thanks. should have scrolled back further i guess
they must have moved it as i dont see anything in the water on the 17th eitehr
interesting example of non-local reporters not knowing what they are talking about. He says he doesnt want to go closer to the river at that time (7:11 in vid)as hes afraid the 'dam' might breach.
No disagreement. I appreciate Sushi adding the USGS topological map in post 1203 yesterday. Sushi observed and highlighted a topological feature, and I added a picture showing the same feature.
I have very similar looking debris islands in the field behind my house. There's a seasonal creek that runs down the hill that's run about ten times as much as normal and is grinding through the hill. . It has created very similar looking flat topped "islands" of essentially coarse grained sand and mud where the water reaches a flatter area and slows down. Scaling that up I'd expect these "islands" to consist mostly of medium sized stones under a foot in diameter.
I'd take a photo, but it's raining here
Welcome Lurajane.
Your image, and the vantage point it contains, helps make the situation a little more clear. I have added some additional annotation.
The red oval with dark red center is located at about the point of initial spillway failure. Since that time the spillway has eroded to include much of the area inside the yellow oblong. The dotted red arrow pointing down to the river overlays an area through which the spillway flow has carved a new erosion outlet.
Thanks! I wonder what the river level is at the powerhouse is today? A few days back I saw a post indicating that they had 8' of freeboard, before "flooding" the powerhouse (whatever that means). The debris island certainly appears to be larger than that we saw three days ago, but I recognize the spillway flow is lower so it can be misleading. I also saw an article in the LA Times (dated 3 days ago) that 150,000 cu.yds. of debris have clogged the riverbed, and presumably most needs to be cleared. This number came from the authorities (Mr. Croyle). I wonder what the current estimated debris accumulation is? **link added below**Screenshot from that AccuWeather video showing a closer view of the debris island.
Full video just ended live feed. Screenshot taken at about the 2:18 mark:
https://www.facebook.com/AccuWeather/videos/10154965453052889
You can link to anything, you just need an excerpt so people don't need to click on the link (i.e. the link is a reference)
Just listening to the recording, and one thing was not clear. They plan on going dry in the main spillway for a period of time, and currently the powerplant is not passing water. Do they have a bypass tunnel/channel somewhere to prevent the river drying up? Or will they maintain a small flow down the chute?
The stilling pool that the spillway runs into is itself a dammed lake. So they can maintain releases from there into the river.
It also has a few other inflows from other watersheds
Sorry, but this is get back towards the type of long pointless speculation I wanted to keep out of this thread. There's sections of ravines all over the place. This particular one (if you arbitrarily extend it) crosses the ravine 400 feet below the site of the original damage and has to cross a ridge to get there.
It's needless speculation, and it's cluttering up the thread. Obviously the ground under the spillway varies.
In related news, the similar Don Pedro Dam is using its spillway today
Source: https://twitter.com/TurlockID/status/833818231894794244/video/1
They have a kind of hybrid gated/emergency spillway that drains down the same unlined ravine. Not very steep though.
They don't use it much. It runs over a road.
Source: https://twitter.com/TuolumneSheriff/status/833821289223589889/photo/1
The word you want to use is geomorphic feature. Geomorphic features can provide great clues and are often evidence of other processes or features.
Bedding planes imply original horizontality. Volcanic intrusions such as sheeted dikes are never emplaced horizontally, that would be called a sill, so the correct term here is layer.
Here's the road last time they opened it in 1997. They say it will be "nowhere near" this level this time.Wow. I suspect that road will need some work after they are done... I hope we don't have to start another thread.... (my golf course opens tomorrow in Surrey BC)
Greenstone is a name given to several different types of minerals and rocks.
- Pounamu, a form of green nephrite jade found in the South Island of New Zealand
- Chlorastrolite, found in the Keewenaw Peninsula of Michigan and Isle Royale in the US
- Elvan, a quartz-porphyry found in Cornwall, UK
- Greensand, glauconite bearing sandstone and a geologic formation in the UK
- Greenschist, metamorphosed mafic volcanic rock and a metamorphic facies
- Greenstone (archaeology), a type of stone used by early cultures, particularly in Mesoamerica
- Greenstone belt, Archean and Proterozoic volcanic–sedimentary rock sequences
if you scroll up to post #1252 youll see a geological map. you can also look for 'geology' links within this thread, as the rock has been discussed pretty intensively. Theres a brief summary of the thread here, that might help you locate info.Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle. The mineral alteration is particularly important at the sea floor at tectonic plate boundaries. https://en.wikipedia.org/wiki/Serpentinite https://en.wikipedia.org/wiki/Serpentinite
The article also mentioned that, although the valve has a capacity of 4,000CFS, "...sustained operation at the moment would be 2,000," said DWR spokesman Ted Thomas.""An Oroville Dam river valve system damaged in 2009 was repaired about two years ago, and their use wouldn't have made a dent in lake levels during this week's crisis, a Department of Water Resources spokesman said.
The valve system, one of three water release points for the dam, only has the capacity to move 4,000 cubic feet per second, according to a department power point presentation dated February 2015.
