U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2019–5063

Prepared in cooperation with the U.S. Department of Agriculture,

Natural Resources Conservation Service

Estimating Potential Wetland Extent along Selected River 

Reaches in Indiana using Streamflow Statistics and FloodInundation Mapping Techniques
Cover. Flooded corn field adjacent to the White River in Knox County, Indiana. Photographs by 

Madelyn Messner, U.S. Geological Survey, June 19, 2019.
Estimating Potential Wetland Extent along 

Selected River Reaches in Indiana using 

Streamflow Statistics and Flood-Inundation 

Mapping Techniques

By Kathleen K. Fowler, Benjamin J. Sperl, and Moon H. Kim

Prepared in cooperation with the U.S. Department of Agriculture,

Natural Resources Conservation Service

Scientific Investigations Report 2019–5063

U.S. Department of the Interior

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

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2019

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

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

Suggested citation:

Fowler, K.K., Sperl, B.J., and Kim, M.H., 2019, Estimating potential wetland extent along selected river reaches in 

Indiana using streamflow statistics and flood-inundation mapping techniques: U.S. Geological Survey Scientific Investigations Report 2019–5063, 12 p., https://doi.org/10.3133/sir20195063.

ISSN 2328-0328 (online)
iii

Contents

Acknowledgments........................................................................................................................................iv

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

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

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

Previous Study.......................................................................................................................................2

Selection of River Reaches.................................................................................................................2

Methods...........................................................................................................................................................4

Compilation of Streamflow Statistics ................................................................................................4

Estimation of Water-Surface Elevations...........................................................................................4

Mapping of Wetlands Extent...............................................................................................................4

Geoprocessing Tools...................................................................................................................4

The “Draw Transects” Tool...............................................................................................8

The “Delineate Wetlands” Tool........................................................................................8

Validation of Estimated 7MQ2 Profiles ..............................................................................................8

Uncertainties and Limitations Regarding Use of Wetland Inundation Maps ...........................10

Transferability of Methods .........................................................................................................................11

Summary........................................................................................................................................................11

Selected References...................................................................................................................................11

Figures

1. Map showing location of selected river reaches in Indiana, Ohio, and Illinois.................3

2. Map showing location of the study reach for the Flatrock River between

Columbus and St. Paul, Indiana, and mapped extent of inundation from 7MQ2

flow..................................................................................................................................................7

3. Graph showing comparison of historical flood profile elevations to estimated

7MQ2 elevations along the Kankakee River in Indiana..........................................................9

4. Graph showing comparison of historical flood profile elevations to estimated

7MQ2 and 7MQ2 using high-water mark elevations along the East Fork White

River in Indiana .............................................................................................................................9

Tables

1. Calculated values of inundation flows and corresponding inundation elevations at

selected U.S. Geological Survey streamgages along the river reaches.............................5

2. River reaches that required the use of high-water marks for calibration of the

7MQ2 profile ................................................................................................................................10
iv

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2)

Flow rate

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

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.

Abbreviations

7MQ2 annual highest 7-consecutive-day mean discharge with a 2-year recurrence interval

ACEP Agricultural Conservation Easement Program

DEM digital elevation model

Esri Environmental Systems Research Institute

GIS geographic information system

NRCS Natural Resources Conservation Service

USGS U.S. Geological Survey

WRP Wetland Reserve Program

Acknowledgments

The authors wish to thank the U.S. Department of Agriculture, Natural Resources Conservation 

Service, for the funding of this study. Special thanks are given to Christian T. Ritz, Chris Morse, 

and Kenny Streett of the Natural Resources Conservation Service, Indianapolis office, for their 

review and valuable input throughout the entire study.
Estimating Potential Wetland Extent along Selected River 

Reaches in Indiana using Streamflow Statistics and FloodInundation Mapping Techniques

By Kathleen K. Fowler, Benjamin J. Sperl, and Moon H. Kim

Abstract

In this study potential wetland extents were estimated for 

12 river reaches covering about 750 river miles in Indiana and 

parts of Illinois and Ohio. The study was completed by the 

U.S. Geological Survey in cooperation with the U.S. Department of Agriculture, Natural Resources Conservation Service. 

This study follows and adds to the work completed in a pilot 

study and determines that potential wetland extents can be 

estimated using streamflow statistics, streamgage data, and 

flood-inundation mapping techniques.

The study was designed to assist in the Agricultural Conservation Easement Program. The Agricultural Conservation 

Easement Program is a voluntary program administered by the 

Natural Resources Conservation Service that provides technical and financial assistance to private landowners and Tribes to 

restore, protect, and enhance wetlands in exchange for retiring 

eligible land from agriculture. For a site to be eligible for wetland restoration, it should be in a zone with sustained or frequent flooding. This study calculated the flows that lasted for 

a period of 7 consecutive days on average at least once every 

2 years (a value termed the “7MQ2”) for all the U.S. Geological Survey streamgages within the selected river reaches. 

These 7MQ2 flows were related to the stage-discharge tables 

for each streamgage, and a corresponding water-surface 

elevation was determined. Maps of estimated wetland extent 

were prepared using the 7MQ2 inundation elevation data in 

conjunction with bare-earth land-surface elevation data made 

publicly available through the online geospatial data clearinghouses of Indiana, Illinois, and Ohio. Flood-inundation 

mapping techniques were applied with the aid of geographic 

information system software to generate water-surface planes 

that represent inundation elevations associated with the 7MQ2 

streamflow. Land-surface elevation data from high-resolution 

digital elevation models were subtracted from the watersurface planes to produce maps of wetland extent. The 12 map 

products, including datasets and geoprocessing tools, produced 

from this study will aid the National Resources Conservation 

Service and its partners with the onsite inundation-zone verification in agricultural land for potential restoration.

Introduction

Wetlands are transitional areas of land between terrestrial 

and deeper-water habitats like rivers or streams. They can be 

vegetated or barren, but the water table is commonly at or 

near the land surface or the area can be covered with water. 

Wetlands are classified by hydrology, vegetation, and substrate 

(Cowardin and others, 1979). This report concentrates on the 

hydrology classification.

Wetlands provide benefits to surrounding ecosystems 

by serving numerous hydrological and ecological functions. 

