Hurricane Irma - Forecast and Documentation of Coastal Change

Science Center Objects

Hurricane Irma coastal change forecast and pre- and post-storm photos documenting coastal change.

Hurricane Irma impacted the Gulf coast of Florida, as well as the Southeast Atlantic coastlines of Florida, Georgia, and South Carolina from September 10–11, 2017. Storm surge reached 1 to 2.5 meters above predicted tides. Offshore wave heights in excess of 6 meters were observed on both the Gulf and Atlantic coasts of Florida. These large waves contributed an additional 1 to 5 meters of wave runup at the shoreline. The combined effects of surge and storm-induced wave runup created elevated total water levels at the shoreline, causing extensive erosion of the beach and dunes. 

Response activities included:

  • Forecast of potential coastal change (see next section)
  • Pre-and post-storm photos documenting coastal change (see galleries below)
  • Drone surveys of Pinellas County, Florida, beaches (available soon)
  • Comparison of pre- and post-storm lidar topography and coastal change (available soon)

Forecast of Potential Coastal Change

The coastal change forecast model predicts the probability of where and how primary sand dunes along the coast will be impacted by water levels during a storm. This includes the combined effect of surge and wave runup. The color band closest to the shoreline is the probability of dune erosion, the middle color band is the probability that sand dunes will be overtopped by waves during the storm, and the outer color band is the probability that the sand dunes will be completely inundated/flooded. The model forecast is available on the Coastal Change Hazards Portal and more information about the model can be found here: https://www.usgs.gov/centers/spcmsc/science/scenario-based-assessments-used-coastal-change-hazard-forecasts

Hurricane Irma-response page intro slide

Predicted probabilities of dune erosion (inner strip), overwash (middle strip), and inundation (outer strip) for Hurricane Irma. Pictures in above illustration are representative of coastal change observed during past storm events. The model forecast is available on the Coastal Change Hazards Portal and more information about the model can be found at https://www.usgs.gov/centers/spcmsc/science/scenario-based-assessments-used-coastal-change-hazard-forecasts. Pictures of actual coastal change caused by Hurricane Irma are shown below. (Public domain.)

Pre- and Post-Storm Photo Comparisons

The photos pairs below show aerial photos from June 2015 and similar imagery taken a few days after Hurricane Irma’s landfall (https://storms.ngs.noaa.gov/). The photos show how the coast was impacted by the storm are used to validate the forecast model.

Florida Keys

SouthWest Florida 

East Florida 

Research is part of the National Assessment of Storm-Induced Coastal Change Hazards project.