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Coastal Louisiana gets that sinking feeling

Subsidence in Bayou may lead to biggest - and riskiest - wetland restoration in history.

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Nowhere in the world is a coastal region losing losing wetlands and protective barrier islands faster than Louisiana. The region is sinking as layers of river-borne muck hundreds of feet thick shift under their own weight.

Now, state, local, and federal officials are pulling together a $14 billion plan to slow the losses, in what would rank as the most ambitious wetlands restoration effort in history. As they do, scientists are raising new questions about how quickly the subsidence is occurring. It's a question whose answer could determine the shape of the political debate over the direction the program takes, or perhaps whether it moves forward at all.

"There's a lot riding on this," says Jeff Williams, a researcher with the US Geological Survey's coastal and marine geology program at Woods Hole, Mass. "Has Louisiana passed some sort of threshold beyond which it's not possible to restore the coast or maintain the conditions we have?"

If the answer is yes, he adds, "It doesn't mean you have to write it off," but it would significantly affect the shape of the program. Current notions of trying to mimic nature's processes for rebuilding river deltas through dredging and moving silt, rechanneling streams and river tributaries, and pumping water from one location to another could shift toward solutions such as the Netherlands' system of dikes, dams, and seawalls. Depending on loss-rate estimates, planners might be faced with the extreme measure of moving millions of people to higher ground.

It's a daunting prospect for a region already engaged in an economic life-or-death struggle against geophysics. For 20 years, the US Army Corps of Engineers has been trying to prevent the Mississippi River from changing course and heading down what is now the Achafalaya River. All that stands between the Mississippi and disaster are three dams that regulate the flow of water down the Achafalaya. If the river were to break through and shift course, Baton Rouge and New Orleans would become economic backwaters instead of bustling maritime and industrial centers, while the region along the Achafalaya would be inundated.

Soggy first line of defense

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