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<br />25 <br />Figure A1. Sea Level Rise Estimates Relative to the Year 2000 <br /> <br />Source: NRC. 2012. 46 <br />In the report Adapting to Rising Tides: Alameda County Shoreline Vulnerability Assessment, these <br />projections inform a sea level rise analysis for Alameda County. Four inundation maps were created <br />which incorporate remote sensing data using light detection and ranging (LiDAR) methods to depict the <br />elevation on natural and hard structures and determine the level of “overtopping” at five-meter <br />resolution. Each map represents a range of scenarios that are possible given different combinations of <br />sea level rise and extreme tides. Extreme tides are caused by the additive impact of unusually high tides, <br />or King tides, which happen twice per year, and storm surge, which results from the high winds and low <br />atmospheric pressure associated with storm conditions. <br />The analysis includes maps of water levels increasing by 12 inches, 24 inches, 36 inches and 48 inches <br />over the Mean Higher High Water (MHHW), or the average height of the higher high tide of each day. <br />(Refer to Figure A2.) Based on the likely sea level rise projections within climate scenarios, the areas <br />flooded in the map depicting 36 inches of sea level rise are likely to be permanently inundated by 2100. <br />However, this same water level could occur temporarily on an annual basis by mid-century with high <br />tides and storm surge. <br />Two additional maps of water level increases at 72 and 96 inches illustrate flooding that can potentially <br />take place under the circumstances that sea level rise is combined with higher than projected glacial <br />melt and extreme tides. For example, a 72-inch scale flood is possible with 36 inches of sea level rise and <br />a 50-year extreme tide. A 95-inch scale flood, which would inundate half the city, is possible with 54 <br />inches of sea level rise and a 100-year storm event. <br /> <br /> <br />46 National Research Council. (2012). Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and <br />Future. Report. DOI: 10.17226/13389 <br />69