From 1932 to 1990, the Caernarvon Mapping Unit lost 14,240 acres of its marsh. Prior to Hurricane Katrina, the greatest loss documented occurred between 1956 and 1974 and coincided with Hurricane Betsy and extensive canal building. Hurricane Katrina devastated the area resulting in substantial marsh loss. According to USGS Open File Report (2006-1274), approximately 39 square miles of marsh around the upper and central portions of Breton Sound were converted to open water by storm related scouring or submergence of the marsh. Because the framework of the marsh has been degraded, suspended sediments provided by the diversion move through the system and fall out where velocities are reduced such as in Big Mar and Lake Lery.
The goal is to create terraces in the shallow open water areas south of Big Mar within the Caernarvon Diversion outfall area. Terraces will reduce wave fetch in the large open water areas and promote conditions conducive to growth of marsh vegetation and submerged aquatic vegetation. Additional benefits may be achieved through capturing suspended sediments. Marsh creation is also proposed to reestablish the western shoreline of Lake Lery in association with the Lake Lery Shoreline Restoration Project (BS-16).
Approximately 65,000 linear feet of terraces (37 acres) will be constructed with in-situ material to reduce fetch and turbidity and capture suspended sediment. Sediments will be hydraulically dredged from Lake Lery and pumped via pipeline to create and restore approximately 334 acres of marsh in the project area.
The Terracing and Marsh Creation South of Big Mar project is located about 5 miles south of Violet, LA in Region 2, Breton Sound Basin in Plaquemines Parish, south of Big Mar and west of Lake Lery.
This project is on Priority Project List (PPL) 22. In 2013, BS-24 was approved for Phase I Engineering and Design.
The Terracing and Marsh Creation South of Big Mar project sponsors include:
- Federal Sponsor: U.S. Fish and Wildlife Service
- Local Sponsor: Coastal Protection and Restoration Authority