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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Hydraulic Analnis <br /> <br />Delineation of the IOQ.year floodplain within Hinsdale County for ponions of Lake Fork <br />and Henson Creek in the vicioity of Lake City used the HEC-2 (USACE, 1991) hydraulic <br />model and ""'ere presented on the FIRM. Approximate floodplains along portions of Lake <br />Fork, Henson Creek, Cebolla Creek, Mineral Creek. Spring Creek, North Clear Creek. <br />South Clear Creek, Rito Hondo Creek. Big Spring Creek. Crooked Creck, Rio Grande <br />River. Little Squaw Creek, Squaw Creek, Weminuche Creek, Los Pinos River, Middle <br />Fork Piedra River. East Fork Piedra River, Piedra River, Williams Creek. and <br />Weminuche River. a few unnamed tributaries. and numerous reservoirs and lakes were <br />also presented on the FIRM. The FIRM's are shown on Figures 3A through 3P. The <br />approximate floodplains are shown for planning purposes only. and development or <br />construction in the area of approximate floodplains should be studied by detailed <br />topographic and hydraulic analysis. <br /> <br />Floodplain l\lappine: <br /> <br />The IOO-year floodplains for portions of Lake Fork and Henson Creek in the vicinity of <br />Lake City sho\\1l on Figures 4A through 4G within Hinsdale County are based on <br />detailed technical methods. Additional infonnation including summary tables of base <br />flood elevations for Lake Fork and Henson Creek may be found in the Floodplain <br />Information Report (WestWater, 1985a and 1985b). <br /> <br />Approximate floodplains for portions of Lake Fork, Henson Creek. Cebolla Creek, <br />Mineral Creek, Spring Creek, North Clear Creek, South Clcar Creek, Rito Hondo Creek, <br />Big Spring Creek, Crooked Creek, Rio Grande River, Little Squaw Creek. Squaw Creek, <br />Weminuche Creek, Los Pinos River, Middle Fork Piedra River. East Fork Piedra River, <br />Piedra River. Williams Creek, and Weminuche River, a few unnamed tributaries, and <br />numerous reservoirs and lakes were presented on the FIRM are also shown on Figures 4A <br />through 40. Approximate floodplains are shown for these areas because thcse reaches <br />have not been studied with sufficient technical detail to be used for floodplain delineation <br />with any certainty. FEMA requires a detailed floodplain analysis for development <br />projects greater than 5 acres in area or more than 50 units in size in approximate <br />floodplains be performed by a professional engineer. <br /> <br />Vertical datum for the FIRM and FIS is NGVD 1929. To conven to the most recent <br />standard, NAVD 1988, add between 4.76 to 6.52 feet to all elevations (USCOE, 2000)., <br />depending on the location in the County. Figures 4A through 4G identify the <br />approximate datum adjustment in the center of the County shown in each Figure. For <br />greater accuracy. please refer to the Corpscon program (USCOE. 2000). <br /> <br />12 <br />