People of Northwest Public Radio
Wed March 26, 2014
Landslide Science Not Connecting With County Planning
The Northwest is a region prone to landslides.
That, of course, is on many people’s minds as the town of Oso, Washington recovers from the tragic slide that happened there this past weekend.
There is a lot of scientific data and maps showing where landslides have occurred in the past.
The question is whether or not it’s getting used.
Bonnie Brown sent me a picture of the cabin her parents built on the Stillaguamish River in the 70s.
“It was just a very beautiful place. With beaver ponds and streams and meadows and trails through the wood. The kind of place that kids dream of,” says Brown.
She also sent me an aerial photo of her cabin after the tragic landslide.
“There’s some grass around the cabin on three sides left but…other than that.”
Her voice trails off.
The second picture shows giant gray fingers of rock and muck and debris encircling the little log cabin.
The slide came down from the cliffs across the river, then up the other side, covering her neighborhood.
Brown’s family wasn’t at the cabin when the slide occurred.
She said over the years her father and neighbors worried about flooding as the Stillaguamish meandered back and forth across its bed. Landslides weren’t at the top of the list of concerns.
But maybe they should have been.
Dan McShane is a geologist in Whatcom County. He said when he heard there was a landslide on the Stillaguamish, he wasn’t surprised.
“The Stillaguamish setting, the geologic units, are particularly sensitive relative to say a real solid granite bedrock somewhere else. So the potential for the failure is much greater,” says McShane.
Towards the end of the last ice age the Stillaguamish River Valley was a giant lake, blocked in by a glacier. It filled with soft lake sediments – sand, clay, gravel – the kind of stuff that falls apart when it’s wet.
And in recent years, scientists are getting a clearer and clearer picture of the scars on this landscape.
Modern imaging technology called LIDAR shows 3-D representations of the Stillaguamish River bed today.
It looks like a little kid took a toy dumptruck with a backhoe and just moved along the river taking giant clam shell bites out of the slopes. Those bites show where landslides have occurred in the past.
McShane says anyone can look at maps and get information like this if they have some time to surf the web.
“It’s public but whether it gets disseminated to the people who make land use decisions and planning for geologic hazards doesn’t necessarily happen,” says McShane.
The disconnect between the science and county officials and planners may have cost some of the residents of Steelhead Drive in Oso, Washington their lives.
A landslide occurred in the same place on the Stillaguamish in 2006, causing flooding.
Snohomish County permitted 5 news homes to be built there that year and another one in 2009.
The Snohomish County Planning Office said they couldn’t comment as to why those permits were issued because they’re busy with the recovery effort.
McShane and others have said the size and reach of this landslide in particular was unprecedented.
No two counties are the same when it comes to incorporating things like new geological mapping technology into their planning or permitting process.
A lot of that variability stems from money, says Scott Burns. He’s a geologist with Portland State University.
"We can make landslide hazard maps just like earthquake hazard maps, just like flood hazard maps but very few of them have been done because we are in a cutback government mode," says Burns.
The Washington Department of Natural Resources has detailed maps, though they’re not as detailed as some of the latest 3-D imaging.
Some counties, like Cowlitz and Jefferson, are incorporating new landslide data into their websites.
Burns says there’s a ways to go and the government needs to invest in hazard maps and use them in the permitting process.
When Bonnie Brown’s father built her cabin in the 70s, the mapping technology we have today didn’t exist.
But technology or not, she has no plans to rebuild.
"The land and what we enjoyed around there is gone and so there’s not the same incentive. I don’t know how long it will take for nature to recover but what was really our family’s past is gone now," says Brown.
Copyright 2014 Oregon Public Broadcasting
Snohomish County Mudslide