U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2013–1157

Land Change in the Central Corn Belt Plains 

Ecoregion and Hydrologic Consequences in 

Developed Areas—1939–2000

Land Change in the Central Corn Belt Plains 

Ecoregion and Hydrologic Consequences in 

Developed Areas—1939–2000

By Krista Karstensen, David Shaver, Randal Alexander, Thomas Over, and 

David Soong

Open-File Report 2013–1157

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: 2013

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Suggested citation:

Karstensen, K.A., Shaver, D.K., Alexander, R.L, Over, T.M., and Soong, D., 2013, Land change in the Central Corn Belt 

Plains Ecoregion and hydrologic consequences in developed areas—1939–2000: U.S. Geological Survey Open-File 

Report 2013–1157, 21 p., http://pubs.usgs.gov/of/2013/1157/.
iii

Contents

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

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

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

Chicago Metropolitan Area.................................................................................................................3

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

Land-Cover Change Analysis..............................................................................................................4

Supporting Data ...................................................................................................................................5

Aerial Photographs......................................................................................................................5

Satellite Imagery..........................................................................................................................7

Image Process..............................................................................................................................7

Summary of Land Change in the Central Corn Belt Plains—1939–2000 ..............................................7

Ecoregional Summary .........................................................................................................................7

Land-Cover Sectoral Change .............................................................................................................9

Developed .....................................................................................................................................9

Agriculture ....................................................................................................................................9

Forest .............................................................................................................................................9

Grassland/shrubland...................................................................................................................9

Water .............................................................................................................................................9

Wetlands .....................................................................................................................................10

Mining..........................................................................................................................................10

Barren..........................................................................................................................................10

Mechanically disturbed............................................................................................................10

Net and Gross Change.......................................................................................................................11

Drivers and Consequences of Land-Cover Change ..............................................................................11

Historic Agricultural Land Change...................................................................................................11

Historic Developed Land Change.....................................................................................................12

Drivers and Consequences of Developed Land Change..............................................................12

Chicago.................................................................................................................................................12

Case Study: Urbanization Effects on Flood Flows in the Chicago Area..............................................12

Future Steps..................................................................................................................................................16

Methodological Way Ahead .............................................................................................................16

Conclusions...................................................................................................................................................18

References Cited..........................................................................................................................................18

Land-Cover Class Descriptions .................................................................................................................21
iv

Tables

1. Percentages of general land cover types for 1939, 1973, 1980, 1986, 1992, and 2000........7

2. Percentage of the ecoregion that experienced change and associated error .................9

3. Net change by interval in the Central Corn Belt Plains........................................................11

 4. Gross change by interval in the Central Corn Belt Plains....................................................12

Figures

1. Map showing 2001 Land cover in the Central Corn Belt Plains Ecoregion.........................2

2. Graph showing population trends for the Chicago metropolitan counties and the city 

of Chicago. Chicago metropolitan counties include Cook, DuPage, Kane, Kendall, Lake, 

McHenry, and Will..........................................................................................................................3

3. Maps showing land-cover change in sample block 26 throughout the study period A, 

1939; B, 1974; C, 1980; D, 1986; E, 1992; and F, 2000 .................................................................4

4. Aerial photographs showing substantial land change has occurred in sample 

block 26 near Rockford, Illinois. A, 2009 imagery from the National Agriculture 

Imagery Program; B, an aerial photograph of the same location in 1939. These 

images demonstrate an increase in impervious surface from road width, parking 

lots, and large buildings...............................................................................................................5

5. Maps showing housing density by decade in northeastern Illinois, 1940 to 2010 .............6

6. Map showing the one sample block in the Indiana portion of the ecoregion that was 

not included in the analysis ........................................................................................................8

7. Aerial photographs showing substantial land change has occurred in the Chicago, 

Illinois, metropolitan area located in the Central Corn Belt Plains Ecoregion. A, 2009 

imagery from the National Agriculture Imagery Program of Chicago O’Hare International Airport in 2000; B, An aerial photograph of the same location in 1939 ...................10

8. Maps showing A, Locations of U.S. Geological Survey streamgages measuring the 

143 watersheds in the Chicago region; B, Locations of U.S. Geological Survey 

streamgages measuring the 143 watersheds in the Chicago region.................................14

9. Histogram showing drainage areas of the 143 watersheds in the Chicago region.........16

10. Histogram showing number of streamflow-gaging stations with peak flow data 

during each water year in the study of 143 watersheds in the Chicago region...............16

11. Graphs showing comparison between theobald exurban/urban housing plus 

commercial-industrial-transportation land area and U.S. Geological Survey Land 

Cover Trends Project developed area for the 40 100-km2 sample blocks in Ecoregion 54 for 1939/40, 1970/73, 1980, 1990/92, and 2000 ........................................................17

12. Graph showing partial residuals of base-10 logarithms of peak flows adjusted for 

effects of precipitation as a function of urban fraction .......................................................18

13. Graph showing ratio of the estimated annual maximum peak streamflow in an urbanized 

watershed to that in a completely rural watershed derived from an analysis of 143 watersheds in the Chicago area...........................................................................................................18
iv

Tables

1. Percentages of general land cover types for 1939, 1973, 1980, 1986, 1992, and 2000........7

2. Percentage of the ecoregion that experienced change and associated error .................9

3. Net change by interval in the Central Corn Belt Plains........................................................11

 4. Gross change by interval in the Central Corn Belt Plains....................................................12

Figures

1. Map showing 2001 Land cover in the Central Corn Belt Plains Ecoregion.........................2

2. Graph showing population trends for the Chicago metropolitan counties and the city 

of Chicago. Chicago metropolitan counties include Cook, DuPage, Kane, Kendall, Lake, 

McHenry, and Will..........................................................................................................................3

3. Maps showing land-cover change in sample block 26 throughout the study period A, 

1939; B, 1974; C, 1980; D, 1986; E, 1992; and F, 2000 .................................................................4

4. Aerial photographs showing substantial land change has occurred in sample 

block 26 near Rockford, Illinois. A, 2009 imagery from the National Agriculture 

Imagery Program; B, an aerial photograph of the same location in 1939. These 

images demonstrate an increase in impervious surface from road width, parking 

lots, and large buildings...............................................................................................................5

5. Maps showing housing density by decade in northeastern Illinois, 1940 to 2010 .............6

6. Map showing the one sample block in the Indiana portion of the ecoregion that was 

not included in the analysis ........................................................................................................8

7. Aerial photographs showing substantial land change has occurred in the Chicago, 

Illinois, metropolitan area located in the Central Corn Belt Plains Ecoregion. A, 2009 

imagery from the National Agriculture Imagery Program of Chicago O’Hare International Airport in 2000; B, An aerial photograph of the same location in 1939 ...................10

8. Maps showing A, Locations of U.S. Geological Survey streamgages measuring the 

143 watersheds in the Chicago region; B, Locations of U.S. Geological Survey 

streamgages measuring the 143 watersheds in the Chicago region.................................14

9. Histogram showing drainage areas of the 143 watersheds in the Chicago region.........16

10. Histogram showing number of streamflow-gaging stations with peak flow data 

during each water year in the study of 143 watersheds in the Chicago region...............16

11. Graphs showing comparison between Theobald exurban/urban housing plus 

commercial-industrial-transportation land area and U.S. Geological Survey Land 

Cover Trends Project developed area for the 40 100-km2 sample blocks in Ecoregion 54 for 1939/40, 1970/73, 1980, 1990/92, and 2000 ........................................................17

12. Graph showing Partial residuals of base-10 logarithms of peak flows adjusted for 

effects of precipitation as a function of urban fraction .......................................................18

13. Graph showing ratio of the estimated annual maximum peak streamflow in an urbanized 

watershed to that in a completely rural watershed derived from an analysis of 143 watersheds in the Chicago area...........................................................................................................18
v

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

square mile (mi2

) 259.0 hectare (ha)

acre 0.4047 square hectometer (hm2

)

Flow rate

Cubic foot per second (ft3

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

Temperature can be converted to degrees Celsius (°C) or degrees Fahrenheit (°F) by the 

equations:

°C = 5/9 (°F - 32)

°F = 9/5 (°C) + 32

Vertical coordinate information is referenced to, as “North American Vertical Datum of 1988 

(NAVD 88).”

