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<br /> <br />Flood <br /> <br />FEMA-sponsored programs, such as the CRS, require participating communities to identify repetitive loss areas. <br />A repetitive loss area is the portion of a floodplain holding structures that FEMA has identified as meeting the <br />definition of repetitive loss. Identifying repetitive loss areas helps to identify structures that are at risk but are not <br />on FEMA’s list of repetitive loss structures because no flood insurance policy was in force at the time of loss. <br /> <br />FEMA’s list of repetitive loss properties identifies 15 such properties in the San Mateo County planning area, as <br />of June 15, 2021, as summarized in Table 11-5. These properties likely were flooded by flood events typical for <br />the floodplain reflected in the current mapping. <br /> <br />Table 11-5. Repetitive Loss Properties in San Mateo County <br /> <br /> <br />Jurisdiction <br />Repetitive <br />Loss <br />Properties <br /> <br />Total Number <br />of Losses <br />Payment Made for Losses <br /> <br />Building <br /> <br />Contents <br /> <br />Total <br /> <br />Average per Claim <br />Daly City 1 4 $48,085 $47,210 $95,296 $23,824 <br />Millbrae 1 4 $49,237 $0 $49,237 $12,309 <br />Portola Valley 1 2 $384,097 $210,900 $594,997 $297,499 <br />South San Francisco 1 5 $131,107 $199,578 $330,685 $66,137 <br />San Mateo County 12 30 $540,985 $271,517 $812,502 $27,083 <br />Total 16 45 $1,153,511 $729,205 $1,882,717 $426,852 <br />Source: June 15, 2021 FEMA Repetitive Loss Summary, FEMA Region IX, Bureau Statistical Agent <br />FEMA recently changed its policies on providing repetitive loss properties information due to implications of the <br />federal Privacy Act. The “routine use” provision for acquiring the data, which requires certifications on how the <br />data will be used, was not well-defined at the time of this plan update. Repetitive loss data for all planning <br />partners could not be acquired in time for analysis and assessment for this plan. Therefore, the resolution of the <br />repetitive loss data available to support this plan update is limited to property counts only. No location or dates of <br />loss data was available. San Mateo County and its planning partners understand the importance of a thorough <br />analysis of the repetitive flood loss problem. The County and its planning partners will seek to meet FEMA <br />requirements for access to this data through plan implementation. Future updates to this plan will seek to have <br />enhanced resolution for more detailed analysis. <br /> <br />11.2.6 Frequency <br />San Mateo County has undergone 35 significant flooding events since 1996, most of which have been flash <br />floods. This correlates to a recurrence of 1, or an annual probability of occurrence of 100 percent. Smaller floods <br />may occur more frequently and be categorized under a different hazard event type, typically Severe Weather or <br />Severe Storms. Recurrence intervals and average annual numbers of events in San Mateo County were calculated <br />based on data from 1996 to 2020 in the Storm Events Database. Coastal floods have a 10 percent chance of <br />occurring in any given year, flash floods have a 55.6 percent chance, and other floods have a 40 percent chance of <br />occurrence. <br /> <br />11.2.7 Severity <br />River Flooding <br />The principal factors affecting flood damage are flood depth and velocity. The deeper and faster flood flows <br />become, the more damage they can cause. Shallow flooding with high velocities can cause as much damage as <br /> <br /> <br />11-15