FLOOD06478

• County: Boulder
• Community: Boulder
• Stream Name: Skunk Creek
• Basin: South Platte
• Title: Request for LOMR
• Date: 1/1/1989
• Prepared For: Boulder County
• Prepared By: Love & Associates, Inc.
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

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Request for Letter of Map Revision - Skunk Creek
University of Colorado at Boulder Research Park
Page 5

the flood control channel. The downstream reach of the
channel, from the box culvert at Foothills to Station 13+00,
is designed to release flows along the left channel bank
(north) into the Boulder Creek floodplain. Only those flows
which are in excess of the box culvert's capacity under
Foothills Parkway will leave the improved channel. Hydraulics
of those flows which leave the channel are governed by the
road embankments of Foothills Parkway and Arapahoe Avenue.
This coincides with existing conditions in which flow through
the Foothills Parkway culvert is limited by outlet control
into Bear Canyon Creek.

The HEC-2 input/output for both the main channel and the
spill collection channel are included in Appendices 2 and 3.
Multiple profile runs have been provided using the 10-, 50-,
100- and 500-year discharge quantities listed in Table 1.

4.0 FLOODPLAIN MANAGEMENT APPLICATIONS

4.1 Floodplain Boundaries

Floodplain boundaries were determined using the U. S. Army
Corps of Engineers HEC-2 computer program. Flood elevations
and cross section geometries were determined using digitized
as-built topographic information as prepared by Geonex Delta
Aerial Surveys, Inc. The maps were prepared for the UCBRP
for channel design at 50 scale and 1 foot contour intervals
using national mapping standards. The date of the aerial
photography used to prepare this mapping is December 5, 1988.
The 100-year floodplain boundaries are contained within the
Skunk Creek Channel between design stations 13+00 and 32+55.
The improved channel spills into the Boulder Creek floodplain
between design stations 13+00 and 0+00 to match existing flow
conditions. Floodplain boundaries and flood profiles have
been tied to existing boundaries upstream and downstream for
the improved channel. Flood profiles for Skunk Creek are
included in this report (Figures 2A and 2B) .

4? Floodway

The floodway was previously determined for the Skunk Creek
study area in the FHAD (Ref. 3, 4). The revised floodway is
contained in the improved flood control channel and the
Boulder Creek f loodway. No encroachment on the channel is
expected. The floodway boundaries have been tied to existing
boundaries upstream and downstream for the improved channel.

Love & Associates. Inc.