Oroville Dam Spillway Failure

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From an update by County Supervisor William Connelly:

https://m.facebook.com/story.php?story_fbid=1683579861668957&id=100000508772678

Relevant excerpt:
"
o removal taking place in multiple locations from land to build what DWR is
referring to as the “low flow channel” to get water around the large debris piles at the
bottom of the primary spillway.
o Elevation of water at the Hyatt power plant has been lowering so that water is not going
into the plant – once the “low flow channel” is in, that level will continue to decrease.
 Construction and repairs continue on the emergency/auxiliary spillway. The weather is not
stopping the progress, though it may be slowed down periodically.
 No further erosion has been seen on or near the primary spillway. It is being monitored and
evaluated 24/7.
 PG&E continues to relocate lines below the spillway. Anticipate being completed by Tuesday.
 Lake elevation at 9 AM was 852.30 feet. Only two feet from the 850 goal.
 Current inflow approximately 45,000 cfs. DWR anticipates it will peak on Tuesday morning at flows
that could exceed over 100,000 cfs. The average inflow over the next several days could be around
68,000 on Monday and Tuesday. Outflows are expected to stay at 55,000, but could be adjusted
upwards as necessary. DWR is extremely confident that the lake can easily hold the expected
precipitation through the Tuesday storms. The lake may get above the 850 level, but they expect
nothing even resembling a problem...
Content from External Source
"


Looks like the heavy equiptment work we were seeing on the banks of the pool in earlier photos may have been in preparation for this new "low flow channel"

Also looks like they are ramping up outflow to 60,000cfs, per the Butte County Sheriff's office:
https://m.facebook.com/story.php?story_fbid=785455638271383&substory_index=0&id=119221578228129
 
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The reason this could be a problem here is if hydrothermal fluids flowed parallel to the layers causing entire layers to be altered in a way that makes them much more susceptible to erosion.

OROVILLE MAP 20170215_MOD_moderntopo.jpg

The above topo has been given a rectangular overlay. This overlay crosses the main spillway in the area of spillway failure. The lower portion of the overlay appears to map the erosion channel cut by the water flow from the area of spillway failure.

If you follow the overlay up to the northwest edge of the parking lot, it can be seen the overlay traces over a series of inverted "V's" in the contour lines. This contour shape indicates the presence of a channel in the terrain at that point.

It is understood that any water running off a slope will exploit the natural weakness of that slope. The water will preferentially erode weak overburden and will follow a path of least resistance including existing topographical features.

This diagram suggests the possibility that there exists a geologic feature [ I lack knowledge of the appropriate term] which runs diagonally across the site in the area of the imposed overlay. This geologic feature was exploited to form the erosion channel south of the spillway failure (the rock to the immediate west of this portion of the overlay appears sound as it has resisted a prolonged period of water flowing at 155 feet per second at a volume of 100,000 cfs).

I am not a geologist and want to be careful drawing conclusions. To my amateur mk 1 eyeball the above diagram and overlay suggests the existence of a possible area of geologic weakness running across the site. If this geologic feature is confirmed, then it suggests the possibility of an erosion path leading downhill from the NW corner of the boat ramp parking lot.
 
With regards to hydro-thermal venting and rock color, is there any significance to the colors, rock whisperer? I mean, are the mineral deposits from such venting always 'orange' like weathered rock (at least in these formations in Oroville)?
Nothing is black and white in geology. But I will speculate on a generalization of the rocks here. In the original blowout, blue to gray is the sheeted dikes, the deep red color in the hole is a basalt screen however altered, weathered, and or metamorphosed. Yellows and whites are indicative of extreme alteration due to hydrothermal processes. Up near the weir, the bright reds near the surface is the soil derived from highly weathered bedrock. Orange hues could be basalt screens or alteration. The only way to truly identify these rocks is to take pieces of them back to the lab and thin-section them for viewing under a cross polarizing light microscope. I've never stepped foot on the Smartville block, so everything I say is simply an educated guess.
 
