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Fieldwork

Before-and-After Aerial Photographs Show Coastal Impacts of Hurricane Katrina


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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.

the Chandeleur Islands
Above: The Chandeleur Islands (imagery acquired in 1998) are a north-south-oriented chain of low-lying islands approximately 100 km (60 mi) east of New Orleans. Yellow arrow points to area shown in pair of photographs below, taken before and after Hurricane Katrina.

photos of the Northern Chandeleur Islands before and after Hurricane Katrina
Above: Northern Chandeleur Islands. The first image, taken in July 2001, shows narrow sandy beaches and adjacent overwash sandflats, low vegetated dunes, and backbarrier marshes broken by ponds and channels. The second image shows the same site on August 31, 2005, two days after Hurricane Katrina made landfall on the Louisiana and Mississippi coastline. Storm surge and large waves from Hurricane Katrina submerged the islands, stripped sand from the beaches, and eroded large sections of the marsh. Today, few recognizable landforms are left on the Chandeleur Island chain. [larger version]

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.

photo of dauphin Island
Above: A developed section of Dauphin Island in 2000. Large yellow arrow points to area shown in trio of oblique photographs below.

before and after images of Dauphin Island showing coastal change and property damage caused by Hurricane Ivan and Hurricane Katrina
Above: Dauphin Island. The top image was taken in July 2001, before Hurricane Lili (2002). The middle photograph was taken on September 17, 2004, immediately after the passage of Hurricane Ivan. The bottom image was acquired on August 31, 2005, two days after Hurricane Katrina. Note the road and two parallel canals in the first photograph. The post-Ivan photo shows overwash deposits covering the road and encroaching on the first canal. The post-Katrina photo shows that the overwash deposit has not only covered the road but also filled the first canal and is encroaching on the second. The beach appears brown in the bottom photograph because of a "deposit" of plant debris. [larger version]

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 endeavor—it is a matter of public safety."


Related Sound Waves Stories
USGS Center in Lafayette, LA, Provides Aid in the Aftermath of Hurricane Katrina
September 2005

Related Web Sites
USGS Responds to Hurricane Katrina Disaster
U.S. Geological Survey (USGS)
Hurricane Katrina Impact Studies
U.S. Geological Survey (USGS)

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in this issue: Fieldwork
Cover Story:
USGS Provides Aid in the Aftermath of Hurricane Katrina

Coastal Impacts of Hurricane Katrina

Hydrologic Impacts of Hurricane Dennis

ATRIS Used to Survey Sea Floor in Dry Tortugas National Park

Research Using Genetic Modeling to Assess the Health and Status of Manatee Populations

Outreach USGS Activities Rock the Waquoit Bay Watershed Block Party

Balancing Wildlife Needs and Wetland Restoration in San Francisco Bay

Journalism Interns Help Get the USGS Word Out

Meetings 2005 Meeting of the Digital Library for Earth System Education

Workshop on Integrating Modeling and Laboratory Gas Hydrate Studies

Staff & Center News Steven Schwarzbach Appointed Director of USGS Western Ecological Research Center

Woods Hole Science Center Hosts Visitor from India

Publications September Publications List


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