New Orleans sinking faster than expected

[Matt-hurricanewatcher]

New Orleans sinking faster than expected
AP on Yahoo ^ | 5/31/06 | Seth Borenstien - ap



WASHINGTON - Parts of New Orleans are sinking far more rapidly than scientists first thought, more than an inch a year, new research suggests.

That may explain some levee failures during Hurricane Katrina and raises more worries about the future.

The research, being published Thursday in the journal Nature, is based on new satellite radar data for the three years before Katrina struck in 2005. The data show that some areas are sinking — from overdevelopment, drainage and natural seismic shifts — four or five times faster than the rest of the city. And that, experts say, can be deadly.

"My concern is the very low-lying areas," said lead author Tim Dixon, a University of Miami geophysicist. "I think those areas are death traps. I don't think those areas should be rebuilt."

For years, scientists figured New Orleans on average was sinking about one-fifth of an inch a year based on 100 measurements of the region, Dixon said. The new data from 150,000 measurements taken from space finds that about 10 percent to 20 percent of the region had yearly subsidence in the inch-a-year range, he said.

As the grounds in those rapidly sinking areas shift downward, the protection from levees also falls, scientists and engineers said.

For example, the Mississippi River Gulf Outlet, built more than three decades ago, has sunk by more than 3 feet since its construction, Dixon said. That, he added, explained why water poured over the levee and part of it failed.

"The people in St. Bernard got wiped out because the levee was too low," said co-author Roy Dokka, director of the Louisiana Spatial Center at Louisiana State University. "It's as simple as that."

The subsidence "is making the land more vulnerable; it's also screwed up our ability to figure out where the land is," Dokka said. And it means some evacuation roads, hospitals and shelters are further below sea level than emergency planners thought, he said.

So when government officials talk of rebuilding levees to pre-Katrina levels, it may really still be several feet below what's needed, Dokka and others say.

"Levees that are subsiding at a high rate are prone to failure," Dixon said.

The federal government, especially the Army Corps of Engineers, hasn't taken the dramatic sinking into account in rebuilding plans, said University of Berkeley engineering professor Bob Bea, part of an independent National Academy of Sciences-Berkeley team that analyzed the levee failures during Katrina.

"You have to change how you provide short- and long-term protection," said Bea, a former engineer in New Orleans. He said plans for concrete walls don't make sense because they sink and can't be easily added onto. In California, engineers are experimenting with lighter weight reinforced foam-middle levee walls, he said.

Dixon and his co-author Dokka disagree on the major causes of New Orleans not-so-slow falling into the Gulf of Mexico.

Dixon blames overdevelopment and drainage of marshlands, saying "all the problems are man-made; before people settled there in the 1700s, this area was at sea level."

But Dokka said much of the sinking is because of natural seismic shifts that have little to do with construction.

All is not completely lost, Dokka said. Smarter construction can buy New Orleans some time.

"We've made the pact with the devil by moving down here," he said. "If we do things right, we probably can get another 100-200-300 years out of this area."





I would not rebuild on this sinking piece of land. Your putting your lifes on risk.

[Stormcenter]

New Orleans sinking faster than expected
AP on Yahoo ^ | 5/31/06 | Seth Borenstien - ap



WASHINGTON - Parts of New Orleans are sinking far more rapidly than scientists first thought, more than an inch a year, new research suggests.

That may explain some levee failures during Hurricane Katrina and raises more worries about the future.

The research, being published Thursday in the journal Nature, is based on new satellite radar data for the three years before Katrina struck in 2005. The data show that some areas are sinking — from overdevelopment, drainage and natural seismic shifts — four or five times faster than the rest of the city. And that, experts say, can be deadly.

"My concern is the very low-lying areas," said lead author Tim Dixon, a University of Miami geophysicist. "I think those areas are death traps. I don't think those areas should be rebuilt."

For years, scientists figured New Orleans on average was sinking about one-fifth of an inch a year based on 100 measurements of the region, Dixon said. The new data from 150,000 measurements taken from space finds that about 10 percent to 20 percent of the region had yearly subsidence in the inch-a-year range, he said.

As the grounds in those rapidly sinking areas shift downward, the protection from levees also falls, scientists and engineers said.

For example, the Mississippi River Gulf Outlet, built more than three decades ago, has sunk by more than 3 feet since its construction, Dixon said. That, he added, explained why water poured over the levee and part of it failed.

"The people in St. Bernard got wiped out because the levee was too low," said co-author Roy Dokka, director of the Louisiana Spatial Center at Louisiana State University. "It's as simple as that."

The subsidence "is making the land more vulnerable; it's also screwed up our ability to figure out where the land is," Dokka said. And it means some evacuation roads, hospitals and shelters are further below sea level than emergency planners thought, he said.

So when government officials talk of rebuilding levees to pre-Katrina levels, it may really still be several feet below what's needed, Dokka and others say.

"Levees that are subsiding at a high rate are prone to failure," Dixon said.

The federal government, especially the Army Corps of Engineers, hasn't taken the dramatic sinking into account in rebuilding plans, said University of Berkeley engineering professor Bob Bea, part of an independent National Academy of Sciences-Berkeley team that analyzed the levee failures during Katrina.

"You have to change how you provide short- and long-term protection," said Bea, a former engineer in New Orleans. He said plans for concrete walls don't make sense because they sink and can't be easily added onto. In California, engineers are experimenting with lighter weight reinforced foam-middle levee walls, he said.

Dixon and his co-author Dokka disagree on the major causes of New Orleans not-so-slow falling into the Gulf of Mexico.

Dixon blames overdevelopment and drainage of marshlands, saying "all the problems are man-made; before people settled there in the 1700s, this area was at sea level."

