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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each stream reach. Cross sections used for the backwater analysis
of Fountain Creek downstream of the Road to the Cave of the Winds
werll furnished by the COE from the Flood Plain Information report
for the area published in 1974 (Reference 4). For Fountain Creek
and Sutherland Creek, supplemental cross sections were developed
from topographic maps at a scale of 1:1,200, with contour intervals
of 4 and 20 feet (Reference 12). All bridges, culverts, and other
hydraulically significant structures were field checked to obtain
elevation data and structural geometry.

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Locations of selected cross sections used in the hydraulic analyses
are shown on the Flood Profiles (Exhibit 1). For stream segments
for which a floodway was computed (Section 4.2), selected cross
section locations are also shown on the Flood Insurance Rate Map
(Exhibit 2).

Roughness factors (Manning's "n") used in the hydraulic
computations for Sutherland Creek, Williams Canyon, Ruxton Creek,
and Beckers Lane Tributary were chosen by engineering judgment and
based on field observations of the streams and overbank areas.
Roughness factors for the main channels ranged from 0.020 to 0.035,
and overbank factors ranged from 0.035 to 0.100 for floods of the
selected recurrence intervals. Roughness factors from Fountain
Creek downstream of the Road tO,the Cave of the Winds were supplied
by the COE (Reference 4) and ranged from 0.020 to 0.040 for the
main channel and from 0.050 to 0.100 for the overbank areas for
floods of the selected recurrence intervals.

Starting water-surface elevations for the streams studied in detail
were determined using the slope-area method or a critical depth
elevation.

Flood profiles were drawn showing computed water-surface elevations
to an accuracy of 0.5 foot for floods of the selected recurrence
intervals (Exhibit 1).

~

Generally, the distances on the flood profiles correspond to
distances measured along the centerline of the designated
watercourses. Along Williams Canyon, however, the low-flow is
carried through an 1, 100-foot, concrete box culvert under Canon
Avenue near to the confluence with Fountain Creek. In this area,
the divergence of the .low-flow drainage necessitated the use of
distances measured along the centerline of the 100-year flow path.
On the maps, this flow line, used to establish profile distances,
is delineated and labeled as the Profile Base Line.

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The hydraulic analyses for Sutherland Creek, Williams Canyon,
Ruxton Creek, and Beckers Lane Tributary are based on unobstructed
flow. The flood elevations shown on the profiles are thus
considered valid only if hydraulic structures remain unobstructed,
operate properly, and do not fail.

The hydraulic analysis for Fountain Creek as developed by the COE
is based on an assumption of limited clogging. The COE considers

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