Ohio River Backwater Flood-Inundation Maps 

for the Saline and Wabash Rivers in Southern Illinois

Scientific Investigations Report 2012–5212

U.S. Department of the Interior

U.S. Geological Survey
Cover. View of flooding in Old Shawneetown from the Ohio River taken from the Route 13 bridge on May 10, 2011. 

(Photograph by the U.S. Geological Survey.)
Ohio River Backwater Flood-Inundation 

Maps for the Saline and Wabash Rivers 

in Southern Illinois

By Elizabeth A. Murphy, Jennifer B. Sharpe, and David T. Soong

Scientific Investigations Report 2012–5212

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation maps for the Saline and 

Wabash Rivers in southern Illinois: U.S. Geological Survey Scientific Investigations Report 2012–5212, 20 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Study Area Description........................................................................................................................2

Previous Studies ...................................................................................................................................2

Constructing Water Surfaces ......................................................................................................................4

Hydrologic Data.....................................................................................................................................4

Topographic/Bathymetric Data ..........................................................................................................4

Development of Inundation Surfaces................................................................................................5

Inundation Mapping ......................................................................................................................................5

Inundation Verification.........................................................................................................................5

USGS Flood-Inundation Maps on the Internet...............................................................................10

Disclaimer for Flood-Inundation Maps ...........................................................................................10

Uncertainties and Limitations Associated with Inundation Maps .............................................10

Acknowledgments.......................................................................................................................................10

Summary........................................................................................................................................................10

References Cited..........................................................................................................................................11

Glossary.........................................................................................................................................................11

Figures

1. Map showing location of study area for the Saline and Wabash Rivers 

study, Illinois, and location of U.S. Geological Survey streamgages and 

National Weather Service forecast point.................................................................................3

2. Map showing the grouped Hydrologic Unit Code (HUC-12) basins with 

common water-surface elevations assigned for inundation-surface generation.............6

3. Maps showing generated water-surface elevations as compared to 

satellite imagery of flooding................................................................................................... 7–9

Tables

1. U.S. Geological Survey streamgage information for the Ohio River at

Old Shawneetown, Illinois-Kentucky, and the Middle Fork Saline River 

near Harrisburg, Illinois ...............................................................................................................4

2. Relative elevations of the Ohio River at Old Shawneetown USGS streamgage, 

Ohio-Saline confluence, and Ohio-Wabash confluence .......................................................5
iv

Map Sheets

Sheets 1–8. Flood-inundation maps for the Saline and Wabash Rivers, Illinois, corresponding 

to USGS streamgage Ohio River at Old Shawneetown, Illinois-Kentucky (station 

03381700) for gage height of:

1. 31 feet........................................................................................................................................13

2. 36 feet........................................................................................................................................14

3. 41 feet........................................................................................................................................15

4. 46 feet........................................................................................................................................16

5. 51 feet........................................................................................................................................17

6. 56 feet........................................................................................................................................18

7. 61 feet........................................................................................................................................19

8. 66 feet........................................................................................................................................20

(Map sheets are also available for downloading separately at http://pubs.usgs.gov/sir/2012/5212/.)

Conversion Factors

Multiply By To obtain

Length

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3

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

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Elevation, as used in this report, refers to distance above the vertical datum.
Ohio River Backwater Flood-Inundation Maps 

for the Saline and Wabash Rivers in Southern Illinois

By Elizabeth A. Murphy, Jennifer B. Sharpe, and David T. Soong

Abstract

Digital flood-inundation maps for the Saline and Wabash 

Rivers referenced to elevations on the Ohio River in southern 

Illinois were created by the U.S. Geological Survey (USGS). 

The inundation maps, accessible through the USGS Flood 

Inundation Mapping Science Web site at http://water.usgs.gov/

osw/flood_inundation/, depict estimates of the areal extent of 

flooding corresponding to selected water levels (gage heights) 

at the USGS streamgage at Ohio River at Old Shawneetown, 

Illinois-Kentucky (station number 03381700). Current gage 

height and flow conditions at this USGS streamgage may be 

obtained on the Internet at http://waterdata.usgs.gov/usa/nwis/

uv?03381700. In addition, this streamgage is incorporated into 

the Advanced Hydrologic Prediction Service (AHPS) flood 

warning system (http://water.weather.gov/ahps/) 

by the National Weather Service (NWS). The NWS forecasts 

flood hydrographs at many places that are often co-located at 

USGS streamgages. That NWS forecasted peak-stage information, also shown on the Ohio River at Old Shawneetown 

inundation Web site, may be used in conjunction with the 

maps developed in this study to show predicted areas of flood 

inundation.

In this study, eight water-surface elevations were mapped 

at 5-foot (ft) intervals referenced to the streamgage datum 

ranging from just above the NWS Action Stage (31 ft) to 

above the maximum historical gage height (66 ft). The elevations of the water surfaces were compared to a Digital Elevation Model (DEM) by using a Geographic Information System 

(GIS) in order to delineate the area flooded at each water level. 

