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More than rain: Why Seattle is seeing so many landslides

State crews work to clear debris from I-90 after a mudslide covered the roadway with debris early Thursday morning. (WSP)

It may appear to some that the Puget Sound region is experiencing more landslides than usual this winter.

“They may be perceived to be more frequent,” Dr. John Clauge said. “But with the growth of urban areas like Seattle and Tacoma, you put homes on land that’s not as stable as we might otherwise wish. And with the growth, they are getting more frequent, but not as a natural phenomenon.”

Related: Extreme threat of landslides in King and Pierce counties

Dr. Clauge is the chair of Natural Hazard Research at British Columbia’s Simon Fraser University. His book, “Landslides,” is a collection of studies and papers compiled by 78 leading researchers on landslide science.

More than rain

Dr. John Clauge said there are a few things to blame for landslides — not just rain. Seattle’s urban growth is one culprit.

“We can see it in Seattle, people moving in the fringes of the urban area (the mountain valleys) where there are a lot of steep slopes,” Dr. Clauge said.

“In the Seattle area, when you have a steep slope and heavy rain that results in water penetrating the slope and that reduces its stability,” he added.

Want to spot landslide potential in your area? It doesn’t have to be too complicated — Dr. Clauge refers to simple common sense.

“Look for ground cracking and trees that we call ‘drunk trees’ — where they lean over,” he said. “Really, look for any sign that the ground may be unstable.”

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