From U.S. Geological Survey

As Florida starts to feel the effects of Hurricane Dorian, U.S. Geological Survey coastal change experts have forecast that 80 percent of the sandy beaches from Florida to North Carolina are likely to undergo beach and dune erosion from the powerful storm.

Georgia and South Carolina beaches are projected to face the highest rates of dune erosion, with 100 percent of those states’ beaches likely to suffer some level. About 85 percent of Florida’s beaches and 60 percent of North Carolina’s dunes will also experience erosion from the strong waves and surge generated by Dorian.

Dune erosion is only the first level of damage a major storm like Dorian can cause. As waves and surge reach higher than the tops of dunes, overwash can occur, often transporting large amounts of sand across coastal environments – including roads, depositing sand inland and causing significant changes to the landscape. Overwash is currently predicted as very likely for 59 percent of Georgia dunes, 57 percent of South Carolina dunes, 22 percent of Florida dunes and 9 percent of North Carolina dunes. Overall, 28 percent of the dunes from Florida to North Carolina may experience some level of overwash.

Inundation, the most severe coastal impact, occurs when beaches and dunes are completely and continuously submerged by water. Inundation is forecast as very likely for 9 percent of dunes in both Georgia and South Carolina. North Carolina and Florida are currently not projected to experience any inundation.

The prediction of Dorian’s effects are based on results of the USGS Coastal Change Forecast model, which has been in use since 2011, and is continually being improved. The Coastal Change Forecast model starts with the National Hurricane Center’s storm surge predictions and National Oceanic and Atmospheric Administration wave forecast models as input. The USGS model then adds detailed information about the forecasted region’s beach slope and dune height to predict how high waves and surge will move up the beach, and whether the protective dunes will be overtopped. The forecasts are available at high resolution for all the areas likely to be affected by storm-tides from Hurricane Dorian.

The public can view a real-time map of these coastal change forecasts on the USGS’ Coastal Change Hazards Portal. Emergency managers can use the coastal change forecast to help identify locations where coastal impacts might be the most severe and this data can assist them as they make critical decisions on which areas to evacuate, which roads to use, and where to position heavy equipment for post-storm clean-up.

“Our coastal change forecast is for Dorian to cause long-lasting and widespread erosion of dunes from Florida through the Carolinas,” said research oceanographer Kara Doran, leader of the USGS Coastal Change Hazards Storm Team.

“When hurricanes move slowly and remain at sea for long periods of time, they tend to build up large storm waves,” Doran said. “These waves can travel hundreds of miles and begin causing dune erosion well before the storm arrives, on shorelines that are far from the center of the storm. And with Dorian now moving very slowly, and forecast to stay offshore and move slowly up the coast, high surge, and strong waves are likely to persist over a period of days. So the likelihood increases that the dunes could be overtopped and flooding could occur behind them as they are eroded by wave action.”

If Hurricane Dorian, which as of Monday morning was a Category 5 storm, stays on the course forecast by the National Hurricane Center, coastal change from the storm is likely to be most severe along Georgia and South Carolina coastlines where storm surges are projected to reach 6-10 feet.

Other areas likely to receive significant coastal changes include Florida from Jupiter to Cape Canaveral, where storm surges are expected to reach 3-6 feet, and from Cape Hatteras, North Carolina south along the coast to the state line where storm surges could reach 3 to 7 feet.

While the final projections for Hurricane Dorian will continue to change, Dorian is forecasted to remain a powerful storm for several days and is likely to damage many parts of the South-Eastern Coastline.

 

The USGS continues to take all appropriate preparedness and response actions as Hurricane Dorian approaches the United States. People potentially affected by the storm can visit http://www.ready.gov/ or http://www.listo.gov/ for tips on creating emergency plans and putting together an emergency supply kit.