These maps, along with information on the Internet 

regarding current gage heights from USGS streamgages and 

forecasted stream stages from the NWS, provide emergency 

management personnel and residents with information that is 

critical for flood response activities such as evacuations and 

road closures, as well as for post-flood recovery efforts.

Introduction 

Saline County, with an estimated 2010 population of 

24,913 (U.S. Census Bureau, 2012a), and Gallatin County, with 

an estimated 2010 population of 5,528 (U.S. Census Bureau, 

2012b), are in southern Illinois (fig 1). Parts of Saline and 

Gallatin Counties have experienced severe flooding numerous 

times, most notably in March 2008, May 2009, and March–

May 2011. Damage from the March 2008 flood was estimated 

at $16.8 million in Harrisburg (Federal Emergency Management Agency, 2011a). Saline and Gallatin Counties were 

designated counties in the Federal Emergency Management 

Agency (FEMA) disaster declarations in July 2009 (DR–1850) 

and June 2011 (DR–1991) (Federal Emergency Management 

Agency, 2009, 2011c). Spring 2011 brought record flooding to 

much of southern Illinois, including both the Mississippi and 

Ohio Rivers. Land use along flood plains in the study area is 

mostly agricultural, with scattered residential and commercial 

structures.

Prior to this study, county and municipal officials relied 

on several information sources to make decisions on how to 

best alert the public about impending flooding and to mitigate 

flood damages. One source is the FEMA Flood Insurance Study 

(FIS) for Saline County, Illinois, and Incorporated Areas, dated 

December 16, 2011 (Federal Emergency Management Agency, 

2011a), and for Gallatin County, Illinois, and Incorporated 

Areas, dated December 2, 2011 (Federal Emergency Management Agency, 2011b). A second source of information has been 

the U.S. Geological Survey (USGS) streamgages Ohio River 

at Old Shawneetown, Illinois-Kentucky (Ill.-Ky.) (station no. 

03381700) and Middle Fork Saline River near Harrisburg, Ill. 

(station no. 03382200), from which current or historical gage 

heights can be obtained. A third source has been the National 

Weather Service (NWS) forecast of peak stage (gage height) at 

the USGS Old Shawneetown streamgage through the Advanced 

Hydrologic Prediction Service (AHPS) site. Although USGS 
2 Ohio River Backwater Flood-Inundation Maps for the Saline and Wabash Rivers in Southern Illinois

current stage and NWS forecast stage information is useful 

for residents in the immediate vicinity of a streamgage, it is 

of limited use to residents farther upstream or downstream 

because the water-surface elevation is not constant along the 

entire stream channel. Also, FEMA and State emergency management mitigation teams or property owners typically lack 

information related to how deep the water is at locations other 

than near USGS streamgage or NWS flood-forecast points. 

Purpose and Scope

The purpose of this report is to (1) describe the development of a series of estimated flood-inundation maps for the 

Saline and Wabash Rivers based on gage heights on the Ohio 

River in southern Illinois, and (2) provide users with a library 

of flood-inundation maps that correspond to water levels 

referenced to the gage heights at the USGS streamgage on 

the Ohio River at Old Shawneetown, Ill.-Ky., ranging from 

31 ft to 66 ft. This report is a description of the maps and 

other flood information available on the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/

flood_inundation/.

Study Area Description

The study area is in southern Illinois (fig. 1) and includes 

parts of the Saline and Wabash River systems. The northern 

part of the study area is in the Mt. Vernon Hill Country of 

the Till Plains section of the Central Lowland physiographic 

province, and the southern part is in the Shawnee Hills section of the Interior Low Plateaus physiographic province 

(Illinois State Geological Survey, 2012). The drainage area is 

225 mi2 at the Middle Fork Saline River near Harrisburg, Ill. 

(03382200), streamgage (U.S. Geological Survey, 2012). The 

Middle Fork Saline River is a tributary of the Ohio River with 

the confluence at Ohio River mile 867.4, about 9.5 mi downstream from the Ohio River at Old Shawneetown streamgage. 

Flooding on the Saline River system is strongly influenced by 

flooding on the Ohio River because of the flat topography at 

the confluence and along the Saline River. This topography 

causes the majority of flooding on the Saline River to be from 

Ohio River water flowing up the Saline River rather than from 

local runoff. The Saline River also receives overland flow 

from the Wabash River when it floods (fig. 1). The Wabash 

River is another tributary of the Ohio River that joins the Ohio 

River upstream of the Saline River confluence at Ohio River 

mile 848.8. Contributions from the Ohio and Wabash Rivers 

and local runoff make flooding of the Saline River a hydraulically complex problem.

The Saline River headwaters originate in adjacent 

Franklin, Williamson, and Hamilton Counties, and the river 

flows generally east-southeast before entering the study area. 

