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<br />Lakewood Gulch and Lakewood Gulch Overflow <br /> <br />Cross section data, Manning's "n" values, and starting water- <br />surface elevations were obtained from' the 1979 UDFCD Flood Haurd <br />Area Delineation report for Lakewood' Gulch (Reference 53). The <br />starting water-surface elevations for Lakewood Gulch were <br />established using the elevation of a 10-year flood on the South <br />Platte River at its confluence with Lakewood Gulch. The starting <br />water-surface elevations for Lakewood Gulch Overflow were taken <br />from the Lakewood Gulch profile at the confluence with Lakewood <br />Gulch Overflow. Values of Manning's. "n" on Lakewood Gulch were <br />selected in order to model the roughness of the streambed and <br />overbank areas. Each cross section o~ group of cross sections was <br />evaluated and assigned a Manning's "n'" value for the left overbank, <br />the channel, and the right overbank. .Selected Manning's "n" values <br />ranged from as low as 0.02 for street ~rossings and parking lots to <br />as high as 0.08 for overbank areas restricted by buildings or <br />debris. At a typical channel section, consisting of a natural <br />channel with natural overbank are~s, the generally selected <br />Manning's "n" values were between 0'.030 and 0.035 in the main <br />channel, and between 0.045 and 0.050 in the overbank areas. In <br />overbank areas that were restricted' by buildings, Manning's "n" <br />values of 0.08 were used when it wa, felt .that a flow of water <br />could occur through the developed area, <br /> <br />Dry Gulch (Lakewood Gulch Tributary) <br /> <br />Cross section data, Manning's "n" values, and starting water- <br />surface elevations were obtained from, the 1977 UDFCD Flood Hazard <br />Area Delineation report for Dry Gulch and its tributaries <br />(Reference 12). Values of Manning's "n" used in that report ranged <br />from as low as 0.017 for streets and. parking lots to as high as <br />0.100 for overbank areas restricted, by buildings. In general, <br />areas of natural channel section with natural overbanks were <br />assigned Manning's "n" values of approximately 0 .045 and 0 .080. <br />Where buildings represented significant obstructions to the channel <br />flow, they were represented in the cross sections as total <br />blockages. Starting water-surface elevations were determined from <br />the Lakewood Gulch flood profiles. <br /> <br />Harvard Gulch. Harvard Gulch Overflow; West Harvard Gulch. and Dry <br />Gulch (Harvard Gulch Tributary) i <br /> <br />Cross section data, Manning's "n" ,values, and starting water- <br />surface elevations were developed for' use in the 1979 UDFCD Flood <br />Hazard Area Delineation report for Harvard Gulch, West Harvard <br />Gulch, and Dry Gulch (Harvard Gulch Tributary) (Reference 14). <br />Cross section information was obtained photogrammetrically by <br />digitizing cross sections marked oq aerial photographs of the <br />stream channel and floodplain (Referejlce 54). The digitized cross <br />section information was supplemented ~ith cross sections taken from <br />topographic mapping (Reference 55) ideveloped from the aerial <br />photography. All cross sections at' bridges were obtained from <br />field measurement. <br /> <br />22 <br />