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<br /> <br />. <br /> <br />The headwaters of Lefthand Creek are at somewhat lower ele- <br />vations than those of St. Vrain Creek. The highest point in the <br />Lefthand Creek drainage basin is Bald Mountain, elevation 11,453 feet. <br />The reach above the foothills is a steep canyon but the reach between <br />the foothills and Longmont has moderate slopes. Lefthand Creek, <br /> <br />in and for some distance above the study area, has a well-defined <br /> <br />main channel and wide, flat, overflow plains, similar to the Plains <br /> <br /> <br />part of St. Vrain Creek. There are several diversions from and <br /> <br /> <br />into Lefthand Creek in the Plains reach. <br /> <br /> <br />The drainage area of Lefthand Creek at the point it enters the <br /> <br /> <br />Plains region is about 48 square miles; at U.S. Highway 287 at <br /> <br /> <br />Longmont, 74 square miles. <br /> <br />Dry Creek is tributary to St. Vrain Creek just upstream from <br /> <br />the mouth of Lefthand Creek. The drainage area at the mouth is <br />14.8 square miles, all within the Plains region. The drainage areas <br />of the other two or three tributaries in the study area are fractions <br /> <br />of a square mile. <br /> <br />I <br /> <br />In Study Area <br />St. Vrain Creek <br />The rate of fall of St. Vrain Creek in the study area is about <br />19 feet per mile. The well-defined main channel is bordered by wide <br />flood plains that are in some cases lower than the banks of the main <br /> <br />channel. The banks and bed of the main channel are alluvial material, <br /> <br />principally coarse gravel with a few cobbles. There is a wide variation <br /> <br />. <br /> <br />4 <br /> <br />