FLOOD07444

• Designation Number: 387
• County: Summit
• Community: Frisco
• Basin: Colorado Mainstem
• Title: Flood Insurance Study - Frisco, CO, Summit County
• Date: 11/1/1994
• Designation Date: 11/1/1994
• Floodplain - Doc Type: Floodplain Report/Masterplan

The peak flow rates used in this study were either taken directly
from previous Flood Insurance Studies or other studies, derived
from other frequencies using log-probability plots, or calculated
using regression equations from previously referenced studies
(for small basins regression lines were adjusted to consider
rainfall effects).

The peak discharge-drainage area relationships for Miners Creek,
Jug Creek, and No Name Creek are shown in Table 3.

The revised hydraulic analyses of the streams studied using
detailed methods, were performed using the U.S. Army Corps of
Engineers HEC-2 step-backwater program (Reference 15).

Starting water-surface elevations (SWSELs) for the following
streams were calculated using the slope-area method: Tenmile
Creek (lower portion), Meadow Creek, and Miners Creek. The
SWSELs for Tenmile Creek (upper portion), and Meadow Creek (upper
portion) were chosen from contiguous studies. The SWSELs for Jug
and No Name CreeKs were chosen based on coincident peaks.

Cross sections were obtained through field surveys, existing
topographic maps, and/or previous HEC-2 input data as follows:

Tenmile Creek

Jug Creek
No Name Creek

Survey, Topographic Maps,
and HEC-2 data
Survey, Topographic Maps,
and HEC-2 data
Survey, Topographic Maps,
and HEC-2 data
Topographic maps
Topographic maps

Meadow Creek

Miners Creek

Channel roughness factors used in the hydraulic computations were
chosen by engineering judgment and based on field observations of
the streams and floodplain areas. The ranges of "n" values for
the streams in this 3tudy are as follows:

Stream Name

Channel

Overbank

Meadow Creek
Miners Creek
Tenmile Creek
Jug Creek
No Name Creek

0.025-0.080
0.060-0.l00
0.040-0.100
0.035-0.045
0.030-0.040

0.035-0.200
0.lOO-0.150
0.060-0.160
0.040-0.050
0.040-0.050

The split flow option of HEC-2 was used to determine the quantity
of flow leaving the channel banks of Tenmile Creek that cause the
corresponding shallow flooding. The depths associated with this
flooding were determined using Manning's "n" equation.

A floodway was not computed for portions of Meadow Creek, since
it is not appropriate due to the Wetland Habitat of the area.

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