FLOOD00576

• County: El Paso
• Community: Manitou Springs
• Stream Name: Fountain Creek
• Title: Flood Insurance Study - City of Manitou Springs
• Date: 8/19/1991
• Prepared For: Manitou Springs
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

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the computed skew, a regional skew of 0.4 was used in computations
of peak discharges and confidence limits. The COE frequency curve
falls within the 50-percent confidence interval of this more recent
study for recurrence intervals of greater than 30 years, while the
10-year flood is only slightly larger than the 0.25 limit. It was
concluded that the COE discharge for Fountain Creek at Manitou
Springs would be adopted for this study.

.

For Sutherland Creek, Williams Canyon, and Ruxton Creek, discharges
were determined using the regression equations described in Manual
For Estimatin2 Flood Characteristics of Natural-Flow Streams in
Colorado (Reference 7). The equations for the Plains Region were
applied to the portion of each drainage area below an elevation of
9,000 feet. Above an elevation of 9,000 feet, the equations for
the Mountain Region were applied. It was found that the Plains
Region portion of each drainage yields much higher discharges than
the Mountain Region portion. Consequently, the 10-, 50-, 100-, and
SOO-year flood discharges from the respective Plains Region
equations were used.

For Beckers Lane Tributary, discharges were determined using the
methodology out lined in the Draina2e Criteria Manual for Colorado
Springs and El Paso County (Reference ~). This manual requires the
determination of 2- and 24-hour storms using the Soil Conservation
Service method. The storm producing the most severe event for a
gi ven recurrence interval was selected. Final calculations were
carried out using the COE HEC-l hydrologic computer program
(Reference 9).

Peak discharge-drainage area relationships for Fountain Creek,
Sutherland Creek, Williams Canyon, Ruxton Creek, and Beckers Lane
Tributary are shown in Table 1.

The flood discharges for the upper portions
Tributary and williams Canyon were interpolated
area-discharge curve developed from computed
Williams Canyon and Sutherland Creek.

of Beckers Lane
from a drainage
discharges for

3.2 Hydraulic Analyses

.

Analyses of the hydraulic characteristics of
sources studied were carried out to provide
elevations of floods of the selected recurrence

flooding from
estimates of
intervals.

the
the

.

Water-surface elevations of floods of the selected recurrence
intervals were computed through use of the COE HEC-2 step-backwater
computer program (Reference 10).

Cross section data and additional fLoodplain data for Fountain
Creek upstream of the Road to the Cave of the Winds was obtained
from the Flood Insurance Study for the unincorporated areas of E1
Paso County (Reference 11).. Cross sections used for the backwater
analyses of Sutherland Creek, Williams Canyon, Ruxton Creek, and
Beckers Lane Tributary were obtained from detailed field surveys of

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