Thread Status:
Not open for further replies.
  1. Mick West

    Mick West Administrator Staff Member

    Note
    This is a split-off thread from https://www.metabunk.org/oroville-dam-spillway-failure.t8381/

    Since the eroson of the main spillway is the key risk now water levels are under control, I've created this thread to keep track of any changes in the erosion at the "waterfall" location. Inevitably there will be some "head cutting" and the erosion will the move up the hill. However it seems to have stopped since Feb 10, and the hope is that it is now stable with the spillway spilling over a rock-bedded location.

    This is a single topic thread on the progression of the waterfall erosion. Please stay on topic as much as possible. Off topic posts may be edited or removed.



    Closeup on the latest DWR photo taken 8:55 this morning.

    20170215-085456-q1f9s.


    Appears pretty consistent with this image from Feb 11, so that's good.
    20170214-132216-m7jwj.
     
    Last edited: Feb 15, 2017
    • Like Like x 3
  2. Mick West

    Mick West Administrator Staff Member

    Of course if the main spillway fails further back then there will be major problems. The thing is there's absolutely nothing to suggest it is eroding back at all in the last three days. It seems entirely unchanged.

    I posted the comparison before:
    There's no detectable difference. And yes, I labeled on image as 2016, but quite obviously it's 2017. You can look up the image yourself.
    http://pixel-ca-dwr.photoshelter.co...00PCdyEjzDuNk/FL-Oroville-2601-02-14-2017-jpg

    I also posted an earlier comparison showing how it went back 330 feet in a few days. The obvious inference here is that it was receding rapidly backwards and then it stopped.

    Please refrain for baseless fear mongering here. Even in the unlikely event of the entire main spillway rapidly collapsed there's plenty of time to shut down it down, and then evacuate people over at least two days before the emergency spillway flows. And that's the worst case. Right now the main spillway is running perfectly fine at 100K cfs. Probably because it's running on rock.
     
    Last edited: Feb 14, 2017
    • Like Like x 2
    • Agree Agree x 1
  3. Mick West

    Mick West Administrator Staff Member

    • Agree Agree x 2
  4. Mick West

    Mick West Administrator Staff Member

    This CHP video from Feb 13 shows the rock bag transport, and has some close-ups of the waterfall.

    Source: https://www.youtube.com/watch?v=_rx2hhTi8I8


    20170215-074509-nz7pm.

    And the bottom of the e-spillway
    20170215-074621-vovpx.

    Middle of the e-spillway - shows how it's fairly well contained once it gets into the ravine. However this is only with a day or so of max 12,000 CFS.
    20170215-074719-ov6fl.
     
    • Like Like x 2
  5. Mick West

    Mick West Administrator Staff Member

    And comparing the video to this one shot 33 hours earlier, looking at the North edge of the Waterfall
    20170215-075358-le00d.
    There has been no visible erosion there over that time, which is good.

    Of course there's no guarantee the waterfall will continue to work, but at least there are no signs of it failing.
     
    • Like Like x 3
  6. Mick West

    Mick West Administrator Staff Member

    Last edited: Feb 15, 2017
  7. JCL

    JCL New Member

    It looks like it's creeping closer to those towers to me? Very hard to see from a front angle though, side shots show it better...
     
  8. Mick West

    Mick West Administrator Staff Member

    Attached Files:

    • Agree Agree x 2
    • Like Like x 1
  9. Roy W. Spencer

    Roy W. Spencer New Member

    If the current main spillway situation remains stable for weeks/months of high flow, is it possible they could just finish off the end of the existing concrete flume [...]?
     
    Last edited by a moderator: Feb 15, 2017
    • Agree Agree x 2
    • Funny Funny x 2
    • Like Like x 1
  10. Mick West

    Mick West Administrator Staff Member

    Certainly the cheapest option. I think there is some possibility they will do that on a temporary basis at least.
     
    Last edited: Feb 15, 2017
    • Like Like x 1
  11. JCL

    JCL New Member

  12. Mick West

    Mick West Administrator Staff Member

    Reminder This is a single topic thread. The erosion progression at the waterfall. Please do not drift off topic. Discussions so be restricted to if the erosion is progressing, how it might be stopped, and what the immediate effects will be of progression.
     
    • Like Like x 1
  13. MortarBoarder

    MortarBoarder Member

    Avoid using that orange fence as a primary landmark. It is a safety barrier for workers and will be moved based on safety decisions. The power line towers are presently convenient markers, but might get removed soon.
     
    • Like Like x 4
  14. smfrnz

    smfrnz New Member

    Not sure if this has been reported but,
     
    Last edited by a moderator: Feb 15, 2017
    • Like Like x 1
  15. Mick West

    Mick West Administrator Staff Member

    The fence is useful, so long as you check it's position relative to other things. The bushes are not going to move.

    Unfortunately it's had to find shots from precisely the same angle.
    20170215-100941-vqnar.
     
    • Like Like x 1
  16. Mick West

    Mick West Administrator Staff Member

    20170215-101901-b560k.

    That appears to be normal rain erosion which also exists in this 2015 Google Earth image.

