March 29-April 4

The week's best posts, covering everything from breaking the rules to sexual communication.

The Oso Mudslide: Why Do We Live in Harm's Way?

Psychology tells us why so many ignore the lessons of natural disasters.

More than 20 people are dead and at least 90 missing and presumed dead after a huge hillside of mud, clay, and rock collapsed and slid down into their little village of Oso in western Washington. As the search goes on, more a matter of recovering the dead now than rescuing anyone who might still be alive, questions are being asked about emergency preparedness, warning systems, and insurance coverage.

But no one is asking perhaps the most important question of all: What were those people doing living in such imminent danger in the first place?

There can be no clearer example of people ignoring evidence that practically screamed, “Living here puts you in constant mortal danger!” There had been landslides on that hill in 1949, 1951, 1955, 1970, 1984, 1995, 2002, and in 2006, a huge one. There was even one last year. According to a report in the Seattle Times, there were multiple been warnings from officials, including a 1999 Army Corps of Engineers report noting “the potential for a large catastrophic failure.”

Geologists who have studied the hill call it Hazel Landslide or Steelhead Haven Landslide. One investigator wouldn’t even walk on it, saying the ground was too soft to hold him up. Locals used to call the hill Slide Hill and the streams it regularly collapses into as Slide Creek and Mud Flow Creek.

All sorts of human engineering had been applied to reduce the risk, lulling some residents into a false sense of security. Retaining walls, berms, and drainage ditches were built. The river was even moved to reduce how much soil it washed away from the base of the hill. But some engineers warned that all this wouldn’t work. One University of Washington geologist said:

“It is almost impossible from a practical standpoint to stabilize this slide in its present position. The slope will continue to slide and the area will increase. Drainage ditches, dikes, walls, etc., would give at best only temporary relief. The structures would need constant repair and replacement.”

So why did people still live there? Some were apparently in denial, including, tragically, the head of the local Emergency Management department, who said Monday “It was considered very safe," and, “This was a completely unforeseen slide.” Other officials knew but didn’t act, including those with the power through zoning laws and even eminent domain to keep people away from this clearly dangerous site. According to a New York Times graphic depicting building in the slide area, seven homes destroyed in the landslide were built after the 2006 disaster.

Why were they there? The comments of two environmental engineers begin to reveal the real reason. Emotions play a powerful role in our judgments about risk. One engineer said that a proposed plan to buy homeowners out went nowhere because "nobody wanted to sell their property and move.” The environmental manager of the local Stillaguamish tribe said simply, “We always thought there was a possibility that a catastrophic event could come. We were hoping that wouldn’t happen.”

This episode is a clarion example of the Risk Perception Gap, in which, because of the subjective, instinctive, emotional nature of the psychology of risk perception, we fear some things too much, and others too little, compared with what the facts clearly prescribe. This tragedy affords lessons relevant far beyond Oso.

Not everyone who lives in areas at risk for potentially deadly natural events does so voluntarily, of course. But many do, and they must employ a variety of subconscious cognitive tools to allow them the choice of living in a place they like, but which could kill them. Here are just a few of those risk perception factors:

  • Something cognitive scientists call Optimism Bias lets us say, “Yeah it may be a risk, but it won’t happen to me.”

  • The things we do ostensibly to reduce the risk—like reinforcing a hillside that always collapses, building sea walls, shelters, or tornado, volcano, or tsunami warning systems—gives us a feeling of control, and when we feel in control we feel safer, safe enough to live in places where the evidence is otherwise clear that nature is far more in control that we can ever be.

  • We’re lousy at gauging probabilities, so we figure a risk with a low likelihood is acceptable in exchange for a pretty house by the river or shore or forest—even though the consequences could be death. We forget, and never really understand, that a low likelihood in any one year adds up to a relatively high likelihood pretty fast if you string a few years together. The chance of a deadly magnitude 6.7 or greater earthquake somewhere in California (America’s most populous state) in the next single year may be low, but over the next 24 years it is 99.7 percent, a virtual certainty.

  • Natural risks don’t scare us as much as human-made ones. Not a lot of people choose to move in next to nuclear power plants, which are far less likely to kill than the floods and earthquakes and mudslides and hurricanes that hit the beautiful natural places we do choose to live.

In part because of these emotional inputs into decision making, tens of millions of Americans live in “Tornado Alley,” or in coastal areas regularly ravaged by hurricanes. Not far from Oso, Washington, 150,000 people live in the lahar zones of Mt. Rainier, an active volcano. Thousands more live in the danger region around Mammoth Mountain in California, another active volcano. Around the world, hundreds of millions live, voluntarily, in mortal danger from such natural events.

Some of these people will die because of their choices, or because of the poor risk-management choices of local officials who are themselves human and just as vulnerable to emotion-based risk misperceptions as you and I. But maybe, just maybe, the lessons of the Oso tragedy can spare a few of those lives, by teaching us to be more cognizant of how our feelings can impair healthy and safe decision making.

The Risk Perception Gap is real, it has been studied, its psychology is understood, the factors that lead to choices that put us in danger have been identified, and we can apply all that knowledge to making smarter choices. Until we do, though, the hills will keep tumbling down on us, and shame on us for still being in the way.