Image by James Gleason, Northwest Hydro Inc

3D Sonar Map Shows Sunken Civil War Ship

One hundred and fifty years ago, 20 miles off the coast of Texas, the Hatteras gunboat was sunk during a battle with the famous Confederate commerce raider CSS Alabama. The battle was one of the skirmishes that saw the key southern port of Galveston change hands twice and remain one of the last bastions of the Confederacy.

A new 3-D state of the art sonar map shows never-before seen details of the USS Hatteras, the only Union warship sunk in combat in the Gulf of Mexico during the Civil War.

Today, the wreck of the Hatteras is largely intact, resting 57 feet underwater in sand and silt. Recent hurricanes and storms have removed some of the sediment and sand that once encased the vessel like a time capsule. Given shifting sands may once again rebury the Hatteras, a research team seized the opportunity for a two-day mission to create 3-D photo mosaics of the Hatteras for research and educational purposes.

“Most shipwreck survey maps are two-dimensional and based on observations made by sight, photographs or by feeling around in murky water while stretching a measuring tape,” said James Delgado, director of maritime heritage for NOAA’s Office of National Marine Sanctuaries. “Thanks to the high-resolution sonar, we have a three-dimensional map that not only provides measurements and observations, but the ability for researchers and the public to virtually swim through the wreck’s exposed remains and even look below the surface at structure buried in loose silt.”

Delgado said the survey revealed previously unknown details like the survival of most of one paddlewheel, as well as the fact that the ship’s stern and rudder are emerging from the sand. The three-dimensional map also plots damage to engine room machinery and the ship’s paddlewheel shaft, which seems to have bent when the ship capsized and sank after being shot full of holes.

“The engine room spaces were a dangerous place in the battle,” Delgado said. “Cannon fire severed steam lines and filled these spaces with scalding steam. Fires broke out, and yet the crew stayed at their post to keep the ship running and fighting, and in here, two of them paid the ultimate price.”

Listed in the National Register of Historic Places, the Hatteras was part of the 1863 West Gulf Blockading Squadron commanded by Union Rear Admiral David Farragut. The squadron was part of the U.S. Navy’s efforts to block the passage of goods, supplies, and arms to and from the Confederacy on the Atlantic and Gulf coasts.

The USS Hatteras is protected as a war grave.

Image by James Gleason, Northwest Hydro Ink

Further Reading:
NOAA National Marine Sanctuaries
3D Underwater Maps: Connecting GPS and sonar to laptops

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