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Lakewood Gulch and Lakewood Gulch Overflow Cross section data, Manning's II nil values, and starting water- surface elevations were obtained from the 1979 UDFCD Flood Hazard Area Delineation report for Lakewood Gulch (Reference 53). The starting water-surface elevations for Lakewood Gulch were established using the elevation of a 10-year flood on the South Platte River at its confluence with Lakewood Gulch. The starting water-surface elevations for Lakewood Gulch Overflow were taken from the Lakewood Gulch profile at the confluence with Lakewood Gulch Overflow. Values of Manning's "n" on Lakewood Gulch were selected in order to model the roughness of the streambed and overbank areas. Each cross section or group of cross sections was evaluated and assigned a Manning's "nil value for the left overbank, the channel, and the right overbank. Selected Manning's "n" values ranged from as low as 0.02 for street crossings and parking lots to as high as 0.08 for overbank areas restricted, by buildings or debris. At a typical channel section, consisting of a natural channel with natural overbank areas, the generally selected Manning's "n" values were between 0.030 and 0.035 in the main channe l, and between 0.045 and 0.050 in the' overbank areas. In . overbank. areas that were restricted by buildings, Manning IS "n" values of 0.08 were used when it was fel t that a flow of water could occur through the developed area. Dry Gulch (Lakewood Gulch Tributary) Cross section data, Manning's "nit values, and starting water- surface elevations were obtained from the 1977 UDFCD Flood Hazard Area Delineation report for Dry Gulch and its tributaries (Reference 12). Values of Manning's "n" used in that report ranged from as low as 0.017 for streets and parking lots to as high as 0.100 for overbank areas restricted by buildings. In general, areas of natural channel section with natural overbanks were assigned Manning's "n" values of approximately 0.045 and 0.080. Where buildings represented significant obstructions to the channel flow, they were represented in the cross sections as total blockages. Starting water-surface elevations were determined from the Lakewood Gulch flood profiles. Harvard Gulch. Harvard Gulch Overflow. West Harvard Gulch. and Dry Gulch (Harvard Gulch Tributary) Cross section data, ~anning IS "n" values, g-od starting water- 'l'rface elevations were developed :or '.se :n (he 1979 UDFGD ?load ~fazard Area Delineation report for ~arvard Gulch, West Harvard Gulch, and Dry GuLch (Har~ard GuLch Tributary) (Reference 14). ~~QSS section infarmaticn ~a5 obcai~ed ?hatogrammetrical:y ~~ digitizing croSS sections T.arked 0n aerlal photographs of :he stream channel and floodplain (Refer<=:nce 54). The digitized r:ross sec:ion information was supplement~d ~ith ;~05S sections taken f~om topographic mapping (Reference 55) developed from the aer:al photography. All crosS sectic:1s at bridges -.1ere obtained from field measurement. 22