FLOOD08945

• County: Larimer
• Community: Fort Collins
• Stream Name: Dry Creek
• Basin: South Platte
• Title: Hydrologic Analysis Major Drainageway Planning Dry Creek
• Date: 7/1/1979
• Prepared For: Larimer County
• Prepared By: Gingery Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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peak is difficult to predict. That is, the flood peak may be increased
as canal flows drain into Dry Creek, or the flood peak may be reduced
should flood levels be high enough to continue to direct flows into
the canals. In either case, for the critical 100-year event, the
effect would be small, say !20 percent, and should be ignored.
The frequency discharges determined by these methods at selected
points within the study reach are shown in Table V. The hydrographs
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for Dry Creek at its confluence with the poudre River and at its . "r' i
juncture with the Eaton Ditch are shown in Figures 3 through 14. ~. V I
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, .
-V

TABLE V

Frequency

Discharges and Volumes

Frequency Discharge (cfs)
10-Year 50-Year 100-Year
Q(cfs) Vol Q(cfs) Vol Q(cfs) Vol

Location

2-Year 5-Year
Q(cfs) Vol Q(cfs) Vol

SOO-Year
Q(cfs) Vol

Confluence 230
wi th Poudre
D/S of Eaton 0
Ditch
U/S of Eaton 55
Ditch
U.S. High- 55
way 287

50 440 90 620 250

1900 740 2700 2110 6000 2720

o 0 0 250 20

1950 720 2820 1890 6000 2450

25 260 100 630 230

1950 720 2820 1890 6000 2450

25 260 100 630 230

1950 720 2820 1890 6000 2450

The frequency discharges at these same locations for the 100-year
event without Douglas Reservoir are shown in Table VI. The percentage
increase in flow for this basin condition is also shown. The hydro-
graph is provided in Figures 15 and 16.

TABLE VI

Frequency Discharges
(Without Douglas Reservoir)

Location

100-Year Discharge (cfs)

% Increase

Confluence with
Poudre

D/S of Eaton Ditch

U/S of Eaton Ditch

U.S. Highway 287

4200

4200
4200
4200

50
50
50
50

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