dmccarty,
I agree completely.
It seems they never believed the emergency spillway would actually be used. They had no logical reason to dismiss the recommendation to pour concrete at the base of the spillway.
Sure enough, when it was actually used it began to fail immediately, as could be expected.
We just don't know how stable that lip is. Maybe it could be severely undermined and still hold. Who knows. But if it fails the draining would be spectacular.
If you look at some of the pictures where the water is going over the top, you can see it is also spilling over the small edge alongside the parking lot. A parking lot curb is part of the main structure holding back the water! Eeeek.