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<br />I. BACKGROUND AND PROBLEM IDENTIF'ICATION <br /> <br />Community Description <br /> <br />Fort Collins is located along the banks of the Cache La Poudre River in eastern Larimer County, <br />where the foothills of the Rockies meet the Great Plains, at an elevation of 4,979 feet above sea <br />level. Fort Collins is located approximately 60 nriles north of Denver (Figure 1). The climate is <br />semi-arid with approximately 300 days of sunshine and an average annual precipitation of 14.5 <br />inches. Winters are moderately cold and dry with an average January temperature of27 degrees <br />Fahrenheit and 30 percent humidity. The average July temperature is 71 degrees with 43 percent <br />humidity. <br /> <br />Fort Collins became incorporated in 1873 and haS grown rapidly, from approximately 1,376 <br />residents in 1880 to approximately 56,800 in 1975, to a CWTent (1995) estimate of 99,726. Fort <br />Collins is at the northern edge of the rapidly growing Front Range of the Colorado Rocky <br />Mountains. The City currently covers approximately 44 square miles of area. <br /> <br />Principal Flood Problems and History <br /> <br />Fort Collins is vulnerable to flooding from several different sources (Figure 2). Flood sources <br />include; 1) the rivers and streams in Fort Collins which include the Cache La Poudre River, <br />Spring Creek, Dry Creek, Fossil Creek, Cooper Slough, and Boxelder Creek; 2) potential dam <br />failure; and, 3) urban flash flooding from intense rainfall on smaller drainage basins. The main <br />cause of floods in the Fort Collins area is intense rainfall, which normally occurs in the period of <br />May through September. The Cache La Poudre River flooding could also increase in May and <br />June, as a result of increased runoff from snowmelt. <br /> <br />Fort Collins has a long association '.'1ith flooding. Ansel Watrous (1911), referring to the flood of <br />1864, stated that "Fort Collins, the county seat arId principal town in Larimer County, owes its <br />origin and fust place on the map to the intervention of a flood in the Cache La Poudre River." <br /> <br />Cache La Poudre River <br /> <br />..- <br />The Cache La Poudre River is a major left bank tributary of the South Platte River. It joins the <br />South Platte about 5 miles east of Greeley, Colorado. The Poudre River originates within Rocky <br />Mountain National Park at an elevation close to 12,000 feet above mean sea level; then it flows <br />successively northward, eastward, and southeastward to its confluence with the South Platte <br />River at an elevation of about 4,600 feet above wean sea level (m.s.!). The drainage area at its <br />mouth is 1,890 square miles. The drainage area of the Poudre River above Fort Collins is <br />approximately 1,129 square miles. <br /> <br />Notable floods occurred on the Cache LaPoudre River in 1844,1864,1884,1891,1904,1923, <br />and 1930. The three largest floods occurred in 1864, 1891, and 1904, with flood peaks of <br /> <br />1 <br />