Impact of channelization and dam construction on Kaskaskia River morphology

Since the 1960's in-stream modifications, Carlyle Dam and channelization activities have altered the natural hydrologic and ecological equilibrium of the Kaskaskia River. My study objective was to analyze the long-term impacts of Carlyle Dam and channelization on Kaskaskia River channel morphology. Bankfull channel width from aerial photographs was used as the primary indicator to assess pre- and post-modification channel width change. We found that channel width change was significantly greater during the post-modification period along the entire reach. The mean channel width changes in sub-reach two and three (closer to the channelization terminus) were significantly greater than sub-reach one (downstream of the dam). The morphology impacts of channelization had extended approximately 38 river km upstream.; Specific-gage analysis and pseudo-specific-gage analysis (PSGA) were used to assess channel bed changes over time. Results suggested that there was no significant channel bed incision trend near the river gages with the studied time period. Nevertheless, the substantial channel widening following channelization and dam construction on the Kaskaskia River has accelerated bank erosion and associated channel morphology change and consequently resulted in a net loss of riparian habitat in this important bottomland forest corridor in southern Illinois.