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and methods of study were proposed to, and agreed upon by, FEMA and the City of Aurora. The streams and drainageways studied by detailed methods include Sand Creek, Westerly Creek, Toll Gate Creek, East Toll Gate Creek, West Toll Gate Creek, Cherry Creek Spillway Drain, West Toll Gate Creek Tributary, Unnamed Creek, Sable Ditch, and Granby Ditch. The streams and drainageways studied by approximate methods include Columbia Creek, Senac Creek, Side Creek, First Creek, West Toll Gate Creek, and West Toll Gate Creek Tributary. 2.2 Community Description The City of Aurora is located immediately east of the City and County of Denver, in the southwest corn~r of Adams County and the northwest corner of Arapahoe County. The city 'is bounded by the City and County of Denver to the west, northwest, and southwest; and the unincorporated areas of Arapahoe County to the south and east. The City of Aurora '8 one of the fastest growing cities in Colorado. Its population has increased by approximately 51,800 persons from the 1970 estimate of 78,200 tCl the 1976 estimate of 130,000 (Reference 8). Its population in 1987 was estimated to be 220,066. The economy of the area is based on commercial and agricultural industries. The upper portions of all streams studied, with the exception of Westerly and Sand Creeks, are relatively undeveloped. Sand Creek floodplain development consists of a mobile home park and isolated buildings. Urban development is more extensive in the lower reaches, especially in the shared floodplain of Sand and Toll Gate Creeks at their confluence. The Westerly Creek basin is heavily developed for residential and industrial uses for its entire length. The average annual temperature in Aurora is degrees Fahrenheit and the average annual 15.5 inches (Reference 9). approximately 50 precipitation is The streams within Aurora are intermittent, and the channel banks are typically eroded or covered with weeds and other vegetative cover. The major soil types within the floodplain consist of sandy clay loam, silt loam, sand loam, and silty clay loam to silty clay (References 10 and 11). Sand Creek, which is the major drainageway through Aurora, flows in a northwesterly direction through the city. The channel is well defined through the study reach and has an average channel slope of 26 feet per mile. Toll Gate Creek and West Toll Gate Creek have an average channel slope of 18 feet per mile from Interstate Highway 225 4