Opinion: Why rain-on-snow floods from atmospheric rivers could get much worse
California’s latest atmospheric rivers are sending rainfall higher into the mountains and onto the state’s crucial snowpack. The rain alone is a problem for low-lying areas already dealing with destructive flooding, but the prospect of rain on the deep mountain snow has triggered widespread flood warnings. When rain falls on snow, it creates complex flood risks that are hard to forecast. Those risks are also rising with climate change. For much of the United States, storms with heavy rainfall can coincide with seasonal snow cover. When that happens, the resulting runoff of water can be much greater than what is produced from rain or snowmelt alone. The combination has resulted in some of the nation’s most destructive and costly floods, including the 1996 Midwest floods and the 2017 flood that damaged California’s Oroville Dam.
-Written by Keith Musselman, an assistant professor in geography, mountain hydrology and climate change at the University of Colorado Boulder.