The main spillway is between the dam and the emergency spillway. The main used to be a rectangular concrete channel. Part of that failed and the high energy water flow did the rest. They can suffer much more erosion below the emergency spillway without too much concern. Much more along the dam side of the main and it could start to soften the base of the dam. Maybe even remove enough material to not have enough weight to withstand the pressure. My guess is they’ll let the main run as much as they can, but once it gets maybe 1/3 closers to the damn they’ll cut way back. The emergency spillway will have to take the rest. If the rains are as bad as predicted, I’ll say 60 to 75% chance they lose the spillway wall and 20 ft of Lake plus the new rain.