Landscape evolution of the oil spill mitigation sand berm in the Chandeleur Islands, Louisiana

Abstract : The failure of the Macondo-252 well and explosion of the Deepwater Horizon oil rig resulted in the release of approximately 185 million gallons of crude oil into the Gulf of Mexico (Wilde and Skrobialowski 2011). As part of the emergency response plan, the Louisiana Office of Coastal Protection and Restoration proposed (and subsequently constructed) sand barriers to reduce the amount of oil from reaching the Chandeleur Islands and inland wetlands; thereby protecting these sensitive ecosystem resources. This study was conducted to provide general measures of the sand berms resilience, performance, and potential impacts to the Chandeleur Islands. To satisfy these objectives, Geographic Information System (GIS) and remote sensing techniques were used to quantify changes in sand berm areal extent over time; provide shoreline, habitat, and landscape assessments of the Chandeleur Islands; and assess elevation changes and potential reworking of berm sediment into the island system. The sand berm provided short-term benefits and short-term advancement of the islands shoreline position, but the majority of those benefits were ephemeral since the berm experienced rapid degradation. Data show that the degradation of the berm began within 30 days post-construction, and the berm was largely eroded within 18 months post-construction. The speed and degree of degradation were primarily the results of Tropical Storm Lee (5 September 2011) and Hurricane Isaac (28 August 2012), and the construction of the berm in high-energy open water environments. Additionally, berm sediments were redistributed to areas of known submerged aquatic vegetation communities, potentially impairing these critical habitats. Ultimately, the berm was not successful in providing a barrier to retard oil from reaching the island or oil migrating into Chandeleur Sound and beyond.