1. 1
Pre-Settlement Drainage Network Configuration in the
Upper Sangamon River Basin
Jacob Henden and Alison Anders, University of Illinois Urbana-Champaign, Urbana, Illinois
Abstract
Prior to European settlement in the1850s, the recently glaciated landscape of the Upper
Sangamon River Basin (USRB) was evolving toward a well-developed fluvial landscape via the
headward expansion of river channels. After settlement, the landscape was converted from tall
grass prairie to corn and soy agriculture. This intensive agriculture, typical in the U.S. Midwest,
requires significant modification of drainage networks. Drainage ditches and tile drainage were
added to the basin, and the modern channel network is now significantly more expansive than it
was in the early 1800s. The pre-settlement drainage network provides information about how
the landscape was evolving since the last episode of glaciation and before significant human
impacts. We estimate the physical locations of incised channels within the USRB prior to
European settlement using General Land Office (GLO) surveys from the early 1800s, USDA
Natural Resources Conservation Service soil maps, and LIDAR-based digital elevation models.
Early maps and soil surveys support the hypothesis that these regions lacked a complete fluvial
drainage network, and LIDAR topography suggests about 40% of the USRB lacked incised river
channels prior to the conversion to agriculture. The soil maps and the 1800s GLO maps place the
channels in roughly the same locations with 82% of the mapped 1800s channels existing within
50 meters of alluvial soils. All data sets used show similar patterns for the configuration of the
pre-settlement drainage network.
Introduction
The transportation of water and sediments across a landscape is largely controlled by channels
and lakes within a drainage basin, collectively these features are called drainage networks.
Drainage networks are largely determined by the elevation and slope of the land. Various factors,
such as climate, geologic structure, and lithology, influence topography and erosion rates of
landscapes and, by extension, the formation of drainage networks (Nag and Chakraborty, 2003).
Glaciation, the movement of glaciers over a landscape, effects topography and can completely
alter the location of drainage networks. When this occurs it is known as drainage reversal. In
some circumstances, tributaries can be blocked making landscapes less connected by channels
(Coffey, 1961). After an episode of glaciation, an area can change from a glacial to a fluvial
landscape, through the expansion of drainage networks. In a glacial landscape the land is shaped
by the previous episode of glaciation, while in a fluvial landscape the land is shaped by stream
erosion.
Humans have direct and indirect impacts on drainage networks, often on a more rapid time scale
compared to other factors (Gregory 2006). Human influence on drainage networks is
particularly pronounced in certain regions of the U.S. Midwest, where high intensity agriculture
on wet, flat terrain promotes the use of tile draining and extensive drainage ditches (Urban and
Rhodes 2003). Rhodes et al., (2015) examined how the drainage network of the Upper
Sangamon River Basin (USRB), a previously glaciated region in Illinois, has changed since the
introduction of agriculture. They compared the current channels to mapped historical channels,

2. 2
and estimated the current channel network to be almost three times as extensive compared to
before the 1850s (Rhodes et al., 2015).
The intent of this paper is to produce an estimate for the configuration of the pre-settlement
drainage network of the USRB in order to gain a better understanding of the network’s natural
evolution. General Land Office (GLO) surveys from the early 1800s, USDA Natural Resources
Conservation Service soil maps, and LIDAR-based digital elevation models were used to derive
estimates for physical locations of historic channels, and to determine what extent of the basin
contains natural channels. The results of this research are intended to help produce a model for
how drainage networks evolve in previously glaciated low-relief areas.
Study Area
The Upper Sangamon River Basin is a 2300 km2
basin in East Central Illinois. The geologic
features of the basin are flat uplands, moraines, and incised valleys. The limited expanse of
incised valleys includes the Sangamon River and major tributaries (Illinois Department of
Natural Resources, 1999a). A greater percentage of the incised valleys exist in the southern half
of the USRB, and a greater area covered by moraines exists in the northern half of the USRB.
The flat uplands cover the most area throughout both the northern and southern halves of the
basin (Figure 1). The relatively flat topography (average slope less than 2%) of the landscape is
largely a result of the Wisconsin episode of glaciation approximately 25,000 years ago (Stiff and
Hansel, 2004). Prior to European settlement, vegetation cover of the basin was primarily tall
grass prairie, now the region is dominated by corn and soy agriculture. (Illinois Department of
Natural Resources, 1999c)
The basin is a Critical Zone Observatory for Intensively Managed Landscapes (CZO-IML) as
designated by the National Science Foundation. The Critical Zone is defined as the area ranging
from upper vegetation canopies to the bottom of the active aquifers, the name critical referring to
its critical role in maintaining life. Critical Zone Observatories are intended to integrate
interdisciplinary studies up to the watershed scale (Anderson, et al., 2008). Reconstruction of the
pre-settlement channel network in the USRB is necessary to evaluate the transport of water and
sediment prior to the advent of intensive agriculture.
Data and Methods
Historic channel locations based on General Land Office (GLO) surveys from before 1850 were
obtained as digital georeferenced shapefiles. The Prairie Research Institute at the University of
Illinois produced these shapefiles using original plat maps from the Illinois State Archives. The
modern channel shapefiles were produced from georeferenced digital line files from the U.S.
Geological Survey that were cross-referenced with 2012 Aerial Photography from the U.S.
Department of Agriculture (USDA) to include only well-defined channels (Rhoads et al., 2015).
We make an independent estimate of natural channel locations using soil survey data. The
dominant parent materials for soils in the USRB include loess, till, outwash and alluvium
(Illinois Department of Natural Resources, 1999a). Alluvial soils are deposited by running water,
and the presence of alluvial soils can indicate historic presence of channels and floodplains.

