I don't even think it's a matter of fixing them. Study what happens when you evacuated a major city, develop best and worst practices, and add that to the models for natural disasters and attacks, and get ready for next time. I still say the feds weren't slow what with the CG et al plucking 15K off the rooftops, and then airlifting them out of the convention center with a mighty air armada. Feds aren't allowed to police, so they can't blame the lootin and shootin and rapin and robbin on the feds no matter how hard they try.
Louisiana DID a disaster exercise that was a lot like what happened with Katrina.
And for all the good it did, they STILL didn't implement the city or state disaster plans.