    20170215-101959-66umf.
     
    • Like Like x 3
    • Useful Useful x 2
  17. john r

    john r New Member

    great confirmation, crack is not a crack.

    Is a tweet or twitter post, with-out a source even allowed here? (probably better to debunk and move on anyway.)
     
  18. Mick West

    Mick West Administrator Staff Member

    Photos are photos. The "crack" was just a small bit of erosion side-lit by low sun so it looked darker and hence deeper.

    This misidentification could easily have been magnified into fears that the side of the waterfall bowl was going to collapse - so it's good to debunk it as early as possible.
     
    • Agree Agree x 1
  19. skicopper

    skicopper New Member

    Last edited by a moderator: Feb 15, 2017
  20. Mick West

    Mick West Administrator Staff Member

    Can you quote what they actually said?
     
  21. deirdre

    deirdre Moderator Staff Member

    around 14 minute mark (nothing abnormal, just the design criteria of the dam)
     
    • Like Like x 2
  22. David T

    David T New Member

  23. Mick West

    Mick West Administrator Staff Member

    20170215-155052-qsaai.
     
    • Like Like x 1
  24. Mick West

    Mick West Administrator Staff Member

  25. OgeeWeir

    OgeeWeir New Member

    There will be cavitation and venturi erosion on the trailing edge of the concrete, I do not care how it is attached to the bed, eventually "I Feel" there will be damage and erosion working upward.
     
    • Agree Agree x 3
    • Like Like x 1
  26. Mick West

    Mick West Administrator Staff Member

    Of course there will. The question is how long will it take.
     
    • Like Like x 1
  27. Paul Bogdanich

    Paul Bogdanich New Member

    Two questions, how good are the supplies of pictures (I was looking for them when I found this site) for continuing reference and two, does anyone know anything about the geology? From the press conference is sounds like they put the gates of the main spillway on or near some bedrock. I hope it extends out on the spillway side a good bit.
     
    Last edited: Feb 15, 2017
  28. A. Hunter

    A. Hunter New Member

    New poster here. Can anyone address the increase in sediment to the left of the main spillway? It looks like there might be a parallel erosion channel sharply cutting into the hillside directly left of the waterfall. I wonder if the left side of the waterfall will soon look like the right. LInk below is a picture from today.

    http://pixel-ca-dwr.photoshelter.co...TE/DK-Oro-Spillway-damage-4065-02-15-2017-jpg

    20170215-205858-6ctha.
     
    Last edited by a moderator: Feb 15, 2017
    • Like Like x 2
  29. Mick West

    Mick West Administrator Staff Member

    The partial erosion channel is the result of the useage of the emergency spillway, which is no longer in use.

    It's from various construction round the corner near the power station
     
    Last edited: Feb 15, 2017
  30. thor1872

    thor1872 New Member

    New poster here too and i think he is talking about this.
    erosion.
     
    Last edited by a moderator: Feb 15, 2017
    • Like Like x 1
  31. A. Hunter

    A. Hunter New Member

    20170215-205858-6ctha.
    The channel I'm referring to is much narrower and to the right of the bedrock e-spillway channel. In the picture below, it's in between the red line and the runoff of water north of the concrete sidewall of the waterfall. It has gone from waterfall runoff on Tuesday to heavy sediment today. Pic source DWR. http://pixel-ca-dwr.photoshelter.co...K-Oro-Spillway-damage-02-15-2017-IMG-4211-jpg

    16716005_1324841790904092_3162118306214832886_o.
     
    Last edited: Feb 15, 2017
    • Like Like x 1
  32. First time poster here as well. Great forum. I think that A. Hunter's statement "parallel erosion channel sharply cutting into the hillside directly left of the waterfall" is referring to the flow (new) that can be seen to the left side of the left wall on the main spill way. It is shown clearly in the attached photo (very high definition and very useful). Also note the small stream of water just further to the left of the wall. Will the stream get larger and further accelerate the erosion to the lower surface bounding the main spillway?
    rx1HIA2.
     
    Last edited by a moderator: Feb 15, 2017
    • Like Like x 1
  33. I wasn't able to attach the photo in its original high resolution, but if you go the original posting for photo rx1HIA2 above (I can't seem to find it now - was it removed?), you should be able to zoom in the area of interest...
     
  34. Mick West

    Mick West Administrator Staff Member

    I retract my previous statements. While there is some red sediment coming from the construction round the corner this is clearly a new ravine being formed from this spot:

    20170215-220419-cdjat.

    20170215-220331-caxfj.
    20170215-220305-tyfrx.

    If this continues it will probably just lead to a widening of the fan below the waterfall, and the continues destruction of the structure of the lower parts of the spillway (already pretty much a total loss)
     
    • Like Like x 1
  35. rx1HIA2.
    I have cropped the original photo down to the area of concern. If you look closely you can see a large bypass flow just to the left of the left wall, and a small "creek" with running water a bit further to the left. Reading his latest posts, I think A. Hunter is referring to the creek.

