U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5219

Prepared in cooperation with the Indiana Department of Transportation

Flood-Inundation Maps for the White River near 

Edwardsport, Indiana
Cover photos: Views from State Road 358 bridge over White River near Edwardsport, IN, taken on January 18, 2013 by Paul Baker of the 

U.S. Geological Survey.
Flood-Inundation Maps for the White River 

near Edwardsport, Indiana 

By Kathleen K. Fowler 

 

Prepared in cooperation with the Indiana Department of Transportation

Scientific Investigations Report 2014–5219

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Fowler, K.K., 2014, Flood-inundation maps for the White River near Edwardsport, Indiana: U.S. Geological Survey 

Scientific Investigations Report 2014–5219, 11 p., http://dx.doi.org/10.3133/sir20145219.

ISSN 2328-0328 (online)
iii

Contents

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

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

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

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

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

Creation of Flood-Inundation Map Library ................................................................................................4

Computation of Water-Surface Profiles............................................................................................5

Hydrologic Data............................................................................................................................5

Topographic and Bathymetric Data..........................................................................................6

Hydraulic Structures ...................................................................................................................6

Energy-Loss Factors....................................................................................................................6

Hydraulic Model...........................................................................................................................7

Development of Water-Surface Profiles..................................................................................8

Development of Flood-Inundation Maps ..........................................................................................8

Flood-Inundation Map Delivery.................................................................................................8

Disclaimer for Flood-Inundation Maps ....................................................................................8

Uncertainties and Limitations Regarding Use of Flood-Inundation Maps .......................10

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

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

Figures

1. Map showing location of study reach for the White River near Edwardsport, 

Indiana; location of U.S. Geological Survey streamgage; and location of 

National Weather Service forecast sites .................................................................................3

2. Flood-inundation map for the White River near Edwardsport, Indiana, 

corresponding to a stage of 29.9 feet at the U.S. Geological Survey 

streamgage ...................................................................................................................................9

Tables

1. U.S. Geological Survey streamgage information for White River near 

Edwardsport, Indiana...................................................................................................................4

2. Coordinated discharges for selected annual exceedance probabilities for 

White River near Edwardsport, Indiana....................................................................................4

3. Estimated discharges for corresponding stages and water-surface elevations at 

U.S. Geological Survey streamgage 03360730 used in the hydraulic model of the 

White River near Edwardsport, Indiana....................................................................................5

4. Calibration of hydraulic model to target water-surface elevations at U.S. Geological 

Survey streamgage on White River near Edwardsport, Indiana..........................................7

5. Calibration of hydraulic model to water-surface elevations at selected locations 

along the White River for the flood of April 24, 2013...............................................................7
iv

Acknowledgments

The authors wish to thank the many local, State, and Federal agencies that have cooperated in 

the funding for the operation and maintenance of the gage used for this study, especially the 

National Streamflow Information Program. Special thanks are given to Indiana Department of 

Transportation for their cooperation in this study and to the National Weather Service for their 

continued support to the U.S. Geological Survey flood-inundation mapping initiative. 

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

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 either (1) stage, the height above an arbitrary 

datum established at a streamgage; or (2) elevation, the height above North American 

Vertical Datum of 1988 (NAVD 88). 

Horizontal coordinate information is referenced to the North American Datum of 1927 

(NAD 27).

Conversion Factors

Inch/Pound to SI
Flood-Inundation Maps for the White River near 

Edwardsport, Indiana

By Kathleen K. Fowler 

Abstract

Digital flood-inundation maps for a 3.3-mile reach of 

the White River near Edwardsport, (Ind.), were created by 

the U.S. Geological Survey (USGS) in cooperation with the 

Indiana Department of Transportation. The inundation maps, 

which can be accessed through the USGS Flood Inundation 

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

inundation/, depict estimates of the areal extent and depth of 

flooding corresponding to selected water levels (stages) at 

USGS streamgage 03360730, White River near Edwardsport, 

Ind. Near-real-time stages at this streamgage may be obtained 

from the USGS National Water Information System at http://

waterdata.usgs.gov/ or the National Weather Service Advanced 

Hydrologic Prediction Service at http:/water.weather.gov/

ahps/, which also forecasts flood hydrographs at this site (site 

EDWI3).

Flood profiles were computed for the White River near 

Edwardsport reach by means of a one-dimensional step-backwater model developed by the U.S. Army Corps of Engineers. 

The hydraulic model was calibrated by using the most current 

stage-discharge relations at USGS streamgage 03360730, 

White River near Edwardsport, Ind., and high-water marks 

from the flood of April 2013. The calibrated hydraulic model 

was then used to determine 19 water-surface profiles for flood 

stages at approximately 1-foot intervals referenced to the 

streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The 

simulated water-surface profiles were then combined with 

a geographic information system digital elevation model to 

delineate the area flooded at each water level.

