Yes, but it took time to clear those roads of debris and import buses since they drowned their own buses. And more time to chase away the armed looters. Getting them out was difficult after the flood. Getting them out when they should have would have been much easier. Just shuttle them to the prepositioned, but mostly unused, Red Cross shelters inland; they had room for 70k people there with food, water, sanitation and electricity. There was time for at least 2 or 3 trips. Maybe they couldn't have gotten everybody out but they could have gotten out a lot, perhaps enough to fill those shelters. Stage pickups at the 5 projects and at the larger hotels and the buses would fill quickly with the merely transportation impaired natives and tourists. Those with special needs should have been in a database with separate folks tasked to get them out.
"Yes, but it took time to clear those roads of debris and import buses since they drowned their own buses"
The first buss to the Astro Dome was one stolen by some kid - There are alot of school busses in the outlying areas - no excuse that these people could not get out.