If I saw it right,the service spillway isn't part of the direct face of the dam. The concrete bottom of it failed so they shut it off. Due to the expected inflow, the reservoir will continue to fill faster than they can let it out. They have been running the hydroplants full out too.

I did see a video today that showed the spillway sidewalls failed, so they must have resumed releases figuring additional damage did not threaten the dam itself.

There is another spillway at full pool. This spillway is for emergencies and the lake has never gone over it. If it does (like most dams), there will be no control and downstream flooding.