50,000 cfm is no where close to the maximum rate quoted of 150,000cfm at the time the spillway cratered. If the flow was able to jump across the side barriers of the spillway with no prior defect and well below the maximum rated discharge, what you’ve described sounds like a design flaw.
Inspection reports reference water movement over time eroding underneath the spillway, leading up to a repair in 2013. Is this what you are referring to?
No, but it should have been. I was wrong about it not being a maintenance problem.
I said many were confused, and I was one of them apparently.
Since yesterday, I found out that trees were growing ON the spillway (which had previously never been used). When the spillway water went over them, it tore them out, likely by the roots. This would leave large holes and lead to massive erosion. Which it did.
So, it was likely both things; lack of maintenance and gambling on how much water to keep in the lake to try and get it 'full'.