S E D I M E N T 

T R A N S P O R T 

IN THE 

LOWER MISSOURI 

AND THE 

CENTRAL MISSISSIPPI 

RIVERS 

JUNE 26 THROUGH SEPTEMBER 14 

9 9 3 

U.S. GEOLOGICAL SURVEY CIRCULAR 1120-I 

Click here to return to USGS publications 
Front cover-View of Highway 67, West Alton, Missouri 

(Srenco Photography, St . Louis, Mo.) 

Back cover-View of Spirit of St . Louis Airport, 

Chesterfield, Mo. (Srenco Photography, 

St . Louis, Mo.) 

Field Hydrologist making streamflow 

measurements (U .S . Geological Survey) 
SEDIMENT TRANSPORT IN THE LOWER MISSOURI AND€

THE CENTRAL MISSISSIPPI RIVERS, JUNE 26 THROUGH€

SEPTEMBER 14, 1993€

By Robert R . Holmes, Jr. 

Floods in the Upper Mississippi River Basin, 1993€

U.S. GEOLOGICAL SURVEY CIRCULAR 1120-I 
U.S .DEPARTMENT BRUCE BABBITT, OF THE Secretary€ INTERIOR Denver, CO 80225 

U .S . GEOLOGICAL SURVEY€

GORDON P. EATON, Director 

Any use of trade, product, or firm names in this 

publication is for descriptive purposes only and does 

not imply endorsement by the U .S . Government 

UNITED STATES GOVERNMENT PRINTING OFFICE : 1996 

Free on application to the 

U.S . Geological Survey Information Services 

Box 25286, Federal Center 
FOREWORD 

During spring and summer 1993, record flooding inundated much of the upper Mississippi River 

Basin. The magnitude of the damages-in terms of property, disrupted business, and personal traumawas unmatched by any other flood disaster in United States history . Property damage alone is expected 

to exceed $10 billion. Damaged highways and submerged roads disrupted overland transportation 

throughout the flooded region. The Mississippi and the Missouri Rivers were closed to navigation 

before, during, and after the flooding . Millions of acres of productive farmland remained under water for 

weeks during the growing season. Rills and gullies in many tilled fields are the result of the severe erosion that occurred throughout the Midwestern United States farmbelt. The hydrologic effects of extended 

rainfall throughout the upper Midwestern United States were severe and widespread. The banks and 

channels of many rivers were severely eroded, and sediment was deposited over large areas of the basin's 

flood plain. Record flows submerged many areas that had not been affected by previous floods. Industrial and agricultural areas were inundated, which caused concern about the transport and fate of industrial chemicals, sewage effluent, and agricultural chemicals in the floodwaters . The extent and duration 

of the flooding caused numerous levees to fail . One failed levee on the Raccoon River in Des Moines, 

Iowa, led to flooding of the city's water treatment plant. As a result, the city was without drinking water 

for 19 days. 

As the Nation's principal water-science agency, the U.S. Geological Survey (USGS) is in a unique 

position to provide an immediate assessment of some of the hydrological effects of the 1993 flood. The 

USGS maintains a hydrologic data network and conducts extensive water-resources investigations nation 

wide. Long-term data from this network and information on local and regional hydrology provide the 

basis for identifying and documenting the effects of the flooding. During the flood, the USGS provided 

continuous streamflow and related information to the National Weather Service (NWS), the U.S . Army 

Corps of Engineers, the Federal Emergency Management Agency (FEMA), and many State and local 

agencies as part of its role to provide basic information on the Nation's surface- and ground-water 

resources at thousands of locations across the United States . The NWS has used the data in forecasting 

floods and issuing flood warnings. The data have been used by the Corps of Engineers to operate water 

diversions, dams, locks, and levees. The FEMA and many State and local emergency management agencies have used USGS hydrologic data and NWS forecasts as part of the basis of their local flood-response 

activities . In addition, USGS hydrologists are conducting a series of investigations to document the 

effects of the flooding and to improve understanding of the related processes. The major initial findings 

from these studies will be reported in this Circular series as results become available . 

U.S . Geological Survey Circular 1120, Floods in the Upper Mississippi River Basin, 1993, consists of individually published chapters that will document the effects of the 1993 flooding . The series 

includes data and findings on the magnitude and frequency of peak discharges; precipitation ; water-qual 

ity characteristics, including nutrients and man-made contaminants; transport of sediment; assessment of 

sediment deposited on flood plains ; effects of inundation on ground-water quality ; flood-discharge volume; effects of reservoir storage on flood peaks; stream-channel scour at selected bridges ; extent of floodplain inundation; and documentation of geomorphologic changes. 

A4,cxle~41V'44 

Director 

Foreword III 
CONTENTS


Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III


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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Methods for data collection and computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Sediment transport during the 1993 flood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Suspended-sediment concentrations and loads and bedload estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Accuracy of suspended-sediment concentrations and loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Particle size of suspended-sediment and bed-material samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Sediment loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Mixing of sediment from the Missouri and the Mississippi Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Storage and flux of sediment in the lower Missouri and the central Mississippi River Basin . . . . . . . . . . . . . . . . . . . . 18 

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

References cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 

FIGURES 

1 . Map showing location of water-discharge and sediment-data-collection stations on the lower 

Missouri and the central Mississippi Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

2.-9. Graphs showing: 

2. Relation between water discharges and suspended-sediment concentrations for the 

Mississippi River below Grafton, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

3. Relation between water discharges and suspended-sediment concentrations for the Missouri 

River at Hermann, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

4. Water-discharge hydrographs and suspended-sediment-sample concentrations for the 

Mississippi River from June 26 through September 14, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

5. Relation between water discharge and bedload determined by using the Meyer-Peter and 

Muller, the Modified Einstein, and the Schoklitsch bedload equations for selected sediment 

data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

6. Mean particle-size distributions for multivertical suspended-sediment cross-section samples 

collected during the 1993 flood rise at the sediment data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

7. Mean particle-size distribution for multivertical suspended-sediment cross-section samples 

collected from the Mississippi River at Thebes, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

8. Bed-material particle-size distribution for selected sediment data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . 15 

9. Water-discharge and suspended-sediment-concentration hydrographs for two floods on the 

Mississippi River at Thebes, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

10. Photograph showing the Mississippi River at St . Louis, Missouri, July 30, 1993, looking west, 

showing the lateral variability in sediment concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

11 . Graph showing lateral distribution of suspended-sediment concentrations for the Mississippi 

River at St. Louis, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

12. Photograph showing view of the sand deposited on the Missouri River flood plain near the 

junction of the Missouri and the Mississippi Rivers, November 8, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

13 . Graphs showing streambed cross sections for the Mississippi River at Chester, Illinois . . . . . . . . . . . . . . . . . . . . . . . . . 22 

Contents V 
TABLES 

1 . U.S . Geological Survey sediment data-collection stations on the lower Missouri and the central 

Mississippi Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

2. Concentration and particle-size distribution for multivertical suspended-sediment samples 

collected during the 1993 flood. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

3 . Particle-size distribution for bed-material samples collected from July 7 through August 12, 1993, at 

selected sediment data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

4. Suspended-sediment loads and estimated bedloads at sediment data-collection stations from 

June 26 through September 14, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

5 . Minimum and maximum values of miscellaneous sediment, hydraulic, and slope data collected 

during multivertical sediment sampling and water-discharge measurements, June 26 through 

September 14, 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

6. Suspended-sediment loads and volumes of water discharge for the 1951, 1973, and 1993 flood 

periods on the Missouri River at Hermann, Missouri, and the Mississippi River at St . Louis, 

Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

7. Median daily suspended-sediment concentrations and loads for the 1993 flood and the period of 

record at the daily sediment data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

8. 1993 flood and annual sediment load at the sediment data-collection stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

CONVERSION FACTORS AND VERTICAL DATUM 

Multiply 

millimeter (mm) 

meter (m) 

square meter (m'`) 

kilometer (km) 

metric ton (t) 

metric ton per day (t/d) 

meter per second (m/s) 

cubic meter per second (m3/s) 

hectare (ha) 

cubic hectometer (hm3) 

By 

0.03937 

3.281 

10 .76 

0.6214 

1.102 

1 .102 

3.281 

35 .31 

2.471 

8.107 

To obtain 

inch 

foot 

square foot 

mile 

short ton 

short ton per day 

foot per second 

cubic foot per second 

acre 

acre-foot 

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)-a geodetic 

datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called 

Sea Level Datum of 1929 . 

VI Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
Sediment Transport in the Lower Missouri and€

the Central Mississippi Rivers, June 26 through€

September 14, 1993 

By Robert R. Holmes, Jr. 

Abstract 

Sediment data were collected at five sites in 

`he lower Missouri and the central Mississippi 

"'ivers during the 1993 flood. Bedloads were indi 

-ectly estimated to be generally less than 5 percent of the suspended-sediment load for this 

period . Suspended-sediment loads for the 1993 

`food generally were less than during previous 

goods in 1951 and 1973, which is thought to be 

attributable to the trapping of sediment in the resi~,rvoirs in the Missouri River Basin that have been 

operational since 1953 and the depletion of sedi-

-nent supply and dilution of sediment concentra-

`ion by the large 1993 flood volumes. 

