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2.2 HAZARD DESCRIPTIONS This section summarizes the hazard conditions that may reasonably occur in Redwood City and would potentially require response by City public safety and other staff and activation of the City's ECIC. More detailed hazards descriptions are contained in the City's General Plan Public Health and Safety Element, the 2015 Flood Response Annex and the Local Hazard Mitigation Plan. '.2.1 FLOODINr Flooding occurs when water builds up in normally dry areas because it cannot drain away or be absorbed into the soil fast enough. Floodwaters may move or they may be stationary (an effect called ponding), but both can be dangerous and may require emergency response. Floods typically happen as a result of heavy precipitation, but they can also be caused by breaks in water infrastructure (such as reservoirs or levees) or in the case of coastal areas, particularly strong tides. Floodwaters can damage or destroy buildings and structures, injure or kill people caught in the water, and block transportation networks with water or debris. In the City, floods are most common during the winter rainy season. The areas at greatest risk of flood (known as the 100 -year flood plain, which has a statistical one percent chance of flooding in any given year) are the bay islands and marshes in northern Redwood City, as well as some waterfront areas north of US Route 101. Areas at a lower but still elevated risk (the 500 -year flood plain, where there is a 0.2 percent chance, or a 1 in 500, of flooding in any given year) include large sections of downtown, the area north of Bay Road, and the Jefferson Avenue and Roosevelt Avenue corridors near Cordilleras Creek. The Redwood Shores neighborhood is also in the 500 -year flood plain, although it is protected by levees that help reduce the flood risk. Flood events have occurred several times in the City's history. Floods in the winter of 2014-2015 and 2016- 2017 caused flooding in northern Redwood City and resulted in damage to multiple mobile homes. Several other floods were reported in February 1986, January 1982, February 1963, March 1962, April 1958, December 1955, and February 1954. Severe storms have also caused minor flooding throughout the community. In the future, climate change may alter the location of flood prone areas and increase the frequency and/or intensity of major storm events, which could increase the risk of flood events. 2.2.2 HAZARDOUS MATERIALS INCIDENT Hazardous materials cover a wide range of substances, including those that are toxic, flammable, corrosive, explosive, radioactive, or infectious. Due to the risk posed by these substances, they are often stored in special containers in controlled environments. When a sufficient quantity of these materials escapes into the environment, people may be accidentally exposed to these substances and suffer negative effects. A release of hazardous materials large enough to pose a human or environmental health risk is known as a hazardous materials incident. Despite the danger of hazardous materials, they are widely used in homes and businesses. Hazardous materials may include common cleaning supplies, medical and biological wastes, industrial chemicals, and substances used in commercial services such as photography, dry cleaning, printing, and automotive repair. Numerous locations throughout Redwood City have hazardous materials on site, although only 10