The French Quarter actually received little damage from Katrina the main damage being the roof of the old US Mint was ripped off which caused major rain damage into the building, the nearby French Market had a section of the sheds torn up, Rain infiltrated the Catholic Basilica in Jackson Square through one of the bell towers and entered into the grand pipe organ and minor roof damage over the area. The French Quarter being on higher ground, though sinking (look at various fire hydrants that are showing how the land has sunk around them), helped keep much of the flood water from entering it though it did get into neighborhoods several feet deep that were just blocks north and west of the actual Quarter. The main thing that Katrina did to the area was to "power wash" it and scrub off decades of pollution from the buildings that brought out the colors in the paint and roofing.