FLOOD03485

• County: Denver
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: Comparison of Estimated Flood Peaks with Historic Floods
• Date: 1/1/1986
• Prepared For: State of Colorado
• Prepared By: USDOI
• Floodplain - Doc Type: Educational/Technical/Reference Information

of 9,670 ft3/S from a drainage basin of 1,38 ml', and Dark Gulch at Glen Haven (tlowing south
,<1 the divide) had a reported discharge of 7,210 ft3/s from a drainage area of 100 mil. Both
of these small basins produced discharges In excess of 7,000 ft3/s/mi2 from this thunder-
storm [45],

The topography of the area is characterized by steep north and south facing slopes with rugged
rock faces along the ridge lines and a thin soil mantle, which supports moderate stands of coni-
ferous trees and small brush at the lower elevations, Because of the steep slopes and small storage
capacity of the soils, storm runoff quickly reaches nearby surface channels. On this basis, C values
of 0.7 were selected to aid in the determination of PMF hydrographs With this assumption and
basin parameters measured on USGS 40-ft contour maps, lag times of 22 and 17 min were
computed for these two small basins, This is generally consistent with the reported times of 6:30
p.m" when the rainfall started, and about 7:00 p.m" when the first damage was reported by
residents on the larger streams. Loss rates assumed in preparation of PMF estimates for both
streams were assumed to be 0.15 in (initial) and 0,10 in/h (constant).

The PMP for these two small basins was derived from HMR 55 [2J maps and procedures. Table
21 presents the PMP estimates for various durations used in this study.

2B
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15 r

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6 12 ~8 2-4,
'l.1E H~Ot~ t<E(;Ir~t~H,'r; 01' RHI,\JFi-1Ll :hr-::;)

30

36

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!Sl
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BUREAU CF RECLPMATION
PMF COMPRR1S0~. SlLDY
OJ, rGRK T,,;3. :<E9R GLEN HAVEN CC.
LPG "'. 0.37 HR BUCK:-iORN TiuH
PM? F~SED O~ rlMR j5

" r'!1r PEAK.. 161Qe CFS
II
II

II
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II

HISTORIC FLOOD PEAK~ 9670 CFS
60% OF PMF PEAK

PMf" 3D HOU~ VCl.L!HE ... 1613 AC!oi'E FE:ET

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HISTOfUC fl00D JUl' J! 1976 PERI< .. ~6;'~ cr-s
K\.n 7~'lJ/a",

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pla:~ ~o - COr'10urerl PMF hydrograph and historiC flood peak for North Fork Tributary near Glen Haven, CO

58