Photo of Oso slide

Discussion in 'Fly Fishing Forum' started by Richard Olmstead, Apr 3, 2014.

  1. This is the best pic I've seen of the Oso slide. It is and aerial taken from somewhere upstream and shows the extent of the slide AND the reservoir formed on the upstream side. I'm not sure when it was taken, but I think you can see why the state is worried that the river might commit to a new channel following the route of hwy 530, if something isn't done.

    Go here for the accompanying story:


    Ron McNeal likes this.
  2. Good shot Dick - thanks for sharing.

    There's a disturbing story in today's Seattle Times indicating that Snohomish County had commissioned a study back in 2004 that concluded that the very slope had a high danger of a catastrophic slide into the Steelhead Haven community and recommended the county buy out the homeowners there to minimize the risk of damage to property and loss of life.

    Facing the possibility of a large price tag and prolonged process, the county opted instead for a cheaper option and try to mitigate the risk of a slide and stabilize the hillside. Two years later, the county approved a number of building permits for homes in the affected areas. Several of those recent homeowners are now either confirmed dead or among the missing.

    The current or former county officials who were party to that report and the decision not to proceed with a buyout all seem to have developed amnesia and can't recall any of the details.

    Evan Burck and Ron McNeal like this.
  3. The photo reminds me of the landslide that caused Quake Lake on the Madison in Montana. Most folks think of a landslide as something similar to an avalanche of dirt... this is much larger than that. It's like half the hill collapsed.

    No wonder so many folks are missing. Sad.
  4. Anyone know then that particular hill was last logged?
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  6. I read that article and put it together with the land plat shown there overlain on a pre-2006 aerial photo, and concluded that the action considered by Snohomish county was to buy a series of undeveloped parcels to prevent further development, including many that were wiped out by the 2006 slide and subsequent rerouting of the river channel, NOT the homes already occupied.

    The fact that the total estimated bill for buying the properties was only $1.1 million for 75 parcels didn't seem like it could include the developed parcels, too, but the map includes the developed parcels. Maybe they did consider buying everyone out, but I'll bet they would have met with strong opposition from residents.

    Kent Lufkin likes this.
  7. You could well be correct Dick. In Danny Westneat's column in the Times back on March 25 he described how King County bought 20 or 30 homes in the Rainbow Bend area of Maple Valley starting 20 years ago that were in a flood plain. At over $10M it cost the county a LOT more than the $1.1M figure from today's article which I also thought sounded ridiculously low.


  8. Not sure if any of you have seen this video. It is one man's analysis via google maps of a decade prior to the slide. Just click the start and enlarge. Pretty compelling, but please remember it is one man's opinion. Since this thread is about the possible effects of logging above the area it seems appropriate to bring it up here.

    From the photo at the start of this thread it appears to be flat to the north of the slide area and that does not seem to compute with the thrust of the video. Not sure how to bring that photo together with what this person presents in the video.


    I tend to concur with someone's comment on the unknown facet of the bonafide's of the guy giving the lecture, so I have taken it off. Probably should have tried to check the guy out.
  9. Mark, thanks for posting that link. After watching it I come away thinking (among other things...) that there's more to come.....
  10. Kent and Richard...the papers don't know the whole story...on the Maple Valley buy out, it took over a decade and King County taxpayers paid a lot more for the property than the appraised values, just to get recalcitrant folks out. In Oso, the folks were, shall we say, are less willing to trust government than...and whenever County officials tried to talk about curtailing development, much less buying out folks, they were met with quite stiff resistance. You can only imagine if County government had tried to do a buy out program and got sued. A jury from Snohomish County would have more than likely not only gone for the property owners, but it could have been expensive for the County. You have to always remember in cases like these, hindsight is 20/20. But at the time, the folks who wanted to develop and live in that area were not about to move.

  11. Ok, having watched this video I also need to respond...who is this guy? Is he a forester? A soils specialist? I was falling off my chair listening to him. He knows nothing about soils, soil saturation, infiltration, how storm water reacts to cleared areas. Much less, he is unable to read an aerial photograph (to talk about different vegetation).

    That isn't to say logging may have been a contributing factor, but so-called experts like this can be dangerous in this age where every plaintiff's lawyer in Washington is vying for clients from Oso. But I will tell you, if this guy gets on the stand and any forester with a Bachelors, can totally impeach his testimony...

    Sorry, don't mean to rag, but this is really bad.

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  12. I absolutely hate the practice of clear cutting. I have nothing against logging but you'll never find me supporting clear cutting.

