The only megaflood to strike the American West in recent history occurred during the winter of 1861-62. This disaster turned enormous regions of the state into inland seas for months, and took thousands of human lives. The costs were devastating: one quarter of California’s economy was destroyed, forcing the state into bankruptcy.
Sixty-six inches of rain fell in Los Angeles that year, more than four times the normal annual amount, causing rivers to surge over their banks, spreading muddy water for miles across the arid landscape. Large brown lakes formed on the normally dry plains between Los Angeles and the Pacific Ocean, even covering vast areas of the Mojave Desert. In and around Anaheim, , flooding of the Santa Ana River created an inland sea four feet deep, stretching up to four miles from the river and lasting four weeks.
In early December, the Sierra Nevada experienced a series of cold arctic storms that dumped 10 to 15 feet of snow, and these were soon followed by warm atmospheric rivers storms. The series of warm storms swelled the rivers in the Sierra Nevada range so that they became raging torrents, sweeping away entire communities and mining settlements in the foothills—California’s famous “Gold Country.” A January 15, 1862, report from the Nelson Point Correspondence described the scene: “On Friday last, we were visited by the most destructive and devastating flood that has ever been the lot of ‘white’ men to see in this part of the country. Feather River reached the height of 9 feet more than was ever known by the ‘oldest inhabitant,’ carrying away bridges, camps, stores, saloon, restaurant, and much real-estate.” Drowning deaths occurred every day on the Feather, Yuba and American rivers. In one tragic account, an entire settlement of Chinese miners was drowned by floods on the Yuba River.
In an interesting echo of that event, I work with a guy whose office is in an old victorian in downtown Marysville - one of the cities recently evacuated. The building was built originally by a Chilean Don who had made his fortune from the gold rush. My acquaintance bought it, turned it into an office for his business, and noted to me during one of my visits that there was a basement billiard room that was still filled to the ceiling with mud from this flood! No one had ever bothered to do the work of shoveling it out. I offered my digging services no charge, but I told him I got to keep any artifacts, dead bodies or GOLD that I found. He didn't take me up on my generous proposal.