The New Orleans Levees
The New Orleans Levees
(OP)
Does anyone have thoughts or links regarding the technical details of what caused the Levees to fail and how they can be repaired?
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RE: The New Orleans Levees
Probably best repair is to plug the gap with barges filled with rock and scuttle as the main anchors.You can then fill any remaining gaps by rock and place rock around the barge and grout both the barge and surrounding rock .
Prepakt
RE: The New Orleans Levees
RE: The New Orleans Levees
The water falling over the floodwalls, however, scoured the floodwall foundations on the city side of the levee enough that the water pressure behind the floodwalls was enough to topple the walls. Finally, the scour from the wall of water unleashed by the breach in the floodwalls eroded the levee through.
Reportedly the floodwalls were designed to handle water levels due to "only" a Category-3 hurricane.
Like many others, I suspect that the disruption in the US and global economy may warrant a re-examination (with respect to cost-to-benefit) of the design criteria for the water management and flood protection of the whole New Orleans and environs area.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: The New Orleans Levees
RE: The New Orleans Levees
RE: The New Orleans Levees
At this point I think they would be better off to drive a celluler dam outbord of the break so that once it is pumped down, they can repair the levy. My question is once they pump down, will tey rebuild the levy and the city below lake level, or will they fill the site to an elevation above lake level?
RE: The New Orleans Levees
Regarding cvg comments on enforcing a mandatory evacuation, many people are poor and cant really just 'get up and leave' that easily. The governement should have provided busses or some other way to get them out before the hurricane. The hurricane center predicted the category 4 level and where it would go right after it went past here in Fort Lauderdale, and the feds still did not prepare ahead of time. Quite unbelievable.
RE: The New Orleans Levees
This should show everyone the difference between real planning and lip service. Most governments in this country are very very good at giving lip service the problem on the moment, but when it comes to real planning and setting aside resources to cope with problems, they fail completely. I don't know if this is a reflection of our socity as a whole or just the way our elected officals behave due to the short election cycle that puts them in office.
RE: The New Orleans Levees
I can think of a couple possibilities. There are probably others.
1. The money is promised for rebuilding of levees high enough to prevent reoccurrence - $100 Gig??? People rebuild at existing grade. Maybe my yet-to-be-born grandchildren will get jobs designing the new levees.
2. Money is found for only modest levees. Poor people rebuild at present elevation. Government agencies, corporations, and wealthier people, acting individually and jointly, buy nearby properties to use as borrow areas to build up their own sites. Borrow areas become wetlands. City becomes smaller, and therefore very expensive to live in.
RE: The New Orleans Levees
As I understand it, the entire Levee is built to the same height and there is no control over the location where it will overflow and no ability to predict it.
So, knowing that the Levee might possibly be exposed to levels beyond it's capacity, why wouldn't we have designed the Levee with strategically placed overflow "notches" at perhaps a level of 1' below the top. The Levee could be reinforced in this area with some structure to guide the water away from the Levee to minimize erosion.
Presumably with this type of setup we might have topping of the Levy slightly sooner, but when the surge subsides and the Lake drops below the level of the notch, the water stops flowing.
It seems to me a necessary design feature. A parallel situation is a pressure vessel whose purpose is to contain pressure. If the design pressure is approached, a relief valve actuates which reduces pressure... momentarily disrupting the function of the pressure vessel but preserving it's ability to function after the overpressure condition is relieved.
Of course the ideal solution now is to build the entire Levee greater than the category 5. But I am looking in retrospect at the Engineers that were designed the resources for the full category 5 and knew there was a possibility the level might exceed the top. Wouldn't notches have been a good low-cost design feature?
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RE: The New Orleans Levees
"Of course the ideal solution now is to build the entire Levee greater than the category 5. But I am looking in retrospect at the Engineers that were denied the resources to build against the full category 5 and knew there was a possibility the level might exceed the top. Wouldn't notches have been a good low-cost design feature? "
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RE: The New Orleans Levees
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RE: The New Orleans Levees
RE: The New Orleans Levees
Flooding near Wuhan should now be a thing of the past with Three Gorges Dam nearly finished upstream. Saw it a few weeks ago, and it is IMPRESSIVE (in ways both good and bad). As our small cruise ship went through the locks, I realized that the locks alone were bigger than any project I've ever worked on and probably ever will.
RE: The New Orleans Levees
Ummm. Could be. Just heard on CNN something about another break 8pm cst 9/12.
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RE: The New Orleans Levees
You are thinking like engineers. As a geologist, I see this as a never ending race, the levees will never be high enough. As Lake Pont. fills in with sediment the lake level will continuously rise, requiring the levees to be made higher and higher.....
RE: The New Orleans Levees
RE: The New Orleans Levees
RE: The New Orleans Levees
As the lake fills with sediment, the bottom of lake Pot. (I couldn't spell it if I wanted to.) will rise. The surface of the lake will always be at about the level of the Gulf. Eventually you would get a bog. The top of the lake will not rise except for tides, storm surges and local fluxuations known as seeches
RE: The New Orleans Levees
RE: The New Orleans Levees
the levees have been repaired on a temporary basis . These areas are still weak.Some seepage will occur due to lack of time for full compaction of the gravel and bag repairs.
Some suggestions or thoughts on the problem.
Place bentonite matting along the outside of the repaired areas it comes in 20mm thick rolls and cover with re-inforced flexible concrete matting anchored to some new piling.This will cut seepage and possible failure significantly.
At the beginning of this thread I mentioned rock filled barges.They should be available along with some heavy duty tugs.
The principle here is that at the first sign of seepage/ failure a barge should be moved into the failure area and the bottom blown out. If a large area is failing several barges can be used in a brick layer pattern and the ends between the barge and the shore filled by rock.This will hopefully reduce the water flow and permits repairs to proceed.
Intrusion Prepakt
www.marineconcrete.com