The poorest 20% (you can argue with the number -- 10%? 18%? no one knows) of the city was left behind to drown. This was the plan. Forget the sanctimonious bullshit about the bullheaded people who wouldn't leave. The evacuation plan was strictly laissez-faire. It depended on privately owned vehicles, and on having ready cash to fund an evacuation. The planners knew full well that the poor, who in new orleans are overwhelmingly black, wouldn't be able to get out. The resources -- meaning, the political will -- weren't there to get them out.

White per capita income in Orleans parish, 2000 census: $31,971. Black per capita: $11,332. Median *household* income in B.W. Cooper (Calliope) Housing Projects, 2000: $13,263.

I've been wondering why people didn't leave. This is an answer. Of course, these people could have gone to the SuperDome, but it may not have been clear that was what you needed to do, and it may not have been reasonable for the disabled and elderly. Furthermore, with 15,000 people in there with broken toilet facilities and rising temperatures the SuperDome may, in time, turn into a disaster itself.