The study reach is approximately 33 mi long, the top-of-bank 

channel width ranges from 60 to185 ft, and the average 

channel slope is 0.27 ft/mi. The land use along the study reach 

is a mix of agricultural, forested, and rural residential land. 

The main channel within the study reach has seven major road 

crossings. 

Previous Studies 

The current FISs for Saline County, Illinois, and Incorporated Areas, dated December 16, 2011(Federal Emergency 

Management Agency, 2011a), and Gallatin County, Illinois, 

and Incorporated Areas, dated December 2, 2011 (Federal 

Emergency Management Agency, 2011b), do not include any 

information on detailed hydrologic or hydraulic modeling of 

the Saline River. The Saline County FIS states that the Base 

Flood Elevation on the Middle Fork Saline River is controlled 

by backwater from the Saline River, which is in turn controlled by backwater flooding from the Ohio River. No profile 

or floodway for the Middle Fork Saline River is included in 

the Saline County FIS report. The flood-plain boundaries for 

the Saline River in the FIS report were delineated by using 

backwater from the Ohio River (Federal Emergency Management Agency, 2011a). The Gallatin County FIS states that 

the hydraulic behavior of the Wabash River is dominated 

by the Ohio River for 25 mi upstream of the confluence and 

that the Saline and North Fork Saline Rivers are controlled 

by backwater from the Ohio River. For the Saline River, the 

Saline County FIS states that the 1-percent annual exceedance probability flood water-surface elevation is 366.6 ft and 

the 0.2-percent annual exceedance probability flood watersurface elevation is 371.6 ft at the confluence with the Ohio 

River (Federal Emergency Management Agency, 2011a). For 

the Wabash River, the Gallatin County FIS states that the 

1-percent annual exceedance probability flood water-surface 

elevation is 368.5 ft and the 0.2-percent annual exceedance 

probability flood water-surface elevation is 373.2 ft at the confluence with the Ohio River (Federal Emergency Management 

Agency, 2011b). 

The historical record gage height at Ohio River at Old 

Shawneetown, Ill.-Ky., was reported to be 65.64 ft on January 

30, 1937, according to the National Weather Service (2012). 

The record gage height, corresponding to a water-surface 

elevation of 374.7 ft, was used to determine the upper bound 

of the mapping range.
Introduction 3

Figure 1. Map showing location of study area for the Saline and Wabash Rivers study, Illinois, and location of U.S. Geological Survey 

streamgages and National Weather Service forecast point.

Muddy

Carrier

Mills

Galatia

Raleigh

Eldorado

Omaha

Equality

Junction

Ridgway

New Haven

Shawneetown

Old Shawneetown

Harrisburg 03382200

03381700

(NWS 

forecast 

point)

1

142

13

145

34

45

88°30' 88°20' 88°10' 88°

37°50'

37°40'

13

34

56 Ohio

River

Wabash

Middle

Fork

Saline

River

River

ILLINOIS

Map

area

Map base from ArcGIS Map Service 

World_Shaded_Relief, accessed May 2012 at 

http://services.arcgisonline.com/arcgis/services

ILLINOIS

KENTUCKY

ILLINOIS

South

Fork

North

Fork

EXPLANATION

Saline and Wabash Rivers study

Physiographic division

USGS streamgage and number

INDIANA

Gallatin County

Hardin County

Saline County

Pope County

Saline County

Gallatin County

03382200

0 5 10 MILES

0 5 10 KILOMETERS

MT. VERNON HILL COUNTRY

in the TILL PLAINS 

section of the 

CENTRAL LOWLAND PROVINCE

MT. VERNON HILL COUNTRY

in the TILL PLAINS 

section of the 

CENTRAL LOWLAND PROVINCE

SHAWNEE HILLS

section of the

INTERIOR LOW

PLATEAU PROVINCES

SHAWNEE HILLS

section of the

INTERIOR LOW

PLATEAU PROVINCES
4 Ohio River Backwater Flood-Inundation Maps for the Saline and Wabash Rivers in Southern Illinois

Constructing Water Surfaces

 The water surfaces used to produce the eight floodinundation maps for this study were estimated by using 

water-surface elevations equivalent to the elevations along 

the Ohio River. This method was chosen because of a lack 

of hydrologic or hydraulic modeling for the study area and a 

history of backwater flooding from the Ohio River (Federal 

Emergency Management Agency, 2011a). Additionally, an 

analysis of the historical streamgage record on the Middle 

Fork Saline River near Harrisburg, Ill. (03382200), revealed 

that the Harrisburg streamgage would be in backwater from 

the Ohio River starting at a stage of 26 ft at the streamgage 

at Old Shawneetown (Marvin L. Harris, U.S. Geological 

Survey, written commun., January 18, 2012). The extent of the 

influence of the Ohio River on the Middle Fork Saline River 

water-surface elevations means that a reliable relation between 

stage and discharge cannot be established at the Harrisburg 

streamgage. Determining the discharge at the Middle Fork 

Saline River near Harrisburg streamgage is also complicated 

by a non-unique relation between stage and discharge (Marvin 

L. Harris, U.S. Geological Survey, written commun., January 

18, 2012). This non-uniqueness would make simulation of the 

Middle Fork Saline River with a one-dimensional, steady-state 

hydraulic model unrealistic. A one-dimensional, unsteadyflow model would also not capture the complexity of the flow 