Reducing streamflow velocity and flood peaks is a flood 

control method that can be implemented near wetlands by 

storing water temporarily and releasing it gradually. Wetlands 

improve water quality because they absorb excess nutrients 

that can degrade ground and surface water. Stream channels can be maintained by stabilizing the land surface with a 

variety of vegetation that grows well in wetlands. Wetlands 

serve as habitat for many animals, migrating birds, and diverse 

plant life (Indiana Department of Natural Resources, 1996). 

Wetlands also can be valuable assets because they provide 

educational, economic, and recreational activities such as 

boating, swimming, hiking, birding, fishing, and hunting. 

Interest in the conservation and management of wetlands has 

increased because their function and value to the environment 

and society have become better understood (U.S. Geological 

Survey, 1996).

Wetlands are an important part of the Nation’s natural 

resources; however, during a period of about 200 years, from 

the 1780s to the 1980s, the total estimated loss of wetlands in 

the conterminous United States was about 53 percent, from 

about 221 million acres to about 104 million acres (Dahl, 

1990). During the same time, Indiana lost about 87 percent of 

its wetlands, decreasing from about 5.6 million acres to about 

751,000 acres (Indiana Department of Natural Resources, 

1996). Wetlands in Indiana and across the country were being 

lost at a rate of about 1–3 percent each year, mainly because 

of drainage for agricultural purposes (U.S. Geological Survey, 

1996); however, during 1998–2004, the trend was reversed. 

Studies completed by the U.S. Fish and Wildlife Service 
2 Estimating Potential Wetland Extent along Selected River Reaches in Indiana

indicate that wetland gains have surpassed wetland losses, and 

the United States is gaining about 32,000 acres of wetlands each 

year. The increase is due to agricultural conservation plans, wetland restoration, land retirement programs, and the construction 

of freshwater ponds (U.S. Fish and Wildlife Service, 2004). The 

Natural Resources Conservation Service (NRCS) also notes an 

increase in wetlands from 1997 to 2007 in the 2010 Summary 

Report (U.S. Department of Agriculture, 2013).

The Agricultural Conservation Easement Program 

(ACEP) was established by the Agricultural Act of 2014. It 

repealed the Wetland Reserve Program (WRP) created by the 

1990 Food, Agriculture, Conservation, and Trade Act but did 

not affect the validity or terms of any WRP contract entered 

into before February 7, 2014. Like the WRP, the ACEP is a 

voluntary program, administered under the U.S. Department of 

Agriculture, NRCS, that provides technical and financial assistance to private landowners to restore, protect, and enhance 

wetlands in exchange for retiring eligible land from agriculture (U.S. Department of Agriculture, 2017). Landowners can 

contact their local NRCS office if they are interested in participating in the ACEP. If an agricultural land contains degraded 

wetlands that have a high chance for successful restoration, the 

land may be eligible for participation. The hydrology criteria 

for an agricultural site to be eligible for wetland restoration 

require that the land be in a zone with sustained or frequent 

flooding for a period of 7 consecutive days on average at least 

once every 2 years (a flow statistic called the “7MQ2”) or 

be saturated for at least 14 days during the growing season. 

If an agricultural site meets these criteria, and is selected for 

participation, the NRCS develops a restoration plan and makes 

an offer to the landowner (U.S. Department of Agriculture, 

2007). For this study, the focus was on the 7MQ2 criterion 

only. Because this flow statistic represents the mean value of 

the 7-day high flow, it necessarily represents an estimate that 

is conservative. The estimated inundation area probably would 

not be under water for the entire 7 days. Areas that could be 

inundated are less likely to be missed using this statistic.

In this study, wetland extents were estimated for 12 river 

reaches covering about 750 river miles in Indiana and parts 

of Ohio and Illinois. The river reaches were selected by the 

NRCS and the U.S. Geological Survey (USGS) as river basins 

that contain two or more USGS streamgages and are in areas 

where potential wetland information is needed for restoration 

under the ACEP.

Purpose and Scope

This report presents the methods used to estimate the 

potential wetland extents for 12 river reaches in Indiana and 

parts of Ohio and Illinois (fig. 1). New methods were needed 

to expand the library of maps used by the NRCS in determining agricultural areas that can be restored to wetlands. 

The methods for map preparation are documented, and the 

datasets used in all calculations are available through a USGS 

data release at https://doi.org/10.5066/P9LGXDJ8 (Fowler 

and others, 2019). In addition to the data release, the library 

of maps produced by this study can also be viewed through 

an Esri story map at https://wim.usgs.gov/geonarrative/

indianawetlands/.

Previous Study

In 2012, a pilot study was completed by the USGS in 

cooperation with the NRCS to document that potential wetland extents can be estimated using streamflow statistics and 

flood-inundation mapping techniques (Kim and others, 2012). 

The pilot study was done to assist the NRCS and its staff in 

planning a wetland restoration following the WRP guidelines. 

Several criteria must be satisfied regarding vegetation, soils, 

and hydrology before a site in agricultural land area is deemed 

to be a wetland and considered for restoration. The pilot study 

focused on the hydrology criterion of the WRP guidelines, 

which requires determination and identification of areas indicating evidence of sustained or frequent flooding for a period 

of 7 consecutive days at least once every 2 years on average. 

The stream reach selected for the study was the Wabash River 

near Terre Haute, Indiana.

Upon completion of the pilot study, the NRCS and 

USGS realized the need for an expanded study that would 

furnish datasets for additional river reaches in Indiana where 

new requests for wetland restoration were being submitted 

by agricultural land owners. This need would require that the 

aging computer scripts used in the pilot study (Kim and others, 

2012) be updated because they were written in the ARC Macro 

Language and are no longer fully supported by Esri; thus, the 

fundamental methods of the pilot study were incorporated into 

the programming of a new set of geoprocessing tools implemented in an ArcGIS Python Toolbox (.pyt).

