[thecodont]

There is a hole under the emergency spillway.

Reminds me of the Old River Control Structure (Mississippi River) near-fail in 1973.

http://www.tulane.edu/~bfleury/envirobio/enviroweb/FloodControl.htm

[Ozark Tom]

Yes. Turbulent flow in the hole within the service spillway is a concern for the possibility of undercutting the concrete of the upper side. How likely is the scour erosion to backtrack toward the dam?