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<br />. <br /> <br />. <br /> <br />. <br /> <br />Hvdraulic Analvsis <br />Hydraulic methods used for the approximate floodplain delineations shown on the Town of Ovid <br />FHBM panel are not available or have not been docwnented by FEMA, For future studies, an <br />approximate 100-year flood elevation at a particular location on the Lodgepole Creek may be <br />obtained by using the 100-year peak flow value (as provided in this report) in conjunction with 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 or HEC-RAS computer programs 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, Approximate lOO-year water surface elevations for the South Platte River <br />may be interpolated from the information provided in the 1977 Corps of Engineers report, <br /> <br />The CWCB has developed a limited amount of hydraulic information for Lodgepole Creek, which <br />can be found in the Appendix of this report, Based on the asswned 100-year flow value of 3,500 <br />cfs, a surveyed cross-section perpendicular to the stream at Momoe Street, and a depth calculation <br />using Manning's equation, the CWCB estimates that overbank flooding depths along 2nd Street <br />would be 2 to 3 feet during a IOO-year event Bridge geometry information was measured in the <br />field, and a summary is provided in the Appendix, However, bridge restrictions and additional <br />channel cross-sections were not modeled in a backwater program to determine a water surface <br />profile for the stream, <br /> <br />Floodplain Mappin!! <br />The existing Flood Hazard Boundary Map for Town of Ovid depicts areas subject to IOO-year <br />flooding from the South Platte River based on approximate technical methods, The map does not <br />show flood profiles, base flood elevations, or sufficient detail in order for Town officials, engineers, <br />developers, and land owners to make floodplain determinations with any certainty, A better source <br />of flood data for the South Platte River can be found in the 1977 Corps of Engineers Floodplain <br />Information Report that is available for review in the CWCB's floodplain information library, <br />Interested parties may contact the Colorado Water Conservation Board to clarify flood related <br />issues and to request technical assistance as needed, <br /> <br />The Town of Ovid should regulate the approximate floodplains on a case-by-case basis, FEMA <br />requires that a detailed floodplain analysis must be performed by a professional engineer and <br />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 />4 <br />