The Houston Chronicle mentions the flooded schoolbuses and NO's disaster planning here:
...The mayor's mandatory evacuation order was issued 20 hours before the storm struck the Louisiana coast, less than half the time researchers determined would be needed to get everyone out.
City officials had 550 municipal buses and hundreds of additional school buses at their disposal but made no plans to use them to get people out of New Orleans before the storm, said Chester Wilmot, a civil engineering professor at Louisiana State University and an expert in transportation planning, who helped the city put together its evacuation plan.
Instead, local buses were used to ferry people from 12 pickup points to poorly supplied "shelters of last resort" in the city. An estimated 50,000 New Orleans households have no access to cars, Wilmot said...
Hospitals were exempted from the mayor's mandatory evacuation order. But at least two public hospitals, loaded with more than 1,000 caregivers and patients, had their generators in their basements, which made them vulnerable in a flood. That violated the state's hurricane plan but had gone uncorrected for years because the hospitals did not have the money to fix the situation, a state university hospital official told the Chronicle...
...Tami Frazier, a spokeswoman for Mayor C. Ray Nagin, currently working out of Houston, refused to comment on direct questions this week or to answer several written questions sent via e-mail. She cited the need to focus on rescuing citizens and recovering bodies....
...The city of New Orleans Comprehensive Emergency Management Plan suggested people develop their own way to get out. "The potential exists that New Orleans could be without sufficient supplies to meet the needs of persons with special considerations, and there is significant risk being taken by those individuals who decide to remain in these refuges of last resort," it says.
People who called for information on special needs shelters Saturday were directed to sites in Alexandria and in Monroe, La. - cities 218 and 326 miles away. The state scrambled to find 20 ambulances and some specialized vans to pick up fragile residents who needed rides.
"There were transportation systems in place to take people out of New Orleans, which was the preferred solution," said Kristen Meyer, a spokeswoman for the Department of Health and Hospitals. But she's not sure how many got out...
...Florida, by contrast, for two decades has required counties to establish and maintain permanent databases of "special needs citizens," and arrange rides for people with no transportation. The state also has shelters established for myriad medical conditions...