Laserfiche WebLink
<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-surface elevations between thG 10- and 100-year floods. This <br />difference 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-year Floods <br /> <br />Variation <br /> <br />Less than 2 feet <br />2 to 7 feet <br /> <br />0.5 foot <br />1. 0 foot <br /> <br />Five reaches meeting the above criteria were required for the flooding <br />sources of the Town of Silverton and the designated unincorporated <br />areas of San Juan County. These included one reach each on the <br />Animas River and Mineral Creek and three on Cement Creek. The <br />locations of the reaches are 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 laO-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 />lOa-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 />nearest 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 Silverton, <br />and the designated unincorporated areas of San Juan County were <br />divided into zones, each having a specific flood potential or <br />hazard. Each zone was assigned one of the following flood insurance <br />zone designations: <br /> <br />Zone A: <br /> <br />Special Flood Hazard Areas inundated by <br />the IOO-year flood, determined by <br />approximate methods; no base flood <br />elevations shown or Flood Hazard Factors <br />determined. <br /> <br />18 <br />