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Washington landslide: catastrophic but predicted

Hillside moves across river and takes lives
Hillside moves across river and takes lives
D Kostelnik Juarez

In a year with lower than normal annual rainfall, March hit Washington with a deluge of twice the average monthly deposit. Amid rising temperatures, a crushing wall of tumbling mountainside wiped out homes and destroyed lives. Today volunteers are pouring into the area with friends on their minds.

Rescuers have been working around the clock to find the hundreds of missing - the neighbors and families buried under washed-away trees, rock and acre-feet of mud since last Saturday morning in the community of Oso, Washington.

No warning?

In an instant, the rumbling flow of tons and tons of soggy mountain broke through the still air and inundated the valley, crushing houses and lives. For most residents, the tragedy occurred without warning. However, in a 1999 report, geologist Dr. Daniel Miller of Earth Systems Institute, predicted this catastrophe in accurate detail. Snohomish County is a beautiful wooded area north of Seattle where landslides come with the territory - hilly and wet, and sometimes quaking.

Then in 2006, following a minor slide, according Ken Klein, an official with Snohomish County, plans for new housing development moved forward in the area now inundated; according to Klein, the decision was based not on concerns specified in the Miller report, but only upon conclusions that the Stillaguamish River was stable enough within its banks.

The mountain of evidence in the Miller report apparently went unnoticed, though it detailed the likelihood of further degradation and pending disaster from allowing further development of the area. Miller interviewed with KIRO-TV in Seattle after the slide and expressed frustration that the county opted not to recognize the signs and to permit construction directly in line of what the report identified as unstable mass.

Seismic records indicate a minor tremor of 1.1 on the Richter scale 10 days prior to the landslide, centered 100 feet from the slide and another slightly larger earthquake (3.3 on the Richter scale) last month. In his scientific report, Miller identified the risks, the history of slides, the potentials for catastrophic disasters like the one Oso is now facing.

The Miller report described this very occurrence; he spelled out the causes and the results. Today more than a square mile of developed property lies beneath a mountainside.

With slightly higher temps, the troubles multiply. As groundwater saturates the area, the hillside turns from the texture of a moist chocolate cake into a warm chocolate shake, and the soaked soil flows more easily. Minor changes in temperature and major changes in rainfall amounts and intensities put at double jeopardy the most tenuous of leaning hillsides.

Many mountainsides that remained stable for centuries are now reaching saturation and beginning to slowly move on down wherever they can settle, and the likelihood of more and more similar slides is daunting in a land where our real estate values are frequently a function of our views.

It’s a Hard Rain

Landslides are regular events in the Pacific Northwest, the Rockies and Appalachia. Wherever mountainous formations face rain and erosion or earthquakes, we will find the tumbling masses. In the US each year we lose 25 to 50 people to this natural occurrence. We spend $4 billion undoing what nature washed over.

As temperatures have risen since the 20’s, rainfall patterns have skewed off the charts in parts of the country and completely under the table in others, and real estate development has fleshed out our now soggy hillsides, experts predict far greater losses in the near future.

According to David Montgomery, a geologist at the University of Washington, “If the climate changes in a way that we get a lot more rainfall you would expect to see a lot more landslides.” The month of March is so far the 5th wettest on record. David differentiates between soaking rains and the intense variety Washington endured this month. “The character of the rainfall that we get, whether it’s more high intensity rain or more of the long soak would actually influence the type and style of landslides that we might expect to get but the short answer is, you know, if we get more rainfall we ought to expect to see more landslides and this region already is landslide-prone.”

An environmental policy analyst with Washington State Department of Transportation, Carol Lee Roalkyam puts it this way: “{We face}..more extreme rain events – the sudden and intense rain that we’ve been experiencing more frequently so a lot of the state routes are vulnerable to landslides today and the projections are that those will be worse.”