2021 Workshop

Learning from 1862: Drought and Deluge in California’s Central Valley

In 1860, William Henry Brewer was hired as the botanist for the first ever geological survey of the State of California. The Gold Rush that brought thousands out West had waned, and mining had shifted from individual fortune-seeking to corporate operations, most of which were unsuccessful. It was a time of railroad dependency, and California needed coal. Legislators recognized the necessity of accessing the overall mineral wealth of the state. Thus the first ever geological survey of California was born, the predecessor of the U.S. Geological Survey, which is still in operation today.¹The methods used by the U.S. Geological Survey at its inception in 1879 can be traced directly to those used by the California State Geological Survey. The U.S. Geological Survey’s first director, Clarence King, was part of the California State Geological Survey and worked with Brewer. William Henry Brewer, Up and Down California in 1860-1864 (New Haven: Yale University Press, 1930), xxii.

Brewer and the other men who formed the field team were mountaineers as much as scientists, climbing up and down ridges from the Central Valley to Napa County, taking frequent barometric readings, and drawing maps. Brewer also found time to write copious letters almost daily to his brother back East. Brewer shared his observations with clarity and candor; his writing is neither embellished nor reductive. Published in 1930 as Up and Down California in 1860-1864, Brewer’s letters provide a meticulous account of the Central Valley in the years preceding and following the catastrophic flood of 1862, a narrative of drought and deluge that echoes in the present day.

“I have seen no heavy rain since early last January,” Brewer wrote to his brother on October 4, 1861.²Brewer, 196. Indeed, the Central Valley was in the midst of a severe drought. Brewer described approaching teams visible only as clouds of dust, and vast plains, 60 miles wide, without a single sapling or stream. On numerous days, the expedition had only the water in their canteens. Brewer’s mules reluctantly drank alkaline runoff from mines. “I shall be glad,” he told his brother, “when we can … get a drink of good water. I assure you the last is no little item.” ³Brewer, 209.

Contemporary research shows what the Nisenans, the Native Americans living along the Sacramento River, already knew: The worst floods in history are preceded and followed by long periods of drought.⁴“Overflow Anticipated,” Nevada Democrat, vol. 9 no. 561 (January 11, 1862); Damon B. Akins and William J. Bauer, We Are the Land: A History of Native California (Berkeley: University of California Press, 2021), 123; Michael D. Dettinger, “Atmospheric Rivers as Drought Busters on the U.S. West Coast,” Journal of Hydrometeorology, vol. 14 no. 6 (December 2013): 1730. Brewer was not yet privy to this knowledge, but he did carefully observe the incipient signs of flood. He noted that there was snow not far away, on the Sierras, and for weeks leading up to the rainstorms, he reported to his brother a distinctive “stiff wind,” which brought so much dust swirling into his tent that it was better to sleep outside. ⁵Brewer, 219. When the rains finally hit, in November 1861, the Sierras’ snowcaps became a slide for water gushing down the mountains.⁶B. Lynn Ingram and Frances Malamud-Roam, The West Without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow (Berkeley, CA: University of California Press, 2015), 48. Heavy snowfall before a deluge exacerbates flood damage.

Brewer’s expedition returned to San Francisco shortly after the rain started, so that Brewer surveyed the damage from the warmth and safety of his office.⁷Brewer, 234-36. By January 1862, the entirety of the Sacramento and San Joaquin Valleys was underwater. In Brewer’s estimation, the submerged area was “250 to 300 miles long and an average of at least 20 miles wide.” Between November and January, more than 32 inches of rain fell, more than the Central Valley sees in a typical year. The rain drowned an estimated 200,000 cattle and swept away thousands of homes. The poor suffered the greatest losses. Steamers were sent to rescue civilians, and California’s capital was temporarily relocated from Sacramento to San Francisco.⁸Brewer, 242-44. It is not known how many people died, but likely thousands.⁹Michael D. Dettinger and B. Lynn Ingram, “The Coming Megafloods,” Scientific American, vol. 308, no. 1 (January 2013): 66. In reference to California’s precipitous population growth, Brewer grimly remarked, “Had this flood been delayed for ten years the disaster would have been more than doubled.”¹⁰Brewer, 245. He did not know that floods like this had happened before, and would likely happen again.¹¹Dettinger and Ingram, “The Coming Megafloods,” 67.

