It may not be in the cards this year, but California has an extended history of mega-floods the likes of which the state has not seen since 1862, when about 40 days of straight rain turned the Central Valley and much of Sacramento into a lake, killing countless people and thousands of livestock and leveling a number of barely decade-old west coast towns. Hydrology researcher Dave Reynolds argued in a 2012 paper that despite the lack of weather records for the state prior to the 1850s, the Great Flood of 1862 should be considered a 200-year event that could be expected to repeat itself with much more disastrous effects now that the west coast is so much more densely populated. But now KPIX/CBS 5 picked up on this historic flood narrative, noting that the "atmospheric river" effects we're seeing this season from the colloquially named Pineapple Express could lead to a mega-flood catastrophe sooner than we think.
They report that "Geographic data indicates California has a mega flood about every 100 to 200 years," meaning we could even be overdue for another one and the relatively minor inconveniences and small number of casualties we've seen as a result of the past six weeks' storms are negligible compared to the massive destruction the state could have in the future, climate change or not.
The USGS has modeled a scenario that they've called an ARkStorm (standing for Atmospheric River 1,000), and if you want one more thing to keep you up at night you can read the full report from 2011 right here. They estimate that economic losses could be three times what have been estimated for a major Southern California earthquake, roughly $400 billion in property losses, and business interruption costs of another $325 billion, so $725 billion total (in 2011 dollars).
The report is meant to help governments prepare for such a possibility (inevitability?), but really, how can they? The concluding statements in the abstract are enough to make you want to throw up your hands, or worse: "An ARkStorm raises serious questions about the ability of existing federal, state, and local disaster planning to handle a disaster of this magnitude... [and] innovative financing solutions are likely to be needed to avoid fiscal crisis and adequately fund response and recovery costs from a similar, real, disaster."
Ecologist John Bourgeois, who is from Louisiana, tells CBS 5 that in the Bay Area alone, about 350,000 people live in the 100-year flood plain, and they likely don't realize it.
So stop complaining about this rain, in other words. It could be much, much worse.