A new U.S. Geological Survey coastal change forecast predicts sandy beaches and dunes along Florida’s Gulf Coast are likely to see significant impacts from Hurricane Ian, which is expected to make landfall later this week as a major hurricane.
USGS coastal change forecasts provide vital information during coastal storms that can help emergency management officials decide which areas to evacuate, where and when to close coastal roads and where to position clean-up equipment in advance of a storm.
The National Hurricane Center is currently warning of possible life-threatening storm surge along parts of Florida’s Gulf coast for Ian. USGS researchers are forecasting the waves and surge caused by Hurricane Ian are likely to cause 66% of Florida’s Gulf coast dunes along sandy beaches between Marco Island and Anclote Key to be inundated – meaning continuously covered by ocean water. This is the most severe type of storm effect on coastal beaches, with flooding behind the dunes that may impact coastal communities.
“Storms as strong as Ian is forecast to be can result in dramatic changes to the coastline and put coastal communities at risk,” said oceanographer Kara Doran, leader of the USGS Coastal Change Hazards Storm Team. “These forecasts can hopefully help local emergency managers and community leaders determine the most effective plans for keeping people safe.”
The second most severe level of coastal damage, overwash, occurs when water levels reach higher than the top of dunes. Approximately 99% of Florida’s dunes along sandy beaches in the area between Marco Island and Anclote Key are expected to be overwashed by Ian. When a beach is overwashed, sand can be pushed and deposited inland, causing significant changes to coastal landscapes and blocking roadways. Overwash can reduce the height of protective sand dunes, alter beach profiles and leave areas behind the dunes more vulnerable to future storms.
The least severe level of storm damage on sandy shorelines is erosion at the base of sand dunes. In Florida, 100% of the dunes along sandy beach between Marco Island and Anclote Key are projected to face some level of erosion caused by Ian. From the Alabama state border to St. James Island in Florida, 6% of the dunes along sandy beaches are forecast to face some level of erosion.
The most current forecast is always available on the USGS Coastal Change Hazards Portal. Real-time coastal change forecasts for individual locations along the coast are also available in the Total Water Level and Coastal Change Forecast Viewer.
The forecast of Ian’s coastal effects at landfall is based on results of the USGS Coastal Change Forecast model, which has been in use since 2011 and is continually being improved. The model starts with inputs from the NHC’s storm surge predictions and National Oceanic and Atmospheric Administration wave forecast models. It then adds detailed information about the expected landfall region’s beach slope and dune height. The predictions define “very likely” effects as those that have at least a 90% chance of taking place, based on the storm’s forecast track and intensity.
As the USGS continues to take all appropriate preparedness actions in response to Ian, those in the storm’s projected path can visit Ready.gov for tips on creating emergency plans and putting together an emergency supply kit.
