FLOOD05252

• Designation Number: 303
• County: Garfield
• Community: Parachute
• Stream Name: Parachute Creek and Colorado River
• Basin: Colorado Mainstem
• Title: Floodplain Information Report - Parachute Creek and Colorado River
• Date: 10/1/1989
• Designation Date: 1/1/1990
• Floodplain - Doc Type: Floodplain Report/Masterplan

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HYDROLOOIC ANALYSIS

Listed in Table 2 are discharges for the return intervals examined in this
study for Parachute Creek and the Colorado River. No further hydrologic
investigations were performed for this report.

TABLE 2

FLCXJD DISCHARGES
(cubic feet per second)

Location

10-year

50-year

100-year

500-year

Colorado River
Parachute Creek

31,200
2,350

40,400
4,400

44,400
5,600

50,100
10,000

Source: ref. 1 and 2

Peak discharges for Parachute Creek developed by the Soil Conservation
Service are derived partially with the use of the SCS TR-20 computer program
which simulates rainfall flood peaks. Output from the program for 16 different
watersheds tributary to the Colorado River between DeBeque and Glenwood Springs
were plotted and a regional curve of drainage area versus peak discharge and
return frequency was developed. Regional curves were also drawn for snowmelt
flood events derived from stream gage data from 8 gages in the area. The
simulated rainfall curves and the snowmelt curves were then combined using a
standard probability equation into one set of curves which was applied to
several tributaries in the area, including Parachute Creek.

Regional stream gage analyses were used by the Corps of Engineers to derive
flood discharges for the indicated return frequencies for the Colorado River as
well. Data from eight gages on the Colorado River, the Roaring Fork River and
Plateau Creek were used without differentiating between rainfall and snowmelt

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