The Category 4 hurricane will also send sea waters over about 15 percent of the state’s dunes, “with less extensive erosion in nearby states,” the agency said in a news release, citing its “coastal change” experts. The storm could cause “continuing damage” to mid-Atlantic beaches and dunes if, as expected, it moves slowly after landfall.
On Tuesday, the USGS coastal change forecast model also predicts erosion at “53 percent of Virginia’s beaches, 36 percent of Georgia’s beaches, 29 percent of South Carolina’s beaches and 4 percent of Maryland’s beaches,” officials said. Overwash, in which the storm surge waters wash over the beach and dunes, is “predicted as very likely for 20 percent of beaches in Virginia, 15 percent in North Carolina, 12 percent in South Carolina, and 3 percent in Georgia,” according to the government.
“Our forecast is for Florence to cause a long-lasting coastal erosion process with more than one set of impacts to the Mid-Atlantic beaches,” research oceanographer Kara Doran said in the release. She leads the USGS coastal change hazards storm team based in St. Petersburg, Fla.
Expect “erosion at the base of the dunes from Georgia through Virginia,” according to Doran.
“In most places, it is not likely to overtop that protective row of dunes and cause damage to the communities and natural areas behind them – at least not at first,” Doran said in the news release. “But if the storm lingers, and if high surge, higher than normal tides and strong waves persist over a period of days, the likelihood increases that the dunes could be overtopped and flooding could occur behind them.”
The government has used the USGS coastal change forecast model since 2011 and said in the news release that the model is “continually being improved.”
The model factors in storm surge predictions from the National Hurricane Center and wave forecast models from the National Oceanic and Atmospheric Administration. It then takes into account information about beach slopes and dune heights “to predict how high waves and surge will move up the beach, and whether the protective dunes will be overtopped ...” the news release said.
View a real-time map of the USGS predictions at https://marine.usgs.gov/coastalchangehazardsportal.
Joe Marusak: 704-358-5067; @jmarusak