Recent years have shown how variable California’s weather and hydrology can be. The four-year stretch of 2012 through 2015 was the driest since statewide record-keeping began in 1896. Just a year later, 2017 is on track to be among the wettest years on record, with precipitation in the northern part of the state registering more than 200 percent of normal at the end of February.
Recent months have also highlighted how quickly statewide concerns can turn from the devastating impacts of too little water during a prolonged drought, to the comparably destructive effects of too much water and resulting floods. According to the state’s Hazard Mitigation Plan, “Floods represent the second most destructive source of hazard, vulnerability and risk, both in terms of recent state history and the probability of future destruction at greater magnitudes than previously recorded.” Recent incidents of damaged spillways at Oroville Dam and breached levees in the Sacramento-San Joaquin Delta have highlighted the state’s dependence on aged flood management infrastructure. One-in-five Californians live in a flood plain, and state officials estimate that $575 billion in structures are at risk of flood damage. However, when managed appropriately, floods can bring beneficial impacts, including enhanced ecosystems, increased future water supply, and improved water quality.
This report is intended to provide basic information about floods and flood management in California. (Whereas previous generations referred to “flood control” or “flood prevention” activities, experts now prefer the term “flood management” in acknowledgement that floodwaters are recurring and inevitable.) We begin by summarizing the history, causes, and risk of floods across the state. We then describe flood management agencies, infrastructure, and strategies, as well as how governmental agencies typically respond when floods occur. Next, we describe the spending levels and funding sources currently supporting flood management efforts, as well as estimates for how much additional funding may be needed to improve those efforts. We conclude by highlighting some key challenges confronting the state in contemplating how best to manage floods in California.
Read the full report here.