Landslides after clearcuts

Sandy & John leah8 at athens.net
Sun Feb 22 16:43:54 EST 1998


Having some experience with the occurence of slides in the Pacific northwest, this
article does not present anything new accept to attempt to sensationalize a long
recognized problem. In general responsible forest landowners try to layout harvest
units and roads in consideration of the potential for mass wasting.  Also the article
omits an important contributor to mass wasting, in addition to the amount of rain and
steepness of the slope, an important factor is the detachability of the soil, simply
put certain soils are more prone to sliding than others based on clay content grain
size etc.

John Vona





dwheeler at teleport.com wrote:

> The following is an article which ran in The Oregonian on Friday, Jan. 30,
> 1998.
>
> State study links clear-cuts to landslides
> By JONATHAN BRINCKMAN, of The Oregonian staff
>
> Preliminary results show forested land tends to be more stable, but steepness
> and rain also are key factors.
>
>         The state of Oregon has calculated for the first time that clear-cutting
> increases the chance of landslides, a finding that raises concern in a logging
> industry already beset by government constraints.
>         The study follows massive rainstorms in 1996 that triggered tens of
> thousands of landslides across the state, some of them lethal. Slides
> emanating from clear-cuts killed five people and destroyed at least a dozen
> homes.
>         Now state officials are considering tightening logging rules, to increase
> the public's safety and to protect salmon that spawn in streams that can be
> damaged by logging practices.
>         The study, outlined Thursday in Portland, was begun by the state
> Department of Forestry after the February 1996 storms. It was expanded after a
> November 1996 storm caused more damage.
>         Results of the $370,000 study, which will not be made final until late
> this year, will be used by a special panel convened by Gov. John Kitzhaber to
> recommend changes to Oregon logging rules.
>         The subject is fractious among loggers, those whose homes adjoin prime
> land for tree harvest and the state officials who establish allowable logging
> practice. Landowners who lease to loggers also are entwined in the debate.
>         Roughly 56 percent of Oregon's private timberland is owned by large timber
> companies, with the remainder owned by small firms and individuals. Harvest
> from private lands generated $1.25 billion in revenues in 1996.
>         The findings released Thursday, though confirming for the first time that
> clear-cuts are twice as likely to slide as forest land, indicate that slides
> are driven by variables such as the amount of rain and steepness of slope.
>         Moreover, the scientists conducting the study found that clear-cut areas
> do not always slide more than uncut forests. In the Elk Creek region of
> Southern Oregon, for example, land covered with forests 100 years or older
> slid more frequently than clear-cut sections.
>         But timber inudstry officials were alarmed Thursday by the results thus
> far.
>         "There is a potential that this could be devastating for the industry,"
> said Jim James, general manager of wester timber and logging for Willamette
> Industries, which owns 610,000 acres of Oregon timber land.
>         James said that even if final results confirm that clear-cut areas are
> slide-prone, harvesting prohibitions should not be required. More careful
> logging practices, including construction of fewer roads, might be the answer,
> he said.
>         "I do not foresee that the landslide issue will put us out of business,"
> he said.
>         Jim Geisinger, executive director of the Northwest Forestry Association, a
> timber trade group, called Thursday's preliminary findings alarming. "If the
> ultimate outcome is to restrict timber management on steep slopes, it could
> have a very serious impact on the industry," he said.
>         Environmentalists said the state's calculations set the stage for long-
> needed overhauls of logging practices.
>         "The timber inudstry has had free reign over Oregon's forests for
> decades," said Dougl Heiken, a field representative for the Oregon Natural
> Resources Council. "It's about to be put in its place."
>         Federal scientists and others called Thursday's clear-cut-slide
> calculations "significant."
>         "They've decided to face the music," said David Montgomery, a professor at
> the University of Washington.
>         Gordon Grant, a research hydrologist with the U.S. Forest Service in
> Corvallis, said the study seems to confirm previous findings. "It give us
> confidence that this study and the studies that preceded are right," he said.
>         Department of Forestry officials said their study, which covered a
> patchwork of 52 square miles in the state's coast range, was the most
> exhaustive landslide study undertaken. Rather than rely on aerial photos to
> identify landslides, crews walked 136 miles of stream channels, inspected 170
> miles of road and documented about 600 landslides.
>         The scientists examined eight sites in Western Oregon. Three were chosen
> to represent the most severe effects caused by the February storm, two
> represented the effects of the November storm, and three were randomly chosen
> to represent typical storm effects.
>         Other findings:
>         - Newer logging roads, which are better built and placed in less fragile
> sites than older roads, trigger few landslides.
>         - Aerial surveys detect less than 25 percent of the landslides found by
> researchers traveling streams and roads.
>         - Almost 80 percent of the total landslides that entered streams came from
> very steep slopes.
>
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