“This enlarged image shows trees growing in the berm/embankment that what looks like a concrete wall that joins to the upside down “J” of the curved “approach wall” inlet.”
Comparing this image with the image you posted in #1320 showing the turbulence before the spillway gate, it appears to me that the “upside down J” approach wall is gone, and may have collapsed.
The concrete wall that joined it remains, and the earth that abutted it on the near side has eroded away allowing water to flow on both sides of it, but at least two of the trees remain.
If true, could this be the cause of the turbulence you circled in #1320?
“J” wall still there. It’s just that the water was so high it was covered up. The whole main spillway structure is solid concrete and is anchored/imbedded in good solid bedrock.
If you zoom in on the photo in 1342 you can see that the rock is higher than the wall.