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Manning's un" values and cross section data in some portions of Westerly Creek were obtained from the 1977 UDFCD Flood Hazard Area Delineation report for Westerly Creek (Reference 64), Additional cross section data were obtained from construction drawings for recent channel improvements (Reference 65). Start ing water-surface elevat ions were determined in the 1977 Major Drainageway Planning report for Westerly Creek (Reference 11), Coon Creek and Other Tributaries Elevations for Coon Creek, First Creek, First Creek Tributary, Sloans Lake Basin, and Marston Lake North Drainage Basin, which are presented in this Flood Insurance Study as approximate study areas, were determined previously as part of the following UDFCD reports: the Flood Hazard Area Delineation report for Dutch Creek, Lilley Gulch, Coon Creek, and Three Lakes Tributary (Reference 66); the Major Drainageway Planning report for First Creek (Reference 67); the Flood Hazard Area Delineation report for Sloans Lake Basin (Reference 68); and the Flood Hazard Area Delineation report for Marston Lake North Drainage Basin (Reference 69). - Due to the channel improvements along a reach of Coon Creek from State Highway 121 to a point approximately 1,850 feet upstream at Southwest Commons, the lOa-year recurrence interval flood is contained in the channel. The hydraulic analyses for this study were based on unobstructed flow (Reference 25), The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the flood profiles are thus considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail, Generally, the distances on the flood profiles correspond to distances measured along the centerline of the designated watercourses. In several areas, however, the meandering nature of the low-flow streambeds necessitated use of distances measured along the centerline of the lOa-year flow paths. On the maps, these flow lines, used to establish the respective profile distances, are delineated and labeled as Profile Base Lines, Excepting some overland flow across South Wadsworth Boulevard, the lOa-year recurrence interval flood is contained in the channel, This is due to channel improvements and the addition of. culverts and a sedimentation control basin along a reach of Marston Lake North, from Vaile Lake to a point approximately 3,600 feet upstream of Highway 121. The hydraulic analyses for this study were based on unobstructed flow. Manning's "nil values ranged from 0,013 to 0,035. . All elevations are referenced to the National Geodetic Vertical Datum (NGVD) of 1929, Elevation reference marks used in this study are shown on the maps, 26