Erosion has created a 300-foot-deep hole in the concrete spillway of Oroville Dam and state officials say it will continue grow.
State engineers on Wednesday cautiously released water from Lake Oroville's damaged spillway as the reservoir level climbed amid a soaking of rain.
Situated in the western foothills of the Sierra, Lake Oroville is the second-largest manmade reservoir in California after Shasta....
I did not offer this item as if it were from a 'scientific journal'. It's a newspaper article, written by what appears to have been their science reporter. And I only suggested that it might provide a "possible explanation". That being said, I did find it interesting that this "non-professional" at least took the time to research and reference other examples where this cavitation phenomenon had been shown to have apparently damages the spillways of other dams around the globe.
OG once more: I have a general rule that might apply here. If the article has one thing obviously wrong, the rest of it is highly questionably. Saying the main spillway is 3,000 feet long when it really is 1,700 fits the rule.
Cavitation damage at the transition from laminar to turbulent flow is well-known even on smaller river structures like weirs, except I imagine that the forces at Oroville are an order of magnitude larger. I take an interest in weir design as a kayaker because some of the anti-scour designs are outright dangerous to a kayaker or canoeist, but while learning about them you also pick up layman's knowledge of the problems they are designed to prevent.
@oldestguy: If you look on google maps aerial (earth) view, it does indeed look like the main spillway is about 3000 ft long. The 1700ft number is the length often quoted for the emergency spillway. (Which is "width" if the 3000 ft is a "length"!). I'm not sure if that 1700 ft includes the parking lot, as the emergency spillway wall looks like only about 1000 ft to me on the aerial image.
OG again: I use my age as a excuse if I was wrong, 1,700 vs 3,000. After a log search found one newspaper says 3,000, so I was wrong. Anyhow, who might be able to explain these guys on the 20th, carrying road gravel, presumably to provide filtering of water entering the cobbles there behind the side walls of the main spillway? Seems like some soft of band aid to features not built right in the beginning.
The article was partly talking about issues with the Glen Canyon Dam, which has two spillways, and they could be on the order of 1700 ft long, but they're tunnels, so there's no way to get an accurate measurement of length.
<edit>
I did a crude measurement of the attached, and came up with 1524 ft for Glen Canyon Dam's right spillway, but the left one was the one mostly damaged
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Three five-gallon buckets in each hand filled with gravel? That's about 200 lbs in each hand.
Don't start any trouble with these guys. They're a lot stronger than they look.
Bill
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"Why not the best?"
Jimmy Carter
Apparently on some other sites there is an explanation for the water spouts into the main spillway from side walls. There is a drain system under the base slab, with pipes on an angle leading to side walls and then into a sloping pipe under the exterior wall backfill, periodically dumping the collected water into the sluceway. Cracking the concrete base slab in many places seems to follow that diagonal drain locations.
The question at the spillway with cracks above the perforated drain pipes tends to indicate a thinner slab at these locations. However, the mix of materials going into the product as well as the site conditions have a great deal to do with potential for cracking. A major player is the water content of the mix. Generally the higher the water content, the more shrinkage that may occur later. I've noticed on some jobs that within as little as less than an hour that shrinkage has started.
Apparently the buckets and the road gravel are filled at a lower part of the hill and the worker is just taking them back to be filled. The reported work is merely making a walking path over those cobbles for visitors.
So, these guys aren't super human after all. I was going to say that carrying 400 lbs down a hillside is an injury waiting to happen. Here is a NFL player doing it and it is a struggle for him on flat ground.
![URL]](https://res.cloudinary.com/engtips/image/fetch/w_800,c_lfill,q_auto,f_auto,g_faces:center/[URL unfurl="true"]http://www.riversimulator.org/Resources/Graphs/GCDschematicSpillwayTunnel.jpg[/URL])
