Florence hurricane may cause erosion in Southeast Atlantic beaches

U.S. Geological Survey (USGS) models predict that Florence Hurricane can cause beach erosion along 3/4 of North Carolina among other areas.

Florence, a Category 4 hurricane, can provoke landfalls and influence about 15% of North Carolina's dunes. USGS team of Coastal Change Hazards investigates 2 different forecasts of coastal erosion, which combined together can evaluate the effect of the storm on the coast. In the first simulation, coast-wide beach impact is analyzed in order to determine the potential of dune erosion and overwash for a large area. In the second application, an experimental model that predicts the characteristics of elevated water levels at the coastline over long periods is utilized.

The impact of the hurricane on landfalls is predicted by the USGS Coastal Change Forecast model that is evolving since 2011. The simulation operates by using National Hurricane Center's storm surge predictions and National Oceanic and Atmospheric Administration wave forecast models as input. Then, detailed information about the geometry of the beach slope and dune heights is imported. This way, the course of high waves can be defined. Due to fact that these forecasts are depended on the storm-surge predictions, they often change. The simulation predicted erosion at the base of protective dunes on 75%, 53%, 29% and 4% of North Carolina's, Virginia's, South Carolina's Maryland's beaches, respectively.

Nevertheless, the storm has another significant impact, other than erosion, on landscape. If waves propagate over the top of dunes, overwash occurs. During this procedure, large sand deposits are transported across coastal area altering the landscape. Current predictions show that overwash can occur in 20% of beaches in Virginia, 15% in North Carolina, 12% in South Carolina and 3% in Georgia.

Kara Doran, a research oceanographer and leader of the USGS Coastal Change Hazards Storm Team based in St. Petersburg, Florida stated: "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. As Florence makes landfall its storm surge will cause some erosion at the base of the dunes from Georgia through Virginia. 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. 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."

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