Selection of River Reaches

A total of 12 river reaches were selected by the NRCS 

and the USGS as river basins that contain 2 or more USGS 

streamgages and are in areas where potential wetland information is needed for restoration under the ACEP (fig. 1). Each 

streamgage was required to have at least 10 years of record 

to provide enough data to determine streamflow statistics and 

have an established rating curve from which to obtain the 

stage/discharge relation. In addition to streamgages, highresolution elevation data were needed. Indiana currently (since 

2011) has high-resolution elevation data (Woolpert, 2011), and 

all river reaches in the State were included in the new digital 

elevation models (DEMs). For areas in Ohio, elevation data 

were obtained from the Ohio Office of Information Technology (Ohio Geographically Referenced Information Program, 

2018). Illinois elevation data were downloaded from the 

Illinois Natural Resources Geospatial Data Clearinghouse, Illinois State Geological Survey (2018). Historical flood profiles 

from the Indiana Department of Natural Resources were used 

to check the estimated 7MQ2 elevations along each reach.
Introduction 3

42°

41°

88°

87°

42° 42°

84°

84°

40°

86°

87°

38°

39°

40°

86° 86°

85°

85°

St. Joseph River Basin

Whitewater 

River Basin

Lake Michigan Basin

Kankakee 

River Basin

Middle Wabash 

River Basin

Upper Wabash River Basin

Maumee River Basin

Miami River Basin

White and 

West Fork White

River Basin

Lower Wabash River Basin

East Fork White River Basin

Patoka River Basin

Ohio River Basin

24

7

6 5

4

3 2

39

37

36

35

33

32

31

30

29

28

27

26

25

23 22 21

20 19

18

17

16

15

14

13

12

11

10

9 8

38

34

1

#

#

#

#

#

## #

#

##

#

#

#

#

# #

# # ##

# # #

#

#

#

#

#

#

##

#

#

#

#

#

#

#

KNOX

OHIO

OWEN

CLAY VIGO

CASS

POSEY PERRY

FLOYD

CLARK

UNION

PARKE

WAYNE

BOONE

GRANT

WHITE

NOBLE

GIBSON

GREENE

RIPLEY

PUTNAM

TIPTON

WARREN

BENTON HOWARD

WABASH

FULTON

SPENCER

WARRICK

DAVIESS

CLINTON

CARROLL

PULASKI

WHITLEY

HARRISON CRAWFORD

SULLIVAN

DEARBORN

FRANKLIN

RANDOLPH

FOUNTAIN DELAWARE

LAGRANGE

BLACKFORD

KOSCIUSKO

VERMILLION

ELKHART

STEUBEN

MIAMI

HUNTINGTON

JAY TIPPECANOE

HAMILTON

MONTGOMERY

HENDRICKS MARION

MORGAN

SWITZER- LAND

VANDERBURGH

UNION

FAYETTE

MADISON

PIKE

RUSH

SCOTT

BROWN

HENRY

WELLS ADAMS

DUBOIS

MONROE

NEWTON

JASPER

STARKE

JACKSON

DECATUR

HANCOCK

LAWRENCE

MARSHALL

LA PORTE

JEFFERSON

ST. JOSEPH

WASHINGTON

LAKE

PORTER

DEKALB

ALLEN

JOHNSON

SHELBY

BARTHOLOMEW

JENNINGS

MARTIN

ORANGE

River reach studied

River basin boundary

State boundary 

U.S. Geological Survey streamgage 

and map number. Streamgage 

information is listed in table 1. 

25 #

EXPLANATION

MAD19_1911_IP097069_fig01

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983 

Universal Transverse Mercator projection zone 16 

North American Datum of 1983

INDIANA

Map

area

MICHIGAN

OHIO

KENTUCKY

ILLINOIS

Figure 1. Location of selected river reaches in Indiana, Ohio, and Illinois.
4 Estimating Potential Wetland Extent along Selected River Reaches in Indiana

Methods

Procedures were developed to determine streamflow 

and water-surface elevation along selected reaches in Indiana 

to allow estimation of inundation elevations and inundation 

extent that meet the ACEP planning guidelines. The procedure 

consists of three steps: (1) compilation of streamflow statistics, 

(2) estimation of water-surface elevations based on streamflow 

statistics, and (3) mapping of estimated wetland extents. 

Compilation of Streamflow Statistics

The ACEP planning guidelines state that to meet the 

planning criteria for restoring agricultural land to wetlands, 

a site needs to provide evidence of being in an area prone to 

sustained or frequent flooding for a period of 7 consecutive 

days at least once every 2 years on average or be saturated 

for at least 14 days during the growing season. The evidence 

can be obtained through statistical analysis of daily mean 

discharges computed from the historical records of USGS 

streamgages. The statistical value generated by this analysis is 

the annual highest 7-consecutive-day mean discharge with a 

2-year recurrence interval. The 7MQ2 at a streamgage serves 

as a determination of the inundation flow at that location. 

Daily mean discharges for the streamgages used in this study 

are stored in the USGS National Water Information System at 

https://waterdata.usgs.gov/nwis. Based on those daily mean 

discharges, the set of annual highest 7-consecutive-day mean 

discharges was calculated for each streamgage. The water 

year rather than the calendar year was used as the annual 

period for this flow statistic. A water year is defined as the 

12-month period from October 1 to September 30 and is 

designated by the year in which it ends. By separating annual 

periods at the time of year when discharges are generally 

low, the high flows can be analyzed with a greater degree of 

continuity.

The set of annual highest 7-consecutive-day mean discharges at each streamgage was used for the frequency analysis. Frequency curves relate the magnitude of a variable to 

the frequency of occurrence (Riggs, 1968). For this frequency 

analysis, the 7-consecutive-day mean discharge time-series 

data were analyzed using a log-Pearson Type-III distribution, 

as implemented in the USGS software package SWToolbox 

(Kiang and others, 2018).

This frequency analysis produced the 7MQ2, which was 

used as the inundation flow. Resulting data for streamgages 

along the selected river reaches are listed in table 1. For the 

streamflow data to better represent current conditions, the 

datasets included only those years after installation of floodcontrol reservoirs upstream from the river reaches (Ruddy and 

Hitt, 1990). The datasets for each streamgage are available 

in the data release (Fowler and others, 2019). Locations and 

other information regarding the streamgages can be found 

in the National Water Information System (U.S. Geological 

Survey, 2018a).

