Aug 31 2005
While the shrill, and not too knowledgeable, left wing nuts run rampant claiming Katrina’s devastation was the fault of Bush and convservatives – the rest of us can refer to science and the study of the bayous for the real cause. It is a well known fact, unless you are a Kyoto lemming, that the gulf coast as been sinking for decades.
Yes folks, sinking. The water is not rising, the area around the Mississippi River Delta is sinking. And it is due to the damns and levies established to control flooding. This has reduced the material flowing down and out of the Mississippi River into the Gulf. I was reminded of these studies when the Mayor of New Orleans correctly noted that the bayou used to be a barrier to storm surge. But they have been disappearing at an alarming rate. From the Sierra Club (no right wing outfit) we see 25-30 square miles a year is lost.
Every year, 25 to 35 square miles of Louisianaâ€™s bayou countryâ€”an area larger than Manhattanâ€”sinks into the Gulf of Mexico. Since the 1930s, an area about the size of Rhode Island has disappeared. And without immediate and focused intervention, the rate of loss is likely to accelerate.
Here is the suspected cause (which is from measurements folks, not computer models)
The “straight-jacketing” of the Mississippi River is usually listed first among the causes of coastal subsidence. After the great flood of 1927, residents of the floodplain demanded action, and the Army Corps of Engineers responded by building levees as much as 30 feet high along the length of the river. But the rich sediment that the erratic branches of the Mississippi had once deposited throughout Louisiana is now funneled right to the Gulf of Mexico and dumped over the continental shelf. The broad coastal plainâ€”more than 40 miles wide from Baton Rouge to the Gulfâ€”is now denied the sediment it had received for thousands of years. So inland areas built on loose silt, like New Orleans, are subsiding. The tides and fierce storms of the Gulf wash away the coastâ€™s outlying coastal marshes and beaches. Of the entire 18,000-square-mile coastal zone, more than 96 percent is less than two feet above sea level.
Man has caused other problems, ones I would think would be correctable:
But there are other notable causes. The thousands of oil and gas pipelines and pump stations that cut through the fragile landscape create canals where saltwater can enter and erode the swamps. Canals constructed for waterborne commerce cause the same problems
Of course, being the Seirra Club you have to mention Global warming, and it is mentioned as a possible minor factor
And the rise in sea level caused by global warming is also cited as a cause of lost land.
Of course there has been no measurable increase in the sea levels that I am aware of. Have Holland’s dikes had to be raised? Have beaches along our coast seen 25-30 square miles a year submerge under rising oceans? Of course not.
By centuryâ€™s end, much of southern Louisiana may sink into the Gulf of Mexico. The Texas coastline, including Galveston, could soon follow.
Thatâ€™s the sobering â€” and controversial â€” conclusion of a new report published by the National Oceanic and Atmospheric Administration that finds the northern Gulf of Mexico is sinking much faster than geologists thought.
The report centers on the humble benchmark, a small metal disk bolted to the ground, that provides a standard elevation above sea level for land surveying and mapping as well as determining flood-prone areas.
But thereâ€™s one problem with benchmarks: They donâ€™t give reliable elevation readings if theyâ€™re sinking along with everything else.
Thatâ€™s what the geologists who wrote the NOAA report say is happening in Louisiana: The yardstick is broken. Instead of minimal geologic subsidence along most of the Louisiana coast, as previously thought, the stateâ€™s entire coastal region is sinking at least 5 feet every century.
And although a number of local officials disagree with the reportâ€™s conclusions about Texas, hereâ€™s a scary thought: Similar forces could well be at work just a few miles south of Houston.
â€œSubsidence doesnâ€™t stop at the Texas border,â€ said Roy Dokka, a co-author of the NOAA report and a Louisiana State University geologist.
This is not a global warming issue, it is something else. It could even be techtonic. But it was not President Bush that caused this shelf to sink 5 feet per century.
Laura Rozen has some other information here.