As the world warms and precipitation that would have generated snowpack instead creates rain, the western U.S. could see larger floods, according to new Stanford research.
An analysis of over 400 watersheds from 1980 to 2016 shows that winter floods driven by rainfall can be more than 2.5 times as large as those driven by snowmelt. The researchers also found that flood sizes increase exponentially as a higher fraction of precipitation falls as rain, meaning the size of floods increased at a faster rate than the increase in rain.
The study, which appears in the January issue of Water Resources Research, is particularly salient for people planning infrastructure while taking global warming into account. As Northern Californians saw during the Oroville Dam crisis in 2017 when a spillway failure forced more than 180,000 residents to evacuate, warm storms can pose big problems.
“The Oroville Dam crisis is a good example of how existing infrastructure is already vulnerable to flooding,” said lead author Frances Davenport, a PhD student in Earth system science at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “These results show that warming alone – even without changes in precipitation amounts – could lead to changes in the size of floods.”
Read more at Stanford University
Image: Water overflowing the auxillary spillway of Oroville Dam, CA. CREDIT: William Croyle, California Department of Water Resources