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<br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br /> <br />Hvdraulic Analvsis <br />Water surface profiles for stream reaches studied by detailed methods were developed using the <br />U.S. Army Corps of Engineers HEC-2 step-backwater computer model. Hydraulic methods used <br />for the approximate floodplain delineations shown on the El Paso County FIRM panels are not <br />documented by FEMA in the FrS. For future studies, an approximate roO-year flood elevation at <br />a particular location on an approximate stream may be obtained by application of the CWCB <br />regression equations (see Tables 2 and 3) in conjunction with cross section information and an <br />acceptable hydraulic analysis. Hydraulic analyses for determining 100-year water surface <br />elevations for approximate floodplains may be performed using FEMA's Quick-2 computer <br />program, the Corps of Engineers' HEC-2 computer program, Flowmaster, or other acceptable <br />hydraulic methods. Channel and floodplain cross-sections may be obtained from detailed <br />topographic mapping or from field surveys. Cross-sections obtained from USGS quadrangle <br />maps are not advised. <br /> <br />Floodplain Mappin!! <br />The 1999 FrS for El Paso County includes stream reaches with both detailed and approximate <br />floodplain mapping. For reaches studied by approximate methods, the FrS does not include <br />flood profiles, base flood elevations, or sufficient detail for county and municipal officials, <br />engineers, developers, and land owners to make floodplain determinations with any certainty. <br />Flow rates and methodologies have been included in this HA to assist with these determinations <br />and the Colorado Water Conservation Board can be contacted to request technical assistance for <br />approximate floodplain analyses as needed. <br /> <br />18 <br />