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  1. Bleodswean

    Bleodswean New Member

    901.09 feet right now!!

    Articles in which the emergency spillway is mentioned as some sort of "choice" are frustrating. It seems as though this safety feature is going to be breached this morning.

    What about the ecological damage? The mud, rock, rebar, cement downstream.
  2. Mick West

    Mick West Administrator Staff Member

    It was a choice (and still is). They could easily have opened the gates more to put 100K cfs down the main spillway. But they have to weigh erosion at the top and hillside vs. erosion at the bottom. They ramped down the main spillway flow as the erosion was going to take out some power lines.
  3. Mick West

    Mick West Administrator Staff Member

  4. Mick West

    Mick West Administrator Staff Member


    Time for a live test of something that was built 40 years ago, and has never been used, and is holding back a mountain of water. The Army Corps of Engineers says it's good for a massive flood of 700K cfs. But there's a lot of unknowns.
  5. Bleodswean

    Bleodswean New Member

    Yes, of course. Insomuch as a safety feature is a "choice" after the preferred choice has been lost. You do think they could have easily allowed that amount of water down the main spillway? At some point this season they will be doing exactly that. It's going to be amazing to see the extent of the breakage of the spillway since the latest releases.
  6. Mick West

    Mick West Administrator Staff Member

    The main spillway isn't "lost". The top half is still working perfectly.

    Still, it wasn't exactly a choice to use the emergency spillway. They chose to gamble on the the inflow falling and the 65K outflow being maintained. They had to reduce to 55K, and the inflow decline leveled off a bit.

    Yeah, the next storm systems are going to be scarey. They will have to continue to draw down the level as much as possible with the main spillway - probably for weeks. They might stop it briefly for inspections once the emergency spillway stops running.

    Interesting times at Oroville and the Yuba area.
  7. Mick West

    Mick West Administrator Staff Member

    Live pic at 8:52AM, it's only just over the top. Minimal flow.
  8. Bleodswean

    Bleodswean New Member

    I appreciate you posting the KCRA footage. INSANE stuff, really. We are not getting that on a local level. I hope someone is out there with cameras.

    For those of us who hike the point regularly, it's concerning. Access to that trailhead....the emergency spillway catch basin will begin to spill over the road.
  9. Mick West

    Mick West Administrator Staff Member

    I think that road is likely going to be washed away. You've still got 90K cfs coming in, 55K going down the main spillway. That leaves 35K. That's still largely going towards raising the level of the lake, hence the minimal flow. But the higher the lake goes, the faster the overflow. I think it's going to ramp up very quickly and you'll start to see a torrent cutting up the hillside some time this morning.

    09:00 level is 901.24 feet. There's probably some weir-related math to calculate the CFS given the length of a weir and height of the water level above the weir.

    Note the weir also extends into the parking lot, all the way along to the hillside. Not clear what the slope up is though.
  10. rkt88edmo

    rkt88edmo New Member

    From the KCRA footage at around 0900hrs it looks like they reduced the regular spillway output. It doesn't look like the same flow as yesterday.
  11. Bleodswean

    Bleodswean New Member

    Does approaching velocity apply to this? Or is the damaged spillway going to be used to counter?
  12. SR1419

    SR1419 Senior Member

    As Dierdre pointed out, its a State dam...Feds have nothing to do with it.
    Last edited: Feb 11, 2017
  13. Mick West

    Mick West Administrator Staff Member

    They just reduced it from 65K to 55K cfs. Still that an extra 75,000 gallons per second that is now heading for the emergency spillway.

    (1 cubic foot = 7.5 gallons)
  14. Mick West

    Mick West Administrator Staff Member

    Approaching velocity of what? The water in the lake by the dam and spillway is essentially static. It's being filled up by rivers that are miles away.
  15. SR1419

    SR1419 Senior Member

    Last edited by a moderator: Feb 11, 2017
  16. Mick West

    Mick West Administrator Staff Member

    View from the top:
    Parking Lot Flooding-aw.

    The emergency spillway goes all the way along the edge of this parking lot. The lot itself is filling up via the drains that normally take rainwater to the lake. They are flowing backwards now.

    The edges of these puddles will give a good indication of the changes in the lake level.


    Source: https://www.youtube.com/watch?v=RpTSUHDM2JQ
  17. Here is an estimated rating curve for the spillway. It is only an estimate because I do not know if the elevation of the spillway along the parking lot has the same top elevation as the ogee crest spillway. I have used a weir coefficient (C, not to be confused with discharge coefficient Cd) of 3.0 as a compromise between that of an ogee crest (up to 3.8) and the parking lot (broad crest - roughly 2.0). The weir equation is Flow in cfs = C x length x (depth over spillway crest ^ 1.5). Length and depth are in feet. The horizontal scale is the height of the reservoir surface above the spillway crest.

    Oroville Spillway Rating.
  18. From the posting immediately prior to my posting of the estimated rating curve, it appears that the weir crest adjacent to the parking lot is slightly higher in elevation than the ogee weir crest. As such the estimated rating curve may overestimate flow slightly.
  19. Mick West

    Mick West Administrator Staff Member

    So does that mean if the net inflow is sustained at 35K cfs, then the level will rise to ~3 feet above the spillway?
  20. SR1419

    SR1419 Senior Member

    This might be useful. Oville.
  21. Spectrar Ghost

    Spectrar Ghost Senior Member

    I'm fascinated by this in spite of myself.

    I can't imagine being one of the CWA engineers right now, seeing all my work literally washing away in front of me, nor can I really envision the effort it will take to rebuild in between wet seasons.

