OPTIMIZATION OF THE CLOSURE OF A BREACHED BARRIER ISLAND IN THE GULF OF MEXICO

A chain of barrier islands in the Gulf of Mexico reduces storm and hurricane impacts along the Mississippi coast. Ship Island, one of the largest islands of this chain, was breached by hurricanes Camille and Katrina creating a 5.5 kilometer wide gap. US Army Corps of Engineers plans to restore the island nourishing 15 million cubic meters of sand. Extensive modeling studies were carried out to support the environmental impact assessment and to optimize design. The main objective of these studies was to determine the impact of the restored island on the environment. The possible increase of sedimentation rates in the adjacent navigation channel connecting a major port to the Gulf of Mexico was of particular interest. The Delft3D models, calibrated on measurements of waves, tidal levels and currents, were used to estimate the annual sediment transport rates. These models were subsequently applied to optimize the design of the closure of Camille Cut. The optimum construction sequence was established. Sediment losses from the fill, and the impact of turbidity plumes on the nearby sea grass fields were determined.