OREGON STATE UNIVERSITY

Clatskanie Landslide: OSU Background

12/19/2007

Recent news coverage has raised questions about management of OSU forest lands near Clatskanie, Oregon, including some areas involved in a recent landslide that temporarily closed U.S. Highway 30 and destroyed other property. OSU’s management of these forest lands includes ongoing review of various factors affecting the land, and continuous response to any issues raised. That review and several of the responses include:

-- The university has invested $2.8 million in recent years in state-of-the-art management of these lands, in support of the Oregon Plan for Salmon and Watersheds. The work has improved road drainage and implemented the latest logging, road building and land management practices. Salmon that had been gone for many years are now returning to streams on this land.

-- The lands involved in the landslide had been monitored in the weeks just prior to what the Oregon Department of Forestry called a “catastrophic” rainstorm (12 inches in two days), which triggered the event. David Lysne, director of College Forests in the OSU College of Forestry, said that prior to the storm, there was no evidence of any problems, soil movements, etc.

-- Although there is no evidence thus far to suggest that management activities played a role in causing these landslides, a leading expert in Coast Range geomorphology and landslides (Arne Skaugset, associate professor of forest engineering) will soon do an on-site review of the landslide area near Clatskanie, including an evaluation of logging practices, road construction, drainage management and other issues.

-- Beyond that, the OSU College of Forestry routinely reviews management and logging activities on all of the forest lands it operates for student education, scientific research and timber production, to ensure that all practices meet appropriate standards.

-- Officials at the Oregon Department of Forestry have already indicated they may pursue a review of this incident. OSU will welcome such a review and fully cooperate and assist in its completion.

 

Additional background on these issues:

 

OSU owns 2,440 acres of forest land above the area that experienced a major landslide onto U.S. 30 recently. This is land that has been owned and operated by the university since the 1930s. Part of the OSU forest lands were involved in the slide.

There is no evidence thus far to suggest that OSU’s timber harvesting or research operations on this land contributed to the landslide. One of the first areas that started to move was on a ridgetop, some land that had been logged and replanted about 15 years ago, and since then had no indication of instability. Its drainage ditches were in good shape, there was no road or culvert failure.

Most of the Oregon Coast Range is on land that is inherently unstable, with shallow soil layers on top of bedrock, and steep slopes that have slid frequently since they were uplifted off the ocean floor millions of years ago. For instance, an average acre of Oregon Coast Range forests contains 259 “headwalls,” areas of accumulated dirt and sediments that, historically, have probably experienced a landslide.

The land OSU owned and operated in this area was being used for multiple purposes. One was a research project testing whether unique types of long-term forest rotations could be used to provide harvestable timber while maintaining old-growth characteristics. Another research project was looking at growth models of alder. And some of the land was being used for timber production that provided income for other college educational and research operations.

In this particular case, the fundamental problem was that large amounts of fill from old railroad construction formed a type of dam on land above U.S. 30. Drainage issues caused large amounts of water to back up during the recent torrential rains, what is being referred to as a 100-year event. Ultimately the pond collapsed, causing a large mud, water and debris slide onto the roads below.

The link between clearcut logging and landslides is complex. Research has found that logging causes about a 40 percent increase in Coast Range landslides during the first 10 years, if there is a major storm event during that time. But even then, the range of variability is huge – some recently logged areas actually have fewer landslides while others have significantly more. In established forests – such as the primary OSU tract that slid in this case - there is no discernible connection between logging and landslides, and in some cases there is actually a decrease in the incidence of landslides.

About three out of four landslides which occur in the Oregon Coast Range will happen whether or not the land is managed in any way at all. It’s often impossible to tell from the appearance of various areas whether they will be the site of a future landslide or not.

Because of its geologic formation and heavy rains, landslides are a natural, frequent and continual part of Pacific Northwest Coast Range geology, far more than many other mountainous regions around the world.