Summary/Abstract
Although California is currently experiencing drought and wildfire conditions, paleoclimate and historical records show that it is a region subject to infrequent but intense flooding. This study uses climate modeling to provide evidence that changes to precipitation patterns, water moisture content, temperature, and snowmelt increase both the risk and potential intensity of extreme flooding events in California. Climate change has doubled the likelihood of an extreme flooding event, and runoff in the future extreme storm scenario is likely to be 200 to 400% greater because of increased precipitation rates and decreased snow friction. These potential flooding events may actually compound the risk posed by wildfires if runoff from flash-flooding transports debris left by wildfires. A severe flood would cause extreme threats to public safety, livelihoods, crops, and most economic industries.