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<br />The northern one-half of the plains area of Douglas County consists <br />of three basic soil types. Loamy and sandy soils exist on the <br />floodplains and terraces. The terrain in these areas is nearly <br />level to gently sloping to moderately steep, with sandy and <br />gravelly soils on the uplands. Vegetation is mainly grass, with <br />some Gambe1 oak, mountain mahogany, and ponderosa pine trees <br />(Reference 2). Most of the remaining area is gently sloping to <br />moderately steep, with loamy soils on the uplands. <br /> <br />2.3 Principal Flood Problems <br /> <br />Douglas County is located in an area that is subject to intense <br />rainfall, sometimes as c10udbusts. Floods have resulted from <br />. storms covering large areas with heavy general rainfall as well as <br />from storms covering small areas with intense rainfall. Floods <br />generally occur from May through August. The upland areas are <br />characterized by dissected topographic relief and steep stream <br />slopes. Floods are characterized by rapid rises, high maximum <br />discharges, short durations, and comparatively low volumes of total <br />runoff. <br /> <br />The roadways that cross streams and obstruct floodflows are the <br />most significant factor affecting flooding in the area. Other <br />manmade features, such as buildings, cars, and fences, as well as <br />the natural vegetation of the floodplains, cause flow obstruction. <br /> <br />The following accounts of flooding on Cherry Creek in the study <br />area are representative of typical floods for which information is <br />available. <br /> <br />Three floods occurred during May and June 1864. The first, <br />originating in the Cherry Creek and Plum Creek basins, occurred <br />during the nights of May 19-20, 1864, and was caused primarily by a <br />cloudburst in the upper part of those basins. On the morning of <br />May 20, the flood covered the lower portions of Denver with water <br />to depths of from 1 to 5 feet, leaving great deposits of sand and <br />gravel. <br /> <br />. <br /> <br />Records indicate that 2.08 inches of rain occurred during a 2-hour <br />period on July 14, 1912. The heaviest precipitation occurred <br />between Franktown and a point approximately 5 miles north of <br />Denver, with the center located near Parker. The rainfall started <br />at approximately 3 p.m. and continued until approximately 5 p.m. <br />Cherry Creek crested at approximately 10 p.m. and had a peak <br />discharge of 25,000 cubic feet per second (cfs) in Denver. The <br />Cherry Creek Flood Commission estimated that runoff occurred from <br />an area between Franktown and the site of the existing Cherry Creek <br />Dam and Resrvoir totaled $554,000. <br /> <br />. <br /> <br />A large storm mass moved into southeastern Colorado on August 25, <br />1945, and extended over the Cherry Creek basin. Unofficial <br />rainfall amounts varied from 2 to 5 inches. Severe flooding <br />occurred along Cherry Creek in the Franktown-Parker area. The <br /> <br />5 <br />