FLOOD11732 - Laserfiche WebLink

Home Browse Search

5.0 INSURANCE APPLICATION To establish actuarial Insurance rates, data from the engineering study must be transformed i~to flood insuran~e criteria. This process includes the determination of reaches, Flood Hazard Factors, and flood insurance zone designations for each flooding source studied by detailed methods affecting the City of Boulder. or 5.1 Reach Determinations ~ Reaches are defined as sections of floodplain that have relatively the same flood hazard. In riverine areas, reaches are based on the averagE! weighted difference in water-surface elevat ions between the 10- and 100-year floods. This difference may not have a variation greater than that indicated in the following table for more than 20 percent of the reach: Average Difference Between 10- and 100-Year Floods Variation Less than 2 feet 2 to 7 feet 7.1 to 12 feet More ~han 12 feet 0.5 foot 1.0 foot 2.0 feet 3.0 feet The locations of the reaches determined for the riverine flooding sources of Bouldel;' are shown on the Flood Profiles (Exhibit 1), and the reaches aie summarized In Table 4. 5.2 Flood Hazard Factors The Flood Hazard Factor (FHF) IS used to establish relationships between depth and frequency of flooding in any reach. This rela- tionship is then used with depth-damage relationships for various classes of structures to establish actuarial insurance rate tables. .. The FHF for a reach is the average weighted difference between the 10- and 100-year flood water-surface elevations rounded to the nearest one-ha 1 f foot, mul t iplied by 10, and shown as a three- digit code. For .example, if the difference between water-surface elevations of the 10- and 100-year floods is 0.7 foot, the FHF is 005; it the difference is 1.4 feet, tne FHF is 015; if the differ- pnce is 5.0 fect, the FHF is 050. When the difference between the 10-and 100-year flood water-surface elevations is greater than 10.0 feet, it is rounded to the nearest whole foot. / 27