FLOOD00959

• Designation Number: 143
• County: Denver
• Community: Denver
• Stream Name: Marston Lake North
• Title: Flood Hazard Area Delineation - Marston Lake North
• Date: 2/1/1979
• Designation Date: 3/18/1979
• Prepared For: Denver
• Prepared By: UDFCD
• Floodplain - Doc Type: Floodplain Report/Masterplan

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III. HYDROLOGICAL SUMMARY

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March 1975. "Preliminary Drainage Study Marston Lake Area."

(Wastewater Management Division, City and County of Denver.) This

report identified major questions which needed to be resolved be-

fore proceeding with the Marston Lake area drainage plan. One such

decision was whether or not to allow overflow from Lakes Lake to

enter the Marston Sump. The report recommended channels and piping

along the north side of Marston Lake to relieve drainage problems.

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January 1976. "Marston Lake Area Flood Hydrology." (Leonard Rice,

Consulting Engineers.) This report, prepared for the Denver Water

Board, recommended that Lakes Lake be used as a detention facility

for major storms. The study also identified potential problems in

the Marston Sump. Bowles Lateral was considered to flow full in a

storm; thus, no storm drainage can be placed into the lateral.

Flood History

Very little historical information is available for the Marston Lake

drainage basin. Since the construction of Lakes Lake in 1885, it is

not known whether or not any stormwater has overflowed Lakes Lake into

the Marston Sump. It was also acknowledged in Reference 1 that Lakes

Lake had only filled to a dangerous level once, with this instance oc-

curring during the Turkey Creek Flood of 1969. The high water level

was relieved by opening irrigation gates, which allowed water to move

downstream toward Marston Lake.

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January 1978. "Drainage Study for Park West Filing 3." (Hydro-

Triad, Ltd.) This study recommended flows from Park West 2 and

Park West 3 be conveyed in a 40-foot drainageway to Lakes Lake for

detention. An assumption made in this report was that Bowles

Lateral would not be full during a storm due to its low flow rates,

and thus would intercept any runoff upstream of Park West 2 and 3,

and pass it around these developments.

Hydrology

Hydrologic analyses of the study area were carried out to establish

peak discharge/frequency relationships for floods of 2-, 10-, 50-, and

100-year intervals. A modified computerized storm simulation model,

the Storm Water Management Model (SWMM), was used to determine the peak

discharges for the 2-, 10-, 50-, and 100-year storms for the Marston

Lake North drainage basin.

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The SWMM simulates a uniform rainfall over a drainage basin, and routes

the runoff through various combinations of detentions and drainage chan-

nels, and outputs flood hydro graphs for individual sub-catchments.

Drawing No. 3 of 12 shows the Marston Lake North drainage with the sub-

catchments and drainage channels delineated. For this report no loss of

flood water to another drainage basin is considered.

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Rainfall Data

The rainfall intensity was assumed to be uniformly distributed through-

out the drainage basin. The rainfall depths for floods of 2-, 10-, 50-,

and 100-year recurrence intervals were obtained from Rainfall/Runoff

Information published by the Denver Regional Council of Governments and

the Urban Drainage and Flood Control District in May 1972. Table I

lists the rainfall depths for each storm frequency for a three-hour

duration storm.

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