TOTAL DESTRUCTION OF HOLLY BEACH, LA DURING HURRICANE RITA: WHY LOUISIANA'S CHENIER-PLAIN COMMUNITIES ARE AMONG THE MOST VULNERABLE

Hurricane Rita made landfall as a category 3 storm near the Louisiana-Texas border on September 24, 2005. The Gulf-front towns of Holly Beach and Cameron, Louisiana were located within the hurricane's right-front quadrant and suffered near total destruction. In a cooperative program between the U.S. Geological Survey, NASA, University of New Orleans, Louisiana State University and Louisiana Department of Natural Resources, aerial photography and airborne topographic lidar were acquired of the coastal towns and adjacent beach systems of the Chenier Plain, both before and after landfall. These data show erosion and accretion along the coast as well as the near total removal of structures within the impacted communities. The shallow offshore shelf seaward of the Chenier Plain in western Louisiana is conducive to large storm surges along the coast, the surge during Rita reaching approximately 5 m. Beach systems along the Chenier plain are low relief, their peak elevations generally rising no higher than ~ 2 m above mean high water. As a consequence, during Rita, the entire beach system was not overwashed in the classic sense of waves periodically overtopping a berm or dune, but was continuously submerged, as characterized by the ‘inundation regime' of Sallenger (2000). In Holly Beach, preliminary analyses of lidar data show that the shoreline retreated on average ~ 18 m, and the beaches lost significant quantities of sand, lowering beach elevations in places >1 m. The low relief of beach systems, coupled with the potential for high storm surges, makes the Chenier Plain of Louisiana one of the United States' most vulnerable coasts to extreme storms.