fwd: massive landslide threatens Headwaters
mhagen at olympus.net
Thu Feb 19 19:53:37 EST 1998
Hmmm, I've learned a few things in the last week. Never upgrade your browser.
Don't bid a floodplain cruise in spring. Don't explain geotech . Sometimes things
It sounds to me like your freeway slide was likely, maybe even guarenteed. The
slope was undercut. The road at the bottom ensures that the material that rolls off
the hill is removed, preventing a more stable angle of repose from developing. The
fire killed the roots holding the surface soil in place. It may have changed the
slope's capacity to hold both surface and groundwater. It rained hard, making the
soil heavier, less cohesive and lubricating buried slip zones. Pointing to a
single cause of the slide is easy to do, but probably not accurate.
Prevention? Maybe they shouldn't be logging in an el nino year at Headwaters. I
suppose the freeway shouldn't have been there. The houses below the bluff at Rio
Nida(?) shouldn't be there either. It might have been the human activity that
messed things up but other reasons may have contributed as well.
> On 2/16/98, larryc at teleport com wrote:
> >It can be tricky to establish causality in natural events. Landslides
> >are particularly tough, since there's no way to observe what is happening
> >under several feet of dirt and rock. If you see a bare slope slide, did
> >the slide happen because the slope was bare?
> >There has been a lot of recent research on this, since with urban intrusion
> >into rural areas more people are at risk than they used to be. Instead
> >of just flying over and taking pictures, they actually sent geological
> >engineers in on the ground to see what was happening.
> >Current results indicate that the slide did not happen because the slope
> >was bare. Slides also happen just about as frequently on slopes covered
> >by trees. They have been underreported from the air because the trees
> >move right along with the slide, and cover up the signs of damage from
> >However, the recent reports indicate that roads DO cause landslides. It
> >may be that the landslide that covered up the freeway was caused by the
> >freeway at the base of the slope. It may be that a fire road built during
> >the fire fighting effort caused the slide, or maybe a decades old logging
> >road finally cut loose. Or maybe the slope was just ready to slide, and
> >went because it rained and made the dirt heavy.
> >The fire may have caused some surface erosion, but it is unlikely that
> >it caused the slide. You have too many other culprits sitting around
> >looking guilty.
> Sorry to drag this out, but I really want to understand. The slope that came
> down near my home was largely bare slope (actually rock & dirt nearly vertical
> grade) for a long time. The freeway was cut into the side of the mountain.
> The grade was severe enough that there was another slope between the west
> direction and the east direction of the freeway. Prior to the fire, at the top
> of the mountain, there were trees, brush and grasses. So, with the vegetation
> gone from the top of the mountain, the rain going onto and running off the
> "fire bare" land wouldn't likely have produced a landslide? Despite the fact
> that the freeway had been there for decades, the fire only occurred a short
> time before, and heavy rains no doubt did make the dirt heavy, there is no way
> to establish causation to this slide? I'll have to take your word for it if
> you say yes, but it seems common sense that much of the rain that made the dirt
> heavy would have been absorbed by the vegetation had it been there. (BTW, the
> mountain started sliding again in the latest rains.)
> The other point that is confusing me is can government do anything to even try
> to prevent catastrophic landslides? Again, it seems common sense that if you
> keep adding more and more stress on the land, that it will give at some time.
> Maybe they can approve ten timber harvest plans and the logging roads that are
> needed, but what's to say the 11th would not be the one that brings it all
> down? I mean, is the solution no roads? Or is there no solution?
> >> Mind you, I'm not against logging. Not even. What I am against is logging
> >> old growth - leave the elders of all trees alone. Is it really true that
> >> isn't sufficient second growth, etc. to keep foresters and loggers working?
> >That's probably the wrong question. The forestry industry has been losing
> >workers at a great rate for years. Oregon lost 12,000 mill jobs at the
> >height of the Reagan overcut. In order to be competitive, mills had to
> >computerize and automate their operations, and the process that started
> >with the invention of the chainsaw continues. Sites that are level enough
> >are harvested with wood processors that allow one person to do work that
> >took an entire crew 20 years ago.
> >The question should probably be, "Is there sufficient second growth for
> >our needs as a society?" The answer to that one is "not yet." While
> >large industrial forest owners have been reforesting diligently since
> >about 1920, the State of Oregon didn't start reforesting until 1961,
> >and the federal government didn't start requiring reforestation of
> >timber sales until the 1970's. AFAIK, California got into the act
> >about the same time the fed did.
> >There is some natural reprod on the areas that were harvested before
> >replanting, but the land is nowhere near as productive as it could have
> >been with good management. Second growth on federal lands that is ready
> >for harvest is often sparse and limby, yielding inferior wood and not
> >much of it. The well managed areas are only 20 to 30 years old at most,
> >and won't be mature for decades yet.
> >People who advocate making up the shortfall off of private lands forget
> >that the US Government owns 2/3 of all land west of the Rocky Mountains,
> >including over half of all productive forest land.
> >Right now, we are making up the shortfall in supply by importing wood.
> >Most of it comes from Canada, so we're preserving some American forests
> >at the expense of a lot of Canadian old growth. We've also shifted to
> >new engineered materials, like OSB (Oriented Strand Board) instead of
> >plywood, because there is no way the current supply of veneer grade logs
> >could meet the demand, even with imports. There has also been a shift
> >to glue-lam beams instead of milled beams, and finger jointed finish
> >wood, printing press wood paneling, and many other changes to make
> >inferior materials stretch to do the job.
> You're painting a very grim picture for timber workers. It seems they're
> f**ked no matter what.
> Old growth certainly cannot meet society's needs for decades by itself, and
> what happens when it's all cut? IMHO, old growth is old growth, no matter
> under whose flag it stands. Maybe the innovations you describe and other
> processes yet to be developed will save both the old growth and the timber
> workers. I don't see any other bright spots on future's horizon.
> >Headwaters is really being cut down by little old ladies in San Francisco
> >who want redwood planters for their posies, or suburbanites who want
> >redwood edging for their flower beds and redwood decks for a patio, or
> >redwood trim on their hot tub.
> 'Tis true. The fight for Headwaters includes educating the public on what that
> flawless redwood trim really represents.
> >-- Larry
> Thanks for taking the time to write, Larry. :D
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