Author(s): Samuel J. Bentley, Clinton S. Willson, Scott C. Hagen, Robert R. Twilley
Linked Author(s): Samuel Bentley
Keywords: River delta, resilience, sediment supply, Mississippi
Abstract: River deltas and the communities upon them are threatened globally by the combined effects of relative sea-level rise, reduced sediment supply, and other unintended consequences of river-management strategies. Globally, this constitutes a threat to communities hosting >500 million residents, massive infrastructure, and major agricultural, navigation, and other resource sectors. The State of Louisiana in the United States is home to the delta of the Mississippi River (Mississippi River Delta, or MRD), a coastal landscape of approximately 18, 000 km2 that has formed over the last 8, 000 years, where the Mississippi discharges into the Gulf of Mexico. Since the 1930�s, land area of the MRD has decreased by >5, 000 km2, and estimates of potential future land loss under possible future sea-level-rise scenarios exceed an additional 10, 000 km2. Key causes of this land loss include dam construction on upper tributaries; construction of levees along the river mainstem, and deltaic subsidence. Extensive human outmigration has occurred in the MRD, with socio-political consequences. In response, the State of Louisiana established a Coastal Master Plan in 2007 to guide coastal conservation efforts. Mostly as a result of projected increases in sea-level rise, projects included in the 2017 draft plan will no longer be able to eliminate future land loss. So, what can be done? We propose three new concepts. First, consider a smaller, but more sustainable delta area. Second, attempt to reduce loss of sediment passing through the MRD for more efficient land building. Third, increase the volume of sediment delivered from the catchment to the delta, via controlled floods and engineered increases in river gradient. None of these possible strategies are without risk. Nevertheless, in order to sustain a Mississippi River Delta for future generations, creative solutions must be sought, tested, and implemented
Year: 2017