Let’s remember the catastrophic Oso landslide, which happened on this day in 2014 (March 22)
It’s the deadliest landslide in US history, and when it was all over, 43 people were dead and 49 houses destroyed.
On Saturday, March 22, 2014, at about 10:37 a.m., a catastrophic landslide hits Steelhead Haven, near the community of Oso, between Arlington and Darrington in Snohomish County, with a loss of 43 lives and with several survivors sustaining significant injuries. It is to date the deadliest landslide disaster in United States history. The landslide occurs in the 29400 block of State Route 530, about 17 miles east of Arlington, and destroys more than 30 homes in the small community of Steelhead Haven. It creates a debris field a square mile wide and 20 to 80 feet deep. The slide blocks the North Fork Stillaguamish River and covers an approximately 2,000-foot-long stretch of State Route 530, which will result in its closure for more than two months. After-effects of the disaster include severe impacts on the local economy, on transportation, and on the environment. State officials will estimate capital losses associated with it to be at least $50 million. Snohomish County manages development in the valley. The Washington Department of Natural Resources regulates logging in the area. The Stillaguamish Tribe of Indians has fishing rights in the North Fork Stillaguamish River.
The U.S. Geological Survey said that the landslide was caused by recent rain conditions that had saturated the soil. Debris from the landslide covered nearly a full mile of State Route 530, hence the hashtag #530slide. In addition, it created a blockage at the North Fork of the Stillaguamish River, creating a flood hazard, the USGS said. The USGS and the National Weather Service are working to see what would happen if this blockage at the river broke, helping to figure out about where flooding could occur.
There were warning signs, and warning signs that a lot of people who chose to live in the area did not know about. According to this CNN report:
Seattle-based geomorphologist Daniel Miller said he would never have built a house around where the disaster occurred. He co-wrote the 1999 report for the Army Corps of Engineers that looked at options to reduce sediments from landslides in the area.
The 56-page study identified “a very large volume of material that could potentially become unstable,” he said this week.
“That’s the portion that appears to have failed in this event,” he said.
Miller cautioned that his study never assessed risk. At the same time, he said that he believes his study was shelved by officials who could have done more than they did.
U.S. Army Corps of Engineers spokeswoman Patricia Graesser said the study spoke to how people were living in the landslide area but the report wasn’t a risk assessment of landslide hazards. Rather, the study was designed to look at restoring the ecosystem for the nearby North Fork Stillaguamish River’s fisheries.
“What we’re looking at in those sites is silt entering the river and silt in salmon spawning beds, and could we do something to restore their habitat,” Graesser said. “It’s documented in there that there was a risk of catastrophic failure and it was documented that people live there. But that wasn’t the purpose of the study.”
The 1999 study clearly states a 60-year history of landslides in the area, notably in 1937, 1942, 1951, 1952, 1967 and 1988.
“I currently have no basis for estimating the probable rate or timing of future landslide activity,” Miller’s study states. “The primary conclusion to be drawn is that mass wasting activity will persist for as long as the river remains at the toe of the landslide.”
The proposed restoration project ended with Miller’s study because there was no further funding from Congress and Snohomish County, Graesser said.
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