Though nobody yet knows the full extent of the damage, 80 percent of New Orleans has been flooded since early this week. Even under slightly better circumstances, Carliner says, the majority of homes, including many historic ones, could not be salvaged.

"With clean water, if you submerge a house for a week, it's not going to be livable anymore," Carliner says. The water that has inundated New Orleans since levees against Lake Pontchartrain failed is polluted with chemicals and sewage. "It would be very difficult to get those contaminants out of the houses."