Pete;
The slump you refer to did in fact occur, just to the north of the greenside bunker on #6 at BD. An engineered wall has been installed, with fill and turf in place above that structure consistent with the shape found there previously.
It was a 'top down' event, meaning it was local to the top of the cliff, and not caused by wave events at the bottom of the cliff....the topic of this thread.
Much of the base of the cliffs at BDGR is protected by low dunes, which effectively keeps the high tides away from the base; it is as Tom D stated, broad and tilted, with a bit of dunes to protect. However, there are also sections where the highest tides combined with winter storm waves do get quite close to the base.
There are some small sections of hole #13 at PD that are undercut by several feet, i.e., there is a dense sand layer several feet thick located a couple of feet underneath the playing surface there, with softer sand below that layer that is eroding somewhat; we do expect to see a small slump or two at some time.............again, a 'top down' event.
The strata underneath all the bandon property is essentially sand, different in origination and material from the slumps mentioned at the Olympic Club. That cliff is typical of much of Northern California.....higher clay content and relatively youthful history....as others have mentioned the entire nw corner of nor cal is rising rapidly and has alot of serpentine soils....very slippery indeed. Thus the many slumps along Hwy 1 from Big Sur north, including near Sharp Park and all the way north to the border. Back when I played OC, in the early seventies, the Ocean course holes played across large slumps, suggesting a long history of the instability of that cliff edge.
That's what I know!....not much, but hope it helps.
Tom