The use of large water and sediment diversions in the lower Mississippi River (Louisiana) for coastal restoration

SummaryThis study examines the use of large sediment and water diversions in the lower Mississippi River (e.g., South Louisiana) as a tool for coastal restoration. Herein we provide a review, new analysis and synthesis of existing work, much of it previously only available in government reports, and integrate our recent research on the topic. We outline critical knowledge gaps that need to be addressed by the time that construction begins on any future large diversions. The focus of this study is on “river side” issues and the policy considerations that arise from them.The study includes a quantitative examination of the sediment budget of the Lower Mississippi River as a region of potential diversion construction in South Louisiana, due to its critical control on any future management plans that include large diversions. We conclude that development of a coordinated system of diversions and other restoration strategies for land-building will require parceling this sediment budget out between individual projects. However, this is only possible if the input function and its variability is well understood. It is clear that numerical simulations are the only way to adequately predict the combined effects of multiple diversions and other restoration projects, such as dredge-fed pipelines, on the river channel for navigation, flood control and sediment regime. Numerical models also provide the only way to properly examine diversion structures to maximize their sediment capture and minimize any negative impacts. The status of these models and their application to lower Mississippi River channel hydrodynamics and sediment transport is examined herein.