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  1. Eric Barnes

    Eric Barnes New Member

    Thanks for the interesting posts/commentary Mick! Came here from Dr. Roy Spencer's site. It will be interesting to follow events in the next few weeks/months.
     
  2. Mick West

    Mick West Administrator Staff Member

    Based on:
    upload_2017-2-12_15-3-59.

    The CDEC lake level figures have 1AM with 902.58 and 11AM at 902.30. I'm going to assume they are just using a simple equation

    Flow = K * (h-D)^1.5

    The -D is the height of the spillway, you'd expect 901, however, solving:
    12600=K*(902.58-D)^1.5, 8000=K*(902.30-D)^1.5 for K and D

    Gives K=11357.8, D=901.508

    So based only on those two data points it looks like they are using

    Flow = 11357.8*(height - 901.508)^1.5

    However it's entirely possible they are using a more complex formula to account for the variations in the lip height and shape
     
    • Like Like x 1
  3. It is a little more complex. The crest of the ogee section is at elevation 901.0 and the crest of the parking lot spillway section (a short wall) appears to be about one foot higher. Further clouding the calculation is the fact that the weir coefficient of the parking lot spillway section is very different than that of the ogee section. These differences (two more unknowns) make it impossible to back into a reliable equation. Going forward from established weir flow knowledge, two weir equations can be superimposed to estimate the stage discharge relationship but other ambiguities (at lease to me) still limit the result to an estimate.
     
  4. Mick West

    Mick West Administrator Staff Member

    Well I assume they have better measurements than we do. That equation fits the two data points, and the curve would be similar (^1.5) so it's probably a reasonable estimate for <2 feet. Hopefully it will never get higher!
     
    • Agree Agree x 1
  5. Also subtracting the controlled spillway and powerhouse releases from the downstream river flow may not be a very good estimate of emergency spillway flow. Before the emergency spillway was in operation I noticed that the estimate of downstream river flow was consistently exceeding the sum of the controlled spillway release and the powerhouse release. Sediment in the bottom of the river channel from the controlled spillway failure may cause this inconsistency by causing the water in the river to be higher than normal for the actual flow.
     
  6. Carl Leoanrd

    Carl Leoanrd New Member

    There is an emergency evacuation order for low lying areas from Oroville and down stream. There is undermining of the emergency spillway.

    This is from the Sacramento TV stations.
     
  7. dafogle

    dafogle New Member

    https://www.facebook.com/bcsonews/posts/781255845358029
     
    Last edited by a moderator: Feb 12, 2017
  8. Mick West

    Mick West Administrator Staff Member

    http://www.sacbee.com/news/state/california/water-and-drought/article132332499.html
     
  9. Mick West

    Mick West Administrator Staff Member

    This is the worst case I wrote about in the OP.

    Not the same as the dam failing, however it's very bad. 30 feet rapid release will create major flooding if it happens.
     
  10. Yes. Failure of the emergency spillway would be very bad. If the ogee spillway is lost, flow through the breach may be in the multiple hundreds of thousands of cubic feet per second. Outflow may reach 100,000 cfs per 100 feet of lost spillway.
     
    Last edited: Feb 12, 2017
  11. Graham2001

    Graham2001 Active Member

    Just checked the 'latest' videos and the scare-mongers are out in force, King Truth LoganLLC ran a video with a close up of the emergency spillway and the following title "OROVILLE DAM WASHOUT !!! BETTER EVAC NOW". I have also seen one video which I will not link to which uses footage from a flood either in China or a nearby region and claims this is happening in California.


    Source: https://www.youtube.com/watch?v=pK9emHspzZ4


    On the other hand here is a more recent and less alarmist video of the overflow, though some of the commenters seem to be claiming that 'the government' is censoring YouTube videos on this event.


    Source: https://www.youtube.com/watch?v=UFpDJ_NsEDo
     
  12. Mick West

    Mick West Administrator Staff Member

    A failure of the spillway will be a significant disaster in itself. It would then raise the spectre of an possible failure of the dam itself which would be ten times worse. My "why the dam will not collapse" diagram says it won't because of the rock ridge. But the geology can't be 100% relied upon. It's not something anyone is going to rule out.

    Downstream areas are already saturated with high rivers and some local flooding. And that's with actually reduced flows.
    There's a range of possible outcomes here. None of them are good, some of them are disastrous.
     
    • Agree Agree x 2
  13. deirdre

    deirdre Moderator Staff Member

    its not really scare mongering if it's really happening.
     
  14. deirdre

    deirdre Moderator Staff Member

    did they at least open the main spillway full force once it was running clear?
     
  15. Mick West

    Mick West Administrator Staff Member

    Said they put it to 100K
     
  16. rkt88edmo

    rkt88edmo New Member

    DWR Tweets E-spillway failure before 6pm (tweet from around 1640hrs)


    flood snip.JPG
     
  17. Mick West

    Mick West Administrator Staff Member

    • Informative Informative x 1
  18. rkt88edmo

    rkt88edmo New Member

    So, there is the very strong horizontal line below the e-spillway, is that really the base of the non-earthen spillway lip, or do we know how tall/deep the concrete portion of the e-spillway is?
     
  19. Carl Leoanrd

    Carl Leoanrd New Member

    They are talking the top 30 of the lake being drained, so I'm guessing that it is 30 ft.

    I'm just estimating as I'm only on my phone, but the top 30 feet of the lake has about 350k acre feet. That is a disaster on a huge scale.
     