The availability of these maps, along with Internet information regarding current stage from the USGS streamgage 

03360730 White River near Edwardsport, Ind., and forecasted 

stream stages from the National Weather Service, provides 

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 

The city of Edwardsport, (Ind.), is a community in Knox 

County, with an estimated population of 303 (U.S. Census 

Bureau, 2010). Edwardsport and the surrounding area have 

experienced flooding numerous times, most recently in 2002, 

2005, 2008, and 2013. The majority of flood damages in 

the Edwardsport area have occurred along the White River, 

which flows on the east side of the town (Federal Emergency 

Management Agency, 1984). During flood events, some 

evacuations are necessary in low areas in the northeast part 

of the city and some local roads are impassable. Another 

potential problem from flooding is the halting of rail traffic 

to the power-generating plant on the south side of town and 

flooding in parts of the plant property. In addition, agricultural 

lands surrounding the city have potential for flooding as the 

levees are topped. Flood plains along the river are moderately 

developed and contain a mix of residential, commercial, and 

agricultural areas.

Before this study, emergency responders in Edwardsport relied on several information sources to make decisions 

on how to best alert the public and mitigate flood damages. 

One source is the Federal Emergency Management Agency 

(FEMA) flood insurance study (FIS) for Knox County 

(Federal Emergency Management Agency, 1984). Another 

source of information is U.S. Geological Survey_(USGS)

streamgage 03360730, White River near Edwardsport, Ind., 

from which current (U.S. Geological Survey, 2014a) and 

historical (U.S. Geological Survey, 2014b) water levels (stage) 

can be obtained (http://nwis.waterdata.usgs.gov/in/nwis/

nwisman/?site_no=03360730&agency_cd=USGS). A third 

source is the National Weather Service’s (NWS) forecast of 

peak stage at USGS streamgage 03360730, White River near 

Edwardsport, Ind., through their Advanced Hydrologic Prediction Service (AHPS) Web site http:/water.weather.gov/ahps/

(National Weather Service, 2014a). 
2 Flood-Inundation Maps for the White River near Edwardsport, Indiana

Although the current stage at a USGS streamgage is 

particularly 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 reach. Knowledge of a water 

level at a streamgage is difficult to translate into depth and 

areal extent of flooding at points distant from the streamgage. 

One way to address these informational gaps is to produce 

a library of flood-inundation maps that are referenced to the 

stages recorded at the USGS streamgage. By referring to the 

appropriate map, emergency responders can discern the severity of flooding (depth of water and areal extent); identify roads 

that are, or will soon be, flooded; and make plans for notification or evacuation of residents in harm’s way for some distance upstream and downstream from the streamgage. In addition, the capability to visualize the potential extent of flooding 

has been shown to motivate residents to take precautions and 

heed warnings that they previously might have disregarded. In 

2013–14, the USGS, in cooperation with the Indiana Department of Transportation, lead a project to produce a library of 

flood-inundation maps for the White River near Edwardsport, 

Ind. 

Purpose and Scope

This report describes the development of a series of 

estimated flood-inundation maps for the White River near 

Edwardsport, Ind., and identifies where on the Internet the 

maps can be accessed and ancillary data (geographic information system [GIS] flood polygons and depth grids) can be 

downloaded. Internet users can select estimated inundation 

maps that correspond to (1) flood stages at USGS streamgage 

03360730 and (2) the NWS forecasted peak stage at the NWS 

sites FREI3 and EDWI3.The scope of the study was limited to 

the White River reach extending 2.4 miles (mi) upstream from 

USGS streamgage 03360730 at the State Road 358 Bridge and 

0.94 mi downstream from streamgage 03360730 (fig. 1). 

The flood-inundation maps were produced for flood levels referenced to the stage recorded at the USGS streamgage 

03360730 on the White River near Edwardsport, Ind. (table 1); 

the streamgage is on the downstream side of the State Road 

358 bridge. The maps cover a range in stage from 12 to 

29.9 feet (ft). The 12-ft stage is approximately bankfull and 

is defined by the National Weather Service (2014b) as the 

“action stage” or that stage which, when reached by a rising 

stream, requires the NWS or a partner to take some type of 

mitigation action in preparation for possible significant hydrologic activity. The 29.9-ft stage is the highest stage on the 

current (2014) stage-discharge rating curve. The stage of the 

flood of April 24, 2013, near Edwardsport, was 25.4 ft (U.S. 

Geological Survey, 2014c). The major flood stage, as determined by the NWS, is 25 ft.

