INVESTIGATION of the LEVEE BREACH? How did this happen?

[bj2110]

I don't mean to ruffle any anti-conspiracists, and while I wholeheartedly disagree with any notion that a hurricane can be manufacturered, I can't wrap my arms around one devastating event:

How did the Levee fail?

We've all seen the pictures of the water flowing through the huge 300' breach in the levee system along a canal from the Lake. But how did the huge structure fail? How did it collapse? It wasn't a storm surge flowing over the tops of the levees that caused the bulk of this flooding, it was the structural failure of the levee itself.

Now, I'm a civil engineer by trade. I have designed dams and water containing structures, albeit in engineering classes, and have been in the practice of designing steel structures as a structural engineer for many years. I know quite a few basic engineering principles, although I am not very educated on levees, as they are different sorts of animals. Basic 2-D forces on a water containing structure are directly based on the depth of water being held back. Forces are large at the base of the structure.

I guarantee these levees were structurally capable of carrying a water level to the tops of the levees. I guarantee it wasn't the wind that destroyed these structures, as even a 130 mph wind only exerts 30 - 40 psf of wind pressure. However, many times, river flows and the third dimension of movement will impact the strength of a structure, i.e. a fast flowing river, and this very well may have had occurred here as there was no doubt flow in the canal from the lake. Also, perhaps the foundations could have been compromised from a build up of water on the opposite side of the levee.

But the real question is how long it took for the levee to fail. I would imagine that one of the key variables to capacity deterioration due to both water flow and foundation compromise would be exposure time. The longer the water is at a high level and flowing, the less capable the structure is of containing it.

But, here, the levee failed after what, 5, 10, 15 hours? It wasn't much more than 15, and who really knows? That doesn't seem like that much time to, considering upstream surges of the Mississippi River take days to subside.

My point here is not figure out how it happened. I am only trying to point out that a failure of this type of structure is highly unlikely, even in the event of a huge storm surge. I have confidence in the engineering profession, especially considering life-safety structures get safety factors of 2, 3, sometimes 4 multiplied to the anticipated event.

I urge a call for the investiagion into the levee breech. If we accept that the levee should have maintained itself due to the engineering principles used to design, build, and maintain it, then we must accept that there was some unnatural force acting on the section that failed.

Whether it was a governmental conspiracy to exaggerate the effects on the oil industry and give credence to our presence in Iraq, an attack on the poor, black, inhabitants of NOLA, or just a single criminal with a bomb, this must be investigated. I can only hope that there is enough forensic evidence to piece together what really happened to the levee.

[whistle]

1. All started back in 2001 when Bush rejected plans to reinforce

...New Orleans levy system and other recommendations from a $500k study and did nothing and diverted all funding to other purposes leaving the city wide open to the next catastrophe. The republican congress went right along with it.

[bj2110]

3. I'd like to know howo ld the breeched section was, when was it built?

[Inland]

2. Current theory is water rushing over top of

section that was four foot lower than the rest (thanks to Bush not funding projects) undermined the earthenworks supporting the levee.

Therefore I don't accept the levee should have maintained itself under engineering principles.

[bj2110]

5. Who's theory? And how quickly did that theory promulgate?

A full investigation should be called for. It's dangerous to let these theories take hold....

[Inland]

12. I've got no problem with an investigation.

But come on, there's no reason to believe in the MIHOP stuff.

You can check out the discussion in todays www.chicagotribune.com

[bj2110]

14. Discussion where at the tribune site?

[madeline_con]

4. One word: water.

I hate to bust your bubble, but you'll have that with huge storms the size of Katrina.

[bj2110]

8. We know a lot about water. Engineers make careers in dealing with

it's destructive powers. Such a simple response is naive...

[shance]

6. Great point. Certainly deserves proper investigation.

n/t

[mikeiddy]

7. Destined to Fail

I seem to recall reading in The Control of Nature by John McPhee that it is the height of hubris to think that we can control the Mississippi River - that all levees are destined to fail against the power of water.

That having been said, it seems to me to be the height of irresponsibility to have intentionally defunded flood control around New Orleans.

[bj2110]

11. I totally agree. Over a long enough time, every structure will fail, and

those dealing with a force as large as the Mississippi River are no doubt accelerated in that timeframe. But, this was lake water, this was a storm surge.

And yes, without proper maintenance, the levees were doomed. But, we must understand exactly how they were doomed. How should the money have been spent if it was available? We must investigate.

[MsTryska]

9. I could have sworn I read soemwhere

on here, maybe that that section of levee had been recently rpaired, but they hadn't completed the fortifying process (hardening it?) I guess because they ran out of funds.


i could totally be pullign this out of my ass tho.

