The turbulence might be caused by water flowing over the retaining wall near the gate.
There is a small berm or ledge atop part of the retaining wall and appears to be what is sticking out of the water in the circled area of the photo in #1320
Great picture, thanks.
It gives a perspective that I had not seen before.
Dam design construction blueprints show this incoming waterflow channel as the "approach channel". The far side wall of this waterway "approach channel" is the "Cut escarpment".
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.
What is of note is that the composition of this apron, with trees growing in a "soil or aggregate/soil" base is not a protected surface if turbulence were to occur (notice the grooving in the berm from equipment).
This turbulence, brown discoloration in other images, and the soil/aggregate design of this inlet has been the source of heated discussions in whether there is a risk of an "erosion scouring" at the entrance to the Main Spillway inlet (approach wall). This would be a serious condition.
Of course, the huge "bubbles" that were caught by the Fox10 helicopter crew overflight in front of the Emergency Spillway weir suggests that there is a porosity potential via the soil -in front of - and the now known layer of "fractured rock" that the ES rests upon.
The approach channel likely has this same substructure. Laminar flow is very important to prevent scouring with any non-armored surfaces.
That is a massive dam...reassuring ...The Spillway migt go ouy buy yhjr fsm eill dutvivr.Downstream stuff will get damaged of course.