Study Area Description

The White River near the city of Edwardsport is in southwest Indiana in the Wabash Lowland physiographic section 

of the Southern Hills and Lowlands Region (Gray, 2000). The 

drainage area is 4,988 square miles (mi2) at the upstream end 

of the study reach; 5,015 mi2 at USGS streamgage 03360730 

(White River near Edwardsport); and 5,016 mi2 at the downstream extent of the study reach (U.S. Geological Survey, 

2014a, 2014d). The headwaters originate in Randolph County 

(not shown) and the stream flows generally southwestward 

entering the town of Edwardsport. There are no significant 

tributaries to the White River as it flows through the study 

reach. Generally, the area has extensive flood plains with 

broad terraces and is underlain by outwash sand. The study 

reach is approximately 3.3 mi long and has an average topof-bank channel width of about 350 ft and an average channel 

slope of 0.0002 (1.2 feet per mile [ft/mi]). Most of the land 

contiguous to the study reach is either agricultural or natural 

areas with much smaller portions having residential development. An earthen levee (shown as “levee” on fig. 1) runs 

along the eastern bank of the study area. The levee protects the 

agricultural area from flooding until it is overtopped during 

the highest flows (at stage 27 ft and above). There is also an 

earthen embankment that runs along the western bank from 

State Road 358 southward and past the study extent. The overall effectiveness of this embankment is unknown; therefore, it 

was not simulated as a levee in the hydraulic model that was 

developed for this study.

The population of Edwardsport has declined in recent 

years from 363 in 2000 to 303 in 2010 (U.S. Census Bureau, 

2010). The main channel within the study reach has one major 

road crossing, State Road 358, crossing the main channel 

and adjacent flood plain. A railroad spur enters the town from 

the north and runs along the west side of the river. This spur 

serves the power generating facility on the south side on 

Edwardsport. This railroad, a small part of the power generating facility, and local roads close to the river are vulnerable to 

flooding during the highest flows.

Previous Studies

The most recent FIS for Knox County (Federal Emergency Management Agency, 1984) is a study that investigated 

the existence and severity of flood hazards in the unincorporated areas of Knox County. The FIS presents estimates of 

the peak discharges with 10-, 2-, 1-, and 0.2-percent annual 

exceedance probabilities and their associated water-surface 

elevations for the White River at Petersburg (03373980) 

(river mile 45.7) (http://nwis.waterdata.usgs.gov/in/nwis/

uv/?site_no=03373980).
Introduction 3

67

67

358

358

Edwardsport

03360730

N Ott Rd

N 300 W

Power-generating

plant

EDWI3

FREI3

EXPLANATION

67

U.S. Geological Survey

streamgage and number

Limit of study area

State Road marker

Flow arrow—Indicates direction

of water flow

03360730

Levee

EDWI3 National Weather Service

Advanced Hydrologic Predictive

Service site

87°15' 87°13'30"

38°49'30"

38°48'

INDIANA

Study area

Figure 1. 

Projection: Indiana State Plane Eastern Zone

Horizontal coordinate information is referenced to the North American Datum of 1983

Orthophotography from Esri ArcGIS World Imagery, 

2011, available at http://goto.arcgisonline.com/maps/World_Imagery

Location of study reach for the White River near Edwardsport, Indiana, location of U.S. Geological Survey streamgage, and location of 

National Weather Service forecast sites (FREI3 and EDWI3).

White

River

Hammelman Rd

N Freelandville Rd

Albert St Water St

Shipping St

Railroad

0 0.5 1 MILE

0 0.5 1 KILOMETER

Figure 1. Location of study reach for the White River near Edwardsport, Indiana; location of U.S. Geological Survey 

streamgage; and location of National Weather Service forecast sites (FREI3 and EDWI3).
4 Flood-Inundation Maps for the White River near Edwardsport, Indiana

Table 1. U.S. Geological Survey streamgage information for White River near Edwardsport, Indiana (station number 03360730). 

[mi2, square miles; NAD 27, North American Datum of 1927; °, degree; ′, minutes; ′′, seconds; NAVD 88, North American Vertical Datum of 1988; ft, feet; ft3/s, 

cubic feet per second]

Streamgage 

name

Streamgage 

number

Drainage 

area 

(mi2

)

Latitude 

(NAD 27)

Longitude 

(NAD 27)

Period 

of record

Datum 

of gage 

(NAVD 88)

Maximum 

recorded flood 

elevation 

(NAVD 88) 

and date

Maximum 

discharge, 

in ft3

/s, 

and date

White River near 

Edwardsport, 

Indiana

03360730 5,015 38°47′42.2′′ 87°14′30.7′′ August 2012 

to present

431.56 ft 456.96 ft on 

April 24, 2013 

(corresponds 

to a gage 

height of 

25.40 ft)

61,400 on 

April 24, 

2013.

 The USGS streamgage near Edwardsport is at river mile 

81 and does not compare well to the discharges at the Petersburg streamgage; however, the FIS does include information 

about the principal flood problems in Knox County. 

