There are four different places where these rivers meet, now. The first is a hydroelectric dam, taking water from the Miss and letting it drop into the Atchafalaya. The second is an Outflow Channel, for the Miss to overflow into the Atchafalaya in times of high water. The next is an Inflow Channel, to let water out of the Atchafalaya into the Miss, in a case of more localized high water in the Red/Atchafalaya system. And finally, around a long, slow turn, there's the place where boats can lock through between the two rivers. All of these structures have signs and lights and horns, warning boats away from them. The tows stuck to the furthest edge on the opposite bank. But none of these structures were working at this moderate-to-low water level, so their impact on the river was, as far as I could tell, nonexistent.
As I said in the post for day 77, it's clear that the Mississippi would flow through the Atchafalaya/Red river channel if it could. Only massive interventions by the Army Corps is keeping it from doing so. Someday, the river will win. The river always wins. I hope it's not too catastrophic for the people of the delta when that happens.