[TXnMA]

It appears that one critical point is in the center of this image, where the erosion is already back up to the concrete lip of the auiliary spillway's "lip cap".

Per other photos (Gannet -- can't post here) the erosion at the far side (top) of this photo is much deeper.

The critical question is "How deep does the vertical concrete face of this structure (right side) extend?" (i.e. "How deep must the backface erosion (left side) reach before water tunnels under and destroys the whole structure?)"

[444Flyer]

“The critical question is “How deep does the vertical concrete face of this structure (right side) extend?” (i.e. “How deep must the backface erosion (left side) reach before water tunnels under and destroys the whole structure?)””
__________

Sounds like this in reverse:

“Model Dam Fail”

https://www.bing.com/videos/search?q=model+dam+fail&view=detail&mid=C283D1CB1C47BAC91C28C283D1CB1C47BAC91C28&FORM=VIRE