There are gaping holes.
And then there is not even trying. Which IMO happened here - there was NO PLAN whatsoever to get out those without transportation - including tourists. How can a friggin' tourist town not have a plan in place to get stranded tourists out?
Ever been trapped at an airport during a major storm?
New Orleans is a metropolitan area of about 1.4 million people. Add several thousand visitors at any given time. I don't care how much planning you do in advance . . . there is simply no way to move that many people out of a city without starting the process WEEKS in advance.
I had the "pleasure" of evacuating Manhattan during the blackout of August 2003. I was one of the lucky ones because in a matter of no more than 10 seconds I knew exactly what I had to do (I headed right for a nearby ferry terminal because I figured that the diesel-operated ferries would be running even if the electricity wasn't restored for hours or days). It took a long time, and lots of people ended up sleeping on the sidewalks outside the major train stations in the city -- but eventually everyone got home. A government can't possibly prepare to evacuate a major city in an orderly manner.