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Coastal and Marine Geology Program > Hurricane Impacts on the Coastal Environment

Hurricane Impacts on the Coastal Environment

USGS Fact Sheet

Color-enhanced satellite image of the eye and circular storm patterns of Hurricane Andrew.
[larger version]
"In terms of insured losses, Hurricane Andrew is the most severe catastrophe in the Nation's history. Prior to the arrival of Andrew, the U.S. Geological Survey (USGS), in cooperation with the Louisiana Geological Survey (LGS), acquired an extensive body of information and data on the behavior and long-term erosion of Louisiana barrier islands. As a result, we have a clear understanding of pre-storm conditions in this area; Andrew provided an opportunity to learn in detail the impact of a very large storm on Louisiana coastal environment."

- Dr. Abby Sallenger, U.S. Geological Survey
Of the most severe catastrophes in the Nation's history, hurricanes account for two-thirds of the insured property losses.

During August and September 1992, Category 4 hurricanes, with sustained winds between 131 mph and 155 mph, made four landfalls in the United States and its territories. The resulting damage in south Florida, Louisiana, Guam, and Hawaii was in the tens of billions of dollars. Hurricanes and extreme extratropical storms cause elevated sea level, known as storm surge, and extensive shoreline erosion and other geologic effects leading to the loss of property and life. We cannot yet predict with confidence the magnitude of this erosion and the extent of geologic impacts. The variability of shoreline types, including barrier islands of Louisiana, mangroves of south Florida, coral reefs and pocket beaches of Hawaii and Guam, make predictions especially difficult.

Insured Losses
Year Event Losses
1992 Hurricane Andrew 15.50
1906 San Francisco Earthquake 5.07*
1989 Hurricane Hugo 4.20
1871 Chicago Fire 1.83*
1992 Hurricane Iniki 1.60
1991 Oakland Fire 1.20
1989 Loma Prieta Earthquake 0.95
1983 Winter Storm and Freeze (41 States) 0.88
1992 Los Angeles Riots 0.78
1979 Hurricane Frederic 0.75
1983 Hurricane Alicia 0.68
1990 Wind and Hail Storm - Colorado 0.63
1965 Hurricane Betsy 0.52
* adjusted to 1990 dollars
Bar graph showing that hurricanes are responsible for 67% of insured losses.
Above - The thirteen most-costly insured catastrophes in U.S. history (listed at left) are predominantly hurricanes, according to the Property Claims Services Division, American Insurance Services Group; and the Insurance Information Institute.

Left - Insured losses are given in billions of dollars.

Rapid-response surveys of Hurricane Andrew's impact zone conducted by the USGS reveal surprising results.

For Hurricane Andrew, the loss of human life and property is well documented. However, the environmental effects are less well-known. In south Florida, Hurricane Andrew completely stripped vegetation from the northernmost Florida Keys. In the case of mangrove trees, defoliation and wood damage killed large old stands along the shoreline.

Area studies reveal the immense change brought about by these storms.

In Louisiana, Dr. Shea Penland and his colleagues at the LGS reported that Andrew stripped sand from 70 percent of the barrier islands leaving exposed old coastal marsh. More than 80 percent of oyster reefs behind the barrier islands were smothered by a 0.3-0.9-meter thick blanket of sediment. More than 70 kilometers of valuable dune habitat providing storm protection to estuaries, wetlands, and the coastal population were destroyed. In Hawaii, Dr. Charles Fletcher and his colleagues at the University of Hawaii cooperated with USGS scientists in a study of the effects of Hurricane Iniki, the most powerful hurricane to strike the Hawaiian Islands this century. They report that Iniki caused massive beach-face erosion and overwash of the coastline which penetrated up to 300 meters reaching elevations of nearly 9 meters.

