Sacramento underwater due to floods in an 1862 rendering that ran in local papers.

Sacramento underwater due to floods in an 1862 rendering that ran in local papers.

Californians are always talking about the coming Big One, but what if the big one is a flood, not an earthquake?

With this recent cavalcade of rainstorms, there’s been renewed interest in a 2011 USGS study on the so-called “ARkStorm.” In it, the USGS lays out a case for a hypothetical “megastorm,” one that could cause up to $725 billion in damage and impact a quarter of California’s homes.

The ARkStorm would bring with it catastrophic rains, hurricane-force winds and hundreds of landslides. Central Valley flooding alone is projected to span 300 miles.

If that sounds far-fetched, there’s historic precedent: Geological evidence indicates that California endures massive flooding caused by atmospheric rivers every 100-200 years. And settlers who moved to California after the Gold Rush soon found what the native population had known for centuries: Northern California is prime flooding territory.

The most prominent example is the Great Flood of 1862, a natural disaster that still ranks as the largest flood in the history of the American West. Between Dec. 1861 and Jan. 1862, the West Coast received a near-constant deluge of rain. Sacramento received a stunning 23 inches in that period, turning the city into a watery ghost town.

“The people are leaving the city as rats would a sinking ship” the Red Bluff Independent wrote on Jan. 14.

As flood waters rose, it took entire houses with it. Little two-story wooden houses were carried off whole and eyewitness reports in the local papers said the flowing waters were full of furniture and dead livestock. Thirty foot-tall telegraph poles, which had recently been installed between New York and San Francisco, were fully submerged.

That was hardly the worst of it. A Tuolumne County paper reported that 1,400 Chinese migrants died in the flooding state-wide. One-third of the property in the state was destroyed and 800,000 cattle died, a mass die-off that marked “the beginning of the end of the cattle-based ranchero society in California.”

Settlers realized the homes that survived had something in common: They were built in the spots where Native Americans originally put down settlements. Native stories spoke of the Sacramento Valley as an inland sea. For centuries, they’d seen the valley fill with water, and the Nevada City Democrat reported that “Indians living in the vicinity of Marysville left their abodes a week or more ago for the foothills predicting an unprecedented overflow. ”

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SOURCE: Katie Dowd
San Francisco Chronicle