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Hurricane Irma removed approximately 5 million cubic meters of sand from Florida’s Atlantic beaches, making them more vulnerable to future storm impacts. Because of the magnitude of changes due to Irma, existing coastal hazard assessments that are relied upon by federal and state coastal managers must be updated using post-storm lidar-derived coastal elevations which reflect the current vulnerability of the coast to erosion during hurricanes. These products include: (1) scenario-based assessment of storm-induced coastal erosion and (2) real-time forecasts of coastal water levels.
Scenario-based assessments of potential coastal change
The assessment methodology is based on a storm-impact scaling model that uses observations of beach morphology combined with sophisticated hydrodynamic models to predict how the coast will respond to the direct landfall of extreme storms. Storm-induced water levels, due to both surge and waves, are compared to beach and dune elevations to determine the probabilities of three types of coastal change (1) collision (or dune erosion) - occurs when the dune toe is eroded by waves and surge, (2) overwash - occurs when the sand is transported landward over the beach and dune by waves and surge, and (3) inundation - occurs when the beach and dune are completely and continuously submerged by surge and wave setup. The assessments will be updated using post-Irma beach and dune elevations to describe how coastal vulnerability to storms will vary in the future. Updated assessments will be publicly available in the Coastal Change Hazards Portal where users can download and interact with the scenarios for their area of interest. More information can be found on the National Assessment of Coastal Change Hazards webpage.
Operational total water level and coastal change forecasts
The USGS National Assessment of Coastal Change Hazards project is working with the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP) to combine wave predictions from the Nearshore Wave Prediction System (NWPS) with USGS-derived beach morphology to provide regional weather offices detailed forecasts of wave-induced water levels. The interagency operational model is available at select pilot sites and model forecast can be accessed in the Total Water Level and Coastal Change Forecast viewer. The viewer includes predictions of the timing and magnitude of water levels at the shoreline and potential impacts to coastal dunes.
Return to Assessment of Coastal Impacts and Hazards in Florida and Georgia
Examples of storm impacts on barrier islands
Examples of storm impacts on barrier islandsThis chapter focuses on the morphologic variability of barrier islands and on the differences in storm response. It describes different types of barrier island response to individual storms, as well as the integrated response of barrier islands to many storms. The chapter considers case study on the Chandeleur Island chain, where a decadal time series of island elevation measurements have documentAuthorsNathaniel G. Plant, Kara S. Doran, Hilary F. Stockdon