Mudslides

Mudslide at Oso, Washington. Dozens dead, scores missing.

Mudslide at Oso, Washington, March 29, 2014. 43 dead.

The site of a fresh mudslide from a distance always looks so cleanly cut, as if a shovel dug into the wet ground and simply lifted the hillside away and dropped it gently a couple hundred feet down. Grass and shrubs and even small trees are often left in place. Come by in a few weeks, after the rains have stopped and the sun is out and you can see wild flowers in all their colors where people and houses used to be. Sometimes the people and houses are still there, after the survivors had given up hope of ever digging them out again. The old hillside becomes their tomb, and the flowers just make it pretty.

Oso Washington...mud

Another view of the Oso slide….mud everywhere.

Once you recognize the shape you can see mudslides all over the place in southern California, recent ones and old ones. They’re not uncommon. In fact they’re usually so small as to even be newsworthy. Someone loses a backyard and the people below get their pool filled it. It doesn’t even have to rain for those, a broken water pipe will do it. Even a sprinkler left on during a vacation. But it’s rain that really gets the ground moving. Hillsides become soaked, the soil becomes mud, and mud being heavier than dry soil, eventually, at a certain point, that ground begins to slide downward, and continues to slide until a new center of gravity is found and the movement ceases. One of the amazing things about mud is how the water holds the dirt together into a mass while at the same time makes that mass easy to move. An entire hillside, thousands and thousands of tons of dirt, can suddenly move as if my command in one piece, holding its composition and even keeping its topsoil in place. With all our engineering prowess and computer modelling we can’t do that. We can’t make a hillside move in such an orderly fashion down a hillside in one piece, and in a matter of seconds. We can start avalanches and rock slides, sure, those are easy. We can blow a mountain to kingdom come to get at what’s inside. But we can’t just make a whole hillside shift downward a few hundred feet without disturbing the flowers. That’s a matter for rain and gravity and fluid mechanics.

Mudslide at Oso. the grin

Mudslide at Oso. The grin.

Mass wasting is the technical term, gravity making shit fall down. Rocks falling down all the time in California. Our mountains and hills are very young and haven’t been worn down smooth yet by erosion, and besides that a lot of the material is made up of fragile sedimentary rock that breaks up and falls back down easily. Quake, rain, flash flood,. high winds, fire zone…everything comes down out in Southern California. If you ever drive along the base of the mountains in Pasadena, say, you come across these enormous catch basins designed to capture all the stuff that begins falling down in heavy rain…including boulders that weigh hundreds of tons. Those things used to roll for miles, trashing everything in their paths. I love this state, always exciting.

The effects, as in Oso, Washington, can be horrific. Sometimes merely destructive. In 1995 there was a very impressive mudslide above the village of La Conchita, between Ventura and Santa Barbara. For months afterward the 101 there was covered with a thin layer of mud, and if you looked up at the bluffs you could see a classic view of a hillside dropped down a couple hundred feet and resting atop what had been a street.

For a while afterward houses stood with their insides protruding through their front windows. Just imagine how much mud could make a house do that. Down the other end of the street the mud had buried houses completely. Then in 2005 the hillside came down again but much more quickly (here’s some terrifying video) and took out more streets and houses. Ten people died in their homes.  A whole family was entombed in one, save for the father, who had stepped out to go to the store. He spent days walking the streets calling out the names of his children. No one knew what to say. When I saw the news of that mudslide in Washington, saw the scar where the hillside had been, and the hillside now where the houses had been, I thought of that man again, looking for his children.

La Conchita mudslide, 1995

La Conchita mudslide, 1995

On the back slope of the ridge I live on here in LA you can see another old slide. There’s a big concrete wall holding it back off Riverside Drive. I remember sitting at a gas station years ago and wondering what the hell that big slab was there for and then saw the shape of an old mudslide. It was like a miniature version of that hillside in La Conchita, scooped out of the ridge and deposited fifty or sixty feet below. I asked a few other people if they saw anything there. They said no. I guess you have to know what to look for.

Once the scar is grown over again and green, it doesn’t look so menacing. You have to stare hard to realize what you’re seeing. Once you do see it, though, you can never miss it again. You can, in your mind’s eye, take the piece of the hillside that is now below it and pick it up and put it back where it was and see what a perfect fit it makes. But there it is, at the foot of the ridge. I can’t imagine that this slide buried anything. Some ground squirrels, maybe, a few tarantulas. Some California poppies. Some of the snow birds wintering on the street there (we call that stretch the Riverside Riviera) might have found their beat up vans engulfed in a foot or two of mud. But I don’t think there were any structures there. Somewhere down there on Riverside Drive was an old gay bar, but I don’t know where exactly. Some of the older guys from the neighborhood–all gone now–told me stories about the place. A total dive, they said, a wreck. Every winter they had to open the back door so the water coming off the hill could flow through the bar and out the front door and onto Riverside Drive. Some winters the place would be full of mud. It was a popular place, though. But that bar, whatever it was called, is long gone. From what I was told–and this is just hearsay–the place was condemned as a hazard because the ground behind it was unstable. So maybe it was where the hillside came down. But I have no idea what happened to it. Perhaps the patrons just got tired of muddy shoes.

Anyway, they’re talking about another El Nino rainy season next year, which we desperately need, so more of these ugly gaping smiles where hillsides used to be will appear throughout Southern California. Especially in burn areas. Next summer well after the rains (should they come) you should be able to see them. By the following spring, after a few rains again and the grasses turn the hillsides green, they’ll really stand out, big brown scars where green slopes should be, and below them, mustard and lupine and poppies waving in the breeze, yellow and purple and red. Pretty.

Mudslides have been one of the prime shapers of our topography here in southern California. Mudslides on the hillsides, debris flows down the mountains, earthquakes and floods . You don’t like the lay of the land now, just wait till the next big rain. Something’s bound to give.  Just don’t be there when it does.

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(Great National Geographic article on the slide: Mudslides Explained: Behind the Washington State Disaster)

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