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<br />. <br /> <br />. <br /> <br />. <br /> <br />STUDY AREA DESCRIPTION <br /> <br />Community Descrintion <br />Jefferson County is located in north-central Colorado along the Front Range of the Rocky <br />Mountains and is bordered by Boulder, Gilpin, Clear Creek, Park, Teller, Douglas, Arapahoe, <br />Denver, and Adams Counties. The county's land area covers about 789 square miles. Jefferson <br />County is now the most populated county in Colorado, with a population on the order of half a <br />million people (503,9] 5) as estimated by the Department of Local Affairs in July 1997). <br /> <br />Jefferson County was created in 186] and named in honor of Thomas Jefferson. It was one of the <br />original ]7 counties of the Colorado Territory. The City of Golden, founded in ]859 and originally <br />named Golden City, is the County Seat and is located is approximately ]5 miles west of downtown <br />Denver. Development in the county began with the discovery of gold and the gold mining <br />activities that resulted. Other types of mining, in addition to significant agricultural activities, <br />played a key role in the growth and development of the county. Post World War II industry <br />evolved to create a more diverse and stable economy in the later part of the 20lh century. <br /> <br />The area studied for the FIS is the unincorporated areas of Jefferson County as of July 4, ] 989. <br /> <br />Watershed Descrintion <br />Jefferson County is located entirely within the South Platte River basin on the eastern slope of the <br />Continental Divide. The county's land area covers about 789 square miles. The topography in <br />Jefferson County varies significantly and ranges from steep mountainous terrain to relatively flat <br />plains-like land areas. Ground elevations in the county range from about 5,000 feet to over] 0,00 <br />feet. The average annual rainfall has been estimated to be ] 4.59 inches. <br /> <br />Floodinl! Problems and Floodinl! Historv <br />Floods in the subject watersheds normally occur during the months of May through September as a <br />result of intense localized cloudbursts/thunderstorms or general rainstorms. Due to topographic and <br />meteorological variability, flooding scenarios in different parts of the county can be quite different. <br />Areas subject to intense thunderstorms are prone to flash flooding, while other areas may be <br />subject to less damaging flooding from rapid melting of mountain snowpack in the spring and early <br />summer months. A combination of rainfall on top of snowmelt can sometimes prove to be the worst <br />flooding scenario for Colorado's mountain and foothills streams. <br /> <br />Major floods in Jefferson County have been documented since the late 1800's. Examples of known <br />flood events are as follows: <br /> <br />Bear Creek: Floods on this creek have occurred in ] 876, ] 894, ] 957, 1965, and 1969. The worst <br />known event was the flood of ]896 where 27 people were killed and major property damage was <br />experienced. The recorded peak discharge for that event was 8,600 cfs. <br /> <br />Clear Creek: Past floods on Clear Creek have been fairly infrequent and more of a concern in the <br />upper reaches of the watershed. A dam failure flood in ] 957 produced the highest recorded peak <br />2 <br />