The Indiana Department of Natural Resources (IDNR) 

has produced Digital Flood Insurance Rate Maps (DFIRM) 

that include the study area in both Knox and Daviess Counties 

(Indiana Department of Natural Resources, 2004a and 2004b). 

These maps outline the special flood hazard areas around 

Edwardsport. In addition, IDNR, the USGS, the Natural 

Resource Conservation Service, and the U.S. Army Corps of 

Engineers have agreed to the discharge-frequency values for 

sites along many rivers in Indiana, the values are termed coordinated discharges and assure consistency among the State and 

Federal agencies that undertake streamflow studies (Indiana 

Department of Natural Resources, 2014). The coordinated 

discharges for the White River near Edwardsport are listed in 

table 2. 

Creation of Flood-Inundation Map 

Library

The USGS has standardized the procedures for creating 

flood-inundation maps for flood-prone communities so that the 

process followed and products produced are similar regardless of which USGS office is responsible for the work (U.S. 

Geological Survey, 2014e). Tasks specific to development of 

the flood maps for Edwardsport, Ind., were (1) installation of 

the streamgage on the White River near Edwardsport in 2012 

(table 1), (2) collection of topographic and bathymetric data 

for selected cross sections and geometric data for structures 

and bridges along the study reach, (3) estimation of energyloss factors (roughness coefficients) in the stream channel and 

flood plain and determination of steady-flow data, (4) collection of high-water marks for the flood of 2013, (5) computation of water-surface profiles using the U.S. Army Corps of 

Engineers’ HEC–RAS computer program (U.S. Army Corps 

of Engineers, 2010), (6) production of estimated flood-inundation maps at various stream stages using the U.S. Army Corps 

of Engineers’ HEC–GeoRAS computer program (U.S. Army 

Corps of Engineers, 2009) and a GIS, and (7) preparation 

of the maps, both as shapefile polygons that depict the areal 

extent of flood inundation and as depth grids that provide the 

depth of floodwaters, for display on a USGS flood-inundation 

mapping application.

Table 2. Coordinated discharges for selected annual 

exceedance probabilities for White River near Edwardsport, 

Indiana. 

[mi2, square miles; ft3/s, cubic feet per second; USGS, U.S. Geological 

Survey]

Location on 

White River

Drainage 

area 

(mi2

)

Coordinated discharges (ft3

/s) for 

indicated annual exceedance 

probabilities (in percent)1

10 2 1

At USGS 

streamgage 

number 03360730

5,015 67,500 95,100 109,000 

1

 Data from USGS StreamStats (2014).
Creation of Flood-Inundation Map Library 5

Computation of Water-Surface Profiles

The water-surface profiles used to produce the 19 

flood-inundation maps in this study were simulated by using 

HEC–RAS, version 4.1.0 (U.S. Army Corps of Engineers, 

2010). HEC–RAS is a one-dimensional step-backwater model 

for simulation of water-surface profiles with gradually varied, 

steady-state or unsteady-state flow computation options. The 

HEC–RAS analysis for this study was done using the steadystate flow computation option.

Hydrologic Data

The study area hydrologic network consists of one 

streamgage 03360730 (fig. 1; table 1), which has been in operation since August 2012. This streamgage has a continuous 

record of measured water level (stage) and computed streamflow since 2012. Stage is measured every 15 minutes, transmitted hourly by a satellite radio in the streamgage, and made 

available on the Internet through the USGS National Water 

Information System (NWIS; U.S. Geological Survey, 2014b). 

Stage data from this streamgage are referenced to a local 

datum but can be converted to water-surface elevations referenced to the North American Vertical Datum of 1988 (NAVD 

88) by adding 431.56 ft. Continuous records of streamflow 

are computed from a stage-discharge relation, which has been 

developed for the streamgage, and are available through the 

USGS NWIS Web site (http://waterdata.usgs.gov/nwis). 

The steady-flow data necessary for the hydraulic model 

consisted of boundary conditions (normal depth) and peakdischarge information. The peak flows used in the model 

simulations (table 3) were taken from the current stage-discharge relation (USGS rating no. 3, effective May 30, 2014) 

and corresponded with the target stages. The steady-flow 

data for the model were obtained from field measurements of 

streamflow at USGS streamgage 03360730, White River near 

Edwardsport, Ind. All computations used discharge values 

with known stages from actual streamflow measurements or 

the stage-discharge relations at the gage. No major tributaries 

join the White River within the 3.3-mi study reach; therefore, 

the gage-derived discharges were not adjusted for tributary 

inflows but were held constant throughout the study reach for 

a given profile (table 3).

Table 3. Estimated discharges for corresponding stages and water-surface elevations at U.S. Geological Survey streamgage 03360730 

used in the hydraulic model of the White River near Edwardsport, Indiana. 

