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St. Petersburg Coastal and Marine Science Center > National Assessment of Storm-Induced Coastal Change Hazards > Hurricane Nate

National Assessment of Storm-Induced Coastal Change Hazards

Hurricane Nate Storm Response

Pre- and Post-Storm Photo Comparisons - Gulf Coast

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: https://marine.usgs.gov/coastalchangehazardsportal/ and more information about the model can be found here: https://coastal.er.usgs.gov/hurricanes/assessments/background.php

Below is an initial comparison of imagery collected by the National Oceanic and Atmospheric Administration (NOAA) in 2017 with similar imagery taken a few days after Hurricane Nate’s landfall (https://storms.ngs.noaa.gov/). These photos provide information about how the coast was impacted by the storm and can be used as validation for the model.

    Predicted probabilities of dune erosion (inner strip), overwash (middle strip), and inundation (outer strip) for Hurricane Nate. Pictures are representative of coastal change observed during past storm events.
Predicted probabilities of dune erosion (inner strip), overwash (middle strip), and inundation (outer strip) for Hurricane Nate. Pictures are representative of coastal change observed during past storm events. [larger version]

Location Map
Locations of observed coastal change due to Hurricane Nate.



pre- and post-storm photos
Location 1: Elevated water levels and high waves during Hurricane Nate overtopped low spots in the line of dunes near Fort Morgan, Alabama. The fan-like sand deposits behind the dunes indicate that sand was transported landward, while the sandbar offshore indicates that sand was also transported seaward during the storm. The predicted probability of overwash for this location was 84%. [larger version]



pre- and post-storm photos
Location 2: The low-elevation west end of Dauphin Island is especially vulnerable to storms and has been impacted by multiple storm events over the last decade. Storm surge and waves from Hurricane Nate overtopped and cut through the line of dunes in front of the road, depositing sand across the road in overwash fans. The predicted probability of overwash in this location was 95%. [larger version]



pre- and post-storm photos
Location 3: Elevated water levels during Hurricane Nate overtopped and eroded the rock barrier that was constructed to close the breach that formed in Dauphin Island during Hurricane Katrina. The predicted probability of inundation in this location was 96%. [larger version]



pre- and post-storm photos
Location 4: The low elevation spit on the far western end of west Dauphin Island was breached during Hurricane Nate. The predicted probability of inundation was 54%, likely due to the inclusion of the higher elevation dunes to the east of the spit in the 1-km alongshore prediction area. [larger version]



pre- and post-storm photos
Location 5: Elevated water levels during Hurricane Nate overtopped the low dunes on Petit Bois Island. The predicted probability of overwash for this location was 99%. [larger version]



pre- and post-storm photos
Location 6: The low-elevation east end of Horn Island was inundated by waves and storm surge during Hurricane Nate. The predicted probability of inundation for this location was 98%. [larger version]



pre- and post-storm photos
Location 7: Low elevation dunes on East Ship Island were inundated by waves and surge from Hurricane Nate. Sand was transported across the entire island, covering vegetation and filling in ponds. The predicted probability of inundation in this location was 98%. [larger version]



pre- and post-storm photos
Location 8: On the east end of West Ship Island, dunes were overtopped by elevated water levels during Hurricane Nate. The predicted probability of overwash for this location was 100%. [larger version]

St. Petersburg Coastal and Marine Science Center > National Assessment of Storm-Induced Coastal Change Hazards > Hurricane Nate

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Page Last Modified: October 18, 2017 10:44 AM (JSG)

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