Sediment apparently went into storage, 

either in the channel or the flood plain, upstream 

`rpm St. Louis, Missouri, because the total sus 

-)ended sediment transported by the Mississippi 

Iiver past St. Louis was 22 million metric tons 

Iess than that transported past the two upstream 

-?diment stations-below Grafton, Illinois, and at 

=Iermann, Missouri. The storage of sediment was 

-partly verified by the massive amounts of newly 

deposited sediments on the flood plains . 

Anonhomogenous mixture of water is 

-)resent at St. Louis, which is 24 kilometers down-

,tream from the normal junction of the Missouri 

.and the Mississippi Rivers . During the 1993 

good, the suspended-sediment concentration var-

~ed from one shoreline to the other by a factor of 

-iearly five . Aerial photography taken on July 25 

; ndicates the river became well mixed 88 kilome-

`ers downstream from the normal junction of the 

`wo rivers . Several days before and after July 25, 

,he junction of the two rivers was 32 kilometers 

upstream from the normal junction . 

The dynamics of sediment transport and 

movement were exemplified by 4 meters of 

channel-bed scour from July 12 through July 20 

at the Mississippi River at Chester, Illinois. The 

channel-bed changes generally followed a pattern 

of scouring during the flood rise followed by 

channel-bed aggradation during the recession. 

INTRODUCTION 

Flooding in the upper Mississippi River Basin 

in 1993 will long be remembered for the magnitude 

and duration of the river stages and discharges and the 

sediment deposition in the flood plains . Record peak 

discharges were reported at 40 streamflow-gaging stations operated by the U.S . Geological Survey (USGS; 

Parrett and others, 1993) as the Mississippi River at 

St. Louis, Missouri, was continuously above flood 

stage for 81 days from June 26 through September 14. 

The record flooding mobilized, transported, and 

deposited large quantities of sediment throughout the 

upper Mississippi River Basin. The Mississippi River 

system transports more sediment than any other river 

in North America (Meade and others, 1990). High 

quantities of sediment affect river navigation and 

operation of reservoirs and water-treatment plants . 

Sediments can adsorb and transport numerous contaminants, such as pesticides and toxic metals, that could 

be a problem for public health . To monitor the transport of sediment, the USGS operates data-collection 

stations for sediment transport at five sites on the 

lower Missouri and the central Mississippi Rivers . 

Purpose and Scope 

This report summarizes information on sediment concentrations, loads, and size distributions in 

the lower Missouri and the central Mississippi Rivers 

during the 81-day flood period from June 26 through 

Introduction 1 
September 14, 1993. Data were collected at five existing USGS sediment data-collection stations (hereafter 

referred to as "sediment stations") during the flood 

(fig . 1 ; table 1) . The data collected consist of water 

discharge, velocity, channel geometry, water-surface 

slope, detailed multivertical cross-section suspendedsediment concentrations, daily single-vertical suspended-sediment concentrations, and particle-size distributions of bed material and suspended sediment. 

Suspended-sediment concentrations and loads at the 

five sediment stations are analyzed in relation to temporal and spatial aspects of sediment transport . Bedload was estimated by applying theoretical equations 

to hydraulic and geometric data collected onsite during streamflow discharge measurements. In addition, 

sediment data from the 1993 flood are compared with 

those from the 1951 and the 1973 floods on the MisEXPLANATION 

07022000 

sissippi River and from the period of record at each 

station. 

Methods for Data Collection and Computation 

Two types of sediment stations, daily and periodic, are operated by the USGS. The type of station is 

defined by the frequency and quantity of data col 

lected. A daily sediment station has daily concentration and load published when, according to Porterfield 

(1972, p. 1), "sufficient determinations of sediment 

concentration and water discharge are obtained to justify computation of daily sediment discharge. The end 

product is a tabulation of daily mean concentration, 

suspended-sediment discharge (load), and periodic 

determinations of particle-size distribution of suspended sediment and bed material ." The USGS operWater-discharge and sediment-data-collection station and number 

-05587450 Water-discharge station and number 

Figure 1 . Location of water-discharge and sediment data-collection stations on the lower Missouri and 

the central Mississippi Rivers. 

2 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
-able 1 . U.S . Geological Survey sediment data-collection stations on the lower Missouri and the central Mississippi Rivers 

CY, current year] 

number (fig . 1) milel published2 

05587455 Mississippi River below Grafton,1113 . . . . . . . . . . . . . . . . . . . . . . 214.6 March 1989 to CY Daily. 4 

06934500 Missouri River at Hermann, Mo . . . . . . . . . . . . . . . . . . . . . . . . . . 97 .9 April 1948 to CY Periodic . 

07010000 Mississippi River at St. Louis, Mo . . . . . . . . . . . . . . . . . . . . . . . 180.0 . . . . . do . . . . . . . . . . Daily. 

07020500 Mississippi River at Chester, Ill . . . . . . . . . . . . . . . . . . . . . . . . . . . 109.9 August 1980 to CY Do. 

07022000 Mississippi River at Thebes, Ill . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 .7 October 1980 to CY Do. 

Station Station River Period of record Type of record 

'River mile is measured from the junction of the Missouri and the Mississippi Rivers for the Missouri River stations and from the Ohio River inflow for 

he	Mississippi River stations . 

` Type of record published can be either daily or periodic. Daily stations have data collected frequently enough to define the daily sediment concentration 

,and load, whereas periodic stations have data collected less frequently, and usually only load estimates are published for time spans of months or longer. 

3 Water discharge was measured at the Mississippi River at Grafton, station number 05587450 . 

4 Although this is a daily record station, daily samples could not be collected at this station . Therefore, most of the 1993 flood period suspended-sedinent loads was computed by transport relations . 

ates four daily sediment stations on the central 

Mississippi River (table 1). 

Data collected at a periodic sediment station are 

insufficient for daily load computation, but may be 

adequate to warrant estimation of sediment loads for 

months or longer periods . These estimates are made 

by the use of sediment-transport curves, which relate 

either suspended-sediment load or concentration to 

water discharge (Glysson, 1987) . The USGS operates 

one periodic sediment station on the lower Missouri 

River at Hermann, Missouri (table 1). 

All suspended-sediment data were collected 

according to methods described in Edwards and Glysson (1988) . At a USGS daily sediment station, sus 

pended-sediment samples generally are collected once 

daily (or more frequently) by a local contract observer 

(hereafter referred to as "observer") at a single location in the river. Multivertical cross-section samples 

(hereafter referred to as "cross-section sample") also 

are collected to "adjust" the single vertical observer 

samples . These cross-section samples are collected by 

using either an equal discharge increment method 

(EDI) or an equal width method (EWI; Edwards and 

Glysson, 1988) at 5 to 10 locations across the stream. 

From these data, the daily mean concentration and 

daily suspended-sediment load are computed by methods described in Porterfield (1972). 

Conditions prevented the collection of daily 

samples at the Mississippi River below Grafton, Illinois, during the 1993 flood. Therefore, the EWI cross 

section data, which were collected periodically, and 

the data from a few samples collected by the observer 

are the only sediment data available for this sediment 

station during the 1993 flood. A suspended-sediment 

transport relation (hereafter referred to as "curve") 

was developed by using the data from the cross-section samples collected during the flood and the sediment samples collected before the flood (fig. 2). These 

data, which are shown with the date of collection next 

to the sample point, indicate a looped curve (hereafter 

referred to as "hysteresis") (fig . 2) . This hysteresis is 

more exaggerated than normal because of the depletion and dilution of sediment during the 1993 flood, 

which will be discussed in the section entitled "Sediment Loads." By using this curve, an estimate was 

made of the suspended-sediment concentration for 

each day during the flood period. The suspended-sediment load for the flood then was computed as the sum 

of all the daily loads that had been determined as the 

product of the estimated concentrations, water discharge, and a conversion factor for tons per day. The 

daily suspended-sediment loads before the flood 

period were determined by methods described in Porterfield (1972) for daily sediment stations . 

Since 1948, monthly EDI cross-section samples 

have been collected at the Missouri River at Hermann 

by the USGS or the U.S . Army Corps of Engineers . 

