The Great Flood of California (1862)

In the winter of 1861-62, rain across the West created the worst flooding in the history of California, Oregon, and Nevada, killing thousands, more than 1% of the population at the time, and bankrupting the state. A 300-mile stretch of California’s Central Valley, the center of its agriculture, was covered thirty feet deep in water. Yet most Californian’s have never heard of it. (The Big Ones, L. Jones, 2018).

Unfortunately, due to climate change, storms of this magnitude will become more frequent and intense. To prepare communities the USGS developed a simulation, ARkStorm, to address these massive storms (Figure 9.18). Experts from scientific research agencies were assembled and tasked with designing a large, but scientifically plausible, hypothetical storm scenario that hit both northern and southern California. The wind, precipitation, flooding, and coastal hazards were translated into physical, environmental, social, and economic damages to provide emergency responders, resource managers, and the public a realistic assessment of what is historically possible.

Map of California with areas in blue signifying the major flood event of 1862. — **Figure 9.18:** A diagram of the flood areas of the December 1861-January 1862 California Megastorm. These same areas are expected to flood again if another megastorm were to impact California. (Public Domain, USGS)

Want to know more about the Great Flood and ARkStorm? Consider reading,

- Mother Jones: The Biblical Flood That Will Drown California (2020)
- Scientific American: The Coming Megafloods (2013)