FLOOD09664

• Designation Number: 171
• County: Eagle
• Community: Minturn
• Basin: Colorado Mainstem
• Title: Flood Insurance Study - Minturn, Eagle County, Colorado
• Date: 3/1/1980
• Designation Date: 12/1/1980
• Floodplain - Doc Type: Floodplain Report/Masterplan

Table 1. Summary of Discharges

Flooding Source
and Location

Drainage Area
(Square Miles)

?eak Discharges
(Cubic Feet per Second)
IO-Year 50-Year IOO-Year 50G-Year

Eagle River
Downstream Corporate
Limits
Upstream Corporate
Limi ts

260

1925

2550

2800

3400

245

1900

2500

2700

3300

3.2 Hydraulic ~~a1yses

Analyses of the hydraulic characteristics of streams in the community
were carried out to provide estimates of the elevations of floods of
the selected recurrence intervals along each stream studied in the
community.

Water-surface profiles were computed for the 10-, 50-, 100-, and 500-
year flood events using the u.s. Army Corps of Engineers HEC-2 step-
backwater computer model (Reference 7).

Cross section data for the Eagle River were obtained from field
surveys. The field-surveyed cross sections were supplemented with
cross sections from topographic maps in areas of sparse development
(Reference 8)~ All bridges were surveyed to obtain elevation datu and
structural geometry.

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 is computed (Section 4.2), selected cross section
locations are also shown on the Flood Boundary and Floodway Map
(Exhibit 2).

Roughness coefficients (Mannings "n") for the Eagle River were esti-
mated by field inspection at each cross section~ The channel rough-
ness value was 0.040, and the overbank value was 0.070.

Starting water-surface elevations were obtained using the slope-area
method at a starting cross section 800 feet downstream of the Minturn
corporate limits. The computer model computed elevations at three
cross sections before reaching the corporate limits.

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