IIRC, they opened about 1/2 of the Morganza in 2012. The engineers were real careful in determining how much water to let loose and who was gonna flood, of course they didnt have a clue and were made to look like the fools they are. Water didnt get nearly as high as they had predicted and a lot of people moved that didnt have to. Very few, if any, got flooded and that made the people mad. Not that they didn't flood, but that the corps made them move/abandon the area and none, not much, of it flooded.
They erred to the safe side.
The main thing that prevented the downstream flooding was the amount of trees that slowed the flow and caused it to disperse in a wider fashion.
