FLOOD05134

• County: Jefferson
• Community: Lakewood
• Stream Name: South Lakewood Gulch
• Basin: South Platte
• Title: Flood Hazard Area Delineation
• Date: 7/1/1977
• Prepared For: Lakewood
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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suggest a larger tributary area than that used in this analysis. However,
recent field inspections have indicated that a large portion of the lower
basin that would otherwise be tributary is in fact cut off by the Sixth
Avenue Freeway. Drainage in this area would tend to run along the frontage
road just south of the freeway, eventually finding its way into lakewood
Gulch. No major problems were noted in this area, except for the potential
inundation of the frontage road during extreme rainfall events. In addition
to this basin modification, others were made according to the local street
grades in some areas. In general, basin boundaries often diverge from those
evident from surface contours in urban areas.

By comparing Tables I I 1-1 and 111-2, it can be seen that future development
flows are not significantly greater than those for present conditions;
typically differing by about 10 percent. The reason for this is the large
extent of urban development presently existing in the basin, as well as
its concentration in the lower half. Most open areas to be developed in the
future are located in the ~pper half of the basin, so that the effects of
increases in subbasin hydrographs due to future development ;n these are",
will be minimized.

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Hydrographs illustrating the 5-year and 100-year flows for the various
subbasins under future development conditions are given in the Hydrologic
Appendix. In addition, storm runoff volumes for future development are pre-
sented in the Hydrological Appendix.

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In addition to peak rates of flow, storm runoff volumes were determined
for present conditions. These volumes are presented in the Hydrological
Appendix.

Future Development Peak Flows

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As discussed in Section I I, the South lakewood Gulch drainage basin is
presently about 70 percent developed. Based upon future land use maps
provided by the City of lakewood officials, peak flows have been de-
termined for the 5, 10, 50, andl00-year flood frequencies, and are pre-
sented in Table 111-2 below.

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TABLE 111-2

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PEAK RUNOFF FLOWS
FUTURE DEVELOPMENT
(All Values in Cubic Feet per Second)

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Subbasin

Peak Flow for Various Frequencies
5-Year 10-Year 50-Year lOO-Year

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1 @ Addenbrooke Pond 120 180 210 240
2 @ Rockmon t Pon d 370 560 670 740
3 @ 1st Ave. Pond 450 670 800 890
4 @ Wadsworth Blvd. 540 800 960 1,070
5 @ lakewood Gulch 630 950 l,130 1,260

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