Steep slopes & water
Back in 2014 local public radio did a story on The Little Street at the Bottom of a Landslide-prone Bluff aka Y R people so dumb?
It’s no secret that Western Washington is prone to landslides. The combination of glacial soils, steep slopes and water creates a risk that’s greater than in other parts of the U.S.
And it’s not just river valleys like the one near Oso: The region’s coastal bluffs are also danger zones that have experienced large landslides in recent decades.
But that still doesn’t deter people from living in those slide-prone areas.
Because people are just that dumb.
Ruth Trail has lived in the Magnolia neighborhood of Seattle for 23 years.
She said she loves it for the views. Standing in a park that sits atop a bluff overlooking Elliot Bay, Trail can see downtown Seattle, Mt. Rainier, West Seattle and the Olympic mountains.
The views are indeed nuts. That’s why I take my dog friend/client there often. The boulevard is neither straight nor flat so the vista changes as you go, and it’s all breathtaking. It’s just…don’t live at the foot of it, you know? Don’t put your expensive house at the bottom of a landscape-prone bluff. Put it at the top, a healthy distance back from the edge (all the houses on the boulevard are across the street from the edge). Safer.
It was here, 18 years ago, that a deep-seated landslide hit. During an especially wet winter, a big chunk of the bluff collapsed, wiping out five houses below.
From above, on the boulevard, you can see where it happened. You can go up to the fence and look down at the empty space.
Geologists consider Perkins Lane Seattle’s poster child for landslide risk.
“The Perkins Lane area has been failing back since the 1930s; and probably long before that,” said David Montgomery, a geomorphology professor at the University of Washington.
But there are houses on it. People live in them. People live in them and even stay in them after a couple of inches of rain fall in a matter of hours.
When the slope at Perkins Lane failed in the winter of 1996, residents were lucky in a sense: The slide moved slowly, and they were able to evacuate their homes. No one was killed.
This time not so much.
Now, the portion of the street where the big slide hit is closed off, and no new homes have been built in the slide zone. But many homes remain nearby, in an established and rather pricey community, perched between the steep bluff above and the water below.
One of which just got taken out.
My guess is that residents believe they’ve done the necessary risk assessment when they’ve actually just performed rationalizations. “On the one hand, there is this very real possibility of sliding disaster which I’m aware of and have studied. Very concerned, I am. But, on the other hand …” And then they think of the difficulties in housing and finding and affording the right property along with the fact that hey, it hasn’t happened yet and it’s a crap shoot which ones if it does happen, etc etc. Eventually, iit culminates with something inspirational about grabbing life and taking chances because Life is meant to be Lived! And nobody gets out alive!
My guess then is they’re maybe fractionally dumber than the rest of us, and at least half of that is circumstantial.
Also, beside the fact that the normally stabilizing forest cover that used to be here is gone, there’s the fact that Seattle is basically built on a giant landfill. It doesn’t take much of a slope on that kind of stuff to become water-logged and slide. If it’s not built on bedrock, it’s not safe, and when the big #9 quake finally arrives then even that is going to be unsafe.
The Berkeley hills are composed of pure, slippery, clay. The heavy rains of 1963 sent a bunch of houses sliding down the hills. All ambitious, pillar and cantilever cracker box constructions from the 40s-50s. There are somewhat better zoning standards now. But not much better.