P R O P A G A T I O N 

A N D 

C O M P O S I T I O N 

O F T H E 

FLOOD WAVE 

ON THE UPPER 

MISSISSIPPI RIVER 

9 9 3 

U.S . GEOLOGICAL SURVEY CIRCULAR 1120-F 

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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) 
PROPAGATION AND COMPOSITION OF THE FLOOD 

WAVE ON THE UPPER MISSISSIPPI RIVER, 1993 

By John A. Moody 

Floods in the Upper Mississippi River Basin, 1993 

U.S. GEOLOGICAL SURVEY CIRCULAR 1120-F 
U.S . DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S . GEOLOGICAL SURVEY 

GORDON P EATON, Director 

For sale by U.S . Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225 

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. 

Published in the Eastern Region, Reston, Va . 

Manuscript approved for publication February 14, 1995 

Library of Congress Cataloging in Publication Data 

Moody, John A . (John Alexander), 1944-

Propagation and composition of the flood wave on the upper Mississippi River, 1993 / by 

John A . Moody. 

p . cm. -(Floods in the upper Mississippi River basin, 1993) 

(U .S . Geological Survey circular ; 1120-F) 

Includes bibliographical references (p. - ) . 

Supt. of Docs. no. : I 19 .4/2: 

1 . Floods-Mississippi River Valley. 2 . Flood routing-Mississippi River Valley . 

I . Title . II . Series . III . Series: U.S . Geological Survey circular ; 1120-F. 

GB 1217158 1993 ch . F 

[GB 1399A .M71 

551 .48'9'0977 s-dc20 

[551 .48'9'09771 95-38379 

CIP 
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. 

Director 

Foreword III 
Contents 

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

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

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

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Flood wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Flood-wave routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

Flood-wave propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Tributary inflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Flood-plain storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 

Levee breaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 

Levee seepage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Flood-wave composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 

Mississippi River at Prescott, Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 

Mississippi River at Winona, Minnesota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 

Mississippi River at Clinton, Iowa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 

Mississippi River at Keokuk, Iowa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 

Mississippi River at St . Louis, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 

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

Selected References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 

FIGURES 

1 . Map showing the upper Mississippi River and some of its tributaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

2. Graph showing the mean discharge of the upper Mississippi River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

3-4. Graphs showing: 

3. Composite flood wave on the upper Mississippi River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

4. Periods of open channel for the upper Mississippi River, 1992 and 1993. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 

5 .- 8. Graph showing: 

5. Daily mean water discharge at seven stream-gaging sites on the upper Mississippi River from April 

through August 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

6. Times and locations of maximum stages and discharges during the 1993 flood on the upper 

Mississippi River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

7. Daily mean discharge of the upper Mississippi River at St. Louis, Missouri, and at Thebes, 

Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 

8. Water levels for the Mississippi River near Thebes, Illinois, and for the adjacent East Cape 

Girardeau and Clear Creek Levee Districts, July through October 1993. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 

9.-13 . Graph showing flood-wave composition of the Mississippi River at : 

9. Prescott, Wisconsin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 

10 . Winona, Minnesota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 

11 . Clinton, Iowa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 

12 . Keokuk, Iowa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 

13 . St . Louis, Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 

TABLES 

1 . Drainage areas, mean discharges, and 1993 flood discharges for the upper Mississippi River and some 

of its tributaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

2. Flood-wave propagation speeds on the upper Mississippi River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 

3. Some levee breaks on the upper Mississippi River, July and August 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 

4. Daily mean discharges for the upper Mississippi River and some of its tributaries, June through 

August 1993 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 

Contents V 
CONVERSION FACTORS AND VERTICAL DATUM 

Multiply 

meter (m) 

kilometer (km) 

square kilometer (km-) 

cubic meter (m3) 

meter per second (m/s) 

cubic meter per second (m3 /s) 

kilometer per day (km/d) 

By 

Length 

3 .281 

0.6214 

Area 

0.3861 

Volume 

35 .31 

Velocity 

3 .281 

35 .31 

0 .6214 

To obtain 

foot 

mile 

square mile 

cubic foot 

foot per second 

cubic foot per second 

mile per day 

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.


Meandischarge : In this report, "mean discharge" is the arithmetic mean of individual daily mean discharges during a period, usually the period of


record of the stream-gaging station .


Contents VI 
Propagation and Composition of the Flood Wave on the


Upper Mississippi River, 1993 

ByJohn A. Moody 

Abstract 

The historic flood of 1993 affected the 

entire 1,358-kilometer reach of the upper Mississippi River from Minneapolis, Minnesota, to 

Cairo, Illinois, but had no unusual effect on the 

lower Mississippi River from Cairo to the Gulf of 

Mexico. The flood was preceded by heavy (200 

percent of normal) spring rains that saturated the 

ground in much of Minnesota, Iowa, Illinois, and 

Wisconsin. The flooding began in June along the 

upper 200 kilometers of the river. Intense rains 

that continued into summer caused the Minnesota 

River in Minnesota and the Chippewa and the 

Black Rivers in Wisconsin to contribute simultaneously near-record discharges to the upper Mississippi River from June 22 to 25. The maximum 

discharge in the flood wave, which propagated 

downstream at about 0.58 meter per second, was 

five to seven times the daily mean discharge at 

stream-gaging stations on the upper Mississippi 

River. As the flood wave propagated southward, 

the rains shifted southward in concert. The phase 

or propagation speed of the flood wave was influenced largely by hydrologic factors, such as tributary inflow and flood-plain storage, rather than 

by hydraulic factors, such as water depth, channel width, and channel roughness. The Iowa and 

the Des Moines Rivers contributed near-record 

discharges to the Mississippi in early July. A 

record (greater than 100-year recurrence interval) 

discharge of 12,300 cubic meters per second 

occurred on the Mississippi River at Keokuk, 

Iowa, on July 10. This part of the flood wave 

probably passed St. Louis, Missouri, on July 20, 

but was not the major flood peak there; by late 

July, the rains had shifted further southward into 

Missouri and central Illinois, which caused the 

Missouri and the Illinois Rivers to contribute 

about 20,900 and 2,220 cubic meters per second, 

respectively, to the upper Mississippi River at St. 

Louis from July 29 to July 31. Not all of this 

water passed Thebes, Illinois (about 70 kilometers upstream from Cairo, where the last downstream-gaging and sampling station on the upper 

Mississippi River is located), because water left 

the channel of the upper Mississippi River 

upstream from Thebes through failed levees and 

by seepage through and under the levees that did 

not fail and was stored temporarily on the flood 

plain. The maximum discharge at St. Louis 

(29,700 cubic meters per second) occurred on 

August 1 ; however, the maximum discharge at 

Thebes (27,700 cubic meters per second) did not 

occur until August 7, which was about 4 days 

later than the normal travel time of 2 days. 

INTRODUCTION 

Flood waves that move down the upper Mississippi River, which ends at the confluence with the 

Ohio River at Cairo, Illinois, are confined and altered 

by human and natural processes. Starting in Minneapolis, Minnesota, a moderate flood cannot propagate 

as a free wave under normal conditions because the 

free surface of the river is controlled by a drop of 96 

meters (m) through a series of stairstep pools created 

by backwater from 29 navigation dams that regulate 

the 1,050-kilometer (km) reach of the river to its confluence with the Missouri River near St. Louis, Missouri (fig . 1) . Between Minneapolis and Clinton, 

Iowa (532 km), the flood plain is narrow and confined by high bluffs on either side ; the average depth 

of the river is 2 m. Downstream from Clinton to St . 

Introduction 1 
95 . 

ao St-Croix Fallen 

rndcdam 1 ank C 

thony Falls upper

46°i ewer lock and dam 

Preseott r'P` I 

,t3 &Durand 

pDodge 

Winoir~t_ A &Galesville 

EXPLANATION 

-"" -Boundary of upper and lower 

Mississippi River 110 Navigation lock and dam and 

number ,Joslin Stream-gaging station and 

Chester name shown on tributaries 5 ~~SS~ o Stream-gaging station and `o~Ea name shown on the 

1 Sny Levee 1fllssissippi River 

Levee Base map from U.S . Geological Survey National Atlas, 1970 

100 200 MILES 

100 200 KILOMETERS 

Figure 1 . Upper Mississippi River and some of its tributaries. 

2 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
Louis (518 km), the flood plain widens, and a series 

of levees of different heights has been built by Federal, State, and local agencies . The levees normally 

confine a moderate flood wave to a narrow channel 

within the wider flood plain; the average depth of the 

river is 3 m. From St. Louis to Cairo (315 km), where 

the Ohio River joins the upper Mississippi River, the 

Mississippi is channelized by using lateral dikes and 

revetments to maintain an average depth of 7 m. 

