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3 Sheet 2 of 20, Basin Boundaries, shows the drainage basin limits of Goldsmith Gulch. The basin extends from an elevation of 5,384 at Cherry Creek to an elevation of 5,775 at the basin divide lo- cated approximately one-fourth mile south of Arapahoe Road. Tra- versing a length of approximately eight miles, the average stream gradient for Goldsmith Gulch is approximately 49 feet per mile. Drainage areas at various points within the basin are provided in Table 1. The lower portion of the basin, within the limits of the City and County of Denver, is considered to be presently, fully developed. The development consists of average density residential develop- ment, high density residential development, commercial develop- ment and open space. In certain areas along the gulch, open space has been preserved through the development of city parks. Along other reaches of the gulch, green belts have been provided and have been maintained by the City. - FLOOD HISTORY - Table 1 Location Drainage Area (Sq. mi.) Little information is available on past flooding on Goldsmith Gulch. Discharge measurements, high water marks and other flood data have not been officially recorded. Most published accounts of past flooding are related to the South Platte River and the larger tributaries. When there was flooding on these other streams, such as Cherry Creek, one can be certain Goldsmith Gulch was carrying unusually high flood flows. Drainage Areas Goldsmith Gulch Cherry Creek 8.0 Hampden Avenue 4.9 I-225 3.5 Belleview Avenue 2.6 Dayton Street 0.6 Southmoor Park Tributary Mouth near Dartmouth Avenue 1.4 West Tributary Mouth near Orchard Road 0.8 History will show that floods have and will continue to occur along Goldsmith Gulch. Few records exist as little development existed along the gulch which would draw attention and concern to the unusually high water. Present day conditions are much different from those of the past and, as a result, no records would relate extent and severity of damage caused by an extreme flood flow should such occur today. For the purposes of this study, the drainage basin was considered to be fully developed consistent with the comprehensive land use plans of the City and County of Denver, City of Greenwood Village and Arapahoe County. The proposed land uses in this part of the basin are primarily residential with some provision for commercial and office park development along the major streets. The planned residential development would be average to high density and would encompass approximately 80% of the total drainage area. The re- maining 20% of the drainage area would be retained as open space or developed for commercial uses. Pictures are included in the Appendix which do show the impact of a current day flood situation. The pictures show flooding along certain areas of main Goldsmith during the storm of May 5-6, 1973. Estimates of flood frequency resulting from this long duration storm would put the Goldsmith Gulch flood of 1973 at a 5-year to 10-year occurrence interval.l 1. "Storm of May 5-6, 1973 in the Denver Metro Area: Frequency and Effect", Ducret and Hansen, USGS and UD&FCD, 1973.