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I I I I I I I I I I I I I I I I I I I 4 At the west end of the basin, two dams owned by Eastlake Water Company (of which Thornton owns 90% of the stock) are presently being used as detention storage for the supply of irrigation water to local farmers. However, this function will be suspended at the end of the 1982 irrigation season. At the extreme east end of the basin lie the Adams County Fairgrounds and Golf Course, and the South Platte River. Part of this area is subjected to periodic flooding from the South Platte River in addition to flooding from the Brantner Gulch watershed. Brantner Gulch flows are conveyed in a concrete lined channel through the Golf Course and adjacent to the Fairgrounds area. The soils of the watershed primarily consist of the Platner, Ulm and Renshill Loams in the greater portion of the basin and in the upper and middle portions of the basin. The lower portion of the channel consists of Nunn clay loam, Arvada loam, and loamy alluvial soil near the river. All of these soils are described in the Soil Survey of Adams County, Colorado, published by the Soil Conservation Service, as having moderate to very low permeability. The static water table in the loamy alluvial land near the river is seasonably about three feet below the surface. The Brantner Gulch watershed area consists of 10.56 square miles, and is about twice as long as it is wide. The Gulch flows eastward through Adams County to its confluence with the South Platte River. Regional Park Tributary Basin The Regional Park Tributary watershed is located northeast of and adjacent to the Brantner Gulch watershed, all within Adams County. Its location is more specifically shown on Figure 16. The drainage basin consists of a mildly sloping, grass covered terrain at the upper and middle portions of the basin and relatively level land at the lower end near the South Platte River. The watershed is drained by two separate earth channels, hereafter referred to as North and South Regional Park Tribu- taries. Presently, the basin for the South Tributary, Tributary VI, is undeveloped at the upper end and developed to a limited extent at its lower end at the County Fairgrounds near the Platte River. A portion of its flow combines with the Brantner Gulch flow because the Gulch water exceeds its banks in this area. The present basin for the North Tributary, Tributary VII, is undeveloped for its entire length. The existing channels have been shaped by rainfall runoff from the basin over a period of several years. Anticipated development will increase the frequency and quantity of flow in the channels. Yet, flood damages can be prevented if enough land is reserved for protection purposes. In addition, it will be necessary to consider channel improvements for control of increased channel erosion. Flow constrictions occur at road crossings of the two channels due to undersized culverts. Thus, it is also necessary to consider the flooding effects of back- water at these locations.