This is my understanding. The levees held. It was the flood control walls that failed. All of the mainstream press has missed this even though a spokesman from NO emergency management was trying to make the point during their special on Sunday night.
It was the flood control walls that failed.Did you see the second paragraph in post #179?
Looks to me like it was an unfortunate 'cause and effect' relationship that caused the failure ultimately; with water as high was it was, pouring over the wall, it was just a matter of time before the weakest point(s) in the system succumbed to the scouring effect. There are probably a number of other points where this was going on, and these areas will have to be back-filled to return the levee flood walls to full flood-holding strength.