because flow recirculation near the streamgage means that the 

flow direction must be described in two or three dimensions, 

not one (Marvin L. Harris, U.S. Geological Survey, written 

commun., January 18, 2012). A two-dimensional hydraulic 

model could be used for the system, but development of such 

a model would be prohibitively expensive. Considering these 

factors, generating water surfaces from Ohio River water-surface elevations was determined to give a reasonable estimate 

of the inundation surfaces.

Hydrologic Data

Hydrologic data in the study area were from the two 

previously mentioned streamgages (fig. 1; table 1). The Ohio 

River at Old Shawneetown, Ill.-Ky., streamgage was installed 

in January 2002 and has been recording discharge and water 

levels (gage height) continuously since installation. The 

Middle Fork Saline River near Harrisburg, Ill., streamgage 

was installed in August 2011 and has been recording water 

levels (gage heights) continuously since installation. This 

streamgage was also operated during October 1922–September 1932. The water-surface elevations from the Shawneetown 

streamgage are referenced to North American Vertical Datum 

of 1988 (NAVD 88). The water-surface elevations for the 

Middle Fork Saline River near Harrisburg streamgage are referenced to National Geodetic Vertical Datum of 1929 (NGVD 

29). The NGVD 29 elevations may be converted to NAVD 88 

elevations at this site by subtracting 0.325 ft. In addition to the 

continuous measurements, some discrete discharge measurements were made at these sites during periods of moderate to 

high flow. 

Topographic/Bathymetric Data

The 1/3-Arc Second National Elevation Dataset (NED) 

for the study area was downloaded from http://seamless.usgs.

gov/. NED has a horizontal resolution of approximately 10 m 

and a vertical accuracy of approximately 2.44 m (Gesch, 

2007) and was typically derived from cartographic contours 

and mapped hydrography. The NED does not contain detailed 

bathymetric data for the Middle Fork Saline River. Bathymetric and cross-sectional survey data were collected on the 

Middle Fork Saline River during September through November 2011. These survey data contain detailed channel elevation 

data below the water surface and were collected by using a 

Table 1. U.S. Geological Survey streamgage information for the Ohio River at Old Shawneetown, Illinois-Kentucky, and the Middle 

Fork Saline River near Harrisburg, Illinois.

[mi2, square miles; ft, feet; NAVD 88, North American Vertical Datum of 1988]

Station name Station number Drainage area 

(mi2

)

Latitude

(degrees, minutes, 

seconds)

Longitude

(degrees, minutes, 

seconds)

Period 

of record

Maximum 

recorded elevation 

at gage (ft above 

NAVD 88) and date

Ohio River at Old 

Shawneetown, 

Ill.-Ky

03381700 141,000 37o

 41′ 31′′ N. 88o 08′ 00′′ W. January 2002 to 

current year 

(2012)

365.47 ft

May 6, 2011

Middle Fork 

Saline River 

near Harrisburg, Ill.

03382200 225 37o

 44′ 18′′ N. 88o 30′ 05′′ W. August 10, 2011 

to current 

year (2012); 

October 1922 

to September 

1932

N/A; all data 

provisional at 

this time
Inundation Mapping 5

SonarMite echosounder (Ohmex Instrumentation, 2012) for 

the bathymetry and a total-station surveying instrument for 

elevations above the water surface. These survey data were to 

be included in a hydraulic model of the Middle Fork Saline 

River before the analysis of the streamgage record showed that 

backwater from the Ohio River dominates the streamgage near 

Harrisburg and creates non-unique stage-discharge relations, 

making steady-state, one-dimensional hydraulic modeling 

insufficient.

Development of Inundation Surfaces

Inundation maps were developed for a total of eight gage 

heights at 5-ft intervals. The gage heights ranged from 31 ft 

to 66 ft as referenced to the Ohio River at Old Shawneetown, 

Ill.-Ky., streamgage (03381700). The low end of this range 

of gage heights is just above the NWS Action Stage, and the 

high end is slightly above the maximum historical gage height 

value (National Weather Service, 2012). The method for creating the eight inundation surfaces was based on the Ohio River 

backwater controlling the Middle Fork Saline River watersurface elevations. To estimate the water-surface elevations to 

be mapped, the streamgage at Old Shawneetown (03381700) 

was used as the reference elevation. To estimate the change 

in the water-surface elevation away from the streamgage, the 

slope of the Ohio River water-surface elevation was determined from a HEC-2 model provided by the U.S. Army Corps 

of Engineers (Ken Lamkin, U.S. Army Corps of Engineers, 

Louisville District, written commun., 2011). From that model, 

elevations of the Ohio River at the confluence with the Wabash 

River (upstream of the streamgage) and at the confluence with 

the Saline River (downstream of the streamgage) could be 

related to the elevation at the streamgage (table 2). 

