Flood Risk Perception in Lands “Protected” by 100-year Levees
Under the US National Flood Insurance Program, lands behind levees certiﬁedas protecting against the 100-year ﬂood are considered to be out of the ofﬁcially recognized‘‘ﬂoodplain.’’ However, such lands are still vulnerable to ﬂooding that exceeds the designcapacity of the levees—known as residual risk. In the Sacramento-San Joaquin Delta ofCalifornia, we encounter the curious situation that lands below sea level are considered not‘‘ﬂoodplain’’ and open to residential and commercial development because they are‘‘protected’’ by levees. Residents are not informed that they are at risk from ﬂoods, becauseofﬁcially they are not in the ﬂoodplain. We surveyed residents of a recently constructedsubdivision in Stockton, California, to assess their awareness of their risk of ﬂooding.Median household income in the development was $80,000, 70% of respondents had a4-year university degree or higher, and the development was ethnically mixed. Despite thelevels of education and income, they did not understand the risk of being ﬂooded. Giventhat literature shows informed individuals are more likely to take preventative measuresthan uninformed individuals, our results have important implications for ﬂood policy.Climate-change-induced sea-level rise exacerbates the problems posed by increasingurbanization and aging infrastructure, increasing the threat of catastrophic ﬂooding in theCalifornia Delta and in ﬂood-prone areas worldwide.