During the 1993 flood, EDI samples were collected 

more frequently by the USGS. A curve was developed 

that related suspended-sediment concentration to 

water discharge. Because of depletion and dilution of 

sediment, the 1993 flood data plot below the straight 

line on the basis of previously collected data, and, 

therefore, a different line was drawn by visual fit 

(fig . 3) . Daily suspended-sediment concentrations 

Methods for Data Collection and Computation 3 
cc


w 1,000


J
 +


Looped curve (hysteresis) - Dashed a - 500 where approximate + 

+ Samples collected from January 

s 1990 through June 1993 +++ +

0 

July 5, 1993 

(7 July 5, 1993 

J ® Samples collected from ++ June through August 1993 + 

z 200 and date of collection +


z


O June 2, 1993 July 15, 1993


F


Cc 100 

+ + + July 17, 1993


t-


z + July 19, 1993
 w


z August 11, 1993 ® July 23, 1993


O 50 z 

w ® August 4, 1993 

+ 0 

w 

0 

w 20 

zz 

w 

a 

10 

100 1,000 10,000 100,000 

WATER DISCHARGE, IN CUBIC METERS PER SECOND 

Figure 2. Relation between water discharge and suspended-sediment concentration for the 

Mississippi River below Grafton, Illinois . 

were estimated from this curve. The suspendedsediment load for the flood period was determined to 

be the sum of all the daily loads that were computed as 

the product of the daily estimated mean suspendedsediment concentrations, the daily mean water discharge, and a conversion factor for tons per day. 

During the flood, USGS personnel collected 

daily suspended-sediment samples from the Mississippi River at St. Louisl at two longitudinal locations 

(one each near the Missouri and the Illinois shorelines) 

to account for the incomplete mixing of the Missouri 

River inflow 24 km upstream. Cross-section samples 

usually consisted of 10 verticals collected by using the 

EDI method. However, during the flood, one crosssection sample was collected from the front of a barge 

tow as a nine-vertical EWI sample because the monorail system used to collect the samples was disabled. 

The Mississippi River sediment stations at 

Chester and Thebes, Illinois, are daily sediment stations ; suspended-sediment samples are collected at 

least daily by observers at a single location in the 

river. During the 1993 flood, samples were collected 

twice daily at Thebes and three times daily at Chester 

'During normal flow conditions, USGS personnel collect the 

two location samples weekly because use of contract observers at 

this station is not feasible . From a combination of the samples collected every 2 weeks, cross-section samples collected every 2 

months, and the daily turbidity records from two nearby waterworks intakes (one on each side of the river), a daily record is 

computed. 

by the observers . Cross-section samples were collected by using the EDI method. 

Bed-material samples were collected according 

to methods described in Edwards and Glysson (1988). 

Suspended-sediment samples were collected from the 

Mississippi River at Chester, Illinois . by using a US P-63 

sampler suspended from a specially designed boom-hoist 

car. 

Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
W 10,000

F

J -Transport relation 

W 

a + Samples collected January 1985 + 

through May 1993 

2 ++ + (7 " Samples collected July

J through September 1993 

+

+ + 

" + 

+ 

z 1,000 + + 

0 + 

+ + +++ + + 

F + + +
 z + + +
 U


O +
 U


F

Z 100


W


O


W


O
W


Z
W


a


10,000 100,000 

WATER DISCHARGE, IN CUBIC METERS PER SECOND 

Figure 3. Relation between water discharge and suspended-sediment concentration for the 

Missouri River at Hermann, Missouri. 

Most bed-material samples from the 1993 flood were 

collected from the bow of a boat because of the 

extreme depths and velocities. 

Particle size was determined on all cross-section 

suspended-sediment and bed-material samples collected 

during the flood [tables 2 and 3]. For suspended 

sediment cross sections collected by using the EDI 

method, concentration and size were analyzed for each 

vertical sampled . For those suspended-sediment and 

bed-material cross sections collected by using the EWI 

method, the samples from all the vertical sections 

were composited for a single analysis of size; the concentration of the composited suspended-sediment 

samples also was determined. 

Bedload was not measured directly during this 

flood because accurate measurements in the Missouri 

and the Mississippi Rivers are not possible at this time 

under such conditions with existing bedload samplers. 

These inaccuracies are, for the most part, the result of 

the extreme temporal and spatial variability of bedload 

transport and the distortions of natural flow fields 

when the bedload sampler moves near the bed (Meade 

and others, 1990). The measurement inaccuracies are 

increased during the sampling conditions (high velocities and large depths) on the Missouri and the Mississippi Rivers during the flood. 

No direct determination of bedload could be 

made during the 1993 flood, but estimates of bedload 

were made for each of the five sediment stations . 

However, because of the lack of onsite verification 

data, no single equation could be used to make accurate estimates of the bedload for such a large river system. The following equations were used: Meyer-Peter 

and Muller (Meyer-Peter and Muller, 1948), Modified 

An attempt was made to collect bedload samples for the 

Mississippi River at St. Louis, Missouri, by using an 

experimental sampler designed at the U.S. Geological 

Survey Cascades Volcano Observatory, Vancouver, 

Washington . The sampler was suspended from a crane on 

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

Pathfinder. 

Methods for Data Collection and Computation 5 
-- -- -- -- -- --

-- -- -- -- -- --

-- -- -- -- -- --

-- -- -- -- -- --

Table 2. Concentration and particle-size distribution for multivertical suspended-sediment samples collected during the 1993 flood 

[Q, waterdischarge; particle diameter, in millimeters; m; /s, cubic meters per second; m, meters ; mg/L, milligrams per liter; --, no data] 

Suspended Percentage of sample smaller than particle diameter 

Q Distance from 

Date Time (m3/S) left shoreline 

(m) 

sediment 

concentration 

(mg/L) 

2 1 0.5 0.25 0.125 0.062 0.031 0.016 0.008 0.004 0.002 0.001 

Mississippi River below Grafton, Illinois 

07-15-93 1514 12,100 Composite. . . 130 100 100 100 99 97 96 96 93 89 79 67 55 

07-17-93 1120 13,900 . . . .do. . . . . 94 100 100 100 98 96 95 94 90 83 72 60 46 

07-19-93 1228 14,700 . . . .do. . . . . 74 100 100 100 100 99 99 

07-23-93 1045 16,200 . . . .do. . . . . 63 100 100 100 99 98 97 

08-04-93 1640 16,600 . . . .do. . . . . 42 100 100 100 97 82 79 

08-11-93 1235 11,500 . . . .do. . . . . 65 100 100 97 85 81 79 

Missouri River at Hermann, Missouri 

07-07-93 1430 11,400 239 1,430 100 100 95 89 64 62 60 51 45 39 32 25 

285 1,541 100 100 100 90 68 59 57 49 42 37 30 24 

338 1,630 100 700 95 83 60 57 55 47 41 35 29 23 

383 1,660 100 100 88 75 63 56 54 46 40 35 28 22 

444 1,400 100 100 97 94 74 66 64 55 48 41 34 27 

07-13-93 1030 9,290 338 1,150 100 100 100 91 69 59 58 57 55 51 45 37 

392 1,150 100 100 97 90 65 58 58 56 54 50 44 36 

437 1,210 100 100 95 85 56 56 55 54 52 48 42 35 

498 1,080 100 100 95 86 64 62 61 59 57 53 47 38 

07-16-93 1740 14,300 291 937 100 100 100 89 67 63 62 59 54 49 40 32 

390 971 100 100 100 84 66 64 63 60 55 50 41 32 

443 1,070 100 100 100 83 54 54 53 51 46 42 35 27 

504 856 100 100 100 89 68 68 67 64 58 53 44 34 

07-17-93 1440 11,800 291 724 100 100 98 96 73 69 68 67 63 57 49 34 

337 874 100 100 95 84 63 57 56 55 52 47 40 28 

390 994 100 100 94 80 54 50 50 48 46 41 36 25 

443 1,180 100 100 95 83 60 52 51 50 47 43 37 26 

504 878 100 100 94 82 62 56 55 53 51 46 40 28 
-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

-- -- -- -- -- -- -- -- -- --

-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

07-30-93 1325 18,200 297 1,980 100 100 100 100 88 88 86 74 63 54 46 40 

342 1,960 100 100 99 97 91 89 87 75 64 54 47 40 

396 2,250 100 100 95 91 82 78 76 66 56 48 41 35 

449 2,410 100 100 92 84 75 72 71 61 51 44 38 32 

502 2,030 100 100 97 94 87 86 84 73 61 52 45 39 

08-01-93 1445 19,900 297 1,320 100 100 100 96 89 89 86 73 60 48 36 23 

342 1,340 100 100 98 95 88 87 84 71 59 47 35 23 

396 1,460 100 100 96 93 84 82 79 67 55 44 33 21 

449 1,600 100 100 93 88 76 74 71 60 50 40 30 19 

502 1,390 100 100 98 94 85 84 81 68 57 45 34 22 

08-19-93 1230 6,230	 134 631 81 

180 712 73 

233 805 59 

287 597 67 

400 610 72 

Mississippi River at St. Louis, Missouri 

07-07-93 1200 19,100 97 195 100 100 100 96 93 90 89 84 77 68 57 44 

148 220 100 100 100 100 100 95 94 88 82 72 60 47 

187 228 100 100 100 100 100 97 96 90 83 74 61 48 

219 644 100 100 97 90 77 72 71 67 62 55 45 35 

277 836 100 100 97 89 79 75 74 70 64 57 47 37 

0 324 943 100 100 100 91 78 75 74 70 64 57 47 37 

372 908 100 100 98 94 86 84 83 78 72 64 53 41 

0 404 863 100 100 99 97 91 89 88 83 77 68 56 44 

m 477 1,010 100 100 99 94 88 87 86 81 75 66 55 43 0

0 

533 921 100 100 100 99 97 95 94 88 82 72 60 47

m
0


0 08-06-93 0930 26,200 Composite . . . 522 100 98 95 81 69 63 62 62 61 56 47 39


d 09-02-93 1310 12,900 94 121 86 

CL 143 108 90 

0 180 125 81 

227 141 82 

m 256 155 82 

296 148 73 

344 255 74 

390 355 73 
--

--

--

--

--

--

--

--

--

--

-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

-- -- -- -- --

Table 2. Concentration and particle-size distribution for multivertical suspended-sediment samples collected during the 1993 flood-Continued 

