FLOOD01680

• Designation Number: 126
• County: Boulder
• Community: Unincorporated Boulder County
• Stream Name: St. Vrain Canyon upstream of Lyons
• Title: Floodplain Information Report - South St. Vrain Canyon upstream of Lyons, Boulder County, CO
• Date: 2/1/1978
• Designation Date: 1/1/1979
• Floodplain - Doc Type: Floodplain Report/Masterplan

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HISTORY OF FLOODING

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There are no existing or authorized flood control structures in the
study area and none are under investigation.

St. Vrain Creek is known to have a long history of floods. Large

floods occurred in 1864, 1876, 1894, 1919, 1941, 1949, 1951, 1957 and

1969. Peak flood discharge and stages at Lyons during the period of

record are presented in Table 2 (references 5, 6, 7 and 9).

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and a bridge is destroyed, or abutments and approaches eroded and road-
beds damaged.

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Table 2
Historical Flood Peak Dischar~es and Sta~es
St. Vrain Creek at Lyons Gage
(Drainage Area = 212 square miles)

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Peak Discharge Stage
Year Date (ds) (ft.)
1894 May 31 9,800 8.13
1919 July 30 9,400 7.90
1941 June 22 10,500 8.06
1949 June 4 2,970 4.95
1951 August 3 3,920 5.37
1957 May 9 3,060 5.97
1969 May 7 2,900 6.80

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In general, information on past floods is based on newspaper accounts,

interviews with long time residents of the area, and flow data published

in U.S. Geological Survey Water-Supply Papers and Surface Water Records

(references 5, 6, 7, 8 and 9). In the study area, information on past

floods is available only for the vicinity of Lyons, where population is

concentrated.

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The floods of June 1864 and May 1876 inundated much valley farmland and

caused severe damage. The flood of l1ay 1894 washed away 20 homes in

the lower part of Lyons. Peak discharge was later estimated to be

9,800 cubic feet per second, most of which came from South St. Vrain

Creek.

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Summaries of floods occurring in 1919, 1941, 1949 and 1951 are con-
tained in articles of the Lyons Recorder, below. Various
flood photographs are shown in Figures 1 through 5.

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