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<br />North St. Vrain & St. Vrain Creeks
<br />Floodplain Update
<br />
<br />Town of Lyons
<br />
<br />1949 FLOOD
<br />
<br />Nearly 3 inches of rain which fill in the St. Vrain valley on June 4. 1949 caused the St, Vrain to
<br />peak at 2,970 cfs at Lyons, Peak discharge reached approximately 6,700 cfs at Longmont. All
<br />bridges between Longmont and Lyons were either impassable or under close watch by State4
<br />Highway Department crews, while two bridges were destroyed entirely. Thirty-five people
<br />were evacuated from the St. Vrain floodplain. The road in the South St. Vrain canyon was
<br />closed as a precautionary measure. The Burlington Northern Railroad track to Lyons was also
<br />rendered useless as floodwaters had destroyed the roadbed east of Lyons (References 1, 2, 3, 5,
<br />6),
<br />
<br />1951 FLOOD
<br />
<br />Heavy rains occurred in the St. Vrain basin during the afternoon and night of August 3, 1951.
<br />Lyons received 6.3 inches from a cloudburst which began about 6 p,m, Flooding resulted along
<br />the South St. Vrain, and along the reach from Lyons to the mouth of the St. Vrain. Floodwaters
<br />destroyed several sections of road in the South St. Vrain Canyon and inundated businesses in
<br />Lyons,
<br />
<br />Railroad and highway bridges near Longmont were also damaged. Farmers in the valley
<br />between Lyons and the mouth of the St. Vrain suffered crop losses as well (References 1, 2, 3, 5,
<br />6),
<br />
<br />1957 FLOOD
<br />
<br />Three to five inches of rain fell on the entire St. Vrain basin during the night of May 8-9, 1957,
<br />The St. Vrain at Lyons peaked at 3,060 cfs about 1 pm on May 9, while the Str. Vrain at the
<br />mouth peaked at 9.450 cfs at 12:15 am on May 10, Two bridges were destroyed. approaches to
<br />several bridges were washed out, and several irrigation diversion structures were damaged or
<br />destroyed (References 1, 2, 3, 4, 6),
<br />
<br />1969 FLOOD
<br />
<br />Heavy rainfall combined with snowmelt to cause prolonged high flows on the St, Vrain. The
<br />worst flooding occurred on May 7-8, and June 15-21, 1969, Roads and bridges along the stream
<br />were extensively damaged, streambanks eroded, and farmlands flooded, The peak discharge at
<br />Lyons was 2,900 cfs on May 7, Peak discharge at the4 mouth was 10,300 cfs on May 8
<br />(References 1,2, 3, 4, 6),
<br />
<br />Following are selected newspaper headlines and articles dealing with several of the major
<br />floods along the St, Vrain, These newspaper accounts were taken from the Camp, Dresser,
<br />MeKee, Inc. report (Reference 5) and from the Water Resources Consultants. Inc, report
<br />(Reference 4), The Colorado Water Conservation Board and Boulder County supplied the
<br />historical photographs,
<br />
<br />Floodplain Information Report 11
<br />K:\35600l004\FLOODPLAIN INFORMATION REPORT.doc
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<br />June 1998
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