Horizontal coordinate information is referenced to as, “North American Datum of 1983 

(NAD 83).”
vi

Hydrologic Terms

The hydrologic definitions provided largely are from Langbein and Iseri (1960) and Perry 

(2005).

A

annual maximum peak streamflow The maximum instantaneous discharge value measured 

during a given water year at a streamflow-gaging station.

D

discharge Discharge is the volume of water that passes a given location within a given period 

of time. In its simplest concept, discharge means outflow; therefore, the use of this term is not 

restricted to course or location, and it can be applied to describe the flow of water from a pipe 

or a drainage basin.

drainage area The drainage area of a stream at a specified location is the area, measured in a 

horizontal plane, that is enclosed by a drainage divide.

drainage basin A part of the surface of the Earth where precipitation runs off into the drainage 

system, which consists of a surface stream or a body of impounded surface water together with 

all tributary surface streams and bodies of impounded surface water.

F

flood An overflow of water onto or an inundation of lands that are not normally covered by 

water, and causes or threatens damage.

P

peak streamflow The maximum instantaneous discharge of a stream or river at a given location, and usually occurs at or near the time of maximum stage.

R

runoff That part of the precipitation, snowmelt, or irrigation water that appears in surface 

streams, rivers, drains, or sewers.

S

streamflow The water discharge that occurs in a natural channel. Although the term “discharge” can be applied to the flow of a canal, the word “streamflow” uniquely describes the discharge in a surface stream course. The term “streamflow” is more general than runoff because 

streamflow may be applied to discharge whether or not it is affected by diversion or regulation.

streamflow-gaging station A site on a stream, lake, reservoir or other body of water where 

observations and hydrologic data are obtained. The U.S. Geological Survey measures stream 

discharge at streamflow-gaging stations. 

W

water year The continuous 12-month period from October 1 through September 30, and is 

designated by the year in which it ends. Thus, the year ending September 30, 1994, is called the 

“1994 water year.”
Abstract

This report emphasizes the importance of a multi-disciplinary understanding of how land use and land cover can 

affect regional hydrology by collaboratively investigating how 

increases in developed land area may affect stream discharge 

by evaluating

• Land-cover change from 1939 to 2000,

• Urban housing density data from 1940 to 2010, and 

• Changes in annual peak streamflow from water years 

1945 to 2009.

The results and methods crosscut two mission areas of 

the U.S. Geological Survey (Climate and Land Use, Water) 

and can be used to better assess developed land change and 

hydrologic consequences, which can be used to better assess 

future management and mitigation strategies. 

Introduction

The U. S. Geological Survey (USGS) Land Cover Trends 

Project investigates the rates, trends, causes, and consequences 

of contemporary U.S. land-use and land-cover change (Loveland and others, 2002). Through comparison of land cover in 

different time periods, the rates and types of changes can be 

determined in order to assess possible effects of land use on 

socioeconomic, biologic, geologic, and hydrologic systems 

(Loveland and others, 1999). 

Historical settlement patterns and contemporary driving forces, such as changes in population and technological 

advancements, are primary factors that create a complex 

pattern of land-cover change across the United States. Landchange analyses of the period 1973 to 2000 revealed the geographic and temporal variability of landscape change across a 

diverse national setting. This 27-year timeframe assessed four 

temporal periods: 1973 to 1980, 1980 to 1986, 1986 to 1992, 

and 1992 to 2000. General land-cover classes for these periods 

include water, developed, mechanically disturbed, mining, 

barren, forest, grassland/shrubland, agriculture, wetland, nonmechanically disturbed, and ice/snow. Land cover for these 

periods is interpreted from Landsat Multispectral Scanner, 

Thematic Mapper, and Enhanced Thematic Mapper Plus imagery to categorize land-cover change and evaluate trends using 

a modified Anderson Land Use Land Cover Classification 

System (Anderson and others, 1976) for image interpretation. 

These land-cover classes were selected because they complemented the objective of looking at land-use change with land 

cover serving as a surrogate for land use (Loveland and others, 

1999). 

Mapping for the four temporal periods within the 

84 Level III ecoregions was completed in March 2011. 

Results illustrate a complexity of landscape dynamics and 

temporally variable processes occurring across the national 

landscape that vary depending on the environmental setting 

and interacting change agents. As the project moves forward, 

teams will be developing an improved analytical framework 

for understanding human-environment dynamics (such as 

ecosystem function, biodiversity and habitat, and water quality and quantity) and will work to synthesize biophysical and 

land-use interactions to better assess the effects of land-use 

changes on environmental conditions and land management. 

Because of the great amount of geographic variability 

in land-cover change within and among ecoregions, a plan to 

assess changes with a single ecoregion was developed. The 

Central Corn Belt Plains was selected as the ecoregion to analyze because (1) the 1973 to 2000 interpretation, analysis, and 

statistical evaluation were complete; (2) the authors had participated in field analysis of the ecoregion; and (3) aerial photography was readily available to extend the land-cover analysis 

period back to 1939. This extended period of record provides 

researchers with more data to help understand the story of land 

change and associated consequences in the ecoregion.

In addition to these reasons, another motivation for 

selecting the Central Corn Belt Plains Ecoregion was the 

presence of the Chicago metropolitan area, which had experienced substantial change during the completed 1973 to 2000 

study period. In the Chicago metropolitan area, important 

Land Change in the Central Corn Belt Plains 

Ecoregion and Hydrologic Consequences in 

Developed Areas—1939–2000

By Krista Karstensen, David Shaver, Randal Alexander, Thomas Over, and David Soong
2 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

drivers of change included changes in population growth 

rates, socioeconomics, production and manufacturing, and 

increased development. The spatial growth of developed land 

in the ecoregion somewhat mirrored the image of the loss of 

agricultural land. In addition to affecting agricultural land, 

increases in developed land area also can affect water supply and natural hazards such as urban flooding. The research 

efforts described herein focus on the potential consequences 

of land-use changes in the Central Corn Belt Plains Ecoregion 

and how these consequences may manifest in regional hydrologic trends.

Study Area

 The Central Corn Belt Plains Ecoregion (Omernik, 

1987; U.S. Environmental Protection Agency, 1999) covers 

approximately 98,800 square kilometers (km2) [38,000 square 

miles (mi2)] in Illinois and Indiana, extending slightly into 

Wisconsin (fig. 1). Note that updated ecoregion boundaries 

are documented by the U.S. Environmental Protection Agency 

(2007) and were derived from Omernik (1987). These updates 

took place after the Land Cover Trends Project classification 

initiative was underway so analysis incorporates the boundaries reflected in Omernik (1987) and the U.S. Environmental 

Protection Agency (1999). 

Figure 1. 2001 Land cover in the Central Corn Belt Plains Ecoregion.