OROVILLE MAP 20170215_MOD_moderntopo.jpg

The above topo has been given a rectangular overlay. This overlay crosses the main spillway in the area of spillway failure. The lower portion of the overlay appears to map the erosion channel cut by the water flow from the area of spillway failure.

If you follow the overlay up to the northwest edge of the parking lot, it can be seen the overlay traces over a series of inverted "V's" in the contour lines. This contour shape indicates the presence of a channel in the terrain at that point.

It is understood that any water running off a slope will exploit the natural weakness of that slope. The water will preferentially erode weak overburden and will follow a path of least resistance including existing topographical features.

This diagram suggests the possibility that there exists a geologic feature [ I lack knowledge of the appropriate term] which runs diagonally across the site in the area of the imposed overlay. This geologic feature was exploited to form the erosion channel south of the spillway failure (the rock to the immediate west of this portion of the overlay appears sound as it has resisted a prolonged period of water flowing at 155 feet per second at a volume of 100,000 cfs).

I am not a geologist and want to be careful drawing conclusions. To my amateur mk 1 eyeball the above diagram and overlay suggests the existence of a possible area of geologic weakness running across the site. If this geologic feature is confirmed, then it suggests the possibility of an erosion path leading downhill from the NW corner of the boat ramp parking lot.
That is an extremely interesting hypothesis. Reason being, on the evening of the evacuations, I was right above the dam, on the south-east ridge, looking at the spill with a telescope. I was able to see that the fastest amount of water flowing (besides the water pouring into the main spillway) was down the sloping parking lot near the driveway - and it was moving like a river, compared to all the water moving over the spillway. (I had early though that we were watching water pouring down the driveway that leads to the parking lot. But pictures now confirm it was a bit before the driveway.)
 
The LA times published this a few days ago:
http://www.latimes.com/local/lanow/la-me-oroville-dam-cause-spillway-20170216-story.html

A summary of the incident, prepared by state water officials four days after the crater in the concrete chute appeared, said water from heavy rains hit the hillsides where the massive concrete spillway runs.

Flowing water during heavy rains was “diverted ... effectively eroding and undermining the spillway, causing a section to collapse,” said the incident summary.
Content from External Source
Report (Feb 15) attached, but seems not to match that exactly:

A spillway located at the Oroville Dam was compromised
during heavy rains. Flowing water was diverted toward the
adjoining hillsides, effectively eroding and undermining
the spillway causing a section to collapse. At
0738(02/11/17) water crested over the auxiliary spillway
and began to flow causing minimal erosion to the hillside
as expected.
Content from External Source
Notice it does not say that heavy rains were diverted, it says flowing water. The sequence of events suggested in the report is not clear. Is the LA times reading too much into it? Has DWR said anything similar elsewhere?

The short answers to your questions are (1) yes, they misread what was in the incident report (although, as you point out, it is not wholly clear) and (2) no, DWR has not said anything similar to the news report or indeed that clarifies what the incident report means - but obviously they are busy coping with other things.

I recall reading both the article and the incident report at the time they came out. My conclusion after reviewing the exact terms of the incident report was that it was referring to the breach in the spillway diverting water on to the adjoining ground. (Note that if you read the relevant paragraph of that report in full it also describes the erosion at the emergency spillway as "minimal" and attempts to deal with at least four other elements of a clearly complex situation within the space of a box on a form.)

At that time I hunted around for something else from DWR on this subject but there is nothing that even suggests that the collapse of the spillway was triggered by heavy rainfall eroding the affected section. In any event I can't see how DWR could have reached such a conclusion at this stage without the ability to perform a comprehensive investigation of the damaged part of the spillway while it is in use and sustaining further damage. Note that the news report does not suggest that the LA Times asked for and got confirmation of their understanding of the incident report; they appear just to have gone to print with it.

