A U.S. Geological Survey coastal change forecast predicts that 52% of Louisiana’s barrier islands and beaches will be inundated – continuously submerged with flooding behind the dunes – by the storm surge from Hurricane Delta. The storm is likely to cause some beach and dune erosion across a wide swath of the central Gulf Coast, with storm waves likely to erode the bases of ocean-facing sand dunes along about 48% of the region’s sandy shorelines.
Scientists and emergency managers can use USGS’s forecasts – produced before major hurricanes and other powerful storms – to plan evacuations, position clean-up equipment to have it ready after the storm. The USGS predicts the storm surge and wave effects will be felt from East Texas through Mississippi, although Delta is not currently predicted to cause erosion of Alabama beaches and barrier islands.
The storm’s expected effects on central Gulf sandy shorelines are similar to those predicted for Hurricane Laura, which made landfall near Cameron, Louisiana Aug. 27, causing extensive erosion. The damage done by Laura makes the area especially vulnerable, said USGS oceanographer Kara Doran, leader of the USGS Coastal Change Hazards Storm Team based in St. Petersburg, Florida.
“Hurricane Laura removed a large volume of sand from Louisiana’s Chenier Plain beaches and offshore barrier islands, which means the coastline behind them has already lost some of its natural protection from storms,” Doran said. “For that reason, Delta’s storm surge is cause for concern.”
Storm surges are increases in ocean water levels above the astronomical tide generated at sea by extreme storms. Surge can have devastating coastal impacts. The National Weather Service is predicting a peak storm surge of 7-11 feet in portions of western Louisiana.
The USGS coastal erosion prediction covers only sandy shorelines, such as beaches and barrier islands, and not marshes, forests or shorelines with seawalls or other armoring. Louisiana has more marshy shorelines and fewer sandy beaches than the other two states, so this prediction applies to a smaller portion of that state’s coast, but the predicted inundation in Louisiana is still significant, Doran said.