Because there are no navigation dams on this reach of 

the river, flood waves can propagate freely . 

The flood of June through August 1993, however, was not a moderate flood. For floods this large, 

the gates in the navigation dams are raised out of the 

water, which prevents damage to structures and 

machinery at the dam, and the river surface more 

closely resembles a natural, smoothly changing surface than a series of stairsteps. 

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Flows from tributaries also affect the timing 

anc: shape of a flood wave, depending upon the proportion of the tributary's discharge to the discharge of the 

main river. The mean discharge of the upper Mississippi River, which receives a large percentage of its 

water from its many tributaries (fig . 2; table 1), 

increases from 225 cubic meters per second (m3/s) 

near Anoka, Minnesota, at an average rate of 4.2 m3 /s 

per river kilometer. In contrast, the mean discharge of 

the lower Mississippi River (downstream from the confluence with the Ohio River), which has fewer significant tributaries, increased from 13,500 m3 /s near Cairo 

at an average rate of only 1 .6 m3/s per river kilometer. 

Purpose and Scope 

This report describes the propagation of the 

flood wave of 1993 through the engineered channel of 

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DISTANCE UPSTREAM FROM THE OHIO RIVER, IN RIVER KILOMETERS 

Figure 2. Mean discharge of the upper Mississippi River in relation to distance upstream from the confluence of the 

upper Mississippi River with the Ohio River. See footnote in table 1 for references that give the period of record for 

the mean discharges shown here . 

Introduction 
Table 1 . Drainage areas, mean discharges, and 1993 flood discharges for the upper Mississippi River and some of its 

tributaries 

[km, kilometer ; km2, square kilometer ; m3 /s, cubic meter per second; na, does not apply. Mean discharge is given for the stream-gaging station closest to the 

mouth of the tributary ; distances upriver from the Mississippi-Ohio River confluence are measured to the mouth of the tributary. See Parrett and others 

(1993) for other flood discharges] 

Percentage Estimated Distance of mean 

upriver from discharge of Maximum daily travel time 

mean to next 

Stream-gaging Mississippi Drainage Period of Mississippi Mean discharge for downstream 

stations and Ohio area River 

River (km2) record downstream 

discharge June through Mississippi 

confluence from mouth of 

(m3/s) August River stream­

(km) tributary (m3/s) gaging stations 

(percent) (days) 

Mississippi River near 1,391 49,500 1931-88 na 225 974 2 

Anoka, Minn. 

Minnesota River near 1,358 42,000 1934-88 34 107 2,570 2 

Jordan, Minn. 

St . Croix River at 1,307 17,700 1902-89 25 122 558 2 

St . Croix Falls, Wis. 

Mississippi River at 1,306 116,000 1928-89 na 486 3,680 3 

Prescott, Wis. 

Chippewa River at 1,228 23,300 1928-89 28 216 2,400 1 

Durand, Wis. 

Mississippi River at 1,168 153,300 1928-88 na 788 4,810 6 

Winona, Minn. 

Trempealeau River at 1,154 1,670 1913-19 1 .5 12.2 145 6 

Dodge, Wis. 1934-89 

Black River near 1,141 5,400 1931-89 5.8 49.3 1,540 6 

Galesville, Wis. 

Root River near 1,116 3,290 1912-88 1 .2 10.1 214 5 

Lanesboro, Minn. 2 

Upper Iowa River near 1,080 1,990 1936-89 1 .8 15 .6 231 4 

Dorchester, Iowa. 

Wisconsin River at 1,015 26,900 1902-03 22 246 1,670 3 

Muscoda, Wis. 1913-89 

Turkey River at 978 4,000 1913-89 2.3 26.7 456 3 

Garber, Iowa. 3 

Grant River at 954 700 1934-89 0.4 4.7 111 2 

Burton, Wis. 

Platte River near 947 370 1934-89 0.2 2.8 73.9 2 

Rockville, Wis. 

Maquoketa River near 883 4,020 1913-89 2.4 29.0 827 1 

Maquoketa, Iowa. 

Mississippi River at 823 221,700 1873-1989 na 1,350 6,230 4 

Clinton, Iowa. 

Wapsipinicon River 815 6,030 1934-89 3 .1 43.2 609 4 

near DeWitt, Iowa. 

Rock River near 771 24,700 1939-88 11 176 986 4 

Joslin, Ill . 

Iowa River at 698 32,400 1914-89 11 197 3,000 2 

Wapello, Iowa. 

4 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
Table 1 . Drainage areas, mean discharges, and 1993 flood discharges for the upper Mississippi River and some of its 

tributaries-Continued 

Percentage Estimated Distance of mean Maximum travel time upriver from discharge of dailmean tt 

Stream-gaging Mississippi Drainage Period of Mississippi Mean y o ne 

stations and Ohio area River discharge discharge for downstream 

River (km21 record downstream (m3/s) June through Mississippi 

confluence from mouth of August River stream­

(km) tributary (m3/s) gaging stations 

(percent) (days) 

Skunk River at 637 11,100 1914-89 4.2 68.8 1,300 1 

Augusta, Iowa. 

Mississippi River at 586 308,200 1878-1989 na 1,810 12,100 4 

Keokuk, Iowa. 

Des Moines River at 582 36,400 1904-05 8 165 3,060 4 

Keosauqua, Iowa. 1912-89 

Illinois River at 351 69,700 1938-88 24 620 2,220 2 

Meredosia, 111 . 

Salt River near 457 6,400 1922-89 1 .8 48.2 317 1 

New London, Mo. 

Missouri River at 314 1,358,000 1897-1989 46 2,290 20,900 1 

Hermann, Mo. 

Mississippi River at 289 1,805,000 1861-1989 na 5,140 29,700 2 

St . Louis, Mo. 

Meramec River near 259 9,810 1903-06 1 .8 89.0 918 1 

Eureka, Mo. 1921-89 

Kaskaskia River near 189 11,400 1969-88 2 107 252 1 

Venedy Station, 111. 

Mississippi River at 70 1,847,000 1932-89 na 5,600 27,700 0 

Thebes,111 . 

'Institute of River Studies, 1983 . Travel times from river kilometers 289 to 938 averaged about 0.7 m/s; this speed was extrapolated and used from river 

kilometers 938 to 1,228 . Travel times between river kilometers 1,306 and 1,391 were based on information furnished by Joseph Hess, U.S . Geological Survey, Minnesota District. The extrapolation of travel times was supported by the conservation of mass calculations (with errors of about 10 percent) for Mississippi River stream-gaging sites . 

`1912-14, 1916-17, 1941-85, and 1987-88 . 31913-16, 1919-27, 1929-30, and 1932-89. 

the upper Mississippi River from Minneapolis to 

Thebes, Illinois, and the effects of tributary inflow and 

flood-plain storage on this flood wave. The composition of this flood wave, in terms of contributions from 

tributaries, is described for five U.S . Geological Survey stream-gaging stations between Minneapolis and 

Thebes-Prescott, Wisconsin, Winona, Minnesota, 

Clinton and Keokuk, Iowa, and St. Louis. 

Flood Wave 

The shape of the upper Mississippi River flood 

wave of 1993 was not the simple, solitary flood wave 

commonly depicted in textbooks, but was a composite 

shape that resulted from the summation of many 

separate tributary flood waves. The length of the 

composite flood wave was essentially the length of the 

upper Mississippi River, or 1,358 km (fig . 3A). The 

water surface of the composite flood wave for June 25 

dropped sharply (600 km upstream from the Ohio 

River; fig . 3A); this was caused by the hydroelectric 

power dam at Keokuk, which always controls the flow 

of the river (fig . 4). This composite flood wave 

comprised three secondary peaks that can be seen when 

the average river slope of 91 x 10-6 is removed (fig . 

3B). The daily mean discharge of some tributaries was 

routed into and down the upper Mississippi River at an 

assumed average water speed of about 0.7 meter per 

second (m/s) (Institute of River Studies, 1983). The 

shapes ofthe tributary discharge flood waves for June 

25 had abrupt increases at the mouth ofthe tributary 

Introduction 5 
---

--------

(fig . 3C). The summation of the tributary discharges in 

the upper Mississippi River upstream from Keokuk had 

a shape similar to the composite flood wave (fig . 3B) . 

The composite flood wave for August 1 (date of peak 

discharge at St. Louis at river kilometer 289) distinctly 

showed the inflow of the floodwaters from the Missouri 

River (fig . 3B). On August 1, numerous drops in the 

J

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4,000 w Wisconsin River Summationof five tributary 

0) flood wavesfor June 25,1993 

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DISTANCE UPSTREAM FROM THE OHIO RIVER, IN KILOMETERS 

elevation ofthe water surface were evident as the river 

flowed through navigation dams between 800 and 1,358 

km upstream from the Ohio River. By this time, some 

dams were operational and were again regulating the 

river. 