Suspended Percentage of sample smaller than particle diameter 

Distance from sediment Q Date Time (m3/s) left shoreline concen­

(m) tration 

(mg/L) 

454 530 

518 589 

07-21-93 1200 26,300 75 220 

130 247 

168 253 

200 302 

245 380 

270 319 

335 285 

392 240 

453 207 

532 216 

07-30-93 1730 25,500 195 290 

265 396 

359 234 

495 209 

08-05-93 1125 26,700 100 425 

219 352 

264 535 

365 364 

494 344 

08-12-93 1606 24,000 98 115 

185 180 

263 236 

365 146 

539 122 

2 1 0.5 0.25 0.125 0.062 0.031 0.016 0.008 0.004 0.002 0.001 

Mississippi River at St. Louis, Missouri-Continued 

69 

76 

Mississippi River at Chester, Illinois 

94 94 84 78 69 57 45 

100 100 100 98 90 87 87 77 72 64 53 41 

100 100 100 100 86 83 83 74 68 61 51 39 

100 100 100 93 78 71 71 63 59 52 43 34 

100 100 100 96 69 59 59 53 49 43 36 28 

100 100 100 88 73 68 68 61 56 50 41 32 

100 100 96 89 77 74 74 66 61 54 45 35 

100 100 100 96 90 88 88 78 73 65 54 42 

99 98 88 82 73 60 47 

96 96 85 79 71 59 46 

100 100 100 96 78 73 72 63 58 50 40 29 

100 100 100 87 60 56 55 49 45 39 31 22 

100 100 100 96 92 91 90 79 73 63 50 36 

98 97 85 78 68 53 39 

100 100 100 97 84 80 79 74 68 60 46 34 

100 100 100 98 96 95 94 88 81 71 55 40 

100 100 98 95 70 63 62 59 54 47 36 26 

100 100 99 97 93 91 90 85 78 68 52 38 

100 100 100 98 97 97 96 90 83 72 56 41 

98 98 93 84 73 59 44 

100 100 98 94 69 65 65 61 56 48 39 29 

100 100 100 92 57 50 50 47 43 37 30 22 

100 100 94 87 80 78 78 74 67 58 47 35 

94 94 89 80 70 57 42 
Mississippi River at Thebes, Illinois 

07-18-93 1426 23,800	 195 324 100 100 100 99 88 85 84 84 82 77 69 57 

277 352 100 100 100 98 82 78 77 77 75 71 63 52 

341 414 100 100 98 94 72 67 66 66 65 61 54 45 

446 408 100 100 100 92 72 67 66 66 65 61 54 45 

494 423 100 100 100 98 70 65 64 64 63 59 53 44 

533 540 100 100 100 94 55 51 50 50 49 46 41 34 

567 431 100 100 99 96 69 64 63 63 62 58 52 43 

610 476 100 100 99 97 63 58 57 57 56 53 47 39 

695 325 100 100 100 98 88 85 84 84 82 77 69 57 

07-21-93 1920 25,300 195 288 100 100 98 96 88 85 83 76 69 63 54 43 

277 319 100 100 100 98 81 76 74 68 62 56 48 39 

341 394 100 100 97 90 66 62 61 55 51 46 39 32 

393 378 100 100 96 89 71 66 65 59 54 49 42 34 

446 550 100 100 99 85 49 44 43 39 36 33 28 22 

494 465 100 100 100 96 57 52 51 46 42 38 33 27 

533 1,060 100 100 98 82 58 23 23 20 18 17 15 12 

567 499 100 100 98 90 56 51 50 45 42 38 32 26 

610 429 100 100 98 97 62 56 55 50 46 41 36 29 

695 262 100 100 98 98 94 91 89 81 75 67 58 46 

08-2-93 1610 25,100 247 437 100 100 98 94 91 90 90 84 76 65 50 35 

c 356 487 100 100 100 98 90 89 89 83 76 65 49 34 0. 469 514 100 100 99 96 79 76 76 71 65 55 42 29 

° 556 415 100 100 100 99 95 94 94 87 80 68 52 36 

° m 665 495 100 100 100 98 82 79 79 73 67 57 43 30 0

° 

08-06-93 1645 27,400 356 408 100 100 97 95 82 79 77 72 66 58 47 34 ° 0 469 423 100 100 100 92 80 78 76 71 65 57 46 34 3 

556 491 100 100 100 97 71 67 66 61 56 49 40 29 

0 665 416 100 100 100 97 82 78 76 71 65 57 46 34 

° 3

.°c 

ro 
i

0 

a 

3 

m

0 

w Table 3. Particle-size distribution for bed-material samples collected from July 7 through August 12, 1993, at selected sediment data-collection stations 

O [Q, water discharge; m;/s, cubic meters per second ; particle diameter, in millimeters] 

3 

w 

m 0 Date Time (m 3 0 /s) 16 8


m


3


H


w
O 07-07-93 1435 11,400 100 100


c


m 07-13-93 1030 9,290 100 100


a 07-30-93 1705 18,200 100 100


08-01-93 1445 19,900 100 100 

n

m 

m 

08-02-93 1330 28,700 100 100 ra 

w 08-04-93 1215 28,000 100 100 rA 

w 

v

'o. 

e 08-12-93 1930 24,000 100 100 

N 

L 

c 

m 

N 07-29-93 1030 25,400 100 100 Of 

3 

O 

c 

S 

N 

3 

a 

i 

A 

i

0

0

W 

Percentage of sample smaller than particle diameter 

4 2 

Missouri River at Hermann, Missouri 

99 94 

93 92 

97 94 

92 79 

Mississippi River at St. Louis, Missouri 

94 83 

97 87 

Mississippi River at Chester, Illinois 

93 85 

Mississippi River at Thebes, Illinois 

95 90 

1 0.5 0.25 0.125 0.062 

85 40 14 0 0 

86 38 12 0 0 

79 28 17 0 0 

59 35 13 0 0 

66 25 15 14 14 

68 15 1 0 0 

75 37 9 1 0 

80 54 22 8 6 
Einstein (Colby and Hembree, 1955), and Schoklitsch 

(Shulits, 1935). The values from these equations give 

a range of bedload transport estimates for the 1993 

flood. These three equations were selected on the basis 

of the onsite data required for computation, demonstrated use of the equations in a previous upper Mississippi River study (Jordan, 1965), grain size of material 

used to develop the equation, and the ability of the 

equation to estimate the bedload directly. 

SEDIMENT TRANSPORT DURING THE 

1993 FLOOD 

The Mississippi River at St. Louis was continuously above flood stage from June 26 through September 14. From the sediment data collected during the 

flood at the five stations listed in table 1, suspendedsediment loads have been computed and bedload estimated for the flood period. The St. Louis sediment station was selected to define the flood period because 

data also had been collected there during the 1951 and 

the 1973 floods. The suspended-sediment loads and 

particle-size data allow examination of the spatial and 

temporal variation of sediment sizes at the five sediment stations, comparison of the 1993 flood with other 

floods and the period of record, and investigation of 

the storage and flux of sediment in the lower Missouri 

and the central Mississippi Rivers. The cross-section 

and single vertical suspended-sediment concentration 

data allow examination of the temporal distribution of 

concentration in a flood of this magnitude and the nonhomogenous mixture of sediment downstream of the 

junction of two large rivers. 

Suspended-Sediment Concentrations and 

Loads and Bedload Estimates 

Hydrographs of water discharge and suspendedsediment concentrations of samples collected during 

the flood of 1993 at the Mississippi River at St. Louis, 

Chester, and Thebes are shown in figure 4. No hydrographs of suspended-sediment concentration are 

shown for the Mississippi River below Grafton and the 

Missouri River at Hermann because daily samples 

were not collected as was explained in the "Methods 

for Data Collection and Computation" section . The 

water-discharge hydrographs of the flood (fig . 4) indicate that the significant rise was in early to mid-July 

and that the discharge peaked on August 1 at St. Louis 

and August 7 at Chester and Thebes . At the sediment 

station at St. Louis, the suspended-sediment concentration first peaked on July 4, and water-discharge 

first peaked on July 11 . During the flood period, the 

suspended-sediment concentration peaked a second 

time within 1 day of the water-discharge peak on 

August 1 . Similar characteristics of peak sequences 

between water discharge and suspended-sediment 

concentration can be seen at Chester and Thebes. 

