PORTLAND, Ore. (KOIN) — With a death toll now at 14, the massive mudslide in Oso, Wash. Saturday March 22 has caused more deaths than any other landslide in Oregon in the last 100 years.
But, according to one geological expert, those deaths may have been preventable — if Snohomish County had invested in more maps that assess landslide risk, using Lidar technology.
The maps are built taking into consideration the risk of landslides in a particular area, and there is a major disparity between which counties are well-mapped, and which aren’t.
“We’re in a a cutback government mode,” said Portland State University Geology professor Scott Burns.
“Most counties don’t look at natural hazards.”
“We have the ability now to make those maps but nobody wants to pay for them,” he said.
Salem and Portland, on the other hand, have extensive, up-to-date Lidar-built maps documenting past landslides as well as thousands of potential risk areas.
“If the climate models are correct, we might be seeing more precipitation in the Northwest, putting us at a higher risk for landslides,” said Burns.
Average annual repair costs for landslides in Oregon run more than $10 million. The West Hills area of Portland and the area surrounding Oregon City are particular hotbeds.
With the risk of a landslide assessed, a potential homeowner can decide whether or not to apply for landslide insurance (which is difficult to obtain) or whether to live in the area at all.
No one in Oso likely had landslide insurance, said Burns.
“All those people who lost their houses lost everything,” he said.
How a landslide happens
Three factors must be at play for a landslide to occur.
“Steep slopes and weak material, soil wise, and you’ve got two strikes against you,” said Burns.
A third “strike” — the trigger — is either caused by a seismological event, or excessive rain or snow, he said.
In the case of Oso, Wash., the village was built under a steep slope with a river at the bottom, with weak soil and had seen tremendous rainfall in the weeks leading up to the slide.