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<br />. <br /> <br />. <br /> <br />. <br /> <br />on the creek, however the gage records are only short-term and contain 5 years of annual peak flow <br />data (1951-1955). The annual peak flows for Little Columbine Creek are presented in Table 2. <br /> <br />Table 2 <br />Annual Peak Flows for Little Columbine Creek <br /> <br />Water year Date Disehar2e (efs) <br />1951 Mav5 11 <br />1952 May 3 34 <br />1953 July 11 13 <br />1954 November 6 14 <br />1955 June 14 6 <br /> <br />The Town of Grand Lake should regulate the approximate floodplains on a case-by-case basis. <br />FEMA requires that a detailed floodplain analysis must be performed by a professional engineer <br />and submitted by the developer or development proponent for development projects involving more <br />than 5 acres or more than 50 units (whichever is more restrictive). <br /> <br />Hvdraulic Analvsis <br />Hydraulic methods used for the approximate floodplain delineations shown on the Town of Grand <br />Lake FIRM panel are not available or have not been documented by FEMA. For future studies, an <br />approximate 100-year flood elevation at a particular location on the river may be obtained by using <br />the 100-year peak flow value (as provided in this report) in conjunction with an acceptable <br />hydraulic analysis. Hydraulic analyses for determining lOa-year water surface elevations for <br />approximate floodplains may be performed using FEMA's Quick-2 computer program, the Corps <br />of Engineers' HEC-2 computer program, Haestad's Flowmaster program, 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 7.5' quadrangle <br />maps are not advised. <br /> <br />Floodplain Mappinl! <br />The existing Flood Insurance Rate Map for Town of Grand Lake depicts areas subject to 100-year <br />flooding based on approximate technical methods. The map does not show flood profiles, base <br />flood elevations, or sufficient detail in order for Town officials, engineers, developers, and land <br />owners to make floodplain determinations with any certainty. The Colorado Water Conservation <br />Board can be contacted to request technical assistance for approximate floodplain analyses as <br />needed. <br /> <br />4 <br />