[hnsez]

10. I'm a geologist and can tell you how one of them broke

After looking at all the photos... the levy that consisted of a concrete wall failed after erosion at the base made it unstable and the water pressure simply pushed it over. It became unstable at the base because of water flowing over the top of the wall. Water was flowing over the top of the wall at that location because of 2 things:

1) the nearby "bridge" (more of a roadway) barely cleared the top of the levy. Tons of floating debris floating with the current in the canal was trapped against the side of the "bridge" during the storm and this created an impediment that raised the water level behind it. The cross-sectional area for flow under the bridge had decreased.

2)The raised water level found the weakest point - where the levy wall had settled slightly more than the rest of the wall had and water began to flow over it at that point.

3) Water spilling over the wall eroded the soil at the footing that supported the wall and eventually that section collapsed.

I would investigate surveys of that section that showed settling, reports that advised raising the bridges, and reports that advised placing anti-erosion measures along the base of the wall along the outside of it (particularly where the wall was lower), and studies that advised creating controlled failure points where overflowing water could occur safely without eroding the base of the wall.

the best designed systems fail in a controlled way to minimize damage and speed recovery

Where is my check?

[bj2110]

13. Good theory. Now, it just needs to be backed up with a proper...

study. I still have a hard time accepting how quickly this all happened. Ground is usually sloped away from any water containing structure to help with the control of surface water. Although this can only work for so long, a breech in just a matter of hours seems a little quick for me with the failure mode that you described. Don't get me wrong, I understand what you're saying, and it does seem logical.

[Xithras]

18. We have levee failures in N. California regularly. It just takes seconds.

These aren't concrete structures, but compacted earth and rock. Once water begins flowing over the top of them, ANY structural irregularities will allow erosion to begin within minutes, and a 6" breach can expand into a top-to-bottom breach within minutes. Once that happens, only an immediate attack to plug the breach can keep it from expanding.

The process has actually been witnessed by news helicopters here in California during the various floods, and is well understood. Short of building your levees out of solid concrete, there isn't much you can do about it.

By the way, "structural irregularities" can be many things. We had a several thousand acre island on the delta flood last year when the levee failed, and the irregularity that caused it is now believed to have been a frigging GOPHER HOLE. That hole allowed water to seep through, and according to witnesses it took under 15 minutes to go from a leak with the volume of a garden hose to a 10 foot wide breach.

[BeFree]

21. Your check is being held up

One problem with your theory:

1)" the nearby "bridge" (more of a roadway) barely cleared the top of the levy. Tons of floating debris floating with the current in the canal was trapped against the side of the "bridge" during the storm and this created an impediment that raised the water level behind it. The cross-sectional area for flow under the bridge had decreased."

The picture I saw showed the bridge upstream of the breeched levee. Clearly, a dam upstream would not cause a downstream overrun.

[Poll_Blind]

15. There was a rumor that the levee had been dynamited in an...

...attempt to "save the city". Apparently shortly after the levee broke this rumor started to circulate. I don't understand how it would save anything, but I'm repeating what I read. I read this on, I think, NOLa.com in one of the message boards (I think St. Bernard Parish). The poster was mentioning it, trying to disabuse readers of the rumor, so it appears that the poster assumed that others would know about it.

Sorry, just checked NOLa.com and it doesn't look like the forum I rember reading this on. It's the place that had a separate subforum for each parish.

PB

[craigolemiss]

16. hard to imagine that it could happen in a Western country

Experts in the Netherlands expressed surprise that New Orleans' flood systems failed to restrain the waters.
With half of the country's population of 16 million living below sea level, the Netherlands prepared for a "perfect storm" soon after floods in 1953 killed 2,000 people. The nation installed massive hydraulic sea walls.
"I don't want to sound overly critical, but it's hard to imagine that (the damage caused by Katrina) could happen in a Western country," said Ted Sluijter, spokesman for the park where the sea walls are exhibited.

[Jacobin]

17. Its been predicted for YEARS

It was why N.O was under a mandatory evacuation before the storm.

Water and wind wash away dirt.

[KamaAina]

19. I believe it was undermined from within (on the N.O. side)

It happened hours after the storm had passed, AND several blocks down from Lake Pontchartrain itself, so it is unlikey that storm surge alone caused it to happen.

But the area where it happened (Lakeview) was one that had lots of floodwater from the storm -- maybe enough to cause the failure.

Sounds to me like a case of poor maintenance. And don't you know, the repuke criminals embezzled, er, I mean "diverted", money from the Army Corps of Engineers to pay for their oil war in Iraq! :grr:

[oasis]

20. Best answer yet. (nt)