[mi2, square miles; ft3/s, cubic feet per second; NAVD 88, North American Vertical Datum of 1988]

Stage, in feet above gage datum at White River (reference datum 431.56 NAVD 88)

Location

Drainage 

area 

(mi2

)

12.0 

(443.56)

13.0 

(444.56)

14.0 

(445.56)

15.0 

(446.56)

16.0 

(447.56)

17.0 

(448.56)

18.0 

(449.56)

19.0 

(450.56)

20.0 

(451.56)

 21.0 

(452.56)

22.0 

(453.56)

Streamgage 

number 

03360730

5,015

Discharge (ft3

/s)

9,820 11,300 12,800 14,400 16,100 17,800 19,800 23,200 27,600 32,600 38,100

Stage, in feet above gage datum at White River (reference datum 431.56 NAVD 88)

23.0 

(454.56)

24.0 

(455.56)

25.0 

(456.56)

26.0 

(457.56)

27.0 

(458.56)

28.0 

(459.56)

29.0 

(460.56)

29.9 

(461.46)

Discharge (ft3

/s)

44,200 50,900 58,300 66,300 75,500 87,100 99,900 113,000
6 Flood-Inundation Maps for the White River near Edwardsport, Indiana

Topographic and Bathymetric Data

All topographic data used in this study are referenced 

vertically to NAVD 88 and horizontally to the North American Datum of 1983 (NAD 83). Cross-section elevation data 

were obtained from a digital elevation model (DEM) that 

was derived from light detection and ranging (lidar) data that 

were collected as part of a statewide project during 2011–13 

by Woolpert, Inc., Geospatial Services, Dayton, Ohio (Woolpert, Inc., 2011). The lidar data for Knox and Daviess Counties were collected in 2013. The DEM was obtained from the 

Indiana Spatial Data Portal (Indiana University, 2013). The 

original lidar data have horizontal resolution of 4.9 ft and 

vertical accuracy of 0.98 ft at a 95-percent confidence level 

based on a root mean squared error of 0.49 ft for the “open 

terrain” land-cover category. By these criteria, the lidar data 

support production of 2-ft contours (Dewberry, 2012); the final 

DEM, which was resampled to a grid-cell size of 10 ft by 10 

ft to decrease the GIS processing time, has a vertical accuracy of plus or minus 1 ft. By using HEC–GeoRAS (a set of 

procedures, tools, and utilities for processing geospatial data 

in ArcGIS) elevation data were extracted from the DEM for 33 

cross sections, including one bridge, and a levee to protect the 

agricultural area on the east side of the study area from flooding. These data subsequently were input to the HEC–RAS 

model. 

Because lidar data cannot provide ground elevations 

below a stream’s water surface, channel cross sections were 

surveyed by USGS field crews during 2013. Cross-sectional 

depths were measured by using hydroacoustic instrumentation at 18 locations. A differential global positioning system 

(DGPS) with real-time kinematic (RTK) technology was used 

to derive horizontal locations and the elevation of the water 

surface at each surveyed cross section. 

In the ArcMap application of ArcGIS (Esri, 2014), these 

field data were used in conjunction with a bathymetry mesh 

tool, created by Merwade and others (2008), to interpolate 

below-water ground elevations through the study reach. The 

density of ground elevations in the mesh was determined by 

two variables: (1) the number of parallel longitudinal profiles 

that were evenly spaced across the channel and ran the length 

of the study reach, and (2) the user-specified spacing between 

cross sections. Ground elevations were either extracted or 

interpolated from the field data at the intersections of the longitudinal profiles and cross sections that were spaced approximately 500 ft apart. The mesh elevations were subsequently 

added to the DEM data of the synthetic cross sections before 

the data were exported to HEC–RAS. Instructions for the 

bathymetry mesh tool are presented by Merwade (2011). 

Hydraulic Structures

There is one road (State Road 358) crossing that has the 

potential to affect water-surface elevations during floods along 

the stream. Bridge-geometry data were obtained from field 

surveys conducted by USGS personnel (C.D. Menke, unpub. 

data, 2013). A levee exists along the east side of the study area 

and provides protection from flooding in the adjacent croplands. An earthen embankment runs along the west bank of the 

White River downstream from the bridge and continues past 

the study extent. Because of the uncertainty as to the effectiveness of this embankment, it was not simulated as a levee; 

rather, where appropriate to do so, the landward side of the 

levee was simulated as ineffective flow area up to the elevation of the top of the embankment. 

Energy-Loss Factors

Hydraulic analyses require the estimation of energy 

losses that result from frictional resistance exerted by a channel on flow. These energy losses are quantified by the Manning’s roughness coefficient (n-value) (Arcement and Schneider, 1989). Initial (pre-calibration) n-values were selected 

on the basis of field observations and high-resolution aerial 

photographs. An n-value of 0.040 was selected for the main 

channel and 0.100 for the overbank areas, which are dominated by forests and agricultural fields in the rural sections of 

the study reach and a small residential and commercial areas 

within the city of Edwardsport. 