Frankly, this illustrates why concerned and interested persons have come to this site for information as opposed to ferreting around in the online mass media. Things that are simply published in an unfiltered/unverified form are potentially misleading. They certainly deserve to be debunked.
 
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I recall reading both the article and the incident report at the time they came out. My conclusion after reviewing the exact terms of the incident report was that it was referring to the breach in the spillway diverting water on to the adjoining ground. (Note that if you read the relevant paragraph of that report in full it also describes the erosion at the emergency spillway as "minimal" and attempts to deal with at least four other elements of a clearly complex situation within the space of a box on a form.)

I guess the question then would be: why mention "heavy rains"? Do they just mean "heavy rains, which had filled up the lake, so we were running the spillway"?
 
I guess the question then would be: why mention "heavy rains"? Do they just mean "heavy rains, which had filled up the lake, so we were running the spillway"?

Possibly. This is just speculation based on my observations, but I believe they may have noticed an issue with the spillway prior to the release on the 7th. They closed Oroville Dam Blvd East at 8:54 AM February 7th, hours before any reported issues with the spillway. https://www.buttecounty.net/publicworks/roadclosures.aspx This was the first time they've closed this road while releasing water from the spillway, I drive it daily and found it odd it was closed that morning. Again, just my observed speculation, so delete if this doesn't follow the rules.
 
I guess the question then would be: why mention "heavy rains"? Do they just mean "heavy rains, which had filled up the lake, so we were running the spillway"?

I wondered about that too and also whether what they said was cobbled together under pressure to submit the required paperwork. It's possible that's what they really meant and if so it's unfortunate their wording suggested something more. But it's unfair to use something like an incident report submitted in extremely trying circumstances as headline fodder.

P.S. If you look at box 9 on page 1 of the incident report (actual title "Incident Status Summary") it gives the subject as "Oroville Dam compromised spillway" and states as the cause "Unknown."
 
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News article quoting a disaster expert, commenting after the incident.
http://www.govtech.com/em/disaster/...o-about-risks-of-Oroville-Dams-spillways.html
The cratering of the main spillway — which spiraled into the current crisis in Butte County — occurred in a spot where cracks and other defects had been found repeatedly since 2009, said Robert Bea, a professor emeritus and engineering expert at UC Berkeley.
Content from External Source
Bea said inspectors noticed trees growing on the right side of the spillway in their 2015 report. The inspectors recommended removing the trees, but the damage may have already occurred.

“Those trees are there because they like water, and the question is, where are they getting the water from?” Bea said. “The answer is that we’ve got seepage in that spillway.”
Content from External Source
 
This is soo interesting! Because I took a pic in the sluice of the spillway only a couple of months ago - and the 2 walls abutting each side of the spillway sluice in your pics are now completely gone. What caused their demise? The disintegration of weathered rock they were abutting, I suppose?

Here's my pic, taken in December if I remember right...
Spillway.JPG

Just one of many plans - shows the existing grade at 900' ...




Before construction of weir - above Ronnies head .... Soil level at appx 900' next to structure (922 at top)...





Finished ground level reservoir side of emergency weir same height as the top of the approach wall - appx 875 ...


 
*Smacks face* I see them now, thanks. From the floor of the sluice, the walls blended into the main walls. My bad.
i know angles always mess me up too.. spend a year of two on Metabunk and you'd be amazed what funky stuff cameras (angles, zooms etc) do to views :)
 
I spoke earlier with City Admin of Biggs, Mark Sorensen, who has attended all of the DWR breifings. He said that William Connelly's update is quoting the DWR press release that is given to local officials about the work the DWR is doing, but Mr. Connelly himself has not actually been at the breifings. Mr. Connelly is not misquoting, but at the in person breifings the DWR representatives have made it more clear with maps and clarification that the "low flow channel" is how they (DWR employees, etc) refer to the section of the pool that currently has low flow due to debris build up. The section of the pool between the dam and spillway is termed the "low flow channel." They are removing debris from it, but it does not sound like they are creating any new channels at they his time.

