Forecasting landscape effects of Mississippi River diversions on elevation and accretion in Louisiana deltaic wetlands under future environmental uncertainty scenarios

• Published in: Estuarine, coastal and shelf science Vol. 138; pp. 57 - 68
• Main Authors: Wang, Hongqing, Steyer, Gregory D., Couvillion, Brady R., Rybczyk, John M., Beck, Holly J., Sleavin, William J., Meselhe, Ehab A., Allison, Mead A., Boustany, Ronald G., Fischenich, Craig J., Rivera-Monroy, Victor H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2014; Elsevier
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; deltaic wetlands; Fundamental and applied biological sciences. Psychology; sea-level rise; sediment diversion; subsidence; surface elevation; Synecology; vertical accretion; Louisiana; United States; North America; America; deltaic wetlands; subsidence; surface elevation; sea-level rise; sediment diversion; vertical accretion; Vertical; Subtropical zone; Brackish water environment; Uncertainty; Accretion; Landscape; Sea level; Sediments; River basins; Forecasting; Mississippi Basin; Wetland
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2013.12.020

Large sediment diversions are proposed and expected to build new wetlands to alleviate the extensive wetland loss (5000 km2) affecting coastal Louisiana during the last 78 years. Current assessment and prediction of the impacts of sediment diversions have focused on the capture and dispersal of both water and sediment on the adjacent river side and the immediate outfall marsh area. However, little is known about the effects of sediment diversions on existing wetland surface elevation and vertical accretion dynamics in the receiving basin at the landscape scale. In this study, we used a spatial wetland surface elevation model developed in support of Louisiana's 2012 Coastal Master Plan to examine such landscape-scale effects of sediment diversions. Multiple sediment diversion projects were incorporated in the model to simulate surface elevation and vertical accretion for the next 50 years (2010–2060) under two environmental (moderate and less optimistic) scenarios. Specifically, we examined landscape-scale surface elevation and vertical accretion trends under diversions with different geographical locations, diverted discharge rates, and geomorphic characteristics of the receiving basin. Model results indicate that small diversions (<283 m3 s−1) tend to have limited effects of reducing landscape-scale elevation loss (<3%) compared to a future without action (FWOA) condition. Large sediment diversions (>1500 m3 s−1) are required to achieve landscape-level benefits to promote surface elevation via vertical accretion to keep pace with rising sea level.