Landslides common but not catastrophic locally

Officials: It's unlikely what occurred near Oso would happen in Clark County

By Eric Florip, Columbian transportation & environment reporter

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As workers continue to sift through a sea of mud and debris left by a deadly landslide in Snohomish County last week, local officials say there's little risk of a massive event like that happening in Clark County.

That doesn't mean landslides are a rarity here. In fact, slides commonly occur in Southwest Washington and other parts of the state, especially after long stretches of rain saturate the soil. Cases of significant property damage are relatively uncommon, however, though slides have wreaked havoc on roadways and railroads at times.

Locally, one of the most slide-prone areas is the Washougal River Road corridor in east Clark County, according to the state Department of Natural Resources. Another slide area hugs Lockwood Creek east of La Center, and several others dot the northeast corner of the county, according to a DNR map.

Recent years haven't seen anything major in Clark County, said John Wheeler, emergency management coordinator at the Clark Regional Emergency Services Agency.

"Our experience with landslides during that time is we tend to have small landslides," Wheeler said. They often go hand in hand with flooding, another ever-present hazard in the Northwest, he added.

Even small slides can demand immediate action. In late 2012, a landslide ripped away part of the foundation under state Highway 501 in Ridgefield, forcing crews to rebuild the slope supporting the roadway. That followed a similar slide on the same stretch of highway several years earlier.

Slides commonly impact state Highway 14 in the Columbia River Gorge, said WSDOT regional construction engineer Glenn Schneider. And in 2006 and 2007, large, slow-moving landslides ate away at vast slopes north of the Columbia River in Skamania County.

Perhaps the biggest recent landslide in the region occurred in 1990, when a huge portion of KM Mountain shifted and blocked state Highway 4 in Wahkiakum County for more than a year, Schneider said. That slide was comparable to this month's Snohomish County landslide, he said, but only in volume. It caused no property damage or injuries.

WSDOT currently has two funded slope stabilization projects on its radar for Southwest Washington, said spokeswoman Abbi Russell. One will occur at a Highway 14 tunnel in eastern Skamania County; the other will focus on state Highway 97 in Klickitat County.

More than a dozen other stabilization projects are unfunded, Russell said — most of them targeting other parts of Highway 14 in the Gorge.

"It isn't as if anything isn't being done," she said. "But as with anything, there are limited resources and many needs."

Sometimes, those plans change unexpectedly.

"It's unpredictable," Russell said, "but natural."