Flood-Wave Routing 

Many methods for routing a flood wave assume 

unsteady flow in an open channel and no significant 

tributary inflow, but these two assumptions are not 

applicable to the upper Mississippi River. During low 

water conditions when the river is regulated by navigation dams, a flood wave cannot propagate freely through 

an open channel . However, flood waves can propagate 

freely in an open channel during high water conditions 

when the navigation dams no longer control the water 

level. During spring and late fall 1992, when the water 

discharge was closer to mean conditions, the periods of 

high water or open channel typically lasted a few days 

and occurred only in short reaches of the river between 

some dams. During summer 1993, the periods of open 

channel were longer and encompassed the entire reach of 

river from Minneapolis to Cairo, with the exception of 

the hydroelectric power dam at Keokuk (fig. 4). Tributary inflow to the upper Mississippi River was significant 

and had two effects on the flood wave. First, tributary 

inflow produced several secondary peaks and increased 

the magnitude of the maximum discharge flood peak as 

distance increased downstream (fig . 5). This contrasts 

with the assumption made by many routing methods that 

there is a single flood peak and that the magnitude of the 

peak is constant or decreases in the downstream direction 

(Gilcrest, 1950; Lawler, 1964). Second, the wave-propagation speed (phase speed or speed of the stage or discharge peak) was determined by the tributary inflows 

rather than the hydraulic characteristics of the channel. 

Figure 3. Composite flood wave on the upper Mississippi River. 

A, Shape of the flood wave for June 25 was based on water-level 

elevations from 78 stations . Data were furnished by the U.S . 

Army Corps of Engineers in the St. Paul, the Rock Island, and the 

St. Louis Districts; B, The water-level heights above an arbitrary 

plane with slope equal to the average river slope of 91 x10-6 . The 

flood wave propagates downstream between June 25 and 

August 1, but its height at the hydroelectric damat Keokuk, Iowa 

(at about 600 km), is held constant . The second large peak for 

August 1 is the Missouri River flood peak; C Some individual discharge flood waves for tributaries upstream from Keokuk . They 

are plotted for June 25 by assuming that the daily mean discharge moves 0.7 meter per second. The summation of these 

tributary flood waves approximates the solid-line curve in 8. 

6 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
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Ford Dam at Minneapolis, Minn . A 1992 = 

1,200 Lake Pepin, Minn. and Wis. 5A 

1,000 10 

800 15 

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600 

400 

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JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 4. Periods of open channel for the upper Mississippi River. A, 1992; 8, 1993. Blue represents times when 

all control gates in the navigation dam were out of the water. Information was furnished by U.S . Army Corps of 

Engineers in the St . Paul, the Rock Island, and the St . Louis Districts. 

The flood-wave routing method used in this 

paper for the upper Mississippi River, therefore, 

assumed a steady, open-channel flow only from June 

through August 1993 and only along short reaches of 

the river between tributaries. The travel times within 

these reaches were based on field data published by 

the U.S . Army Corps of Engineers for the upper Mississippi River (table 1 ; Institute of River Studies, 

1983) and the conservation of mass at upper Mississippi River stream-gaging stations . The steady openchannel flow was increased abruptly by inflow from 

tributaries or decreased abruptly by outflow to floodplain storage . Following these abrupt gains or losses 

of water, steady open-channel flow was assumed to 

resume until the next tributary downstream entered 

the upper Mississippi River. 

Acknowledgments 

The discharge information used to prepare this 

report was provided by many U.S. Geological Survey 

personnel from the Minnesota, the Wisconsin, the 

Iowa, the Illinois, and the Missouri Districts. Although 

Introduction 7 
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Mississippi River€ St. Louis, Missouri 

Keokuk, Iowa 

Clinton, Iowa 

McGregor, Iowa 

Prescott, Wisconsin 

St. Paul, Minnesota 

Anoka, Minnesota 

. . . . . . . ... . . . . . II- / 

. . . .... . . . . . . . . . . ... . . . . . .. 

. ._ . . 

. . . . . . .. . . . . .... . . . . . . . . . . 

April May June July August 

1993 

Figure 5. Daily mean water discharges at seven stream-gaging stations on the upper Mississippi River from April through August 1993. 

working extra hours during the flood period, they still 

took time to satisfy numerous requests for the data 

required to make the calculations of percent composition of the flood wave. 

The U.S . Army Corps of Engineers provided 

most of the stage information for at least 50 stations 

along the upper Mississippi River. Several requests 

required considerable time to fulfill or required search 

ing of archived records . Some of these very helpful 

people were E.G. Eaton and K.W. Willus in the St. 

Paul District ; W.H. Koelner, J.D. Bledsoe, B .J . Goodrum, G.F. Gitter, and K.W. Finch in the Rock Island 

District; D.M. Coleman, S .G. Farkas, and R.J . Kopsky, 

Jr ., in the St. Louis District ; and S.A. Lehr and H.W. 

Barton in the Memphis District. 

The water-level information along Illinois 

Route 3 in Alexander County, Illinois, behind the East 

Cape Girardeau levee, was provided by K.L. Bartelsm 

eyer and B .G. Stout, Jr., of the Illinois Department of 

Transportation, Division of Highways. 

Discussions with J.F. Sullivan of the Wisconsin 

Department of Natural Resources were instrumental in 

the conception of this chapter . 

FLOOD-WAVE PROPAGATION 

Hydrologic factors, such as tributary inflow or 

flood-plain storage, were more important than hydraulic factors, such as water depth, channel width, and 

channel roughness, in determining the flood-wave 

propagation speed. Water speed is not the same as 

wave-propagation speed. The wave-propagation speed 

was determined from the times and locations of maximum stages or discharges in the regulated reach of the 

upper Mississippi River. The general observed wavepropagation speed was 0.58 m/s for open-channel conditions during the 1993 flood (fig . 6) . This compares 

closely with the wave-propagation speed of 0.52 m/s 

calculated from measurements given by Seddon 

(1900) for the upper Mississippi River flood of April 

1881 when no navigation dams were present . 

Tributary Inflow 

The peak inflow from the tributaries of the 

upper Mississippi River upstream from the Illinois 

and the Missouri Rivers was nearly synchronous with 

the arrival of the flood wave from upstream because 

the areas of intense rainfall moved southward as the 

summer progressed (Wahl and others, 1993). This pattern of inflow contrasts with the inflow from the Illinois and the Missouri Rivers, which lagged behind the 

arrival of the upper Mississippi River flood wave by 

about 2 weeks and caused the wave-propagation 

speed to decrease from 0.58 to about 0.08 m/s (fig . 6). 

The average wave-propagation speed in the open8 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
Q

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900 

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-

0 I . . . . . . . . . . . . . . . . . . .  I . . . . . . . . ~\ . . . . . . . . 1. I, 

June July August 

1993 

Figure 6. Times and locations of maximum stages and discharges during the 1993 flood on the upper Mississippi River. Maximum stages are shown by open circles, and maximum discharges, by solid circles . The 

times and locations of maximum discharges for the tributary are labeled. The three segments of the dashed 

line were fit visually to show the general trend. The slope of the three line segments is an estimate of the 

flood-wave propagation speeds and are equal to 0.58, 0.08, and 0.42 m/s. 

channel reach from St. Louis to Thebes increased to 

about 0.42 m/s (fig . 6); this still was much, less than 

the average of 1.6 m/s for previous high-water events 

in 1993 (table 2). Along some reaches, however (for 

example, 300-400,700-800,900-1,100, and 1,100-

1,200 km upstream from the Ohio River), the wavepropagation speed was much higher than 0.58 m/s. 

This higher speed usually was caused by the arrival of 

the tributary inflow at the downstream end of a reach 

of the upper Mississippi River at the same time that 

the flood wave was arriving at the upstream end of the 

same reach. Consequently, the time of maximum 

stage or discharge coincided nearly simultaneously 

along the entire reach of the river and resulted in high 

wave-propagation speeds . 

An estimate of the wave-propagation speed 

for a simple kinematic wave in an open channel is the 

slope of the regression line for a plot of discharge as 

a function of cross-sectional area (Gilcrest, 1950). 

These estimates of the predicted kinematic wavepropagation speed for stations on the upper Mississippi River (table 2) generally differ from the speeds 

observed during the flood of 1993 and the speeds calculated from measurements during previous highwater events. This is because the significant tributary 

inflow, not the hydraulic factors, determined the propagation speed of the flood wave, and numerous levee 

breaks and seepage under and through the levees 

delayed the arrival of the flood wave downstream by 

removing water from the river and storing it on the 

flood plain. 

