POTENTIAL USE OF INNOVATIVE DREDGE TECHNOLOGY AND BENEFICIAL USE OF SEDIMENT FOR RIVER RESTORATION

During the past century sediment has filled over 70 percent of the volume of the Illinois River backwaters and side channels. Areas that were once six to eight feet deep are now 18 inches or less at normal pool. Sedimentation’s dramatic adverse impact on recreational and environmental resources has been well documented (see references below). The sediment has essentially replaced a diverse benthic habitat with a flat, featureless layer of fine grained sediment under shallow water. Additionally, since 1900 higher average water levels resulting from the altered hydrologic regime have made it impossible for many native floodplain flora and fauna to remain in their historic locations. Within a generation most of the 60,000 acres of backwaters will be converted to willow covered mudflats if depth is not restored and sediment input reduced. The filling of the of the backwaters is dramatically illustrated by the Department of Natural Resources flyer “Illinois River Backwaters Between Chillicothe and Lacon, ” included as Figure 1. In this seven mile stretch it is readily apparent that the islands which separated Babbs Slough from the main channel in 1970 were one long, wide peninsula by 1994. Areas such as the upper end of Sawyer Slough have essentially been converted to land and other areas such as the islan