[DB]

It is pretty clear that the levees held during the storm.

The city was essentially dry the next day.

The questions are, did the heavy run off as the storm went north cause the failure? Did a barge or some other heavy floating object hit the levee wall and damage it? Considering the time it took for it to fail it would seem more likely water got under the foundations of the levee wall weakening it causing it to fail. The pressures against the wall were far lower when it did fail many hours after the hurricane passed through.

[CobaltBlue]

There were actually several floodwalls that failed, and several failures per floodwall.

None of it caused by canals, they don't use canals on these floodwalls.

If you ever watched the Terminator movies, or similar movies set in Los Angeles, you've seen similar construction. Concrete beds, concrete walls, solely for drainage.

[visualops]

Did a barge or some other heavy floating object hit the levee wall and damage it?

That did in fact happen. I may not have time to find the articles, if I do I'll post back.

[Ditto]

Did a barge or some other heavy floating object hit the levee wall and damage it?

If I'm not mistaken, there was a report of a loose barge in the 17th street canal during the storm. Another report said that a barge was sunk at the point of the breech. Wind and waves banging one of those big suckers against the flood wall couldn't possibly be a good thing for the structural integrity.