Flood-Wave Propagation 9 
Table 2. Flood-wave propagation speeds on the upper Mississippi River 

[km, kilometer; m/s, meter per second; numbers following ± symbol are standard deviations] 

Distance upstream Wave propagation speed (m/s) Upper Mississippi River stream-gaging from the Ohio River 

Predicted' stations Observed 1993 Previous high water

(km) flood2 events3 

Regulated river : 

Prescott, Wis. . . . . . . . . . . . . . . . . . . 1,306 0.92±0.73 0.58 

No data . 

Winona, Minn. . . . . . . . . . . . . . . . . . 1,168 .91-1 .4 .58 

Do. 

. . . . . . . . . . . . . Pool 8, Wis./Minn.4 1,097-1,102 .69 .58 

Do. 

McGregor, Iowa . . . . . . . . . . . . . . . . 1,019 .88± .06 .58 

0.59 

Clinton, Iowa . . . . . . . . . . . . . . . . . . 823 2.3± .21 .58 

1 .86 

Keokuk, Iowa . . . . . . . . . . . . . . . . . . 582 1 .9± .15 .58 

Open river : .65 

St. Louis, Mo. . . . . . . . . . . . . . . . . . 289 3 .0± .30 .42 

1 .3±0 .3 

Chester, Ill . . . . . . . . . . . . . . . . . . . . 177 2 .1± .12 .42 

1 .9± .8 

Thebes, Ill . . . . . . . . . . . . . . . . . . . . . 70 3 .9± .28 .42 

'From the slope of a regression line of measured discharge as function of a cross-sectional area . 

2From slope of dashed lines (fig. 6), which is an average over several stream-gaging stations but listed for each station as the same value . 

3From measurements of historic high water events of various magnitude previous to the flood of 1993 in the regulated river reach (Institute of River 

Studies, 1983, Plate II) and for seven events previous to the flood of 1993 in the open-channel reach . 

4 Based on three measurements at different locations made on July 14 and October 18, 1991, and April 16, 1992 . 

Flood-Plain Storage 

During the flood of 1993, water was stored on 

flood plains because of two mechanisms-levee breaks 

and levee seepage. No levee breaks occurred upstream 

from Clinton, a few occurred between Clinton and St. 

Louis, but the largest levee breaks occurred downstream from St. Louis and caused a delay in the arrival 

of the discharge flood peak at Thebes. 

Levee Breaks 

Among the most dramatic pictures seen on 

television and in the newspapers during the upper 

Mississippi River flood of 1993 were those of 

floodwaters raging through levee breaks and flooding 

adjacent flood plains . The floodwalls that protect St. 

Louis and East St. Louis, Illinois, held throughout the 

flood and confined the river to a narrow channel near 

the Gateway Arch at St. Louis. However, many levees 

failed downstream from St. Louis (table 3) and allowed 

water to flow onto the flood plain, thus decreasing the 

discharge of the river at Thebes where natural bluffs 

again confined the floodwaters to a narrow channel. 

The plot of water discharge at St. Louis (fig . 7) has 

been lagged 2 days (on the basis of the wavepropagation speed of previous high-water events in 

1993) so that the two red shaded areas (in July and 

August) between the water-discharge graphs for St. 

Louis and Thebes represent the water volume stored 

on the flood plain between St. Louis and Thebes. 

These volumes of water stored on flood plains (fig . 7) 

between St. Louis and Thebes were estimated to be 

1 .36 x 109 m3 during July and an additional 

1 .54 x 109 m3 during August. The volume of water 

stored on flood plains also can be estimated by using 

the approximate area protected by the levees that 

broke and an assumed average depth (table 3) . A 

generous estimate of the average depth is 6 m, but this 

is still not enough to account for all the water stored 

on the flood plain, which is based on the difference in 

10 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
Table 3. Some levee breaks on the upper Mississippi River, July and August 1993 

[km, kilometer ; kmz, square kilometer ; m3, cubic meter; m, meter. Information between St. Louis, Missouri, and Thebes, Illinois, was provided by S .G. Farkas, 

U.S . Army Corps of Engineers, St . Louis District ; information between Clinton and Keokuk, Iowa, was supplied by G.F. Gitter, U.S . Army Corps of Engineers,

Rock Island District, November 19931 

Distance of levee Approximate volume of water stored 

break upstream Date of break Approximate 

on the flood plain for various assumed 

depths Levee from the Ohio 1993 area protected (109 m) River (km2) 

2-m deep 4-m deep 6-m deep 

Clinton to Keokuk, Iowa 

Green Island . . . . . . . . . . . . . . . . 879-882 July 2 29 0.06 0.12 0.17 

Henderson Co. No. 3 . . . . . . . . . 663-668 July 1 9 .02 .04 .05 

Green Bay . . . . . . . . . . . . . . . . . . 623-637 July 10 55 .11 .22 .33 

Keokuk, Iowa, to St. Louis, Missouri 

Meyer . . . . . . . . . . . . . . . . . . . . . 550-576 July 9 40 0.08 0.16 0.24 

Indian Grave South and North . . 531-550 July 13 69 .14 .28 .41 

Sny . . . . . . . . . . . . . . . . . . . . . . . 478-507 July 25 445 .89 1 .78 2.67 

St. Louis, Missouri, to Cairo, Illinois 

St . Genevieve . . . . . . . . . . . . . . . 196 July 18 28 0.06 0.11 0.17 

Kaskaskia . . . . . . . . . . . . . . . . . . 179 July 22 38 .08 .15 .23 

Bois Brule . . . . . . . . . . . . . . . . . . 156 July 25 106 .21 .42 .64 

Subtotal for July levee 174 0.35 0.68 1 .04 

breaks . 

Columbia . . . . . . . . . . . . . . . . . . 265 August 1 57 0.11 0.23 .34 

Harrisonvillel . . . . . . . . . . . . . . . 249 August 2 188 .38 .75 1 .13 

Subtotal for August levee 

breaks . 

'Later breached deliberately at river kilometer 212. 

the discharge graphs for St. Louis and Thebes (fig . 7). 

The levee breaks, therefore, probably do not account 

for all the water stored on the flood plain; additional 

water was stored by seepage through and under levees 

that did not fail. 

Levee Seepage 

Although the levee breaks made national news, 

the seepage of water through and under the levees also 

was important. Levee breaks happen suddenly and 

allow rapid inundation of the flood plain, whereas 

seepage continues steadily for as long as the river 

level is higher than that of the water in the adjacent 

245 0.49 0.98 1 .47 

flood plain protected by the levee. Seepage can continue long after the flood peak in the river has passed 

the levee (fig . 8). For example, although the flood peak 

passed Thebes on August 7, water continued to seep 

under the 51-km-long levee that protected the East 

Cape Girardeau (an area of 38 km2) and the Clear 

Creek (an area of 73 km2) Levee Districts, which are 

just upstream from Thebes, until September 25. The 

seepage slowly raised the water level an additional 0.6 

m (B.G. Stout, Illinois Department of Transportation, 

written commun., 1993) . The water level behind the 

levees rose even as the river level was falling and in 

spite of pumps that were operating to lower the water 

level. Homes and businesses behind the levees that 

Flood-Wave Propagation 1 1 
32,000 

0 

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a 28,000 

ii 

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W 

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DATE OF MAJOR LEVEE BREAK AND APPROXIMATE 

AREA EACH LEVEE PROTECTED, IN SQUARE KILOMETERS 

m m m co o n m N M r Nr 

July August 

1993 

Figure 7. Daily mean discharge of the upper Mississippi River at 

St. Louis, Missouri, and at Thebes, Illinois . The discharge at St. 

Louis was plotted 2 days later to compensate for the travel time 

of water between the two stations . The red shaded area represents the volume of water lost between St. Louis and Thebes. 

For July, this volume was 1 .36 x 109 cubic meters, and for 

August, it was 1 .54 x 109 cubic meters . 

were dry on August 7 were flooded on September 25. 

No measurements of the water level were made after 

September 25, but the water level probably rose a little higher when a minor flood peak passed Thebes on 

October 2. The river level did not drop sufficiently 

below the water level behind the levees until October 11, when the gates in the levees were opened, and 

the water began to drain back into the river (R.R. 

Colyer, East Cape Girardeau Levee District, oral commun., 1993) . If a conservative mean water depth of 

about I m is assumed, then the volume of water 

stored on the flood plain in these levee districts must 

have been about 0.1 x 109 m3. If seepage in other 

levee districts along the 217 km of river between St. 

