I've heard of the locks. And I've also heard that, somehow, they regulate between the lake and the river. My understanding has always been that one or the other could be used to pump to depending on which source was the problem. I'm not more educated than that. The river hasn't been a problem so far. But, as someone pointed out, there will be rain water coming from everywhere north and into the river.
The river is low now, it can take the rain.
Bonnet Carre Spillway
http://www.mvn.usace.army.mil/pao/bcarre/bcarre.htm