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97 <br /> <br />5.7 LEVEE FAILURE <br />The Sacramento-San Joaquin River Delta and Suisun Marsh are vitally important to <br />the Bay Area economy and environment and contain many levees. The Delta region <br />contains critical infrastructure including pipelines, highways, and power and <br />communication lines. The Delta is the hub of the California water system, providing <br />water to 25 million people in the State and 3 million acres of farmland.8 The <br />probability of levee failure is increasing over time due to sea level rise, increased <br />flooding potential due to early winter snow melts, and the likelihood of an <br />earthquake. <br /> <br />An earthquake is the single biggest risk the Delta Region faces. If an earthquake <br />occurs, levees may fail and as many as 20 or more islands could be flooded <br />instantaneously. This would result in an economic impact of $15 billion or more. <br />While local Delta faults contribute most significantly to the hazard at longer return <br />periods, and will produce stronger shaking due to their proximity to the levees, the <br />major Bay Area faults pose a greater risk to the Delta levees. While they are farther <br />away and will produce smaller ground motions at Delta sites, earthquakes occur <br />much more frequently on these faults. The Hayward fault, in particular, is the greatest <br />concern for the Bay Area. It is capable of producing large earthquakes that will be <br />devastating to the Bay Area and is close enough to the Delta to damage levees. Other <br />Bay Area faults, such as the Concord and Green Valley, are also likely to produce <br />earthquakes that will damage Delta levees. Additionally, the soils in the western delta <br />are extremely weak and liquefaction will trigger at even low levels of shaking. <br /> <br />PAST OCCURANCE AND POTENTIAL FOR OCCURANCE <br />San Leandro does not have any levees due to land adjacent to the bay lying above sea <br />level. San Leandro’s shoreline has been armored with rip rap to ensure that bay water <br />does not erode away the shoreline. <br /> <br /> <br />8 ABAG, (2010) <br />8 ACFC website <br /> <br /> <br />136