From an update by County Supervisor William Connelly:

https://m.facebook.com/story.php?story_fbid=1683579861668957&id=100000508772678

Relevant excerpt:
"
o removal taking place in multiple locations from land to build what DWR is
referring to as the “low flow channel” to get water around the large debris piles at the
bottom of the primary spillway.
o Elevation of water at the Hyatt power plant has been lowering so that water is not going
into the plant – once the “low flow channel” is in, that level will continue to decrease.
 Construction and repairs continue on the emergency/auxiliary spillway. The weather is not
stopping the progress, though it may be slowed down periodically.
 No further erosion has been seen on or near the primary spillway. It is being monitored and
evaluated 24/7.
 PG&E continues to relocate lines below the spillway. Anticipate being completed by Tuesday.
 Lake elevation at 9 AM was 852.30 feet. Only two feet from the 850 goal.
 Current inflow approximately 45,000 cfs. DWR anticipates it will peak on Tuesday morning at flows
that could exceed over 100,000 cfs. The average inflow over the next several days could be around
68,000 on Monday and Tuesday. Outflows are expected to stay at 55,000, but could be adjusted
upwards as necessary. DWR is extremely confident that the lake can easily hold the expected
precipitation through the Tuesday storms. The lake may get above the 850 level, but they expect
nothing even resembling a problem...
Content from External Source
"


Looks like the heavy equiptment work we were seeing on the banks of the pool in earlier photos may have been in preparation for this new "low flow channel"

Also looks like they are ramping up outflow to 60,000cfs, per the Butte County Sheriff's office:
https://m.facebook.com/story.php?story_fbid=785455638271383&substory_index=0&id=119221578228129
 
Bea said inspectors noticed trees growing on the right side of the spillway in their 2015 report. The inspectors recommended removing the trees, but the damage may have already occurred.

“Those trees are there because they like water, and the question is, where are they getting the water from?” Bea said. “The answer is that we’ve got seepage in that spillway.”

There are posts with pictures in the thread

Pre-Failure Oroville Dam Spillway Historical Images
 
I extracted some images from the DWR drone footage Saturday 2/18/2017

Source: https://www.youtube.com/watch?v=yxgtyOfwrj8


From which I made this panorama:


You can see the bags of rocks are all placed in front of the parking lot. I think this is because there's a lot of flat solid ground in front of that weir, and the bags are largely there to protect the road. Notice no bags where there is no road.

20170219-230740-zj19v.jpg
 
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News article quoting a disaster expert, commenting after the incident.
http://www.govtech.com/em/disaster/...o-about-risks-of-Oroville-Dams-spillways.html
The cratering of the main spillway — which spiraled into the current crisis in Butte County — occurred in a spot where cracks and other defects had been found repeatedly since 2009, said Robert Bea, a professor emeritus and engineering expert at UC Berkeley.
Content from External Source
Bea said inspectors noticed trees growing on the right side of the spillway in their 2015 report. The inspectors recommended removing the trees, but the damage may have already occurred.

“Those trees are there because they like water, and the question is, where are they getting the water from?” Bea said. “The answer is that we’ve got seepage in that spillway.”
Content from External Source

I don't agree with the Bea comment that implies that the trees are there because they are getting water from the spillway. There are trees all over that hillside. I have been going to Lake Oroville and across that spillway for 25 years. In many low water years the spillway is never wet. In the years the spillway is used, trees get plenty of water from rain. The spillway would not be a reliable source for trees to get water. I expect the inspectors recommended removing the trees because their roots could undermine the spill way just as they do sidewalks and driveways.
 
DWR has just released a series of videos showing both the damaged flood control spillway and the erosion below the emergency spillway. They are in reverse chronological order. In #7 & 8 you can see the erosion progression that likely led to the evacuation.


