California Spring Flood Outlook 2021: Low, but always high in Sacramento The risk of spring flooding due to Sierra snowmelt is low but Sacramento's flood risk remains near the top in the U.S. Author: Monica Woods Updated: 6:34 PM PST March 3, 2021 SACRAMENTO, Calif. — Sacramento is typically ranked first or second in the country for the risk of flooding. The region is surrounded by the Sacramento, American and Cosumnes Rivers. The American and Sacramento Rivers have flood control measures like weirs, bypasses and Folsom Dam. The Cosumnes River is an uncontrolled and natural river running from the Sierra Nevada foothills and flowing into southern Sacramento County.