FLOOD01682

• County: Fremont
• Community: Florence
• Title: Hydrologic Analysis for Coal Creek and Oak Creek in the Vicinity of Florence
• Date: 9/1/2000
• Prepared For: CWCB
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 1
COMPUTED PEAK DISCHARGES FROM PREVIOUS STUDIES
FOR COAL CREEK IN FLORENCE, COLORADO
Location and Report Drainage Area 1O.0%-Chance 2.0%.Chance 1.0%.Chance O.2%-Chance
Date (Sq.mL) Flood Flood Flood Flood
(cfs) (cfs) (cfs) (cfs)
Coal Creek (1977) 18.1 3,713 7,917 10,508 20,160
Coal Creek (1978) 18.1 4,850 7,850 9,000 15,000
Coal Creek (1984) 18.4 3,400 6,200 7,400 8,200
Coal Creek (1989) 20.4 4,900 7,800 9,000 15,000

TABLE 2
COMPUTED PEAK DISCHARGES FROM PREVIOUS STUDIES
FOR OAK CREEK IN FLORENCE, COLORADO
Location and Report Drainage Area 10.0%.Chance 2.0%-Chance 1.0%-Chance O.2%.Chance
Date (Sq.mi.) Flood Flood Flood Flood
(cfs) (cfs) (cfs) (cfs)
Oak Creek (1977) 71.9 7,599 15,308 19,841 36,583
Oak Creek (1978) 72 10,500 17,000 20,500 36,500
Oak Creek (1984) 71.6 11,000 19,500 22,500 30,000
Oak Creek (1989) 71.6 10,500 17,000 20,500 37,000
Oak Creek (1991) 72 7,100 13,300 16,000 23,000

FLOOD HISTORY

The majority of flood problems in the study area are caused by cloudburst-type storms over
the foothills to the south of Florence during the summer months of June, July, and August. These
high intensity, short duration rainstorms oflimited areal extent result in flash floods of high peak
flow, short duration, and low total runoff volume.
Flood potential also exists from long duration rainstorms and from rapid melting of snow
cover in the upper drainage basins during late spring. These floods are characterized by moderate
peaks, large volumes, and long duration. The potential for the most severe flooding is created by the
combination of rapid snowmelt with long duration rainfall.

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