, silty clay, lean clay

OL Organic silt and organic silty clay of low plasticity

MH Inorganic silt, micaceous or diatomaceous fine sandy

CH Inorganic clay of high plasticity, fat clay

OH Organic clay of medium to high plasticity

SP Poorly graded sands

SC Sand with plastic clayey fines

SM Sand with non-plastic sitly fines
Table B1. Soil-boring profile and laboratory test results for SB1 collected on September 5, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois. 

Boring Date: 9/5/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

0.65 Light brown silt (loess)

2 Medium brown silt with 

thin sand lens and organic matter

Same as above

Same as above

ML

ML

ML

15.4

6

6

28

26

28

5

4

5

2.65

2.66

4

6

8

10

Same as above CL-ML 15.4 25 5 Streambed level

12

14

16

Medium gray clayey silt CL 21.5 29 8 2.69

18

Silty sand SM 14 17 1

20

Clayey silt w/ silty sand lenses

(fine to medium grained)

SP-SM NP 103

End of boring

22

24

Table B2. Soil-boring profile and laboratory test results for SB2 collected on September 5, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois. 

Boring Date: 9/5/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

2 Light brown silt (loess) ML 22.2 29 4 2.64

4

6

8

10

12

Medium to brown clayey silt with thin

silty sand lenses and

some organic matter

Same as above

Same as above with more sand

CL-ML

ML

ML

CL-ML

ML

ML

25.7

24.8

21.3

14.7

18.2

20.7

25

28

24

24

NP

22

4

4

3

5

3

2.67

2.66

99

105

105

torvane c=1,300 psf

Streambed level

14

16

Gray clayey silt with gray sandy silt

and trace organic carbon

Silty fine to medium fine sand 

with silty clay

CL-ML

SC-SM 18.6

27

22

6

4

2.65

2.67

94 UC

torvane

c=1,238 psf

c=1,250 psf

18

20

22

Medium gray silty clay with

 fine sand and trace organic matter

(stiff overconsolidated)

ML

CL

39.4

26.5

32

34

8

15 End of boring

34  Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Appendix B  35

Table B3. Soil-boring profile and laboratory test results for SB4 collected on September 5, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois. 

Boring Date: 9/5/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

2

4

Cinder, topsoil, brick, gray silt

cobbles and gravels, mixed 

with clay and silt (fill)

ML 22.7 42 15 2.12

6

8

10

Medium brown gray silt

Same as above with slight clay

Gravel cobble and sand lens

CL-ML

ML

CL-ML

17.9

17.4

24.6

23

27

27

4

3

5

2.66

2.54

2.65

12

14

16

18

Clayey silt with fine sand 

and organic matter

Same as above without organic

Same as above

CL

CL-ML

CL-ML

ML

18.4

19.4

25.0

28.9

24

26

26

27

8

7

5

4

2.65

2.65 90 UC

torvane

c=893 psf

c=750 psf

Streambed level

20

22

24

26

28

Silty clay (glacial till)

Same as above

Very stiff to hard silty clay 

(possibly weathered rock)

CL-ML

SC-SM

CL

28.2

18.3

21

26

17

35

6

4

15 2.76

105

Refusal

Table B4. Soil-boring profile and laboratory test results for SB5 collected on September 5, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois. 

Boring Date: 9/5/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

2

4

Medium brown fine silt (loess) 

with fine rootlets

Same as above but lighter brown 

color and some organic matter

ML 21.6 27 3 2.67

6

8

Brownish gray silt with orange

(oxidized) fine-to-medium 

grained sand lenses

Gray silty sand

ML

ML

ML

SM

19.8

22.6

22.5

22

24

25

19

2

2

3

1

2.66

2.65

103

torvane c=500 psf Streambed level

10

12

Silt with thin laminae of fine

sandy silt ML 20.2 21 1 2.66 107

torvane(top/bottom)

CU (remolded)

c=625/750 psf

c=198 psf

Φ=17.6o

Φ’=37.5o

c’=0 psf

End of boring
Table B6. Soil-boring profile and laboratory test results for SB8 collected on September 5, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois.

Table B5. Soil-boring profile and laboratory test results for SB6A collected on September 6, 2000, in Judy’s Branch watershed, in the St. 

Louis Metro East region in Illinois.