As shown in figure 2, the area to be mapped was then 

divided according to Hydrologic Unit Code (HUC-12) basin 

boundaries. The majority of the area (Beaver Creek-Saline 

River group) is inundated with the water-surface elevation 

at the Saline-Ohio River confluence, one area (Sibley CreekOhio River group) is inundated with the elevation at the 

streamgage, one area (Willow Pond Slough-Wabash River) 

is inundated with the elevation at the Wabash-Ohio River 

confluence, and one special-case area (Cypress Ditch) uses the 

Saline-Ohio River confluence elevation for the lower elevations and the Wabash-Ohio River confluence elevation for the 

higher elevations. The special-case area of Cypress Ditch is 

where the Wabash River partially flows into the Saline River 

instead of completely draining to the Ohio River.

Inundation Mapping

Flood-inundation maps were developed for eight watersurface elevations corresponding to the gage heights observed 

at the Ohio River at Old Shawneetown, Ill.-Ky., streamgage. 

The maps were created in ArcMap (Esri, Inc., 2012) by 

combining the water-surface elevations and Digital Elevation 

Model (DEM) data. Estimated flood-inundation boundaries 

for each water-surface elevation were created by using a DEM 

with a 10-m (approximately 30-ft) cell size. The inundation 

surface was then created by subtracting the ground-surface 

DEM from the water-elevation surface. The maps show 

estimated flood-inundated areas overlaid on high-resolution, 

georeferenced aerial photographs of the study area for each of 

the generated inundation surfaces for every 5 ft of change in 

gage height ranging from 31 to 66 ft.

Inundation Verification

The inundation surfaces produced with this method were 

compared to Landsat satellite imagery taken during selected 

flood events in spring 2011 (U.S. Geological Survey, 2011). 

Three different water-surface elevations at the Old Shawneetown streamgage (350.1 ft on April 17, 2011, 357.6 ft on 

March 16, 2011, and 364.7 ft on May 3, 2011) were compared 

to inundation surfaces produced for water-surface elevations 

of 350 ft, 355 ft, and 365 ft, respectively. The comparisons 

show that the generated inundation surfaces do a reasonable 

job in approximating the inundated area portrayed in the satellite images (fig. 3A–C). 

Table 2. Relative elevations of the Ohio River at 

Old Shawneetown USGS streamgage, Ohio-Saline confluence, 

and Ohio-Wabash confluence.

[WSE, water-surface elevation; ft, feet; NAVD 88, North American Vertical 

Datum of 1988]

WSE at 

Shawneetown 

(ft above NAVD 88)

Corresponding 

WSE at Ohio-Saline 

confluence

Corresponding WSE 

at Ohio-Wabash 

confluence

340 336.46 342.59

345 341.70 347.37

350 346.95 352.16

355 352.19 356.94

360 357.43 361.73

365 362.67 366.51

370 367.91 371.30

375 373.16 376.09
6 Ohio River Backwater Flood-Inundation Maps for the Saline and Wabash Rivers in Southern Illinois

Muddy

Carrier

Mills

Galatia

Raleigh

Eldorado

Omaha

Equality Junction

Ridgway

New Haven

Shawneetown

Old Shawneetown

Harrisburg 03382200

03381700

1

34

142

13

145

34

13

45

88°30' 88°20' 88°10' 88°

37°50'

37°40' Ohio

River

Wabash

Middle

Fork

Saline

River

River

ILLINOIS

Map

area

Map base from ArcGIS Map Service 

World_Shaded_Relief, accessed May 2012 at 

http://services.arcgisonline.com/arcgis/services

ILLINOIS

KENTUCKY

ILLINOIS

South

Fork

North

Fork

EXPLANATION

Grouped HUC12 basins

Beaver Creek-Saline River

Cypress Ditch

Sibley Creek-Ohio River

Willow Pond Slough-Wabash River

Saline and Wabash Rivers study

USGS streamgage and number

INDIANA

Gallatin County

Hardin County

Saline County

Pope County

Saline County

Gallatin County

03382200

0 1 2 3 4 5 6 7 8 9 MILES 10

0 1 2 3 4 5 6 7 8 9 KILOMETERS 10

56

Figure 2. Map showing the grouped Hydrologic Unit Code (HUC-12) basins with common water-surface elevations assigned 

for inundation-surface generation.
A

New Haven

Old Shawneetown

Harrisburg

03382200

03381700

1

34

142

13

145 34

13

45

88°30' 88°20' 88°10' 

37°50'37°40' Ohio

River

Middle

Fork Saline

River

Image base from Landsat 5 Thematic Mapper Imagery, Path 22, Row 34, April 17, 2011. Accessed September 2011 at http://glovis.usgs.gov/.

