Gulf Coast Faces Sea Level-Sinkage Double Whammy

Sept. 3, 2008 -- Hurricane Gustav has been a harsh reminder that it's only the whim of a hurricane track, a few miles this way or that, which can make the difference between a close call and another Katrina-like catastrophe for New Orleans and other Gulf Coast communities.

With the one-two punch being delivered by sinking land and rising sea levels, and with every hurricane threatening a knock-out blow, it's getting harder to avoid that very unpopular question: How much longer can these coastal communities survive?

To get the answer Discovery News caught up with four Gulf Coast researchers and posed the question to them. Their answers differ, but they agree on one thing: The long-term prospects are not good.

Body Blows

"This is a discussion that should have occurred after Katrina," said Roy Dokka of Louisiana State University. Dokka has been outspoken about the measurable rates of subsidence -- the process by which land slips below sea level -- in New Orleans and other coastal areas. His work indicates that larger geological forces, far beyond the control of humans, are causing parts of New Orleans to sink.

"New Orleans is going to last as long as people decide that they want to do this and as long as the U.S. taxpayers want to spend money propping it up," said Dokka. Other, smaller communities will not fare so well, he said, because there is little or no money to save them. "New Orleans will last as long as people are willing to put up a struggle. But nature will keep punching until people give up."

Ideally, Dokka said, New Orleans is safe for no more than 100,000 people, concentrated along the river. It's a geological reality, he explained.

Rising Waters

Subsidence is critical, but it's just part of the problem, argues geologist Torbjorn Tornqvist of Tulane University.

"I think we've got our priorities wrong on this," said Tornqvist. "No matter what we do as far as building levees and restoring wetlands, if we don't address global warming, it's pointless."

Since Katrina, Tornqvist and Dokka have often been at odds about how to measure subsidence rates, and its causes, in southern Louisiana. But neither denies that global warming is melting glaciers and raising sea level globally an average of 1/8-inch per year. Add in sinking land -- whatever the cause -- and you get a double whammy.

No one knows how long New Orleans can stand as a viable city, stressed Tornqvist, but sea levels alone could rise by three to four feet by the end of the century. If that happens, New Orleans is doomed.