Sample 

block 26

^

92° 91° 90° 89° 88° 87° 86°

43°

42°

41°

40°

39°

38°

37°

ILLINOIS

MISSOURI

IOWA

INDIANA

KENTUCKY

Chicago

Central Corn Belt Plains Ecoregion

WISCONSIN Lake Michigan

MICHIGAN

0 60 120 MILES

0 60 120 KILOMETERS

Base from National Atlas of the United States, 2006 200-meter resolution 

Albers projection

Central Corn Belt Plains 

 Ecoregion sample

Land use from National Land Cover Database, 2001

EXPLANATION

Land cover (within Central 

Corn Belt Plains Ecoregion)

Water

Developed

Mechanically disturbed

Mining

Forest

Grassland/shrubland

Agriculture

Wetland
Study Area 3

Elevations in the ecoregion range from approximately 

122 meters (400 feet) in the south to about 305 meters 

(1,000 feet) on a few hills in the north (Omernik and Gallant, 

1988). The average length of the frost-free period varies from 

160 to about 190 days (Wiken and others, 2011) with most 

of the annual precipitation falling during the growing season 

and averaging from 813 millimeters (mm) (32 inches) to 

1,117 mm (44 inches) annually (Omernik and Gallant, 1988). 

The soils in the ecoregion are generally dark and fertile which 

help support the extensive cropland and livestock farming vital 

to the ecoregion (Woods and others, 2006).

The native landscape was composed of extensive prairie 

communities intermixed with oak-hickory forests; however, 

nearly all of the natural vegetation has been replaced by agriculture (Wiken and others, 2011), and farms are now extensive 

and primarily produce corn and soybeans. Livestock farming 

in the Central Corn Belt Plains is not as common as in neighboring ecoregions, but does include hogs, cattle, sheep, and 

poultry (Woods and others, 2006). Agriculture in the ecoregion 

has affected stream chemistry, turbidity, and habitat (Woods 

and others, 2006).

The Central Corn Belt Plains has a relatively high population, especially adjacent to Lake Michigan where nearly all 

of the natural vegetation has been replaced by urban development (Woods and others, 2006). Chicago is the most populated 

city in the ecoregion with a 2000 population of 2,896,016. 

But there are many small- to medium-sized cities scattered 

throughout the ecoregion including (2000 population) Rockford, Illinois (150,115); the Chicago suburbs of Aurora, Ill.

(142,115) and Naperville, Ill. (128,358); Peoria, Ill. (112,892); 

Springfield, Ill. (111,454); Gary, Indiana (102,746); and Decatur, Ill. (81, 860) (U.S. Census Bureau, 2000).

Chicago Metropolitan Area

Suburban expansion began in the period following World 

War II (McGrath, 2001). The city of Chicago showed noticeable upward population swings in 1920 and 1950 (Buchanan 

and Acevedo, 2010) before beginning a slight but consistent 

decline in the 1960s (fig. 2); however, the decline in population did not slow the urban development: from 1950 to 2000, 

the urbanized land area of Chicago grew from 1,834 km2 to 

4,330 km2 (McGrath, 2001). 

Historically, the city also underwent substantial infrastructure changes to accommodate emerging modes of 

transportation during the transition from canals to railroads 

(1850s), at the turn of the century (electric railroads), and 

when the automobile began to dominate (1940s) (Buchanan 

and Acevedo, 2010). As demonstrated in the statistics later in 

the report, much of the development occurred at the expense 

of agricultural land (figs. 3 and 4). According to the Northeastern Illinois Planning Commission, the explosion of land consumption continued dramatically between 1970 and 1990 with 

a 40-percent increase in developed land area in the region, 

whereas the region’s population increased by only 4 percent 

(Mariner, 2005; Platt, 2004). In a study by Radeloff and others (2005), housing growth varied by ecoregions in the upper 

Midwest. The study indicates that the highest absolute growth 

0

1

2

3

4

5

6

7

8

9

1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Population, in millions

Year

Metropolitan counties

City of Chicago

EXPLANATION

Figure 2. Population trends for the Chicago metropolitan counties and the city of Chicago. 

Chicago metropolitan counties include Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will 

(University of Virginia, 2007; McClendon, 2012).
4 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

between 1940 and 2000 occurred in the Chicago, Ill./Gary, 

Ind./Kenosha, Wisconsin and Milwaukee, Wis./Racine, Wis. 

areas, and documents that suburban housing growth was especially high post World War II. A historical view of this growth 

and development pattern in the Chicago area is provided by 

the Census-based housing density product of Theobald (2005; 

fig. 5) and further illustrates that the rate of development 

increased despite minimal population growth. Whether urban 

population and the corresponding land change is rapid or slow, 

it can be difficult to measure actual changes in the developed 

land because it is a collection of areas under various ownerships (Platt, 2004) and surfaces (Xian and others, 2006).

Methods

Land-Cover Change Analysis

The methodology of the Land Cover Trends Project is 

defined in part by multitemporal analysis of Landsat satellite 

data and a stratified probability-based sampling of 84 Level 

III ecoregions (Omernik, 1987) with more than 2,700 sample 

block locations of 100 km2 and 400 km2. The rates of landcover change are estimated using a stratified, random sampling 

(Stehman and others, 2005) of 10-kilometer (km) by 10-km 

blocks allocated within each ecoregion. For each sample 

block, the satellite images are used to interpret land-cover 

change for the five time periods. Additionally, historical aerial 

photographs from similar timeframes and other ancillary data 

Lake Michigan

EXPLANATION

Land cover

A B C

D E F

Water

Developed

Mechanically disturbed

Mining

Forest

Grassland/shrubland

Agriculture

Wetland

Figure 3. Land-cover change in sample block 26 (fig. 1) throughout the study period A, 1939; B, 1974; C, 1980; D, 1986; 

E, 1992; and F, 2000.
Methods 5

such as census statistics and published literature are used. The 

sample block data are then incorporated into statistical analyses to generate an overall land change matrix for the ecoregion. These change statistics are applicable for different levels 

of scale, including total change for the individual sample 

blocks and change estimates for the entire ecoregion. At each 

level of scale, corresponding sets of land-cover change statistics are produced. For example, the scalar statistics indicate 

the spatial extent and type of change per cover type with time. 

The sampling was designed to enable a statistically robust 

estimate of land-cover change within each ecoregion and additional frameworks, such as states and landscape-scale watersheds, although variability of the estimates of other geographic 

frameworks may change. 

Field verification data for the sample blocks included 

ground surveys for training and validation of image classifications (Loveland and others, 2002). The field measurements 

and observations made in each ecoregion also allowed 

additional observations of the character and condition of the 

landscape for improving interpretation, ground truthing of the 

Landsat imagery, and to provide evidence for potential driving 

forces of land change in the ecoregion. 

Supporting Data 

Aerial Photographs

Historic aerial photographs produced by the U.S. Department of Agriculture (known then as the Agricultural Stabilization and Conservation Service) were used to classify land 

cover for 1939. The aerial photographs for the sample blocks 

located in Illinois were downloaded from the Illinois Natural 

Resources Geospatial Data Clearinghouse at the University 

of Illinois at Urbana-Champaign (University of Illinois at 

Figure 4. Substantial land change has occurred in sample block 26 near Rockford, Illinois. A, 2009 imagery from the 

National Agriculture Imagery Program; B, an aerial photograph of the same location in 1939. These images demonstrate an 

increase in impervious surface from road width, parking lots, and large buildings. 

A B
6 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1940

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1970

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

2000

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1950

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1980

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

2010

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1960

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

1990

0 25 50 MILES

0 25 50 KILOMETERS

EXPLANATION

Housing density class number 

 and description

0–Undeveloped

1–Greater than 80 acres per unit

2–50 to 80 acres per unit

3–40 to 50 acres per unit

4–30 to 40 acres per unit

5–20 to 30 acres per unit

6–10 to 20 acres per unit

7–1.7 to 10 acres per unit

8–0.6 to 1.7 acres per unit

9–Less than 0.6 acres per unit

10–Commercial/industrial

 /transportation

Undefined

N

Figure 5. Housing density by decade in northeastern Illinois, 1940 to 2010, based on data from Theobald (2005).
Summary of Land Change in the Central Corn Belt Plains—1939–2000 7

Champaign-Urbana, 2012). The aerial photographs for the 

sample blocks located in Indiana were acquired from the 

Indiana Geological Survey (Indiana Geological Survey, 2011). 

