Send the Queen Mary
I know this sounds flippant, but I am serious (also, I lived in New Orleans for a few years, so I really take to heart what is happening to the city). So, my suggestion to anyone who is looking for a suggestion is send some cruise ships up the Mississippi to New Orleans. Why not? Food, water, shelter, hospitals. It's all there. Ships are like the only things that can really access New Orleans. New Orleans has wharves big enough for cruise ships. Get some there. Now.