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<br />The peak discharge of the St. Vrain at Lyons was 1650 cfs at 1:00
<br />AM on September 3, while the peak discharge at the mouth of the
<br />St. Vrain was estimated as 8,360 cfs at 6:00 PM the same day.
<br />Newspaper reports indicated that "scores" of families along the
<br />St. Vrain in the Longmont area were forced from their homes along
<br />the Creek by the high water. Two bridges on State Highway 52
<br />were also washed out and the bridge approaches damaged (Reference
<br />4) .
<br />
<br />Railroad and highway bridges near Longmont were also damaged.
<br />Farmers in the valley between Lyons and the mouth of the St.
<br />Vrain suffered crop losses as well (References 1, 2, 3, 5, 6).
<br />
<br />1951 FLOOD
<br />
<br />Three to five inches of rain fell on the entire St. Vrain basin
<br />during the night of May 8-9, 1957. The St. Vrain at Lyons peaked
<br />at 3,060 cfs about 1 pm on May 9, while the St. Vrain at the
<br />mouth peaked at 9,450 cfs at 12:15 am on May 10. Two bridges
<br />were destroyed. approaches to several bridges were washed out,
<br />and several irrigation diversion structures were damaged or
<br />destroyed (References 1, 2, 3, 4, 6).
<br />
<br />1941 FLOOD
<br />
<br />Cloudbursts occurred over both North and Sou th St. Vrain Creeks
<br />on June 22, 1941. Peak discharge at Lyons was estimated as
<br />10,500 cfs. A resident of Longmont was killed at his cabin in
<br />South St. Vrain Canyon by the flood. Three homes in the canyon
<br />were destroyed, and several homes in Lyons were flooded. Damage
<br />was reported to the roads in both North and South St. Vrain
<br />Canyons. The road damage, in conjunction with a bridge washout,
<br />caused the road in the South St. Vrain Canyon to be closed for
<br />several days. The "swinging bridge" in Lyons was also destroyed
<br />by the floodwaters (References 1. 2, 3, 4, 5, 6).
<br />
<br />1969 FLOOD
<br />
<br />Heavy rainfall combined with snowmelt to cause prolonged high
<br />flows On the St. Vrain. The worst flooding occurred on May 7-8,
<br />and June 15-21, 1969. Roads and bridges along the stream were
<br />extensively damaged, streambanks eroded, and farmlands flooded.
<br />The peak discharge at Lyons was 2,900 cfs on May 7. Peak
<br />discharge at the mouth was 10,300 cfs on May 8 (References 1, 2,
<br />3, 4, 6).
<br />
<br />1949 FLOOD
<br />
<br />Nearly 3 inches of rain which fell in the St. ,Vrain valley on
<br />June 4, 1949 caused the St. Vrain to peak at 2,970 cfs at Lyons.
<br />Peak discharge reached approximately 6,700 cfs at Longmont. All
<br />bridges between Longmont and Lyons were either impassable or
<br />under close watch by State Highway Department crews, while two
<br />bridges were destroyed entirely. Thirty-five people were
<br />evacuated from the St. Vrain floodplain. The road in the South
<br />St. Vrain canyon was closed as a precautionary measure. The
<br />Burlington Northern Railroad track to Lyons was also rendered
<br />useless as floodwaters had destroyed the roadbed east of Lyons
<br />(References 1, 2, 3, 5, 6).
<br />
<br />Following are selected newspaper headlines and articles dealing
<br />with several of the major floods along the St. Vrain. These
<br />newspaper accounts were taken from the Camp. Dresser, McKee, Inc.
<br />report (Reference 5) and from the Water Resources Consultants,
<br />Inc. report (Reference 4). The Colorado Water Conservation Board
<br />and Boulder County supplied the historical photographs.
<br />
<br />1951 FLOOD
<br />
<br />Heavy rains occurred in the St. Vrain basin during the afternoon
<br />and night of August 3, 1951. Lyons received 6.3 inches from a
<br />cloudburst which began about 6 p.m. Flooding resulted along the
<br />South St. Vrain, and along the reach from Lyons to the mouth of
<br />the St. Vrain. Floodwaters destroyed several sections of road in
<br />the South St. Vrain Canyon and inundated businesses in Lyons.
<br />
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