St. Petersburg Coastal and Marine Science Center

National Assessment of Hurricane-Induced Coastal Erosion Hazards: Gulf of Mexico

Introduction

Sandy beaches provide a natural barrier between the ocean and inland communities, ecosystems, and resources. However, these dynamic environments move and change in response to winds, waves, and currents. During a hurricane, these changes can be large and sometimes catastrophic. High waves and storm surge act together to erode beaches and inundate low-lying lands, putting inland communities at risk. A decade of USGS research on storm-driven coastal change hazards has provided the data and modeling capabilities to identify areas of our coastline that are likely to experience extreme and potentially hazardous erosion during a hurricane.

The analysis 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 category 1-5 hurricanes. Hurricane-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 – dune toe is eroded by waves and surge, (2) overwash - sand is transported landward over the beach and dune by waves and surge, and (3) inundation - beach and dune are completely and continuously submerged by surge and wave setup. As new beach morphology observations and storm predictions become available, this analysis will be updated to describe how coastal vulnerability to storms will vary in the future.

Probabilities of Coastal Change
(click to use interactive map)

Key Findings

Percentage of Gulf of Mexico sandy beaches very likely (probability > 0.9) to experience erosion associated with collision, overwash, and inundation during category 1-5 hurricane landfall.
	Hurricane Intensity Category
	1	2	3	4	5
collision (dune erosion)
US Gulf of Mexico	99	100	100	100	100
Texas	99	100	100	100	100
Louisiana	100	99	100	100	100
Mississippi	100	100	100	100	100
Alabama	100	100	100	100	100
Florida Panhandle	98	99	100	100	100
Florida West Coast	99	100	100	100	100
overwash
US Gulf of Mexico	71	85	92	97	98
Texas	61	75	88	98	99
Louisiana	95	99	100	100	100
Mississippi	96	100	100	100	100
Alabama	69	99	100	100	100
Florida Panhandle	47	74	83	89	93
Florida West Coast	98	99	100	100	100
inundation
US Gulf of Mexico	27	58	73	83	89
Texas	20	54	62	73	85
Louisiana	62	86	95	100	100
Mississippi	35	93	100	100	100
Alabama	4	29	74	99	100
Florida Panhandle	5	25	51	69	77
Florida West Coast	42	91	99	99	99

During a category 1 hurricane landfall in the Gulf of Mexico, waves increase water levels at the shoreline by 170% above surge alone. The predicted wave-driven component of shoreline water levels was 2.8 m, high enough to overwash the mean dune elevation along the U.S. Gulf coast, even without surge.
For modeled conditions representing category 1 hurricane landfall, 99% of sandy beaches along the U.S. Gulf of Mexico coast are very likely (P>90%) to experience dune erosion, 71% are very likely to overwash, and 27% are very likely to inundate.
For category 3 hurricane landfall, 92% of sandy beaches are very likely to overwash.
For category 5 hurricane landfall, 89% of sandy beaches are very likely to inundate.
Hurricanes are not required for significant coastal change in the Gulf region. Waves associated with tropical storms and winter cold fronts provide sufficient energy to put low-elevation beaches and dunes at risk to erosion.

Full Report

For more information, see USGS Open-File Report 2012-1084.

Download Data

ArcGIS Shapefiles:

Probabilities of coastal change for category 1-5 hurricanes (310 KB .zip)
Morphology data (dune crest, dune toe, beach slope, shoreline) (302 KB .zip)
Hydrodynamic data (storm surge, wave runup, wave height) (359 KB .zip)

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U.S. Department of the Interior | U.S. Geological Survey
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Page Last Modified: May 09, 2013 @ 02:12 PM (JSG)