    A couple of additional concerns come to mind with the newly formed/forming ravine. More sediment and debris will make its way to the river, and will complicate plans to restart the power station. Also, it might accelerate erosion upstream, as the water can focus equally on the left side and the right side of the undamaged spill way, above the sink hole. Also, I am not an expert, but the larger the eroded area on the hillside, the more prone the area will be to large scale mudslides.
     
  36. A. Hunter

    A. Hunter New Member

    Thanks everyone for your input and I appreciate the close up images. I was having trouble locating them. This forum has been an incredible wealth of information. It will be interesting to see what happens with this newly formed ravine and how the waterfall continues to shape with a continuous 100k CFS output (for how long?) and impending storm/rainfall.
     
    • Like Like x 2
  37. Ln X

    Ln X New Member

    With this new flow which is causing erosion on the right side (right side downstream from the dam) of the main spillway, the steep cliffs close to the electricity pylons could collapse a bit and threaten the two electricity pylons nearby. Perhaps the electricity pylons should be removed to stop them getting entangled upon the main spillway?
     
  38. aczlan

    aczlan Member

    That was already covered in the other thread ( https://www.metabunk.org/oroville-dam-spillway-failure.t8381 around page 16 or so) but there are plans to fly the towers out by chopper once there is time/availability/cooperative weather.

    Aaron Z
     
  39. Paul Bogdanich

    Paul Bogdanich New Member

    No new pictures on the CA Dept of Water Resources website today (02-16-17). Anyway of seeing how the back-cutting or lack thereof on the main spillway is proceeding? Outflows are still 100,000 cfs. Inflows are up to 37,000 cfs with the rain. Lake level still falling.
     
  40. Ecomorphologist

    Ecomorphologist New Member

    Some inferences of moderate validity about erosion prognosis might be drawn from examination of the vegetation in the high resolution photo provided above in post #32 by retired mech eng (https://www.metabunk.org/attachments/rx1hia2-jpg.24694/). I hope that link is correct. I draw also from comments on geology by other astute and knowledgeable posters here, to wit, that the solid grayish rock is more competent than the brownish orangish rock and (certainly) soil. That fits my field experience and is backed up by plenty of science on the weathering continuum from competent bedrock, through "weathered rock" to "soil" which after all is just highly weathered rock with a higher level of biological content and activity than harder rock. It is never ideal to speculate without the benefit of a site visit, but I perceive areas of broken woodland canopy with shrubby, probably chaparral understory on grayish substrate, and areas where there is much more (bright green) grassy cover on browner/oranger substrate. Based on my field observation in analogous foothills sites, the former vegetation generally grows on more competent rock with a very thin layer of weathered rock/soil. (This is somewhat corroborated by the shallow depth of gullying of the gray rock, seen in photos in posts #30 and #31, above.) The latter grows on more weathered material with deeper soils; which is more susceptible to erosion.

    The failure of the spillway occurs just about right where a band of the grassy/orangish soil abuts the spillway. There is the grayer, hypothetically more competent material downslope on the left side, and extending far upslope on the right side (viewed as in the photo; thus right bank and left bank of the spillway looking in the direction of flow). Where the browner, hypothetically weaker material intervenes, that's exactly where the failure is. There is clearly some very competent rock still sitting at the bottom of the waterfall, right in line with the chaparral/grayer material on the left side (in the photo). And, remarkably, a lot of the concrete (at least, the visible left wall) is still intact despite being subjected to a lot of energy impinging on exposed upper edges. I suggest that this means that the concrete that's placed right on the gray material, not on (heavens!) fill or the more weathered material, is not likely to erode much even under severe circumstances of extended periods of 100,000 cfs flow.

    There is a narrow band of orange brown soil with darker green vegetation along the left side of the spillway; I speculate that that represents a body of backfill placed after excavating down to build the spillway. That's where the minor new erosion noted by Mick West is occurring, caused by water escaped at the sidewall breach above. It's either backfill or a tongue of that more weathered material; in either case, more susceptible to erosion than the gray stuff that's still happily bathing in the bottom of the waterfall.

    Returning to the critical upper part of the spillway, above the breach, the woodland/chaparral on grayer material seems to run along the whole of the right side. There is slightly higher headcutting on the left side than the right, again supporting the statement that the woodland/chaparral/gray substrate is more resistant. It is not reassuring that the headcut scarp on that right side is brown/orange material, but the exposed rock peeping out through the vegetation above is gray, and hopefully that means getting more competent as one moves uphill. In any case, I think the pattern of vegetation and other clues suggests that the hard gray rock certainly extends (at the surface, overlain immediately by the concrete) partially underneath the intact upper spillway. Probably the construction documentation does not even show precisely its extent there, but the fact that the headcutting did not propagate much uphill from the original failure of the concrete suggests that it probably extends right across. Given how well pieces of the concrete in the lowest gray-rock area have remained attached, it's plausible to infer that the upper spillway is also well attached, in close contact, to competent rock and will probably not fail and headcut all the way up, even if fractures develop or additional pieces of the slab are lost.
     
    • Like Like x 4
Thread Status:
Not open for further replies.