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This difference does not have a variation greater than that indicated in the following table for more than 20 percent of the reach: 10- and 100 Year F 00 s Var1a lon 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 Grand Junction are shown on the Flood Profiles (Exhibit 1) and summarized in Table 4. 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 hetween 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 Grand Junction was divided into 'zones, each having aHspec:ific flood potential or hazard. Each zone was assigned one of the following flood insurance zone designa- tions: Zone AO: Special Flood Hazard Areas inundated by types of 100-year shallow flooding where depths are between 1.0 and 3.0 feet; depths are shown, but no FHFs are determined. Zones Al, A2, and A4-A9: Special Flood Hazard Areas inundated by the 100-year flood, determined by detailed methods; base flood elevations shown, and zones subdivided according to FHFs. 23