The Mississippi “River” is really, more or less, a system of long lakes and channels and concrete from Lake Itasca to the Gulf of Mexico. At one point in Louisiana, only a fortress of concrete keeps it from switching banks and heading to the southwest. Any serious disrpution to this system and it will happen.
If anything is left of New Orleans after this hurricane, there may be nothing left of the old Mississippi there either. Without the flow of the river, the seawater will back up further, and, indeed the industrial shipping on the river there will end.
update: the river and NO both made it. This time.
update 2: I guess they gave the all clear too soon. It’s getting worse down there. It’s apocalyptic. I still don’t have any information about the river controls near Simmesport, LA about 50 miles northwest of Baton Rouge, where the Miss is trying to change course (and would wipe out Morgan City)