Very true, it's like the tsunami, if people had known what was coming, they would have gotten the fuck out of dodge.
Of course, the problem with Katrina was that some people did stay and after that, all the material damage that had been done.
I doubt much more could have been done about Katrina though, those there were not going to leave anyway and after the fact, there wasn't much that could be done.
With all due respect, I think you might not grasp what happened with Katrina and the aftermath.
There is a lot of blame to go around, here are some highlights :
(1)- People unwilling or unable to leave the area. (you mentioned this)
(2)- Disagreement and doubt about whether or not the levees would hold. Mobilization of the resources necessary to deal with the potential consequences of the levees breaking didn't happen.
(3)- EPIC communication failures between state and federal agencies, and with civilian relief agencies which for the most part had to go it their own way.
In the final analysis of the situation, one can really only come to the conclusion that FEMA should have been a lot more proactive about taking over the situation when it became clear that things were wildly out of control. FEMA was still suffering the political destabilization that occurred as a result of being folded under DHS directive, which was in many people's minds a confusing move. Sure, FEMA and DHS should talk effectively in the situations which warrant it, but they serve vastly different functions and should never have been merged in the way they were. The final insult was that the head of FEMA was one of the worst appointments ever made. The guy had ZERO work history, knowledge, or even common sense ability to do the job he was tasked to do. He was a purely political appointment that made terrible sense, and by not rising to the task he and his agency failed to save many lives during that ordeal due to unnecessary negligence and incompetence. Do I think Bush planned this on purpose? Of course not, it was just a cronyist move that backfired.