The mountain ranges of the Pacific Northwest may appear solid and stolid, but they’re a geologically active part of the physical environment, including regular earthquakes, landslides, and the occasional volcano. And sometimes human activities – including the clear-cut logging that patch-marks much of the region – have an important impact on forests, soils, and water patterns.
As rescue and recovery efforts continued Friday morning, officials reported that the number of confirmed dead remains at 17 with another nine bodies located but not yet recovered. Ninety more individuals are still unaccounted for – large numbers in a community that had totaled about 180 people.
“Rain and wind are working against us,” Snohomish County Fire District 21 Chief Travis Hots, principal spokesman for search and recovery efforts, said at a briefing Friday morning. Another inch of rain in the area was forecast for the day.
"The areas that are already very saturated with water and muddy, that's just going to further complicate things,” Chief Hots said. “It's going to be a very difficult day."
As rescue workers, specially trained dogs, and heavy equipment move carefully through the area, longstanding questions are being raised about logging there and how it might have contributed to the slide.
The hillside in and around the slide area, which slopes steeply down toward the river, has seen much clear-cut logging over the years. Much of the forest there is second- and third-growth timber, replanted or regenerating naturally after earlier cuts.
Concern over logging’s impact has involved environmentalists and native American tribes. Large, old-growth trees take up more water than younger stands, which can take decades to mature and may be cut down before they reach full maturity. The demand for lumber, plywood, paper, and other wood products is part of an industry that once dominated Washington State and Oregon.
The Tulalip Tribes were so concerned with landslides hitting the Stillaguamish River and its prime salmon habitat that they blocked a proposed timber sale above an earlier slide in 1988.
"There were some very large clear-cuts planned for that area, which made us very concerned," Kurt Nelson, a hydrologist with the tribes, told KUOW, the NPR affiliate at the University of Washington in Seattle.
"That reach of the North Fork has multiple, ancient, deep-seated landslides," Mr. Nelson said. "There's a lot of unstable terrain in that area."
Landslides have followed logging in that area at least four times, KUOW reported.
"There was cutting in the 1940s; it failed in the '50s. There was cutting in 1960, then it failed in the mid-'60s. There was cutting in '88; it failed in '91. There was cutting in 2005, and it failed in 2006 and in 2014,” said geomorphologist Paul Kennard, who worked for the Tulalip Tribes in the 1980s and now works for the National Park Service at Mt. Rainier.
"This had been known at least since the '50s as one of the more problematic areas on the Stillaguamish for perennial landsliding," Mr. Kennard said.
Although state logging regulations have been tightened in recent years, The Seattle Times reports that a clear-cut nine years ago “appears to have strayed into a restricted area that could feed groundwater into the landslide zone that collapsed Saturday.”
An analysis of government geographical data and maps suggests that a logging company “cut as much as 350 feet past a state boundary that was created because of landslide risks,” the newspaper reported.
This is an area above the most recent slide. Scientists and officials are investigating whether that clear-cut could have contributed to the current disaster.
Meanwhile, the request by Washington Gov. Jay Inslee (D) for more federal assistance to help with recovery efforts in the Oso area has been approved. The money will be used to help local and state government agencies recover a portion of the estimated $4.5 million expected to be spent on emergency response, protective measures, and debris removal.
At his briefing Friday, Hots asked corporations and businesses in the region to donate money to help those affected.
“Some of these people have lost their homes, some have lost their cars, some have lost their entire family,” he said. “Funerals will have to be paid for. Please dig deep.”
The possibility that dozens more people may be buried in the gray-toned debris pile of rocks, mud, twisted trees, vehicles, and crushed buildings has the potential to place Oso among the worst tragedies in Washington State history. The 1980 eruption of Mt. St. Helens killed 57 people, and a 1910 avalanche near Stevens Pass swept away two trains and killed 96.
"We do know this could end up being the largest mass loss of Washingtonians," Governor Inslee said Thursday. "We're looking for miracles to occur."
• This report includes material from the Associated Press.