SEDIMENT TRANSPORT AND DEPOSITION STUDIES ALONG LOUISIANA’S GULF COAST

Abstract:

Anthropogenic constraints placed upon the Lower Mississippi River (LMR) in the forms of dam construction, levee construction and river flow control systems have decreased sediment loads by approximately 50% delivered to the Northern Gulf of Mexico (NGoM) in the past century. The decrease in sediment is one of leading factors causing a wetland loss crisis in Louisiana. Maintaining and restoring barrier islands along Louisiana’s Gulf Coast (LGC) is vital to minimize storm surge that causes salt water intrusion, damaging the coastal freshwater marshes, as well as decreasing flooding in the coastal regions. A cost benefit analysis performed on Coastal Protection and Restoration Authority’s (CPRA) Master Plan 2012 for long term land building indicated that Barrier Island Restoration is the third most cost-effective type of restoration considered in the plan with approximately 1.7 billion U.S. dollars spent over a 50yr period to build or maintain approximately 39 - 52 km².

High-quality sand has been targeted for beach and dune restoration efforts in Louisiana with several offshore sites identified. Several of them have been already dredged for this purpose, but questions remain about the finiteness surrounding this precious resource. Understanding sediment deposition occurring along LGC will better identify if the resource is finite or if it requires longer timescales to replenish. A comprehensive literature review and synthesis of published papers is examined detailing sediment transport processes on LGC along with sediment deposition studies to better understand where fluvial sediment is deposited and then re-suspended and transported to deeper waters. This study aims at understanding sedimentation and sediment transport processes under the impacts of wind, wave, tide, current and morphology in the NGoM along the LGC to aid in management decisions of valuable high-quality sand resource.