In the mid-2000s, Cox [a different Cox, not the author of the article I'm quoting] assembled a group at the U.S.G.S. to study what would happen if the atmospheric rivers from two notable California flood years, 1969 and 1986, occurred back to back. They named the resulting scenario the Arkstorm: flooding throughout the state, water depths of up to 20 feet in the Central Valley and economic losses of $725 billion. When the report on this research was done, the authors presented it to emergency managers, municipal authorities and dam owners, including D.W.R. [the Department of Water Resources]. The response was demoralizing. “They said, ‘That’s too big, that’s ridiculous,’” says Lucy Jones, the chief scientist for the project.
The authors of the Arkstorm report had a response ready, however. Their imaginary storm was modeled on the Great Flood of 1862, which also made a lake of the Central Valley and destroyed, by one account, a quarter of all the buildings in the state. “The minute that you say this is too big, this couldn’t happen, this is unrealistic,” says Michael Dettinger, a hydrologist who worked on the report, “I can just point at 1862 and say, ‘1862 was far worse than this.’”
The original plan for the Arkstorm scenario was to have D.W.R. and other agencies translate the storms they had created into water on the ground: turning meteorology into hydrology. But according to Cox, “D.W.R. ghosted the Arkstorm project about three-quarters of the way through.” He never got a straight answer about why, but one of his contacts there told him it was “political.” (“Is that a capital P or a small p?” Cox asked.) My own reporting would eventually reveal another possible answer: The numbers were scary enough to shut down any discussion.The best the Arkstorm team could manage for the final report was this line, buried on Page 59, which read like a statement from a hostage negotiation: “Because of the extremely sensitive nature of a dam-damage scenario, the selection of a particular dam to imagine as hypothetically damaged in such a way is left to emergency planners.”
From the top of Seven Oaks, you can see the crowded valley below, home to more than four million people. If you keep following the Santa Ana, you’ll reach the hills above Anaheim and Orange County, home to millions more. The wave running down the river following a dam breach would remain high all the way to those hills. Nearly a mile from the dam, it would still be 69 feet from top to bottom. By the time it got to the San Bernardino airport, an hour later, it would have spread out and slowed down, at merely 30 feet tall.The inundation map shows all that would be caught in its path. Red dots for fire stations, purple dots for police stations, green squares for schools: Highland Grove Elementary, Cypress Elementary, Lankershim Elementary, Warm Springs Elementary, Bing Wong Elementary, Monterey Elementary, H. Frank Dominguez Elementary, Urbita Elementary, Woodrow Wilson Elementary, Patricia Beatty Elementary, Fremont Elementary, Ina Arbuckle Elementary, West Riverside Elementary.Houses would be knocked off their foundations, warehouses would crumple, commercial jets would be tossed about. Much of the infrastructure along the river, bridges, highways and railroads, would be washed away. Thousands of people would have minutes to evacuate. The death toll would be far higher than that of an ordinary flood. If the surge found a flaw in Prado Dam, which sits above Orange County, all of Anaheim would be added to the inundation zone, Disneyland included, before the water met the sea (emphasis added).
Engineers could keep raising the levees, holding back the water as best they can. Dam owners could build more spillways like the one at Folsom or the ARC spillway planned for New Bullards Bar. And state authorities could get better at evacuations, start drilling for dam failures as we do for earthquakes.Probably California will have to do all three. But climate change requires a different kind of adaptation. What if, rather than trying to out-engineer the weather, or evacuate and return in an endless cycle, we changed where and how we live? It would be not an administrative feat but a psychological one, an attempt to check, in John McPhee’s words, “the powerful fabric of ambition that impelled people to build towns and cities where almost any camper would be loath to pitch a tent.”Americans aren’t good at retreating, and the ones who wound up in California, the cliché goes, are the people who didn’t stop pushing forward until they ran out of continent. The Indigenous population, though, knew a floodplain when they saw one. Is it unimaginable that we might learn that lesson as we unlearn the ones of the 20th century?
Maybe this could be California: It’s a drought year. The streams dry up. There’s barely enough water for the people and the crops and the animals, but because there aren’t too many of them, they survive. The next year it floods. The snow builds in the Sierra, storm after incredible storm, until the spring arrives and it all goes rushing out to the ocean. The people, though, live well above the rising water. The storms are intense, but after each one passes, the land around them, dun and brittle and dusty for years now, blooms with a million newborn flowers and endless gold-green grasses (emphasis added).