FLOOD03708 - Laserfiche WebLink

Home Browse Search

cold, with mean daily temperatures of approximately 30*F from Nov- ember to March. Summers are short and hot, with mean daily maxi- mum temperatures greater than 90*F. The Mancos River drains approximately B3 square miles within the northeast part of Montezuma County at the downstream limit of the study, west of the Town of Mancos. The headwaters of the Mancos River are located approximately 16 miles upstream of U.S. Highway 160, at Mancos. The river flows in a southwesterly direction to the San Juan River, a tributary of the Colorado River. The drainage basin elevations range from 13,000 feet at the headwaters to 6,BOO feet at the downstream study limit. The Mancos River flood plain is flat and not heavily developed, with the exception of the area near Main Street. At Main Street, building walls and foundations serve as the channel bank. Four major roads cross the river along the study reach. Only the bridge crossing at Spruce Street significantly affects floodflows within the flood plain. The sewage lagoons near the downstream limit do not affect 100-year flood widths. Obstructions to floodflows include brush and vegetation along and within the channel. During periods of high water. flood plain vegetation impedes or slows floodflows. Debris carried by flood- waters can collect on flood plain vegetation and impede and alter floodflow patterns in these areas. Chicken Creek drains a small, narrow basin of approximately 22.3 square miles. not including a 1.4-square-mile area that is tributary to the Jackson Gulch Reservoir. The headwaters of Chicken Creek are located approximately 12 miles upstream of U.S. Highway 160 at Mancos. The creek flows in a south-southwesterly direction to its confluence with the Mancos River. approximately 1 mile southwest of Mancos. The basin elevations range from 11.200 to 6,200 feet. The Chicken Creek flood plain is mostly undeveloped. There are no major bridge crossings in the reach of the Chicken Creek study. Natural obstructions to flow. consisting of brush. vegetation. and fallen trees, exist primarily in the middle of the study area. Backwater from these obstructions does not cause a threat to properties adjoining the creek. 2.3 principal Flood Problems Flood events on the Mancos River and Chicken Creek are usually the result of spring snowmelt coupled with thunderstorms occurring through May and June. Antecedent ground moisture also contributes to flood characteristics. High ground moisture coupled with warm 4