Aerial photographs were not acquired by the research team for 

sample block 561, in the Indiana part of the ecoregion (fig. 6), 

so it was not included in the analysis. The land-cover change 

in the omitted block was minimal enough to not play a significant role in the overall statistical analysis as the overall change 

in the block from 1973 to 2000 was relatively low. After the 

data were acquired, the target scenes from the photographs 

were georeferenced and the rectified image was clipped as 

close to camera fiducials as possible. The preliminary georeferencing was then further refined through autocorrelation 

processes and mosaicing techniques.

Satellite Imagery

Land-cover analysis from 1973 to 2000 for the Central 

Corn Belt Plains was completed by the USGS Land Cover 

Trends Project in 2010. The land-cover classification data 

interpreted from Landsat Multispectral Scanner, Thematic 

Mapper, and Enhanced Thematic Mapper Plus satellite images 

for each sample block were used in the present study.

Image Process

In order to supplement the contemporary (1973 to 2000) 

land-cover analysis, land cover also was interpreted from 1939 

aerial photographs. The mosaiced photograph image for each 

sample block was classified for land cover following the same 

protocol and methods used by the USGS Land Cover Trends 

Project for the 1973 to 2000 analysis (Griffith and others, 

2003; Stehman and others, 2005; and Stehman and others, 

2003). A statistical land-cover change product that demonstrates the rates and types of change from 1939 to 2000 was 

completed following the same standards and equations used 

in the Land Cover Trends Project (Griffith and others, 2003, 

Stehman and others 2005, and Stehman and others 2003). 

Importantly, interpretation dates from 1973 to 2000 generally 

are 7 years and the interval between 1939 and 1973 is much 

larger and accounts for 34 years. 

Summary of Land Change in the Central 

Corn Belt Plains—1939–2000 

Ecoregional Summary 

The percent area of all land-cover types is shown in table 

1 for six dates from 1939 to 2000. Again, note that the statistical analysis was calculated with no data reported for one low 

changing block in the ecoregion. The leading land covers in 

the ecoregion were agriculture, forest, and developed. Combined, these land-cover classes comprised an estimated 92 percent of the region’s land area in 1939 and 96 percent in 2000. 

By 2000, agriculture had decreased by approximately 5 percent, whereas forest land increased by approximately 2 percent 

and developed land increased by approximately 7 percent. The 

principal land change in the ecoregion revolves around loss of 

farmland resulting from conversions to developed lands.

When normalized to account for varying lengths of time 

intervals, the overall spatial change for the region—the percentage of land that changed from one land cover to another—

was 19.9 percent (table 2). This statistic does not account for 

the fact that an intermediate date between 1939 and 1973 was 

not analyzed for image interpretation or land-cover change 

classification. Approximately 18.3 percent of the land area 

converted only once, whereas 1.4 percent and 0.1 percent transitioned from one land cover to another two and three times, 

Table 1. Percentages of general land cover types for 1939, 1973, 1980, 1986, 1992, and 2000. 

[-, minus] Year or change 

interval

Water

(in percent)

Developed

(in percent)

Mechanically 

disturbed

(in percent)

Mining

(in percent)

Barren

(in percent)

Forest

(in percent)

Grassland/ 

shrubland

(in percent)

Agriculture

(in percent)

Wetland

(in percent)

Nonmechanically disturbed

(in percent)

Snow/ice

(in percent)

1939 1.23 4.54 0 0.03 0.01 7.30 3.44 80.20 0.76 0 0

1973 1.63 9.19 0.02 0.16 0 9.50 0.73 77.42 1.37 0 0

1980 1.56 9.58 0 0.18 0 9.40 0.74 77.09 1.44 0 0

1986 1.53 9.95 0.01 0.21 0 9.34 0.67 76.80 1.48 0 0

1992 1.57 10.47 0.01 0.22 0 9.33 0.62 76.33 1.45 0 0

2000 1.58 11.56 0.02 0.27 0 9.29 0.57 75.27 1.45 0 0

1973–2000 

Change

-0.05 2.38 0 0.11 0 -0.21 -0.16 -2.15 0.08 0 0

1939–2000 

Change

0.35 7.02 0.02 0.24 -0.01 1.99 -2.87 -4.94 0.69 0 0
8 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

^

Chicago

91° 90° 89° 88° 87°

43°

42°

41°

40°

39°

38°

37°

EXPLANATION

0 50 100 MILES

0 50 100 KILOMETERS

Base from National Atlas of the United States, 2006

200-Meter Resolution, Albers projection

ILLINOIS

MISSOURI

INDIANA

KENTUCKY

Central Corn Belt Plains Ecoregion

Lake Michigan

WISCONSIN

Central Corn Belt Plains Ecoregion

Central Corn Belt Plains Ecoregion sample blocks

IOWA

Figure 6. Map showing the one sample block in the Indiana portion of the ecoregion that was not included in the analysis. 
Summary of Land Change in the Central Corn Belt Plains—1939–2000 9

respectively. No amount of land in the sample blocks underwent more than three changes in land cover. The significant 

amount of land that underwent change only one time likely is 

due to the unidirectional changes from agriculture to developed lands. 

Land-Cover Sectoral Change 

Developed

In 1939, developed lands accounted for approximately 

4.5 percent of the region (table 1). By 2000, an estimated 

11.6 percent of the region was developed (table 1). A significant percentage increase occurred between 1939 and 1973 as 

well as between 1992 and 2000, the latter being a noted time 

of substantial residential expansion (von Hoffmann, 1999). 

Most of the newly developed lands in each interval were the 

result of conversions from farmland (fig. 7). Some gains to the 

developed class resulted from forest clearing, but to a much 

lesser extent than agricultural land. Developed land change 

nearly always is a unidirectional change with all of the land 

remaining in a built-up or developed state, which can have 

serious implications on hydrologic and ecological systems 

(U.S. Geological Survey, 2012). 

Agriculture

Agriculture was the leading cover class in all of the time 

intervals; agricultural land use played, and continues to play, 

a leading role in shaping the Central Corn Belt Plains Ecoregion physical and socioeconomic landscape. When land is 

converted to agricultural use, the hydrologic processes of the 

natural landscape are modified toward optimizing agricultural 

production (U.S. Geological Survey, 2010). Often, these modifications have unintended environmental effects, including 

changes in water quantity and water quality (U.S. Geological 

Survey, 2010). In 2000, agricultural land accounted for 

75.3 percent of the ecoregion (table 1). The cover class primarily was being lost to developed land from 1939 to 2000, 

with a small percentage of the region’s agricultural land 

being converted to grassland/shrubland. The primary gain in 

agricultural land cover in the region occurred during the first 

three time intervals and came from forests being cleared for 

agricultural expansion. 

Forest

In the early 19th century, scattered areas of forest were 

documented on level uplands, and river valleys and moraines 

mostly were forested (Woods and others, 2006). The percentage of forest cover in 1939 (7.3 percent) may reflect the early 

land use patterns associated with the native vegetation gradually being replaced by agricultural crops (U.S. Environmental 

Protection Agency, 2010). After a net increase of 2.2 percent 

between 1939 and 1973 (table 3), the forest land-cover class 

remained relatively stable in the ecoregion declining from 

9.5 percent of the ecoregion in 1973 to 9.29 percent in 2000 

(table 1). 

Grassland/shrubland

Level uplands in the ecoregion were dominated by tallgrass prairie in the early 19th century, and at the time of settlement no other Illinois Level III ecoregion had as much prairie 

as the Central Corn Belt Plains (Woods and others, 2006). 