Boring Date: 9/6/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

2 Top soil, organic clayey silt ML 27.2 34 10

4

6

Silty clay with rock fragments CL

ML

26.4

29.4

33

29

10

4

2.70

8

10

12

Medium gray clayey silt

Same as above

ML

ML

ML

25.6

24.3

25.2

32

29

29

7

5

5

2.72

2.7

100

torvane

CU

c=1,000 psf

c=182 psf

Φ=15.8o

Φ’=27.8o

c’=0 psf

14

16

Very stiff to hard silty clay

(glacial till)

CL-ML 26.5 28 7 2.69 97 UC

torvane

c=1,145 psf

c=1,375 psf

18

20

Saturated gray clayey silt CL-ML 26.4 25 5 2.67 Streambed level

End of boring

Boring Date: 9/5/2000, USGS-WRD, Urbana Tested by: USDA-NRCS, Lincoln, NE

Depth (ft) Soil Description USC w (%) LL (%) PI (%) G γd, (lb/ft3) Test Results Comments

2

4

Light brown silt with organic rootlets

and oxidized orange silts

ML 9.1 26 3 2.63

6

8

Medium dark gray clayey silt

to silty clay

Same as above with higher clay content

CL 28 30 8 2.63

10 Medium gray clayey silt 

with fine-grained thin sand lens

CL-ML 27.4 26 7

12

14

16

Medium dark gray silty clay

with organic material 

CL-ML

CL

CL-ML

CL

21.7

31

27.4

25.3

24

37

26

26

6

15

7

8

2.67

2.67

103

UC

torvane

torvane

c=936 psf

c=1,000 psf

c=750 psf

Streambed level

18

20

Tan brown clayey silty with

lenses of silty sand and cobbles

(glacial till)

SM 20.9 18 2 2.66

End of boring

36 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Soil 

Boring 

and 

Depth 

(ft)

Grain-Size Distribution in Percent Finer

Particle Size Diameter (mm)

25.40 19.05 12.70 9.525 4.760 2.000 0.840 0.420 0.250 0.105 0.074 0.050 0.020 0.005 0.002

