I have friends/family who went down to bluetarp roofs after Katrina. From what I have been told:
1. Get lined up with a group that has permits/authorization to go (otherwise you may not be allowed in)
2. Bring EVERYTHING you will need (from TP to water, to food, to fuel) so that you don't become a burden or get stuck there
3. In case the previous point isn't clear enough: Be prepared for NO services, no running water, no bathrooms, no power, no stores open, nothing more than you would find camping in the middle of the desert.
Aaron Z