Landslide tragedy: What’s Central Oregon’s risk?

Saturday’s landslide in Oso, Washington was so large it registered like an earthquake on a seismograph.

The awful aftermath is 1,500 feet wide and 600 feet tall.

“The community was aware of the fact that the landslide was there — it had moved in 2006,” Iam Madin, chief scientist for the Oregon Department of Geology and Mineral Industries, said Tuesday. “I don’t think anyone would have anticipated that it would come down with the speed and force that it did, so that it crossed the river and crossed the valley and inundated the community.”

Madin says usually when a landslide is reactivated, it moves slowly — a couple hundred feet in a week’s time.

The movement of this fast slide is still not over.

“We still have the aftermath of everything trying to settle down as the water moves out of it,” COCC geology professor Bob Reynolds said.

This could take a few more days or even weeks.

Geologists track landslides across the Pacific Northwest, including right here in Central Oregon.

Madin says Deschutes County is void of known big landslide-prone areas But it’s a different story for Jefferson and Crook counties.

“There are some very, very large landslide complexes out there that have probably been going on intermittently for thousands of years,” Madin said.

Many are shown on the maps on oregongeology.org.

“We have had a least one historical mudflow that came out of Broken Top back in 1966, for example,” Reynolds said. “Made it all the way down to the Cascade Lakes Highway and spilled into Sparks Lake.”

Madin says the chance of another mud slide like Saturday’s in Washington state is unlikely. That event, he says, was common, but unusual.

To find out if there are any major landslides in your area, visit: www.oregongeology.org/slido/index.html

“If you find you are on or near an existing landslide, it’s not the end of the world,” Madin said. “Most of these landslides are relatively stable, and as long as they aren’t disturbed they generally don’t reactivate.”