I was watching a segment where they showed a section of NO that was relatively unaffected by Katrina. Many of the people didn't evacuate but are perfectly fine. They have power and running water and most have enough bottled water to last several months.
The thing is, despite the fact that section is peaceful and under control, the police still come by and demand that those people evacuate. Why?
So the police can loot. The folks in the area said that their neighbors who DID evacuate had their homes looted by the cops not long after the storm subsided, and the people that have left since then have had their homes looted by cops within hours after leaving.