And that's the problem. The levees were supposed to withstand a Cat 3. They couldn't hold out strong Cat 1 winds, which is what NOLA got hit with on the weak side of Katrina.
If they are built to supposed Cat 5 specifications, do we really know what that means? Recall that Jim Cantore was in a location where the NHC thought there would not be surge - and he had to help evacuate veterans to the second floor. What if tens of thousands of NOLA residents stay behind, believing that the new levees would hold back a Cat 5 - and they don't?
It's insane to try and keep the parts of NOLA that are well below sea level from becoming a lake. Rebuild a smaller NOLA, move residential areas to higher ground further west, and avert the future tragedy.
The wrecked area could be the perfect place for a refinery farm. Major port, importing oil, exporting refined products up and down the Mississippi River an elsewhere? Sounds like a plan to me.