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Little Dry Creek Tri butary C Mouth upstream 4,000 feet 0.8 mile Bates Lake Area Colorado and Southern Railroad to Bates Lake 1. 7 miles 2.2 Community Description Arvada is located on the east slope of the Rocky Mountains, about 6 miles northwest of the State Capitol Building in Denver. The majority of the streams that were studied within the City corporate limits flow through moderate density residential and commercial areas. Much of the development on the streams has occurred within the past 10 years, and continued growth is expected to occur. All of the study streams have their source of flow in the Rocky Flats area and eastern foothills of the Rocky Mountains. Ralston Creek is tributary to both the Ralston and Arvada Reservoirs and Leyden Creek is tributary to the Leyden Reservoir. Little Dry Creek flows through, or is adjacent to, both Lake Arbor and the Pomona Lakes which are recreational facilities owned and maintained by the City of Arvada. The total basin area draining the study streams is approximately 104 square miles. The elevations within the drainage basins for the streams range from over 10,000 feet in the upper portion of the Ralston Creek Basin to 5,250 feet at the confluence of Ralston Creek and Clear Creek. For the most part, the study streams have a relatively small base flow for most of the year. The area's climate 1S characterized by low relative humidity, low rainfall, moderate to high wind movement, and a large dai ly range in temperature. The average annual maximum and minimum temperatures are 60.20F and 39.1oF, respectively. The average annual preci pi tation is 15.14 inches. Sixty-nine percent of thi s precipitation falls from April through September. Summer precipitation is largely from thunderstorm activity and is sometimes extremely heavy. Land use wi thin the study area is mixed, wi th commercial, 1 ight industrial and residential developments, and several parks and open undeveloped areas. 2.3 Principal Flood Problems In general, the streams within the City of Arvada are well defined with relatively narrow channels. Potential flooding problems along the streams can be attributed to the large developed areas that have encroached into the overbanks of these channels severely constricting the floodplain and diminishing the carrying capacity for large floodflows. Although the potential exists for severe flooding, there is little information regarding past floods on the study streams. Records of 4