South Fork

North

Fork

EXPLANATION

Saline and Wabash Rivers study

Generated water-surface elevation of 350 feet above NAVD 88

USGS streamgage and number

03382200

Gallatin County

Hardin County

Saline County

Gallatin County

ILLINOIS KENTU

ILLINOI

IND

Figure 3A. Map showing generated water-surface elevations as compared to satellite imagery of flooding. Dark blue areas on the Thematic Mapper inundated areas. 350 feet compared to flooding on April 17, 2011, with a water-surface elevation of 350.1 feet at the streamgage. 
B
C

New Haven

Old Shawneetown

Harrisburg

03382200

03381700

1

34

142

13

145 34

13

45

88°30' 88°20' 88°10' 

37°50'37°40' Ohio

River

Middle

Fork Saline

River

Image base from Landsat 5 Thematic Mapper Imagery, Path 22, Row 34, May 3, 2011. Accessed September 2011 at http://glovis.usgs.gov/.

South Fork

North

Fork

EXPLANATION

Saline and Wabash Rivers study

Generated water-surface elevation of 365 feet above NAVD 88

USGS streamgage and number

03382200

Gallatin County

Hardin County

Saline County

Gallatin County

ILLINOIS KENT

ILLINO

IND

Figure 3C. Map showing generated water-surface elevations as compared to satellite imagery of flooding. Dark blue areas on the Thematic represent inundated areas. 355 feet as compared to flooding on March 16, 2011, with a water-surface elevation of 357.6 feet at the streamgag
10 Ohio River Backwater Flood-Inundation Maps for the Saline and Wabash Rivers in Southern Illinois

USGS Flood-Inundation Maps on the Internet

A USGS Flood Inundation Mapping Science World Wide 

Web portal has been established at URL http://water.usgs.gov/

osw/flood_inundation/ to provide estimated flood-inundation 

information to the public. The maps from this study showing the extent of inundated areas can be downloaded in three 

electronic file formats from that portal: (1) GIS shapefile format, (2) KMZ file format, and (3) Portable Document Format 

(PDF). Users can print out formatted maps (recommended 

size for printing is 11×17 in) or create customized maps using 

available GIS data layers. Each stream reach displayed on the 

Web site contains links to NWISWeb graphs of the current 

stage and streamflow at USGS streamgage Ohio River at Old 

Shawneetown, Ill.-Ky. (to which the inundation maps are 

referenced) and Middle Fork Saline River near Harrisburg, 

Ill. (which is at the upstream end of the study reach). A link 

also is provided to the NWS Advanced Hydrologic Prediction 

Service (AHPS) site (http://water.weather.gov/ahps/) so that 

the user can obtain applicable information on forecasted peak 

stage. The estimated flood-inundation maps are displayed in 

sufficient detail to note the extent of flooding with respect to 

individual structures so that preparations for flooding and decisions for emergency response can be performed efficiently, 

although the uncertainties and limitations described in this 

report must be considered. 

Disclaimer for Flood-Inundation Maps

Inundated areas shown should not be used for navigation, 

regulatory, permitting, or other legal purposes. The USGS 

provides these maps “as-is” for a quick reference, emergency 

planning tool but assumes no legal liability or responsibility 

resulting from the use of this information.

Uncertainties and Limitations Associated with 

Inundation Maps

Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty 

is associated with these maps. The flood boundaries shown 

were estimated on the basis of gage heights (water-surface 

elevations) at a selected USGS streamgage. Water-surface 

elevations along the stream reaches were estimated by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS streamgage. Unique meteorological factors 

(timing and distribution of precipitation) may cause actual 

water-surface elevations along the mapped reach to vary from 

those assumed during a flood, which may lead to deviations 

in the inundation boundaries shown. Additional areas may be 

flooded due to unanticipated conditions such as changes in the 

streambed elevation or roughness, or backwater from localized 

debris or ice jams. The accuracy of the floodwater extent portrayed on these maps will vary with the accuracy of the Digital 

Elevation Model used to simulate the land surface. 

If this series of flood-inundation maps will be used in 

conjunction with National Weather Service (NWS) river forecasts, the user should be aware of additional uncertainties that 

may be inherent or factored into NWS forecast procedures. 

The NWS uses forecast models to estimate the quantity and 

timing of water flowing through selected stream reaches in the 

United States. These forecast models (1) estimate the amount 

of runoff generated by precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds downstream, 

and (3) predict the flow and stage (water-surface elevation) for 

the stream at a given location (AHPS forecast point) throughout the forecast period (every 6 hours and 3 to 5 days out in 

many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_

forecasting.pdf.

 As mentioned previously, a USGS Flood Inundation 

Mapping Science World Wide Web portal has been established 

at URL http://water.usgs.gov/osw/flood_inundation/ to provide 

estimated flood-inundation information to the public. Although 

USGS intends to make this server available 24 hours a day, 

7 days a week, timely delivery of data and products from this 

server through the Internet is not guaranteed.

