I realize this is sort of tangental to our topic, but...

I wonder if in the end we might have something like the Seattle underground. If you aren't familiar with this, let me explain:

Seattle was situated almost at sea level. When they got toilets, and thus sewers that had to flow downhill, they litterally raised the level of the city, but left the city with two levels: the old underground and the new above ground. The old underground is now a location where tourists can go on guided tours.

If New Orleans has to be rebuilt, I wonder if they might do something like that to preserve the historic nature of some parts of it, yet bring it above waterlevel for everyday use.