Source: https://www.youtube.com/watch?v=yxgtyOfwrj8&index=1&list=PLeod6x87Tu6eVFnSyEtQeOVbxvSWywPlx


The second video at 0:47 shows a spillway drain on Feb 17. The water looks slightly muddy, suggesting possible erosion under the remaining upper spillway. Also possible those workers seen to the right in video disturbed the soil; the 17th was rainy.
Screencap:
Screenshot 2017-02-20 at 1.21.12 AM.png
Youtube link at 0:47, drain shown for ~5 seconds.

Source: https://youtu.be/IRyj0T9Rm4A?list=PLeod6x87Tu6eVFnSyEtQeOVbxvSWywPlx&t=47
 
DWR has just released a series of videos showing both the damaged flood control spillway and the erosion below the emergency spillway. They are in reverse chronological order. In #7 & 8 you can see the erosion progression that likely led to the evacuation.


Source: https://www.youtube.com/watch?v=yxgtyOfwrj8&index=1&list=PLeod6x87Tu6eVFnSyEtQeOVbxvSWywPlx


Does anyone recognise what those huge, almost rectangular slabs in the river are, in the opening shot of the last video? Still no possibility to annotate a picture, but they´re in the river itself, at the junction with the end of the spillway. Would they be bedrock, exposed by the erosion?
 
Does anyone recognise what those huge, almost rectangular slabs in the river are, in the opening shot of the last video? Still no possibility to annotate a picture, but they´re in the river itself, at the junction with the end of the spillway. Would they be bedrock, exposed by the erosion?

If you are speaking of the rectangular slabs shown in the image below,
they are "Debris Islands" composed of rock that has been eroded by the force of the spillway jet. They are blue grey which is the color of the rock believed to be least easily eroded. The more easily eroded rock is colored reddish orange. If you look at some of the other videos in the series they show images taken further downstream. The waterways downstream to the Thermolito dam are all colored reddish orange.

I suspect the reddish orange rock is a lighter rock and is more easily transported by water. It likely also grinds up into fines which are more easily transported. The hard blue grey rock breaks up into larger pieces, these pieces are heavier, they are not easily transported and so they collect in the river bed.

At present they are blocking the discharge from the power station. Crews have been moving construction equipment into the area with the intent of removing these debris islands in order to restart flow through the power station.

EDIT
They are found at the end of the 1/9 video rather than at the start.

DEBRIS ISLANDS 20-02-2017 5-46-24 AM.jpg
 
c
If you are speaking of the rectangular slabs shown in the image below,
they are "Debris Islands" composed of rock that has been eroded by the force of the spillway jet. They are blue grey which is the color of the rock believed to be least easily eroded. The more easily eroded rock is colored reddish orange. If you look at some of the other videos in the series they show images taken further downstream. The waterways downstream to the Thermolito dam are all colored reddish orange.

I suspect the reddish orange rock is a lighter rock and is more easily transported by water. It likely also grinds up into fines which are more easily transported. The hard blue grey rock breaks up into larger pieces, these pieces are heavier, they are not easily transported and so they collect in the river bed.

At present they are blocking the discharge from the power station. Crews have been moving construction equipment into the area with the intent of removing these debris islands in order to restart flow through the power station.

EDIT
They are found at the end of the 1/9 video rather than at the start.

DEBRIS ISLANDS 20-02-2017 5-46-24 AM.jpg


Thanks, yes those are what I meant.

And that explains the activity visible at the southern bank.
 
Has anyone calculated what would happen if the current rainfall levels increase by 50 or 100%. California periodically gets Megafloods:
-https://www.scientificamerican.com/article/atmospheric-rivers-california-megaflood-lessons-from-forgotten-catastrophe/.

Would the emergency spillway washout? Could the flow in the damaged main spillway handle more (double or more) outflow then it has ever had to in the past?

