FLOOD09313

• County: Denver
• Community: Denver
• Stream Name: Marston Lake North
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 10/1/1979
• Prepared For: Denver
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 3
I INCREMENTAL RAINFALL DATA*
(All values in inches)
I Time Incremental Rainfall
(Minutes) 2-year 5-year 10-year 50-year 100-year
I 0 0 0 0 0 0
I 10 0.38 0.56 0.75 0.93 1.02
20 0.54 0.79 1.05 1.30 1.42
I 30 0.65 0.96 1.28 1.58 1.73
40 0.71 1.04 1.38 1.71 1.88
I 50 0.76 1.10 1.47 1.82 2.00
60 0.80 1.16 1. 54 1.91 2.10
I 70 0.84 1.21 1.61 2.00 2.19
I 80 0.87 1.26 1.66 2.07 2.27
0.90
90 1.30 1.72 2.14 2.35
I 100 0.93 1.34 1.77 2.20 2.42
110 0.95 1.38 1.81 2.26 2.48
I 120 0.98 1.41 1.86 2.31 2.54
I 130 1.00 1.44 1.90 2.37 2.60
140 1.02 1.47 1.94 2.41
2.66
I 150 1.05 1.50 1.97 2.46 2.71
160 1.07 1.53 2.01 2.51 2.76
I 170 1.08 1.55 2.04 2.55 2.80
I 180 1.10 1.58 2.07 2.59 2.85
*Based on the rainfall on T5S, R69W (Reference 11)
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6

Runoff Hydrographs

The modified SWMM was used to cal cul ate runoff hydrographs for each
sub-catchment and design points. The runoff hydrographs of various
frequencies were estimated using future development conditions with
existing channel conditions. A summary of peak discharges under
future conditions for the 2-, 5-, 10-, 50- and 100-years frequency
events is presented in Table 4.

Runoff hydro9raphs and runoff vol umes under future conditions for the
2-, 10-, and 100-year frequency events at various locations are pre-
sented in Figure 1. The design flow profiles for the 2-, 5-, 10-, and
100-year flood frequencies for the fully-developed basin conditions
and the 100-year peak flow profile for the existing basin conditions
are shown in Figure 2.

TABLE 4
PEAK DISCHARGES - FUTURE CONDITIONS
(All val ues in cubic feet per second)
Location 2-year 5-year 10-year 50-year 100-year
Lakes Lake 170 320 460 660 740
Downstream of Colorado 121 210 420 680 980 1040
Marston Water Treatment Pl ant 230 440 760 1030 1140
Bear Creek Park 270 540 860 1260 1410