FLOOD03506

• County: Jefferson
• Community: Lakewood
• Stream Name: South Lakewood Gulch
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 8/1/1978
• Prepared For: Lakewood
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 111-2

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

Peak Flol. for Various Frequencies
Subbasin 5-Year 10-Year 50-Year 100-Year
@ Addenbrooke Pond 120 180 210 240
2 @ Rockmont Pond 370 560 670 740
3 @ First Ave. Pond 450 670 800 890
4 @ Wadsworth Blvd. 540 800 960 1,070
5 @ Lakewood Gulch 630 950 1,130 1,260

Storm runoff volumes were determined at each design point for each frequency.

This was done for both present conditions and future development, and these

were found to agree within 5 percent. Only the runoff volumes for future

development are presented in Table 111-4. Volump~ sh""ln are cumulative

values at the lower end of each subbasin.

By comparing Tables 111-1 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 upper half of the basin, so that the effects of
increases in subbasin hydrographs due to future development in these areas
will be minimized.

The effect of the Master Plan flood storage improvements will serve to elongate

the runoff period, not to decrease the runoff volume. After improvements, the

runoff volume of 26 acre-feet resulting from Subbasin 1 is expected to dis-

charge at a constant five cfs. At this rate, it will take approximately

two and one half days after a 100 - year storm to completely drain the pond

as opposed to the immediate runoff effect of a storm. At Rockmont, the normal

operating water surface will be restored within approximately 3~

hours. The pond at First Avenue will be at normal operating levels within

one half hour after the storm.

Revised peak runoff flow rates have been developed utilizing the proposed

maximum detention storage at Garrison Street and the proposed maximum

available storage at Rockmont College and at First Avenue and Balsam sites.

These peak flows comparing the effect of stormwater storage are given in Table

111-3.

TABLE 111-3

PEAK RUNOFF FLOWS
FUTURE DEVELOPMENT WITH DETENTION
MASTER PLAN IMPROVEMENTS
(All Values in Cubic Feet per Second)

Subbasin

TABLE 111-4
RUNOFF VOLUMES
FUTURE DEVELOPMENT
(All valuE'S in acre-feet)
~u~,o!f_V~I~m!:, !o.!:. ~a.!:i~u~ !:.r!:,q~e~ci.e~
5-year 10-year 50-year 100-year

5-Year 100-Year
Subbasin (I nflow/Outflow) (Inflow/Outflow)
1. @ Addenbrooke Pond * 120/5 310/5
2. @ Rockmont POnd 300/5 510/130
3. @ First Ave. Pond 120/100 380/320
4; @ Wadsworth Blvd. 220 480
5. @ Lakewood Gulch 360 770

I
2
3
4
5

10
30
41
51
63

18
55
74
92
114

23
70
95
118
147

26
78
105
131
163

*

Detention storage facility to be located at Garrison Street.

111-3