If this is the predicted 200 year megaflood, then all of California could be tested.
 
Has anyone calculated what would happen if the current rainfall levels increase by 50 or 100%. California periodically gets Megafloods:
-https://www.scientificamerican.com/article/atmospheric-rivers-california-megaflood-lessons-from-forgotten-catastrophe/.

Would the emergency spillway washout? Could the flow in the damaged main spillway handle more (double or more) outflow then it has ever had to in the past?

If this is the predicted 200 year megaflood, then all of California could be tested.
Good question! Was wondering this myself...
 
If you are speaking of the rectangular slabs shown in the image below,
they are "Debris Islands" composed of rock that has been eroded by the force of the spillway jet.

DEBRIS ISLANDS 20-02-2017 5-46-24 AM.jpg

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 :)
 
Has anyone calculated what would happen if the current rainfall levels increase by 50 or 100%. California periodically gets Megafloods:
-https://www.scientificamerican.com/article/atmospheric-rivers-california-megaflood-lessons-from-forgotten-catastrophe/.

Would the emergency spillway washout? Could the flow in the damaged main spillway handle more (double or more) outflow then it has ever had to in the past?

If this is the predicted 200 year megaflood, then all of California could be tested.

Given that we don't really know what the state of either spillway is without more inspect, there's no way of knowing. More rain would be more damage. But in a mega flood event you are either going to get massive flooding or quicker massive flooding. The water's coming down the hill one way or another.

And it's not a "predicted" 200 year megaflood. They don't happen on schedule.
 
Here's my pic, taken in December if I remember right...
Spillway.JPG

I have a question regarding the boom shown in this photo and the debris pictured elsewhere around the main spillway gates lakeside. This boom is clearly now broken and can be seen lying on opposing sides of the lake. It is presumably intended to keep floating debris away from the main spillway.

Has anyone seen any effort to a) repair or replace this boom b) clear any of the floating or now beached debris that would seem to threaten the main spillway and gates? Would it not make sense to remove any further threats to the main spillway eg this debris? Should the water rise again, the debris which is currently beached will refloat and present another threat. Also, any more which arrives, will not be prevented approaching the spillway by a broken boom. How difficult would it be to replace the boom, even with the current flowing towards the spillway at 60kcfs? Could a replacement be dropped in place by a helicopter? Why has this preventative equipment not been replaced?
 
Has anyone seen any effort to a) repair or replace this boom b) clear any of the floating or now beached debris that would seem to threaten the main spillway and gates?

Any activities directly in front of or near the flood control structure would be ill advised with the gates open.

While the floating boom provides some restraint of debris, its real purpose is to keep boaters and others out of the danger area where currents could pull them into the FCS.
 
Any activities directly in front of or near the flood control structure would be ill advised with the gates open.

While the floating boom provides some restraint of debris, its real purpose is to keep boaters and others out of the danger area where currents could pull them into the FCS.
Thank you.
In normal times, presumably there is a maintenance schedule and established methodology to remove debris not caught by the boom? I understand these are abnormal times for Oroville Dam, and such schedules may have been abandoned, but I am concerned that an already compromised spillway and gates may be further damaged by not removing at least the debris which is now safely and easily accessible on land.
 
News article quoting a disaster expert, commenting after the incident.
http://www.govtech.com/em/disaster/...o-about-risks-of-Oroville-Dams-spillways.html
The cratering of the main spillway — which spiraled into the current crisis in Butte County — occurred in a spot where cracks and other defects had been found repeatedly since 2009, said Robert Bea, a professor emeritus and engineering expert at UC Berkeley.
Content from External Source
Bea said inspectors noticed trees growing on the right side of the spillway in their 2015 report. The inspectors recommended removing the trees, but the damage may have already occurred.

