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Taken from the news pages
Channels blamed
for shrinking barrier islands

Staff Reporters
Sunday, June 15, 2008

Erosion caused by ship channels in Mobile, Pascagoula and Gulfport has been singled out by federal scientists as a primary reason the string of five barrier islands beginning at Dauphin Island and stretching to Cat Island off Mississippi is slowly withering.

But those same channels - like dozens of major shipping corridors maintained around the nation by the U.S. Army Corps of Engineers - are critical components of the nation's shipping economy.

Mobile's port, for instance, provides the entryway for nearly all of the Colombian coal burned at each of Alabama Power's electric plants, as well as for car parts destined for the Hyundai and Mercedes vehicles manufactured in the state. Pascagoula's port is a major player in the international export of fertilizer, while Gulfport has long been a receiving center for fruit shipped from abroad.

Their channels, with Mobile's more than 10 miles long, are maintained at depths of about 45 feet through large-scale federal dredging operations. The shallow, shoal-filled waters traversed by the three deep channels range from 10 to 15 feet deep. Corps documents indicate that more than 20 million cubic yards of sand have been removed from the Mobile channel since about 1940. That's equivalent to 1 million dump truck loads of sand.

Scott Douglass, a coastal engineer with the University of South Alabama, has estimated that beaches on Dauphin Island might be 1,000 feet wider today if that sand had not been removed from the natural sand delivery system.

The dredge machines used by most of the corps' contractors operate like huge vacuums, sucking sand from the bottom of the channels and pumping it to the surface. Often, the sand is pumped onto barges with special doors in the hull. To dispose of the sand, the barge is simply pushed away from the channel and taken to a dumping area. The hull doors are opened and the sand falls out, sinking to the seafloor in a disposal area.

Until about 10 years ago, all sand dredged from the Mobile Ship Channel was dumped about a mile offshore, in water much too deep to ever be swept up by the nearshore currents that deposit sand on beaches.

On Dauphin Island, dozens of houses were lost even before Hurricanes Ivan and Katrina to the disappearing beaches. In fact, Sand Island, once several acres in size, was also lost because of the effects of the channel dredging, according to coastal scientists. An ongoing lawsuit seeks to hold the corps and its dredging of the Mobile Ship Channel accountable.

Beaches near ship channels around the nation have suffered from well-documented sand loss after channels were constructed. The corps has been on the losing end of several lawsuits seeking hundreds of millions of dollars in damages. In some cases, the corps has agreed to rebuild the diminished beaches, and agreed to take dredged sand and place it where nearshore currents can pick it up and push it back onto the beaches, where it was headed before falling in the channel.

Scientists say that if the corps were to place the sand dredged from the channels in Mobile, Pascagoula and Gulfport in shallow water to the west of each channel, the problem of the shrinking barrier islands might be solved. Corps officials indicated to the Press-Register in recent interviews that they would be operating in that fashion in the future.

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