Why we risk life and property

They began in the last days of 2004, and carried on through the rest of the winter: Storms that made desert flowers sprout for the first time in a century and restored ancient playas to Pleistocene lakes. On Friday, Jan. 7, 2005, the rain came again, a subtropical plume that dumped up to 18  inches in four days on the already saturated hills of Ventura County, Calif. When it finally let up around noon on Monday, 38-year-old Jimmie Wallet, who had been holed up with his wife and three youngest daughters in the beach community of La Conchita, went out to buy ice cream. He and his older daughter, away at a friend's house, survived the afternoon. The rest of his family did not.

In retrospect, it surprised few people that Rincon Mountain, the amphitheatrical scarp that holds La Conchita in its perilous embrace, exploded in a thunderous current of earth and debris that day, burying 33 homes and 10 people in a mountain of mud. The La Conchita disaster was every bit as predictable as the mudslide that killed 43 people in Oso, Wash., on March 22, 2014. But at the time there was horrified disbelief: "How could it happen that suddenly an entire hillside turns into a liquid flow of earth and rock?" wrote Los Angeles Times columnist Al Martinez in La Conchita's immediate aftermath. Just as the day after the Oso tragedy, John Pennington, head of Snohomish County's Department of Emergency Management, called Oso "a completely unforeseen slide," that "came out of nowhere."

In fact, had the residents of Vista Del Rincon Drive in La Conchita, and of Steelhead Drive in Oso, examined their hillsides with a critical eye before they collapsed, they would have seen a steep pitch covered with young vegetation, and above it the arc of a sand-colored ridge – telltale scars of recent slides. (Both hills slumped in 1995; the Washington one slid again in 2006.) In both cases, initial shock quickly turned to incredulity of a different sort: How could so many people – families with children, even – have dared to build homes against such unstable mountains?

Dangerous places in the West, tragically, are often desirable places, both because of their natural beauty and because the land is relatively cheap. Ed Keller, a University of California-Santa Barbara geology professor and the author of Natural Hazards, says that we're increasingly moving into them because the planet is getting crowded: "As the global population continues to grow, we're pushing people out into ever more marginal places," he says. Human activity exacerbates the peril: Clear-cut logging above Oso's Steelhead Drive may have hastened the hill's failure, just as irrigation atop Rincon Mountain contributed to its collapse. But both scarps had been changing shape for many thousands of years, Keller clarifies; they would have slid eventually. What the people who lived there may not have understood is that "eventually" sometimes means next week.

U.S. Geological Survey seismologist Lucy Jones has spent much of her career training the public in risk reduction. She believes that people play dice with geology for the same reason they use one cold winter to refute climate science: "As a society, we have fundamental science-processing issues," she says. "We want yes/no answers; we don't know how to handle uncertainty." Science estimates possibility and risk rather than offering the absolute answers we crave. That allows people "to pick the information they want to hear" and dismiss the rest.

Landslides, which in the U.S. cause an estimated $2 billion in property damage every year, present singular public-education challenges, Jones says, "because we can't pick out in a human timeframe what's going to go when." Nor is there any centralized database of precarious slopes. Seismologists plot earthquakes on a national map, but slide-prone hills only make news after they've done their worst. Some states require prospective developers to solicit reports from geologists, but they also allow builders to "shred (an unfavorable) report and go get one they like better," Jones says. Absent a geotechnical paper trail, no one knows which hillsides to monitor. "Around the country, there are plenty of slopes as dangerous as Oso and La Conchita," Jones says. "You just haven't heard about them yet because they haven't broken loose."

One such place might be East Gros Ventre Butte, which rises above Budge Drive and West Broadway in Jackson, Wyo. In early April, a ruptured water main alerted town managers that their pumphouse had shifted downhill. Budge Drive had buckled, and a bulge had risen in the parking lot of the brand-new Walgreens on West Broadway. Fearing a sudden release of the mountain, on April 9 authorities ordered residents out and businesses closed.

It's too soon, says Assistant Town Manager Roxanne DeVries Robinson, to assign blame: "Our concern right now is with life-safety issues," she says. Later, however,  someone might ask whether it was safe to build under East Gros Ventre Butte at all. As George Machan, an Oregon-based geotechnical engineer, told a community meeting on April 10, several episodes of lowering the grade at the toe of the slide – most recently to build the Walgreens – likely hurried the geological process along, provoking a slow-motion landslide that might soon become a catastrophic one.

Today in La Conchita, life carries on along flower-lined Vista Del Rincon Drive, next to the buried wreckage where Jimmie Wallet dug for hours and risked arrest to try to save his family. One house sold not so long ago, a two-story with balconies, priced at less than $400,000 for four bedrooms and three baths – just a mile from where smaller houses sell for millions. It's hard not to fantasize about waking every morning to the ocean view, the seabirds, the easy, consistent surfing at a beach break just steps away. I mean, what are the odds?

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