Moving the Mississippi: would changing the river's course help save the vanishing coastline of Louisiana?

For thousands of years, the Mississippi River has acted like a conveyor belt, carrying millions of tons of sediment downstream each year. And before its flow was controlled, the river meandered across the region, spreading its nutrient-rich contents along coastal Louisiana.

But since the 1820s, when the U.S. Army Corps of Engineers began building levees and dams for protection against flooding, the Mississippi River has essentially been trapped and artificially channeled into the deep waters of the Gulf of Mexico.

As a result, the wetlands and barrier islands along Louisiana's coast, which were once regularly replenished by river sediment, have begun to deteriorate--and disappear.

Scientists have long said that the only way to restore Louisiana's vanishing coastline is to undo the elaborate levee system and divert the river to the sediment-starved marshes below New Orleans to the southeast.

The idea, previously dismissed as impractical, too expensive, and lethal to the region's economy, is now gaining widespread support. State officials are embracing it, motivated not only by the lessons of Hurricane Katrina but also by fears that global climate change will bring rising seas and accelerated land loss.

HUGE IMPLICATIONS

The best way to protect against future storms, officials now agree, is to allow the muddy river to dump that rich sediment where it's needed most. The hope is that this would slow or even reverse the land loss along coastal Louisiana.

But the prospect of moving a river has huge implications--political, social, and economic--for the people who live near the proposed diversion and for the businesses of the region.

Experts say there would also be tremendous engineering challenges, particularly in finding a new way for freighters to make their way into the Mississippi's shipping channel--not to mention the monumental cost of such an enormous project.

At the same time, there is a growing recognition that the cost of not acting may be just as high. Along the Louisiana coast, in the delta plain, much of the land is only a few feet above sea level. If seas rise as expected by two or three feet in the next century, Louisiana's land loss will only accelerate.

Such a program would not turn things around immediately, but many see it as a crucial step for Louisiana.

"Is it practical? Yes," says James T.B. Tripp, a member of the Louisiana Governor's Commission for Coastal Restoration. "Will it be expensive? Yes. But when you look at the alternatives, it's very cost effective."

Cornelia Dean covers science for The Times.