RAPID: Connecting the historic 2011 Mississippi River flood to marsh sedimentation on the Delta

The project aims to determine the impact of a geologically significant flood event on coastal sedimentation patterns and rates. Determining transport pathways will enable researchers from University of Pennsylvania, University of Mississippi, and the U.S. Geological Survey to connect the dots between river dynamics, coastal dynamics, and marsh maintenance. Two contrasting river plumes will be studied?-that of the Mississippi River itself, which is expected to disperse sediment into the Gulf and not contribute greatly to wetland development because of its narrow, focused jet, and that of the Atchafalaya River, which is expected to spread diffusely across the landscape and be more prone to deposit sediment to nourish wetlands.

The research will make use of satellite data, physical sampling, and numerical modeling. Measurement approaches are (1) analysis of satellite data on sea surface temperature, color, and height; (2) collection of sediment samples at the outlet of the Mississippi River using a boat survey with acoustic dopplar, surface sediment samples, and bed grab samples, and (3) measurement of marshland sediment accretion rates once the floodwaters begin to subside. New theory recently developed by two of the PIs for estimating mixing rates and sedimentation patterns in coastal Louisiana resulting from the flood will be captured in a model. The results of the model will be compared with measured plume dynamics off the Mississippi River, and sampled marsh sediments from the shelf bottom and marsh surfaces along the Mississippi and Atchafalaya Rivers, to enhance understanding of how the Mississippi Delta functions as a sediment dispersal system.

There is consensus that protecting and expanding coastal marshes is vital for coastal Louisiana but much less agreement on how to do it. Scientific understanding of marsh building needs to be bolstered before it can inform this debate. This project seizes a unique opportunity to examine constrasting modes of sediment dynamics in two plumes from the historic 2011 Mississippi floods, and aims to enhance the scientific basis for delta restoration that will become increasingly important in the years to come.