FLOOD01452

• County: Larimer
• Community: Fort Collins
• Stream Name: Fossil Creek Drainageway Basin
• Title: Master Drainageway Planning Study
• Date: 8/1/1982
• Prepared For: Larimer County
• Prepared By: Simons Li & Associates Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Table 1. Percent of One-Hour Rainfall Depth for
Five-Minute Intervals.

Table 3.

Fossil creek Rainfall Intensities (Inches per Hour).

End of Period
(minutes)

Percent of One-HourI
Rainfall Depth

5
10
15
20
25
30
35
40
45
50
55
60

4
4
5
6
9
26
15
11
6
5
5
4

Recurrence Interval in Years
End of Period
(Minutes)
2 5 10 50 100 500
5 0.424 0.552 0.662 0.941 1.075 1.354
10 0.424 0.552 0.662 0.941 1.075 1.354
15 0.530 0.690 0.828 1.176 1.344 1.692
20 0.636 0.828 0.994 1.411 1.613 2.030
25 0.955 1. 242 1.490 2.117 2.419 3.046
30 2.758 3.588 4.306 6.115 6.989 8.798
35 1.591 2.070 2.484 3.528 4.032 5.076
40 1.167 1.518 1.822 2.587 2.957 3.722
45 0.636 0.828 0.994 1.411 1.613 2.030
50 0.530 0.690 0.828 1.176 1.344 1.692
55 0.530 0.690 0.828 1.176 1.344 1.692
60 0.424 0.552 0.662 0.941 1.075 1.354

I Fossil Creek Hydrology Study
(reference 10)

Table 2. Rainfall Depths in Inches for 60-Minute
Duration, Fort Collins Areal

Recurrence Interval in Years

2

5

10

50

100

500

Point Rainfall

1.0~

1.35

1.62

2.31

2.63

3.322

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Fossil Creek
85% Reduction

0.884

1.15

1.38

1.96

2.24

2.82

I Larimer County Stormwater Management Manual,
Figure 3.3.1-1 (reference 15)

2 Fossil Creek Hydrology Study (reference 10)

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