Laserfiche WebLink
<br /> <br />2021 Multijurisdictional Local Hazard Mitigation Plan <br /> <br />Time for Failure to Occur <br />The process of the dam failure affects warning time. Earthen dams do not tend to fail completely or <br />instantaneously. Once a breach is initiated, discharging water erodes the breach until either the reservoir water is <br />depleted, or the breach resists further erosion. Concrete gravity dams also tend to have a partial breach as one or <br />more monolith sections are forced apart by escaping water. The time of breach formation ranges from a few <br />minutes to a few hours. <br /> <br />8.3 EXPOSURE <br />Exposure and vulnerability to dam failure hazard were assessed by overlaying the mapped combined inundation <br />area in Figure 8-2 with planning area features including general building stock and critical facilities. Detailed <br />results by jurisdiction are included in Appendix E; countywide summaries are provided below. <br /> <br />8.3.1 Population and Property <br />Table 8-3 summarizes the estimated population living in the evaluated dam failure inundation areas and the <br />estimated property exposure. Figure 8-3 shows the structure type of buildings in the inundation area. Residential <br />properties makeup 94.6 percent of this exposure. <br /> <br />Table 8-3. Exposed Population and Property in Evaluated Dam Failure Inundation Areas <br />Population <br />Population Exposed 111,185 <br />% of Total Planning Area Population 14.4% <br />Property <br />Acres of Inundated Area 15,429 <br />Number of Buildings Exposed 26,867 <br />Value of Exposed Structures <br />Value of Exposed Contents <br />$16,136,073,660 <br />$11,261,306,886 <br />Total Exposed Property Value $27,397,380,546 <br />Total Exposed Value as % of Planning Area Total 14.3% <br /> <br />8.3.2 Critical Facilities <br />Figure 8-4 shows critical facilities located in the dam failure inundation zone by facility type. The total count of <br />critical facilities in the dam failure inundation zone (299) represents 13.4 percent of the planning area total of <br />2,236. Exposed critical facilities include the following major roads: <br /> State Highway 1 (Pacific Coast <br />Highway) <br /> State Highway 82 (El Camino Real) <br /> State Highway 84 (Woodside Road) <br /> State Highway 92 <br /> State Highway 109 (University <br />Avenue, East Palo Alto) <br /> State Highway 114 (Willow Road, <br />Menlo Park) <br /> US Highway <br />101 <br /> Interstate 280 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />8-8