Poor planning and not knowing how to get the hell out of Dodge played a major role in NO's current woes. The Florida Keys are much more vulnerable than NO, with one way in, and one way out...the residents are familiar with both and have sense enough to heed the warnings and get out.
Weather people 'got out of Dodge' as you say had nothing to do with the city's current woes. 90% of the residents got out.Only the dumbest of dumb stayed. The city's current woes are because the levee walls failed.