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<br />I <br />I <br />I <br />r <br />I <br /> <br />. <br /> <br />. . <br /> <br />, <br /> <br />l <br />l <br /> <br />- <br /> <br />HISTORY OF FlOOOING <br /> <br />4June1949-0n4June1949, LefthandCreekhadoverbankfloodingdS <br />a result of heavy and prolonged rainfall during 1ate May and early June <br />and the runoff from an unusually heavy snow blanket. T!leprolongedhigh <br />flow on Lefthand Creek caused minor damages to irrigation headworks, <br />bridges, and farmlands. The gaging station near Boulder, Colorado <br />recorded a peak discharge of 1,140 cubic feet per second during the flood <br />period. <br /> <br />Scattl:red data from urroffichl SOUN:es and limited records indicate <br />significant flooding occurred in 1864, 1876, 1894, 1921, 1938, 1949, <br />1951,1969. and 1973 (Reference 1). The following are descriptions of <br />some these floods. <br />A detalled flood history of the county, prepared by Boulder County, <br />will be published in the near future. That publication will contain more <br />detailed information than given here. <br /> <br />3 AUQust 1951. During the afternoon and night of 3 August, a heavy <br />rainstorm occurred over the front range and foothills east of the <br />Continent<ll Divide from the vicinity of Boulder to near Fort Collins, <br />Colorado, <l distance of approximately 50mlles. One of the storm centers <br />was in the lefthand Creek baSin near the town of Niwot,.Colorado. At <br />this storm center, total precipitatonwas unofficially reported to have <br /> <br />2 - 6 June 1921. This storm produced general rains over the $outh <br />Platte River basin with the greatest amounts '1long the foothills. The <br />storm covered an <lrea of approximately 520 square miles and lasted five <br />days. The maximum recorded rainfall was 5.29 inches and the greatest <br />recorded rainfall intensity was 4.3 inches in six hours at longmont. <br />This flood was produced by a cOlllbin'1tion of rainfall and snowmelt. <br />Although this storm caused overbank flooding, neither discharges nor <br />damages were recorded. <br /> <br />been over 6 inChes. Th, runoff from this storm caused flooding 00 It. <br />Vrain Creek ood 00 'e. tributaries, D', Creek ,"d lefthand Creek. <br />Overbank flows occurred along ~" of th, length of Lefthand CreeL <br />Bridges, roads, crops, and irrig'1tion structures were damaged. <br /> <br />3 September 1938- During this storm, Showers were general over the <br />Lefthand Creek basin accompanied by isolated cloud bursts along the <br />foothills and the lower elevations. A maximum peak dhch'1rge of 812 <br />cubic feet per second was reCOrded '1t the U.S. Highway 287 gaging station <br />near Longmont, Colorado. This gaging station was not inoperationdurin9 <br />the 1949 and 1951 floods. <br /> <br />4.8 May 1969. Heavy rainfall with a relatively long duration <br />occurred from 4 May until 8 May. The storm covered an area along and <br />near the eastern slopes of the Rocky Mountains and e~tended into portions <br />of the high plains. The heaviest amounts were centered 25 miles <br />southwest of Denver and e~tended in a bank along the foothills of the <br />Rocky Mountains northward to Estes Park. Rainfall amounts to 7.60 inches <br />were reported at Boulder, Colorado. <br /> <br />4 <br />