Suspended-sediment loads for the flood period 

were, in millions of metric tons, 7 at the Mississippi 

River below Grafton, 70 at the Missouri River at Her 

mann, 55 at the Mississippi River at St. Louis, 52 at 

the Mississippi River at Chester, and 51 at the Mississippi River at Thebes. The ranges in daily mean concentration and daily loads are listed in table 4. 

Bedload was computed for the range of water 

discharges at each station during the 1993 flood. Average curves drawn through values of computed bedload 

values and corresponding water discharge (fig . 5) were 

used to estimate the daily bedload on the basis of the 

daily mean water discharge. The estimated bedloads 

for the flood period as calculated by use of each equation are listed in table 4. The three equations provide 

estimates that generally are within 11 percent of each 

other at each sediment station except for those below 

Grafton and at St. Louis, where the differences are 87 

and 31 percent, respectively. The ranges of the measured variables used as input in the bedload equations 

are listed in table 5 . The estimated bedloads generally 

are less than 5 percent of the measured suspendedsediment load for all sediment stations except for the 

station below Grafton where the bedload estimate 

made by using the Modified Einstein equation was 18 

percent of the suspended-sediment load. 

Accuracy of Suspended-Sediment 

Concentrations and Loads 

The accuracy of suspended-sediment-concentration data is dependent on sampler error; measurement 

error, which includes spatial and temporal misrepre 

sentations of the mean suspended-sediment concentration, as well as onsite personnel error; and laboratory 

analysis error. On the basis of reports by the Federal 

Interagency Sedimentation Project (1952) and Beverage and Futrell (1986), the sampler error was estimated to be less than 15 percent for the onsite 

conditions (velocity, depth, bed roughness) during the 

1993 flood. By examining multivertical cross-section 

suspended-sediment data, measurement error was 

Sediment Transport During the 1993 Flood 1 1 
30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

Zz 30,000 0 

w 

co 

W 

a 

al 25,000 

W 

w 

U 

' 3 20,000


U


Z


ui 

C7 

Q 15,000 x

U

U 

D 

x 

w 

10,000 

I I , ,TI- .-r . . . -*-,-, - . , 1,600 

A MISSISSIPPI RIVER AT ST .LOUIS, MISSOURI / 

- Water discharge 

° Suspended-sediment concentration 

°

G 

G G ° IAL 

° G° Gp P°° G G 

° G 

June July August September 

1993 

B MISSISSIPPI RIVERAT CHESTER, ILLINOIS 

G 

- Water discharge 

0 

v 

June July August September 

1993 

1,400 

1,200 

1,000 

800 

600 

-m 400 

200 

0 

W 

J 

WW 

1,600 a 

1,400 2

J

J 

1,200 

z 

1,000 z

O 

H
Q
 800 Q


ZZW

U 600 Z

O 

U 

400 ZW 

200 w 

d 0 0 

Z

W 

7 to 1,600 

1,400 

1,200 

1,000 

800 

600 

400 

200 

0 

30,000 

- C MISSISSIPPIRIVER ATTHEBES, ILLINOIS 

- Water discharge 

25,000 ° Suspended-sediment concentration 

20,000 

�G 

15,000 QGG AL 

A AA A ° GAAG°A° Q 

° 

° AA°AdBAO®AAAAB°QAA°QQQGQ 

10,000 ,I, I I 

June July August September 

1993 

Figure 4. Water-discharge hydrographs and suspended-sediment-sample concentrations for the 

Mississippi River from June 26 through September 14, 1993. A, St . Louis, Missouri ; B, Chester, 

Illinois ; C, Thebes, Illinois . 

thought to be less than 10 percent. From qualityassurance data collected as part of a study by the 

Branch of Quality Assurance, USGS (L.J . Schroder, 

USGS, written commun., 1993), and from replicates 

analyzed separately by the National Research Program, USGS, Denver, Colorado, the suspendedsediment concentrations analyzed in the laboratory for 

this study had an average error of 8 percent. 

For daily record sediment stations, Colby (1956, 

p. 137) indicated the accuracy of sediment loads computed for a large river, such as the Mississippi, "in 

which flow is comparatively constant, sediments are 

1 2 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
-- --

Table 4. Suspended-sediment loads and estimated bedloads at sediment data-collection stations from June 26 through 

September 14, 1993 

[mg/L, milligrams per liter; t/d, metric tons per day ; t metric tons ; Min, minimum; Max, maximum; --, not determined] 

Range of daily Range of daily Bedload estimated using indicated 

mean mean load Suspended- equation

Station concentration (million t1d) sediment (million t)

(fig . 1) (mg/L) load 

Min Max Min Max 

(million t) Meyer-Peter Modified 

and Muller Einstein Schoklitsch 

Mississippi River below 

Grafton,111 . 0.02 0.27 7.0 0.45 1 .25 0.16 

Missouri River 

at Hermann, Mo. 

Mississippi River 

at St . Louis, Mo. 222 850 .28 

Mississippi River 

at Chester, 111 . 164 1,270 .28 

Mississippi River 

at Thebes,111 . 89 878 .14 

fine, and concentrations are high enough to sample 

accurately" to be about 10 percent . The annual suspended-sediment load for these stations generally has 

been thought to be within 10 percent of the true value 

on the basis of multiple computations of the same 

record by using variations in the suspended-sediment 

concentration hydrographs . These variations were 

70 .96 1 .00 .95 

1 .77 55 1 .82 2.25 1 .55 

1 .96 52 1 .56 1 .61 1 .47 

1 .35 51 2.50 2.32 2.60 

shifted within the estimated range of errors associated 

with suspended-sediment concentration . These errors 

are evident when the data are plotted as shown in 

figure 4. By interpolating the suspended-sedimentconcentration hydrographs through the middle of the 

"noise pattern" in these data, some of the error can be 

dampened out. 

Table 5. Minimum and maximum values of miscellaneous sediment, hydraulic, and slope data collected during multivertical 

sediment sampling and water-discharge measurements, June 26 through September 14, 1993 

[m3/s, cubic meters per second ; m/s, meters per second; m, meters ; mz, square meters ; m/km, meters per kilometer] 

Water-discharge measurements 

WaterStation Cross- surface Percent 

Water Mean Maximum Mean maximum section slope 

(m3/s) (m/s) (m/s) 

area (m/km) 

Mississippi River below Grafton, 11. 

Minimum . . . . . . . . . . . . . . . . . . . 79 8,670 1 .42 2.25 9.05 12 .8 6,080 0.035 

Maximum . . . . . . . . . . . . . . . . . . 99 16,200 1 .78 3.04 10.6 18 .6 9,130 .048 

Missouri River at Hermann, Mo. 

Minimum . . . . . . . . . . . . . . . . . . . 56.8 4,790 1 .34 2.17 6.73 11 .4 2,970 .148 

Maximum . . . . . . . . . . . . . . . . . . 83.2 21,200 2.40 3.43 10.8 15 .9 6,480 .172 

Mississippi River at St . Louis, Mo. 

(fig . 1) silt of stream stream depth depth samples discharge velocity velocity (m) (m) (m2) 

Minimum. . . . . . . . . . . . . . . . . . . 63 12,900 1 .62 2.21 12.9 17 .7 7,750 .072 

Maximum . . . . . . . . . . . . . . . . . . 85.9 29,200 2.54 4.14 16.99 26.8 12,100 .15 

Mississippi River at Chester, 111 . 

Minimum. . . . . . . . . . . . . . . . . . . 77 13,400 1 .49 2.32 9.81 19 .3 8,649 .109 

Maximum . . . . . . . . . . . . . . . . . . 85.2 26,800 2.26 4.27 17.9 27.4 13,400 .123 

Mississippi River at Thebes, 111 . 

Minimum. . . . . . . . . . . . . . . . . . . 

Maximum . . . . . . . . . . . . . . . . . . 

60.6 

85.6 

13,800 

27,600 

1 .66 

2.45 

2.65 

3.86 

10.6 

11 .3 

18 .0 

22.9 

8,110 

11,300 

.130 

.164 

Accuracy of Suspended-Sediment Concentrations and Loads 1 3 
Q

Y

Q

D 

¢

W 

a 

rn 

z

O

H

U 

F­ W 

z 

O

Q

O

J 

W 

m 

0 

w 

a 

to 

z

O 

O 

W 

Z 

O 

O 

0 

w 

m 

Q

0 

¢ 

w 

a 

Go

Z

O 

O 

H 

Z 

Q

O

J 

Ww 

m 

50,000 

- D Mississippi River at Chester, Illinois 

Hysteresis

20,000 loop curves 

10,000 

5,000 

3,000 

6,000 10,000 20,000 30,000 

WATER DISCHARGE, IN CUBIC METERS PER SECOND 

EXPLANATION 

Transport relation 

Hysteresis of Meyer - Peter and Muller 

Hysteresis of Einstein 

Hysteresis of Schoklitsch 

Meyer - Peter and Muller


Einstein


Schoklitsch


WATER DISCHARGE, IN CUBIC METERS PER SECOND 

Figure 5. Relation between water discharge and bedload by using the Meyer-Peter and Muller, the Modified Einstein, 

and the Schoklitsch bedload equations for selected data-collection stations . A, Mississippi River below Grafton, Illinois ; 

8, Missouri River at Hermann, Missouri; C, Mississippi River at St. Louis, Missouri ; D, Mississippi River at Chester, Illinois ; 

E, Mississippi River at Thebes, Illinois . 

