Opportunity
Some 48km southeast of New Orleans lies the Biloxi Marsh estuary, a network of coastal wetlands totalling about 85,000 hectares. In addition to the Biloxi Wildlife Management Area located there, the wetland helps protect the city from storm surges. Over time, lack of bank stabilisation caused the width of the Mississippi River–Gulf Outlet Canal (MRGO) to expand in some areas from 152m to 823m. Saltwater intrusion from the MRGO affected the Biloxi Marsh, and the building of levees along the Mississippi prevented the marsh from being replenished with river sediment.
Solution
The Louisiana Coastal Protection and Restoration Authority was interested in constructing a demonstration project that utilises living shoreline solutions. We analysed 34km of coastal fringe to develop an understanding of shoreline change rates, morphology, and coastal processes. We then evaluated nine living shoreline concepts based on structural stability, shoreline protection performance, cost, and constructability. Using 3D computational fluid dynamics or CFD modelling tools, our engineers analysed these alternatives to determine their ability to reduce wave energy as it passes through the structure.
Outcome
The project will provide self-sustaining protection to almost 5km of shoreline in St Bernard Parish, reducing erosion and moderating the impact of waves and storm surges. In addition, it will stimulate the growth of oysters and increase biodiversity in the area. Oyster reefs filter and improve the quality of seawater, provide nursery habitat for fish and shellfish, provide food for predatory fish such as flounder, drum, and speckled trout, and mitigate nutrient loading, eutrophication, and hypoxia.