Shells instead of seawalls? Experts give it a shot

updated 12:47 p.m. ET Oct. 29, 2008

DAUPHIN ISLAND, Ala. - Crews keep building high sand barriers to protect this fragile strip of land from erosion, and nature's wrath keeps washing them away.

Most recently, on Sept. 1, Hurricane Gustav erased a 10-foot-tall berm, a wall of sand that stretched for more than three miles.

Now marine scientists are turning to nature itself as the solution in an experiment to mend eroded shorelines.

By planting tons of oyster shells to form angular breakwaters near Dauphin Island, they hope to show that aquatic life drawn to the shells can create a "living shoreline," preventing coastal erosion better than ugly bulkheads, blunt seawalls or feeble berms that inevitably have to be rebuilt.

"Bulkheads are horrible and people build them out of ignorance," said Just Cebrian, who is directing the project at the Dauphin Island Sea Lab, Alabama's state-funded marine science institute.

Scientists in a growing number of states are pursuing living shorelines where once they might have watched or even helped as walls were built to hold back the sea.

North Carolina has had over 30 demonstration projects, including some using oyster shells. Virginia, Maryland and Delaware have been requiring alternatives to bulkheads and seawalls for some time. Projects also have been completed in Pensacola, Fla., and Biloxi, Miss.

"The issue is certainly gaining traction," said Tracy Skrabal of Wilmington, N.C., regional manager for the North Carolina Coastal Federation.

Dauphin project half the cost
Taxpayers are funding the Sea Lab's living shoreline project with a $1.5 million fisheries restoration grant from the National Oceanic and Atmospheric Administration awarded after Hurricane Katrina struck in 2005.

That's less than half the price of the recently demolished berm, built in 2005 with sand pumped from Mississippi Sound. That $3.6 million barrier replaced a $1 million version that was done in by Tropical Storm Isidore in 2002. That first sand wall had been completed in June 2000 as an emergency project initiated after Hurricane Georges in 1998.

These man-made fixes are necessary in part because of man's interference, according to a 2007 U.S. Geological Survey report, which blamed dredging along with storms and rising sea levels for carving away at barrier islands.

The Army Corps of Engineers dredges a 45-foot-deep shipping channel through the mouth of Mobile Bay, right past Dauphin Island. While port officials discount the dredging's impact, the channel — a necessity for the nation's 10th-largest port — interrupts the westward drift of sand that otherwise would naturally replenish Dauphin Island.

The Federal Emergency Management Agency recently said that officials haven't decided whether to replace the latest berm.

Bulkheads and seawalls hold back damaging waves, but they also tend to alter or destroy natural habitat, according to scientists advocating the living shoreline option. Bulkhead walls create a "bathtub effect" that eliminates fringe wetlands and shallows that harbor young fish that eventually move into the Gulf of Mexico, said Scott Douglass, a University of South Alabama coastal engineer.

Idea won't work everywhere
Sea Lab scientists said oyster shells placed in brackish waters with good tidal flow will rapidly become colonized by a multitude of marine critters, including oysters, algae, worms, barnacles, crabs, small minnows and fish.

Carl Ferraro, a natural resource planner with the Alabama Department of Conservation and Natural Resources, said the living shorelines technique can't be used in some spots.

"It won't generally work in very deep water where you have a significant drop right at the shoreline," he said.

It's also impractical for certain commercial or industrial settings where a bulkhead would be required because of deep water, Ferraro said.

Still, scientists are eager to try it most everywhere else.

"All resources agencies would like to see folks starting to use living shorelines," Ferraro said. "That change in mind-set and regulations is slow to come."

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