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<br />dangerous." The peak discharge at Lyons was 2.020 cfs on 7 June which was not <br />indicative of condnions at Longmont becauSB of heavy rains downstream of Lyons. <br /> <br />Flood of Seote!mber 1938. The flood of Septerrber 1939 was confined mostly to rural <br />areas downstream of Longmonl. <br /> <br />~ <br /> <br />Flood of 22 June 1941. The maximum peak discharge on SI. Vrain Creek at Lyons is <br />10.500 cfs on 22 June 1941. Little information is readily available on this flood except that <br />n originated mostly on South SI. Vrain Creek and that n 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 />! <br /> <br />Flood of 4 June 1949c SI. Vrain Creek peaked at 2,970 cfs at Lyons on 4 June 1949. <br />The creek was (Iut of ns banks most of thB month of June due to heavy and prolonged <br />rainfall and unusually heavy snowmelt runoft Sixteen bridges were damaged and out of <br />use, wnh two completely destroyed. Irrigation headworks were extensively damaged. In <br />Longmont, 10 homes and 5 businesses were flooded. <br /> <br />Flood of 3 Auaust 1951. Heavy rain occurred in the SI. Vrain Creek basin during the <br />afternoon and ni!~ht 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 />Creekc 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 St. Vrain valley lost much <br />grain already shc)cked in the fieldsc <br /> <br />Flood of 9 M~lv 1957. During the night of 8 and 9 May. approximately 3 to 5 inches of <br />rain fell over tho entire basin of St. Vrain Creek. The rain began about 10 pcm and <br />stopped about 6 a.m. wnh SI. 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 divers"," works and bridges between Lyons and Longmont were damaged or <br />destroyed. <br /> <br />Flood of Mall and June 1969. Heavy rainfall combined wnh snowmelt runoff caused <br />prolonged high flows on St. 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 wl~re eroded, farmlands were flooded. The peak discharge at Lyons was <br />2,900 cfs on 7 May and at the crBek mouth, 10.300 cfs on 8 Mayc <br /> <br />. <br /> <br />. <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />4.16 <br /> <br />fR'!FT <br />