Louisiana faces another threat: What lies under its coast

4/2/2006, 10:26 a.m. CT
By CAIN BURDEAU
The Associated Press

NEW ORLEANS (AP) — Add one more possible threat to Louisiana's rebuilding: Active geologic faults that are causing levees, flood walls, bridges, homes and other structures to sink.

A new study, published in the April edition of the Geological Society of America's Geology journal, charts a major fault, the Michoud fault, that runs through eastern New Orleans.
The study argues that the fault's downward movement "set the stage for the devastation of Hurricane Katrina by lowering elevations of the land and surrounding levee defenses."

In recent years, studies of subsurface faults, salt domes and other geologic characteristics have emerged as critical in the debate over what is causing Louisiana to lose vast tracts of land. The coast has lost about 1,900 square miles of wetlands — an area roughly the size of Delaware — since the 1930s.

The slumping of the Michoud fault, the study said, has caused up to about 73 percent of the subsidence in sections of eastern New Orleans, an area that has seen some of the worst rates of land loss in south Louisiana. The land sank by as much as 1.7 inches between 1969 and 1971, Dokka said.

The study was the result of ongoing work by Roy Dokka, a Louisiana State University geologist, and the National Geodetic Survey to calculate land changes in south Louisiana using global positioning system base stations and tide gauges.

Dokka's theories on how natural tectonic fault movements cause subsidence run counter to studies that have shown oil extraction and soil compaction as main reasons why the land is sinking.

This threat from deep underground has major implications. If faults are causing the sinking there is very little humans can do to offset the subsidence other than build higher levees.

"It basically says that when levees cross faults, they need to apply more dirt on top of them to keep them safe," Dokka said.

But if oil drilling was the main culprit, then there's hope that the slowdown in onshore drilling will equate to less subsidence.

"Can faulting be induced? Absolutely, and he (Dokka) omits that completely," said Bob Morton, a geologist with the U.S. Geological Survey who blames oil drilling for large amounts of subsidence.

Morton said sampling peat deposits is a more reliable method for determining long-term rates of sinking. Based on peat calculations, the rate of subsidence was minimal before oil started being extracted in the 20th century, he said.

Dokka said oil was not drilled near the Michoud fault, so the sinking wasn't caused by "the usual suspects ... it has to be something deep."

A recent report by the National Academy of Sciences, "Drawing Louisiana's New Map," cited subsidence as an area that needs more study.

"Subsidence is virtually ubiquitous in coastal Louisiana and it is a fundamental underlying cause of land loss," said Joe Kelley, a marine geologist with the University of Maine and author of "Living With the Louisiana Coast."

Despite the disagreements, subsidence is now a component in rebuilding plans.

Al Naomi, a top U.S. Army Corps of Engineers project manager, said more attention is being paid to it and fault studies.

Sherwood Gagliano, a Louisiana scientist who's conducted several pioneering coastal studies, said he's begun investigating whether fault movements caused the New Orleans flood walls that broke during Hurricane Katrina to sag. He said there are "very strong suggestions" that the breaches occurred where the walls crossed fault lines.

"It's possible," Naomi said, "but we don't think that's an overarching reason why we had some levee problems recently."

Well,,, duhhhh. When I drove through New Orleans, all I could ascertain is that it is an island,,,, and it's below sea level !!! Looks like a no brainer to me.

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

None of this is news. The folly was thinking you can fool mother nature forever. Any area in a river delta will subside as compaction occurs when sediment is deposited. The entire gulf coast is geolgically very young and the subsurface is relatively soft rock, lots of uncomsolidated sediments. This extends offshore as well.

__________________
MB-less

How much you wanna bet the whole area gets wiped out again this hurricane season? Hate to see it, but I'd put the odds at 1 in 3 at best. You wouldn't see me rebuilding if I formerly resided there.

Wasn't there a termite theory recently as to why the levees collapsed?

I can't see why anyone would rebuild there or what insurance company (other than USA) would insure them again. It is a poor risk, especially for the next few years of the stronger hurrican cycle.

__________________
-livin' in the terminally flippant zone

Should people be allowed to build on active Kahlifoahnia fault lines?

Build anywhere you want, just don't expect the rest of the country to help you rebuild after the disaster.
regards,
Mark

What has happened down here is the wind has changed
Clouds roll in from the north and it started to rain
Rained real hard and rained for a real long time
Six feet of water in the streets of Evangeline

The river rose all day
The river rose all night
Some people got lost in the flood
Some people got away alright
The river have busted through clear down to Plaquemines
Six feet of water in the streets of Evangeline

Louisiana, Louisiana
They're tryin' to wash us away
They're tryin' to wash us away
Louisiana, Louisiana
They're tryin' to wash us away
They're tryin' to wash us away

President Coolidge came down in a railroad train
With a little fat man with a note-pad in his hand
The President say, 'Little fat man, isn't it a shame what the river has done
To this poor crackers' land'. . ."

--"Louisiana 1927," Randy Newman
Thanks to Poe for the lyrics.

I completely agree. Let's get the federal gov out of the insurance business, too. If people wish to live in a flood zone let them bear the burden of their decision.

Complete agreement there...

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

amen. However, I have no problem with people buying insurance from private companies - if they can afford it. If you go by what I expect the actuaries will come up with regarding NOLA it will be too expensive for most. C'est la vie.

__________________
-livin' in the terminally flippant zone

I am waiting for the big quake to hit St. Louis, MO.
http://www.eas.slu.edu/Earthquake_Center/earthquakecenter.html

Hereis a real-time map showing big events around the globe, ie.
Major accidents: (Plains, Trains & Ferries etc) Disease Outbreaks (Bird flu & Cholera etc) Earthquakes WX events and related evacuations.

Updated as events are happening. Below the map are categorized event showing additional details as known about the event. Or you may just click on the icon and get the same info.

the root site is:
http://visz.rsoe.hu/alertmap/woalert.php?lang=eng
Click on symbols for details on worldwide “major events”
Icon descriptions are here:
http://visz.rsoe.hu/alertmap/icons.php?lang=eng

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Oh, you want me to be responsible for my bad decisions? WTF? This is an entitlement society and a society that is responsible for my stupidity. Where have you been living?

__________________
01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

A spiderhole. Pass the hummus, please.

That's an awesome site! Thanks for the link.

__________________
-livin' in the terminally flippant zone