FLOOD05229

• Designation Number: 86
• County: Arapahoe
• Community: Littleton
• Stream Name: Lee Gulch and Little Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Lee Gulch and Little Creek, Littleton, Arapahoe County, CO
• Date: 10/1/1977
• Designation Date: 11/1/1977
• Floodplain - Doc Type: Floodplain Report/Masterplan

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railroad crossings along Little Creek. A storm drain between
Dry Creek Road and the Highline Canal discharges directly in-
to the canal and the channel at Sterne Park discharges direct-
ly into the City Ditch. The drainage structures along Little
Creek are generally inadequate to pass even the high fre-
quency storm flows with the exception of the AT&SF Railroad
crossing.
D. FLOOD HISTORY
Little information is available about past flooding on Lee
Gulch or Little Creek, particularly floods from low frequency
storms. The trans-basin diversion of storm flows by the
Highline Canal and the City Ditch, especially in the Little
Creek Basin, has probably dampened the flooding effects of
both streams, though this has undoubtedly contributed to
flooding downstream of both canals. Nuisance flooding has
occurred from minor storms in downtown Littleton and on Lee
Gulch near Gallup Street.

TABLE I
HYDROGRAPH PARAMETERS
Length to
Sub- Area Length Centroid Slope % Ct Cp
Basin (Sq.Mi. ) (~1i. ) (Mi. ) (%) Imp.
LEE GULCH
1000 0.40 1.52 0.76 1.2 31 0.54 0.66
2000 0.63 1. 33 0.66 2.6 36 0.45 0.62
3010 0.72 1. 61 0.83 2.6 47 0.37 0.56
3020 0.27 1.21 0.59 3.1 67 0.27 0.49
3030 0.40 0.99 0.33 0.1 74 0.53 0.66
4000 0.20 0.59 0.21 3.9 41 0.39 0.58
LITTLE CREEK
100 0.12 0.64 0.26 1.0 95 0.23 0.46
200 0.62 1.48 0.78 1.2 39 0.45 0.62
300 0.83 1. 33 0.52 1.6 45 0.40 0.59
410 0.57 1.28 0.52 1.9 42 0.43 0.61
420 0.30 0.97 0.47 2.1 52 0.36 0.56
500 0.29 0.80 0.28 2.7 41 0.41 0.59
NOTE: Parameters are based upon future land use.

III. HYDROLOGY

Rainfall data was obtained from the Rainfall-Depth-Duration-
Frequency Maps in the "Urban Storm Drainage Criteria Manual". De-
viations between the upper and lower portions of basins were be-
tween 0 and 0.2 inches and did not warrant using separate rainfall
intensities over the basin. Consequently, the upper basin, or
slightly higher values, were used. A three hour duration storm
was used. The rainfall data is summarized below:
Rainfall Duration
6 Hour

Return Frequency

2 Year
10 Year
100 Year

1 Hour

24 HOLlr

A hydrological analysis of both basins was completed to de-
termine the peak discharge-frequency relationship for floods of
the 2, 5, 10, and 100-year recurrence intervals. These peak dis-
charges were predicated upon full development of the basins with
future land use determined from the City of Littleton and Arapahoe
County master plans.
The Cblorado Urban Hydrograph Procedure as described in the
"Urban Storm Drainage Criteria Manual" (revised 5/15/75) and in-
terim guidelines furnished by the UDFCD were used to obtain storm
hydrographs for each sub-basin. Basin and sub-basin boundaries
are shown on Sheet 1 of the drawings and hydrograph parameters
are shown in Table I.

1.0
2.1
2.7

1.6
3.3
4.3

2.1
3.7
4.7

The storm hydrographs of the sub-basins were routed and com-
bined using the Convex Method of Stream Routing of the Soil Con-
servation Service and the Modified PuIs Method of Reservoir Rout-
ing to obtain peak discharges at the various hydrological points.
Typical flood hydrographs are shown on Figures I.A. and I.B., and
peak flow profiles on Figures II.A. and II.B. It was assumed
that all trans-basin conveyance of storm runoff by agricultural

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