They surely could of hit high ground in 48 hours. They as free people, living on the surface of this planet made a conscious decision, weighing the risks involved and chose to stay. Free people have the right to decide their fate. The government may suggest you leave your house, but they cant force you. People who decide to stay, also have an advantage over those who flea, in that they are able to protect their property from looters and do not have to wait for permission to return.
Do you have ANY clue as to the geography of Louisiana? Apparently not. They would walk for two days and be out in the open in a major hurricane. That's really friggin' brilliant. Are you sure you ain't one of the disaster planners that used to work for New Orleans?