The initial n-values were adjusted as part of the calibration process, which involved stepwise matching of simulated and observed water-surface elevations, starting at the 

downstream end of the study reach and moving upstream. 

Roughness-coefficient adjustment factors were varied by 

flow and adjusted until the simulated water-surface elevations approximated the observed water-surface elevations in 

the downstream half of the study reach (upstream from the 

bridge on State Road 358). The actual n-values were computed 

by multiplying the initial n-value by each of the roughnesscoefficient adjustment factors. Main channel n-values ranged 

from 0.040 to 0.049, and overbank values ranged from 0.088 

to 0.11. Upstream from the bridge to the upstream end of the 

study reach, n-values were no longer varied by discharge. 

Again, these values were used, and transitions were made, 

to minimize the differences between simulated and observed 

high-water marks.
Creation of Flood-Inundation Map Library 7

Hydraulic Model

The HEC–RAS analysis for this study was done by using 

the steady-state flow computation option. Steady-state flow 

data consisted of flow regime, boundary conditions, and peak 

flows that produced water-surface elevations at the streamgage 

cross section that matched target water-surface elevations. 

These target elevations coincided with even 1-ft increments 

of stage, referenced to the local streamgage datum. Subcritical (tranquil) flow regime was assumed for the simulations. 

Normal depth based on an estimated average channel slope 

of 0.0002 from data obtained from a USGS field crew in 

2013 (C.D. Menke, unpub. data) was used as the downstream 

boundary condition of the reach. The peak flows that were 

used in the model were discussed in the “Hydrologic Data” 

section.

The hydraulic model was calibrated to the most current 

stage-discharge relation (USGS rating no. 3, May 30, 2014) at 

USGS streamgage 03360730, White River near Edwardsport, 

Ind., and high-water marks from the flood of April 24, 2013. 

Model calibration was accomplished by adjusting Manning’s 

n-values until the results of the hydraulic computations closely 

agreed with the observed water-surface elevations for given 

flows. Differences between target and modeled water-surface 

elevations for the 19 simulated flows at the USGS streamgage 

03360730 were equal to or less than 0.20 ft (table 4). Differences between surveyed and modeled elevations of high-water 

marks in the study reach for the flood of April 24, 2013, were 

equal to or less than 0.18 ft (table 5). The results demonstrate 

that the model is capable of simulating accurate water levels 

over a wide range of flows in the basin. 

Table 4. Calibration of hydraulic model to target water-surface 

elevations at U.S. Geological Survey streamgage on White River 

near Edwardsport, Indiana (station number 03360730)

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

Stage of 

water-surface 

profile 

(ft)

Target 

water-surface 

elevation 

(ft, NAVD 88)

Modeled 

water-surface 

elevation 

(ft, NAVD 88)

Elevation 

difference 

(ft)

12.00 443.56 443.67 0.11

13.00 444.56 444.71 0.15

14.00 445.56 445.69 0.13

15.00 446.56 446.69 0.13

16.00 447.56 447.64 0.08

17.00 448.56 448.54 –0.02

18.00 449.56 449.47 –0.09

19.00 450.56 450.46 –0.10

20.00 451.56 451.37 –0.19

21.00 452.56 452.47 –0.09

22.00 453.56 453.38 –0.18

23.00 454.56 454.41 –0.15

24.00 455.56 455.47 –0.09

25.00 456.56 456.57 0.01

26.00 457.56 457.42 –0.14

27.00 458.56 458.71 0.15

28.00 459.56 459.36 –0.20

29.00 460.56 460.39 –0.17

29.90 461.46 461.31 –0.15

Table 5. Calibration of hydraulic model to water-surface elevations at selected locations along the White River for the flood of 

April 24, 2013.

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

Location

High-water mark 

field identification 

number1

Surveyed high-water 

mark elevation 

(ft, NAVD 88)

Modeled water-surface 

elevation 

(ft, NAVD 88)

Elevation 

difference 

Intersection of Albert and Water 

Street in Edwardsport, Indiana

1 458.16 458.01 –0.15

East side of railroad track berm at 

east end of Shipping Street in 

Edwardsport, Indiana

2 458.13 457.95 –0.18

Center of State Road 358, 

approximately 575 ft east 

of bridge

3 456.88 456.73 –0.15

40 feet upstream from State Road 

358 on west end of bridge

5 456.68 456.73 0.05

60 feet downstream from State 

Road 358 on right side

4 456.83 456.7 –0.13

1

 U.S.Geological Survey field survey of high-water marks for the flood of April 24, 2013, collected April 26, 2013.
8 Flood-Inundation Maps for the White River near Edwardsport, Indiana

Development of Water-Surface Profiles

The calibrated hydraulic model was used to generate 

water-surface profiles for a total of 19 stages at approximately 

1-ft intervals between 12 ft and 29.9 ft as referenced to USGS 

streamgage 03360730, White River near Edwardsport, Ind. 

