Sea Litter

Underwater debris left in the wake of Hurricane Katrina included this sunken ship in Pascagoula, Miss. Now, NOAA's Office of Response and Restoration and Office of Coast Survey, working with the U.S. Coast Guard and other federal and state agencies, are assisting with Gulf of Mexico recovery efforts by performing side scan sonar surveys and risk assessments of the debris.

A side scan transmits sound energy in the shape of a fan that sweeps the seafloor and then analyzes the return signal, or echo, that has bounced off the seafloor or other objects. The strength of the return echo is continuously recorded creating an image of the seafloor where objects, such as this sunken ship, that protrude from the bottom show up as a dark image (strong return) and shadows from these objects are light areas (little or no return).

After the 2005 hurricane season, the coastal zones of Louisiana, Mississippi and Alabama, and the near shore environment, were littered with debris hazardous to safe navigation, commercial fishing, recreational boating and other normal activities. With these surveys, the team will provide images of the debris and seafloor to update nautical charts in the region and provide mariners with more accurate and up-to-date navigational information.

--LiveScience Staff

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Credit: NOAA