For suspended-sediment loads estimated from 

transport relations, accuracy varies with the type of 

stream and density of data collection. In general, the 

accuracy of the estimate increases with a longer period 

of record estimated (for example, 3-month period load 

in comparison with a daily load) because "some of the 

inaccuracies in measured daily sediment loads will 

inevitably cancel each other when summed over long 

periods" (Walling, 1977, p. 531). Because the curves 

used in this report were developed by "visual fit" 

instead of by regression analysis, a statistical measure 

of error is unavailable . However, the probable accuracy of the load estimates for the flood period was 

determined by a curve that was developed for the 

Mississippi River at Thebes by using data from four 

multivertical cross sections and four of the samples 

collected by observers during the flood period. Because a daily record exists for this station, the 

suspended-sediment load estimated by the transport 

relation for the flood period was compared with the 

daily computed load for the flood period with the 

result that the daily record computed load had been 

overestimated by 14 percent . This error is a combination of all data collection and laboratory errors previously discussed plus any error inherent in the transport 

relation . 

1 4 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
---

----

w

100 

80 

Bed-material samples often were collected from a boat by 

using a US BM-54 sampler. 

Particle Size of Suspended-Sediment and BedMaterial Samples 

The mean suspended-sediment particle-size distributions for cross-section samples collected during the 

1993 flood are shown in figure 6. For these samples, the 

farther downstream, the coarser sediment particular constitute a larger percentage of the particle-size distribution. The contributions of all major tributaries in the 

upper Mississippi River system flowed past the sediment 

station at Thebes; suspended-sediment particle-size distributions at Thebes for multivertical samples collected 

before and during the 1993 flood period are shown in 

figure 7. No definite trend of coarsening or fining is 

noted as the water discharge changes. 

100 

80 

w 60 

F 

U

tt 40 a 

20 

. w \ Particle-size distribution \~., \\ 

and date of sample collection . 

Mississippi River at Grafton, Illinois, July 17, 1993 ."" 

Missouri River at Hermann, Missouri, July 30, 1993 -

Mississippi River at St. Louis, Missouri, July 7, 1993 

. . . . . . . Mississippi River at Chester, Illinois, July 21, 1993 

. . . . . . . . . . Mississippi River at Thebes, Illinois, July 21, 1993 

0.1 0 .01 0.001 

GRAIN SIZE, IN MILLIMETERS 

Figure 6. Mean particle-size distributions for multivertical 

suspended-sediment cross-section samples collected 

during the 1993 flood rise at the sediment data-collection 

stations . 

w 60 z 

w Particle-size distribution 

Q

a 40 March 14, 1990 

July 18, 1993 

20 July 21, 1993 

August 2, 1993 

and date of sample collection 

August 6, 1993 

0 

0 .001 

GRAIN SIZE, IN MILLIMETERS 

Figure 7. Mean particle-size distribution for multivertical 

suspended-sediment cross-section samples collected 

from the Mississippi River at Thebes, Illinois . 

The size distribution of bed material during the 

flood period is shown in figure 8. The bed material 

coarsened upstream. 

Sediment Loads 

Major floods occurred in the upper Mississippi 

River system in 1951 and 1973 . Suspended-sediment 

loads from these two floods were determined only for 

the Missouri River at Hermann and the Mississippi 

River at St. Louis (U.S. Army Corps of Engineers, 

1957 ; Chin and others, 1975). In 1951, the Mississippi 

100 

Particle-size distribution and 

the date of sample collection 

80 Missouri River at Hermann, -

Missouri, August 1, 1993 

Mississippi River at St. Louis,? 

Missouri, August 2, 1993 

w 60
 Z Mississippi River at Chester,


F Illinois, August 12, 1993


U Mississippi River at Thebes, 

40 Illinois, July 29, 1993 

a 

20 

0 

10 1 0 .1 0.01 

GRAIN SIZE, IN MILLIMETERS 

Figure 8. Bed-material particle-size distribution for selected 

sediment data-collection stations 

Sediment Loads 15 
River at St. Louis was above flood stage for 31 days 

from June 29 through July 29, whereas in 1973, the 

river was above flood stage from March 9 through May 

20 for a total of 73 days. The water-discharge volumes 

and suspended-sediment loads for all flood periods are 

listed in table 6. 

During the 1993 flood, less sediment was transported on a per-day basis than during the 1951 and the 

1973 floods . One explanation for this difference could 

be the effect of anthropogenic basin changes from 1951 

to 1993 . Since 1953, reservoirs upstream on the Missouri River have substantially decreased the sediment 

transported to the lower Missouri River (Meade and 

Parker, 1985). Holmes (1993) reported a significant 

downward trend in suspended-sediment concentration 

from 1948 through 1979 for the Mississippi River at St. 

Louis, whereas no trend was detected from 1980 

through 1991 . In addition, a large number of levee 

breaches occurred during the 1993 flood on the Missouri River. These breaches provided numerous potential sinks for sediment. 

For the Mississippi River sediment stations at St. 

Louis, Chester, and Thebes, the median daily suspendedsediment concentration and load for the 1993 flood and 

the period of record are listed in table 7. The median 

daily loads during the flood were more than five times 

the median load for the period of record, whereas the 

median concentrations for the 1993 flood period are 

extremely low and almost equal to the median concentration for the period of record. Furthermore, the suspendedsediment concentrations during the flood are low when 

compared with concentrations from previous rises in 

streamflow during the 1993 water year. The hydrographs 

of water discharges and suspended-sediment concentrations on the Mississippi River at Thebes for 

increases in discharge during November 1992 and during the 1993 flood are shown in figure 9. The peak 

suspended-sediment concentration for the first peak in 

the 1993 flood rise is about one-third of that for the 

November rise, whereas the peak water discharge for 

the 1993 flood is about twice that for the November 

1992 rise . The large differences in suspended-sediment 

concentrations possibly are caused by the seasonal differences of the two rises ; for example, late fall and midto late summer. However, the differences are more 

likely attributable to the depletion of the sediment supply and dilution of the sediment concentration that 

could be caused by any combination of the following: 

the unusually wet spring and early summer in 1993 

prevented many farmers from plowing and planting, 

which reduced the amount of fine sediment available 

to be transported to the rivers ; greater-than-normal 

flow for much of the spring and early summer on the 

Missouri and the Mississippi Rivers had already 

purged the system of much of the fine sediment available for resuspension ; extremely high-water discharges diluted the sediment concentration ; or the 

impact of raindrops, which detach sediment particles, 

was decreased on native soil by water in many fields. 

Between 21 and 29 percent of the 1993 annual 

suspended-sediment load was transported during the 

flood period at the sediment stations on the lower 

Missouri and the central Mississippi Rivers (table 8). 

These percentages of annual load transported are less 

than those transported by smaller rivers (Meade and 

others, 1990) where between 52 and 98 percent of the 

sediment load was transported in 10 percent of the 

Table 6. Suspended-sediment loads and volumes of water discharge for the 1951, 1973, and 1993 flood periods on the 

Missouri River at Hermann, Missouri, and the Mississippi River at St. Louis, Missouri 

[hm, hectare-meters ; t, metric tons] 

�1993 1951 flood period' 1973 flood period2 flood period3 

Station 

(fig . 1) Volume of water Suspended- Volume of Suspended- Volume of Suspended- water water 

(million hm) (million t) (million hm) (million t) (million hm) (million t) 

Missouri River at 3.5 4 57 5 .2 5 75 5.9 70 

Hermann, Mo. 

Mississippi River at 

St . Louis, Mo. 5 55 12 58 13.7 55 

discharge sediment load discharge sediment load discharge sediment load 

Flood period is defined as the 31-day period, June 29 through July 29, 1951 . 

'Flood period is defined as the 73-day period, March 9 through May 20, 1973 . 

3Flood period is defined as the 81-day period, June 26 through September 14, 1993 . 

413ata from U.S . Army Corps of Engineers (1957) . 

SData from Chin and others (1975) . 

1 6 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
W

--

Table 7. Median daily suspended-sediment concentrations and loads for the 1993 flood and the period of record at the daily 

sediment data-collection stations 

[mg/L, milligrams per liter ; t/d, metric tons per day ; --, no data] 

1993 flood Period of record 

Station Median daily Median Median daily Median daily (fig . 1) concentration daily load concentration load 

(mg/L) (t/d) 

Mississippi River below Grafton, Ill. . . . . . . . . . . . . . . . . . . . . . 

