Flooding in Santa Ana, California, in 1969. Photo courtesy Orange County Archives.
As Californians suffer through one of their worst droughts since the state joined the Union, it seems cruel to ponder the devastation that might afflict them if this winter’s rainy season happens to go overboard.
But government planners and emergency managers are paid to prepare themselves - and to prepare us - for the worst. So let’s consider the ARkStorm.
The ARkStorm is a fictional, or more accurately a hypothetical, event that was conjured a few years ago as part of an exercise the U.S. Geological Survey conducted. It asked what would happen if two of the worst rainstorms in the state’s modern history - one from January 1969, the other from February 1986 - chanced to occur back to back.
As you would expect, the answer to that question is “nothing good.” Well, almost nothing. California’s badly depleted reservoirs would certainly be refilled if the ARkStorm were to strike while the current drought’s effects were still fresh. The extra storage capacity now available in those reservoirs would, at least in some cases, mitigate the inevitable flooding. But the ARkStorm would still be a highly unpleasant experience.
On the assumption that the storm would occur in normal conditions, rather than following an antecedent drought, the USGS study anticipated flooding in nearly every corner of California, with the worst effects in the Central Valley but substantial damage also in southern California, from Los Angeles to San Diego, in the Bay Area and in other coastal and mountain locales. Total property damage, mainly from flooding, would approach $400 billion, of which scarcely more than 5 percent would be covered by insurance. Winds in some coastal locations could gust to 125 miles per hour. As many as 1.5 million Californians might be driven from their homes.
It sounds like the script of a Hollywood disaster film, but the ARkStorm scenario does not require us to believe that a cyclone of unprecedented strength or highly atypical course would blow in from the Pacific Ocean. There would be no mega-hurricane, no man-hunting twister registering F5 on the Fujita scale. Instead, an “atmospheric ribbon” (the “AR” in ARkStorm) of moist tropical or subtropical air would be carried into California on a series of more or less ordinary weather fronts, dumping rain at low elevations and even more rain in the mountains, where the mild air would raise freezing levels and cause early season snows to melt and contribute more runoff.
This ribbon of moist air is such a common feature on the West Coast that it has a widely known nickname, the “Pineapple Express.” The only statistically unusual characteristics in the ARkStorm scenario would be its intensity and its duration. The government scientists who modeled the ARkStorm estimate that this sort of rainmaker strikes California every 100 to 200 years, making it what chief researcher Lucy Jones called “not an extremely extreme” event.
In fact, the ARkStorm has been compared to the great California flood of 1861-62, which devastated the nascent city of Sacramento and turned much of the Central Valley into a vast inland sea. That winter, rain began falling across much of California around Nov. 8 and continued more or less without letup for some six weeks. A dispatch in The New York Times estimated the damage at around $10 million at the time, or around $230 million in today’s terms. Not too bad, until you consider that the state at that time consisted entirely of small frontier settlements, mining camps, old Spanish missions and untouched wilderness.
The point of a thought exercise like ARkStorm is to help us to better prepare. But how, exactly, would we rationally prepare for a once-in-several-lifetimes event like ARkStorm? The study’s authors talk about hardening infrastructure and taking other costly mitigation steps now, to avoid paying far more costly recovery and rebuilding costs later.
That advice makes sense when the question of preparing for an ARkStorm-level flood is considered in isolation. But life’s events, and the financial investments we make to prepare for them, do not happen in isolation. How much money should California, or the country, divert from public schools or first responders to prepare for ARkStorm? How much from the prevention, containment and mitigation of wildfires or earthquakes, both of which are far more common in the Golden State than massive floods? How much from transportation infrastructure (Hint: They could take every dollar from California’s bullet train project without hurting anyone), or restoring the state’s grossly abused rivers?
These questions don’t have right or wrong answers; they are judgmental, and thus inherently political rather than empirical. I do not fault USGS and collaborating scientists for developing the ARkStorm scenario, or for monitoring it and publicizing it. They contributed valuable information to the public discussion. Yet until an ARkStorm hits, hardly anyone will pay attention to the prospect, if only because nobody alive has ever seen one.
Probably the best chance of doing something to protect against an ARkStorm’s ravages is to do something that is not about ARkStorm at all - like building dams and reservoirs to increase California’s water storage, and aqueducts to move more water from where it falls to where it can be productively consumed. These facilities would come in very handy amid the drought searing the state at the moment, and they would also be valuable when and if the rains return more enthusiastically than Californians might wish.
Unfortunately, this is not a dam-building era. While a few existing structures might conceivably be upgraded, it is hard to even imagine a new reservoir of any significant size getting approved in California (or most other American states) today, let alone getting built before the next ARkStorm comes along.
This is probably a good time to get a great deal on a small boat in California, however. There are not many places where you can use one right now. But if you keep it in your garage, you might be glad to have it next time you have to row to a grocery store.