10A Action Items 2018 1105 - Laserfiche WebLink

Home

69 Periodically, the Working Group on California Earthquake Probabilities (a collaborative effort of the U.S. Geological Survey, the California Geological Society, and the Southern California Earthquake Center) report a significant chance that one or more quakes of magnitude 6.7 or larger will occur in the Bay Area in this century. Such earthquakes may be very destructive. The U.S.G.S. predicts a magnitude 7 earthquake occurring today on the Hayward Fault, would likely cause hundreds of deaths and approximately $100 billion of damage. Property within the City could sustain extensive damage in a major earthquake, and a major earthquake could adversely affect the area’s economic activity. Flood. Flood hazards in the City are associated with overbank flooding of creeks and drainage canals, dam failure, tsunamis, and rising sea level. During the last 40 years, urbanization in the watersheds has increased impervious surface area, which has resulted in faster rates of runoff and higher volumes of storm water in the channels. Maps published by the Federal Emergency Management Agency indicate that a 100–year storm (e.g., a storm that has a 1% chance of occurring in any given year) could cause shallow flooding in parts of southwest San Leandro. The City’s Floodplain Management Ordinance requires that new construction, additions and major home improvement projects are raised at least one foot above the base flood elevation. The City is also working with the Alameda County Flood Control and Water Conservation City to increase the carrying capacity of flood control channels. Measures being pursued include redesign of the channels, replacing undersized culverts, and keeping the channels well–maintained and free of debris. Most of the City would be flooded in the event of dam failure at the Lake Chabot or Upper San Leandro Reservoirs, which reservoirs are owned, maintained and operated by the East Bay Municipal Utility District. Such a flood could produce catastrophic damage and casualties in the City. The dams at both reservoirs have been seismically strengthened during the last 30 years, although the risk of failure remains. Wildfire. The area of the City east of Interstate 580 is classified as a “moderate” fire hazard by the California Department of Forestry. The lack of a dense tree canopy is a mitigating factor as are the relatively wide streets, gentle slopes and grassland vegetation. Nevertheless, the City lies adjacent to thousands of acres of potentially flammable coastal scrub and forested open space. There are also a number of locations in the City, particularly along San Leandro Creek, with large eucalyptus trees and other highly flammable vegetation and combustible litter. The Uniform Fire Code specifies fire mitigation requirements that are enforced by the City’s Building Division. The City also requires fire–resistant roofing materials in new construction and major remodeling projects. Despite these requirements, the risk of damage from wildfire remains. Tsunami. Tsunamis are long–period waves usually caused by off–shore earthquakes or landslides. Because the San Leandro shoreline does not face the open ocean, the City believes that its risk of experiencing a tsunami is very low. A 100–year frequency tsunami would generate a wave run–up of 4.4 feet at the San Leandro shoreline. Most of the shoreline is protected by rip–rap (boulders) and would not be seriously affected. Sea Level Rise/Climate Change. Within the City, certain property may be vulnerable to property damage or reductions in assessed value as a result of future sea level rise in the San Francisco Bay or other negative impacts resulting from climate change.