Discharges corresponding to the various stages were obtained 

from the most current stage-discharge relation (USGS rating 

no. 3, May 30, 2014) at USGS streamgage 03360730, White 

River near Edwardsport, Ind. Calibration of the model was 

also aided by the collection of high-water marks from the 

flood of April 24, 2013.

Discharges for all profiles (table 3) were selected with the 

assumption that there are no significant tributary or groundwater inflows within the 3.3-mi study reach. The discharges were 

estimated to be uniform and steady throughout the study reach. 

Development of Flood-Inundation Maps

Flood-inundation maps were created for a reach of the 

White River near Edwardsport, Ind. The maps were created in 

a GIS by combining the 19 water-surface profiles and digital 

elevation model data. The DEM data were derived from the 

same lidar data described previously in the “Topographic and 

Bathymetric Data” section and therefore have an estimated 

vertical accuracy of 2 ft (that is, plus or minus 1 ft). Estimated 

flood-inundation boundaries for each simulated profile were 

developed with HEC–GeoRAS software (U.S. Army Corps 

of Engineers, 2009), which allows the preparation of geometric data for import into HEC–RAS and processes simulation results exported from HEC–RAS (U.S. Army Corps of 

Engineers, 2010). Shapefile polygons and depth grids of the 

inundated areas for each profile were modified, as required, in 

the ArcMap application of ArcGIS to ensure a hydraulically 

reasonable transition of the flood boundaries between modeled 

cross sections. 

Any inundated areas that were detached from the main 

channel were examined to identify subsurface connections 

with the main river, such as through culverts under roadways. 

Where such connections existed, the mapped inundated areas 

were retained in their respective flood maps; otherwise, the 

erroneously delineated parts of the flood extent were deleted. 

The flood-inundation areas are overlaid on high-resolution, 

geo-referenced, aerial photographs of the study area. Bridge 

surfaces are displayed as inundated regardless of the actual 

water-surface elevation in relation to the lowest structural 

chord of the bridge or the bridge deck.

Estimates of water depth can be obtained from the depthgrid data that are included with the presentation of the flood 

maps on an interactive USGS mapping application described 

in the following section. The flood-inundation map corresponding to the highest simulated water-surface profile, a 

stage of 29.9 ft, is presented in figure 2.

Flood-Inundation Map Delivery

A Flood Inundation Mapping Science Web site (U.S. 

Geological Survey, 2014d) has been established to make 

USGS flood-inundation study information available to the 

public; that site links to a mapping application that presents 

map libraries and provides detailed information on flood 

extents and depths for modeled sites. The mapping application 

enables the production of customized flood-inundation maps 

from the map library for White River near Edwardsport, Ind. A 

link on this Web site connects to the USGS NWIS (U.S. Geological Survey, 2014a), which presents the current stage and 

streamflow at the USGS streamgage 03360730 to which the 

flood-inundation maps are referenced. A second link connects 

to the NWS AHPS site (National Weather Service, 2014a) so 

that the user can obtain applicable information on forecasted 

peak flows. The estimated flood-inundation maps are displayed in sufficient detail so that preparations for flooding and 

decisions for emergency response can be performed efficiently. 

Depending on the flood magnitude, roadways are shown as 

shaded (inundated and likely impassable) or not shaded (dry 

and passable) to facilitate emergency planning and use. Above 

a stage of 18 ft, the levee on the east side of the river becomes 

effective and is shown with green shading. The levee is shown 

as overtopped at 27 ft. Bridges are shaded (that is, shown as 

inundated) regardless of the flood magnitude. A shaded building should not be interpreted to indicate that the structure is 

completely submerged, rather that bare earth surfaces in the 

vicinity of the building are inundated. In these instances, the 

water depth (as indicated in the mapping application by holding the cursor over an inundated area) near the building would 

be an estimate of the water level inside the structure, unless 

flood-proofing measures had been implemented.

Disclaimer for Flood-Inundation Maps

The flood-inundation maps 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.
Creation of Flood-Inundation Map Library 9

87°15' 87°12'30"

38°50'

38°47'30"

EXPLANATION

Limit of study area

Flow arrow—Indicates 

direction of water flow

Levee

67

U.S. Geological Survey

streamgage and number

State Road marker

03360730

Flood-inundation area

03360730

Edwardsport N Ott Rd

Hammelman Rd

67

N 300 W

N Freelandville Rd

358

358

67

White

River

Projection: Indiana State Plane Coordinate System Eastern Zone

Horizontal coordinate information is referenced to the North American Datum of 1983

Orthophotography from Esri ArcGIS World Imagery, 

2011, available at http://goto.arcgisonline.com/maps/World_Imagery

Figure 2. Flood-inundation map for the White River near Edwardsport, Indiana, corresponding to a 

stage of 29.9 feet at the U.S. Geological Survey streamgage (03360730).

