Reso 2025-151 Environmental Hazards Element General Plan

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S A N L E A N D R O G E N E R A L P L A N E N V I R O N M E N T A L H A Z A R D S 7-14 Rising Sea Level. Global sea level has been rising as a result of melting sea ice and thermal expansion of the ocean. The rate has been accelerating, with multiple sources indicating a potential rise of 55 inches by Year 2100. Projections are consistent with best available science, which currently are published in the 2024 State of California Sea Level Rise Guidance prepared by the Ocean Protection Council (OPC), and state guidance modeled through Adapting to Rising Tides Shoreline Flood Explorer. This poses a number of risks to western San Leandro, including increased incidences of flooding from King Tides, storm surges, and runoff from creeks and flood control channels. Development in vulnerable areas must be planned and designed to be elevated above future projected coastal flood levels. There is also a need to make existing development along the shoreline more resilient, either by adapting structures to recognize the potential for future flooding or by constructing flood protection devices along the shoreline. Presently, sea level rise risk assessments are required for projects in areas where the long-term risk of coastal flooding is present. Such assessments will need to address the likelihood of flooding and the need for shoreline improvements such as levees and seawalls. The City itself will need to engage in adaptation planning to protect public and private property in vulnerable areas. Facilities that have been identified as located within projected sea level rise risk zones include Stenzel Park, Marina Community Center, the Mulford Marina Branch library, Bonaire Park, Marina Park, and the Water Pollution Control Plan. Approximately 13 percent of San Leandro residents currently reside in projected end-of-century sea level rise inundation zones. Figure 7-4 depicts mid-century sea level rise of 0.9 feet and an end-century sea level rise of 4.4 feet, which represents the Intermediate-High sea level rise projection for the Alameda tide gauge, as published in the 2024 State of California Sea Level Rise Guidance. Large areas are shown to be under water by mid- and end-century. Figures 7-5 and 7-6 show rising groundwater levels, which is a secondary potential impact of sea level rise. This impact occurs when the rising Bay water level forces groundwater up toward the surface of the ground. This can present flood complications, stressed pipes, affect roadbeds, amplify the potential for liquefaction, disrupt structural foundations and basements, and stress septic systems. Figure 7-5 presents the depth of groundwater in San Leandro by mid-century while Figure 7-6 presents end-century risk. Resolution No. 2025-151 Exhibit A 14 of 84