FLOOD04702

• Designation Number: 347
• County: Jefferson
• Community: Unincorporated Jefferson County
• Stream Name: Upper Lena Gulch
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Upper Lena Gulch
• Date: 1/1/1993
• Designation Date: 9/1/1993
• Floodplain - Doc Type: Floodplain Report/Masterplan

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II. BASIN CHARACTERISTICS

Channel slopes in the upper basin exceed 400 feet per mile. Channel slopes in the lower
portion of the basin average approximately 80 feet per mile, At its widest point the Upper Lena
Gulch basin is approximately 3,6 miles wide with an overall length of approximately 7 miles,

Studv Area Description

Lena Gulch has its headwaters in Apex Gulch on the southeast slopes of Lookout Mountain in

Golden, Colorado, From Lookout Mountain, the main stream flows northeast to its confluence

with Clear Creek downstream of Kipling Street in Wheat Ridge, Colorado,

The developed areas in the lower portion of the basin are primarily residential and commercial.

Some areas of light-industrial land use are also present An average of approximately 32

percent of the lower basin is impervious areas.

Drainaoewav Description

This study deals with the portion of Lena Gulch upstream of Maple Grove Reservoir. Figure 1
shows the study area location and the basin boundary, Upper Lena Gulch is located in
Jefferson County and portions of the cities of Golden and Lakewood, The mainstem is joined
by three major tributaries and several small drainages, This study includes evaluations of two
of the major tributaries, Apex Gulch and the Pleasant View tributary, The third major tributary,
the Green Mountain tributary, has been evaluated previously (Major Drainageway Planning
Green Mountain Area, UDFCD, 1978) and is not included as part of this study,

This study covers approximately 6.5 stream miles; 5,2 miles on the mainstem of Lena Gulch,
0,7 miles on the Pleasant View tributary, and 0,5 miles along Apex Gulch, The Upper Lena
Gulch basin above Maple Grove Reservoir consists of approximately 6,230 acres (9,73 square
miles) with a wide range of topographic features, Figure 2 shows the location and alignment of
the drainageways and the reach locations as used in this study,

The Apex Gulch tributary joins the mainstem of Upper Lena Gulch in the upper part of the basin

in the City of Golden just downstream of the U,S, Highway 93 crossing, The Pleasant View

tributary is located to the north of Lena Gulch on the south slopes of South Table Mountain, Its

confluence with Lena Gulch is downstream of South Golden Road on the property of the Camp

George West Military Reservation,

The main channel of Lena Gulch follows a northerly alignment along U,S. Highway 40 from near
the intersection with Interstate 70 to a point downstream where it joins with Apex Gulch and
crosses through a geologic formation known as the Hogback, The channel continues
downstream in an easterly direction crossing several streets and mixed residential and
commercial properties in the City of Golden until it empties into a rectangular concrete-lined
channel upstream of 6th Avenue, Downstream of 6th Avenue the channel continues
northeasterly through various residential and undeveloped properties in unincorporated
Jefferson County crossing several streets and then crossing under South Golden Road, Below
South Golden Road the channel crosses open space in Camp George West and is joined by

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