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<br />5.1 Reach Determinations <br /> <br />Reaches are defined as lengths of watercourses having relatively the <br />same flood hazard, based on the average weighted difference in <br />water-surfa~e elevations between the 10- and IOO-year floods. This <br />differen~e does not have a variation greater than that indicated in <br />the following table for more than 20 percent of the reach: <br /> <br />Average Difference Between <br />10- and 100-~~~~,F133~ <br /> <br />Variation, <br /> <br />Less than 2 feet <br /> <br />0.5 foot <br /> <br />One reach meeting the above criterion was required for the Tri-Area <br />Drainageway, the flooding source of Firestone. The location of this <br />reach is shown on the Flood Profiles (Exhibit 1). <br /> <br />5.2 Flood Hazard Factors <br /> <br />The Flood Hazard Factor (FHF) is the Federal Insurance Administration <br />device used to correlate flood information with insurance rate <br />tables. Correlations between property damage from floods and their <br />FHF are used to set actuarial insurance premium rate tables based on <br />FHFs from 005 to 200. <br /> <br />The FHF for a reach is the average weighted difference between the <br />10- and 100-year flood water-surface elevations expressed to the <br />nearest one-half foot, and shown as a three-digit code. For example, <br />if the difference between water-surface elevations of the 10- and <br />100-year floods is 0.7 foot, the FHF is 005, if the difference is <br />1.4 feet, the FHF is 015, if the difference is 5.0 feet" the FHF is <br />050. When the difference between the 10- and 100-year water-surface <br />elevations is greater than 10.0 feet, accuracy for the FHF is to the <br />nedrest foot. <br /> <br />5.3 Flood Insurance Zones <br /> <br />After the determination of reaches and their respective Flood <br />Hazard Factors, the entire incorporated area of the Town of Firestone <br />was divided into zones, each having a specific flood potential or <br />hazard. Each zone Mas assigned one of the following flood insurance <br />zone designations: <br /> <br />Zone A: <br /> <br />Special Flood Hazard Areas inundated <br />by the lOO-year flood, determined by <br />approximate methods; no base flood <br />elevations shown or Flood Hazard Fac- <br />tors determined. <br /> <br />Zone AO: <br /> <br />Special Flood Hazard Areas inundated <br />by types of lOO-year shallow flooding <br />where depths are between 1.0 and 3.0 <br /> <br />9 <br />