Traffic is detoured along a section of Interstate 84 following a landslide Wednesday night. Inevitably rocks will fall on highways along hillsides and mountains, but what triggers a landslide?
The Oregon Department of Transportation monitors 120 areas that are at-risk for landslides in the Portland area, including the Gorge. ODOT spokesperson Don Hamilton says the organization has some measures to prevent landslides (like the recent Jefferson Street Rockfall Repair in which ODOT cleared loose materials and put in mesh and plants to hold soil in place along Highway 26).
He says he wasn’t sure of the history of landslide prevention in the Gorge.
“Each site is different,” says Hamilton. “We’ve had issues in the Gorge. It’s essentially a rock wall.” He says this landslide was likely caused by a combination of precipitation, loose soil and strong winds in the area.
ODOT crews are working to clear the road — nearly 200 truckloads worth of rocks.
Oregon Department of Geology and Mineral Industries tracks landslides throughout the state.
“(The Gorge is) really steep and it got a lot of rain,” DOGMI chief scientist Ian Madin says. “Much of the geology in the Columbia Gorge is landslide prone.”
His advice to the public is to watch when the National Weather Service issues flood or storm warnings.
“Water is what causes landslides 99 percent of the time,” Madin says. “And when you add water and steep slopes, you get big problems.”
The stretch of eastbound I-84 and one westbound lane between Troutdale and Hood River in the Columbia Gorge will remain closed through the weekend. Hamilton says if you witness a landslide on the road, you can contact Traffic Management Operations Center at (503)-283-5859. Call 911 in emergency situations.