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<br />The absence of any paleoflood evidence of large floods in the upper <br />Big Thompson River basin indicates that such floods have not occurred <br />during post-glacial times. The landforms and deposits from such events are <br /> <br /> <br />sufficiently well-known that, if such evidence existed, it would have been <br /> <br /> <br />recognized (e.g., Helley and La Marche, 1973). The 1982 Lawn Lake Dam-break <br /> <br /> <br />flood in the Big Thompson River had a peak discharge of 5,500 cubic feet <br /> <br /> <br />per second (156 cubic meters per second) at Estes Park and left identi- <br /> <br /> <br />fiable flood deposits in the valley. Because similar flood deposits have <br /> <br /> <br />not been found above 7,500 feet (2,300 meters), except for glacial outwash <br /> <br /> <br />and dam-break floods, there does not seem to have been any floods that had <br /> <br /> <br />flows greater than 3,000 to 5,000 cubic feet per second (85 to 142 cubic <br /> <br /> <br />meters per second) during the last 8,000 to 10,000 years. <br /> <br />Big Thompson River at Mouth of Canyon, near Drake <br /> <br />This site is located at the base of the foothills where the river <br /> <br />flows out onto the plains of Colorado. The elevation at the site is 5,300 <br /> <br />feet (1,615 meters). The drainage area of the site is 305 square miles <br /> <br />(790 square kilometers). This site is about 17 miles (29 kilometers) <br />downstream from Estes Park. <br /> <br />011 <br /> <br />