Estimation of Water-Surface Elevations

Water-surface elevations corresponding to the 7MQ2 

streamflow were determined using the active or most recent 

stage-discharge relation for each of the selected streamgages 

at the time of this study (table 1). This relation is commonly 

referred to as the “rating” and is developed based on periodic, 

in-situ measurements of stage and discharge by hydrologic 

technicians (Rantz and others, 1982). Values of stage are 

derived from the rating and added to the vertical datum of the 

streamgage, effectively converting stage to inundation elevations that are referenced to the North American Vertical Datum 

of 1988 (NAVD 88). Conversion of stage to an elevation is 

necessary to make the data comparable among sites.

Mapping of Wetlands Extent

Maps of estimated wetland extent were prepared using 

USGS streamflow-derived inundation elevation data that meet 

the planning criteria for the ACEP in conjunction with publicly 

available bare-earth land-surface elevation data from the 

online geospatial data clearinghouses of Indiana, Illinois, and 

Ohio. Flood-inundation mapping techniques were applied with 

the aid of geographic information system software to generate water-surface planes that represent inundation elevations 

associated with the 7MQ2 streamflow. Land-surface elevation data from high-resolution digital elevation models were 

subtracted from the water-surface planes to produce maps of 

wetland extent.

A total of 12 wetland inundation maps were prepared. 

The raster and vector files for each study reach are available as 

a data release at https://doi.org/10.5066/P9LGXDJ8 (Fowler 

and others, 2019). Of the 12 reaches, 1 is along the Flatrock 

River and is shown in figure 2. The blue area is the estimated 

inundation extent of the 7MQ2 flow and is the hydrologic 

component of the criteria used to determine eligibility in the 

ACEP. Using such a map, property owners and the NRCS 

could evaluate the potential for removing land from agricultural uses and restoring that land back to a wetland.

Geoprocessing Tools

Two scripts named “Draw Transects” and “Delineate 

Wetlands” were written and configured as geoprocessing tools 

in an ArcGIS Python toolbox (.pyt) so that the workflow could 

be carried out in a semiautomated manner with user input 

required to initialize tool parameters. The parameters were 

refined by examining the output after each successive run. 

Development of the toolbox was in part motivated by a need 

to make the workflow more time efficient, but also to allow 

reproducibility of the results and to improve documentation. 

The grouping of processing tasks into separate tools reflects 

a natural break in the workflow whereby the output from the 

“Draw Transects” tool is examined before being used as input 

to execute the “Delineate Wetlands” tool. Both tools rely 
Methods 

5

Table 1. Calculated values of inundation flows and corresponding inundation elevations at selected U.S. Geological Survey streamgages along the river reaches.[mi2, square mile; NAD 83, North American Datum of 1983; 7MQ2, annual highest 7-consecutive-day mean discharge with a 2-year recurrence interval; ft3/s, cubic foot per second; ft, foot; NAVD 88, North 

American Vertical Datum of 1988]

Map 

number 

(fig. 1)

Streamgage name Streamgage number County Drainage area (mi2) Period of record River mile above mouth Latitude (NAD 83) Longitude (NAD 83) 7MQ2 (ft3/s) through water year 20151 Rating table number Stage (ft) Datum of streamgage (NAVD 88) 7MQ2 elevation (ft) (NAVD 88)

1 East Fork White River at Seymour, 

Indiana

03365500 Jackson 2,341 1928–2015 214.6 38.98255300 −85.89914440 19,937 61 16.11 550.26 566.37

2 East Fork White River near Bedford, 

Indiana

03371500 Lawrence 3,861 1940–2015 153.3 38.77033029 −86.40971150 29,164 25 25.78 473.08 498.86

3 East Fork White River at Shoals, 

Indiana

03373500 Martin 4,927 1904–2015 105.4 38.66699568 −86.79194299 32,977 43 20.99 441.91 462.90

4 Kankakee River at Davis, Indiana 05515500 Starke 542 1926–2015 110.1 41.38963889 −86.70616670 1,196 46 9.64 664.34 673.985 Kankakee River at Dunns Bridge, 

Indiana

05517500 Porter 1,352 1949–2015 90.8 41.22003920 −86.96835600 3,668 26 10.01 649.18 659.19

6 Kankakee River near Kouts, Indiana 05517530 Jasper 1,376 1975–2015 86.7 41.25392760 −87.03391400 3,912 8 11.60 644.69 656.297 Kankakee River at Shelby, Indiana 05518000 Newton 1,779 1924–2015 68.0 41.18281340 −87.34030960 4,398 34 10.75 627.94 638.698 Wabash River at Linn Grove, Indiana 03322900 Adams 453 1965–2015 445.2 40.65615729 −85.03274660 3,568 15 10.29 807.34 817.639 Wabash River near Bluffton, Indiana 03322985 Wells 508 2002–2014 436.6 40.72810220 −85.13663650 4,355 5 12.56 794.78 807.34

10 Wabash River at Bluffton, Indiana 03323000 Wells 532 1931–1971 434.5 40.74236110 −85.17144440 3,605 28 10.03 792.57 802.60

11 Wabash River at Huntington, Indiana 03323500 Huntington 721 1970–2002 409.5 40.85325000 −85.48977780 4,155 10 14.28 699.57 713.85

12 Wabash River at Wabash, Indiana 03325000 Wabash 1,768 1969–2015 387.2 40.79087650 −85.82026320 7,593 37 11.16 642.15 653.3113 White River at Spencer, Indiana 03357000 Owen 2,988 1926–1971 165.9 39.28115610 −86.76222800 20,412 41 18.01 525.57 543.5814 White River at Newberry, Indiana 03360500 Greene 4,688 1943–2015 112.4 38.92811110 −87.01927780 30,167 58 17.45 465.08 482.5315 White River at Petersburg, Indiana 03374000 Pike 11,125 1929–2015 45.7 38.51088224 −87.28945830 67,789 42 23.71 399.38 423.0916 White River at Hazleton, Indiana 03374100 Gibson 11,305 1929–2013 18.8 38.48976950 −87.55002269 63,795 8 23.51 382.77 406.2817 Wildcat Creek near Jerome, Indiana 03333450 Howard 146 1962–2015 79.9 40.44127778 −85.91875000 1,302 24 6.89 819.63 826.5218 Wildcat Creek at Kokomo, Indiana 03333700 Howard 242 1956–2015 62.9 40.47088889 −86.15291670 2,008 33 7.95 775.23 783.1819 Wildcat Creek at Owasco, Indiana 03334000 Carroll 396 1945–1973, 

