Tuesday, March 25, 2014

The Osos (or Hazel or Steelhead) Landslide in Washington State - Can Geologic Information Be Better Utilized by Non-Geologists in Geohazard Assesments?

Addendum and update (added on January 2, 2016): A University of Washington study has shown that this area has experienced a slide on average every 140 years for the last 2000 years. See a story here.

Addendum and update (added on April 23, 2014): A fantastic scientific account of the slide was posted on the USGS blog site. You cam access that link here, and visit the related links inside of it. WR

View downstream of the Oso or Steelhead landslide of March 22, 2014. Photo courtesy of Jay Inslee
A devastating landslide in Washington state on Saturday, March 22 was an accident waiting to happen. The area had experienced numerous slides within the past 65 years, with the most recent event occurring in 2006 (see the table below, from the Yakima Herald). Unconsolidated glacial debris (composed of loose, uncemented rock, sand, and mud) deposited during the Ice Age is responsible for the weak substrate in this part of the Cascade range. To find out more about the geology of the area and the history of recent movements on the slide, see this excellent blog posting here. The Seattle Times published a story and an excellent graphic here (use your cursor on the first graphic to see a cartoon drawing of the area before the slide and a photo superimposed after). In addition to the geologic hazards, nearly 14 inches of rain fell within the last 30 days, making something like this virtually inevitable. To understand the recent weather component of this event, see Jeff Master's Weather Blog here.

Also see some excellent before and after pictures here.

Past landslide events or reports about this area:
  • 1949: A large landslide (1000 feet long and 2600 feet wide) affected the river bank
  • 1951: Another large failure of the slope; the river was partially blocked
  • 1967: Seattle Times published an article that referred to this site as “Slide Hill”
  • 1997 report, by Daniel Miller, for the Washington Department of Ecology and the Tualialip Tribes
  • 1999: US Army Corps of Engineers report by Daniel and Lynne Rodgers Miller that warned of “the potential for a large catastrophic failure”
  • 25 January 2006: large movement of the Steelhead landslide blocked the river

View upstream of the Oso landslide. Photo courtesy of Jay Inslee
With the death toll at 41 and 4 people still listed as missing (April 23), this a geo-tragedy of epic proportions. I saw the first images of the slide while watching a national Saturday night newscast. When I first looked at an aerial image of the area, I could easily discern the convex indentation in the slope of a hill that screamed, "landslide." And then the newscaster announced that this was the before picture of the area. An obvious earlier landslide was in plain view to anyone with basic geologic training.

So it was not a secret that this area was ripe for more sliding. A report filed with the U.S. Army Corps of Engineers in 1999, warned of “the potential for a large catastrophic failure”  on this slide. The report was written by Daniel Miller and Lynne Rodgers Miller (husband and wife). When she saw the news of the mudslide Saturday, she knew right away where the land had given way. He did too. Read their quotes and the ones below in this article from the Yakima Herald.

Yet, John Pennington with the Snohomish County Dept. of Emergency Management is quoted as saying, “This was a completely unforeseen slide. This came out of nowhere.”  And Snohomish County Executive John Lovick and Public Works Director Steve Thomsen said Monday night they were not aware of the Miller's 1999 report. “A slide of this magnitude is very difficult to predict.There was no indication, no indication at all,” said Thomsen.

So it goes. Geology once again in the backseat in our society, while some of those in power stick their head in the sand, denying obvious science. One has to wonder to what extent the people who chose to live there, essentially staring up at the barrel of a geologic shotgun, were made aware of or sought out information about the landslide hazard here. They must have known something I would think. I also wonder if the hazard was downplayed in any way by developers or real estate agents? In my personal experience, most people buy homes without a hint of awareness about geohazards. Look at any flood event, earthquake, even volcanoes. People tend to think that "it won't happen to me or in my lifetime". And agents Often do what they can to make the sale.

Make no mistake, this is a tragedy deserving of our sympathy to the victims. At some point however, we have to take a stand against misinformation used to promote pure, economic interests. In the 21st century, we have the resources and the know-how to understand many geologic and meteorologic risks. Yet certain segments of our society routinely use their resources to denounce science as "uncertain", "risky", or "damaging to the economy". Scientists need to become advocates for people who may otherwise live in harms way.


Timothy Egan in the New York Times: http://www.nytimes.com/2014/03/30/opinion/sunday/egan-at-home-when-the-earth-moves.html?_r=0

Andrew Alden at About.com Geology: http://geology.about.com/b/2014/03/25/washington-landslide-completely-foreseeable.htm?nl=1

Lee Allison's Arizona Geology Blog: http://arizonageology.blogspot.com/2014/03/is-this-teachable-moment-for-dealing.html

Photo from CBS News:

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