Mississippi River at St. Louis, Mo . . . . . . . . . . . . . . . . . . . . . . . 

Mississippi River at Chester, Ill . . . . . . . . . . . . . . . . . . . . . . . . . . 

Mississippi River at Thebes, Ill . . . . . . . . . . . . . . . . . . . . . . . . . . 

time. The larger the river system, the less effect 

suspended-sediment load transported during lower 

frequency floods have on the annual sediment 

delivery. However, regardless of the size of a river 

system, major channel and bed changes are the 

result of the dynamics of sediment transport during 

these low-frequency floods . 

The mean annual suspended-sediment loads 

also are listed in table 8 . The 1993 water year annual 

load exceeded the mean annual load by 52 to 75 per 

cent for all stations except the Missouri River at Hermann where the 1993 load exceeded the mean annual 

load by 128 percent . 

Mixing of Sediment From the Missouri and the 

Mississippi Rivers 

The Missouri River flows into the Mississippi 

River 24 km upstream from the sediment station at 

St. Louis (fig . 1). At St. Louis, the water from the 

30,000 

a

z 25,000
 O
U


(7 U 

CC W 20,000 = EL U cn NQ


aF
 uJ W 15,000
 ~H¢U 

fO 

U 10,000 z 

5,000 

20 21 22 23 24 25 26 27 28 29 30 1 2 

November December 

1992 

(mg/L) (t/d) 

62,700 125 41,300 

340 694,000 326 128,000 

326 682,000 304 127,000 

317 717,000 302 139,000 

Missouri River, which routinely carries a larger sediment concentration, is not completely mixed with the 

water from the central Mississippi River. The sediment contributions for each river are evident in figure 

10. The more sediment-laden Missouri River water 

flows along the Missouri shoreline (in the background) and the clearer Mississippi River water flows 

along the Illinois shoreline . The lateral distribution 

of suspended-sediment concentrations determined 

from cross-section samples collected during the flood 

period is shown in figure 11 . The concentration of 

suspended sediment near the Missouri shoreline was 

about five times greater than that near the Illinois 

shoreline. 

Waters from two major rivers sometimes can 

flow for tens of kilometers before they become visually mixed. The mixing distance depends on the river 

conditions, such as water discharge, season, temperature, and relative water discharge and sediment inputs 

from the two rivers. Aerial photographs taken on July 

3,000 

z 

O 

2,500 ¢ 

w~ 

2,000 z 

Oa


~- m
 1,500 m
 w 

DU
 W J
 1,000 rn J


62


0 Z


500 w

a

O 

U 0 

June July August 

1993 

Figure 9. Water-discharge and suspended-sediment-concentration hydrographs for two floods on the Mississippi River 

at Thebes, Illinois . 

Mixing of Sediment From the Missouri and the Mississippi Rivers 17 

111 
Table 8. 1993 flood and annual suspended-sediment loads at the sediment data-collection stations 

[t, metric tons] 

1993 

Station 1993 

(fig . 1) sediment 

load 

(million t) 

annual 

sediment 

load' 

(million t) 

annual load 

transported 

during 

1993 flood 

load for 

period of 

record 

(million t) 

Mississippi River below Grafton, Ill' . . . . . . . . . . . . . . . . . . . . . 27 33 21 321 .3 

Missouri River at Hermann, Mo . . . . . . . . . . . . . . . . . . . . . . . . . 270 2265 26 4 116 

Mississippi River at St . Louis, Mo . . . . . . . . . . . . . . . . . . . . . . . 55 187 29 5119 

Mississippi River at Chester, Ill . . . . . . . . . . . . . . . . . . . . . . . . . 52 192 27 6126 

Mississippi River at Thebes, Ill . . . . . . . . . . . . . . . . . . . . . . . . . . 51 203 25 7116 

'1993 water year is from October l, 1992, through September 30, 1993 . 

Load computed by using transport relations. 

Flood of water year Percentage of Mean annual 

RRecord used to compute mean annual load-1987 to 1993, includes data collected from 1987 to 1989 at Alton, Illinois, 25 miles 

downstream . 

`Record used to compute mean annual load-1949 to 1981, annual load estimates provided by U.S . Army Corps of Engineers, Kansas 

City District . 

5Record used to compute mean annual load-1980 to 1993 ; does not include record from 1949 to 1979 because of anthropogenic

changes documented in Holmes (1993) . 

6Record used to compute mean annual load-1983, 1988 to 1993 ; does not include record from 1980 to 1982 and from 1984 to 1987 

because of missing records during those years. 

Record used to compute mean annual load-1983, 1985, 1987, 1989 to 1993 ; does not include record from 1980 to 1982, 1984, and 

1986 to 1988 because of missing records during those years 

25, 1993, show that the Mississippi River became well 

mixed 88 km downstream from its normal junction 

with the Missouri River. In addition, for a large part of 

the 1993 flood period, the two rivers began flowing 

together 32 km upstream from where they normally 

meet. Inspection of aerial photography taken on 

August 3, 1993, after major levees failed downstream 

from St. Louis on August 1 and 3 indicates that the 

rivers became mixed 43 km downstream from the normal junction of the two rivers . Aerial photographs 

taken on June 22, 1988, during a major drought shows 

that the rivers were mixed within 8 km of their junction. Knowledge of how this mixing takes place is 

important for the management of water-treatment 

plants that are supplied by the Mississippi River. 

Storage and Flux of Sediment in the Lower 

Missouri and the Central Mississippi River 

Basins 

Large quantities of sediment were transported 

past the five sediment stations on the lower Missouri 

and the central Mississippi Rivers during the 1993 

flood (table 8) . The suspended-sediment load of the 

Missouri River at Hermann was 10 times greater than 

that of the Mississippi River below Grafton. The 

suspended-sediment load transported by the 

Mississippi River past St. Louis was 22 million 

metric tons less than the sum of the 77 million metric 

tons of suspended-sediment load transported past the 

two upstream sediment stations below Grafton and at 

Hermann during the flood period. The smaller load at 

St. Louis implies that sediment went into storage 

between the upstream stations and St. Louis. This 

implication is partly verified by the presence of 

massive quantities of newly deposited sand on riverbend flood plains (fig . 12) . Most of the sand seems to 

be associated with major levee breaks where high 

hydraulic heads built up before the levee broke. 

These high hydraulic heads in conjunction with the 

levee break resulted in high-energy flows that 

transported tremendous quantities of sand onto the 

flood plains . Recent surveys (G.K. Schalk, USGS, 

written commun., 1994) from selected Missouri 

River bend flood plains indicate more material was 

deposited on the flood plain than was scoured from 

the levees and flood plains, which indicates that 

much of the sand came from the river. Deposition of 

as much as 0.14 m of silt and clay and 4 m of sand 

18 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 1 4, 1993 
Fmk 

Figure 10. The Mississippi River at St . Louis, Missouri, July 30, 1993, looking west, showing the lateral variability in 

sediment concentration. Lighter areas are higher in suspended sediment, (Photograph from Srenco Photography, St. Louis, 

Missouri, 1993, and published with permission .) 

over more than 20,000 hectare has been observed on 

the river-bend flood plains downstream from 

Hermann. Preliminary estimates from the surveys 

indicate that more than 35 million metric tons of 

sediment were deposited on the flood plain between 

Hermann and the mouth of the Missouri River. 

More sediment was transported by the Missouri 

River at Hermann than by the Mississippi River at St. 

Louis because the water-surface slope of the Missouri 

River at Hermann was about 30 percent greater than 

that of the Mississippi River at St. Louis (table 5). This 

smaller slope decreases the transport power of the 

river and, in turn, decreases the ability of the river to 

suspend and transport sediment. 

The total sediment loads at the Mississippi River 

sediment stations at St. Louis, Chester, and Thebes for 

the flood period were within 7 percent of each other 

[within the accuracy of suspended-sediment-data collection (Meade and others, 1990)]. Therefore, on a 

macroscale, sediment was neither being stored nor 

added to the system between St. Louis and Thebes, 

which implies that the system as a whole was in equilibrium because the load at St. Louis virtually equalled 

that at Chester and Thebes. Potential major sinks for 

sediment were created by levee breaks on the Mississippi River below St. Louis ; however, aerial and ground 

reconnaissance revealed noticeably less associated sand 

deposition than was evident at the Missouri River levee 

breaks. The smaller sand deposits on the Mississippi 

River could be related to stream pattern differences 

(abundant, wooded midchannel islands on the Mississippi River compared with much fewer midchannel 

islands in the Missouri River), differences in width of 

riparian zones, timing of major levee breaks, and differences in energy slope. 