1988–2015

23.0 40.46483330 −86.63655560 2,900 32 6.55 624.28 630.83

20 Wildcat Creek near Lafayette, Indiana 03335000 Tippecanoe 794 1955–2015 4.8 40.44059108 −86.82917520 6,078 29 11.29 527.04 538.3321 Patoka River at Jasper, Indiana 03375500 Dubois 262 1979–2015 91.5 38.41366457 −86.87666360 1,510 36 14.18 445.22 459.4022 Patoka River at Winslow, Indiana 03376300 Pike 603 1987–2015 41.3 38.38032750 −87.21667529 5,002 23 24.30 399.60 423.9023 Patoka River near Princeton, Indiana 03376500 Gibson 822 1979–2015 21.4 38.39032397 −87.54891090 5,394 38 20.29 388.56 408.8524 Flatrock River at St. Paul, Indiana 03363500 Shelby 303 1931–2015 34.4 39.4175493 −85.63414249 2,606 33 4.22 764.30 768.5225 Flatrock River at Columbus, Indiana 03363900 Bartholomew 534 1968–2015 2.6 39.23505140 −85.92665970 4,381 25 9.94 609.67 619.61
6 Estimating Potential Wetland Extent along Selected River Reaches in Indiana Table 1. Calculated values of inundation flows and corresponding inundation elevations at selected U.S. Geological Survey streamgages along the river reaches.—Continued [mi2, square mile; NAD 83, North American Datum of 1983; 7MQ2, annual highest 7-consecutive-day mean discharge with a 2-year recurrence interval; ft3/s, cubic foot per second; ft, foot; NAVD 88, North American Vertical Datum of 1988] Map number (fig. 1) Streamgage name Streamgage number County Drainage area (mi2

)

Period of 

record

River mile 

above 

mouth

Latitude

(NAD 83)

Longitude

(NAD 83)

7MQ2 

(ft3/s) through 

water year 

20151

Rating 

table 

number

Stage 

(ft)

Datum of 

streamgage 

(NAVD 88)

7MQ2 

elevation 

(ft) 

(NAVD 88)

26 Whitewater River near Economy, 

Indiana

03274650 Wayne 10 1971–2012 91.9 40.00421314 −85.11552010 97 21 4.61 1065.55 1,070.16

27 Whitewater River near Hagerstown, 

Indiana

03274750 Wayne 59 1971–2003 84.9 39.87365765 −85.16302030 446 18 5.34 949.55 954.89

28 Whitewater River near Alpine, Indiana 03275000 Fayette 522 1929–2015 54.8 39.57949280 −85.15801900 4,180 67 11.42 749.71 761.13

29 Whitewater River at Brookville, 

Indiana

03276500 Franklin 1,224 1975 –2015 29.3 39.40747220 −85.01288889 7,850 60 8.24 595.12 603.36

30 Maumee River at Coliseum Blvd at 

Fort Wayne, Indiana

04182950 Allen 1,930 2005–2015 133.4 41.07977060 −85.08746960 14,551 3 19.27 727.66 746.93

31 Maumee River at New Haven, Indiana 04183000 Allen 1,967 1957–2015 129.0 41.08504866 −85.02219040 11,975 31 16.90 723.95 740.85

32 Maumee River at Antwerp, Ohio 04183500 Paulding 

(Ohio)

2,129 1940–1981, 

2014–2015

100.6 41.19893889 −84.74440330 11,796 14 18.99 689.80 708.79

33 St. Joseph River near Newville, Indiana 04178000 Defiance 

(Ohio)

610 1948–2015 42.3 41.38560609 −84.80162590 3,615 31 13.52 794.92 808.44

34 St. Joseph River at Cedarville, Indiana 04179000 Allen 763 1957–1981 13.9 41.19616039 −85.02413519 3,910 10 9.90 757.44 767.34

35 St. Joseph River near Fort Wayne, 

Indiana

04180500 Allen 1,060 1942–1955, 

1983–2015

10.7 41.16738889 −85.07408330 6,554 9 12.13 752.99 765.12

36 St. Marys River at Decatur, Indiana 04181500 Adams 621 1948–2015 29.1 40.84810299 −84.93774410 4,416 34 18.19 760.12 778.31

37 St. Marys River near Fort Wayne, 

Indiana

04182000 Allen 762 1932–2015 10.8 40.98782570 −85.11191400 5,564 32 12.25 748.41 760.66

38 Wabash River at Riverton, Indiana 03342000 Sullivan 13,161 1970–20152 162.0 39.02032020 −87.56863440 60,960 31 22.09 414.20 436.29

39 Wabash River at Mount Carmel, 

Illinois

03377500 Wabash (Ill.) 28,635 1928–2015 94.2 38.39833330 −87.75638889 135,310 18 26.52 368.98 395.50

1Data computed using SWToolbox (Kiang and others, 2018).2Regulated period.
Methods 

7

MAD19_1911_IP097069_fig02

0 2 4 6 8 MILES0 2 4 6 8 KILOMETERS

Map image is the intellectual property of Esri and is used herein under license. Copyright © 2014 Esri and its licensors. All rights reserved

Study area inundated by 7MQ2 flow (annual highest Municipal boundaries

7-consecutive-day mean discharge with a 2-year recurrence interval)

Flow arrow—Indicates direction of water flow State road marker 9U.S. Geological Survey streamgage and number 

03363900

Elevation of 7MQ2 discharge at the streamgage, in feet 

above the North American Vertical Datum of 1988 619.61 

EXPLANATION

INDIANA

Study 

area 

03363500

768.52

03363900

619.61

9

Flow

Flow

St. Paul

Hope

Columbus

85°45' 85°37'30" 85°52'30"

39°26'

39°20'30"

39°15'

Figure 2. Location of the study reach for the Flatrock River between Columbus and St. Paul, Indiana, and mapped extent of inundation from 7MQ2 flow.
8 Estimating Potential Wetland Extent along Selected River Reaches in Indiana

heavily on modules in the ArcPy site package, included with 

an ArcGIS Desktop license, but also leverage several other 

packages in the standard library distributed with Python. The 

conceptual underpinnings of these tools are described, though 

the toolbox is not released with this report. The toolbox was 

designed and developed for use by the NRCS to aid in determining areas eligible for restoration under the ACEP.