The water began to recede in February. Decades of mining had eroded the hillsides, so that rivers and cities were filled with sediment, and horses sunk up to their bellies in gravely mud.¹²Ingram and Malamud-Roam, The West, 53, and Brewer, Up and Down, 248. Floods play a key agricultural role by bringing nutrients to the valleys, but this flood was followed by a two-year drought, which devastated crops and starved livestock.¹³Brewer, 510. Brewer’s letters record the drought as thoroughly as they record the flood. In the spring of 1864, he visited the formerly flooded San Joaquin Valley, and noted that the soil was “fertile enough,” due to nutrient runoff, but also “destitute of water.”¹⁴Brewer, 204. Today, extensive water management systems make agriculture possible. According to the United States Geological Survey, California’s Central Valley currently produces 25 percent of the nation’s food. “California’s Central Valley,” United States Geological Survey, U.S. Department of the Interior. The blistering sun had turned the soil to dust, again.¹⁵Brewer, 507.

In modern parlance, the flood of 1862 was what is known as a “megaflood.” Megafloods are linked to the hurricane-strength winds that Brewer described, which indicate atmospheric rivers, masses of water vapor that form over the ocean when cold and warm waters collide and move inland. Weather patterns in California’s Central Valley have been studied extensively by hydrologist Michael Dettinger, whose research suggests that climate change exacerbates megafloods. Rising air temperatures cause the atmosphere to hold more water vapor, creating larger atmospheric rivers.¹⁶Dettinger and Ingram, 67. Furthermore, geographer Roger Byrne’s sediment analysis reveals that megafloods have occurred in the Sacramento Valley every 100 to 200 years since the 13th century, the most recent in 1862.¹⁷Roger Byrne and Donald Sullivan, “An 800-year Paleoflood Record from the Sacramento Valley, California,” Proceedings of the Twelfth Annual Pacific Climate (PACLIM) Workshop (Pacific Grove, CA: Interagency Ecological Program for the Sacramento-San Joaquin Estuary, 1996): 157. The scientific community warns not only that the Central Valley should expect a megaflood, but that the incipient disaster will get larger as California gets hotter.

Droughts are common and top of mind in Mediterranean regions like the Central Valley — but the drought’s twin, the deluge, is often forgotten. The inception of water-management systems gives the illusion that floods can be avoided. Yet, as recently as 2017, the Oroville Dam was at the brink of failure.¹⁸Brian Henn, et al., “Extreme Runoff Generation from Atmospheric River Driven Snowmelt During the 2017 Oroville Dam Spillways Incident,” Geophysical Research Letters, vol. 47 no. 14 (July 28, 2020): 1. Geologist B. Lynn Ingram refers to the flood of 1862 as one of California’s “lessons lost.” Too few people, she writes, are even aware of the megaflood risk.¹⁹Ingram and Malamud-Roam, 57.

Ingram’s 2015 book, The West Without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow (co-authored with Frances Malamud-Roam), warns that, in the event of heavy rains and rapid snowmelt from an atmospheric river, dams might fail.²⁰Ingram and Malamud-Roam, 216-218. The near disaster at the Oroville Dam in 2017 emerged from exactly this scenario.²¹Henn, et al., 8-9. Following a five-year drought, a record snowmelt pushed the dam to its limit. The main concrete spillway, designed to prevent overflow, cracked due to the overwhelming water pressure. Authorities were forced to engage the emergency earthen spillway, causing erosion to the hillsides. The erosion then endangered the concrete weir, the wall over which water flows to the emergency spillway; had the weir collapsed, it would have sent a 30-foot wall of water down the Feather River.²²Aristitekus Koskinas, et al., “Insights into the Oroville Dam 2017 Spillway Incident,” Geosciences, vol. 9 no. 37 (January 2019): 6. The dam did not collapse, though locals were shocked at the possibility. “Nobody thought this was going to happen,” said Jesse Hollis, a longtime Oroville resident.²³Mike McPhate and Jess Bidgood, “In Shadow of California Dam, Water Turns from Wish to Woe,” The New York Times, February 13, 2017. Ingram is right to be concerned that the megafloods of the past are “lessons lost.”

Extensive research suggests that the Central Valley is overdue for a megaflood at least as severe as that of 1862 — and likely more severe, due to climate change. This flood will almost certainly compromise dams. The key difference, however, is that the California floodplains are no longer sparsely populated. As Brewer feared, the damage could very well be “more than doubled.”

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About the Author

Lucy Wang

Lucy Wang is a Master’s candidate in Architecture in the College of Environmental Design at the University of California, Berkeley, and is Editor in Chief of Room One Thousand, Berkeley’s student-run architecture journal. She earned her B.S. in Computer Science from Stanford University and previously worked as a software engineer and UI/UX designer.