Acknowledgments

The authors wish to thank the many local, State, and 

Federal agencies that provided funding and cooperated in the 

operation and maintenance of the streamgages used for this 

study. Thanks are extended to Ken Lamkin and Richard Pruitt 

of the U.S. Army Corps of Engineers, Louisville District for 

providing the HEC-2 model of the Ohio River; Terry Ortel 

of the USGS Illinois Water Science Center (ILWSC) for 

Web-site support; and David Fazio and Charles Bohall of the 

USGS ILWSC for surveying work. Thanks are also extended 

to Robert R. Holmes, USGS Office of Surface Water, for his 

support of this project.

Summary

A series of estimated flood-inundation maps were developed for the Wabash and Saline Rivers in southern Illinois. 

These maps, available at URL (http://water.usgs.gov/osw/

flood_inundation/), in conjunction with the real-time gage 

height data from the USGS streamgage at the Ohio River at 

Old Shawneetown, Ill.-Ky.(station no. 03381700) and National 

Weather Service flood-stage forecasts, can help to guide the 

general public in taking individual safety precautions and can 

provide local government officials with a tool to efficiently 

manage emergency flood operations and flood mitigation 

efforts. 

The maps were developed by using ArcMap to delineate 

estimated flood-inundation areas for selected gage heights. 

The maps show estimated flood-inundation areas overlaid on 
Glossary 11

high-resolution, georeferenced aerial photographs of the study 

area for gage heights between 31 ft and 66 ft at the Ohio River 

at Old Shawneetown streamgage. 

References Cited

Esri, Inc., 2012, ArcGIS Desktop—Release 10.0: Redlands, 

Calif.

Federal Emergency Management Agency, 2009, Illinois 

Severe Storms and Flooding, Disaster Summary for FEMADR-1850, Illinois: Accessed April 17, 2012, at http://www.

fema.gov/news/eventcounties.fema?id=11668.

Federal Emergency Management Agency, 2011a, Flood Insurance Study, Saline County, Illinois and Incorporated Areas: 

Flood Insurance Study Number 17165CV000A [variously 

paginated].

Federal Emergency Management Agency, 2011b, Flood 

Insurance Study, Gallatin County, Illinois and Incorporated 

Areas: Flood Insurance Study Number 17059CV000A 

[variously paginated].

Federal Emergency Management Agency, 2011c, Illinois 

Severe Storms and Flooding, Disaster Summary for 

FEMA-DR-1991, Illinois: Accessed April 17, 2012, at 

http://www.fema.gov/news/eventcounties.fema?id=14672.

Gesch, D.B., 2007, The National Elevation Dataset, chap. 4 

of Maune, D., ed., Digital elevation model technologies and 

applications—The DEM users manual (2d ed.): Bethesda, 

Md., American Society for Photogrammetry and Remote 

Sensing, p. 99–118.

Illinois State Geological Survey, 2012, Physiographic divisions of Illinois: Accessed July 20, 2012, at http://www.isgs.

illinois.edu/maps-data-pub/publications/physio.shtml.

National Weather Service, 2012, Advanced Hydrologic 

Prediction Service, Ohio River at Shawneetown: 

Accessed April 17, 2012, at http://water.weather.gov/ahps2/

hydrograph.php?wfo=pah&gage=shni2.

Ohmex Instrumentation, 2012, SonarMite v3 Echo Sounder: 

Accessed July 18, 2012, at http://www.ohmex.com/

sonarmite.html.

U.S. Census Bureau, 2012a, Saline County QuickFacts: 

Accessed April 16, 2012, at http://quickfacts.census.gov/

qfd/states/17/17165.html.

U.S. Census Bureau, 2012b, Gallatin County QuickFacts: 

Accessed July 20, 2012, at http://quickfacts.census.gov/qfd/

states/17/17059.html.

U.S. Geological Survey, 2011, USGS Global Visualization 

Viewer: U.S. Geological Survey, Earth Resources Observation and Science Center, accessed September 19, 2011, at 

http://glovis.usgs.gov/.

U.S. Geological Survey, 2012, National Water Information System–Web Interface, USGS 03381700 Ohio 

River at Old Shawneetown, Ill.-Ky.: Accessed April 

16, 2012, at http://waterdata.usgs.gov/il/nwis/uv/?site_

no=03381700&PARAmeter_cd=00065,00060.

Glossary

DEM A Digital Elevation Model (DEM) is a digital file consisting of terrain elevations for ground positions at regularly 

spaced horizontal intervals.

Gage height Gage height is the term used by the USGS 

National Water Information System display to describe the 

height of water above the datum at a streamgage. It is synonymous with stage.

HUC A hydrologic unit code (HUC) is an identifier for a 

drainage basin. 

Inundation surface The mathematical difference between the 

water-elevation surface and ground-elevation surface results in 

the inundation surface representing the area covered by water.

