Slide’s impact hits hard

Part of the landslide blocking a major north-south rail traffic route in Oregon began in a section of the Willamette National Forest that was clear-cut in 1993, but government and railroad officials say it’s too soon to know exactly what caused the earth to give way.

Part of the landslide blocking a major north-south rail traffic route in Oregon began in a section of the Willamette National Forest that was clear-cut in 1993, but government and railroad officials say it’s too soon to know exactly what caused the earth to give way.

The slide occurred in an area about eight miles southeast of Oakridge in the Willamette National Forest where the tracks hug steep forested terrain as they move through the confusing maze of ridges that make up the Cascade Range.

A broad section of northeast-facing hillside slumped down Saturday morning, obliterating 3,000 feet of track owned by Union Pacific under a snowy mound of mud and a jumble of trees more than 20 feet deep.

The majority of the slide occurred on Forest Service land that had not been clear-cut or thinned, said Willamette National Forest spokeswoman Judy McHugh. But part of the slide began in an area that was clear-cut in 1993 and replanted in 1995, she said.

Forest Service geologists hadn’t yet visited the site as of Tuesday afternoon, hampering any discussion of the slide’s cause, she said.

“Our intention is to always manage to protect people and property,” McHugh said.

Generally, three elements play a role in landslides — the steepness of the slope, the composition of the ground and the flow of water, said Bill Burns, an engineer and geologist with the Oregon Department of Geology.

Based on a photograph of the landslide outside Oakridge, Burns guessed it was a “translational debris slide” — more ground and rock than the wetter slurry associated with debris flows that begin at the headwaters of streams, he said.

Such slides can be triggered by heavy rainfall or snow melt, but a change in vegetation can also play a role, he said.

Until geologists visit the site, it would be impossible to be certain, he said.

For now, Union Pacific is waiting for the experts to weigh in, spokeswoman Zoe Richmond said.

“We’re working with the department of forestry, and a few geologists are helping look at some of the causes,” she said. “At this point, we’re not speculating because we don’t know what caused it.”