FLOOD03140

• County: Denver
• Community: Aurora, Denver
• Stream Name: Westerly Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation
• Date: 1/1/1977
• Prepared For: Aurora, Denver
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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8

Engineers' HEC-l Flood Hydrograph package computer program
was used to complete the flood routing. The flood discharges
and their corresponding frequencies at four locations in the
study reach are listed in the following table.

HYDRAULICS

Table 4
Flood Frequency and Discharge
Location 2-year 10-year 100-year SPF
(cfs) (cfs) (cfs) (cfs)
E. 11th Ave. 120 385 2950 10,000
\r
E. Colfax Ave. 690 1500 3000 ~~' 10,080
~.)
E. Montview ~
Blvd. 800 1730 3280 ~ 10,100
Westerly Creek 960 1480 2760 9,940
at Mouth

Hydraulic analyses of the study area were completed to deter-

mine the water surface elevations for the 2-, 10-, and 100-

year storm events and the Standard Project Flood. The eleva-

tions were 'compiled using the Corps of Engineers' HEC-2 Water

Surface Profiles computer program. Valley cross sections were

measured from left to right looking upstream on the I" = 100'

scale, 2-foot contour topographic mapping provided by the

District. A field investigation was conducted to determine

the channel and flood plain conditions, vegetative cover, and

roughness coefficients.

The outflow is 500 cfs with the water surface at the crest of
the emergency spillway of Kelly Pond.

Channel and Flood Plain

The natural Westerly Creek channel between 11th Ave. and

Stapleton International Airport has been almost completely

obliterated by development and encroachment so that there is

little or no flood plain remaining. The main channel of

Westerly Creek is a combination of open channel and drainage

structures of mixed construction, with little or no capacity

to receive even local tributary flows. In addition, many

reaches of the creek have not been maintained, and the open

channel sections are covered with brushes and lowland vegeta-

tions. Westerly Creek within this reach has capacity for less

than a I-year frequency storm event.

Flood discharges at E. 11th Ave. represent the outflow from
Kelly Pond for various flood frequencies based on the assumption
that the inflow is contributed from the total watershed above
Kelly Pond (Drainage Area No's. 1, 2, 4, 5 and 6).

Typical flood hydrographs for the 100-year frequency at these

four locations of the study reach are provided in Figures 1

and 2.

Westerly Creek continues with one 108-inch and one 63-inch

pipe under the east-west runways, at Stapleton International