3. 3
Locations of alluvial soils were obtained using soil maps from the USDA Natural Resource
Conservation Service (NRCS) soil surveys. Soil maps from the USRB were downloaded from
the NRCS web soil survey. Soils that had alluvium named as a parent material on their official
soil series descriptions were selected to create a shapefile of alluvial soils within the USRB. The
proximity of the channels mapped in the early 1800 GLO surveys and the channel estimates
derived from the NRCS soil surveys were evaluated using analysis tools in ArcMap.
Topography of the study area was examined using LIDAR data, obtained from the Illinois
Height Modernization Program (ILHMP). LIDAR (Light Detection and Ranging) data was used
to produce 1 meter contour lines in ArcMap. The LIDAR raster and contour lines were used to
estimate areas with and without natural channels. Areas with natural channels have contour lines
with characteristic V-shaped patterns, while in areas without natural channels this pattern is not
seen. In areas with natural channels, there appears to also be wide sloping valleys that lead to the
channels. In areas without natural channels, but with drainage ditches, these natural valleys are
not seen. A natural channel appears to be influenced by surrounding topography, while drainage
ditches largely do not appear to be influenced by surrounding topography.
Two different methods were used to estimate the extent of unchannelized area within the USRB.
One method produced a maximum estimate that had a higher estimate for what percent of the
USRB was unchannelized. The other method produced a minimum estimate that had a lower
estimate for what percent of the USRB was unchannelized. The methods are somewhat
subjective, because the classifications were made visually. For each estimate the LIDAR raster
and contour lines were referenced to select places without the characteristic V-shaped patterns
and wide sloping valleys. In the minimum estimate, there are no V-shaped patterns or wide
sloping valleys. In the maximum estimate, areas are included where it is unclear whether there
are V-shaped patterns and wide sloping valleys, and subsequently, whether there are natural
channels. Examples of a clearly channelized, a clearly unchannelized, and an area that would fall
between the classifications can be seen in (Figure 2). The estimates were averaged together to
derive an estimate for what percent of the basin had natural channels. Elevation and slope for
various estimates were derived using analysis tools in ArcMap. For slope and elevation
estimates, a 30 meter DEM was used instead of the LIDAR raster for the advantage of faster
processing.
Results
Alluvial soils as mapped by the NRCS occur in approximately 4.3% of the USRB. The soil
maps and the 1800s GLO maps place the channels in roughly the same locations with 82% of the
mapped 1800s channels existing within 50 meters of alluvial soils. In comparison only 57% of
modern channels exist within 50 meters of alluvial soils (Figure 3). The modem channel
network is approximately three times more extensive than the estimates based on the 1800s GLO
maps and approximately twice as extensive as the estimates based on the mapped alluvial soils
The minimum estimate for the fraction of the area of the USRB that lacked natural channels was 36.6%
and the maximum estimate was 44.3%, producing an average estimate of 40.45% (Figure 4). The mean
elevation for the Upper Sangamon River Basin is 220.16 meters and the mean slope is 1.52%. In
areas without natural channels the mean elevation is 222.98 meters and the mean slope is 0.82%.
In channelized areas the mean elevation is 219.156 meters and the mean slope is 1.83%. The

