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SECTION II LENA GULCH OESCRIPTIJN GENERAL COMMENTS The tributary basin of Lena Gulch is approximately 13.8 square miles in area and located west of Denver in Townships 3 and 4 South, Ranges 69 and 70 West, 6th P.M. The basin slopes down from the south Lookout Mountain area northeast to the conf':uence. with Clear Creek about 2200 feet downstream of Kipl ing Street. The basin at its widest point measures about 2.1, mi les and is approximately 9.5 miles in lengthi' Lena Gulch i~, actually comp,"ised of three main gulches and a multitude of minor tributaries. Apex Gulch is approximately 2.7 miles of mountain stream that carl'ies runoff from the majority of the foothills portion of the basin. This stream is shown as the northerly stream in Basin 1 of Drawing No. I. The stream to the south, called Jackson Gulch, is approximately 1.9 miles long, and also extends into the foothills. These two streams join west of the Hogback to form the eli'lin stem of Lena Gulch and flows approximately 8.4 miles to Clear Creek. The highest point of the basin is 7567 feet above mean sea level with the ;Iowest being 5338 feet. The elevation of Lena Gulch at the confluence of Jackson and Apex Gulches is 6098 feet. The average stream slopes are 90 feet per mile for Lena Gulch and about 480 feet per mile for both Jackson and Apex Gulch. The main stem of Lena Gulch exhibits the charac- teristics of a high plains stream whereas Jackson and Apex Gulches are more closely related to mountainous streams. Lena Gulch normally carries a low base flow from Jackson and Apex Gulch on the west. During a heavy rainfa, I event runoff flow i.1- creases heavily in Jackson Gulch because it is treeless and has areas of rock quarries and other significant. deveIopment. Apex, however, generally exhibits a smai ler and more controlled flow be- cause of the dense forest on the north-facing slopes, generally 1 ight development, and scattered I ight stands of trees. Green Mountain sheds runoff into the upper reach of Lena Gulch at a mod- erate rate except for those areas that are urbanized. South Table Mountain contributes flow to reaches above and be1.ow Maple Grove Reservoir. The most significant increases in flow occur in the urbanized areas Urbanization has probably increased the runoff peak flow rates 40% to 100% from the historical undeveloped state. At the same time, development has reduced the cross "ectional flow area by up to 98% in several stretches of the Gulch. Historic topographical mapping indicates that three major reaches of the stream have been directed to flow in different di rections. I t is apparent that the Heritage Square (Magic Mountain) development has pushed the natural stream several hundred feet to the north. The trailer courts in the *Measured as direct distance, rather than along the thalweg.