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5.0 INSURANCE APPLICATION TO establish actuarial insurance rates, data from the engineering study must be transformed into flood insurance criteria. This process includes the determination of reaches, Flood Hazard Factors, and flood insurance zone designations for each flooding source studied in detail affecting the Town of Ridgway. 5.1 Reach Determinations Reaches are defined as sections of flood plain that have relatively the same flood hazard, based on the average weighted difference in water-surface elevations 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 than 12 feet 0.5 foot 1.0 foot 2.0 feet 3.0 feet The locations of the reaches determined for the flooding sources of Ridgway are shown on the Flood Profiles (Exhibit 1) and summa- rized in Table 3. 5.2 Flood Hazard Factors The Flood Hazard Factor (FHF) is used to estabiish 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-half foot, multiplied 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; if the difference is 1.4 feet, the FHF is 015; if the difference is 5.0 feet, 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. 5.3 Flood Insurance Zones Flood insurance zones and zone numbers are assigned based on the type of flood hazard and the FHF, respectively. A unique zone number is associated with each possible FHF, and varies from 1 for a FHF of 005 to a maximum of 30 for a FHF of 200 or greater. 10