New Orleans Levee Failure Assessment - Part V

numerous

[Mudbug]

I keep coming back to the fact that neither the Orleans Avenue Canal nor Bayou St. John failed. These 2 are between 17th St and London Av, so what was different? The floodgates.

I'm the farthest thing from an engineer, but it seems like neither of these canals would have failed during the surge from the lake if they had been equipped with floodgates similar to the ones on either side of Lake Vista.

[jeffers]

Lake Pontchartrain is directly connected to the London and 17th Street Canal, with no floodgates protecting them. It is common sense then, to conclude that the water level in those canals closely follows water levels in the nearby Lake. By establishing surge height in the nearby Lake, we can establish the surge level in the canals and determine whether the failures occurred below, at, or above design protection levels.

Damage to the Lakefront levees establishes a minimum surge height of 13.5 feet, and in some cases, 18.5 feet above sea level. The US Army Corps of Engineers often proclaimed that the I-Wall design would withstand a storm surge of 11.5 feet, the canal capwalls were subjected to between two and seven feet greater surge height than that, and in three relatively small sections, they failed. If there is a problem with the levee design, it lies with those who approved it, and funded it, not those who were given a monetary figure to work with, designed a structure that could be built for that price, and oversaw construction of it.

Since it will take several years to complete any levee improvements, the current plan is to restore the levees to their pre-Katrina protection levels before next storm season.

If and when levee improvement above those levels begins, I have little doubt that the first projects will include floodgates at the London and 17th Street Canal entrances. There is a basic problem with canal floodgates in a case like this, during storms, the canals are used to transport excess drainage out of the city areas after it is pumped from low lying areas into the canals. If the floodgates at the canal entrances equal the Lake levees in protection levels, then the drainage will have to be pumped over them, some 18.5 feet instead of 14.5 feet ASL.

This is not an insurmountable problem, but it is more costly, and it requires a pumping station nearby.

If I recall, this was the reason given for why the London and 17th Canals did not have floodgates before Katrina. I strongly suspect that will change.

Again though, the USACE does not make these types of decisions. The Louisiana Congressmen and Women float funding bills to the US Legislature, if and when these are passed, the Louisiana State government decides what to do with the money and how to raise any required matching funds, the Corps of Engineers then tells them what level of protection they can provide for that sum, and if the state government agrees to proceed, the CoE then supervises the letting of bids and actual construction work.

This is why a $700 million dollar lock that nobody except a few political cronies wanted was being built in the Industrial Canal while $3.5 million dollars of "emergency lift" funding to raise the levees that were sinking went un-funded.

[jeffers]

Reference ping.

Excellent anecdotal account narrowing the time frame of the 17th Street and London Canal breaching here:

http://www.freerepublic.com/focus/news/1589796/posts?q=1&&page=41#41

Analysis (same page as above, scroll down) indicates that the London Canal protection structure failed first, probably between 9:50-11:15, most likely between 11:15 and 11:30, while the 17th Street Canal breach most likely occurred between noon and 12:15, both within hours of the eyewall's closest point of approach.

[syriacus]

Hi, Jeffers.

The recent national discussion about "breaching vs topping" brought to mind all your great work here.

Thanks again for all you have taught us.

[bwteim]

Thanks for the ping, Jeffers. Seems like we just ended last year's hurricane season and stories like these below are already circulating:

Will you be ready for the 2006 hurricane season?
Poll: Most Southeastern residents not ready for 2006 hurricanes.
Upcoming hurricane season looks to be another bad one.

[Jack of all Trades]

The begining of some relevant conclusions from reply 6 below.

..Summary, conclusions, and projections:

These are the reasons why St. Bernards Parish flooded, as evidenced above.

1. The levees sank into the marsh.

2. The money to fix the sunken levees was instead spent on airports, marinas, promenades, and fountains, with the great bulk of all funding being directed towards a lock that benefits a very few shipping companies...

Seems like it's getting clearer where the responsiblity lies. The Federal Government rather then "Destroying New Orleans", shipped money down by the trainload for flood protection. The state and local leaders just decided to party the money away.

[JimWforBush]

Thanks for the ping. How have you been?

[umbagi]

Thanks again, for both the material and the ping. This is great work, Jeffers!

Do you have all this archived in one place somewhere on the web, or are the posts FR exclusives?

[Bigun]

Thanks for the ping!

More very excellant work on your part it seems!