State looks at landslide mapping, emergency response after Oso slide


Nine months after the tragic Oso landslide, a state commission convened after the disaster is about to recommend a series of reforms in land use, landslide mapping and emergency management.

The 12-member commission, created by Gov. Jay Inslee and Snohomish County Executive John Lovick, won’t issue its final report until Dec. 15, but its recommendations are starting to circulate. It’s good to see that the commission wants the state to undergo sophisticated mapping of potential landslide hazard zones.

The first steps outlined in the commission’s draft involve launching a program to map landslide dangers throughout the state. The maps would use LIDAR (Light Detection and Ranging) technology. They would gauge risks for busy roads and rail lines, as well as other critical infrastructure, including the I-5 corridor and mountain highways. Maps would include predicted runout zones.

The group is recommending that DNR’s Division of Geology and Earth Sciences oversee the mapping. DNR could bring in geology professionals from outside the agency to assist.

“It would make sense to draw expertise from the wider geologic community,” said UW geomorphology professor David Montgomery, one of the commissioners.

State and local officials also need to improve their coordination, especially with local volunteers willing to help in such large-scale disasters, according to the commission.

At the Tuesday meeting, commissioners largely agreed that government needs to do a better job of responding to landslide disasters — from mobilizing official responders to incorporating skilled volunteers. Loggers and construction workers from the Darrington area played a big role in pulling survivors and 43 bodies from the muddy wasteland created by the massive Oso slide.

“They’re very knowledgeable about working in sort of chaotic environments,” commission director Kathy Lombardo said. “So they were very, very helpful for the first responders and all the other responders that came.”

A new episode of the PBS science show Nova is also shedding new light on the Oso slide.

Made by Bainbridge Island filmmaker Liesl Clark, “Killer Landslides” balances the emotional stories of first responders and survivors with a state-of-the-science look at what likely happened at Oso on March 22.

While much of the material will not be new to Snohomish County viewers, “Killer Landslides” is essential watching for anyone wanting to understand the science of landslides. That science is framed by dramatic storytelling and imagery.

Clark used interviews with survivors, including Amanda Skorjanc and Robin Youngblood, to dramatize the overwhelming scale of the slide and cost in lives and livelihoods. The interviews are accompanied by footage of emergency operations.

On the science side, University of Washington geomorphologist David Montgomery and U.S. Geological Survey hydrologist Richard Iverson play prominent roles. Montgomery serves as a tour guide of the slide zone, walking the headscarp and poking through the soil and describing its characteristics. Iverson demonstrates how analyzing the debris flow enabled rescuers to more easily find victims in the mud.

The episode’s director, Liesl Clark, told that the show is partly about lessons shared by anyone who lives near steep slopes.

The film provides viewers with an overview of some of the causes of landslides like the one that happened in Oso/Darrington. We also point to telltale signs as seen on other slopes around the world, like slumps in a slope’s topography, cracks at the crown of a hill, and smaller slides that form on slopes that are beginning to fail. The film looks at the specific geologic materials on Hazel Hill, the slope above the community of Oso that slid, and shows the value of LiDAR imagery on sloping terrain that is of concern. LiDAR can provide visual information about past landslides that might have occurred in any area, indicating a pattern.

I looked up the LiDAR imagery for my neighborhood, for example, on the south end of Bainbridge Island and was surprised to see that my house is situated at the head scarp of an ancient landslide that occurred here, the only one on the island. It doesn’t help, that we’re also next to the Seattle Fault line. This is all visible through LiDAR. Now I’m going to be particularly interested in studying the nearby topography for signs of slippage, will watch for increases in precipitation, and might even get a geologist’s report on the geologic materials that our home is sitting on and share that with neighbors.

The more informed we are, the better we can make decisions as homeowners and keep an eye on the slopes around us.

The full NOVA episode originally aired on PBS last month but can be watched online here.