FLOOD03506

• County: Jefferson
• Community: Lakewood
• Stream Name: South Lakewood Gulch
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 8/1/1978
• Prepared For: Lakewood
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SECTION II
EXISTING BASIN DESCRIPTION

Overall average imperviousness in this subbasin is presently about 25 percent,

with a slope of about 4 percent. The existing development is uniformly dis-

tributed throughout the basin and consists of mostly single-family residential

developments. Most open areas have been zoned for residential development

in the future. One exception to this is the large open area between Kipling

and Garrison, which is zoned as a park.

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The South Lakewood Gulch drainage basin is located in Lakewood, Colorado, in

Township 4'South, Range 69 West of the 6th P.M. The basin has been divided

into five subbasins for the purpose of this study, as shown on the Title Sheet

of the Master Drainageway Plan drawings at the end of this report. Each

subbasin is discussed in detail below.

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SUBBAS I N (Headwaters to Addenb rooke Pond)
Subbasin is characterized by single family residential development upstream
of Kipling Street, accounting for about 80 percent of the total subbasin
area. The subbasin is about 1.2 miles long and about 0.2 miles wide. Over-
. . presented ,'n Table 11-1 for present and future con-
all impervIousness IS
ditions. The average slope is about 4 percent. A well-defined drainage
channel does not exist in this subbasin, except for a small swale just up-
stream of Kipling. Below Kipling, a portion of the Agricultural Ditch system
crosses the drainageway. The drainageway is a very wide, flat depression from
this point to the farm pond at the lower end of the subbasin. The culvert at
Kipling Street is a 72 x 44-inch pipe arch corrugated metal pipe (CMP) struc-
ture. A rainfall/runoff gauging station is located just upstream of Kipling
to measure runoff from the intensely developed area upstream. The Imler cn,!
of this subbasin (downstream of Kipling) is open farmland.

SUBBASIN 3 (Rockmont Ponds to pond near First Avenue and Balsam Street)

Subbasin 3 is characterized by considerable residential development covering

about 80 percent of the area. It is about two-thirds of a mile long, with

a small but well-defined channel traversing its length. Overall impervious-

ness is presented in Table 11-1. The average slope is about 2.5 percent.

The basin will be almost totally developed in the future.

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SUBBASIN 2 (Addenbrooke Pond to Rockmont Ponds)
bb .. tl undeveloped with resi-
Approximately one-half of this su aSln IS presen y
dential development interspersed with rural farmland. Overall imperviousness
T 1 II I Although the subbasin itself is about 1.3 miles
is presented in ab e -.
d . . 1 bout 0 8 m,'les long. The upper third
long, the major ralnageway IS on y a .
of the channel is a continuation of the wide, flat depression described at
the lower end of Subbasin 1, ending abruptly at Garrison Street. At this
point, a small inlet to the storm sewer system under Garrison Street carries
low flows, with any significant flows going over the street. The channel it-
self continues on the east side of Garrison Street, at a low point in the
street about 50 yards from the location of the upstream inlet. From this
point downstream, a small but well-defined channel carries the flows to the
box culvert at Alameda Boulevard and beyond to the lake at Rockmont College.

The main problem in this area is the obvious floodplain encroachment by

existing development. The channel, about 3 or 4 feet deep typically, makes

several right-angle turns while coursing through the residential area. In

addition, houses are adjacent to the channel for almost its entire length.

The only ~rea~ "here re~idential development is not evident at the present

time are at the extreme upper and lower ends of this reach. These reaches,

representing about 30 percent of the total reach length, are'zoned to be

developed in the future, thus potentially causing more encroachment. An

existing depression at the lower end of this subbasin would store some storm

runoff. The depression has no embankment, but rather is entirely below grade

with the outlet invert several feet below surface grade. The detention

storage effect of this existing depression is minimal for the larger flows.

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SUBBASIN 4 (Pond near First Avenue and Balsam Street to Wadsworth Blvd.)

This subbasin is totally developed at the present time, with an overall

imperviousness of about 40 percent, average slope in the basin is 2 percent

and the stream length is about 0.4 miles. About half the length of the

channel is a continuation of the 48-inch diameter pipe which outlets the

depression in Subbasin 3. The remaining channel, beginning at the crossing

of the Rocky Mountain Ditch near First Avenue, consists of a low, marshy

area extending to Wadsworth Boulevard.

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11-1