Very interesting stories. I think I can debunk a couple of them.
The Cow Creek stories are interesting in that East of Redding there are TWO Cow Creeks. One is called "Cow Creek" and the other is named "Old Cow Creek." I have personally walked the banks of Old Cow Creek several times in my pursuit of the wily wild rainbow trout I have not been back to that stream since the 1960s due to work, family, etc. There is in fact a waterfall (about 30 feet high) that is part of OLD Cow Creek. Perhaps the story has been corrupted through the years and the original stories were about OLD COW CREEK. However, I have never ever heard of anyone finding any gold in that creek and surely if there was gold in it or near it someone would have found some by now.
As far as the story about a rich ledge in Scotts Valley near Kelsey Creek, nope. Although there has been gold found in Lake County and in Kelsey Creek itself, such gold has been associated with hot springs and has been fairly insignificant in amount. There was/is a large gold mining operation at the union of Lake, Napa, and Yolo Counties called the McLaughlin Mine which was developed by Homestake Mining. That gold is far from Kelsey Creek and Scotts Valley and it is not particularly rich, just spread over a somewhat large area. Not a "rich ledge" that's for sure. I had an uncle and aunt who lived in Scotts Valley, Lake County, California for quite a long time and they never said anything about anyone finding any gold in their area. And they knew just about everybody in the area (and in Lakeport) some 30-70 years ago when they were still living.
Have you heard anything about the Hall Cave stash? Hall Cave is real, it's in Trinity County, and the story is famous. That's another interesting story that someone debunked. A few years ago somebody used scuba gear in the water-filled cave and searched the sides and the bottom. NOTHING, but a beer can I think he said. That 2-part article was published in W&E Treasures Magazine a few years ago.
Makes me wonder why/how these stories get started. I'm sure they start out with some facts or evidence but they get screwed up through the years and through the people telling the story. There are sure to be some that pan out, but not many. Makes good reading though. Thanks for posting the link.