Outer Shield
The comprehensive plan may seem more feasible than the total shield, but there are reasons to consider enclosing the significant tracts of marsh that the other plans would leave exposed to the sea. The marshes provide wintering grounds for 70 percent of the nation's migratory waterfowl, cushion ocean waves that could otherwise disturb shallow underground pipelines, and could partially absorb rising sea levels. The region could be walled in by connecting the barrier islands with dams and long stretches of gates--the option the Netherlands embraced after a horrific 1953 storm generated a 15-foot surge that killed 1,800 people and flooded 800 square miles. Virtually the entire country is delta; 26 percent of it is below sea level, bottoming out at -22 feet, lower than New Orleans. The surface is subsiding, too, accelerated by extraction of freshwater and peat, and is home to several major lakes and river outlets. Today the nation is outlined by more than 1,000 miles of dikes (levees), dunes, dams and gates--far longer than the line needed around Louisiana.

Joop Weijers, a longtime senior engineer at the Dutch Ministry of Transport, Public Works and Water Management, which oversees the Delta Works network, says a similar approach could protect Louisiana and deltas in other nations. Although the Netherlands's shield may seem grandiose, Weijers says "building the whole system right now would cost $15 billion to $16 billion." Maintenance runs about $500 million a year. But after the coast was secured, he adds, "the region got an economic boost in tourism, farming and industry."

Coastal administrator Len Bahr says an outer shield is a wild idea, but given the delta's alarming deterioration, "we may need some wild new ideas." Williams of the USGS concurs: "Considering the rates of sea-level rise, land subsidence, and the increasing frequency and severity of storms, it's a legitimate option."

Take a Scientist to Lunch
Panicked by the devastation in 1953, the Dutch quickly set out to build solid dams across several wide estuaries to the North Sea. Those berms, however, cut off the interchange of saltwater and fresh¿water and altered the environment. In recent decades, Delta Works has changed direction, emphasizing man-made barriers that close only when surges are imminent. "It took us a long time to learn that we could work with nature, not just defy it," Weijers says. He advises U.S. planners to "really think it through."

Wagonaar at the Corps, Malbrough at Shaw Coastal, and Mashriqui at L.S.U. agree that certain aspects of the original Coast 2050 and LCA plans that would revive the marshes must be incorporated into any plan adopted. Diversions--large doorways inserted into the levee along the Mississippi River's banks--would supply freshwater and sediment to the wetlands. The Corps' plan includes a significant number of gates to "let water flow in and out to support the LCA objectives," Wagonaar says.

Although the Netherlands and Britain probably have much advice to offer, Malbrough says, "we don't need the Dutch to tell us how to build a levee system." The Corps apparently felt that way at one time, too; its officials made similar statements to Scientific American during research for a 2001 article about restoring the delta [see "More to Explore" below]. But collaboration may improve. In 2004 the Corps and Delta Works leaders signed a memo of understanding to exchange information, and in October several Dutch engineers helped the Corps analyze New Orleans's flood-wall failures.

The need to coordinate physical protection across levee districts and to incorporate coastal restoration means a clear leader is needed. The experts interviewed for this article acknowledged that political infighting in Louisiana killed smaller proposals in the past. Malbrough hopes this message may be sinking in; he was hired by various levee boards together to present the state and federal government with one coordinated plan. Both he, Mashriqui and Bahr think a federally run consortium should oversee the work. They oppose putting the Corps in charge, seeing it as too slow, too politicized by Congress, and too unwilling to entertain novel technical approaches. "I'm inclined to change horses," Mashriqui says.�

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