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. . . Hvdraulic Analvsis Hydraulic methods used for the approximate floodplain delineations shown on the Town of Ovid FHBM panel are not available or have not been docwnented by FEMA. For future studies, an approximate 100-year flood elevation at a particular location on the Lodgepole Creek may be obtained by using the 100-year peak flow value (as provided in this report) in conjunction with an acceptable hydraulic analysis. Hydraulic analyses for determining 100-year water surface elevations for approximate floodplains may be performed using FEMA's Quick-2 computer program, the Corps of Engineers' HEC,2 or HEC-RAS computer programs or other acceptable hydraulic methods. Channel and floodplain cross-sections may be obtained from detailed topographic mapping or from field surveys, Cross-sections obtained from USGS 7.5' quadrangle maps are not advised, Approximate lOO-year water surface elevations for the South Platte River may be interpolated from the information provided in the 1977 Corps of Engineers report. The CWCB has developed a limited amount of hydraulic information for Lodgepole Creek, which can be found in the Appendix of this report. Based on the asswned 100-year flow value of 3,500 cfs, a surveyed cross-section perpendicular to the stream at Momoe Street, and a depth calculation using Manning's equation, the CWCB estimates that overbank flooding depths along 2nd Street would be 2 to 3 feet during a IOO-year event Bridge geometry information was measured in the field, and a summary is provided in the Appendix. However, bridge restrictions and additional channel cross-sections were not modeled in a backwater program to determine a water surface profile for the stream. Floodplain Mappin!! The existing Flood Hazard Boundary Map for Town of Ovid depicts areas subject to IOO-year flooding from the South Platte River based on approximate technical methods. The map does not show flood profiles, base flood elevations, or sufficient detail in order for Town officials, engineers, developers, and land owners to make floodplain determinations with any certainty. A better source of flood data for the South Platte River can be found in the 1977 Corps of Engineers Floodplain Information Report that is available for review in the CWCB's floodplain information library. Interested parties may contact the Colorado Water Conservation Board to clarify flood related issues and to request technical assistance as needed. The Town of Ovid should regulate the approximate floodplains on a case-by-case basis. FEMA requires that a detailed floodplain analysis must be performed by a professional engineer and submitted by the developer or development proponent for development projects involving more than 5 acres or more than 50 units (whichever is more restrictive). 4