Grassland/shrubland accounted for approximately 0.57 percent 

of the land cover of the Central Corn Belt Plains Ecoregion 

in 2000 and during the time period lost approximately 

2.87 percent of land area (table 1). Although the Conservation 

Reserve Program may have played a more substantial role in 

grassland/shrubland land-cover conversions in neighboring 

ecoregions, in the Central Corn Belt Plains, nearly all of the 

original prairies have been replaced by agriculture (Woods and 

others, 2006).

Water

The water cover class comprised 1.58 percent of the 

ecoregion in 2000 (table 1). Overall, this cover class was 

relatively stable, having only a slight increase (0.35 percent) in 

regional composition during the study period. 

Table 2. Percentage of the ecoregion that experienced change and associated error.

[+/-, plus or minus]

Number of 

changes

Percent of 

ecoregion 

(in percent)

85 percent confidence interval +/-

(in percent) 

Lower bound 

(in percent)

Upper bound 

(in percent)

Standard error

 (in percent)

Relative error 

(in percent)

All change 19.9 4.8 15.1 24.6 3.2 16.3

1 18.3 4.1 14.2 22.4 2.8 15.4

2 1.4 0.8 0.6 2.2 0.5 37.9

3 0.1 0 0.1 0.1 0 28.7

4 0 0 0 0 0 59.7

5 0 0 0 0 0 0
10 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

Wetlands

Changes in the wetlands cover class were not prevalent 

in the ecoregion during the study period, comprising 0.76 percent in 1939 and increasing to 1.45 percent in 2000 (table 1). 

Fluctuations in wetland principally came from the water cover 

class and vice versa, and likely are due to interannual weather 

fluctuations. 

Mining

Mining activities accounted for only 0.03 percent of the 

ecoregion at the beginning of the study period and gradually 

increased to 0.27 percent in 2000 (table 1). This increase may 

be most closely related to the increased urbanization the ecoregion experienced. 

Barren

Barren land made up the smallest detectable land-cover 

compositions in the ecoregion during the entire study period, 

accounting for a mere 0.01 percent of the region in 1939 and 

was not present in any other time interval. 

Mechanically disturbed

Regionally, there was no significant gain or loss of 

mechanically disturbed land during the study period, ranging 

from 0.0 percent to 0.02 percent in any time period.

The nonmechanically disturbed and snow/ice classes 

were not classified in the Central Corn Belt Plains from 1939 

to 2000, as these classes were either 1) not present, or 2) 

below the minimum mapping unit of 60 meters.

A B

Figure 7. Substantial land change has occurred in the Chicago, Illinois, metropolitan area located in the Central Corn Belt 

Plains Ecoregion. A, 2009 imagery from the National Agriculture Imagery Program of Chicago O’Hare International Airport in 

2000; B, An aerial photograph of the same location in 1939. 
Drivers and Consequences of Land-Cover Change 11

Net and Gross Change

To understand land-cover dynamics, it is important to 

understand gross and net change in the Central Corn Belt 

Plains. Gross change is the total amount of a given land cover 

changed, and net change is the aggregate of gains and losses 

affecting that category. If all land change occurred only once 

on the same area, then net and gross change would be the 

same (Roger Auch, Steven Kambly, and Krista Karstensen, 

U.S. Geological Survey, written commun., 2012); however, 

the nature of the statistics herein take into account that often, 

a number of different types of land change tend to change 

more than once on the same area during the study period. 

For example, an agricultural field may slowly return to forest 

or grassland/shrubland depending on changes in land use, 

management, or both. The differences between gross and net 

change in a land sector where most of the change is unidirectional, such as the gains in developed land seen in the Central 

Corn Belt Plains, tend to be small (tables 3 and 4). The differences between gross and net change amounts are large in some 

sectors where cyclic or multiple changes affect the status of 

that land cover, such as forest in that particular region (Roger 

Auch, Steven Kambly, and Krista Karstensen, U.S. Geological 

Survey, written commun., 2012). 

Drivers and Consequences of LandCover Change 

A variety of land change was observed during georegistration of the 1939 aerial photographs for the Central Corn 

Belt Ecoregion including historic agricultural practices, urbanization, and transitions in land use. Although the discussion 

herein focuses on observations, drivers, and consequences of 

land change from 1939 to 1973, a full discussion of contemporary land change (1973 to 2000) also is available (Daniel 

Sorenson, U.S. Geological Survey, written commun., 2011).

Historic Agricultural Land Change

The evolution of the agricultural land-use sector has 

included changes in both farming practices and equipment. 

This transformation partly was due to the introduction of 

hybrid seed corn in 1933 (Hart, 1986). The change in corn 

yields that followed increased after World War II as farmers 

were able to double and even triple their yields (Hart, 1986). 

Moreover, from 1939 to 1968, soybean and wheat yields in 

the State of Illinois noticeably increased(Odell and Oschwald, 

1970). While the improved crop varieties boasted increased 

yields, they also required the use of a variety of agricultural 

fertilizers (specifically, limestone, nitrogen, phosphorus, and 

potassium) (Hart, 1986; Odell and Oschwald, 1970), which 

contributed greatly to the water-quality concerns that continue 

to be common in the ecoregion (U.S. Geological Survey, 

2012; Warner, 1998; Groschen and others, 2000). Although 

use of fertilizers, adapted varieties of crops, improved tillage 

practices, timeliness of operations, more efficient management, and technology-improved crop production in the region 

prompted the size of farms to increase (Hart, 1986), farm 

numbers (Odell and Oschwald, 1970; U.S. Department of 

Agriculture, 1964; U.S. Department of Commerce Bureau of 

the Census, 1942) and total farm area were decreasing (Hart, 

1986). This general decline in the number of farms and total 

farm area also may be exhibited in the statistics of this study 

as the agricultural land-cover class declined between 1939 

and 1973. These changes also may reflect the decline of small 

family farms and the increase in agribusiness in the rural counties where farm land area did not decline drastically, as well 

as illustrating agricultural land being developed in the more 

populated counties where both farm numbers and amount of 

land in farms declined more noticeably.

Agricultural land change is of special interest to this 

study because of the measurable amount being lost to other 

land-cover classes, most notably developed. This conversion of agricultural to developed land has taken place during 

a time of low population growth, as previously mentioned. 

Table 3. Net change by interval in the Central Corn Belt Plains.

[-, minus] Change interval

Water

(in percent)

Developed

(in percent)

Mechanically 

disturbed

(in percent)

Mining

(in percent)

Barren

(in percent)

Forest

(in percent)

Grassland/

Shrubland

(in percent)

Agriculture

(in percent)

Wetland

(in percent)

Nonmechanically disturbed

(in percent)

Snow/ice

(in percent)

1939 to 1973 0.4 4.6 0 0.1 0 2.2 -2.7 -2.8 0.6 0 0

1973 to 1980 -0.1 0.4 0 0 0 -0.1 0 -0.3 0.1 0 0

1980 to 1986 0 0.4 0 0 0 -0.1 -0.1 -0.3 0 0 0

1986 to 1992 0 0.5 0 0 0 0 -0.1 -0.5 0 0 0

1992 to 2000 0 1.1 0 0 0 0 0 -1.1 0 0 0
12 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

For example, between 1970 and 1980, net migration from the 

State of Illinois amounted to 375,000 people, yet agricultural 

to developed land conversion accelerated during that time 

(Dovring and others, 1982.)

