You know the Oso landslide? The collapse of a rain-sodden slope that buried a lot of houses, vehicles, animals, and people in a small town north of Seattle two weeks ago?
It’s been reported heavily in the local media, but as a natural disaster and human tragedy, not as something that had been predicted and warned about for decades. Well guess what – it was predicted and warned about decades ago.
Rain is the fuel for landslides in wet western Washington. The tall trees of the Evergreen State help hold the ground together, not just with their roots, but also by soaking up rain before it goes deep underground. That’s why the state essentially prohibits clearing of forests in places where groundwater can pool beneath a landslide zone.
Kennard: “The clearing just makes it much more vulnerable for when you have a wet winter like now.”
Kennard works at Mt. Rainier National Park now. But in the 1980s he worked for the Tulalip Tribes north of Seattle. Even back then, tribes and state officials knew the Oso site had a long history of landslides large and small. 26 years ago, Kennard helped the tribes stop a clearcut on the same slope that gave way last week. The tribes saw it as a victory for the salmon they depend on in the Stillaguamish River at the base of the muddy slope.
Kennard: “We considered it a victory because the Department of Natural Resources, who has say over these things, this was the first time to our knowledge that they actually prohibited clearcutting of trees because there seemed to be a connection with landslides.”
And they prohibited it on the Hazel slope, which is the slope that gave way and fell on Oso two weeks ago, killing a lot of people and animals. Gosh gee what a coincidence.
So, on the night of the latest slide, Kennard was surprised when he looked up the area on Google Earth. He saw an aerial photograph with a clearcut from 2005 right at the edge of the landslide zone.
Kennard: “I thought, whoa, that seems to be awfully close.”
Aerial photos taken of the Oso slide last week show a wall of exposed earth hundreds of feet high, almost directly below that 2005 clearcut.
State officials say the cut they approved was safe: it was just outside the no-logging area intended to keep groundwater from building up. But those aerial photos also show that the seven-acre clearcut crossed the line. Here’s Washington State Forester Aaron Everett.
Everett: “It appears, though we continue to investigate, that there’s been an intrusion into the no-harvest area.”
That intrusion apparently happened at the hands of the landowner, a small timber company called Grandy Lake Forest Associates. But the company has not responded to interview requests.
Brilliant, isn’t it? Grandy Lake Forest Associates got a few more trees and so a few more dollars – and a bunch of people in Oso got killed.
That 2005 clearcut? The state allowed it right on the boundary of a no-logging zone that didn’t reflect the latest scientific information. State-funded research from eight years before the clearcut showed the groundwater danger zone clearly overlapping with the area the state OK’d for clearcutting. Everett says the DNR is investigating what happened.
Everett: “The protections that the department puts in place to ensure that timber harvest do not contribute to landslide hazards are rigorous and are designed to protect public safety and natural resources. It’s a difficult thing to talk about in the face of a tragedy like this.”
Geologists say identifying where groundwater moves beneath a landslide zone is hard to do precisely.
Here’s geomorphologist Paul Kennard:
Kennard: “Perhaps what is sort of the legal definition of the groundwater recharge area is actually a small part of the real groundwater recharge area. All that area has been cut and it takes decades to recover.”
Kennard urges more cautious landuse anywhere near one of these deep-seated landslide zones.
But geologists also urge people not to jump to conclusions about the role of one small clearcut in 300-acre landslide. They say detailed study of this slide is needed before concluding how much of a role, if any, the recent clearcutting played.
Ok. Don’t jump to the conclusion that it was for sure logging that caused the landslide. Ok. But you know what? It seems like the kind of thing where you err on the side of caution, by a wide margin. You have what a geomorphologist considers a slide-prone hill right above a town. That seems like one stand of trees you just leave alone.