FLOOD04773

• County: Montezuma
• Community: Dolores & Montezuma County
• Stream Name: Dolores River
• Basin: San Juan/Dolores
• Title: Dolores River near Dolores, Colorado Flood Insurance Study
• Date: 5/1/2004
• Prepared For: Dolores
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

7.6 1% Flood Ilydrograohs. TIle calibrated HMS model \....as used with the 1% 48-hour

stonns, loss rates, basellow, unit hydrograph parameters and Muskingum routing parametcrs

discussed above to develop t % llood hydrographs on Ihe upper Dolores River basin. Peak flows

for the 1% West and East Fork centerings, output from the IIMS model. are listed on Table 14 for

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severa11ocations. 'Jl1e dilTerence in 1% flood peak flows al Dolores between the East and West

fork ccnterings is not significant; however. the East Fork cenlcring produced a peak 110w at thc

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below Rico gage that is much highcr than indicated from the now frequcncy analysis for the Rico

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gagc. This is discusscd further in Scction 8, Flow Frequency Analysis. For thc t% llood

hydrograph for the Dolores River below Lost Canyon Crcek for the West Fork Centering see

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Plate 26.

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Table 14
Peak Flow (cfs). 1% Eneedence 2-day General Storm
West Fork \'s. East Fork Centering.
Index D.A. West Fork Centerings East Fork Centerings
Point (mi2) Peaks (cfs) Peaks (cfs)
"upper mainslem" Dolores R below Rico 105 2.290 5,260
llearCreek 34 1,130 1,010
East Dolores above West Fork 278 7.516 S.233
West Dolores at mouth 16' 3.820 3,580
East Dolores plus West Fork 446 11,300 11,600
Dolores at Dolores 504 11.700 12.000
Lost Canyon Creek near Dolores 71 820 910
Dolores R below Lost Canyon Creek 579 12,300 12,600

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8. Flm'" Frequency Analysis

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8.1 Upoer Dolorcs Basin Strcamllow Records. The 1976 1100d hazard infom13tion

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hydrology report included a peak flow frcquency analysis for the Wcst Dolores Rivcr at mouth,

upper ffiainstcm Dolores River above West Dolores Rivcr. Lost Canyon Crcek at its mouth. and

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Dolores River below Ihe conl1uence with Lost Canyon Creek. An additional 29 years of

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streaml10w records arc now availablc for analysis at the Rico and Dolores gagcs. The Lost

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28

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