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August 28, 2023

A new U.S. Geological Survey coastal change forecast predicts sandy beaches and dunes along Florida’s west coast are likely to see significant impacts from Tropical Storm Idalia. 

This USGS coastal change forecast for Idalia is a worst case scenario that can provide vital insights 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 forecasting Tropical Storm Idalia will make landfall in Florida August 30 as a major hurricane, and with that, comes the risk of heavy rains and winds and potentially life-threatening storm surge.  

“Our current coastal change forecast is indicating Idalia could produce coastal change impacts to beaches and dunes along the Gulf coast of Florida similar in magnitude to those Hurricane Ian caused last year,” said Kara Doran, a USGS oceanographer and leader of the USGS Coastal Change Hazards Storm Team. “Given the current forecast track and intensity of Idalia, there will be high water levels along the coast from storm surge and waves that will likely cause severe coastal change and hazards for coastal communities.” 

USGS coastal change experts are forecasting Idalia’s waves and surge have the potential to cause 100% of the dunes and beaches along Florida’s west coast from Bonita Springs to Clearwater to experience some level of erosion. Areas north of Clearwater, Florida aren’t included in the forecast since they are mainly comprised of marshes and wetlands, which are not currently a landscape included in USGS coastal change models.  

Approximately 91% of Florida’s dunes along sandy beaches from Bonita Springs to Clearwater could be overwashed. This more severe level of coastal change occurs when water levels reach higher than the top of dunes. 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 most severe level of coastal change is when dunes are inundated - meaning continuously covered by ocean water. This storm effect can cause flooding behind dunes that may impact coastal communities. Currently, 22% of Florida’s dunes and beaches from Bonita Springs to Clearwater are forecasted to become inundated from Idalia.  

USGS coastal change forecasts will continue to be updated as the storm approaches land and real-time coastal change forecasts for individual locations along the coast are available in the Total Water Level and Coastal Change Forecast Viewer. This newer model developed by USGS scientists, in collaboration with NOAA, estimates the location and timing of potential coastal impacts as well as the height of water levels at the shoreline caused by storm surge and waves. This continuously operating model produces six-day forecasts of hourly water levels for almost 3,000 miles of coastline extending from Texas to Maine.  

As the USGS continues to take all appropriate preparedness actions in response to Idalia, those in the storm’s projected path can visit for tips on creating emergency plans and putting together an emergency supply kit. 

Learn more about USGS hurricane science

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