New technology helps predict landslides

The laser system can identify areas that are prone to damage

By John Denny

The Clackamas Review, Jan 27, 2009, Updated Oct 30, 2009

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Indeed, Oregon City Public Works Director Nancy Kraushaar said the city planned to essentially write new development codes around the maps once they’re released.

“We already updated our geologic hazard codes to provide even more peer review of the geologic investigation of the properties, but when these maps come out we’re going to change the code again and have it relate to the susceptibility of the map,” she said. “We’ll use that directly in our development code for identifying properties that require geologic investigation.”

City Commissioner James Nicita said there are many different ways the maps could be implemented, but said he does look forward to them as a resource.

“Each landslide area’s going to have its own particularities to it and I would be concerned about a one-size-fits-all development standard given that landslides and their age and their type and their level of risk would be different and that’s where the inventory would really help,” he said. “There may be some high hazard extreme areas of landslide hazards, where it’s just glaring red on a map and those might be candidates for prohibiting development. But I would be open to hearing arguments as to why you could develop on those areas. I’d also want to hear the counter argument as to why prohibition might be warranted in certain cases.”

Current homeowners

“For existing homeowners, the local government will be able to work with them on mitigation strategies, and even if the local homeowners want to go themselves, they’ll be able to take these maps, figure out perhaps if they need to do something,” Roddey said. “But just knowing whether you live in a landslide-prone area is kind of the first step.”

One thing that experts think led to the slide in the west hills was inadequate water drainage, saturating the soil until it slid away. Homeowners could hire a geotechnical engineer or work with the city on mitigation practices, especially water drainage and diversion.

The susceptibility maps aren’t available yet because they’re being peer-reviewed.

“We have to cross all our Ts and dot all our Is, because once they’re published, these basically become the de facto standards,” Roddey said. “So we have to vet these through many many folks.”

The project was funded in part by the Legislature, which gave DOGAMI $1 million in startup funds and told it to leverage that to get more from outside sources. The department ended up with about $5 million total.

The next area to be mapped using LIDAR will be areas of Washington County.

Maps online

While the susceptibility maps are still being reviewed, the state has released comprehensive landslide maps online. To see if you live on or near a landslide, visit oregongeology.org.

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