The Missouri and Mississippi  River ecosystems have been leveed and dammed to control flooding and facilitate the transportation of goods.  While generally successful in keeping floods at bay, these anthropogenic river training structures permanently altered the ecosystems of these two large rivers by disconnecting them from their associated floodplains.  During 2011, excessive spring runoff caused by snow melt and high rainfall events overwhelmed the capacity of these structures, creating calamitous floods.   Although catastrophic for the people and communities located along the rivers, the flood of 2011 provided scientists an opportunity to investigate the function of floods on large river biota.  Missouri and Mississippi river basin states employed varying strategies to monitor flood impacts on aquatics resources.  Specifically, scientists evaluated entrainment through the mainstem dams, immigration and emigration from floodplain habitats, destruction and creation of habitats, productivity and endangered species throughout the high flow period.  This symposium will serve as a venue for those scientists to describe the direct effects of the flood, and to set the foundation for determining the long term effect the floods of 2011 had on the Missouri and Mississippi Rivers’ ecosystems.