SB1

2.0 100 100 100 100 100 100 100 100 100 100 100 93 35 15 12

6.0 100 100 100 100 100 100 100 100 100 100 100 94 37 16 12

10.0 100 100 100 100 100 100 100 100 100 100 100 93 36 14 9

14.5 100 100 100 100 100 100 100 100 100 100 83 75 30 16 14

17.0 100 100 100 100 100 100 100 100 100 100 89 81 36 19 16

19.0 100 100 100 100 100 100 100 98 78 38 37 37 21 15 14

22.0 100 100 100 100 100 100 99 87 40 9 8 8 2 1 1

SB2

2.0 100 100 100 100 100 100 100 100 100 100 94 86 32 15 10

5.0 100 100 100 100 100 100 100 100 100 100 96 86 32 15 12

7.0 100 100 100 100 100 100 100 100 100 100 100 97 41 16 14

9.5A 100 100 100 100 100 100 100 100 100 100 80 74 27 12 9

9.5B 100 100 100 100 100 100 100 100 100 100 89 81 28 14 14

11.5 100 100 100 100 100 100 99 96 87 67 66 61 22 9 9

13.0 100 100 100 100 100 100 99 93 78 58 57 53 21 10 7

14.0 100 100 100 100 100 100 100 100 100 100 83 80 36 16 13

17.5 100 100 100 100 100 100 94 74 58 49 48 46 20 10 8

19.0 100 100 100 100 100 100 100 100 100 100 78 73 33 19 13

19.5 100 100 100 100 100 100 100 100 100 100 100 95 62 48 35

SB4

4.0 100 100 100 100 100 100 98 91 77 60 58 55 39 27 26

6.5 100 100 100 100 100 100 100 100 100 100 86 75 30 12 12

8.5 100 97 95 94 90 88 83 77 71 60 58 54 31 14 12

10.0 100 100 100 100 100 100 100 100 100 100 98 87 33 15 15

11.5 100 100 100 100 100 100 100 100 100 100 81 75 33 16 14

12.5 100 100 100 98 95 92 87 82 77 70 69 64 30 14 8

15.0 100 100 100 100 100 100 100 100 100 100 96 89 39 16 9

18.5 100 100 100 100 100 100 100 100 100 100 80 72 31 14 10

22.0 100 100 100 100 100 100 100 100 100 100 96 89 41 16 15

25.0 100 100 100 100 100 100 99 96 75 42 41 39 19 11 11

27.0 100 100 100 100 100 100 100 100 100 100 93 86 52 30 26

SB5

2.0 100 100 100 100 100 100 100 100 100 100 96 84 35 15 15

6.0 100 100 100 100 100 100 100 100 100 100 78 71 24 12 12

7.0 100 100 100 100 100 100 100 100 100 100 83 73 27 14 14

9.0A 100 100 100 98 93 80 80 70 54 42 42 41 16 9 9

9.0B 100 100 100 100 100 100 100 100 100 100 89 81 27 12 12

11.0 100 100 100 100 100 100 99 95 86 68 63 54 22 10 10

SB6A

1.5 100 100 100 100 100 100 100 100 100 100 100 96 45 22 20

4.0 100 100 100 100 100 100 100 100 100 100 98 96 48 23 22

6.5 100 100 100 100 100 100 100 100 100 100 100 96 41 16 16

8.0 100 100 100 100 100 100 100 100 100 100 100 96 41 20 20

11.0 100 100 100 100 100 100 100 100 100 100 100 94 38 15 14

13.0 100 100 100 100 100 100 100 100 100 100 100 95 41 17 17

14.0 100 100 100 100 100 100 100 100 100 100 100 100 43 15 12

18.5 100 100 100 100 100 100 100 100 100 100 100 91 35 16 15

SB8

2.0 100 100 100 100 100 100 100 100 100 100 99 90 33 15 14

6.0 100 100 100 100 100 100 100 100 100 100 100 94 47 22 17

10.0 100 100 100 100 100 100 100 100 100 100 98 90 37 15 14

13.0 100 100 100 100 100 100 100 100 100 100 82 75 29 13 13

14.0 100 100 100 100 100 100 100 100 100 100 100 100 56 28 21

15.5 100 100 100 100 100 100 100 100 100 100 96 71 33 15 14

17.0 100 100 100 100 100 100 100 100 100 100 90 81 32 15 13

19.0 100 100 100 100 100 100 97 77 53 53 49 42 20 10 9

Appendix B  37

Table B7. Grain-size distribution for various depths of each soil boring in Judy’s Branch watershed, in the St. Louis Metro East region in 

Illinois. Collected by the USGS-IWSC on September 5-6, 2000. Testing completed by the USDA-NRCS, Lincoln, Nebraska.
38 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
REFERENCES CITED

Casagrande, A., 1948, Classification and identification of soils: Transactions of the American Society of Civil Engineers, 113, p. 901-991.

Terzaghi, K., Peck, R. B., and Mesri, G., 1996, Soil 

mechanics in engineering practice. 3rd edition: 

John Wiley and Sons, Inc., New York, NY, 549 p.

Appendix C: Atterberg Limits for Judy’s Branch watershed in the St. Louis Metro 

East region in Illinois

Figure C1. Plasticity chart developed from samples collected from banks 

and borings throughout Judy’s Branch watershed, in the St. Louis Metro 

East region in Illinois. Refer to table C1 for definition of soil classes. 

Samples plotting above the “A” Line are predominantly clay and those 

below are predominantly silt. 

Soil

Group

Symbol Definition

ML Inorganic silt and very fine sand, silty or 

clayey fine sand, or clayey silt with 

slight plasticity

CL Inorganic clay of low to medium plasticity, gravelly clay, sandy clay, silty 

clay, lean clay

OL Organic silt and organic silty clay of 

low plasticity

MH Inorganic silt, micaceous or diatomaceous fine sandy

CH Inorganic clay of high plasticity, fat clay

OH Organic clay of medium to high plasticity

Table C1. Soil group symbols and typical names 

for cohesive soils as established in the Unified Soil 

Classification (Casagrande, 1948) for soils found in 

the St. Louis Metro East region in Illinois.

Atterberg limits commonly are used to classify 

soils and provide information on the behavior of 

fine-grained soils including liquid limit (LL), plastic 

limit (PL), and plasticity index (PI) as defined in 

Terzaghi and others (1996). The LL is the moisture 

content at which the soil loses its consistency and 

behaves like a viscous fluid. The PL is the moisture 

content at which the soil may plastically deform 

without crumbling. The PI is a measure of how 

much water a soil can absorb before behaving as a 

fluid. The PI is obtained by subtracting the PL from 

the LL; thus, the PI defines the range of moisture 

contents where the soil exhibits plastic behavior. 

The PI and the LL often are correlated to cohesive 

strength. The soil is more compressible and has 

a lower saturated strength at higher values of the 

PI. Soil plasticity is a function of clay content and 

mineralogy. Higher PIs and LLs result from higher 

clay contents. Silt and clay soils with high PIs 

typically have greater proportions of clay minerals 

with thin, platy-shaped particles. The nomenclature 

for soil groups as established in the Unified 

Soil Classification (USC) (Casagrande, 1948) 

is explained in table C1. Soils in the region 

consistently can be classified as low to slight 

plasticity clayey silt, sandy clay, or silty clay 

(fig. C1).

Appendix C  39
40 Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed in the St. Louis Metro East Region in Illinois
Appendix D  41

Bank failures observed during this study were 

categorized as planar or rotational by their mode of 

failure as indicated by the shape of the failure sur- face (Thorne and others, 1997, and Thorne, 1998). 

