The Christian Science Monitor reports that a geological fault might number among New Orlean's enemies. The article suggests that about 6 feet of New Orlean's sinkage in the last century might be the result of geological movement.
It seems to be the nature of this planet that parts of the earth go up and down. Glaciers advance and recede, floodplains fill up and drain. Volcanos go boom.
In such a world, one would expect to see an occasional loss of a city.
Of course, Suggesting that we not rebuild the "Chocolate City" would be racist. Yes, I wouldn't want to locate a business there, but we can have a major city where everyone lives on the government's tab. The free market's response to geologic change is migration. I guess that can be taken as yet another sign of why the free market has failed and should be avoided. I still can't help but wonder what, if any sign, we humans should take as an indication that a city must be abandonned?