Abstract
Levee systems are an important part of California’s water infrastructure, engineered to provide resilience against flooding and reduce flood losses. The growth in California is partly associated with costly infrastructure developments that led to population expansion in the levee protected areas. Therefore, potential changes in the flood hazard could have significant socioeconomic consequences over levee protected areas, especially in the face of a changing climate. In this study, we examine the possible impacts of a warming climate on flood hazard over levee protected land in California. We use gridded maximum daily runoff from global circulation models (GCMs) that represent a wide range of variability among the climate projections, and are recommended by the California’s Fourth Climate Change Assessment Report, to investigate possible climate-induced changes. We also quantify the exposure of several critical infrastructure protected by the levee systems (e.g. roads, electric power transmission lines, natural gas pipelines, petroleum pipelines, and railroads) to flooding. Our results provide a detailed picture of change in flood risk for different levees and the potential societal consequences (e.g. exposure of people and critical infrastructure). Levee systems in the northern part of the Central Valley and coastal counties of Southern California are likely to observe the highest increase in flood hazard relative to the past. The most evident change is projected for the northern region of the Central Valley, including Butte, Glenn, Yuba, Sutter, Sacramento, and San Joaquin counties. In the leveed regions of these counties, based on the model simulations of the future, the historical 100-year runoff can potentially increase up to threefold under RCP8.5. We argue that levee operation and maintenance along with emergency preparation plans should take into account the changes in frequencies and intensities of flood hazard in a changing climate to ensure safety of levee systems and their protected infrastructure.
Highlights
Levees are crucial water infrastructure systems that are engineered to provide resilience against flooding events
We first quantify the length of roads, electric power transmission conductors, natural gas pipelines, petroleum pipelines, and railroads that are protected by each of the Californian levee systems using the National Levee Database (NLD) and critical infrastructure datasets
The CanESM2 model, which is projected to be associated with an average climate condition for the state of California in the future, shows that other than levee systems located in the southern part of the Central Valley with up to 68% projected decrease in the flood hazard, all the levee systems will likely experience a higher flood hazard up to a threefold increase by the end of this century (figure 2(A))
Summary
Levees are crucial water infrastructure systems that are engineered to provide resilience against flooding events. A majority of levees in the United States and in particular in California are earthen systems that were built in the previous century based on the stationary assumption with data records of the time (Remo et al 2009, Dierauer et al 2012, Salas and Obeysekera 2014, Vahedifard et al 2015, 2016, ASCE 2017). Numerous studies in recent years contradicted with the stationary assumption and showed that changes in climate are anticipated to alter the characteristics of flooding events (e.g. Barnett et al 2005, Kundzewicz et al 2014, Mallakpour and Villarini 2015, Asarian and Walker 2016, Asadieh and Krakauer 2017, Ehsani et al 2017, Najibi et al 2017). For coastal southern California, (Feng et al 2019) projected that 100-year flood magnitude could increase up to 185% due to global warming
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