FLOOD00385

• County: Boulder
• Community: Boulder
• Stream Name: Boulder Creek
• Title: South Boulder Creek Interim Hydrology Study
• Date: 7/1/2000
• Prepared For: Boulder County
• Prepared By: Taggart Engineering Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

11-8

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details of these inflows. The westerly overflow at Baseline and Foothills,
element 335, can convey significant flows to the Wellman upstream of
Foothills. This flow can go down the Wellman (limited by the Foothills
culvert and downstream Wellman capacity), but can also overflow to Bear
Canyon Creek. Elements 333 and 334 (the Baseline and Foothills overflow
to Foothills) convey flows up to the capacity of the inlets and a 36 inch
storm sewer to the Wellman. For flows greater than storm sewer capacity,
flood waters drain mostly to Bear Canyon Creek.

The Wellman Ditch acts as a major collector channel for other West Valley
Overflow flow paths. The collected overflow flood waters in the Wellman
simultaneously discharge with a small flow to South Boulder Creek (200 to
500 cfs), then to spills, in rough order:

a) north to the golf course on the east side of 55th (element 390)
b) north to the subdivision immediately west of 55th (element 324) which
subsequently (element 323, Drawing 11 and element 1337, Drawing
7) splits twice again to the golf course and to the north (most of
which finds its way to Dry Creek Ditch No. 2 but could overflow some
to Boulder Creek)
c) north to the subdivision along Merritt Drive, which then drains to both
Dry Creek Ditch No.2 (West Valley Overflow) and Boulder Creek

A major portion of West Valley Overflow (element 320, Drawing 7) joins the
South Boulder Creek spill through the golf course (element 19061. The
combined spillage (element 1909) would move through the industrial and
commercial area toward the outfall Dry Creek Ditch No.2, which at this
location is a major flood conveyance.

SUMMARY CONTROL FEATURES

The direct flow control features starting at the Highway 36 main channel spill are
tabulated in Table 11-1, with annotation as to the relative effect on the overflow and
local drainage distribution. High [H] denotes a control that is a major influence on
overflow magnitude and drainage problems. Moderate [M] denotes control that
moderately affects the intensity of the overall problem and local flooding
characteristics. Lesser ILl denotes that the particular component or subsystem is
important to understanding characteristics of the system, but whose accurate
simulation may have only small effects on the overall performance and flood hazard
recognition.