Once the storm passed and the levees were patched, dewatering and cleanup began immediately. Areas of Louisiana, Mississippi, and southern Alabama were so devastated that it resulted in one of the largest disaster response mobilizations in the United States. Then, of course, came Hurricane Rita, which flooded parts of New Orleans all over again.
Dewatering a city the size of New Orleans was a Herculean task, but the bigger question will be: How many buildings can be restored? In the hot and sticky climate of the Southeastern United States, mold is always an issue anyway. Buildings that were submerged under water for two or more weeks will not only have mold issues, they will also potentially be contaminated from all the pollutants that were in the water. Even buildings that weren't flooded will have problems, since many were without power for days or weeks, giving mold and mildew an ample opportunity to flourish in the non-air conditioned environment.