New Orleans greatest assets are it's people. Now they are gone. The quickest way to return the city to any level of "normal" (if that could ever have been said of Carnival Town) is to get those people back.
Remember the scenes from WW2 of the Germans cleaning up totally devastated cities? Even if you're not as old as that, you've seen the pictures. The people who lived there were the asset required to bring those cities back. Did they evacuate the cities and wait to find all the bodies? Or remove the toxins dropped from the sky or the toxins blasted throughout the cities? Nope. Didn't have the resources.
For New Orleans to begin recovery quickly, the Mayor should post a notice in all possible ways of the addresses "cleared" and get those people back. FEMA can support this by paying a bit for the locals to repair and finish the cleaning job. What do you want to bet the people are eager to return and clean up. As soon as the water is down and people won't drown, allow the people back. If you have to have them sign a "release" of liability, fine. Just get the people back quickly.