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5.1 Reach Determinations Reaches are defined as lengths of watercourses having relatively the same flood hazard, based on the average weighted difference in water-surface elevations between the 10- and 100-year floods. This difference does not have a variation greater than that indicated in the following table for more than 20 percent of the re~ch. Average Difference Between 10- and 100-year Floods variation Less than 2 feet 2 to 7 feet 7.1 to 12 feet 0.5 foot 1.0 foot 3.0 feet Twenty reaches meeting the above criteria were required for the flooding sources of Littleton. The location of the reaches are shown on the Flood Profiles (Exhibit 1). 5.2 Flood Hazard Factors The Flood Hazard Factor (FHF) is the Federal Insurance Administration device used to correlate flood information with insurance rate tables. Correlations 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 eleva- tions expressed to the nearest one-half foot, and shown as a three-digit code. For example, i~the difference between water-surface elevations of the 10-year 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-year and lOb-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 Flood Hazard Factors, the entire incorporated area of Littleton was divided into zones, each having a specific flood potential or hazard. Each zone was assigned one of the following flood insurance zone designations: . ~ 26