Seafloor change from the 1930's to the 1980's for the region of coastal Louisiana hardest hit by Hurricane Andrew.
Seafloor change from the 1930's to the 1980's for the region of coastal Louisiana hardest hit by Hurricane Andrew shows historical patterns of seafloor erosion and accretion. This information was collected as part of the USGS's Louisiana Barrier Island Erosion Study, and will be used as a baseline to determine the effect of Hurricane Andrew on coastal areas already undergoing rapid change. [larger version]

USGS scientists have used historical data to show that Louisiana is eroding rapidly.

The Louisiana barrier island shoreline is eroding at a rate, in some places, exceeding 20 meters per year as a result of both hurricanes and normal processes. The land is subsiding because of compaction of the Mississippi delta sediments. The net effect of subsidence is that sea level is rising at a rate of about 1 centimeter per year, ten times the world rate. USGS scientists take advantage of this natural laboratory to study erosion and deposition patterns resulting from sea-level change. The Louisiana barrier islands protect productive estuarine and wetland environments that support a $10 billion per year fishing industry. Erosion of the barrier islands is so severe that their ability to function as effective buffers for the prevention of wetlands loss has been dramatically reduced. Louisiana's wetlands are disappearing at rates of 40 square kilometers per year. In a few decades the barrier islands may be gone and the wetlands will be lost even faster.

Before Hurricane Andrew. After Hurricane Andrew.
Before Hurricane Andrew After Hurricane Andrew
The area shown is part of the Isles Dernieres in central Louisiana. Sustained winds in excess of 135 miles per hour accompanied Hurricane Andrew as it passed across the western end of these barrier islands. The photograph on the left was taken in July 1992 before Hurricane Andrew [larger version]. The photograph on the right was taken several days after the passage of Hurricane Andrew in August 1992 [larger version].

Information collected by USGS scientists aids coastal planners and managers.

Information and expertise gained during the Louisiana Barrier Island Erosion Study has had a direct impact on local plans for mitigating barrier island loss. Data on seafloor change, shoreline change, and geologic framework have been provided to parish planners and engineers involved in restoration projects. USGS scientists cooperate with State and local governments to provide technical advice on use of sand resources for barrier island nourishment.

USGS scientists plan studies of the high-energy processes responsible for storm damage.

In order to help mitigate the impacts caused by hurricanes such as Andrew and Iniki, environmental managers and engineers must understand the geological processes that cause erosion and environmental change. Results of the recently-completed Louisiana Barrier Island Erosion Study are presently used in formulating erosion-mitigation strategies. Documentation of impacts by Andrew to this area, for example, when compared and interpreted in relation to previously-gathered data, provide an invaluable baseline for mitigation projects and loss-reduction strategies for other areas affected by such storms.

Before Hurricane Andrew. After Hurricane Andrew.
Before Hurricane Andrew After Hurricane Andrew
Soldier Key, 15 miles south of Miami Beach, was inundated during the passage of Hurricane Andrew. The home, associated buildings, and vegetation (shown two weeks before the storm in the left photograph [larger version]) were severely impacted in a few hours, leaving the island devastated (shown one week after the storm in the photograph on the right [larger version]).

Contact Information
Dr. Abby Sallenger
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
Phone: (727) 803-8747
Fax: (727) 803-2032

Related Research Projects:

Hurricane and Extreme Storm Impact Studies
USGS Coastal & Marine Geology Program

Coastal Zone Hydrodynamic Modeling of Storm Surge, Flooding, Drying, and Horizontal Currents Caused by Hurricanes and Northeaster's
USGS Coastal & Marine Geology Program

Related Links:

Louisiana Geological Survey
State of Louisiana

Mapping Coastal Change Hazards
USGS Coastal & Marine Geology Program

Tropical Storm Tracks
University of Hawaii

University of Hawaii
Manoa, Hawaii

National Oceanic and Atmospheric Administration
U.S. Department of Commerce

National Hurricane Center
National Oceanic and Atmospheric Administration

Coastal and Marine Geology Program > Hurricane Impacts on the Coastal Environment

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