But Dokka said much of the sinking is because of natural seismic shifts that have little to do with construction.

All is not completely lost, Dokka said. Smarter construction can buy New Orleans some time.

"We've made the pact with the devil by moving down here," he said. "If we do things right, we probably can get another 100-200-300 years out of this area."





I would not rebuild on this sinking piece of land. Your putting your lifes on risk.

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

[x-y-no]

One word: Stilts!

[sunny]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

[GalvestonDuck]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

They're in non-tropical forums.

[Matt-hurricanewatcher]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

[sunny]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

Tell you what, I'll go outside right now with my measuring stick and stand there for a while. Okay?

[Stormcenter]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

I think it's because they have been saying that about N.O. for over 40 years when it was 5 feet below sea level and guess what it is still 5 feet below sea level now. So wouldn't the city be like 8 feet below sea level now if in fact it was sinking an inch a year? Oh well, hey these writers have to write about something so I guess why not jump on the "N.O. Is Sinking Bandwagon".

[Stratusxpeye]

Cities sinking, oceans rising, by now half of the gulf coast and florida should be covered. Agree with the respondent posters. These stories are just that imo. Global warming and over devolpment sinking My son, Me And my grandhildren most likely wont be alive for any of these tings to affect us anyway. B4 i die than NO Should be about 13 feet Below sea level and should be a new addition to the gulf.

[seaswing]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

Tell you what, I'll go outside right now with my measuring stick and stand there for a while. Okay?

Nola didn't get a direct hit from Katrina. I do hope that they do not have to experience a direct hit. Mississippi was in the direct path and sustained more hurricane related damage. The Levees created Nola problems. Nola or LA for that matter has basically no wetlands left to protect them from direct hittting hurricanes. Back when Camille hit, there was much more wetlands to protect them, and even though it was a catastrophic hurricane, it would have been much worse without the buffer that the wetlands absorbed. NOLA in my opinion is in a lot of trouble now. Another cat 3-5 hurricane in the vicinity would create just as much if not more devastation. I personally would think twice about living there. But hey, I live in Florida... no levees but barely above sea-level.

[sunny]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

Tell you what, I'll go outside right now with my measuring stick and stand there for a while. Okay?

Nola didn't get a direct hit from Katrina. I do hope that they do not have to experience a direct hit. Mississippi was in the direct path and sustained more hurricane related damage. The Levees created Nola problems. Nola or LA for that matter has basically no wetlands left to protect them from direct hittting hurricanes. Back when Camille hit, there was much more wetlands to protect them, and even though it was a catastrophic hurricane, it would have been much worse without the buffer that the wetlands absorbed. NOLA in my opinion is in a lot of trouble now. Another cat 3-5 hurricane in the vicinity would create just as much if not more devastation. I personally would think twice about living there. But hey, I live in Florida... no levees but barely above sea-level.

I am quite aware of where the storm went in, but thank you for the Geography lesson. So you are really not telling me anything I do not know already. In fact, since I live here, I'd be willing to bet that I know just a wee bit more than you guys do.

[T-man]

I'm pretty sure Katrina made landfall first in Louisiana,about 45 miles south of the city, as the bird flies. The eye did not pass over the city, true. However, the city was affected by the storm surge. BTW, the area of Louisiana that the storm passed directly over was flattened. The storm's surge overtopped/destroyed the levees.

[sunny]

I'm pretty sure Katrina made landfall first in Louisiana,about 45 miles south of the city, as the bird flies. The eye did not pass over the city, true. However, the city was affected by the storm surge. BTW, the area of Louisiana that the storm passed directly over was flattened. The storm's surge overtopped/destroyed the levees.

She did a pretty good job at flattening Slidell, too. Take a look at New Orleans East. Yeah, really scenic.

[T-man]

Yep, so much for being on the "good" side of the storm.

[stormtruth]

Houston, Miami, Tampa, etc are all pretty much doomsday scenarios like NOLA. The problem is with continued hurricane hyperactivity these cities will probably all see their worst scenario happen within the next 10 to 20 years. We will probably lose several major cities (that have to be rebuilt) by 2020. Everyone on the coast is pretty much doomed if you are getting 20+ hurricanes a year for 10 to 20 years. The insurers and reinsurers know this is going to happen. They continue to raise their storm damage estimates.

[jasons2k]

FWIW Stacy Stewart, just last night at Houston's Hurricane conference, stated that Katrina was far from the "worse case" for NOLA and that the brunt of the storm was to its east, in MS.

[Stratusxpeye]

I'm sorry but haven't we had enough of these "sinking city" posts already? Where are the L.A. and SF are about to fall into the Pacific posts?

Thank you.

Why are you not concerned that your sinking? WHY?

Tell you what, I'll go outside right now with my measuring stick and stand there for a while. Okay?

What was the measurment?

[sunny]

What was the measurment?

lol - I'm still out here, we haven't sunk any yet

[Stormcenter]

FWIW Stacy Stewart, just last night at Houston's Hurricane conference, stated that Katrina was far from the "worse case" for NOLA and that the brunt of the storm was to its east, in MS.

Hey just my two cents here but really how "worse" could it have really been? Okay maybe the Quarter would have been flooded too and more structural damage but come on have you seen how bad it was after Katrina? I just can't see it getting any worse. The storm flooded 80% of the city for more than a week with up 20 feet of water. In my opinion that is almost as bad as you can get.

[T-man]

It coulda been worse, no doubt. The areas west of the city, and the area south of the city, (on the west bank of the Mississippi River) remained mostly dry. Had these areas been inundated, it would have been worse.