FLOOD10171

• Designation Number: 218
• County: Boulder
• Community: Unincorporated Boulder County
• Stream Name: Lower Boulder Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Lower Boulder Creek - Valley View Road to Boulder Weld County Line
• Date: 3/1/1983
• Designation Date: 7/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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FLOOD OF 1-2 June, 1914

This flood was caused by rainfall on 1 June of more than I-inch in the North
Boulder Creek basin near Silver Lake at an elevation of 10,200 feet, thus
hastening the mountain snowmelt. The flood, described as the worst since
1894, washed out numerous bridges between Colburn Mill and Boulder Falls.
Several hundred feet of main line for Boulder's water system were destroyed.
The peak discharge in Boulder was estimated at 5,000 cubic feet per second.

electric Plant located about three miles up the canyon from Boulder. Precipi-
tation amounts totaled 8.11 inches at E1dorado Springs and 10.05 inches at
Gross Reservoir on South Boulder Creek. Peak flooding occurred on the 7th of
May on both Boulder and South Boulder Creeks. Estimates of discharge at the
Orode11 gage indicate a peak of 1,220 cfs. In Boulder, local inflow increased
the Boulder Creek discharge to an estimated 3,000 cfs. The peak discharge on
South Boulder Creek at E1dorado Springs was 1,690 cfs. Flooding below the
confluence of these two streams extended over large portions of the floodplain.

FLOOD OF 2-7 June. 1921

Little is known of this flood except that it produced the highest peak dis-
charge ever recorded at the U.S. Geological Survey Orode11 gage, located about
three miles upstream from Boulder and one mile upstream from Fourmile Creek.
The Orode11 gage has been continuously operated since 1916. A discharge of
2,500 cfs was recorded on 6 June, 1921. Rainfall totaled 3.36 inches at
Boulder through the period of 2-7 June, 1921.

FLOOD OF 3 September, 1938

A large storm system produced general rains over all of eastern Colorado.
The largest amount of precipitation occurred in the mountains where over 6
inches was reported west of E1dorado Springs. Boulder reported 3.62 inches
of precipitation from 31 August to 4 September with 2.32 inches falling on 2
September. E1dorado Springs located in the South Boulder Creek basin had 4.42
inches of rainfall. A maximum discharge of 4,410 cubic feet per second
occurred near the mouth of Boulder Creek at noon on 3 September.

FLOOD OF 4-8 May, 1969

The flood of May 1969 resulted from a long duration storm. Runoff resulted
from a combination of rainfall and snowmelt which was reported heaviest in the
mountains. In the Boulder and South Boulder Creek basins, the rainfall con-
tinued at a moderate rate for nearly four days. Total precipitation for the
storm amounted to 6.60 inches at Boulder and 9.34 inches at the Boulder Hydro-

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