“Those trees are there because they like water, and the question is, where are they getting the water from?” Bea said. “The answer is that we’ve got seepage in that spillway.”
Content from External Source

Bunkum? Maybe just conclusory and based on limited information. If you read the whole of the article reporting Prof. Bea's views three things stand out:

1. The background material provided to him consisted of about 10 years' inspection reports/maintenance recommendations. No construction records or any that related to the actual composition of the subsurface at the collapse site. Note that the side walls of the spillway were designed to extend much further below the surface of adjoining ground than the wall structure visible above it. They were intended to enclose the subsurface. Tree roots growing from higher ground might well penetrate below the buried portion of the side wall but there's nothing to suggest that they caused any heave of the concrete surface or could have created a vast void under the surface to the extent seen when the spillway flow was interrupted week before last.

2. Another external adviser is quoted in the article, a specialist in dam maintenance. His conclusion was that he saw no evidence of "gross" negligence in the maintenance. Perhaps he chose his words carefully.

3. Neither really commented on the record of substantial flows over the spillway, which over its life appear to have been intermittent. Nor did they refer to the possible effect of prolonged drought on the surrounding and underlying surface. At about the same time as the article was published there was another (which I can't track down but is referenced far back in this thread) referring to drought and the inevitable weathering of the concrete as possible explanations for its failure.

It strikes me that it's all guesswork at this point.
 
Thank you.
In normal times, presumably there is a maintenance schedule and established methodology to remove debris not caught by the boom? I understand these are abnormal times for Oroville Dam, and such schedules may have been abandoned, but I am concerned that an already compromised spillway and gates may be further damaged by not removing at least the debris which is now safely and easily accessible on land.

Correct, there are regular crews with tow boats and small barges that routinely patrol the lake especially during times of significant inflow and rising water. They use long beams or logs chained together to sweep floating debris then tow the debris into selected coves where they can be carried away when the water lever drops later in the year. They also anchor log booms across the upper reaches of the various channels to catch floating debris coming down. (The edge of those log booms can be an excellent place to fish for bass by the way). It is my understanding that those crews and boats are currently working in the Diversion pool to capture floating debris being washed in and keeping it away from the Diversion dam.
 
(My first post - please be gentle)

This diagram suggests the possibility that there exists a geologic feature [ I lack knowledge of the appropriate term] which runs diagonally across the site in the area of the imposed overlay.
That geologic feature can be seen in this picture. I've drawn an oval where the V-shape from the USGS map can be clearly seen as a ravine. orovilleV.jpg
 
(My first post - please be gentle)


That geologic feature can be seen in this picture. I've drawn an oval where the V-shape from the USGS map can be clearly seen as a ravine. orovilleV.jpg

Ravines are not exactly geologic features (in the sense of reflecting the type of rock) though are they? They are a function largely of topology from the initial formation of the hillside via uplifting, glacial carving or deposition, or volcanic activity. That's then compounded by the amplifications of essentially random initial rivulets and notches. You'd get ravines even if the hillside were entirely homogeneous (all made of the same stuff).
 
and the debris pictured elsewhere around the main spillway gates lakeside.
debris seen where? please provide a photo. In my photo, feb 18th, the right side is clear. and its very possible what we see on the left there was actually moved UP the bank.. we would need a pic from teh otehr side of spillway to see what the debris actually looks like near the gates.
ee.JPG

but yes, in one of the press conferences the DWR guy said they had boats out in the lake grabbing logs and what not.
 
debris seen where? please provide a photo.

I believe this is reference to this debris field shown caught against the FCS gate works
[GALLERY=media, 72]FL_Oroville-2590_02_14_2017 (1) by AlmostaCE posted Feb 20, 2017 at 12:18 PM[/GALLERY]
http://pixel-ca-dwr.photoshelter.co...00NtLpqQZaW.4/FL-Oroville-2590-02-14-2017-jpg

I expect some of this is shown in the photo directly above as "landed" on the bank above the SE intake wall, much has likely been sucked through the FCS as the water level gets closer to the top of the opening.
 
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