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<br />temperature contrast is greatest between the warm surface air and <br />cool upper air. The upper air is still very cold to the north, but <br />surface air has begun to heat up rapidly to the south. <br /> <br />. <br /> <br />This maximum contrast causes the heaviest general precipitation. <br />The Manitou Springs area is subject to a meteorological phenomenon <br />known as cloudbursts. They are confined chiefly to the eastern <br />foothill regions below an elevation of 7,500 feet and extend <br />eastward toward the plains for a distance of approximately <br />50 miles. Cloudbursts develop when there is a marked range in <br />temperature within a relatively small area and occur in the <br />afternoon or early evening of an unusually warm day. Cloudbursts <br />are characterized by rainfall of great intensity confined to a very <br />small area and lasting a short time. These storms have rarely <br />occurred where precipitation could be measured at a weather <br />station. In the Manitou Springs area, the peak discharge from a <br />cloudburst is greater than that caused by rainfall during a period <br />of snowmelt. <br /> <br />. <br /> <br />Vegetation varies throughout the study area. In areas above the <br />timberline, vegetation is sparse. In the timber and woodland <br />areas, aspen, oak brush, spruce, juniper, and native grasses are <br />found. <br /> <br />The soils in the study consist mainly of sandy to clayey material <br />with a high percentage of rock fragments. Rock outcropping occurs <br />on approximately 40 percent of the area and consists mainly of <br />crystalline and sedimentary rocks. The depth to the bedrock is <br />usually shallow. <br /> <br />2.3 Principal Flood Problems <br /> <br />Man-made and natural obstructions' in the floodplains impede the <br />flow of water, creating a backwater effect and increasing flood <br />heights. These obstructions in Manitou Springs take the form of <br />trees, brush, and numerous footbridges and planked crossings <br />throughout the study area. This material is carried downstream to <br />create dams at bridges and in areas where the channels are <br />restricted by building foundations and other forms of encroachment. <br /> <br />. <br /> <br />Severe flooding has occurred several times in Manitou Springs. In <br />July 1882, a cloudburst in the city caused flooding on Fountain <br />Creek, Williams Canyon, and Ruxton Creek. A wall of water came <br />down Williams Canyon and flooded Fountain Creek and the lower part <br />of Ruxton Creek. Most houses in the area sustained some damage and <br />one person was killed in Williams Canyon. Hailstones were found to <br />be 11 inches in circumference (Reference 4). <br /> <br />. <br /> <br />In May 1894, a rainstorm of several days' duration caused flooding <br />in the area; however, flood heights were not as high as they could <br />have been, had much of the precipitation not fallen as snow. <br />Fountain Creek, Ruxton Creek, and Williams Canyon all flooded. <br />Canon Avenue was described as a mountain torrent with hundreds of <br />tons of rock washing down (Reference 5). <br /> <br />5 <br />