We in Washington have had plenty of warnings about lahars, tsunamis and other natural threats. But the deadly potential of a steep, rain-soaked hillside — as common a sight as the state offers — has been hiding in our blind spot.
Hindsight is wonderful. In retrospect, the monster slope that collapsed on the town of Oso on March 22 gave fair notice.
The locals knew the hill was unstable. One of its local nicknames was “Slide Hill.” Nearby are “Slide Creek” and “Mud Flow Creek.” It had a long record of shrugging its flanks into the valley below.
Geologists had documented landslides in the area stretching back thousands of years. They happened frequently after heavy rains. Scientists started warning of worse to come at least as far back as the 1950s.
A geologist working for the Tulalip tribe warned in 1988 that logging could lead to “massive and catastrophic failure of the entire hillslope.” (Excessive logging might have contributed to the Oso catastrophe.) A 1999 report for the U.S. Army Corps of Engineers noted a “potential for a large catastrophic failure.” In 2010, Snohomish County report again flagged the hill as a potential danger.
Why didn’t anyone do anything? Perhaps because nature is full of threats, and humans are forced to prioritize them. In this corner of the world, the public is not conditioned to see hills as mass killers. Volcanos and avalanches, yes. But prior to the Oso catastrophe, there was nothing like the Oso catastrophe. A falling 600-foot-high wall of mud and trees was beyond most of our imaginations.
Now we know. It’s obviously a good time for Pierce County and other counties to be reviewing their emergency management plans and maps of potential natural hazards.
Even more important, the U.S. government should wake up to the threat of disastrous slides. Local governments are only as good as their information, and the federal government reportedly has no current surveys of dangerous slopes.
Powerful airborne laser scans can now pinpoint the hazards in a given region with extreme accuracy. The U.S. Geological Survey would logically do this mapping; Congress should appropriate the necessary funds.
But even the most thorough mapping won’t eliminate the risk. There is no reason to believe that Slide Hill was the most dangerous hill in Washington — others may threaten larger numbers of homes in more populated areas.
Western Washington is packed with mountainsides, foothills, gorges, bluffs and other steep slopes. All of them can get supersaturated with water during the rainy season, and it’s hard to predict which ones might be on the verge of giving way.
Washingtonians love the views, and they don’t tend to abandon their homes over threats that seem hypothetical. Bet on this: Despite the March 22 disaster, people will continue living under the foothills overlooking the North Fork of the Stillaguamish River.
Everything possible must be done to prevent a reprise of what happened to Oso. Ultimately, though, many of us will choose to stay in places threatened by floods, tsunamis, lahars and slides. The risk is part of the price of living in such strikingly beautiful surroundings.