FLOOD10328

• County: Boulder
• Community: Lyons
• Stream Name: North Saint Vrain and Saint Vrain Creeks
• Title: Floodplain Information Report, North Saint Vrain Creek, Saint Vrain Creek, Floodplain Update, Town of Lyons, Boulder County, Colorado
• Date: 6/1/1998
• Prepared For: Lyons
• Prepared By: BRW, Inc
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Floodplain Information Report
K:\35600\004\FLOODPLAIN INFORMA nON REPORTdoc

11

June

998

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Following are selected newspaper headlines and articles dealing with several of the major
floods along the St, Vraino These newspaper accounts were taken from the Camp, Dresser,
MeKee, Inco report (Reference 5) and from the Water Resources Consultants, Inco report
(Reference 4). The Colorado Water Conservation Board and Boulder County supplied the
historical photographs.

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Heavy rainfall combined with snowmelt to cause prolonged high flows on the St. Vrain The
worst flooding occurred on May 7-8, and June 15-21, 1969. Roads and bridges along the stream
were extensively damaged, streambanks eroded, and farmlands floodedo The peak discharge at
Lyons was 2,900 cfs on May 7. Peak discharge at the4 mouth was 10,300 cfs on May 8
(References 1,2,3,4,6)

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1969 FLOOD

Three to five inches of rain fell on the entire St. Vrain basin during the night of May 8-9, 19570
The St. Vrain at Lyons peaked at 3,060 cfs about 1 pm on May 9, while the Str. Vrain at the
mouth peaked at 9,450 cfs at 12:15 am on May 10. Two bridges were destroyed, approaches to
several bridges were washed out, and several irrigation diversion structures were damaged or
destroyed (References 1, 2, 3, 4, 6)0

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1957 FLOOD

Railroad and highway bridges near Longmont were also damagedo Farmers in the valley
between Lyons and the mouth of the St. Vrain suffered crop losses as well (References 1,2,3,5,
6).

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Heavy rains occurred in the Sto Vrain basin during the afternoon and night of August 3, 1951.
Lyons received 6.3 inches from a cloudburst which began about 6 pom. Flooding resulted along
the South St. Vrain, and along the reach from Lyons to the mouth of the St. Vraino Floodwaters
destroyed several sections of road in the South St. Vrain Canyon and inundated businesses in
Lyonso

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1951 FLOOD

Nearly 3 inches of rain which fill in the St. Vrain valley on June 4, 1949 caused the St. Vrain to
peak at 2,970 cfs at Lyons. Peak discharge reached approximately 6,700 cfs at Longmont. All
bridges between Longmont and Lyons were either impassable or under close watch by State4
Highway Department crews, while two bridges were destroyed entirely. Thirty-five people
were evacuated from the St. Vrain floodplaino The road in the South St. Vrain canyon was
closed as a precautionary measure. The Burlington Northern Railroad track to Lyons was also
rendered useless as floodwaters had destroyed the roadbed east of Lyons (References 1,2,3,5,
6).

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1949 FLOOD

North St. Vrain & St.
Floodplain Update

Vrain Creeks

Town of Lyons