    That said, it is unlikely that clear cutting done in 2005 was the total cause of the landslide. It reads to me as if the area was known as unstable and those in charge certainly didn't do much to divert the disaster. No more clear cutting should have been allowed after the study indicated the hill was in poor shape. The current land owners should have been advised of the danger and a market value should have been offered for them to sell out and move. And most certainly, they shouldn't have allowed additional homes built in such a potentially dangerous spot.

    So it was the perfect storm of mistakes and ignorance.

    Most likely the clear cutting didn't help matters but I can't see that it was the entire cause of the slide. The slides I've seen that can be traced back to clear cutting happened within a few months or a year of the cut.

    Not 9 years later.
  13. There is going to be a lot more coming out...there was salmon/steelhead restoration work done on the river, very near the toe of that slope, by a variety of interested stakeholders to the Stillie...among other issues. No reporter has looked at HPA permits to see what alterations, if any, were done to the river course over time.

    And you are absolutely right, GAT, there is no one cause, but many. We live in a geologically new area, soils and the rocks are pretty young. They are glacial. We have, and will have, storms of great velocity and quantity, then periods of relative drought, causing soils pores to open and then saturate. Water mounds on top of the till areas (also known as hardpan), meaning, essentially, that water "flows" uphill.

    There was vegetation at the top of that hill at the time of the slide. It wasn't Doug fir, but Alder and Big leaf maple, restoration vegetation from a site that has been "worked" (Alder will be the first to grow in at this slide area). Those are hardwoods, so during the wet season, no leaves, but there was vegetation...anyway, many contributing factors to the slide and many contributing factors to why those folks didn't leave, including, perhaps, not enough information.

  14. I have mixed feelings about clearcutting. Unmitigatedly bad for biodiversity and I oppose it on public land, but as a 'farming' practice on suitable private property, it makes sense.

    As for the effect of the 2005 and earlier clearcuts, I disagree with Gene and agree with the professional foresters and geologists who point out that clearcuts have serious effects on ground water movement long after the clearcuts have been done. A mature tree, like a Douglas fir, moves a tremendous amount of water from the soil into the air. The young trees from the clearcuts that dated to the late '80s move much, much less, and the vegetation on the 2005 clearcut almost none by comparison. Instead of being intercepted by the fungi and associated tree roots and translocated upwards, that water percolates down through the soil until it finds an impervious layer, where it pools, saturating the soil, and then moves laterally, creating the perfect conditions for a slide of the sort that occurred in Oso. It happens on a smaller scale in clearcuts throughout the wetter parts of the PNW. Those smaller slides often happen in the first year or two after a cut, but they are trivial by comparison to a big one like this.

    I'm not saying the 2005 cut, or even clearcutting at all was the cause of this slide, but it was likely a contributing factor. The Lidar land surface images that have been posted from the N. Fork Stilly area show some old, pre-clearcut slides in that area that are as big or bigger than the Oso slide, so they can certainly happen without clearcutting.

  15. Kim,
    Looking at the sat images of the area, I think you are mistaken that the area above the slide is not conifers. The area below the old slide scarp face (which includes a substantial portion of the slide area north of the river) appears to be deciduous. This is the area impacted by the 2006 slide and was probably mostly alder and bigleaf maple, but the area above the scarp, and, thus, the zone where most of the water is entering the soils, is second growth conifer forest, probably mostly Doug fir and western hemlock.

  16. Richard, you're a right in your analysis, far better than the video...if you look at the "cut" that was caused by the slide, my sense is much of that soil had low infiltration rates (mineralized soils are good for Doug fir and so many of the lowland hills which are perfect Doug fir timberland are similar soils). In addition to the till layers, I would also suggest the upper layers were so saturated, causing enormous pressure on an already destabilized cut-bank at the toe slope, an inverse pyramid if you will.

    On a policy level, these cuts occurred during the last "gold rush" in housing. Just before peak. And there is very little cutting on public lands here in Washington, so the pressure on what remains of privately held timber land to produce product is enormous. And obviously the timber company wanted to get out as much as they reality that last cut was a fairly small cut...

    I haven't looked at the ownership of the cut areas, were they also owned by Summit and Grandy Lake? Or was someone selling the timber to pay for a kid to go to college?

  17. No, you're right. I was indicating the area just above the slide and what did slide. That was hardwood.

  18. I read in one of the many articles about this slide (perhaps the one Kent cited) that the timberland above the slide was owned by a lumber company and that they protested the recommendations to prohibit further cutting, citing that the value of the timber in that area was worth 3/4 to 1 million dollars. Unfortunately, in small county politics, that kind of money talk pretty loudly.

    Kent Lufkin likes this.
  19. Actually it's DNR who they protested to, Snoho county has nothing to do with timber permits. Did they own the timber rights or the underlying land, also? I can look on the assessor's records, I just wonder if someone knows.


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