Rating curve A rating curve is the relation between stage and 

discharge at a cross-section in a river. 

Stage Stage is the term used by the National Weather 

Service to describe the height of water above the datum at a 

streamgage. It is synonymous with gage height. 

Water-surface elevation Water-surface elevation at a 

streamgage is determined by adding the gage height of the 

water to the datum for the streamgage. 

13

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 1. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 31 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
14 

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 2. Flood inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 36 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
15

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 3. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 41 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
16

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 4. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 46 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
17

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 5. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 51 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
18

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 6. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 56 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
19

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 7. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 61 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY
20

56

New Haven

Ridgway

Omaha

Galatia

Raleigh

Eldorado

Equality Junction

Shawneetown

Old Shawneetown

Muddy

Harrisburg

34

13 13

145

13

34

1

142

1

45

88°35' 88°30' 88°25' 88°20' 88°15' 88°10' 88°5' 88°

37°50'

37°45'

37°40'

37°35'

Eldorado

Raleigh

Galatia

Omaha

Ridgway

Junction

Shawneetown

Old Shawneetown

Equality

Muddy

Harrisburg

KENTUCKY

ILLINOIS

INDIANA

ILLINOIS

South

03382200

03381700

Fork

Fork

Middle

North

Fork

Saline

River

River

Ohio

River

Wabash

INDIANA

ILLINOIS

Map

area

Orthography from the USDA Farm Service Agency, Aerial Photography Field Office 2012 National Agriculture Imagery Program (NAIP) Natural Color Imagery for Illinois and Kentucky, accessed in 2012 at http://gis.apfo.usda.gov/arcgis/services.

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Scientific Investigations Report 2012–5212

Murphy, E.A., Sharpe, J.B., Soong, D.T., 2012

DISCLAIMER

lnundated areas shown should not be used for navigation, regulatory, permitting, or 

other legal purposes. The USGS provides these maps “as-is” for a quick reference, 

emergency planning tool but assumes no legal liability or responsibility resulting from 

the use of this information.

UNCERTAINTIES AND LIMITATIONS FOR USE OF FLOOD-INUNDATION MAPS

Although the flood-inundation maps represent the boundaries of inundated areas with a 

distinct line, some uncertainty is associated with these maps. The flood boundaries 

shown were estimated based on gage heights (water-surface elevations) at a selected 

USGS streamgage. Water-surface elevations along the stream reaches were estimated 

by assuming unobstructed flow and using hydrologic conditions anticipated at the USGS 

streamgage. Unique meteorological factors (timing and distribution of precipitation) may 

cause actual water-surface elevations along the mapped reach to vary from those 

assumed during a flood, which may lead to deviations in the water-surface elevations 

and inundation boundaries shown. Additional areas may be flooded due to unanticipated 

conditions such as changes in the streambed elevation or roughness or backwater from 

localized debris or ice jams. The accuracy of the floodwater extent portrayed on these 

maps will vary with the accuracy of the Digital Elevation Model used to simulate the 

land surface. Additional uncertainties and limitations pertinent to this study are 

described in the document accompanying this set of flood-inundation map sheets.

If this series of flood-inundation maps will be used with National Weather Service 

(NWS) river forecasts, the user should be aware of additional uncertainties that may be 

inherent or factored into NWS forecast procedures. The NWS uses forecast models to 

estimate the quantity and timing of water flowing through selected stream reaches in 

the United States. These forecast models (1) estimate the amount of runoff generated by 

precipitation and snowmelt, (2) simulate the movement of floodwater as it proceeds 

downstream, and (3) predict the flow and stage (water-surface elevation) for the stream 

at a given location (AHPS forecast point) throughout the forecast period (every 6 hours 

and 3 to five days out in many locations). For more information on AHPS forecasts, 

please see: http://water.weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Suggested citation:

Murphy, E.A., Sharpe, J.B., and Soong, D.T., 2012, Ohio River backwater flood-inundation 

maps for the Saline and Wabash Rivers in southern Illinois: U.S. Geological Survey 

Scientific Investigations Report 2012–5212, 20 p.

EXPLANATION

Limits of the study area

Flood-inundation area

USGS streamgage and number 03382200

0 5 MILES

0 5 KILOMETERS

13 Illinois or Kentucky State route marker

U.S. route marker 45

Sheet 8. Flood-inundation map of the Saline and Wabash Rivers, Illinois, corresponding to a gage height of 66 feet at U.S. Geological Survey streamgage number 03381700, Ohio River at Old Shawneetown, Illinois-Kentucky. 

GALLATIN COUNTY

HARDIN COUNTY

SALINE COUNTY

POPE COUNTY

SALINE COUNTY

GALLATIN COUNTY

Murphy, Sharpe, and Soong —Ohio River Backwater Flood-Inundation Maps for the Saline and Wabash Rivers in Southern Illinois—Scientific Investigations Report 2012–5212