The “Draw Transects” Tool

Data from two primary sources are needed to run this 

tool: (1) flowlines from the National Hydrography Dataset 

(U.S. Geological Survey, 2017), which are extracted based 

on the name of the stream as it appears in the Geographic 

Names Information System (U.S. Geological Survey, 

2018b) and dissolved into a single polyline feature, and (2) 

water-surface elevations that are associated with the 7MQ2-

magnitude streamflow computed from historical data at 

USGS streamgages. Optionally, 7MQ2 elevations at ungaged 

locations may be estimated and used to supplement USGS 

streamgages where coverage is sparse to ensure that critical inflection points in the water-surface profile are captured. 

Inflections in the slope of the water surface commonly occur at 

artificial control structures such as low-head dams, reservoirs, 

and transportation embankments but also occur naturally with 

topographic changes in the drainage basin. Historical flood 

profiles compiled from high-water marks serve as a useful 

reference in identifying where these inflection points occur. 

Taking 7MQ2 water-surface elevation data as input, the “Draw 

Transects” tool completes a stepwise-linear interpolation at 

points generated along the stream polyline at an equal-interval 

defined by the user. In practice, this interval was generally set 

to 500 feet.

Flow direction azimuths (0–360 degrees) are calculated 

for each equal-interval point as the direction of a straight line 

connecting it to the next point downstream. A second set of 

flow direction azimuths is calculated at a more global scale 

by first smoothing the geometry of the stream polyline using 

a moving average on the x- and y-coordinates of the equalinterval points, then repeating the same calculation as before. 

Calculating global azimuths in this way is necessary to determine the predominant direction of flow of the stream. These 

azimuths aid in the drawing of transects that are perpendicular 

to the direction of flow near the stream’s main channel and the 

predominant direction of flow through the broader fluvial plain.

For the stream reaches modeled in this study, the primary consideration in determining an appropriate value for 

the length of transects was to ensure that they cross the entire 

100-year flood plain. The 7MQ2 streamflow is lesser in 

magnitude than a 100-year event; therefore, transects crossing the entire 100-year flood plain also will cover the extent 

of wetlands. Before the “Draw Transects” tool was run, the 

width of the flood plain was measured at a sample of locations 

along the stream reach using ArcGIS software, and from those 

measurements, an appropriate value for transect length was 

determined.

Once drawn, transects are attributed with the 7MQ2 

elevations of their respective points on the stream polyline and 

densified with additional vertices at the same equal interval. 

Transects that cross over the stream polyline more than once 

are deleted, and intersecting transects are deleted iteratively 

until there are no more intersections to ensure the logical 

consistency of transects drawn throughout the study area.” 

After this step, the densified vertices of transects are converted 

to point features and used to generate a triangulated irregular 

network, which is then converted to a raster format producing 

a continuous, planar model of the 7MQ2 water surface sloped 

in the downstream direction of flow.

The “Delineate Wetlands” Tool

The “Delineate Wetlands” tool completes the process by 

subtracting the land-surface elevation data from the rasterized 

7MQ2 water surface produced by “Draw Transects” tool in a 

digital elevation model covering the full extent of the study 

area. The result is an Esri Grid named “depth7mq2,” which 

represents the extent and depth of inundation associated with 

the 7MQ2 streamflow. Cells with depth values greater than 

zero are extracted and converted to a polygon feature class 

named “extent_7mq2” that represents potential wetland extent 

in vector format. No edits were made to the “extent_7mq2” 

feature class post processing. In places the “extent_7mq2” 

feature class may contain polygons in extraneous areas such 

as adjacent streams or topographic depressions that are outside 

the flood plain of the target stream reach. Users may choose to 

review the feature class for areas that may have been inadvertently inundated because of transects extending beyond the 

immediate wetland area of the target stream reach.

Validation of Estimated 7MQ2 Profiles

The validity of a 7MQ2 profile was analyzed by graphically superimposing it with profiles of the stream’s thalweg 

and historical floods. In checking the 7MQ2 profile for validity, several conditions were evaluated:

•	 Is the 7MQ2 profile above the thalweg throughout the 

entire stream reach?

•	 Is the 7MQ2 profile below historical flood events of 

greater magnitude?

•	 Are there any artificial control structures unaccounted 

for in the 7MQ2 profile?

•	 Does the slope of the 7MQ2 profile generally follow 

that of historical floods?

A profile comparison where none of the conditions are 

violated is shown in figure 3. The reach of the Kankakee 

River shown has no artificial control structures, and the 

7MQ2 profile follows the same general slope as the historical 

floods. If the 7MQ2 profile was found to violate one or more 

of these conditions, then high-water marks from a historical 
Methods 9

flood were used to supplement the elevations contributed by 

USGS streamgages as input in the geoprocessing workflow. 

The selected study reach for the East Fork White River is 

shown in figure 4. This graph illustrates that although the 

slope of the 7MQ2 profile (yellow line) is similar to the 

thalweg (light green line), it omits critical inflection points 

in the historical flood profile (dark blue line). When highwater marks were used to supplement the data points, a more 

reasonable 7MQ2 profile was produced (red line).

Historical floods that best represent the hydrology of a 

stream reach in its present state were used to necessitate the 

selection of historical floods that occurred after the construction of a dam if one presently exists on the stream reach. 

Locations, rather than the number of high-water marks used 

to supplement streamgage data, were of primary importance. 

Those at or near major inflections in the slope of the water 

surface were of greater value than those on parts of the 

stream with unchanging slope. To adjust the elevations of 

620

630

640

650

660

670

680

690

Water-surface elevation, in feet above 

North American Vertical Datum of 1988

65 70 75 80 85 90 95 100 105 110 115

River mile above mouth of Kankakee River

05515500

673.98

05517530

656.29

05517500

659.19

05518000

638.69

EXPLANATION

[7MQ2, annual highest 

7-consecutive-day mean discharge 

with a 2-year recurrence interval]

March 1982 historic 

flood profile

December 1980 historic 

flood profile

673.98 7MQ2 elevation, in feet

U.S. Geological Survey 

streamgage and number 05515500

Estimated 7MQ2 profile 

using U.S. Geological 

Survey streamgages

Thalweg

Figure 3. Comparison of historical flood profile elevations to estimated 7MQ2 elevations along the Kankakee River in Indiana.

