Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions

Abstract

Using the Mississippi River as a tool for restoration has been a key element of restoration planning in Louisiana for decades. The results of allowing river water and sediment back into the coastal system are manifested in a number of places in present day Louisiana, with additional plans for large scale sediment and water diversions from the Mississippi River. Many previous numerical modeling studies have focused on sediment delivery to Louisiana estuaries. This study examines the effects of river diversions on salinity gradients in receiving estuarine basins. The Integrated Compartment Model, a planning-level model that simulates multi-decadal change in estuarine hydrodynamics and wetland systems under assumed sea-level rise scenarios, was used to assess the estuarine salinity gradient under potential management regimes. The simulations for current conditions are compared to a future 50-year simulation with additional diversions, as well as cases with a variety of diversion options. This modeling analysis shows that without additional action, 50-years of sea-level rise could result in substantial increases in salinity throughout the Mississippi Delta Plain estuaries. This can be largely offset with additional large river diversions which can maintain variable salinity gradients throughout the estuary basins.

Restoring human freedoms: from utilitarianism to a capability approach to wetland restoration in Louisiana’s coastal master plan

“…On the other hand, if they were not to go ahead, there would have to be some way of ensuring that environmental goals were also met. For example, studies have shown that in the absence of diversions, the salinity line will continue to move landwards causing further problems for fishers in the future (White et al, 2019).…”

Investigation of Spatial and Temporal Salinity Distribution in a River Dominated Delta through Idealized Numerical Modelling

“…This is especially true for the Louisiana wetlands and the Mississippi River Delta (Visser et al 2013) where the majority of vegetation species (e.g. Sagittaria latifolia, Sagittaria lancifolia, Phragmites australis) survive in conditions less than 2 psu (White et al 2019).…”

Influence of Key Environmental Drivers on the Performance of Sediment Diversions

“…Construction of dams along major riverine systems have reduced the sediment supply and increased the likelihood of coastal wetland systems and deltas to be drowned by rising seas and sinking land [3]. Extensive research and analyses have been carried out to evaluate the efficacy of various restoration approaches and strategies [4][5][6][7]. Restoration approaches have been extensively deployed [5] to enhance the resiliency of the coastal ecosystems against these challenges.…”