Sedimentation and Turbidity

The geology of the Illinois River provides conditions that increase sedimentation. The low gradient does not allow the sediment delivered by its headwaters and tributaries to wash downstream. When farming increases throughout the Illinois River valley beginning in the early 1900s, the amount of sediment reaching the river increases dramatically. The construction of locks and dam exacerbates the problem by preventing even more sediment from moving downstream. As a result of the river's natural conditions and changes in land use, the remaining backwater lakes begin to fill in rapidly (Cruikshank 1998).