Blog: Dam-failure flood risk in California: how to manage low-probability hazards
Every year, damaging floods strike somewhere around the world, including sometimes in California like during winter 2022-23. Even a house with just a 1% chance of flooding each year (by the so-called “100-year flood”) has a 26% chance of inundation over a 30-year mortgage. Other natural hazards have much lower probabilities, but would bring more catastrophic consequences. These threats are much more challenging to plan for; dam failure and associated flooding is one such hazard. Over the past 100+ years, California has built over 1200 dams, which impound ~42 million of acre-feet of water statewide. The probability of a dam failing in any one year is very small but no dam is “failure-proof.” While California hasn’t suffered a catastrophic dam disaster in recent history, the 1928 failure of St. Francis dam killed over 400 people. And the failure of the Oroville Dam spillway in 2017 caused the evacuation of more than 180,000 people and was a harsh reminder of the importance of dam inspections and maintenance.