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<br />Flood of 22 June 1941. The maximum peak discharge on St. Vrain Creek at Lyons is <br />10,500 cfs on 22 June 1941. lillie information is readily available on this flood except that <br />it originated mostly on South St. Vrain Creek and that it peaked rapidly at Lyons.,. It is <br />assumed that an extremely localized cloudburst occurred over South St. Vrain Creek a <br />short distance upstream from Lyons and that minor bank overflows occurred in rural areas <br />upstream from Longmont. <br /> <br />I' <br /> <br />Flood of 4 June 1949. SI. Vrain Creek peaked at 2,970 cfs at Lyons on 4 June 1949. <br />The creek was out of its banks most of the month of June due to heavy and prolonged <br />rainfall and unusually heavy snowmelt runoff. Sixteen bridges were damaged and out of <br />use, with two completely destroyed. Irrigation headworks were extensively damaged. In <br />Longmont, 10 homes and 5 businesses were flooded, <br /> <br />Flood of 3 August 1951. Heavy rain occurred in the SI. Vrain Creek basin during the <br />afternoon and night of 3 August 1951. Lyons received 6.3 inches from a cloudburst that <br />began about 6 p.m. Flooding resulted in the reach from Lyons to the mouth of SI. Vrain <br />Creek. Flood duration was less than 12 hours. The peak discharge at Lyons was 3,700 <br />cfs and at a point 7 miles of Longmont was estimated at 6,200 cfs, Railroad and highway <br />bridges near Longmont were severely damaged. Farmers in the 51. Vrain valley lost much <br />grain already shocked in the fields. <br /> <br />Flood of 9 May 1957. During the night of 8 and 9 May, approximately 3to 5 inches of <br />rain fell over the entire basin of 51. Vrain Creek. The rain began about 10 p.m. and <br />stopped about 6 a.m. with 51. Vrain Creek peaking at Lyons about 1 a.m. on 9 May at <br />3,060 cfs. A peak of 9,450 cfs reached the Mouth of the creek at 12:15 a.m. on 10 May. <br />Irrigation diversion works and bridges between Lyons and Longmont were damaged or <br />destroyed. <br /> <br />Flood of May and June 1969. Heavy rainfall combined with snowmelt runoff caused <br />prolonged high flows on 51. Vrain Creek. The worst flooding occurred on 7 and 8 May and <br />from 15 to 21 June. Roads and bridges along the stream were extensively damaged, <br />stream banks were eroded, farmlands were flooded. The peak discharge at Lyons was <br />2,900 cfs on 7 May and at the creek mouth, 10.300 cfs on 8 May. <br /> <br />4.7 DRY CREEK <br /> <br />Flood Historv. Little information is available relative to historic flooding on Dry Creek <br />probably because of its rural nature which has resulted in little flood damage during flood <br />events. Information is available, however, on adjacent streams which indicate that <br />floodwater may have been experienced on Dry Creek. The following are accounts of some <br />of the heavy rainfall events which have occurred in the Dry Creek area. <br /> <br />Colorado Fwod <br />Hydrology Manual <br /> <br />4.11 <br /> <br />ffiIJFr <br />