Louis and Thebes is allowed for, then an additional 

0.2 to 0.3 x 109 m3 of water may have been stored on 

the flood plain. This volume, when added to the 

water stored from the levee breaks, may account for 

the difference in discharge between St. Louis and 

Thebes (fig. 7). The storage of water on the flood 

plain explains the observation that the wave-propagation speed between St. Louis and Thebes was slower 

than the predicted speeds or the measured speeds of 

previous high-water events that had no discharge 

losses caused by levee breaks or seepage (table 2) . 

FLOOD-WAVE COMPOSITION 

A water budget was constructed by computing 

the discharge contribution from upstream tributaries to 

the flood wave and comparing it to the measured dis 

charge at five primary stream-gaging stations on the 

upper Mississippi River-Prescott, Winona, Clinton, 

Keokuk, and St. Louis. For computations of tributary 

contributions during open-channel conditions from June 

through August discharges of tributaries and the discharges at stream-gaging stations on the upper Mississippi River upstream from the primary gaging station 

were lagged relative to the downstream primary gaging 

station (see travel times in table 1). The tributary and 

upstream contributions were computed as percentages 

of the reported daily mean discharge at the primary station (table 4) and not as percentages of the sum of all 

tributaries and the upstream lagged discharges. Therefore, if some of the water that passed an upstream tributary gaging station was later stored on the flood plain 

and did not reach the downstream primary station, then 

the sum of the percentages could be greater than 100, 

and the amount that is greater than 100 percent represents stored water (figs . 9-13). 

The error in this percentage computation is a 

function of the error in estimating the lag time, the 

error in the rating curve for each stream-gaging station, 

106 

105 Mississippi River at Thebes, Illinois w 

WJ 

104 

0 

a 103 

W 

102 z 

J 

W 

WJ 

Q 

100 

99 

July August September October 

1993 

Figure 8. Water levels for the Mississippi River near Thebes, Illinois (black line), and for the adjacent East Cape Girardeau and 

Clear Creek Levee Districts (red line) from July through October 

1993. The water level in the Levee Districts probably peaked

between September 25 and October 11 (dashed extension of red 

line). Water levels inside the levee were supplied by B. G. Stout, 

Jr., of the Illinois Department of Transportation . 

1 2 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
The photograph of the truck above was taken on August 16, 

1993, and the one below was taken on October 11, 1993, within 

the East Cape Girardeau Levee District. See figure 8 for water 

levels inside the levee district. Photographs were supplied by

R.H . Meade, U.S . Geological Surrey. 

and the number of tributaries . The error in estimating 

the lag time is proportional to the change in discharge 

with time (for a specific tributary or upstream gaging 

station) and weighted by the fraction of the total discharge contributed by the tributary or upstream gaging 

station . At most tributary and upstream gaging stations, the discharge changed slowly with time. However, for some tributary stations, the change in 

discharge with time was large, although the fraction of 

the total discharge contributed by these tributaries was 

often small and compensated for the large change in 

discharge with time. Assuming that the rating curve 

error was 5 percent, a few estimates of the error in the 

percentage computation were made for a range of discharges of the upper Mississippi River at Prescott and 

St. Louis. At Prescott these errors were slightly larger 

(7-15 percent) than those at St. Louis (7-10 percent). 

Mississippi River at Prescott, Wisconsin 

The daily mean discharge of two tributaries, the 

Minnesota and the St. Croix Rivers, accounted for 50 

to 90 percent of the daily mean discharge at Prescott 

during June and July ; the maximum daily mean discharge (3,680 m3 /s, or 7.5 times the mean discharge) at 

Prescott was measured on June 27 (fig . 9). The maximum daily mean discharge of the Minnesota River 

near Jordan, Minnesota, was 24 times the mean discharge, but the maximum daily mean discharge of the 

St. Croix River at St. Croix Falls, Wisconsin, was only 

4.3 times the mean discharge. About 3 percent of the 

unaccounted discharge of the Mississippi River at Prescott is from ungaged tributaries (J .H. Hess, U.S. Geological Survey, oral commun., 1994) . 

Mississippi River at Winona, Minnesota 

Many ofthe small tributaries of the upper Mississippi River between Prescott and Winona are 

ungaged ; the percentage of the discharge contributed by 

these tributaries is unknown and probably explains why 

the total percentages at Winona usually are less than 95 

percent (fig . 10) . The Vermillion, the Cannon, the Zumbro, and the Whitewater Rivers, which have stream 

gages on either their main stems or some of their tributaries, accounted for 1 to 7 percent of the water that 

flowed past Winona. The major tributary that entered 

the upper Mississippi River between Prescott and 

Winona is the Chippewa River, which reached a maximum daily mean discharge (2,400 m3/s, or 11 times the 

mean discharge) on June 23. This discharge flood peak 

arrived at Winona on June 24 and accounted for 56 percent of the water that passed Winona on that day. Discharge of the Mississippi River at Prescott accounted 

for 43 to 79 percent of the water that passed Winona in 

June and for 71 to 83 percent in July. 

Mississippi River at Clinton, Iowa 

The discharge from many small tributaries must 

be considered in an accounting of all the water that 

flowed past Clinton . The Black and the Wisconsin Riv 

ers are the main tributaries between Winona and Clinton, but the combined discharge from the Trempealeau, 

the Root, the upper Iowa, the Turkey, the Grant, the 

Platte, and the Maquoketa Rivers accounted for 6 to 20 

percent of the water that flowed past Clinton . Total discharge contributions were greater than 100 percent of 

Flood-Wave Composition 1 3 
5

10

15

20

25

30

-- --- -- ---

Table 4. Daily mean discharges for the Upper Mississippi River and some of its tributaries, June through August 1993 

[Discharge values in cubic meters per second; station number is a unique U.S . Geological Survey identification number; some discharge values are 

provisional and may differ from later data published in the U.S . Geological Survey's Water-Data Reports; - - -, no data ; e, estimate] 

Mississippi River near 

Anoka, Minnesota, 

Day station number 

05288500 

June July August 

1 564 750 518 

2 600 753 493 

3 623 759 484 

4 623 790 450 

606 801 442 

6 583 833 419 

7 558 872 408 

8 535 929 394 

9 507 946 419 

479 966 396 

11 450 974 374 

12 425 952 362 

13 422 920 348 

14 405 920 354 

394 898 377 

16 385 878 365 

17 445 861 343 

18 445 835 365 

19 459 793 399 

470 750 388 

21 493 716 382 

22 515 685 391 

23 544 663 402 

24 620 649 399 

694 640 396 

26 739 612 399 

27 762 586 422 

28 770 572 436 

29 762 549 433 

762 530 433 

31 521 436 

Minnesota River near 

Jordan, Minnesota, 

station number 

05330000 

June July August 

467 1,590 736 

476 1,450 739 

498 1,330 742 

527 1,300 736 

555 1,310 725 

581 1,340 716 

598 1,390 705 

603 1,460 694 

598 1,470 683 

592 1,440 654 

592 1,390 626 

603 1,310 603 

626 1,240 583 

657 1,170 572 

663 1,100 572 

649 1,050 583 

705 1,000 657 

884 980 782 

1,070 957 915 

1,290 935 1,020 

1,680 906 1,040 

2,150 869 1,000 

2,430 847 932 

2,570 824 861 

2,570 804 801 

2,440 787 748 

2,290 762 700 

2,120 745 646 

1,950 731 609 

1,770 722 586 

725 569 

St . Croix River at Mississippi River at 

St. Croix Falls, Wisconsin, Prescott, Wisconsin, 

station number station number 

05340500 05344500 

June July August June July August 

368 266 91 1,400 3,140 1,570 

388 294 85 1,450 2,970 1,540 

365 261 84 1,520 2,920 1,510 

331 286 78 1,540 2,800 1,490 

292 331 75 1,550 2,780 1,470 

255 351 85 1,530 2,780 1,440 

230 348 82 1,510 2,780 1,420 

219 320 65 1,490 2,800 1,400 

231 306 99 1,470 2,860 1,380 

277 382 79 1,470 2,890 1,500 

334 419 73 1,480 3,030 1,400 

317 413 76 1,500 3,090 1,210 

271 354 76 1,460 3,030 1,160 

255 292 73 1,400 2,890 1,130 

262 264 92 1,400 2,760 1,090 

254 240 81 1,420 2,660 1,100 

273 223 79 1,420 2,570 1,120 

232 200 86 1,420 2,470 1,120 

219 184 95 1,550 2,380 1,180 

233 170 93 1,680 2,310 1,340 

239 167 78 1,870 2,230 1,520 

271 140 80 2,070 2,160 1,600 

278 121 100 2,380 2,080 1,620 

374 130 86 2,730 1,990 1,610 

459 121 94 3,140 1,940 1,530 

558 123 89 3,430 1,900 1,460 

558 110 91 3,680 1,840 1,390 

464 105 86 3,620 1,760 1,330 

396 97 99 3,480 1,700 1,300 

328 91 98 3,310 1,640 1,270 

98 103 1,580 1,230 

1 4 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
5

10

15

20

25

30

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

Table 4. Daily mean discharges for the Upper Mississippi River and some of its tributaries, June through August 1993-