Both failure types are observed in Judy’s Branch 

watershed and the St. Louis Metro East region in 

Illinois. Pop-out failures are also discussed here. 

The relation of type of failure and soil material as 

noted in the following text was concluded from field 

observations of banks in the Judy’s Branch water- shed.

Planar failures generally occur in non-cohesive 

to slightly cohesive soils with slight plasticity. Planar failures sometimes are observed to begin with 

the development of a tension crack at the top of the 

bank. Size of failure wedge heights are on the order 

of 75 to 90 percent of the bank height, and their 

lateral dimension along the stream ranged from 

5 to 10 ft. The depth of the failure wedge ranges 

from 3 to 8 ft from the failed bank surface. When a 

planar failure occurs, material from the top of the 

banks becomes redeposited at the toe, temporarily 

buttressing the bank. With time, the wedge may 

crumble and become easily detached and washed 

away by the river flow. The mode of failure was 

generally observed on silty alluvial deposits.

Two types of rotational failures were classified 

in the St. Louis Metro East region: deep and shal- low. Deep rotational failures are common in soft 

deposits with high plasticity indexes (MH or CH). 

High plasticity deposits are not common in the St. 

Louis Metro East region and, therefore, deep rota- tional failures were not considered in this study. 

Shallow rotational failures occur in low to 

medium plasticity soils and their orientation and 

extent depends on the presence of weak planes, discontinuities, zones of high infiltration rates, tree surcharge, and other factors. Shallow rotational failure is a process in which the shear stress increases 

because of prolonged wetting, loss of negative porewater pressures and the shear strength becomes 

degraded by progressive displacement, and remolding of the soil particles along the shearing plane 

and the plane becomes polished. Once sufficient 

displacement has occurred on an unstable bank, 

the shear strength available on the plane will be the 

residual shear strength (the shear strength between 

the polished failure planes). Displacements and 

distortion of the whole mass also will open new 

paths for easy infiltration of water through the 

failure surface; thus, allowing rapid saturation and 

decrease in shear strength because of an increase in 

positive pore water pressure. Once the shear stress 

overcomes the weakened shear strength, it dislo- cates and displaces until it reaches a new state of 

equilibrium. The residual strength for low plastic- ity medium to soft soils, as the ones found during 

this study, is for practical purposes the same as the 

remolded or fully softened shear strength (Stark and 

Eid, 1997, and Terzaghi and others, 1996).

Shallow rotational failures are common on 

Judy’s Branch watershed and other streams in the 

St. Louis Metro East region. The contact of alluvium over glacial till, when present, is a weak zone 

where failure surfaces result. In some cases, it 

was observed that the failure plane had penetrated 

slightly into the till; this penetration was more common if the glacial till was highly weathered. 

Lastly, fill deposits in the area commonly were 

unstable. Generally, fill deposits are observed to 

fail as planar failures and soil falls (occur when 

a stream undercuts the toe of a bank and the soil 

above falls into the river (Thorne and others, 1997 

and Thorne, 1998)). These observations are supported in that these fill deposits are loose and are 

non-cohesive. When material from planar failure or 

soil falls accumulates at the bottom of the bank covering a sand lens, the seepage through the sand lens 

may cause the soil to pop out or become detached 

from the bank face. 

REFERENCES CITED

Stark, T.D., and Eid, H. T., 1997, Slope stability 

analyses in stiff fissured clays: Journal of Geo- technical and Geoenvironmental Engineering, 

American Society of Civil Engineers, v. 123, 

no. 4, 335-342.

Terzaghi, K., Peck, R. B., and Mesri, G., 1996, Soil 

mechanics in engineering practice. 3rd edition: 

John Wiley and Sons, Inc., New York, NY, 549 p.

Thorne, C.R., Hey, R.D., and Newson, M.D., 1997, 

Applied fluvial geomorphology for river engineering and management: John Wiley and Sons, 

Chichester, U.K., 376 p.

Thorne, C.R., 1998, Stream reconnaissance handbook: John Wiley and Sons, Chichester, U.K., 

133 p.

Appendix D: Bank-failure types for Judy’s Branch watershed in the St. Louis 

Metro East region in Illinois

Straub, T.D., and others—Suspended-Sediment Yields and Stream-Channel Processes on Judy’s Branch Watershed

in the St. Louis Metro East Region in Illinois—Scientific Investigations Report 2006-5016

Science Center Director

USGS Illinois Water Science Center

1201 W. University Ave., Suite 100

Urbana, IL 61801

http://il.water.usgs.gov