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flow value in conjunction with an acceptable hydraulic analysis, An appropriate peak flow value may be obtained or estimated using the information described in the previous section. Hydraulic analyses for determining lOO-year water surface elevations for approximate floodplains may be performed using FEMA's Quick-2 computer program, the Corps of Engineers' HEC-2 computer program, normal depths calculations, or other acceptable hydraulic methods, Channel and floodplain cross-sections may be obtained from detailed topographic mapping or from field surveys. Floodplain Mappinl!: The existing Flood Insurance Study for Logan County includes numerous Flood Insurance Rate Map (FIRM) panels that cover the entire county, These maps show approximate floodplain delineations for most of the major flooding sources within the County, Detailed floodplain information is shown for portions of the South Platte River, Pawnee Creek Overflow, and Sand Creek in the vicinity of Sterling, Colorado. Land use, planning, and development decisions should not rely soley on the approximate floodplain delineations shown on the FIRM panels. Logan County should regulate its approximate floodplains on a case-by-case basis. FEMA regulations require that a detailed floodplain analysis be submitted to the County prior to most floodplain development activities, The detailed floodplain analysis needs to be performed by a professional engineer and submitted by the developer or project proponent for development involving more than 5 acres or more than 50 units, At a minimum, it is recommended that an approximate floodplain analysis (using hydrologic and hydraulic methods discussed above) be performed for the situations where a detailed analysis is not required, ~ FLOODPLAIN MANAGEMENT Local Ordinance Requirements Communities which manage their floodplains in Colorado do so most often through the local regulatory process. This requires a community to adopt an ordinance or regulation which sets forth the performance standards by which development will occur in identified flood hazard areas, Nationwide and in Colorado, regulations are enforced within the area of the lOO-year floodplain. The basic requirement of these regulations is that new development and significant improvement of existing development cannot occur in the 100-year floodplain without a floodplain development permit being obtained. Obtaining such a permit requires compliance with engineering standards. In communities like Logan County that have approximate floodplain information, the engineering standards have been more general. Structures must be built with materials and techniques that "minimize flood damages", For communities like Logan County that also have detailed floodplain information, more specific regulations apply. The use of engineering techniques presented in this report can help the County to better regulate its approximate floodplain areas, Flood Insurance ......- 5