Managing floods in large river basins in the USA: The Mississippi River

Abstract

The Mississippi River was the first theater in which the federal government sought to control floods and improve navigation through the efforts of the US Army Corps of Engineers, initially under a "levees only" philosophy, later revised (after the disastrous 1927 flood) to include multiple approaches, such as backwater areas and flood bypasses. The Mississippi River and Tributaries Project successfully conveyed the 2011 flood (with more rainfall than fell in 1927), but operation of criticalbypasses was threatened by encroachment of buildings within the bypasses, permitted by local governments. Structures designed to concentrate flow for the benefit of navigation can result in higher flood stages and thus can undermine flood control efforts. Allowing floodplains to flood naturally, as much as possible, can have benefits not only for the ecosystem but also for managing floods to minimize inundation of cities.