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Last modified
1/26/2010 10:08:49 AM
Creation date
10/5/2006 4:11:19 AM
Metadata
Fields
Template:
Floodplain Documents
County
Denver
Community
Denver
Stream Name
Marston Lake North
Basin
South Platte
Title
Major Drainageway Planning
Date
10/1/1979
Prepared For
Denver
Prepared By
UDFCD
Contract/PO #
&&
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />4 <br /> <br />II. EXISTING BASIN CONDITIONS <br /> <br />Marston Shores condominiums. At Marston Shores, high spots (saddles) <br />in the channel thalweg and adverse channel slopes cause stormwater <br />flows to overtop the Marston Lake berm during ten-year and greater <br />storms and to flow into Marston Lake. Upstream of Marston Lake and <br />east of Colorado State Highway 121 is the Marston Sump. This sump has <br />a storage capacity of approximately six acre-feet before overtopping <br />of the Old Wadsworth dirt road and has detained stormwaters in the <br />past. <br /> <br />The Marston Lake North drainage basin is located in the southwest <br />corner of the City and County of Denver. The basin has been divided <br />into three reaches for the purpose of this study. The limits of each <br />reach are as follows: Reach 1, Bear Creek to Quincy Avenue; Reach 2, <br />Quincy Avenue at Colorado State Highway 121(Wadsworth Boulevard); and <br />Reach 3, upstream of Colorado State Highway 121. Each reach is <br />discussed in detail below. <br /> <br />Reach 3: This reach is mostly privately owned, and contains the most <br />urban developed lands, existing and potential. A 84-inch culvert con- <br />veys stormwater under Colorado State Highway 121 embankment creates a <br />substantial storage area, and during the larger storm events the <br />culvert does not have sufficient capacity (approximate maximum flow <br />capacity is 450 cubic feet per second, 5-year storm) to convey all of <br />the stormwater through it without overtopping Colorado State <br />Highway 121. Upstream of the highway, a channel with 4:1 side slopes <br />connects to the embankment of Lakes Lake. Lakes Lake, before its <br />embankment was breached by the owners, had a detention storage of <br />approximately 50 acre-feet between elevations 5,568 and 5,570. These <br />elevations are the maximum level for irrigation and before over- <br />topping, respectively. Above Lakes Lake, a small channel with mild <br />side slopes continues to the vicinity of the Park West 3 subdivision. <br /> <br />Reach 1: The land ownerships along the drainageway include the City <br />and County of Denver, the United States Government and Pinehurst <br />Country Club. In the vicinity of Bear Creek Park, at Kenyon Avenue, <br />various culverts route drainage under Kenyon Avenue and into channels <br />through the park. These culverts are generally ineffective during <br />high flows, causing the street embankment to back up the flow until <br />overtopping of the road occurred. Upstream of Kenyon Avenue, a chan- <br />nel traverses the United States Governrnent property up to the embank- <br />ment of Incinerator Lake. tncinerator Lake lies immediately <br />downstream of Sheridan Boulevard. Stormwater crosses Sheridan in an <br />arch culvert. The culvert at Sheridan can carry approximately 200 <br />cubic feet per second, (approximately a two-year frequency flood under <br />fully developed basin conditions). From Sheridan to Quincy Avenue, a <br />mild channel with 5:1 side slopes crosses Pinehurst Country Club golf <br />course. The golf course has three lakes of minimal stormwater deten- <br />tion capacity on this drainageway. <br /> <br />Reach 2: Ownerships along the drainageway include various private <br />entities and the Denver Water Board. The Marston Water Treatment <br />Plant is directly north of Marston Lake. There is no defined channel <br />across the Denver Water Board property upstream of Quincy Avenue, <br />which results in a wide, sheet flow floodplain. At the Marston Lake <br />caretaker's house access road, a channel is resumed which has a mild <br />slope and a cross-section having a bottom width of approximately eight <br />feet, a depth of ten feet, and 1:1 to 2:1 side slopes. This channel <br />continues along the Marston Lake embankment, and adjacent to the <br /> <br />Two irrigation canals cross the Marston Lake North drainage basin <br />upstream of Colorado State Highway 121. Bowles Lateral enters the <br />basin south of Harriman Lake, traversing the basin downstream of <br />Kipling Street in a southeasterly direction and moving out of the <br />basin at Belleview Avenue. Johnson Lateral enters the basin to the <br />north of Lakes Lake, flows along Lakes Lake in a easterly direction, <br />leaving the basin in the vicinity of Henry's Lake. Neither canal was <br />assumed to transfer flood flows in or out of the Marston Lake drainage <br />basin. <br /> <br />The hydrologic characteristics for each reach are summarized below in <br />Table 2. <br />
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