Historic Developed Land Change

The principal story of land change in the Central Corn 

Belt Plains between 1939 and 2000 was the increase of 

developed land at the expense of agriculture. As previously 

mentioned, one specific driver of this change was the increase 

in population during the 61-year study period. The Chicago 

metropolitan region has grown dramatically since Chicago’s 

incorporation in 1830 (Buchanan and Acevedo, 2010; Auch 

and others, 2004). Areas in the ecoregion that would be classified as developed in all time periods had an increase in urban 

density and impervious surface. Structures such as airports, 

shopping malls, commercial buildings, subdivisions, and 

schools dramatically increased impervious surface area due 

to increases in road widths and numbers and sizes of parking 

lots. 

Drivers and Consequences of Developed Land 

Change

The land change trend of agricultural land declining as 

the amount of developed land increased is common during all 

time periods between 1939 and 2000. Often, rates of developed land change have socioeconomic underpinnings; for 

example, early development was affected by the events such 

as the Great Depression and World War II. Later in the study 

period, between 1964 and 1975, general decentralization of 

Chicago was occurring. A study conducted by Dovring and 

others (1982) concluded that factors aside from population 

pressure contributing to land conversion to developed uses in 

the Chicago area include automobile transportation and the 

method of financing highways, house financing, tax policies 

affecting capital gains, and public utility pricing policies. 

Chicago

The 1930s were a decade of growth for Chicago. The 

city’s population had grown from approximately 2,700,000 in 

1920 to 3,400,000 in 1930 (McClendon, 2012). The population expansion coincided with an increase in development 

including thousands of new bungalows encircling the city, 

however, the Great Depression slowed growth and development in the 1940s (McClendon, 2012). A post World War II 

building boom in the 1950s once again promoted growth and 

filled in the city and the first ring of suburbs with new houses, 

and increasing auto ownership increased development away 

from public transit lines (McClendon, 2012). This postwar era 

also was when expressways were beginning to be constructed. 

The increased preference for owner-occupied single-family 

houses (Mariner, 2004) and the Federal Highway Act of 1956 

(Auch and others, 2006) may have helped to drive suburban 

development. In its Comprehensive General Plan, adopted in 

1968, the Northeastern Illinois Planning Commission (NIPC) 

called for concentrating new development largely along the 

radial commuter lines focused on the Chicago Loop, and for 

preserving wedges of open space and low-density development between the radial corridors (Mariner, 2004). The open 

space and low-density developed areas are two components 

integral to dissecting the developed land-cover class in order 

to investigate the amount of historical impervious surface area 

and its effects on regional hydrology. 

Case Study: Urbanization Effects on 

Flood Flows in the Chicago Area

To address the lack of valuable data on historical imperviousness and other measures of urbanization, USGS researchers are working to characterize the historical process of urbanization in the Central Corn Belt Plains to determine the effect 

of urbanization on peak streamflows, enabling the adjustment 

of historic peak flow records to the current level of urban 

development. These adjusted records can be the basis of more 

Table 4. Gross change by interval in the Central Corn Belt Plains.

[, percent; -, minus] Change interval

Water

(in percent)

Developed

(in percent)

Mechanically 

disturbed

(in percent)

Mining

(in percent)

Barren

(in percent)

Forest

(in percent)

Grassland/

Shrubland

(in percent)

Agriculture

(in percent)

Wetland

(in percent)

Nonmechanically 

disturbed

(in percent)

Snow/ice

(in percent)

1939 to 1973 0.8 5.5 0 0.2 0 7.8 4.1 12.1 1.5 0 0

1973 to 1980 0.1 0.4 0 0 0 0.2 0.1 0.5 0.1 0 0

1980 to 1986 0.1 0.4 0 0 0 0.2 0.2 0.5 0.1 0 0

1986 to 1992 0.1 0.5 0 0 0 0.1 0.2 0.6 0.1 0 0

1992 to 2000 0.1 1.1 0 0.1 0 0.1 0.1 1.1 0 0 0
Case Study: Urbanization Effects on Flood Flows in the Chicago Area 13

accurate and relevant estimates of the expected frequency of 

peak flows of given magnitudes.

Developed land change can affect stream discharge by 

modifying rates and amounts of runoff from precipitation 

events. In the more agricultural areas in the ecoregion, and 

areas such as forests and grasslands, rainfall is more likely 

to be collected and stored on vegetation, in the soil, or in 

wetlands; however, in developed areas such as the Chicago 

metropolitan area, much of the land surface is covered by 

impervious surfaces that limit storage capabilities and capacities, and drainage generally is enhanced with infrastructure 

such as curb-and-gutter streets and storm sewers. With less 

storage capacity for water in urban basins and more rapid 

drainage, urban streams rise more quickly during storms and 

have higher peak flows than do rural streams, and the total 

volume of water discharged during a flood tends to be larger in 

urban streams than rural streams (Konrad, 2003). 

Although the impervious surface area of a watershed 

alone does not determine the hydrologic and other effects of 

urbanization on streams (Falcone and others, 2007; Sauer and 

others, 1983), it is the most direct parameter for analyzing and 

predicting the effects of changes in land cover associated with 

urbanization on characteristics of streamflow including peak 

flows (for example, Jacobson, 2011; Lee and Heaney, 2003; 

Shuster and others, 2005) and water quality and biology (Falcone and others, 2007), particularly when the fraction of the 

total impervious area that is directly connected1

 to the drainage 

system can be determined. Although measures of imperviousness at one time or over a limited (usually recent) time span 

are becoming available [for example, the National Land Cover 

Database, which includes estimates of imperviousness for 

2001 and 2006 (Xian and others, 2011)], these cannot be used 

in assessing stream effects of urbanization over the multidecadal time scales usually associated with the urbanization 

of a given watershed. Because of the difficulty of obtaining 

historical data for a direct measure of imperviousness, many 

hydrologic studies have used surrogates, such as population 

density or housing density, to indirectly account for the effect 

of impervious area (for example, Moglen and Shivers, 2006), 

despite the uncertainties in relating land use or other surrogates to impervious areas (Ackerman and Stein, 2008; Alley 

and Veenhuis, 1983).

To illustrate the effect of increases in urbanization on 

hydrology in this region, a summary of preliminary results of 

a longitudinal study of the dependence of annual maximum 

peak streamflow2

 on changes in urbanization (Thomas Over 

and David Soong, U.S. Geological Survey, written commun., 2012) is presented. The peak flow data used are from 

water years 1945 to 2009 and were measured at 143 USGS 

streamflow-gaging stations in the Chicago metropolitan in the 

northeastern part of the Central Corn Belt Plains Ecoregion 

(fig. 8). The streamflow-gaging stations measure watersheds 

with drainage areas between 0.03 and 200 mi2

 (0.08 km2 and 

518 km2 ) (fig. 9) and have record lengths of at least 10 years. 

A histogram showing the number of streamflow-gaging stations reporting during each water year between 1945 and 2009 

is shown in figure 10. The U.S. Census-based housing density 

product developed by Theobald (2005) (fig. 5) was used to 

quantify the process of urbanization during the study period 

because aerial photography/Landsat-based land-use estimates 

from the Land Cover Trends Project covering these watersheds 

were not available. Theobald (2005) estimates of urbanization, 

computed as the sum of the three densest classes of housing 

(all housing lots 10 acres (4 ha) or smaller in size) plus the 

commercial-industrial-transportation land-use class (that is, 

classes 7–10), were validated against the Land Cover Trends 

Project data by comparing them over the Land Cover Trends 

sample blocks in the Central Corn Belt Plains Ecoregion (fig. 

11). It is evident that on average, the values agree quite well.