Continued 

Chippewa River at Mississippi River at Black River near Wisconsin River at 

Durand, Wisconsin, Winona, Minnesota, Galesville, Wisconsin, Muscoda, Wisconsin, 

Day station number 

05369500 

station number 

05378500 

station number 

05382000 

station number 

05407000 

June July August June July August June July August June July August 

1 467 374 158 1,990 4,500 2,060 166 94 52 309 600 289 

2 589 365 197 2,010 4,470 2,040 311 128 87 354 555 279 

3 552 348 252 2,070 4,390 1,940 245 154 112 530 473 270 

4 385 402 211 2,140 4,250 1,840 150 197 104 623 433 270 

328 371 174 2,160 4,130 1,820 96 203 80 629 450 279 

6 274 374 143 2,140 4,020 1,830 68 196 67 566 518 276 

7 245 354 163 2,110 3,940 1,830 62 152 59 445 580 264 

8 311 328 116 2,060 3,790 1,860 63 119 54 456 597 245 

9 289 345 186 2,040 3,710 1,900 79 106 54 436 634 218 

382 337 368 2,020 3,650 1,890 162 99 61 425 682 235 

11 436 345 365 2,040 3,620 1,930 408 96 101 538 660 246 

12 413 343 309 2,050 3,650 2,000 462 88 107 677 597 240 

13 385 326 232 2,060 3,710 2,020 340 84 90 773 547 237 

14 345 273 189 2,070 3,710 1,950 215 80 72 827 532 238 

323 283 138 2,080 3,710 1,890 134 78 64 850 481 289 

16 314 262 176 2,050 3,620 1,790 108 75 63 827 439 323 

17 328 231 184 2,040 3,540 1,720 106 68 62 759 436 340 

18 558 226 179 2,130 3,460 1,740 145 66 61 716 442 311 

19 847 184 163 2,360 3,310 1,770 331 64 58 682 510 283 

1,040 232 161 2,800 3,200 1,820 801 64 54 722 462 273 

21 1,350 187 135 3,140 3,060 1,870 1,540 58 50 838 430 261 

22 2,150 176 120 3,460 2,920 1,880 1,350 56 47 971 411 246 

23 2,400 160 126 3,770 2,800 1,880 869 54 44 1,190 382 249 

24 1,800 159 136 4,250 2,680 1,910 572 51 43 1,420 354 220 

1,190 117 148 4,640 2,590 1,990 422 51 40 1,600 351 225 

26 833 110 140 4,760 2,480 2,030 300 56 39 1,670 354 236 

27 733 185 132 4,760 2,410 2,050 208 57 38 1,650 334 237 

28 586 154 126 4,700 2,340 2,050 146 72 38 1,410 348 227 

29 541 140 96 4,640 2,280 2,020 116 57 38 943 343 227 

530 148 117 4,590 2,190 2,000 104 51 45 665 320 229 

31 167 190 2,110 1,990 48 53 289 220 

Flood-Wave Composition 15 
5

10

15

20

25

30

--- --- -- --

Table 4. Daily mean discharges for the Upper Mississippi River and some of its tributaries, June through August 1993-

Continued 

Day 

Mississippi River at 

McGregor, Iowa, 

station number 

05389500 

Mississippi River at 

Clinton, Iowa, 

station number 

05420500 

Rock River near 

Joslin, Illinois, 

station number 

05446500 

Wapsipinicon River near 

De Witt, Iowa, 

station number 

05422000 

June July August June July August June July August June July August 

1 2,300 5,300 2,700 2,890 6,570 3,770 337 685 464 78 253 196 

2 2,320 5,210 2,620 2,920 6,630 3,710 331 776 456 75 250 177 

3 2,350 5,070 2,530 2,920 6,630 3,620 331 858 445 72 236 159 

4 2,420 4,960 2,460 2,920 6,570 3,430 326 901 428 72 237 136 

2,530 4,900 2,390 2,940 6,430 3,260 343 886 411 90 269 124 

6 2,610 4,810 2,340 3,000 6,540 3,170 377 799 399 91 348 118 

7 2,650 4,700 2,280 3,200 6,740 2,890 382 705 385 95 422 111 

8 2,660 4,560 2,220 3,480 6,710 2,920 436 657 385 165 541 105 

9 2,670 4,450 2,190 3,820 6,480 2,940 668 637 374 214 586 112 

2,630 4,330 2,170 3,880 6,370 3,000 923 643 388 214 467 188 

11 2,580 4,220 2,170 3,820 6,310 2,970 986 646 374 182 391 190 

12 2,550 4,130 2,210 3,740 6,230 2,920 929 640 377 168 365 194 

13 2,560 4,110 2,250 3,620 6,170 2,920 821 637 385 168 391 199 

14 2,690 4,110 2,280 3,620 6,090 2,860 733 643 360 168 513 195 

2,710 4,080 2,390 3,710 5,920 2,890 683 666 351 157 609 208 

16 2,640 4,050 2,500 3,710 5,690 2,890 680 677 346 162 575 233 

17 2,630 4,050 2,570 3,740 5,520 2,970 651 677 348 162 510 266 

18 2,620 4,020 2,590 3,910 5,440 3,260 612 677 337 159 532 264 

19 2,680 3,990 2,550 4,020 5,350 3,510 615 716 329 177 538 274 

2,830 3,940 2,480 4,130 5,350 3,740 680 753 317 200 544 314 

21 3,090 3,820 2,430 4,190 5,240 3,680 773 762 314 207 572 323 

22 3,430 3,710 2,400 4,220 5,130 3,540 793 750 314 203 507 314 

23 3,940 3,600 2,410 4,220 5,010 3,370 753 742 306 209 464 300 

24 4,280 3,450 2,400 4,300 4,900 3,230 719 700 303 217 433 289 

4,450 3,370 2,370 4,670 4,760 3,260 685 643 286 212 394 320 

26 4,640 3,260 2,340 5,010 4,640 3,260 649 595 292 198 337 371 

27 4,810 3,110 2,330 5,350 4,530 3,170 612 564 286 227 289 377 

28 4,980 3,030 2,350 5,660 4,390 3,090 600 535 276 286 274 365 

29 5,130 2,920 2,370 5,920 4,220 3,000 634 518 273 273 241 354 

5,270 2,830 2,400 6,290 4,080 3,140 649 498 292 281 225 354 

31 2,760 2,430 3,940 3,200 481 303 219 374 

16 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
5

10

15

20

25

30

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

Table 4. Daily mean discharges for the Upper Mississippi River and some of its tributaries, June through August 1993-

