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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 Collbran are shown on the Flood Profiles (Exhibit 1) and sum- marized in Table 3. 5.2 Flood Hazard Factors The FHF is the Federal Emergency Management Agency device used to correlate flood information with insurance rate tables. Correla- tions between property damage from floods and their FHF are used to set actuarial insurance premium rate tables based on FHFs from 005 to 200. The FHF for a reach is the average weighted difference between the 10- and 100-year flood water-surface elevations expressed to the nearest one-half foot, 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 water-surface elevations is greater than 10.0 feet, accuracy for the FHF is to the nearest foot. 5.3 Flood Insurance Zones After the determination of reaches and their respective FHFs, the entire incorporated area of Collbran was divided into zones, each having a specific flood potential or hazard. Each zone was assigned one of the following flood insurance zone designations: Zone A: Special Flood Hazard Areas inundated by the lOa-year flood, determined by approximate methods; no base flood elevations shown or FHFs determined. Zones AI, A2, and A3: Special Flood Hazard Areas inundated by the lOa-year flood, determined by detailed methods: base flood elevations shown, and zones subdivided according to FHFs. Zone B: Areas between the Special Flood Hazard Areas and the limits of the SOD-year flood, including areas of the 500-year 13