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<br />. <br /> <br />tenths of an inch per event) than the areas adjacent to the <br />foothills. The occurrence of precipitation varies; however, most <br />of the rainfall is concentrated in May. Thunderstorms also occur <br />irregularly throughout the summer months. The temperature extremes <br />at Boulder are evidenced by mean maximums ranging from 46.3 degrees <br />Fahrenheit (OF) in January to 88.30F in July, and by mean minimums <br />ranging from 2l.60F in January to 6l.0oF in July. <br /> <br />) <br /> <br />The City of Boulder is located in central Boulder County, along the <br />foothills of the Front Range. In 1980, Boulder had a population of <br />76,685 (Reference 13), an increase of 14.7 percent since 1970. <br />This population growth is expected to continue with further <br />expansion into identified floodplain areas. <br /> <br />The study area includes the drainage basins of seven streams <br />located throughout the Boulder area. All study streams are <br />tributary to Boulder Creek, with a total drainage area of <br />approximately 23.2 square miles. The elevation in Boulder ranges <br />from 8,520 feet at the headwaters of Fourmile Canyon Creek to 5,155 <br />feet at the confluence of Fourmile Canyon Creek with Boulder Creek. <br /> <br />All stream reaches east of the foothills, except for those on <br />Fourmile Canyon Creek, are located within urbanized areas with <br />occasional open-space and park areas. The terrain of these <br />subbasins consists of mild slopes with topsoils in the Band C <br />hydrologic soils group with some D soils. Vegetation for most of <br />the stream reaches is characteristic of urban areas. Fourmile <br />Canyon Creek is located in sparsely developed agricul tural areas. <br />Vegetation along Fourmile Canyon Creek and the downstream reaches <br />of Bear, Skunk, Coose, and Wonderland Creeks consists of natural <br />grasses and weeds. <br /> <br />The Town of Jamestown is a small mountain community located in the <br />central northwest section of Boulder County, approximately 10 miles <br />northwest of the City of Boulder. The 1970 population was 185, and <br />was estimated at 240 in 1980. Communities near Jamestown are <br />Lyons, approximately 11 miles to the northeast, and Longmont, <br />approximately 16 miles to the east. <br /> <br />Historically a mlnlng town, Jamestown is now a residential <br />community. Most of its residents are commuters to either Boulder, <br />Denver, or Longmont. <br /> <br />. <br /> <br />Little James Creek, draining an area of <br />miles, joins James Creek at Jamestown. <br />drainage area of 14.5 square miles at the <br />is a tributary to Lefthand Creek, which <br />St. Vrain Creek near Longmont. Rainfall <br />nearly 24 inches annually. <br /> <br />approximately 3 square <br />James Creek, with a <br />downstream study limit, <br />flows eastward to join <br />in the basin averages <br /> <br />. <br /> <br />The terrain is mountainous with steep slopes. The soils of the <br />Allen Park Series, which formed on the mountain slopes between <br />elevations of 6,300 and 8,200 feet, are loamy colluvium and <br />weathered granite residuum. The surface layer, approximately 2 <br /> <br />9 <br />