    Despite all that it's such an awesome sight I just have to keep watching.
    • Agree Agree x 2
  22. Mick West

    Mick West Administrator Staff Member

  23. Weir coefficient and discharge coefficient are not the same. The weir coefficient is roughly equal to the discharge coefficient times the square root of 2g (two times gravitational force). Therefore the weir coefficient corresponding to a discharge coefficient of 0.62 (a high discharge coefficient for deep submergence that we will not see in this case) will be 0.62 x sqrt(2 x 32.2) or 4.9.
    • Informative Informative x 1
  24. jwchesnut

    jwchesnut New Member

    The empirical simplified formula for flow over a horizontal weir is Q (cfs) =3.33 * L * H^(1.5). (cite USBR).
    Q = cfs
    L = length in feet
    H = head over the weir
    where H/P <0.33 (P = depth of pool immediately behind the weir)
    It appears the Oroville weir has a vertical wall, so P is greater than H.

    L is conditioned on the upstream channel (usually cited as B). In the case of Oroville, there no restriction on the upstream channel.

    Current head is 0.38 feet, so current flow over the 900 foot segment of the overflow operating is about 720 CFS.
    The current imbalance is 24,000 cfs, so the lake elevation will build. (delta in the last hour was 0.15 feet).
    • Like Like x 1
    • Informative Informative x 1
  25. Mick West

    Mick West Administrator Staff Member

  26. Mick West

    Mick West Administrator Staff Member

  27. Spectrar Ghost

    Spectrar Ghost Senior Member

    The outflow's already carving channels...
  28. Mick West

    Mick West Administrator Staff Member

    Looks like it's using existing drainage under the road. The road is probably not long for this world though. It's just compacted fill, like the dam
  29. Spectrar Ghost

    Spectrar Ghost Senior Member

    I meant the two largely parallel channels downhill from the road, on the right. Probably only a foot deep right now.
  30. jwchesnut

    jwchesnut New Member

  31. Mick West

    Mick West Administrator Staff Member

    I think it's largely a natural ravine lower down.
  32. Spectrar Ghost

    Spectrar Ghost Senior Member

  33. Leifer

    Leifer Senior Member

    It seems they have accepted that the main spillway structure below the initial damage, is a total loss, and large water release will not impact the structural integrity of the main dam.

    According to the gentleman below (vid), there are 3 immediate concerns.
    1) Erosion up above the initial main spillway damage, where there is a power-line tower that could be threatened,which supplies grid power to the plant/dam (see #3).
    2) Debris build-up at the base of the damaged spillway, clogging the river, causing "backflow" into the dam's power-house....flooding it.
    3) Maintaining power "to" the plant, so that excess water releases can be controlled and maintained.

    Future concerns are:
    1) A wet forecast in the next 4-5 days. (or even more wet weather after that)
    2) Considerations of Spring snow-melt, as the snowpack is very high. (likely not enough time to repair the main spillway before that happens)

    [video since r emoved from youtube]
    Last edited by a moderator: Feb 19, 2017
  34. Graham2001

    Graham2001 Active Member

    I've been trying to find video footage of the overflow from the emergency spillway, but the first hits on YouTube turned out to be the following channels (I am quoting here from their about pages, which make their intent quite clear.)

    James Munder: TruEarther & Researcher


    Higher Truth Channel


    Quite simply the conspiracy peddlers and fear mongers have latched onto this major media event and are adding their own 'spin' to it so as to entertain the rubes and thanks to search engine optimisation they are drowning out the major news organizations.
  35. deirdre

    deirdre Moderator Staff Member

    i googled it, then chose videos. (past 24 hrs) and didnt see any conspiracy links.
    This guy on the ground had some interesting footage on his channel. here shows the water going over the road a bit earlier today.

    Source: https://www.youtube.com/watch?v=DVNaPBlIxe4
  36. Bleodswean

    Bleodswean New Member

    I have been slightly surprised by the lack of major news organizations covering this. Not even to mention the abysmal coverage by local news. (I'm local.) KCRA out of Sacramento has been doing a decent job, plus they have a bird or a plane which makes for video footage. Why doesn't someone send a drone up?

    The presser has been one of the more interesting updates thus far. Dismayed to hear that they are considering an alternative placement of the spillway. I really think that rec area is going to be closed for some time.

    There is so much engineering and math...and this forum has been the ONLY place I've found where the failure and responses are being discussed informationally.
    • Like Like x 1
  37. Chris Balfe

    Chris Balfe New Member

    In the video from DWR press conference, did you guys understand his answer to the question (at about 27:56 in the video) about why inflows minus primary spillway outflows would not equal outflows over the emergency spillway? He didn't really explain it well ("engineers get paid a lot of money to figure this out" does not demonstrate a deep grasp of the issue) and it seemed to contradict what folks on this board were saying. Thanks.

    [video added.. this version question is at 31:30]

    Source: https://www.youtube.com/watch?v=wF-0bPO1CGs
    Last edited by a moderator: Feb 11, 2017
  38. Leifer

    Leifer Senior Member

    Here's some HD drone footage of the spillway, yesterday (2/10)

    I agree....I haven't seen one mention of this in my local news, or National TV news coverage. Maybe I missed it ???

    Trump 'news' is trumping a lot of important local, national, and international news and events.
  39. Nrdymik

    Nrdymik New Member

    • Like Like x 1
  40. Leifer

    Leifer Senior Member

    It's like a wave effect....or that inflow 2 miles away will not immediately affect the outflow....it takes some time for the inflow to reach the outflow, miles away.
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