The Mississippi River Flood of 2008: Sediment Dynamics and Implications for Coastal Restoration

The Mississippi River, measured at Reserve, LA, reached flood stage on April 7, 2008 and remained at that level for nearly a month. Records from the USGS indicate that this was the highest water level since 1973, and prompted numerous flood control measures in the region. To understand if high flow events, such as these, have the potential to deliver much needed sediments to deteriorating coastal wetlands in the lower Mississippi River, this study investigated the recently deposited sediments in two coastal systems in the lower Mississippi River: The Pass-a-Loutre Preserve and West Bay. The former is an area of wetlands and open water that has experienced a combination of accretion and erosion in recent decades while the latter is an area of open water where a river diversion was recently constructed with the goal of creating subaerial environments. Preliminary results indicate that this flood deposited a layer of sediment that ranged from 1s cm to several 10s of cm thick; and that thickness could vary with thickness from the river. Recent sediment deposition is being confirmed using textural analysis, x-radiographs, and Be-7, a short-lived, particle reactive radionuclide. These findings, while preliminary, suggest that coastal environments can accrete at rates greater than regional rates relative sea level rise during episodic high-water events if pathways are present to deliver sediment rich water to critical embayments.