  20. Spectrar Ghost

    Spectrar Ghost Senior Member

    Is there a possibility that a failure will cause upstream flow and damage the base of the dam proper?
     
  21. Max Fefer

    Max Fefer New Member

    Top 30ft of the reservoir is roughly 350-400k acre feet. Back of the envelope calculation shows that if it takes 1 day to drain that 350k, this would increase downstream flows by 200 kcfs (above current levels). From what I heard, downstream levees around Marysville are designed for 150k cfs. I think it unlikely to have a large effect on Sacramento given the current information, but these situations can evolve quickly.

    The dam is unlikely to fail due to the hard rock ridge separating the spillways and the dam. If the normal spillway fails, this could cause a more catastrophic failure of the emergency spillway.

    This isn't a tried and true analysis, so please comment if any readers see inaccuracies.
     
  22. Mick West

    Mick West Administrator Staff Member

    I'd not rule it out. There's quite a bit of elevation up the road to the power station, but the level would certainly rise.
    20170212-180304-vbzit.
     
  23. Mick West

    Mick West Administrator Staff Member

    What's the 350K figure? If the emergency spillway holds they will drain it with the broken main spillway at 100 to 150K.

    If the emergency spillways fails then they would probably shut off the main spillway. The failed emergency spillway flow could be anything of a huge range of numbers.
     
  24. Mick West

    Mick West Administrator Staff Member

  25. Mick West

    Mick West Administrator Staff Member

    Plan is now to use helicopters to drop bags of rocks into a hole that is forming near the emergency spillway.

    Hole was eroding up the hill towards the weir, but advance has slowed.

    2" of water going over the emergency spillway. Dropping
     
  26. Mick West

    Mick West Administrator Staff Member

    They sound relatively hopeful.
     
  27. RedNeckGeek

    RedNeckGeek New Member

    Apparently there was "boil" on the auxiliary spillway at around 3PM today that is now rapidly eroding back into the hillside. In order to slow the flow into the auxiliary spillway, flow through the main spillway was increased to 100K CFS. However, it was decided to issue an evacuation notice for all people south and west of the dam in the Feather River drainage. That includes low lying areas of not only Oroville, but several communities south along Highway 70 and the Feather River. It was just announced that an Oroville city councilman had been told that the rate of erosion is not as high as originally thought, but the evacuation orders are still in effect.
     
    • Informative Informative x 1
  28. jwchesnut

    jwchesnut New Member

    New conference reports head cutting has slowed. Spillway has been raised to 100K cfs. Lake level may drop quickly enough to dry out the emergency spillway.
     
    • Like Like x 1
  29. RedNeckGeek

    RedNeckGeek New Member

    DWR personnel are said to expect that the auxiliary spillway will stop flowing within one hour.

    Estimates are that 500,000 cubic feet of water would be released from the reservoir if the auxiliary spillway fails.

    Traffic is jammed northbound on Highway 70 north out of Oroville, but several evacuation centers are open in Chico.

    There will be another news conference at 9PM Pacific Time.
     
  30. Graham2001

    Graham2001 Active Member

    Meanwhile the scare-mongering channels on YouTube are continuing to spread as much fear as is needed to generate the hits.

    This is part of the write up for a video posted on YouTube channel NewsChannel428 which seems to specialise in alarmist material of all kinds. It makes the channels intent pretty clear.




    Source: https://www.youtube.com/watch?v=pke15jmjYP4
     
  31. Mick West

    Mick West Administrator Staff Member

    • Informative Informative x 1
  32. Mick West

    Mick West Administrator Staff Member

    Oroville emptying out earlier:
    20170212-185513-l9ww0.
     
  33. Eric Barnes

    Eric Barnes New Member

    The weir must be getting undercut? It looks like much more water is going over the top than earlier this AM, but the actual water level is lower now?
     
  34. Mick West

    Mick West Administrator Staff Member

    There was a similar helicopter operation in New Orleans with the flooding there. However they used sand bags, as the water was not moving much. Oroville will likely have to be large rocks. Interesting and unorthodox engineering coming up.

    ivE9u.So.91.
     
  35. Mick West

    Mick West Administrator Staff Member

    They say it's down to a couple of inches. Should stop within a few hours.
     
  36. RedNeckGeek

    RedNeckGeek New Member

    I thought I heard during the news conference that the boil was at the bottom of the hill near the river.
     
    • Agree Agree x 2
  37. Mick West

    Mick West Administrator Staff Member

    Well that's not going to make the weir collapse. It must be near the top.
     
    • Agree Agree x 1
  38. dafogle

    dafogle New Member

    so they will be dropping large rocks into that boil/hole ??
     
  39. Leifer

    Leifer Senior Member

    True....searching YT for "Oroville dam"......the mass of individuals creating alarmist videos is amazing (or is it ?). It looks like they are competing for "hits" by creating extreme YT video titles....adding to more and more incorrect inflated information....and basically turning into clickbait. This might be a sign of how many people get their news from YT.
    I gave-up youtube for any current helpful information on this topic, and I'm watching the KCRA live news feed.

    http://www.kcra.com/nowcast
    click on "Live Now" icon at the top if you don't see a live feed.

    Hard to find with a simple YT search, there is Cal EOS live feed on youtube, but other than press conferences, there's not much info to be found there.

    Source: https://www.youtube.com/watch?v=CJVG0z1g6Eo
     
    Last edited: Feb 12, 2017
    • Informative Informative x 1
  40. Mick West

    Mick West Administrator Staff Member