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elevation approximately 13,000 feet at the headwaters, lowering to 6,800 feet at <br />the mouth. <br />The Mancos River floodplain is fl~t and lightly developed, with the exception of <br />the area near Main Street, in the Town of Mancos. At Main Street, building walls <br />and foundations serve as the channel bank. <br />Five major roads cross the river ~long the detailed study reach of the Mancos <br />River. Of these, only the crossings at U.S. Highway 160 and Spruce Street <br />significantly affect floodflows within the floodplain. The sewage lagoons near <br />the western edge of the Town of 1'Vlancos along the Mancos River do not affect <br />- 100-year flood widths. <br />Obstructions to floodflows include brush and vegeta.tion along and within the <br />channel. During periods of high water, floodplain vegetation impedes or slows <br />floodflows. Debris carried by floodwaters can collect on floodplain vegetation <br />and impede and alter floodflow pat~erns in these areas. <br />Chicken ~reek is north of the Town of Mancos and west of the Mancos drainage <br />azea. This creek drains a small, narrow basin of approximately 22.3 square miles, <br />not including a 1.4-square mile area that is tributary to the Jackson Gulch <br />Reservoir. The headwaters of Chicken Creek are 12 miles upstream of U.S. <br />Highway 160, at Mancos. The creek flows in a south-southwesterly direction to <br />its confluence with the Mancos River, approximately 1 mile southwest of <br />Mancos. The basin elevations range from 11,200 feet to 6,200 feet above sea <br />level. <br />The Chicken Creek floodplain is mostly undeveloped. There are no ma}or bridge <br />crossings in the reach of the Chicken Creek study. Natural obstructions to flow, <br />consisting of brush, vegetation, and fallen trees, exist primarily in the middle of <br />the study area. Backwater from these obstructions does not cause a threat to <br />properties adjoining the creek. <br />According to the U.S. Bureau of the Census, the population within corporate <br />limits of the Town of Mancos increased from 870 in 1980 to 1,119 in 2000, an <br />' increase of 28.6 percent (U.S. Department of Commerce, Bureau of the Census). <br />2.3 Principal Flood Problems <br />The nature of flaoding problems within Montezuma County include: general <br />frontal type rainstorms, convective type cloudbursts, and snowmelt. Frontal type <br />rainstorms present the most serious flood hazard in the county. In May to June <br />the combination of spring snowmelt runoff and thunderstorms perpetuate the <br />potential for severe flooding. Antecedent ground moisture also contributes to <br />flood characteristics. <br />7 <br />