Continued 

Iowa River at Skunk River at Mississippi River at Des Moines River at 

Wapello, Iowa, Augusta, Iowa, Keokuk, Iowa, Keosauqua, Iowa, 

Day station number 

05465500 

station number 

05474000 

station number 

05474500 

station number 

05490500 

June July August June July August June July August June July August 

1 592 1,220 1,810 152 564 442 4,300 9,320 7,960 895 1,130 1,920 

2 578 1,350 1,730 151 561 419 4,250 9,460 7,110 920 1,030 1,780 

3 575 1,270 1,770 176 439 360 3,960 9,660 5,890 937 1,130 1,670 

4 600 1,160 1,680 272 343 328 4,250 9,850 6,850 963 1,240 1,570 

682 1,190 1,560 396 416 306 4,560 10,100 5,970 1,060 1,650 1,490 

6 708 1,630 1,400 354 600 283 4,560 10,500 5,780 917 2,240 1,420 

7 699 2,700 1,380 253 728 269 4,500 11,200 5,440 883 2,710 1,350 

8 864 3,000 1,380 527 903 255 4,640 11,100 5,070 1,420 2,680 1,290 

9 1,040 2,780 1,350 748 1,180 241 5,240 11,800 4,730 1,110 2,680 1,220 

1,070 2,340 1,420 691 1,300 413 5,800 12,300 5,130 881 2,680 1,320 

11 943 2,340 1,760 603 1,250 507 6,140 11,900 5,380 770 2,810 1,230 

12 892 2,490 2,050 320 1,120 674 6,230 11,900 6,170 716 2,920 1,340 

13 898 2,700 1,780 212 847 677 6,260 11,900 6,230 691 3,060 1,460 

14 960 2,890 1,480 197 654 572 5,780 11,700 6,340 674 3,030 1,350 

1,040 2,560 1,370 178 648 496 5,890 11,500 6,120 634 3,030 1,350 

16 1,070 2,230 1,590 165 583 725 5,780 11,400 6,090 606 3,000 1,320 

17 1,030 2,150 2,040 167 634 835 5,690 11,400 6,570 623 2,970 1,250 

18 932 2,170 2,200 163 617 835 5,660 11,200 6,680 637 2,890 1,180 

19 934 2,210 2,050 175 694 875 5,690 11,000 6,940 719 2,890 1,190 

1,060 2,420 1,980 275 731 855 5,780 10,900 6,940 779 2,860 1,480 

21 1,130 2,540 1,910 348 702 762 6,030 10,900 7,080 793 2,800 1,510 

22 1,190 2,320 1,990 320 671 702 6,200 11,000 7,050 872 2,690 1,360 

23 1,260 2,090 2,210 331 694 629 6,430 11,000 6,970 878 2,690 1,280 

24 1,200 2,580 2,200 425 787 566 6,570 11,200 6,940 883 2,680 1,230 

1,480 2,920 2,020 906 1,010 527 7,650 11,300 6,940 895 2,710 1,180 

26 1,750 2,780 1,830 722 1,110 456 7,870 11,400 6,680 883 2,640 1,140 

27 1,680 2,320 1,740 445 1,070 430 7,820 11,200 6,400 883 2,460 1,110 

28 1,620 2,070 1,630 371 946 470 8,100 10,900 6,230 883 2,270 1,080 

29 1,420 1,900 1,590 300 750 476 8,160 10,300 6,120 889 2,120 1,080 

1,220 1,810 1,600 354 566 430 8,550 10,300 5,950 1,010 2,010 1,160 

31 1,770 1,700 462 470 9,090 6,060 1,940 1,210 

Flood-Wave Composition 17 
5

10

15

20

25

30

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

Table 4. Daily mean discharges for the Upper Mississippi River and some of its tributaries, June through August 1993-

Continued 

Illinois River at Missouri River at Mississippi River at Mississippi River at 

Day 

Valley City, Illinois, 

station number 

05586100 

Hermann, Missouri, 

station number 

06934500 

St . Louis, Missouri, 

station number 

07010000 

Thebes, Illinois, 

station number 

07022000 

June July August June July August June July August June July August 

1 646 1,470 2,250 4,360 5,300 20,300 10,800 14,000 29,700 11,400 14,200 25,100 

2 612 1,640 1,880 4,280 6,660 18,500 10,600 14,600 29,200 11,200 14,300 25,500 

3 600 1,700 1,530 4,390 7,650 16,500 10,500 16,000 28,600 11,100 14,400 25,900 

4 657 1,710 1,510 4,360 8,210 14,500 10,200 17,100 28,000 10,900 14,900 26,000 

677 1,760 1,420 4,420 8,270 12,900 10,200 17,900 27,400 10,700 15,800 26,500 

6 711 1,800 1,520 4,810 8,330 11,800 10,300 18,600 26,400 10,600 16,700 27,400 

7 708 1,730 1,590 6,630 11,400 10,800 11,200 19,300 25,100 10,700 17,600 27,700 

8 660 1,720 1,580 6,740 11,800 10,300 12,400 20,600 23,700 11,100 18,700 27,300 

9 663 1,690 1,540 6,680 11,600 9,910 12,900 21,600 22,300 12,000 19,900 26,900 

694 1,610 1,530 6,320 10,300 9,540 13,000 22,200 21,600 12,800 21,000 26,200 

11 750 1,590e 1,480 5,920 9,710 9,290 12,800 22,800 20,900 13,100 21,500 25,600 

12 801 1,560e 1,460 5,580 9,370 9,290 12,700 22,800 20,800 13,200 22,100 24,900 

13 847 1,590e 1,480 5,130 9,400 10,500 12,600 22,100 20,700 13,100 22,600 24,100 

14 889 1,620 1,460 4,640 9,830 9,010 12,300 22,500 20,700 13,000 23,400 23,500 

935 1,640e 1,420 4,450 12,300 8,500 12,100 22,900 19,900 12,900 24,500 22,900 

16 986 1,670e 1,370 4,450 13,900 8,210 11,800 24,000 19,200 12,700 23,800 22,300 

17 1,030 1,640e 1,350 4,620 11,800 7,790 11,700 26,200 18,500 12,500 23,300 21,800 

18 1,070 1,590e 1,370 4,560 10,600 7,080 11,800 27,400 17,900 12,300 23,900 21,400 

19 1,110 1,540 1,420 4,280 10,100 6,230 11,700 27,600 17,300 12,200 24,700 20,800 

1,140 1,500e 1,460 4,250 9,830 5,580 11,500 27,500 16,600 12,100 25,300 20,000 

21 1,180 1,470e 1,420 4,250 9,540 5,270 11,600 25,600 15,900 12,000 25,200 19,400 

22 1,210 1,440e 1,380 4,360 9,290 5,130 11,500 25,700 15,300 11,900 25,200 18,700 

23 1,250 1,490e 1,320 4,810 9,120 5,210 11,600 25,500 15,000 11,900 24,800 18,000 

24 1,280 1,640 1,290 4,450 9,060 5,470 11,800 25,300 14,900 11,800 25,100 17,300 

1,340 1,770 1,250 5,270 9,830 5,240 12,000 24,900 14,900 12,000 24,500 16,800 

26 1,380 2,000 1,210 5,720 10,600 4,900 12,900 25,100 14,700 12,400 23,000 16,300 

27 1,370 2,090 1,170 4,900 10,900 4,670 13,400 24,700 14,400 12,700 23,600 15,900 

28 1,350 2,180 1,120 4,870 12,100 4,500 13,400 24,700 14,200 13,300 24,400 15,500 

29 1,280 2,250 1,060 5,100 14,500 4,280 13,800 25,000 13,900 13,700 25,100 15,200 

1,290 2,100 1,010 4,960 18,000 3,910 14,000 26,900 13,700 14,000 24,600 14,800 

31 2,200 971 20,900 3,910 28,900 13,300 24,700 14,500 

1 8 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
z Errorinflood-wave 5-percent error 

z 

0 

U 

3 

0 

0 

W 

a 

a 

W 

s 

W 

a

3 

a

0 

W 

0 

W 

0

a 

WW 

U 

W

a 

June 

1993 

Figure 9. Flood-wave composition of the Mississippi River at 

Prescott, Wisconsin. The amount of water is proportional to 

the vertical distance between successive curves . Pink represents discharge from ungaged smaller tributaries and any 

flood-wave routing errors of less than 100 percent. Red represents any flood-wave routing errors of more than 100 percent. 

the actual discharge at Clinton between June 26 and 

July 2 (fig . 11) . The sharp daily mean discharge peak of 

the Black River for June 21 (1,540 m3/s, or 31 times the 

mean discharge) was expected to reach Clinton about 

June 27; however, much of the peak discharge may 

have been stored on the flood-plain delta near the 

mouth of the Black River (J .F . Sullivan, Wisconsin 

Department of Natural Resources, oral commun., 1993) 

and did not reach Clinton until after July 2 (fig . 11). 

The Wisconsin River had a broad daily mean discharge 

peak (1,670 m3/s, or 6.8 times the mean discharge), 

which accounted for 16 to 28 percent of the daily mean 

discharge at Clinton between June 16 and July 2. The 

Mississippi River at Winona contributed from 49 to 80 

percent of the daily mean discharge at Clinton during 

June and July. 

Mississippi River at Keokuk, Iowa 

The Rock River reached a maximum earlier 

(June 11) than did most tributaries of the upper Mississippi River. The maximum daily mean discharge (986 

m3 /s,. or 5 .7 times the mean discharge) of the Rock 

River represented 17 percent of the daily mean discharge at Keokuk (fig . 12) . The combined discharge of 

the Iowa, the Skunk, and the Wapsipinicon Rivers in 

Iowa accounted for 17 to 48 percent of the daily mean 

discharge at Keokuk from June through August. The 

individual maximum daily mean discharges of these 

three tributaries arrived at Keokuk on or about July 10, 

July 11, and July 19. The discharge of the Mississippi 

River at Clinton accounted for less than 50 percent of 

the discharge at Keokuk after July 19, and the combined discharges of the Iowa, the Skunk, and the Wapsipinicon Rivers accounted for slowly increasing 

percentages of the discharge at Keokuk through 

August. 

