COMPUTER SIMULATION OF OSO LANDSLIDE SHOWS WHAT PROPELLED THE DESTRUCTIVE FORCE
March 22, 2015
(REGIONAL) -- The forty-three people killed in the Oso Landslide in Washington State one year ago today at 10:37 in the morning may simply have had the misfortune to unknowingly live below a huge hillside made of the wrong type of soil.
Oso landslide, ariel view. CLICK TO ENLARGE
Computer simulations released a few days ago indicate that the massive landslide could have behaved much differently - with much less mobility and consequent destructiveness - if the ground had been less porous and thus less water saturated.
The video below, produced by the U.S. Geological Service shows the results of two computer simulations. The first simulation shows computed landslide behavior that best matches that observed at Oso.
An alternative simulation then shows landslide behavior - much less widespread and destructive - that could have occurred if the water-saturated ground had been just slightly less porous.
Details on the Oso landslide and these computer simulations are contained in "Landslide mobility and hazards: implications of the 2014 Oso disaster, Earth and Planetary Science Letters," 2014 (doi: 10.1016/j.epsl.2014.12.020).
Below is a video produced in Sept. of last year by GEER (Geotechnical Extreme Events Reconnaissance) a team of volunteer scientists who visit natural disasters to determine causes and help prepare for or prevent future disasters.
UW geomorphology professor David Montgomery was part of the team that visited Oso and prepared a report on their findings. In the video you'll hear from Montgomery about what the team discovered.
The video below produced by the Wall Street Journal shows how the hillside, super-saturated with rain gave way, again primarily due to the composition of the soil on the hillside and the fact that the Stillaguamish River had, for many years, been eroding the base of the hillside.
When the huge hillside collapsed it sent a raging wall of mud and debris racing across the North Fork of the Stillaguamish River, engulfing the small Oso area neighborhood, and covering an area of approximately 1 square mile.
The landslide engulfed 49 homes and other structures in an unincorporated neighborhood known as "Steelhead Haven" 4 miles east of Oso.
It also dammed the river, causing extensive flooding upstream as well as blocking State Route 530, the main route to the town of Darrington (population 1,347), approximately 15 miles east of Oso
Excluding landslides caused by volcanic eruptions, earthquakes or dam collapses, the Oso slide is the deadliest single landslide event in United States history.