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<br /> <br />; <br /> <br />between Lyons and Longmont, were so minor i~ the study area that <br />they attracted no notice in the press. <br />Lefthand Creek <br />Little is known of the flood history of Lefthand Creek, but <br />probably most noteworthy floods on St. Vrain Creek were accompanied <br /> <br /> <br />by floods (not necessarily of the same recurrence interval) on <br /> <br /> <br />Lefthand Creek. Follansbee and Sawyer (1948) quote the Boulder <br /> <br /> <br />Camera of June 2, 1894: <br /> <br /> <br />"*** Lefthand Creek is 300 yards wide a mile from Niwot /see <br /> <br /> <br />plate 1/. Old timers stated that this is the worst flood since <br /> <br /> <br />1864." <br /> <br /> <br />The greatest flood during the period of record (1927-42) at <br /> <br /> <br />the gaging station on Lefthand Creek at U.S. Highway 287 occurred <br /> <br /> <br />on September 2, 1938, as a result of heavy rains along the foot- <br /> <br /> <br />hills. The peak discharge of this flood was determined to be 812 cfs <br /> <br /> <br />by the Colorado State Egnineer. <br /> <br /> <br />INUNDATION BY ST. VRAIN AND LEFTHAND CREEKS <br /> <br />It should be recognized that absolute accuracy is not attainable <br />for involved hydraulic computations such as those that form the basis <br />for the results presented in this section of the report. Consequently, <br /> <br />the area inundated, depths of water, and water-surface elevations <br /> <br />shown are subject to some variation from the results given herein. <br /> <br />Methods of Computation and Assumptions <br /> <br />Methods used in computing the backwater effect of channel and <br /> <br />18 <br /> <br />