4. 4
channelized areas have lower elevations and greater slopes than the non-channelized areas.
Additionally less than 3% of both the alluvial and 1800s channel estimates occur within non
channelized areas. In comparison, 13% of modern channels occur within non channelized areas.
Discussion
The various data sets used present different challenges in producing estimates for the pre-
settlement drainage network. It is uncertain precisely what size of streams surveyors in the
1800s would record, although previous work with these GLO maps place the minimum recorded
width at 1-1.5 meters. It is also difficult to know if there was consistency between multiple
surveyors, for example some surveyors might have recorded a channel that didn’t have water
flowing through it, while others might not have (Rhode et al., 2015). NRCS soils classified as
alluvium might show areas with wetlands as opposed to just areas with floodplains containing
natural channels, as the soil samples for these areas would look very similar. The LIDAR
elevation represents the topography that the USRB has today and contains artificial features
including ditches and overpasses not present prior to the 1850s. However, the fact that various
data sets used show similar patterns for the configuration of the pre-settlement drainage network
suggests that they can be used to distinguish natural channels from drainage ditches. In order to
increase the accuracy and precision of these estimates, soil cores could be taken at various sub-
watersheds within the USRB. Areas of particular interest may include locations where the
various estimates place the pre-settlement channels in different places.
Prior to European settlement, we estimate that the channel network of the USRB would have
looked like the 1800s GLO survey and alluvial soil estimates (Figure 3). The channel network
was most likely expanding and covered about 60% of the basin (Figure 4). The significant
human modification to the drainage network of the USRB makes the configuration of the pre-
settlement channels necessary to study the natural evolution of the network, and the transition of
the basin from a glacial to fluvial landscape. In particular the locations of the natural channel
heads are an important component to understanding the hydrology of the landscape
(Montgomery and Dietrich, 1989). We would expect to find the natural channel heads in areas
near 1800s surveyed streams, alluvial soils, and in areas with relatively low elevation and high
slope.

5. 5
Figures
Figure 1. The Upper Sangamon River Basin (USRB) located in east central Illinois.
Shown with approximate locations of incised valleys, flat uplands, and moraines.
Figure 2. 1 meter contour lines made from a LIDAR digital elevation model, and the modern channel
network shown in three areas within the USRB. A clearly unchannelized area shown in A. An area that is
unclear whether it may have natural channels shown in B. An area with natural channels shown in C.

6. 6
Figure 3. Modern channel network of the Upper Sangamon River Basin (USRB) derived from U.S. Geological
Survey topographic maps cross referenced with 2011 aerial imagery shown in A, 1800s General Land Office surveyed
channels shown in B, and alluvial soils from USDA National Resource Conservation Soil maps shown in C.

7. 7
Acknowledgments
We thank the National Great Rivers Research and Education Center for providing funding for
this project, Rodger Windhorn and Dave Grimely for advice in interpreting NRCS soil maps, and
Quinn Lewis for providing shapefiles of the mapped 1800s and modern channel networks used
for analysis.
Figure 4. Areas in the Upper Sangamon River Basin (USRB) with no natural channels based on
estimates derived from LIDAR topography shown in comparison to locations of 1800s General Land
Office Surveyed Channels shown in A, in comparison to alluvial soils from USDA National Resource
Conservation Soil Maps shown in B, and in comparison to the modern channel network derived from
U.S. Geological Survey topographic maps cross referenced with 2011 aerial imagery shown in C.

8. 8
Literature Cited
Anderson, S. P., Bales, R. C., & Duffy, C. J. (2008). Critical zone observatories: building a
network to advance interdisciplinary study of Earth surface processes. Mineralogical
Magazine, 72(1), 7-10.
Coffey, G. N. (1961). Major preglacial, Nebraskan and Kansan glacial drainages in Ohio,
Indiana, and Illinois. Ohio J. Sci, 61(5), 295-313.
Gregory, K. J. (2006). The human role in changing river channels. Geomorphology, 79(3), 172-
191.
Hooke, R. (1999). Spatial distribution of human geomorphic activity in the United States:
comparison with rivers. Earth Surface Processes and Landforms, 24(8), 687-692.
Illinois Department of Natural Resources, 1999a. Upper Sangamon River Area Assessment,
Volume 1: Geology, Champaign, IL
Illnois Department of Natural Resources, 1999c. Upper Sangamon River Assessment, Volume 3,
Living Resources. , Champaign, IL
Montgomery, D. R., & Dietrich, W. E. (1989). Source areas, drainage density, and channel
initiation. Water Resources Research, 25(8), 1907-1918.
Nag, S. K., & Chakraborty, S. (2003). Influence of rock types and structures in the development
of drainage network in hard rock area. Journal of the Indian Society of Remote Sensing,
31(1), 25-35.
Rhoads, B. L., Lewis, Q. W., & Andresen, W. (2015). Historical changes in channel network
extent and channel planform in an intensively managed landscape: Natural versus
human-induced effects. Geomorphology.
Stiff, B. J., & Hansel, A. K. (2004). Quaternary glaciations in Illinois. Quaternary glaciations:
extent and chronology, 2, 71-82.
Urban, M. A., & Rhoads, B. L. (2003). Catastrophic human-induced change in stream-channel
planform and geometry in an agricultural watershed, Illinois, USA. Annals of the
Association of American Geographers, 93(4), 783-796.