Seasonal floods maintain the biological productivity and diversity of floodplain-river ecosystems, but the effect of infrequent, great floods on these ecosystems are less well known. Knowing the effect of this type of flood is critical where river ecosystems have been developed and where floodplains are now being restored because there are likely trade-offs between using restored floodplains to maintain native species and natural functions and using them to reduce threats to lives and property. The record flood of April 2013 on the Illinois River flooded two floodplain restoration projects undertaken by The Nature Conservancy; neither project had received river water prior to 2013. There were two contrasting flood regimes: 1) at the Merwin site, the levee breached resulting in a sudden and sustained influx of river water. This flood pattern typifies what happens during intentional breaching to reduce a flood crest; 2) at Emiquon, the levee held but river water flowed into the site inoculating the area with nutrients and organisms. The pattern at Emiquon typifies a seasonal flood or a flood managed to optimize species recovery and natural functions. At both sites, rapid responses will be measured in nutrient and sediment concentrations, sediment denitrification, and change in algal biomass, bacterial communities and zooplankton production. Longer-term responses of vegetation, fish, and water birds will be determined by comparing post flood 2013 data to existing long-term data sets.
Results from this project, including both short and long-term data sets and analyses, will assist floodplain managers and policymakers. This project will support the dissertation research of three graduate students and provide research experiences for three undergraduate students in river ecology. Lessons learned will be shared with the public and government and private organizations through publications and field-based lectures/workshops for students and visiting groups through established programs at three river field stations.