By a regression analysis using a panel linear model with 

fixed station effects (Kleiber and Zeileis, 2008, section 3.6), it 

was determined that the base-10 logarithms of annual maximum peak flows from the 143 streamflow-gaging stations in 

the study increase with the urbanized watershed fraction with 

a coefficient of about 0.51 (fig. 12), after taking into account 

changes in precipitation by including a precipitation term in 

the regression model. The mathematical expression of the 

model is:

log10Qi(t) =b0i + b1Ui(t) + b2Pi(t) (1)

where 

Qi(t) is annual maximum peak flow in cubic feet 

per second at station i during year t, 

Ui (t) is urbanization at station i during year t (nondimensional fraction ranging from 0 to 1), 

Pi(t) is the precipitation in inches associated with , 

b0i is the intercept (fixed effect) for station 

i, 

and the regression coefficients are b1= 0.5117 

± 0.0403 for urbanization and b2 = 0.0846 

± 0.0035 for precipitation. 

The value of the urbanization coefficient implies, for 

example, that if a watershed increases from zero urbanization 

(U′ = 0) to completely urbanized (U′′ = 1), one would expect 

a peak flow increase of Q(U′′)/Q(U′) = 10b1(U′′ – U′) = 3.249

times (that is, a 225-percent increase), whereas a 10-percent 

increase in urbanization (U′′ = U′ + 0.1) implies an increase of 

Q(U′′)/Q(U′) = 10b1(U′′ – U′) = 100.5117(0.1) = 1.125 in the peak flows, 

or a 12.5-percent increase. The complete range of urbanization effects on a watershed that starts out at zero urbanization, 

according to these results, is shown in figure 13.

1

The directly connected (or “effective”) impervious area is that part of the 

impervious area that drains directly to the drainage system of the watershed, 

such as the storm sewers and street gutters. This includes areas that are graded 

toward sewer inlets and street gutters such as streets, driveways, and parking 

lots. Downspouts from roofs may or may not be directly connected; they are 

not if they drain onto a pervious surface such as a lawn.

2

The annual maximum peak streamflow data measured by the USGS are 

available at http://nwis.waterdata.usgs.gov/usa/nwis/peak (U.S. Geological 

Survey, 2010), and the data used in Thomas Over and David Soong (U.S. 

Geological Survey, written commun, 2012) were obtained from this Web site.
14 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

Figure 8. A, Locations of U.S. Geological Survey (USGS) streamgages measuring the 143 watersheds in the Chicago region 

(Thomas Over and David Soong, U.S. Geological Survey, written commun., 2012); B, Locations of U.S. Geological Survey 

(USGS) streamgages measuring the 143 watersheds in the Chicago region (Thomas Over and David Soong, U.S. Geological 

Survey, written commun., 2012).

0 5 10 20 30 40 MILES 0

0 5 10 20 30 40 KILOMETERS 0

Cook

Lake

Will Lake

La Salle

Racine

Iroquois

Kane

Livingston

Kenosha

Rock

De Kalb

Jasper

McHenry

Kankakee

Porter

Walworth

Grundy

Lee

Newton

Boone

Ford

Du Page

McLean

Kendall

Benton

Ogle

Milwaukee

White

Woodford

Jefferson Waukesha Dane

Winnebago

89° 88° 87°

42°

41°

Lake Michigan

Illinois

River

River

Des

River

Fox

River

Plaines

Kishwaukee R.

Kankakee

River

Iroquois River

Vermilion

Little Calumet

River

WISCONSIN

ILLINOIS

ILLINOIS

INDIANA

Base from U.S. Geological Survey 1:24,000-scale

and 1:100,000-scale digital data. Watershed

Boundary Dataset from Natural Resources

Conservation Service.

ILLINOIS

WISCONSIN

INDIANA

Map area

5549900

5549000

5548150

5547755

5545300

5527950 5527900

5527840 5438390

5438300

5438283

5438250 5437950

5527800

5527870

5555775

5555400

5551930

5551900

5551800

5551700

5551675

5551650

5551200

5551050

5550300

5548280

5541750

5539000

5527050

5526500

5523500

5523000

5521000

5519000

5517890

5439000

5438850

5551030

5551060

5551620 5551520

5540275

5540130 5540250

5526150

5551330

5551530

A

Southern Lake, Cook, and 

DuPage County streamgage 

identifiers shown in figure 10B

5540195

5537500

5536310

EXPLANATION

Boundary of Level 4 Watershed Dataset subbasin

USGS streamgage with record ending in 1980 (including 1980) and identifier

USGS streamgage with record starting after 1980 and identifier

USGS streamgage with record through 1980 and identifier
Case Study: Urbanization Effects on Flood Flows in the Chicago Area 15

Figure 8. A, Locations of U.S. Geological Survey (USGS) streamgages measuring the 143 watersheds in the Chicago region 

(Thomas Over and David Soong, U.S. Geological Survey, written commun., 2012); B, Locations of U.S. Geological Survey 

(USGS) streamgages measuring the 143 watersheds in the Chicago region (Thomas Over and David Soong, U.S. Geological 

Survey, written commun., 2012).—Continued

0 1 246 8 M0 ILES

0 1 2468 0 KILOMETERS

Lake Michigan

Des

River

River

Plaines

Little Calumet

River

Salt Creek

West Branch

Branch

Branch

Du Page

River

East

North

Chicago

5549850

5549700

88° 87°40'

42°

41°40'

Base from U.S. Geological Survey

Watershed Boundary Dataset from Natural Resources

Conservation Service.

1:24,000-scale digital data.

Du Page

Cook

Lake

Will

5550500 5550470

5550450

5550430

5540240

5540195

5540195

5540190

5540160

5540150

5540140

5540110 5540095

5540091

5540080 5540060 5540030

5539950 5539900

5539890

5539870

5539000

5538440

5537500

5537500

5536630

5536620

5536570

5536560

5536510

5536500

5536460 5536340

5536335

5536310

5536310

5536275

5536270

5536265

5536255

5536238 5536235

5536215

5536207 5536210

5536201

5536195

5536178

5536105

5536000

5535800

5535700

5534600

5535500 5534500

5535400

5535300

5535200

5535150

5535070

5535000

5534900

5534400

5534300

5533400

5533300

5533200 5533000

5532000

5531800

5531500

5531380

5531300

5531200

5531130

5531100

5531080

5531050

5531000

5530990

5530960

5530940

5530700

5530480

5530400

5530000

5529900

5529500

5529300

5528500

5528360

5528470 5528440

5528230

5528200

5528170

5528150

ILLINOIS

INDIANA

EXPLANATION

B. Inset area from figure 8A

Boundary of Level 4 Watershed Dataset subbasin

USGS streamgage with record ending in 1980 (including 1980) and identifier

USGS streamgage with record starting after 1980 and identifier

USGS streamgage with record through 1980 and identifier
16 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

Future Steps

The dependence of annual maximum peak streamflow 

on urbanized area appears to be reasonable and has been 

used to compute adjusted values of the annual maximum 

peak flow data for each station record that corresponds to 

present land-use conditions. Future research could further 

improve our understanding of the relation between urbanization and discharge. For example, satellite imagery and aerial 

photograph-based estimates of urbanized areas might improve 

the coefficient of urbanized fraction. Likewise, how might 

historical impervious area estimates from aerial photography analyzed over a region of this size affect the estimate of 

urbanization effects on discharge? As mentioned, impervious area is not the only hydrologically important measure of 

urbanization. The construction of curb-and-gutter streets, their 

associated storm drains, and channel straightening and lining 

also contribute substantially to the effects of urbanization on 

streamflow. In addition, in the last few decades, the process of 

urbanization has become associated with measures to mitigate 

its effects on streamflow, such as stormwater detention. Is it 

feasible to identify and measure these features of the urban 

landscape at the regional scale in historical imagery? In recent 

research (Thomas Over and David Soong, U.S. Geological 

Survey, written commun., 2012 ), the effects of these features could not be separately assessed and were assumed to 

have been subsumed in the housing density-based measure of 

urbanization. Finally, some studies report that spatial arrangement of impervious area affects response (Falcone and others, 

2007; Moglen and Shivers, 2006; Sauer and others, 1983). 

