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<br />e 2. BASIN CHARACTERlSIICS <br /> <br />e <br /> <br />e <br /> <br />2. 1 General Hvdrologic Description <br /> <br />The City of Canon City is located in south,central Colorado in the <br />eastem portion of Fremont County approximately 46 miles southwest of <br />Colorado Springs, Colorado, The total land area contained within the <br />corporate boundaries is approximately 10,44 square miles. The 1995 <br />population for the City of Canon City was reported as 15,000. <br /> <br />The climate in the study area of Canon City is semiarid. Average <br />annual precipitation is 13 inches based on an approximation from the U.S. <br />Department of Commerce Map of Normal Annual Precipitation for the State <br />of Colorado. Periods of drought result from the uneven distribution of <br />precipitation. <br /> <br />The Arkansas River above Canon City is a typical mountain stream <br />which descends 6000 feet in elevation in a distance of less than 130 miles, <br />at gradients often exceeding 50 feet per mile. While slopes are steeper in <br />the upper drainage basins the dense vegetation in these areas serves to <br />reduce rainfall runoff. A greater percent of runoff is permitted by the sparse <br />vegetation of the foothills and pasture land at the lower elevations. <br /> <br />Consequently, the majority of flood problems in the study area are <br />caused by cloudburst type storms over the foothills to the north which usually <br />occur during the summer months of June, July and August. Characteristic <br />of this type of flooding is a high intensity, short duration rainstorm of limited <br />areal extent, resulting in a flash flood of high peak flow, short duration, and <br />low total runoff volume. <br /> <br />A 100-year flood is defined as having a 1 percent chance of <br />occurring In any given year. Similarly, the 25-year flood has a 4 percent <br />chance of occurring in any given year. The 100'year flow for the Arkansas <br />River at Canon City is 20,500 cubic feet per second (cfs). Table 1 shown on <br />the next page presents corresponding drainage areas and flows for the <br />drainages at Canon City (reference 1,2). <br /> <br />2.2 Historv Of Floodino <br /> <br />Floods on the Arkansas River in Fremont County are of two general <br />types. One type is represented by "spring floods" which result from melting <br />snow and can often be augmented by rainfall runoff. The other type is <br />represented by 'summer floods' which result entirely from rainfall. The <br />spring floods are characterized by comparatively moderate rates of flow of <br />long duration with large volumes of runoff. The summer floods are <br />characterized by high peak rates of discharge with relatively smaller volumes <br />of runoff, <br /> <br />2 <br /> <br />.. The 100-year flood <br />has a one percent <br />chance of occurring <br />in any given year. <br /> <br />, 100-year flow at <br />Canon City <br />= 20.500 cfs <br />= 5353.8 feet NGVD' <br />= 15.0 feet gage <br />= 10.0 feet stage <br /> <br />See Figure 3 for <br />use of gage height <br />and stage <br />