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<br />The areas studied by detailed methods were selected with priority <br />given to all known flood hazard areas and areas of projected <br />development or proposed construction through March 1990. <br /> <br />2.2 Community Description <br /> <br />The majority of Broomfield is loca~ed in Boulder County, although <br />portions are situated in Adams and' Jefferson Counties. Broomfield <br />is located in north-central Colorado, on the eastern slope of the <br />Rocky Mountains, approximately 13 miles north of Denver. In 1970, <br />the population of Broomfield was 7,161; at the end of 1980, the <br />population was 20,730 (Reference 1). Continued growth is expected <br />for the City of Broomfield. <br /> <br />. <br /> <br />miles and are bounded on the north~est by a rise at an elevation <br />of approximately 5,400 feet. The ~treams generally flow <br />southeasterly, emptying into Big Dry Creek at an approximate <br />elevation of 5,200 feet. The draipage boundaries of the <br />individual basins are indistinct, being located at the crests of <br />the east-west rolls of the high plains. The creeks are generally <br />shallow, with no distinct channels., <br /> <br />The climate of the area has chara~teristic features of low <br />relative humidity, low rainfall, moderate to high winds, and a <br />large daily range in temgerature. I Temperatures range from a high <br />of 1020F to a low of -26 F at Roc~y Flats. The average maximum <br />and minimum temperatures are 60.2~F and 39.10F, respectively. The <br />average annual precipitation at Rocky Flats is 15.14 inches. <br />Sixty-nine percent of the precipitation occurs between April and <br />September. Summer precipitation is largely from thunderstorm <br />activity and is sometimes extremely heavy. <br /> <br />Typical area soils are composed mdstly of the Nunn, Platner, and <br />Renshill series, as defined by th~ U.S. Soil Conservation Service. <br />These soils are generally well dr~ined, nearly level to moderately <br />sloping formations of loamy alluvial material. Slopes vary from 0 <br />to 9 percent, and the natural vegetation is grass, although most <br />undeveloped areas are cultivated. The permeability of these soils <br />is moderate to slow (Reference 2). <br /> <br />Land use within the drainage basi9s consists of a mixture of com- <br />mercial and residential developme9t with several parks and open <br />space areas. <br /> <br />2.3 Principal Flood Problems <br /> <br />The City Park Channel, located in southwestern Broomfield, <br />is well defined and narrow ~ntil it crosses West l20th <br />Avenue, where it becomes very shallow with low banks. The <br />slope of this channel avera~es 47.6 feet per mile. <br /> <br />4 <br />