The marsh boundary separating Lake Borgne and the MRGO has undergone both interior and shoreline wetland losses due to subsidence, impacts related to construction and use of the MRGO (i.e., deep draft vessel traffic), and wind-driven waves. Although much of the project area is protected from edge erosion by shoreline protection measures, and since 2009, then MRGO has been deauthorized for deep draft navigation and maintenance, interior wetland loss due to subsidence continues to cause marsh fragmentation and pond enlargement. Wetland loss rates in the project area are estimated to be -0.60 percent a year based on USGS analysis.
The proposed project will create and nourish 634 acres of marsh using dredged sediment from Lake Borgne. Existing high shorelines along Lake Borgne, remnants of previous containment dikes and marsh edge, would be used for containment to the extent practical. Constructed containment dikes would be breached/gapped as needed to provide tidal exchange after fill materials settle and consolidate. The project would create 346 acres of marsh and nourish at least 288 acres of existing fragmented marsh. A target fill elevation of +1.2 feet is envisioned to enhance longevity of this land form. Additionally, 187 acres of vegetative planting will occur within the newly created areas. Due to the presence of existing banklines, dredged slurry overflow could potentially be discharged immediately adjacent to the project polygons, resulting in nourishment of additional areas.
The Shell Beach South Marsh Creation project is located in Region 1, Pontchartrain Basin, South Lake Borgne Mapping Unit, St. Bernard Parish, north bank of the Mississippi River Gulf Outlet (MRGO) in the vicinity of Shell Beach.
This project is on Priority Project List (PPL) 24 and was approved for Phase I Engineering and Design in January 2015.
The Shell Beach South Marsh Creation project sponsors include:
- Federal Sponsor: U.S. Army Corps of Engineers
- Local Sponsor: Coastal Protection and Restoration Authority