...[S]ome are now questioning whether many of the homes should have been built at all in the valley below a hillside that commonly shifts, sending mud raining down about once a decade. At least four new homes have been built since the last major landslide muddied the valley eight years ago.
The Snohomish County officials who control land use permits asserted last week that there was no way of knowing a giant mudslide would ever happen there. In fact, the area was primed for just such an extraordinary event, according to geologist Daniel J. Miller, who twice surveyed the area for local Native American tribes who rely on the river’s health for fishing and for the Army Corps of Engineers. He wrote in his 1999 report that the Hazel Landslide, as the mountain is known, was constantly shifting, experiencing landslides and would one day suffer “a catastrophic failure.”
...An ancient glacier is jutting out of the mountain, making its flat plateau unstable, Miller said. The Stillaguamish River was eroding it from below. Rows of conifer trees that helped to mitigate erosion by sucking water through their roots and releasing it into the atmosphere were chopped down by loggers. Rain fell on the bald spots they left, drenching dirt and sand, making the mountain even more precarious.
March 2014 has been a record-breaker, the wettest in Seattle’s history. Miller realized his warning was not heeded when he visited the site following a major landslide in 2006 that did not do nearly as much harm. He could not believe what he saw.
...Charity Prueher, 41 and raised in Oso, said homeowners rarely mentioned the slides. When they did, the coursing mud was considered a small disruption, more of an annoyance than a major problem. “They’re so content with the beautiful place where they live, they don’t think anything would happen,” Prueher said....
Lisa Bishop and her dog, Cody, with Northwest Disaster Search Dogs, watch as a Washington National Guard helicopter flies over the debris field caused by the mudslide in Oso, Wash., March 27, 2014. US National Guard photo