[Enchante]

"Actually were it not for human-built structures the Mississippi would ALREADY be going down the Atchafalaya"

Yes, so I guess what I'm wondering is if the dams and levees that the Army Corps of Engineers has been using for decades to keep the Mississippi on its present course are vulnerable or not. I have no idea, I'm just wondering what it would take in terms of water flow to overwhelm the existing system, and would that have permanent effects?

[Wonder Warthog]

"Yes, so I guess what I'm wondering is if the dams and levees that the Army Corps of Engineers has been using for decades to keep the Mississippi on its present course are vulnerable or not. I have no idea, I'm just wondering what it would take in terms of water flow to overwhelm the existing system, and would that have permanent effects?"

I grew up in north Pointe Coupee, which is just north of the Atchafalya Spillway and south of the Old River Control Structure (which are the main two "flood control structures" to keep the Mississippi from "re-channeling" down the Atchafalaya, and they are designed for (as I recall) an amount of water 3X the 1927 flood (largest of historical record). No hurricane is going to drop that amount of water, and those structures are so massive (and low) that they are invulnerable to wind damage.