January 2005 historic 

flood profile

Estimated 7MQ2 profile using 

adjusted HWM data

EXPLANATION

03371500

498.86

03373500

462.9

03365500

566.37

River mile above the mouth of East Fork White River

100 120 140 160 180 200 220

Water-surface elevation, in feet above 

North American Vertical Datum of 1988

425

445

465

485

505

525

545

565 [7MQ2, annual highest 

7-consecutive-day mean discharge 

with a 2-year recurrence interval; 

HWM, high-water mark]

Estimated 7MQ2 profile 

using U.S. Geological 

Survey streamgages

Thalweg

566.37 7MQ2 elevation, in feet

U.S. Geological Survey 

streamgage and number 05515500

Figure 4. Comparison of historical flood profile elevations to estimated 7MQ2 (streamgages only) and 7MQ2 using high-water mark 

elevations along the East Fork White River in Indiana.
10 Estimating Potential Wetland Extent along Selected River Reaches in Indiana

high-water marks to a level commensurate with the 7MQ2 

streamflow, the difference in elevation between the historical flood and the known 7MQ2 elevation at the location of a 

USGS streamgage was subtracted from all high-water marks 

that make up the historical flood profile. This process was 

repeated for each individual streamgage on the study reach to 

produce as many adjusted profiles as streamgages. Adjusting the elevations in this way preserves the stepwise pattern 

of the historical flood and shifts the water surface profiles 

to align with and pass through their respective streamgages. 

Distance-weighted averaging was then applied to merge each 

of the adjusted profiles into one profile that assigns greater 

weight to nearby streamgages in estimating 7MQ2 elevations at unknown locations, and thus ensures the interpolated 

profile passes through the known 7MQ2 elevations at all 

streamgage locations.

All 12 stream reaches were graphically analyzed using 

historical flood profiles and the 4 checks for validity listed 

above. Not all stream reaches required an adjustment or 

calibration if none of the conditions were violated. Dates 

of historical flood events and summaries of the number and 

coverage of high-water marks along the three study reaches 

where they were used as supplemental data are provided in 

table 2. The precise locations of the high-water marks used 

are provided in the data release for the three study reaches 

listed.

Uncertainties and Limitations Regarding Use of 

Wetland Inundation Maps

The wetland inundation maps represent the boundaries 

of inundated areas with a distinct line; however, some uncertainty is associated with these maps. The boundaries shown 

are estimated on the basis of streamflow statistics at USGS 

streamgages. The 7MQ2 streamflow statistic represents the 

mean value of the 7-day high flow. The estimated inundation 

area would probably not be under water for the entire 7 days, 

but areas that could be inundated are less likely to be missed 

using this statistic. Additional areas may be inundated because 

of unanticipated conditions such as backwater from a main 

stem river, blockage of water because of earthen embankments, or backwater from localized debris. Conversely, some 

areas that should be shown as inundated may not be because 

of changes in the streambed elevation or roughness. The accuracy of the inundation extent portrayed on these maps also will 

vary with the accuracy of the digital elevation model used to 

simulate the land surface.

As distance from a streamgage increases, so does the 

uncertainty of interpolated water-surface elevations. The 

overall accuracy of interpolation throughout a study reach is 

affected by the number and spacing of streamgages as well as 

the coverage of supplementary data points such as high-water 

marks. Changes in the slope of the water-surface profile may 

go unobserved without sufficient coverage of data points. To 

the extent possible, high-water marks from historical floods 

were used to validate results; however, distances between 

the high-water marks vary from a few feet to many miles. In 

general, data points at or near major inflections in the slope of 

the water surface are of greater value than those on parts of a 

stream with relatively unchanging slope.

The angles at which stream transects intersect with the 

fluvial plain contribute some uncertainty to inundation results 

given that the way they are drawn affects how water-surface 

elevations are extrapolated outwards from the main channel. 

Effort was made to draw transects that are perpendicular to the 

direction of flow, but highly sinuous or meandering streams 

present challenges to the automated methods that compute 

flow direction azimuths based on stream geometry. Areas 

having relatively small differences in elevation between the 

estimated 7MQ2 water surface and the land surface, such as 

areas near the boundary of the estimated wetlands, would be 

more sensitive to variations in the angles at which transects 

are drawn. With all other parameters held equal, differences 

in how transects are drawn could produce variability in the 

results, which may be less pronounced in constricted parts of 

a stream reach and more pronounced where the fluvial plain 

widens.

Table 2. River reaches that required the use of high-water marks for calibration of the 7MQ2 profile.

[7MQ2, annual highest 7-consecutive-day mean discharge with a 2-year recurrence interval; mi, mile]

River reach Downstream 

river mile

Upstream 

river mile

Number of highwater marks1

 used 

as inflection points

Month and year 

of historical flood

Average distance 

between 

high-water marks 

(mi)

Maximum distance 

between 

high-water marks 

(mi)

East Fork White River 105.4 214.6 43 January 2005 2.6 21.6

Upper Wabash River 387.2 445.2 46 July 2003 1.3 18.3

Wildcat Creek 4.8 79.9 79 June 1958 0.9 10.4

1

High-water marks from Indiana Department of Natural Resources Historical Flood Profiles (written commun.).
Selected References 11

Transferability of Methods

The methods described in this report for determining 

potential locations for wetland restorations could be used 

by other States and regions to help administer important 

national programs to restore and protect wetlands. Because 

of the widespread availability of the data resources used 

for this project, including high-resolution digital elevation 

model data, historical flood profiles, and a national network 

of about 8,200 USGS streamgages, this project has great 

transferability potential.

Summary

The U.S. Geological Survey (USGS), in cooperation 

with the U.S. Department of Agriculture, Natural Resources 

Conservation Service, completed a study to estimate the 

potential wetland extents for 12 river reaches in Indiana and 

parts of Illinois and Ohio. The reaches were selected by the 

USGS and the Natural Resources Conservation Service as 

river basins that contain two or more USGS streamgages and 

are in areas where potential wetland information is needed 

for restoration under the Agricultural Conservation Easement 

Program.

