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<br />Scenes of past flooding in Longmont are shown in <br />Figures 2-9. The pictures were produced from the photo- <br />graphic records of The Longmont Daily Times-Call news- <br />paper. <br /> <br />2.4 Flood Protection Measures <br /> <br />There is little evidence of flood protection measures <br />along the study segment of St. Vrain Creek, except the <br />channelization between Sunset Street and the Colorado <br />and Southern Railroad Bridge. There also exists a line <br />of low levees along the trailer park on the south side of <br />this segment. Three dams exist in the upper, mountain <br />segments of the St. Vrain Creek. Button Rock Dam was <br />completed on North St. Vrain Creek in 1969, 6 miles west <br />of Lyons near the City of Longmont, to store the munici- <br />pal water supply. It was not designed to store flood- <br />waters but in the ~ay of 1969 flood, it reduced the <br />magnitude of the discharge that could have hit Longmont. <br />Both the Long~ont Dam, located I mile downstream of the <br />Button Rock Dam, and Beaver Reservoir, near the South <br />St. Vrain Creek headwaters, have no effect on the flood <br />discharge in Longmont. <br /> <br />Left Hand Creek has been channelized along the segment <br />from Pike Road (Colorado 22) to the mouth. The channel <br />from Pike Road to South Pratt Parkway is grass-lined and <br />flanked on either side by a grassed park and is designed <br />to contain a flow of about 3650 (cfs). From South Pratt <br />Parkway to the mouth of Left Hand Creek, the stream has <br />been channelized; however, the overbanks remain unimproved. <br /> <br />Various structural and nonstructural improvements such <br />as grass or concrete-lined channels, detention ponds, <br />and outfall culverts have been implemented on Spring <br />Gulch in the segment from 9th Avenue to 3rd Avenue. <br />These improvements are inadequate to contain even the <br />lO-year flood discharge. <br /> <br />- <br />~ <br /> <br />9 <br />