Earthquake, rain behind deadly Mudslide in Oso, Washington StateBaltimore Post-Examiner

Earthquake, rain behind deadly mudslide in Oso, Washington State

Aerial photograph of the Oso mudslide, taken by the Washington State Patrol on March 23. (Wikipedia)

On Saturday morning, March 22, just before 11 a.m., a massive mudslide wiped out roughly 50 homes along the Stillaguamish River in Snohomish County, Wash., between the towns of Oso and Darrington. Reports estimate that the sliding earthen mass reached speeds of up to 100 mph. Two mudslides occurred, one after the other, from the same hillside. Each mudslide lasted about two minutes and stretched nearly a mile out from where they calved from the hillside.

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A Google Maps view of affected area before the 2014 mudslide.

The death toll as of the morning of March 25, 2014, was 14. No one knows how many bodies are buried under all that mud, reportedly up to 50 feet deep in some areas. Travis Hots, chief of Arlington, Wash., rural fire district, expects more fatalities to be confirmed in the coming weeks as recovery efforts continue.

A distant view of the affected area on March 23, 2014. (Carl Niedermeyer)

A distant view of the affected area on March 23, 2014. (Carl Niedermeyer)

Search-and-rescue organizers have set up a telephone and email hotline for people to report missing persons. The hotline as of late Monday had received nearly 200 sources of input. Some media sources are listing this number as “missing persons,” but, in fact, the total is merely the number of separate sources of input the hotline has received. This means that, for example, several sources of input may be for any one person reported missing, such that the actual number of missing persons amount to far fewer than 200.

A direct view of the affected area on March 23, 2014. (Carl Niedermeyer)

A direct view of the affected area on March 23, 2014. (Carl Niedermeyer)

Further hampering rescue efforts is the concern that yet more earth may slough off of the original hillside. Worse, while weather has been dry since the weekend, more rain is forecast for much of the remaining week, with some flood warnings. Rescue workers describe attempting to walk on the mucky goo as like walking on quicksand.

Geologists have described the material that came loose in the mudslide as clay and sandy glacial soil piled onto bedrock. When that loose material becomes thoroughly saturated from a season of rain, conditions are prime for gravity-induced disaster. Recent reports suggest that a small earthquake in the area several days prior to the mudslide may have contributed to the event.

This same hillside shed some earth in 2006, but on a far smaller scale. Carl Niedermeyer, a pilot from nearby Everett, Wash., took aerial photographs then and now, several of which are featured in this article. The 2006 photos show how that slide blocked a bend in the Stillaguamish River. No casualties or injuries were reported from the 2006  mudslide.

This image shows the extent of the 2006 mudslide. Note the community to the left of the straight section of river, which re-joins the blocked sections of river. (Carl Niedermeyer)

This image shows the extent of the 2006 mudslide. Note the community to the left of the straight section of river, which re-joins the blocked sections of river. (Carl Niedermeyer)

Recent news-helicopter reports show countless homes on the upstream side of the Stillaguamish river flooding from the backup.  The river did start flowing downstream late Sunday, perhaps 18 hours after the blockage occurred, according to USGS river-flow graphs online.

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USGS graph shows river flow at Arlington, Wash., downstream from the mudslide before and after the slide.

Some observers wonder if effects of global warming may have contributed to the mudslide. According to wunderground.com rainfall data, the rainfall in the mudslide area in the last seven months has totaled about 9 inches. Additional rain in the coming days could further endanger, and delay, recovery efforts.


About the author

Mark Forseth

Mark Forseth is a regulatory technical writer with the Federal Aviation Administration in Seattle, Wash. His career has centered on public-broadcast journalism and technical writing for such industries as GE Medical; ABB Robotics; Harley-Davidson Motorcycles; Allen-Bradley Motion Controls; Johnson Controls; and Imago Scientific instruments, among others. Contact the author.
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