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Scientists say Louisiana slip-slidin' away, not sinking

A new report by scientists studying Louisiana's sinking coast says the land is not just sinking -- it is sliding ever so slowly into the Gulf of Mexico.

The new findings may further complicate plans being drawn up to build bigger and better levees to protect New Orleans and Cajun bayou culture from the kind of flooding and damage caused by Hurricane Katrina and other storms that routinely batter the US Gulf coast.

If the land is shifting -- even slightly -- engineers may need to take that into consideration as they build new levees and draw lines across the coast to delineate which areas should and should not be protected.

Researchers have known for a long time that the swampy land under south Louisiana is sinking -- pothole-riven streets and wobbly porches and floors caused by subsidence are visible evidence of that -- but a lateral movement of the land into the Gulf enters largely unstudied terrain.

GLACIAL SPEED

The report, which appeared in last month's issue of the Geophysical Research Letters, a journal that is published by the American Geo-physical Union, said that the bedrock under southeast Louisiana is breaking away at a glacial speed.

The southward movement is triggered by deep underground faults slipping under the enormous weight of sediment dumped by the Mississippi River, the study said.

The slippage, though, is confined to a large egg-shaped area approximately 400km long and 290km wide that encompasses the delta of the Mississippi, which was built up by river deposits over the past 8,000 years, the report said.

The report was based on data collected between 1995 and last year by Global Positioning System stations installed in recent years to better understand the dynamic nature of this delta the French settled in 300 years ago.

NO WORRIES

"People should not be afraid that we're going to fall into the Gulf. That's not going to happen," said Roy Dokka, lead researcher and executive director of the Center for GeoInformatics at Louisiana State University.

He described the slide into the Gulf as "a kind of avalanche of material, except that it is happening very slowly. It moved about the width of two credit cards this year."

While that may seem trifling in the big picture, Dokka said that engineers needed to include this reality into their plans for levees, floodgates and other projects.
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