Katrina/New Orleans was an engineering failure. The wind was modest. The surge was modest, but put a modest natural event up against terrible engineering and you get failure.
Maybe if these people evacuate enough they will give it up. If this storm does not flood NO and they do evacuate I bet next time the people will just sit it out.
I have heard that the port of NO is so vital to the countries energy security that no matter what happens they will always build it back 13 feet below sea level or not. Sounds like a huge task to me.