FLOOD04928

• County: Denver
• County: Jefferson
• Community: Denver, Edgewater, Lakewood, Wheatridge
• Stream Name: Sloans Lake Basin
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 12/1/1977
• Prepared For: Denver / Lakewood
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SECTION III

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HYDROLOGY

Drawing I II in the report section following the Appendix, shows the

location, 1 imits and size of 18 designated sub-basins within the

total Sloans Lake Drainage Basin planning area.

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GENERAL

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Hydrological investigations were performed on Sloans Lake Basin to

determine peak rate of runoff and volume of runoff for the entire

basin and each sub-basin within the study area. The Colorado Urban

Hydrograph Procedure was used to determine peak discharge-frequency

relationships for storm recurrence intervals of 5-, 10-, 25- and

100-years for each of the major drainageways in the basin. This

procedure is well outl ined in the runoff section of the Urban Storm

Drainage Criteria Manual (USDCM) and, therefore, wi 11 not be presented

in any detail in this report.

Table 1 provides the physical data for each of the 18 sub-basins. The

tributary area for each sub-basin varied from approximately 0.128 square

miles (81.9 acres) to 3.743 square miles (2,395.5 acres) with an aver-

age sub-basin tributary area of approximately 0.721 square miles (461.4

acres).

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The completed investigations are based on rainfall data characteristic

of the study area as provided in the USDCM and the Project REUSE report.

The runoff computations made in this hydrologic evaluation included

considerations of both existing and planned future land Use development

within the Basin.

To facilitate the evaluation of intermediate points on the various drain-

ageways within the basin, 17 design points were selected to permit a

detailed hydrologic investigation. Drawing I I I in the report section

following the Appendix, Basin Map, shows the location of 17 design points

and corresponding sub-basins. No design point was designated for Sub-

basin A2a which primarily contributes overland flow into Sloans Lake and

is drained by an existing 15 inch storm sewer located along the bike path

on the east side of the lake.

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Flood hydrographs were computed to define the peak rates of runoff

at the selected design points, as well as the volume of runoff charac-

teristic of the storm frequency and type of development within each

sub-bas i n.

BASIN PARAMETERS

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SUB-BASIN DELINEATION

Each sub-basin was physically described in terms of tributary area to

each design point, sub-basin length, distances from sub-basin centroid

to design point, degree of perviousness throughout the basin and the

selection of representative coefficients typical of the basin. Numer-

ous field visits were made to become famil iar with the physical charac-

teristics of each sub-basin, to aid in making necessary judgments con-

cerning adjustments to coefficients relating peak flows and time to

peak. All available records of existing storm sewers were gathered

from the municipalities in the basin and were studied to determine

the extent, capacity and effects On runoff of the existing storm

drainage facil ities,

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A flood routing through Sloans Lake was also performed to determine

the impact of the Lake on the various design floods.

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Sub-basins were defined in relation to the following parameters:

1. Significant differences in land use and ground cover;

2. Major drainageway crossings;

3. Geographic significance of jurisdictional boundaries;

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