THE MIGRATION OF THE LITTLE WABASH RIVER CHANNEL OVER SEVEN DECADES – CLAY COUNTY, SOUTHCENTRAL ILLINOIS

Geology consists of various landscape-changing processes. One of the most dynamic of these processes involves rivers. They cut back and forth across the landscape inscribing their channels into the underlying strata. Over time, a river’s channel is capable of laterally migrating substantial distances. The Little Wabash River in southcentral Illinois has been the focus of recent work to find how the channel’s path has evolved over several decades (Burns and Viertel, 2011) in the area encompassed by Effingham County. This study takes the project forward, examining the channel’s migration through time in Clay County.

The Little Wabash is a meandering river whose headwaters originate in southwestern Coles County and flows southward approximately 200 miles to its confluence with the Wabash River. The watershed through which the Little Wabash flows is devoted primarily to corn, hay, soybean and winter wheat production (IEPA, 2006). The river winds its way across distinct properties, some of which may not be owned by the same entity on either side of the river. Therefore, any change in the stream’s path creates a loss or gain of acreage, which directly impacts the landowners. In the 2011 study, a total of 241 acres were found to now be on the opposite side of the channel’s previous path in Effingham County. The goal of this project was to apply the same GIS techniques to the area deliminated as Clay County. Clay County’s dominant land use is agricultural in nature, with crops of corn, soybeans, wheat, oats and sorghum. The yields from these are substantial – in 2007, for example, corn yielded 8,473,314 bushels and wheat yielded 634,160 bushels (USDA/NASS, 2007). These yields along with the other crops equated to over 72 million dollars of gross revenue in 2007 alone. Any loss or gain of acreage due to an alteration in the river’s path will have a significant impact to any farm owner involved.

The historical channel of the Little Wabash River was digitized to establish a baseline survey using archival aerial photography acquired in 1938, which were georegistered to their proper locations and proportions. Current channel position was acquired through a basemap within the GIS ArcMap software. The comparison between the datasets highlights the alterations that have occurred along the Little Wabash River’s path over the last 75 years in Clay County.