EIGHT DECADES OF GEOMORPHOLOGICAL CHANGE TO THE LITTLE WABASH RIVER, EAST-CENTRAL ILLINOIS, USA

Geologically-speaking, rivers are extremely dynamic, cutting back and forth and re-inscribing their channel paths into the underlying and laterally adjacent sediments repeatedly over the years. Rivers are continuous eroders of bedrock as well as bank material, constantly reshaping the landscapes through which they course. Through time, a river’s channel can move a fair distance laterally – a change of 750 meters is not uncommon. Local studies of individual rivers or stream reaches have been examined in relation to factors such as groundwater supply (VanLooy, 2005), endangered species habitat (Greco and Plant, 2003), and channelization processes in agricultural watersheds (Urban and Rhoads, 2003). This study examines changes in the hydraulic environment of the Little Wabash River in East Central Illinois. Special attention is given to the impact of channel changes on agricultural acreage.

The Little Wabash River is a meandering river that has its headwaters in southwestern Coles County and that flows southward approximately 200 miles to its confluence with the Wabash River. The watershed through which the Little Wabash River flows is primarily devoted to agricultural uses, yielding crops such as soybean, corn, winter wheat and hay (IEPA, 2006). The river wends its way across distinct land holdings, many of which are not owned by the same entity on both sides of the river. Any change in the stream’s pathway therefore means a loss or gain of acreage directly impacting landowners adjacent to the channel. The goal of this project is to determine what changes the river has made to the surrounding agricultural acreage through the last 80 years.

The historical channel of the Little Wabash River was delineated to establish a baseline survey using archival aerial photography acquired in 1938. Current channel position was initially determined using 2008 Quickbird satellite imagery and supplemented with field-checked reference sections along the length of the study area. The comparison among the datasets documents the significant alterations that have occurred along the Little Wabash River over the last 80 years and reflects the impacts upon local landowners.