The citizens who live there are responsible.
Citizens of every city, town and rural community need to set up civil defense corps with shelters and supplies at the ready in every community. No waiting for corrupt and bloated governmental agencies then to "help". Forget FEMA, Jimmy Carters bloated bureaucracy that was designed to do away with self reliance and civic responsibility through civil defense.
Citizens need to remove every politician and bureaucrat implementing "smart growth". "Smart growth" creates very dense cities and developments where people are discouraged or not allowed to have private transportation.
Note that New Orleans evacuation plan stated that private transportation should be used to evacuate people, knowing that there are politically created "smart growth" areas where the people have no private transportation. The concept of controlling people through "smart growth" is criminal beyond belief and has no place in a free society.
Bravo, you nailed it.
Citizens must expect that government will screw things up, and they must be prepared to be self sufficient.
In the end it isn't government's fault that people in New Orleans died, it is the fault of those who relied on government to protect them.