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Hurricane Katrina was a category 4 storm with winds as high as 140 mph when it struck the Gulf Coast at about 5 a.m. on August 29. On the basis of its barometric pressure, Katrina was the third-most intense hurricane to hit the United States since reliable records began in 1851 (exceeded only by the "Labor Day Hurricane" that hit the Florida Keys in 1935 and Hurricane Camille, which hit the Gulf Coast in 1969).
Katrina's intensity took a heavy toll on coastal landforms, as shown in aerial photographs posted by the U.S. Geological Survey (USGS) documenting conditions before and after the hurricane along the northern Gulf of Mexico coastline. Available at URL http://coastal.er.usgs.gov/hurricanes/katrina/, the photographs are one result of a cooperative project being conducted by the U.S. Geological Survey (USGS), the National Aeronautics and Space Administration (NASA), the U.S. Army Corps of Engineers, and the University of New Orleans to investigate coastal change produced by the hurricane. Aerial-video, still-photography, and laser-altimetry surveys of post-storm beach conditions were collected on August 31 and September 1, 2005, for comparison with earlier data. The comparisons will show the nature, magnitude, and spatial variation of such coastal changes as beach erosion, overwash deposition, and island breaching. These data will also be used to further refine predictive models of coastal impacts from severe storms. The data are being made available to local, State, and Federal agencies for purposes of disaster recovery and erosion mitigation.
Among the photographs posted on the USGS Web site are before-and-after photos of the Chandeleur Islands, LA, mainland Mississippi, and Dauphin Island, AL, along with several sets of "quick response" photographs from Bay St. Louis to Biloxi, MS.
Photographs of the Chandeleur Islands show dramatic removal of all the sand, leaving only marshy outcrops barely above sea level. Before Katrina struck, the island chain consisted of narrow sandy beaches and low vegetated dunes. The coastal response is similar to the damage observed in the Isles Dernieres, LA, after Hurricane Andrew in 1992. USGS coastal researcher Abby Sallenger said, "I've seen dramatic response in the Chandeleur Islands after a number of storms, but I've never seen it this bad; the sand is just gone."
Dauphin Island, AL, lies about 50 km (30 mi) south of Mobile and approximately 110 km (70 mi) east of where Katrina's eye came ashore. Sections of Dauphin Island west of the airport and fishing pier look as if an enormous rake has been dragged across the island. Large amounts of beach sand washed over the island, covered roads, and filled canals. Storm surge created numerous temporary inlets as the water carved out paths through the sand.
Photographs along the mainland coast of Mississippi show evidence of the destructive power of the storm surge. The surge of water moved inland, carrying with it the debris of structures from the first four or five blocks that had been swept away. The wrack line of debris is a 5- to 8-ft-high pile that ended up several blocks inland. Offshore casino barges are lodged inland, and mere foundations are all that is left of many buildings. Sections of bridges of Interstate Highway 90 have been destroyed, with the remaining pieces toppled like dominoes.
"The past several days have seen remarkable devastation resulting from Hurricane Katrina. Our thoughts and prayers are with everyone who has been affected by this disaster," said USGS Acting Director Pat Leahy. "In the aftermath of Katrina, USGS research on hurricanes and natural hazards is no longer just a scientific endeavorit is a matter of public safety."
in this issue:
Coastal Impacts of Hurricane Katrina
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