Riparian Wetland Restoration Suitability Analysis for the Middle Mississippi River Floodplain, in Monroe County, Illinois

Abstract

Riparian wetlands are unique ecosystems that provide beneficial environmental services to surrounding communities, but have been replaced by farm fields and human development throughout history within river floodplains. As a consequence, there are inadequate natural buffer zones to absorb, filter, and slowly release excess flood water back into the system in case of levee failure. This became apparent in the Great Flood of 1993 when Southern Illinois towns became inundated with record river levels rising 6 meters over flood stage near St. Louis. After this devastating natural disaster, communities started turning towards alternative methods of flood control like wetland restoration. This study analyzes areas of comprehensive suitability for wetland restoration within a 15 kilometer reach of the Middle Mississippi River near Valmeyer, Illinois. Using GIS (Geographical Information Systems) spatial analysis and mapping, the overlaid layers of elevation, soil type, floodplain zones, land ownership, and existence of infrastructure, including structures, roads, and levees, revealed suitable sites for wetland restoration. Findings show that scenarios where wetland sites are proposed directly adjacent to the river channel without fragmentation from human development or restriction by levees, though often more costly in restorations, provide the most ecological functionality for flood water mitigation. In scenarios where wetlands would be restored behind levees in smaller land portions, restoration would be less expensive, but also less functional in absorbing and relieving flood water.