[Lazamataz]

I don’t remember, but someone informed me that the failure talk was about the main spillway, that big hole in it.

[editor-surveyor]

.
No laz, the failure that DWR is concerned about is at the southerly end of the emergency weir.

The geology there is very “ify”

[Interesting Times]

I don’t remember, but someone informed me that the failure talk was about the main spillway, that big hole in it.

No. The issue is the emergency spillway to the left of the broken regular spillway. It's hard to detect, since it just appears as a large area of shrubs and foliage. If the top goes, the top 30 feet of the entire lake will cascade into the river below. That hasn't happened as yet, but officials consider the risk high enough to order the evacuation.

[freeandfreezing]

The main spillway isn't the problem - that water is just flowing into the river, and apart from some erosion isn't a risk to the dam.

The problem, at least according to statements from a TV helicopter pilot who was streaming live about 1 hour ago, was that water was running over the area at the end of the emergency spillway and eroding soil there, and that erosion could lead to a failure of the emergency spillway.

They ran out of daylight, but there is video showing the problem area and the traffic backups of people trying to escape Here