FLOOD04241

• County: Broomfield
• Community: Broomfield
• Stream Name: Nissen Res., City Park, Gay Res., West Lake Basins
• Basin: South Platte
• Title: Flood Hazard Area Delineation
• Date: 6/1/1979
• Prepared For: UDFCD
• Prepared By: Wright-McLaughlin Engineers
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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4

SECTION II

BASIN DESCRIPTIONS

All of the subject drainage basins are located within the cities of Broom-

field and Westminster in Township 1 South, Range 68 and 69 West of the

6th P,M., and all are tributary to Big Dry Creek, Each basin has been

divided into subbasins to facilitate hydrological analysis, as indicated in

Figures I I -1 through I I -4. Pertinent data, such as subbasin size, average

slope, and percent impervious is compiled in tabular form accompanying each

basin figure (see Tables I I -1 through I I -4), Specific flooding problems

in each basin are described in Section IV of this report,

streets, and in the vicinity of the mobile home park located upstream from
Perry Street.

Designated as Direct Flow Area 3207 under Project REUSE by the Denver Re-
gional Council of Governments and the Urban Drainage and Flood Control
District, the drainage basin is rapidly being developed. A Master Drainage
Plan has been prepared for the basin by Wright-McLaughlin Engineers and
preliminary major drainageway design is scheduled to begin following review
of the master plan report by the City of Broomfield.

CITY PARK BASIN (FIGURE I I -I)
The City Park Basin is a highly urbanized drainage basin encompassing 1,785
acres, the majority of which form the downtown area of the City of Broom-
field. The channel flows in a southeasterly direction, traversing City
Park, and parallels West 120th Avenue before joining with the Nissen Reser-
voir Basin channel just west of Lowell Boulevard, Business and industrial
development exists near the primary transportation arteries such as U.S, 36,
U,S. 287, and West 120th Avenue, while residential development surrounds the
linear City Park, Areas which remain to be developed are the northwest and
southeast sections of the basin.

WINDMILL BASIN (FIGURE 11-3)

The Windmill Basin is a relatively small (370 acres) drainage basin that

is presently undeveloped. Flow is from west to east into Big Dry Creek,

but a defined channel does not exist other than local ditches adjacent

to the sewage treatment plant access road, The basin is bisected by Lowell

Boulevard, which also forms the boundary between the cities of Broomfield

and Westminster and Adams County. Present zoning for the basin calls for

residential planned unit development west of Lowell Boulevard and industrial/

commercial planned unit development east of Lowell Boulevard.

NISSEN RESERVOIR BASIN (FIGURE 11-2)

The Nissen Reservoir Basin is the drainage outfall for a 1,660-acre basin.

Approximately 30 acres of the basin are within the City of Westminster,

between Lowell Boulevard and Big Dry Creek, and the remainder of the basin

is in the City of Broomfield. The basin is approximately 40 percent de-

veloped, wi th pr imari ly s i ngl e-fami ly res i dent ia I and some commerci a I

and industrial development. A single tributary drains the area surrounding

and including Nissen Reservoir, and combines with the main stream at a point

east of Main Street and north of 10th Avenue. Major transportation routes

through the basin are Main Street and Lowell and Sheridan boulevards in

the north-south direction, and East 10th Avenue and Midway Boulevard in

the east-west direction, Floodplain encroachment is evident in the lower

part of the basin, particularly along 7th Avenue between Birch and Ash

GAY RESERVOIR BASIN (FIGURE I I -4)
The drainage basin serving Gay Reservoir is presently undeveloped, except
for the subbasins west of Sheridan Boulevard, which have been developed as
single and multifamily residential areas, The basin between Sheridan and
Lowell boulevards Ties within unincorporated Adams County, except for a
small portion downstream from Gay Reservoir which lies within the City of
Broomfield, Residential development plans are currently underway for the
area west of Lowell Boulevard and south of West 128th Avenue (Subbasin 15).
The remainder of the basin (Subbasins 16, 17, and 18a) lies within Adams
County and is presently agricultural,

\~EST LAKE BASIN (FIGURE II -4)
Most of the West Lake Basin lies within the City of Broomfield, except
for the residential area west of Lowell Boulevard along Carbon Road