"Does that make sense?"
No. It makes no sense to build below sea level, ever. Period.
The French originally built the quarter on a comparatively high spot. Before all the flood control and futile efforts to tame the Delta, New Orleans was on higher ground. It no longer is, and there has been too much development in the flood plain.
Save the historic district, keep it as a tourist attraction and national landmark. Move the rest of Newer Orleans to higher ground.
I agree that it doesn't make sense to build below sea level, and that is the first thing that NO needs to do. They need to raise the city. It's been done in Galveston, Sacramento, and someone else said Chicago.
I still wouldn't put housing in a lot of NO. There's a lot of skyscrapers and hotels in the downtown area. They could keep those areas down there.
The other thing is that in Texas on the coast the houses are all built on stilts to help with flood waters. They could do the same to housing in that area.