On a microscale, there were dynamic changes in 

the reach from St. Louis to Thebes. Channel-bed 

changes for the Mississippi River at Chester are shown 

Storage and Flux of Sediment in the Lower Missouri and the Central Mississippi River Basins 19 
w 1,400 

Ww0-

1,200 

C7 

J 1,000 

z 

Z .c O 800 y

L

0 F 

N 

Z 7 

U 600 IN z 

O 

U 

i-Z

W 400 

W

U 200 W 

O

Z

W 

0 

I ' ' ' I I , 

0 ..- . " Suspended-sediment concentration, 

July 7,1993 

", Suspended-sediment concentration, 

1,010 September 2, 1993 

300 400 500 600 700 

BRIDGE STATION, IN METERS 

Figure 11 . Lateral distribution of suspended-sediment concentrations for the Mississippi River at 

St . Louis, Missouri . 

in figure 13 . Scour in the channel bed was as great as 4 

mfrom July 12 through July 20, 1993 (fig . 13A). Such 

scouring adds to the sediment in transport. A general 

pattern of scour during the flood rise was followed by 

aggradation during the recession (fig. 13B). However, 

as of February 3, 1994, the channel bed still had not 

aggraded to the previous bed level of November 17, 

1992 (fig . 13C). 

SUMMARY 

Sediment data were collected at five sediment 

stations on the lower Missouri and the central Mississippi Rivers during the 1993 flood. The suspended 

sediment loads transported past these sites for the 81-

day flood period from June 26 through September 14, 

1993, were, in millions of metric tons, 7 at the Mississippi River below Grafton, 70 at the Missouri River at 

Hermann, 55 at the Mississippi River at St. Louis, 52 

at the Mississippi River at Chester, and 51 at the 

Mississippi River at Thebes . By using the Meyer-Peter 

and Muller, the Modified Einstein, and the Schoklitsch 

equations, bedload was estimated for these sites to be 

generally less than 5 percent of the suspendedsediment load, except for the station below Grafton. 

The 1993 flood generally transported less sediment per volume of water discharge than did other 

floods on the Mississippi River. This decrease in transported sediment probably is attributable to the construction and operation of reservoirs in the upper 

Missouri River since 1953 that greatly decreased the 

supply of sediment, as well as the depletion and dilution of sediment that was evident during the 1993 

flood. Possible causes of these phenomena are the 

unusually wet spring and early summer that prevented 

many farmers from plowing and planting, which made 

less fine sediment available to be transported to the 

rivers ; greater-than-normal flow for much of the 

spring and early summer, so that the Missouri and the 

Mississippi Rivers had already purged the system of 

much of the fine sediment available for resuspension ; 

extremely high water discharges diluted the sediment 

concentration ; and the decrease in raindrop impact on 

native soil because of the water in many fields . 

The suspended-sediment load transported by the 

Mississippi River past St. Louis was 22 million t less 

than the total of the suspended-sediment loads trans 

ported past the two upstream sediment stations below 

Grafton and at Hermann (77 million t) . This loss of 

sediment implies that sediment was being stored 

between the upstream stations and St. Louis and is 

partly verified by the massive amount of newly deposited sediments on more than 20,000 ha of the flood 

plain downstream from Hermann. New sediment 

deposits as thick as 4 m were observed. The ability of 

the Mississippi River near St. Louis to transport sediment generally was less than the Missouri River at 

Hermann because the water-surface slopes at St. Louis 

were about 30 percent less than those at Hermann. 

The Missouri River at Hermann contributed 10 

times as much sediment as the Mississippi River contributed below Grafton, which is upstream from the 

20 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
Figure 12. View of the sand deposited on the Missouri 

River flood plain near the junction of the Missouri and the 

Mississippi Rivers, November 8, 1993. (Photograph from 

U.S . Army Corps of Engineers, 1993, and published with 

permission .) 

junction of the two rivers . The inflow of the Missouri 

River causes a nonhomogenous mixture of water in 

the Mississippi River past St. Louis 24 km downstream from the inflow. The suspended-sediment concentration near the Missouri shoreline is almost five 

times that near the Illinois shoreline . Aerial photographs taken on July 25, 1993, show that the Mississippi River became well mixed 88 km downstream 

from its normal junction with the Missouri River. 

In the Mississippi River reach between St. Louis 

and Thebes, the suspended-sediment loads are fairly 

constant, which implies equilibrium ; however, many 

dynamic changes occurred within this reach. For 

example, at Chester, as much as 4 m of scour was 

measured between July 12 and July 20, 1993. The 

channel-bed changes generally followed a pattern of 

Collection of data on large rivers, such as the Missouri and 

the Mississippi, often requires specialized equipment, such 

as this monorail system built underneath the Thebes, Illinois, 

railroad bridge. 

scouring during the flood rise followed by aggradation 

during the recession. 

The particles of the suspended sediment transported in the Mississippi River between Grafton,111. 

and Thebes, Ill . are larger in size in the downstream 

direction, whereas no change in particle size is seen 

with variation of discharge. Bed material coarsens in 

the upstream direction . 

Summary 21 
----

105 

100 

95 

90 

115 

J 

W 

W 

J 

W 

W 

O 105 

m


w


w 100


z


z


O


H 95


w


J 

W 

90 

115 

105 

100 

95 

90 

Streambed cross section 

July 12, 1993 

July 20, 1993 

0 100 200 300 400 

0 100 200 300 400 500 600 700 800 900 

0 100 200 300 400 500 600 700 800 900 

BRIDGE STATION, IN METERS 

Figure 13. Streambed cross sections for the Mississippi River at Chester, Illinois . A, Streambed

scouring prior to flood peak; B, Streambed aggradation following the flood peak; C, Streambed 

levels 6 months after flood peak. 

REFERENCES CITED 

Beverage, J.D., and Futrell, II, J.C., 1986, Comparison of 

flume and towing methods for verifying the calibration of a suspended-sediment samples : U.S . Geologi 

cal Survey Water-Resources Investigations Report

86-4193, 12 p. 

Chin, E.H., Skelton, John, and Guy, H.P ., 1975, The 1973 

Mississippi River Basin flood-Compilation and 

analysis of meteorologic, streamflow, and sediment 

data: U.S . Geological Survey Professional Paper 

937, 137 p. 

Colby, B .R., 1956, Relationship of sediment discharge to 

streamflow: U.S . Geological Survey open-file report, 

170 P. 

Colby, B.R., and Hembree, C.H., 1955, Computations of 

total sediment discharge, Niobrara River near Cody, 

Nebraska : U.S. Geological Survey Water-Supply 

Paper 1357, 187 p. 

22 Sediment Transport in the Lower Missouri and the Central Mississippi Rivers, June 26 through September 14, 1993 
Edwards, T.K., and Glysson, G.D., 1988, Field methods 

for measurement of fluvial sediment: U.S . Geological Survey Open-File Report 86-531, 118 p. 

Federal Interagency Sedimentation Project, 1952, The 

design of improved types of suspended sediment 

samples : Federal Interagency River Basin Committee, Subcommittee on Sedimentation Report 6, 103 p. 

Glysson, G.D., 1987, Sediment-transport curves : U.S . Geological Survey Open-File Report 87-218, 47 p. 

Holmes, Jr ., R.R ., 1993, Suspended-sediment concentration trends on the Mississippi River between St. 

Louis, Missouri, and Cairo, Illinois [abs .] : Mississippi River Research Consortium, 25th annual meeting, Lacrosse, Wisconsin, April 22-23, 1993, 

Programs with Abstracts, 1 p. 

Jordan, P.R ., 1965, Fluvial sediment of the Mississippi 

River at St. Louis, Missouri: U.S . Geological Survey 

Water-Supply Paper 1802, 89 p. 

Meade, R.H ., and Parker, R.S ., 1985, Sediment in rivers of 

the United States, in National Water Summary 

1984-Hydrologic events, selected water-quality 

trends, and ground-water resources: U.S . Geological 

Survey Water-Supply Paper 2275, 467 p. 

Meade, R.H., Yuzyk, T.R ., and Day, T.J ., 1990, Movement 

and storage of sediment in rivers of the United States 

and Canada, in Wolman, M.G., and Riggs, H.C ., 

eds., Surface water hydrology: Geological Society of 

America, The Geology of North America, v. O-1, 

p. 255-280. 

Meyer-Peter, E., and Muller, R., 1948, Formulas for bedload transport: International Association of Hydraulic Structures Research, 2d, Stockholm, Sweden, 

p. 39-64. 

Parrett, C., Melcher, N.B ., and James, Jr ., R.W., 1993, 

Flood discharges in the upper Mississippi River 

Basin, 1993: U.S . Geological Survey Circular 

1120-A, 14 p . 

Porterfield, George, 1972, Computation of fluvial-sediment 

discharge: U.S . Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. C3, 

66 P. 

Shulits, Samuel, 1935, The Schoklitsch bed-load formula: 

Engineering, v. 139, p. 644, 687. 

U.S . Army Corps of Engineers, 1957, Suspended-sediment 

in the Missouri River, daily record for water years 

1949-1954: Omaha, Nebraska, U.S . Army Corps of 

Engineers, 210 p. 

Walling, D.E ., 1977, Assessing the accuracy of suspendedsediment rating curves for a small basin: Water 

Resources Research, v. 13, no. 3, p. 531-538. 

References Cited 23