How then should such information best be used, and how 

much difference would it make?

Methodological Way Ahead

To begin addressing these questions, further research 

could develop methods to improve the ability to quantify the 

amount of impervious surfaces from the aerial photographs. 

Land-change detection in urbanizing areas is challenging. 

Although they may shift from one land class to another, 

agricultural and forested areas in the ecoregion are often 

more homogenous, whereas urban areas are a heterogeneous 

mixture of different surfaces with different levels of imperviousness (Platt, 2004; Xian and others, 2006). It is the heterogeneous characteristics of urban areas that contribute to the 

difficulties of land-change detection in urban and suburban 

areas using remote sensing techniques. For example, pixels 

that were classified as developed may vary between 20 percent 

and 100 percent in their impervious surface and they might 

vary between 0 and 60 percent in their tree canopy coverage (Xian and others, 2006). To attempt to overcome these 

challenges, the authors currently are testing a feature extraction method to identify impervious surfaces based on characteristics such as brightness, shape, and texture in the aerial 

photographs as well as current modeling efforts to determine if 

backcasted estimates of developed land change based on current land-change rates could be incorporated. 

Number of watersheds

Drainage area, in square miles

0

20

30

35

10

0.02 0.1 0.5 2 5 20 100 0.05 0.2 1 10 50

Figure 9. Drainage areas of the 143 watersheds in the Chicago 

region (Thomas Over and David Soong, U.S. Geological Survey, 

written commun., 2012). Number of stations

Water year

60

100

120

80

1940 19601950 1970 1990 1980 2000 2005

0

20

40

140

Figure 10. Number of streamflow-gaging stations with peak flow 

data during each water year in the study of 143 watersheds in the 

Chicago region (Thomas Over and David Soong, U.S. Geological 

Survey, written commun., 2012).
Future Steps 17

Figure 11. Comparison between Theobald (2005) exurban/urban housing plus commercial-industrial-transportation 

(C/I/T) land area and U.S. Geological Survey Land Cover Trends Project developed area for the 40 100-km2 sample 

blocks in Ecoregion 54 (Central Corn Belt Plains) for 1939/40, 1970/73, 1980, 1990/92, and 2000. The commercialindustrial-transportation land areas in Theobald (2005) are from the year 2000, and so for other years, these values 

were adjusted proportionally to the changes in housing density (Thomas Over and David Soong, U.S. Geological 

Survey, written commun., 2012).

0

10

20

30

40

50

60

70

90

0 20 40 60

80

80

100

100

Area of adjusted 1970 Theobald urban housing

and C/I/T (classes 7–10), in square kilometers

1973 Trends developed area, in square kilometers

y = 0.9874x + 0.657

R2

 = 0.9721

0

10

20

30

40

50

60

70

90

0 20 40 60

80

80

100

100

Area of adjusted 1980 Theobald urban housing

and C/I/T (classes 7–10), in square kilometers

1980 Trends developed area, in square kilometers

y = 1.0258x + 1.1335

R2

 = 0.9637

0

10

20

30

40

50

60

70

90

0 20 40 60

80

80

100

100

Area of adjusted 1990 Theobald urban housing

and C/I/T (classes 7–10), in square kilometers

1992 Trends developed area, in square kilometers

y = 1.0068x + 1.0726

R2

 = 0.9708

0

10

20

30

40

50

60

70

90

0 20 40 60

80

80

100

100

Area of 2000 Theobald urban housing

and C/I/T (classes 7–10), in square kilometers

y = 1.0001x + 1.1678

R2

 = 0.9738

0

Area of adjusted 1940 Theobald urban housing

and C/I/T (classes 7–10), in square kilometers

1939 Trends developed area, in square kilometers

y = 1.1384x + 0.5143

R2

 = 0.9824

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

2010 Trends developed area, in square kilometers

EXPLANATION

OLS regression

1:1 line

Observed value
18 Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas

Conclusions

This report combines land-cover change analyses with 

urbanization effects on hydrologic discharge in order to provide input to a multi-disciplinary understanding of the effects 

of land change on earth systems such as urban watersheds. 

The Central Corn Belt Plains Level III ecoregion was analyzed for land-change rates, causes, and consequences from 

1939 to 2000 with a specific focus on how the increased 

development may be influencing regional hydrology. The case 

study presented in this report demonstrates that a generalized 

quantification of developed (“urban”) land needs to be further 

refined in order to better understand the effects of urbanization 

on regional hydrology. Further collaboration might begin to 

assess additional consequences of developed land change such 

as water quality and stream ecology. Additional avenues of 

research collaboration would include studying the effect of the 

patterns of the land change in urban watersheds in response to 

efforts such as stormwater mitigation structures. Such collaborations provide a more comprehensive approach to determining how changes in land use and land cover contribute to 

land resources condition, and insight on how the geographic 

variability of change may affect land management priorities 

and practices. 

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Figure 12. Partial residuals of base-10 logarithms of peak 

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2.0

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1.0

0 0.2 0.4 0.6 0.8 1.0

Ratio of the estimated annual 

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EXPLANATION

Partial residual fit indicating the dependence of the 

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precipitation removed; slope = 0.5117 and intercept = 0

Observed value

Urban fraction

log10 (observed peaks, in cubic feet per 

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1.5

1.0

0.5

0

-0.5

-1.0

-1.5 0 0.2 0.4 0.6 0.8 1.0
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Land-Cover Class Descriptions 21

Land-Cover Class Descriptions

water Areas persistently covered with water, such as streams, canals, lakes, reservoirs, bays, or 

oceans. 

developed Areas of intensive use, with much of the land covered with structures or anthropogenic impervious surfaces (for example, high-density residential, commercial, industrial, and 

roads) or less intensive uses where the land-cover matrix includes both vegetation and structures 

(for example, low-density residential, recreational facilities, cemeteries, parking lots, and utility 

corridors), including any land functionally related to urban or built-up environments (for example, 

parks and golf courses).

mining Areas with extractive mining activities that have a substantial surface expression, which 

includes (to the extent that these features can be detected) mining buildings, quarry pits, overburden, leach, evaporative, tailings, or other related components.

barren Land composed of soils, sand, or rocks where less than 10 percent of the area is vegetated. 

Barren lands usually are naturally occurring.

forest Tree-covered land where the tree-cover density is greater than 10 percent. Note that cleared 

forest land (clear-cuts) is mapped according to current cover (for example, mechanically disturbed 

or grassland/shrubland). 

grassland/shrubland Land predominately covered with grasses, forbs, or shrubs. The vegetated 

cover must comprise at least 10 percent of the area.

agriculture Land in either a vegetated or an unvegetated state used for the production of food 

and fiber, which includes cultivated and uncultivated croplands, hay lands, pasture, orchards, 

vineyards, and confined livestock operations. Note that forest plantations are considered forests 

regardless of the use of the wood products.

wetland Land where water saturation is the determining factor in soil characteristics, vegetation 

types, and animal communities. Wetlands usually contain water and vegetated cover.

ice and snow Land where the accumulation of snow and ice does not completely melt in the 

summer period (for example, alpine glaciers and snowfields).

nonmechanically disturbed Land in an altered and often unvegetated state that, because of disturbances by nonmechanical means, is in transition from one cover type to another. Nonmechanical 

disturbances are caused by fire, wind, floods, animals, and other similar phenomena.

mechanically disturbed Land in an altered and often unvegetated state that, because of disturbances by mechanical means, is in transition from one cover type to another. Mechanical disturbances include forest clear-cutting, earthmoving, scraping, chaining, reservoir drawdown, and 

other similar human-induced changes.
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Karstensen and others—Land Change in the Central Corn Belt Plains Ecoregion and Hydrologic Consequences in Developed Areas—Open-File Report 2013–1157