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<br />dangerous,. The peak discharge at Lyons was 2,020 cfs on 7 June which was not
<br />indicative of condttions at Longmont because of heavy rains downstream of Lyons,
<br />
<br />Flood of Seotember 1938, The flood of September 1939 was confined mostly to rural
<br />areas downstream of Longmonl.
<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 />tt originated mostly on South SI. Vrain Creek and that tt 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 />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 tts 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, wtth 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 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 St. Vrain valley lost much
<br />grain already shocked in the fields,
<br />
<br />Flood of 9 Mav 1957, During the night of 8 and 9 May, approximately 3 to 5 inches of
<br />rain fell over the entire basin of SI. Vrain Creek, The rain began about 10 p,m, and
<br />stopped about 6 a,m, wtth 81, 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 Mav and June 1969, Heavy rainfall combined wtth 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 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 />Colorado Flood
<br />Hydrology Manual
<br />
<br />4,16
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<br />fRIJFT
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