FLOOD04309

• County: Eagle
• Community: Eagle County
• Stream Name: Stone Creek
• Basin: Colorado Mainstem
• Title: Flood Hazard Identification Report - Stone Creek, Eagle County, Colorado
• Date: 9/1/1986
• Prepared For: Eagle County
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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HYDROLOGIC AND HYDRAULIC DETERMINATIONS

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History of Flooding

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Flooding along Stone Creek has not been documented. It is likely,
however, that floods occured when Beaver Creek flows were particularly
high. Beaver Creek is an adjacent drainage basin, immediately to the
west of Stone Creek basin, with a drainage area of approximately 16
square miles. A gage near its mouth recorded relatively high streamflows
during 1983, 1978, and 1984 (in order of magnitude) during its record
since 1974. All of these peak flows occured in the month of June.

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Flood Characteristics

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All of the highest peak flows in the adjacent basin of Beaver Creek
in its record of 1974-1984 occured during the month of June. This
indicates snowmelt ruhoff as the probable cause of the largest floods in
Stone Creek basin.

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Hydrologic Analysis

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The 100-year peak flow on Stone Creek was obtained through use of a
regional discharge versus drainage area curve for the Eagle River basin
area (Ref. 4). The regional curve was derived through a statistical
analysis of records of 18 streamflow gages in the Eagle County area as
well as other data. A 100-year peak flow of 250 cfs was calculated by
this method.

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Peak flows for other recurrence intervals are also based on the regional
relationship curves. Estimated peak discharges for Stone Creek at the
mouth are summarized below.

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Peak Flows for Stone Creek at its Mouth

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Recurrence Interval
(years)
10
50
100
500

Peak Discharge
(cfs)
160
205
250
420

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A plot of the frequency-discharge curve is shown in Figure 1.

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It should be noted that the engineering consulting firm of KKBNA
(the engineer for the subdivision) had previously estimated a 100-year
peak flow of nearly 700 cfs in their drainage calculations for the Stone
Creek basin. An examination of the backup calculations deriving this
flow revealed a serious error in the estimation of one of the hydrologic
parameters. The effect of this error was that the re-routed channel was,
in most cases, oversized when it was designed.

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