EDWI3

National Weather Service

Advanced Hydrologic

Prediction Service site

EDWI3

FREI3

Albert St Water St

Shipping St

Railroad

INDIANA

Study area

0 0.5 1 MILE

0 0.5 1 KILOMETER

Power-generating

plant

Figure 2. Flood-inundation map for the White River near Edwardsport, Indiana, corresponding to a stage of 29.9 feet at the U.S. 

Geological Survey streamgage (station number 03360730).
10 Flood-Inundation Maps for the White River near Edwardsport, Indiana

Uncertainties and Limitations Regarding 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 on the basis of water stages and streamflows at 

selected USGS streamgages. Water-surface elevations along 

the stream reaches were estimated by steady-state hydraulic 

modeling, assuming unobstructed flow, and using streamflows and hydrologic conditions anticipated at the USGS 

streamgage. The hydraulic model reflects the land-cover 

characteristics and any bridge, dam, levee, or other hydraulic 

structures existing as of March 2013. Unique meteorological 

factors (timing and distribution of precipitation) may cause 

actual streamflows along the modeled 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 because of unanticipated conditions such as changes in the streambed elevation 

or roughness, backwater into major tributaries along a main 

stem river, 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 DEM used to simulate the land 

surface.

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

conjunction with 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 (and 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 in the future in many 

locations). For more information on AHPS forecasts, please 

refer to http://water.weather.gov/ahps/forecasts.php.

An additional source of uncertainty is pertinent to the 

White River near Edwardsport. The flood maps show a levee 

east of the river and midway to the east side of the study area 

that is to protect agricultural areas from flooding. The extent 

and depth of flooding that occur on the landward side of this 

levee are uncertain, yet the fields are shown as inundated at 

the 29.9 ft stage (fig. 2). The extent and depth of flooding will 

vary with the elevation of the water surface in the river and the 

length of time that the water level remains above the elevation 

of low spots on the levee. Because the actual extent and depth 

of flooding in these leveed areas during a particular flood 

event are uncertain, the flood-inundation maps show flooding as the “worst-case” scenario (that is, the maximum flood 

extent that would occur if the levee did not exist). The “areas 

of uncertainty due to a levee” are displayed in green to reflect 

this uncertainty and in blue when a levee is circumvented or 

overtopped. Additional uncertainties and limitations pertinent 

to this study may be described elsewhere in this report.

Summary

A series of 19 digital flood-inundation maps were 

developed in cooperation with the Indiana Department of 

Transportation for the White River near Edwardsport from 

2.4 miles (mi) upstream from the U.S. Geological Survey 

(USGS) streamgage 03360730 at the State Road 358 bridge 

to 0.94 mi downstream from the streamgage. The flood-inundation maps were developed by using the U.S. Army Corps of 

Engineers’ HEC–RAS and HEC–GeoRAS programs to compute water-surface profiles and to delineate estimated floodinundation areas and depths of flooding for selected stream 

stages. The HEC–RAS hydraulic model was calibrated to the 

current stage-discharge relation at the White River streamgage 

and to the flood of April 2013. The model was used to compute 19 water-surface profiles for flood stages at approximately 1-foot intervals referenced to the streamgage datum 

and ranging from 12 ft, or near bankfull, to 29.9 ft, which is 

the highest stage of the stage-discharge rating. The simulated 

water-surface profiles were then combined with a geographic 

information system digital elevation model derived from light 

detection and ranging (lidar) data to delineate estimated floodinundation areas as shapefile polygons and depth grids for 

each profile. These flood-inundation polygons were overlaid 

on high-resolution, geo-referenced, aerial photographs of the 

study area. The flood maps are available through a mapping 

application that can be accessed on the USGS Flood Inundation Mapping Science Web site (http://water.usgs.gov/osw/

flood_inundation).

Interactive use of the maps on the USGS mapping application can give users a general indication of depth of water at 

any point by using the mouse cursor to click within the shaded 

areas. The mapping application enables the production of customized flood-inundation maps from the map library for White 

River near Edwardsport, Indiana. These maps, in conjunction 

with the real-time stage data from the USGS streamgage, 

White River near Edwardsport, Ind. (station number 

03360730), and forecasted flood stage data from the National 

Weather Service Advanced Hydrologic Prediction Service, 

will help to guide the general public in taking individual safety 

precautions and will provide emergency management personnel with a tool to efficiently manage emergency flood operations and post-flood recovery efforts.
References Cited 11

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Fowler—Flood-Inundation Maps for the White River near Edwardsport, Indiana—Scientific Investigations Report 2014–5219

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20145219