Streamflow statistics were obtained through statistical analysis of daily mean discharges stored for USGS 

streamgages. The statistical value generated for this analysis 

is the annual highest 7-consecutive-day mean discharge with a 

2-year recurrence interval. This statistical value is referred to 

as the “7MQ2.” The 7MQ2 at a streamgage serves as a determination of the inundation flow at that location. For this study, 

the 7-consecutive-day mean discharge time-series data were 

analyzed using a log-Pearson Type-III distribution, as implemented in the USGS software package SWToolbox.

Water-surface elevations of the 7MQ2 flows were 

determined using the stage-discharge rating for each of the 

streamgages used in this study. Once the inundation flow was 

determined, the corresponding elevation of that flow was 

selected from the rating. The most recent rating or the rating 

used during the period of record of the streamgage was used. 

The validity of the elevations and the resulting water-surface 

profiles was checked using a visual comparison with Indiana 

Department of Natural Resources historical flood profiles at 

each stream reach.

Once the inundation elevations were estimated for 

the river reach, flood maps were developed in conjunction 

with digital elevation model data. A series of water-surface 

planes was created using a geographic information system 

application to represent the surface of inundation elevation that sloped in the downstream direction of flow. After 

the surface of the inundation zone was generated, a map 

representing the inundation zone was created by subtracting 

the digital elevation model from the surface of inundationelevation data.

The workflow for the 2012 pilot study for the mapping 

of wetland extent was reproduced programmatically using 

Python, an open-source, object-oriented programming language. Scripts named “Draw Transects” and “Delineate Wetlands” were written and configured as geoprocessing tools in 

an ArcGIS Python toolbox (.pyt). Development of the toolbox 

was in part motivated by a need to make the workflow more 

time efficient, but also to allow reproducibility of the results 

when using an identical set of parameters and to improve 

documentation of the process.

Wetland mapping is important for wetland inventory, 

regulation, management, protection, and restoration. The 

National Resources Conservation Service and its partners use 

inundation-zone verification for the Agricultural Conservation 

Easement Program. The emphasis of this program is to protect, 

restore, and enhance the functions and values of wetland ecosystems. Because data resources used for this project—including digital elevation model data, flood profiles, and a national 

network of about 8,200 USGS streamgages—are widespread, 

this project has great transferability potential to other States 

and regions across the country.

Selected References

Cowardin, L.M., Carter, V., Golet, F.C., and LaRoe, E.T., 

1979, Classification of wetlands and deepwater habitats of 

the United States: Washington, D.C., U.S. Department of 

the Interior, Fish and Wildlife Service, FWS/OBS–79/31, 

142 p., accessed June 2017 at https://www.fws.gov/wetlands/documents/classification-of-wetlands-and-deepwaterhabitats-of-the-united-states.pdf.

Dahl, T.E., 1990, Wetland losses in the United States 1780s to 

1980s: Washington, D.C., U.S. Department of the Interior, 

Fish and Wildlife Service, 13 p., accessed October 9, 2018, 

at https://www.fws.gov/wetlands/Documents/WetlandsLosses-in-the-United-States-1780s-to-1980s.pdf.

Fowler, K.K., Sperl, B.J., and Kim, M.H.B., 2019, Geospatial 

datasets related to wetland extent maps for 12 river reaches 

in Indiana: U.S. Geological Survey data release, https://doi.

org/10.5066/P9LGXDJ8.

Illinois Natural Resources Geospatial Data Clearinghouse, 

Illinois State Geological Survey, 2018, Illinois height modernization (ILHMP)—LiDAR data: Illinois State Geological 

Survey, Illinois Natural Resources Geospatial Data Clearinghouse, digital data, accessed September 2018 at http://

clearinghouse.isgs.illinois.edu/data/elevation/illinois-heightmodernization-ilhmp-lidar-data.

Indiana Department of Natural Resources, 1996, Indiana 

wetlands conservation plan: Indiana Department of Natural 

Resources, 75 p., accessed August 16, 2018, at http://www.

in.gov/dnr/fishwild/3350.htm.
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Kiang, J.E., Flynn, K.M., Zhai, T., Hummel, P., and Granato, 

G., 2018, SWToolbox—A surface-water tool-box for statistical analysis of streamflow time series: U.S. Geological 

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accessed May 2018 at https://doi.org/10.3133/tm4A11.

Kim, M.H., Ritz, C.T., and Arvin, D.V., 2012, Method for 

estimating potential wetland extent by utilizing streamflow 

statistics and flood-inundation mapping techniques—Pilot 

study for land along the Wabash River near Terre Haute, 

Indiana: U.S. Geological Survey Scientific Investigations 

Report 2012–5175, 15 p., 1 app., accessed June 2017 at 

https://pubs.usgs.gov/sir/2012/5175/.

Ohio Geographically Referenced Information Program, 2018; 

Ohio spatial data infrastructure—OSDI downloads: Ohio 

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data, accessed June 2017 at https://ogrip.oit.ohio.gov/ServicesData/GEOhioSpatialInformationPortal/OhioSpatialDataInfrastructure-Downloads.aspx.

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of streamflow: U.S. Geological Survey Water-Supply Paper 

2175, v. 1–2, 631 p., accessed May 2017 at https://pubs.

usgs.gov/wsp/wsp2175/.

Riggs, H.C., 1968, Frequency curves: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 4, 

chap. A2, 15 p., accessed August 2017 at https://pubs.usgs.

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characteristics of large reservoirs in the United States and 

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wps/portal/nrcs/detail/national/programs/easements/

acep/?cid=stelprdb1242695.

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about—Status and trends of wetlands in the conterminous 

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Publishing support provided by: 

Madison and Rolla Publishing Service Centers

For additional information concerning this publication, contact:

Director, Ohio-Kentucky-Indiana Water Science Center

U.S. Geological Survey

5957 Lakeside Boulevard

Indianapolis, IN 46278

(317) 290−3333

Or visit the Ohio-Kentucky-Indiana Water Science Center website at:

https://www.usgs.gov/centers/oki-water
Fowler and others—Estimating Potential Wetland Extent along Selected River Reaches in Indiana—Scientific Investigations Report 2019–5063

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20195063