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11 Sea level rise is a certainty Sea level rise is occurring and is expected to accelerate throughout the 21st century. However, it is uncertain how much and how quickly sea levels will rise in the Bay Area. Considered the best available science, the National Research Council (NRC) identified likely sea level rise estimates for the west coast of the United States. 16 These values are accompanied by ranges of possible sea levels based on low and high emissions scenarios and ice melt scenarios. Figure 7 summarizes these projections: six inches of sea level rise by 2030 (range: 2-12 in), 11 inches by 2050 (range: 5-24 in), and 36 inches by 2100 (range: 17- 66 in) relative to the year 2000. Figure 7. Sea Level Rise Estimates Relative to the Year 2000 Source: NRC, 2012. 17 These projections characterize the estimated timeline for permanent increases in water levels. However, the conditions may occur sooner on a temporary basis under a number of different circumstances given the combination of permanent sea level rise and temporary extreme tides resulting from the additive impact of high tides and storm surge. For example, water levels could reach the equivalent of 48 inches of inundation by 2050 in the event of a 50-year storm, or a storm that has a two percent chance of occurring in a given year, even though that level of sea level rise is not projected to occur by the end of the century (See Appendix A, Figure A2). In the 2035 General Plan, the City of San Leandro adopted a sea level rise scenario of 55 inches by 210018 according to conservative estimates in the San Francisco Bay Conservation and Development Commission (BCDC) report Living with a Rising Bay. 19 City planning and projects in San Leandro will work to account for the threats posed by this estimate of sea level rise over the remainder of the century. In order to provide a wider lens to evaluate near and long term sea level rise relative to the established planning horizon of 55 inches, this climate hazard assessment explores the exposure of assets to sea level rise of 12 to 96 inches as presented in the Adapting to Rising Tides: Alameda County Shoreline Vulnerability Assessment, which was conducted as part of a related effort by BCDC and provides more localized sea level rise projections.20 See Appendix A for further information on the data used in this analysis. 16 National Research Council. (2012). Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. Report. DOI: 10.17226/13389 17 National Research Council. (2012). 18 City of San Leandro. (2016). San Leandro 2035 General Plan. Adopted September 19, 2016. 19 San Francisco Bay Conservation and Development Commission (BCDC). (2011). Living with a Rising Bay: Vulnerability and Adaptation in San Francisco Bay and on its Shoreline. 20 Alameda County Flood Control and Water Conservation District and the San Francisco Bay Conservation and Development Commission (BCDC). (2015). Adapting to Rising Tides: Alameda County Shoreline Vulnerability Assessment Final Report. 55