The Pacific Coast and Atmospheric Rivers

As an Oklahoman, I have a profound interest in the weather, an enthusiasm shared by approximately 99.9% of Oklahomans. I have yet to meet an Oklahoman who could not talk at length about weather issues. It is not surprising, then, that my attention was drawn to an article in the January 2013 issue of Scientific American titled “The Coming Megafloods.” What surprised me is that it had a Civil War connection.

Authors Michael Dettinger and B. Lynn Ingram wrote “The intense rainstorms sweeping in from the Pacific Ocean began to pound central California on Christmas Eve in 1861 and continued virtually unabated for 43 days… The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out—six months later. By then, the state was bankrupt” (p. 66). The authors explain that the intense rains were caused by phenomena known as atmospheric rivers (“pineapple expresses” are one type of these). Sometimes these atmospheric rivers become megafloods, and these megafloods occur approximately every two hundred years along the Pacific Coast…

California soldiers were marching to Fort Yuma in Arizona during part of this time period. Here is Andrew E. Masich’s description of the ordeal from his book, The Civil War in Arizona:

“Roads became mud bogs, making the movement of men and supplies virtually impossible. Soon after [Lieutenant Colonel Joseph] West’s command reached the Colorado, the river overflowed its banks. Torrents of muddy water carved a channel around Fort Yuma, making it an island, and swept away tons of stockpiled supplies. Despite these conditions, by February 1862, ocean-going vessels and river steamers had delivered all of the expedition’s supplies, now safely stored on high ground at Fort Yuma” (p. 28). In training at Camp Wright in southern California, George Hand wrote entries such as “heavy rain,” “Very stormy,” “Very rainy,” “Rained all day and night very hard,” “Rained, snowed and the wind blew heavy” in his diary through the period.

Citation for George Hand diary: Carmony, Neil B., ed. The Civil War in Apacheland: Sergeant George Hand’s Diary: California, Arizona, West Texas, New Mexico, 1861-1864. Silver City, NM: High-Lonesome Books, 1996.