It will take weeks to months to drain New Orleans. That's just the delay before New Orleans can start repairing itself. People with little stake in the city are unlikely to put their lives on hold for that long if they can resettle elsewhere. Is rebuilding New Orleans hopeless or is rebuilding essential? The Port of South Louisiana (just upriver from New Orleans) is the biggest port (by tonnage passing through it) in the US. The Port of New Orleans is the fifth largest. Baton Rouge is the 10th largest with Plaquemines (just downstream of New Orleans) the 11th largest. Both the Port of South Louisiana and the Port of New Orleans rely on New Orleans for their workers and infrastructure. The absence of its ports will definitely be felt through the entire Midwest. It will impact Minnesota and all other farmers in the Midwest. It will impact Latin America and every consumer in the Midwest. (The impact on coffee imports really sends chills through me - I don't think I can live without coffee.) It's absence will positively affect some cities like Houston. I think you have to have a port where the Mississippi River meets the Gulf. Houston and other Gulf ports may be able to meet the needs, but none can do so as cheaply as a port on the Mississippi.