Over the past century, >5000 km² of the Mississippi delta has been lost, and mitigation efforts are underway to ameliorate the damaging impacts of this loss. River-sediment diversions proposed by the Louisiana Coastal Protection and Restoration Authority have great potential to restore subsiding wetlands within receiving basins (Mid-Barataria and Breton Sound), though it is crucial to be certain the basins can support the future increase in water and sediment flux. Here, an investigation into deltaic development using sediment extraction and dating methods (radiocarbon and Optically Stimulated Luminescence) reveals the heterogenous lithology of the Mid-Barataria receiving basin. Most of the underlying architecture consists of St. Bernard delta lobe deposits, with somewhat minor contributions from the Plaquemines delta lobe located proximal to the modern river. Marshes within the basin have been maintaining elevation with relative sea level rise (RSLR) for thousands of years, as evidenced by continuous peat and organic-rich mud deposits in many locations since 2-2.5 ka.

Using 210Pb and 137Cs radiochemistry, marshes on top of paleochannel sands exhibit greater vertical accretion rates (VAR) over the past 100 years than marshes overlying muddy substrates (1.29 cm/yr, versus 0.95 cm/yr, respectively), but further analyses are needed to verify. Average long-term VAR from this and other studies show these marsh platforms are currently keeping pace with RSLR rates, but the bays are not (VAR 0.63 cm/yr). With a lack of new allochthonous sediment provided to the basin, inorganic material for the marshes is scavenged from bay bottoms and the coastal ocean during storm events and sourced from eroding marsh edges. This underscores the importance of a multi-prong approach to coastal restoration that encompasses a combination of sediment diversion, shoreline protection, and marsh creation projects.

Bio: Carol Wilson is an Associate Professor in the Dept of Geology and Geophysics at Louisiana State University with an expertise of quantifying ecophysical processes that shape deltaic and coastal wetlands--specifically how biology, geology, and water interact to create and maintain functioning landscapes. After completing her BS in Biology and Chemistry at the University of New Orleans, Carol utilized these skills to understand wetland loss in SE Louisiana marshes and quantified the geomorphic evolution of subsiding and eroding marsh shorelines. She completed her PhD from Boston University studying the ecogeomorphic evolution of marshes along the east coast of the US (Massachusetts, South Carolina, and Georgia), and worked as a Post-doctoral scholar on the tide-dominated delta of the Ganges Brahmaputra in Bangladesh while at Vanderbilt University. She is heavily involved in research projects in the Mississippi and Ganges-Brahmaputra deltas, and is currently serving on CWPPRA’s Academic Advisory Group for wetland restoration/mitigation.

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