Mississippi River at St. Louis, Missouri 

The discharges of the Des Moines and the Illinois Rivers each accounted for 5 to 12 percent of the 

daily mean discharge at St. Louis from June through 

August. The Mississippi River at Keokuk accounted 

for about 50 percent of the discharge at St. Louis with 

a maximum of 54 percent on July 13 and 14. In early 

August, the Mississippi River at Keokuk accounted 

120 

0 Error in flood-wave 5-percent error 

- routing in discharge 10 .--__-___--->_4-------t--____-------- " _

z Z 100 

z Ungaged_,\ tributaries 

0 

W 

a 

0 60 Mississippi River 

W 

0 

W 

z 

W 

U 

a 

1993 

Figure 10. Flood-wave composition of the Mississippi River at 

Winona, Minnesota. The amount of water is proportional to 

the vertical distance between successive curves. Pink represents discharge from ungaged smaller tributaries and any 

flood-wave routing errors of less than 100 percent. Red represents any flood-wave routing errors of more than 100 percent. 

The four tributaries are the Vermillion, the Cannon, the Zumbro, and the White Water. 

Flood-Wave Composition 19 
a

140 

3 

z

0 

z 

J 100 a 

w 

a 

U 80 

s 

w

Fa 60
 3
J


F

O

F 

0 

F

z 

w 20 

w 

a 

0 

- Error in flood-wave 

routing or water 

- stored on flood plain 

Ungaged tributaries 

and return flow 

Mississippi River 

1993 

Figure 11 . Flood-wave composition of the Mississippi River 

at Clinton, Iowa. The amount of water is proportional to the 

vertical distance between successive curves. Pink represents discharge from ungaged smaller tributaries, any flood_ 

wave routing errors of less than 100 percent, or return flow 

to the upper Mississippi River. Red represents flood-wave 

routing errors of more than 100 percent or water that did not 

arrive at Clinton because of flood-plain storage . The seven 

tributaries are the Trempealeau, the Grant, and the Platte in 

Wisconsin, the Root in Minnesota, and the upper Iowa, the 

Turkey, and the Maquoketa in Iowa. 

for only about 21 percent of the discharge at St. Louis 

due to large contributions from the Missouri River. 

However, in late August, this percentage again 

increased to about 50 percent due to decreasing contributions (about 30 percent) from the Missouri 

River. The Missouri River contributed a maximum 

percentage (70 percent) of the discharge at St. Louis 

on August 1 and 2, which are the dates the flood peak 

passed St. Louis. Significant amounts of water (10­

20 percent of the discharge measured at St. Louis) 

did not reach St. Louis as a result of flow through 

major levee breaks onto the flood plain at upstream 

sites (table 3) . The Meyer and the Indian Grave South 

and North levees were breached on July 9 and July 

13, respectively, and flow through these breaks probably accounted for some of the water that did not 

reach St. Louis between July 10 and July 17 (fig . 13) . 

The Sny levee was breached on July 25 after a long 

battle to save it (Stewart, 1993). Flow through this 

breach probably accounted for the additional water 

that was stored and did not reach St. Louis between 

July 28 and August 4. Some of the water stored on 

the flood plain drained back to the river (fig . 13) and 

represented the "missing" water that could not be 

accounted for by the Illinois, the Des Moines, and the 

Missouri Rivers or by the Mississippi River at 

Keokuk. 

SUMMARY 

The flood wave that propagated down the 

upper Mississippi River from June through August 

1993 was a composite of individual tributary flood 

waves. The average wave-propagation speed in the 

river was about 0.58 m/s upstream from St. Louis and 

about 0.42 m/s downstream from St. Louis. 

The wave-propagation speed was determined 

primarily by hydrologic factors, such as tributary 

inflow and flood-plain storage, rather than by hydrau 

lic factors, such as water depth, channel width, and 

channel roughness . Flow through levee breaks 

accounted for most of the flood-plain storage on the 

upper Mississippi River, but levee seepage also was 

significant, especially in its impact on human activiError in flood-wave 

a routing or water 

0 5-percent error stored on flood plain 

in discharge 

Y 

O 

w

Y 

Q 

U

u)s 

Q 

J 

a 

0

F 

0 

w 

aF

Z 

U 

1993 

Figure 12. Flood-wave composition of Mississippi River at 

Keokuk, Iowa. The amount of water is proportional to the 

vertical distance between successive curves. Pink represents discharge from ungaged smaller tributaries, any floodwave routing errors of less than 100 percent, or return flow 

to the upper Mississippi River. Red represents flood-wave 

routing errors of more than 100 percent or water that did not 

arrive at Keokuk because of flood-plain storage . 

20 Propagation and Composition of the Flood Wave on the Upper Mississippi River, 1993 
O 

s

0 

F 

a 

W 

a 

0

to 

0 

w 

a

3 

a 

0 

0

W 

a 

WWU 

W 

a 

routing or water 

stored on flood plain 5-percent error 

in discharge 

June July August 

1993 

Figure 13. Flood-wave composition of Mississippi River at 

St . Louis, Missouri . The amount of water is proportional to 

the vertical distance between successive curves. Pink represents discharge from ungaged smaller tributaries, any floodwave routing errors of less than 100 percent, or return flow 

to the upper Mississippi River. Red represents flood-wave 

routing errors of more than 100 percent or water that did not 

arrive at Keokuk because of flood-plain storage. 

ties . Seepage through and under levees continued 

long after the peak of the composite flood wave in 

the river had passed, which caused extended periods 

of inundation. 

The flood wave peaked twice as it passed St. 

Louis during July and August. The first discharge 

peak of 27,600 m3/s on July 19 comprised about 

equal amounts (40 percent) of upper Mississippi and 

Missouri River water. A second and larger discharge 

of 29,700 m3/s peaked on August 1 ; the Missouri 

River accounted for about 70 percent of the total discharge, or about twice the discharge contributed by 

the Mississippi River at Keokuk. 

SELECTED REFERENCES 

Gilcrest, B.R., 1950, Flood routing, in Rouse, Hunter, ed., 

Engineering hydraulics, chap. 10-Proceedings of 

the 4th Hydraulics Conference, June 12-15, 1949, 

Iowa Institute of Hydraulic Research: New York, 

John Wiley, p. 635-710. 

Institute of River Studies, 1983, Time of travel estimates 

for selected streams in Missouri, Iowa, and Illinois : 

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

Louis District potamology study (S-17), 237 p. 

Lawler, E.A., 1964, Flood routing, pt . 2 of Hydrology of 

flow control, in Chow, V.T., ed., Handbook of 

applied hydrology: New York, McGraw-Hill, p. 25-

34-25-59. 

Moody, J.A., and Meade, R.H., 1992, Hydrologic and sedimentologic data collected during three cruises at low 

water on the Mississippi River and some of its tribu 

taries, July 1987-June 1988: U.S . Geological Survey 

Open-File Report 91-485, 143 p. 

Parrett, Charles, Melcher, N.B ., and James, R.W., Jr., 

1993, Flood discharges in the upper Mississippi 

River Basin, 1993, in Floods in the upper Mississippi 

River Basin, 1993: U.S . Geological Survey Circular 

1120-A, 14 p. 

Seddon, J.A., 1900, River hydraulics: Transactions of the 

American Society of Civil Engineers, v. 43, p. 179-

243. 

Stewart, J.B., 1993, Battle on the Sny: The New Yorker, v. 

69, no. 25, August 9, 1993, p. 30-40. 

U.S . Army Corps of Engineers, 1990, The upper Mississippi River nine-foot channel : Washington, D.C., 

U.S . Government Printing Office, 2 p. 

U.S. Geological Survey, 1989, Water-resources data for 

Illinois, water years 1989-1990 : U.S . Geological Survey Water-Data Reports IL-89-1 and IL- 90-1, vol 

umes 1 and 2 (published annually) . 

1989, Water-resources data for Iowa, water year 

1989: U.S . Geological Survey Water-Data Report 

IA-89-1 (published annually) . 

1988, Water-resources data for Minnesota, water 

year 1988: U.S . Geological Survey Water-Data 

Reports MN-88-1 (published annually) . 

.1989, Water-resources data for Missouri, water year 

1989: U.S . Geological Survey Water-Data Report 

MO-89-1 (published annually) . 

1989, Water-resources data for Wisconsin, water 

year 1989: U.S . Geological Survey Water-Data 

Report WI-89-1 (published annually) . 

Wahl, K.L., Vining, K.C., and Wiche, G.J ., 1993, Precipitation in the upper Mississippi River Basin, January 1 

through July 31, 1993, in Floods in the upper Missis 

sippi River Basin, 1993: U.S . Geological Survey Circular 1120-B, 1 0 p.