FLOOD00191

• Designation Number: 464
• County: Larimer
• Community: Fort Collins
• Title: Flood Insurance Study - Fort Collins, CO, Larimer County
• Date: 2/1/1984
• Designation Date: 5/1/1998
• Floodplain - Doc Type: Floodplain Report/Masterplan

Peak discharges for the 10-, 50-, and 100-year floods a~ong the
Cache La Poudre River were provided by the U.S. Army Corps of Engineers,
Omaha District (Reference 1). Five hundred-year discharges were
estimated by straight-line extrapolation of the 10-, 50-, and 100-
year floods estimated by the U.S. Army Corps of Engineers.

Peak discharge-drainage area relationships for Cache La Poudre
River, Spring Creek, and Dry Creek are shown in Table 1.

Table 1. Summary of Discharges

Drainage Area
(Square Miles)

Peak Discharges
(Cubic Feet per Second)
10-Year 50-Year 100-Year 500-Year

Flooding Source
and Location

Cache La poudre River
At State Highway 14
At U.S. Highway 287

1
1,1001
1,100

9,586
10,051

15,829
16,526

18,893
19,622

27,000
28,000

Spring Creek
At Confluence With Cache
La poudre River 7.46 1,540 2,700 3,300 4,800
Below Shields Street,
Upstream of North
Tributary 3.92 930 1,550 1,870 2,700
Above Shields Street,
upstream of Central
Tributary 3.03 830 1,320 1,570 2,200
At Upstream Limit of Study l,[;R 470 820 1,000 1,500

Dry Creek
At Confluence With Cache
La Poudre River
At U.S. Highway 287

65.0
60.0

660
720

1,860
1,900

2,700
2,900

5,600
6,000

1 .
Approx~mate Drainage Area

3.2 Hydraulic Analyses

Analyses of the hydraulic characteristics of streams in the community
were carried out to provide estimates of the elevations of floods of
the selected recurrence intervals along each stream studied in the
community~

Flood elevations given in this Fort Collins Flood Insurance Study
for the 10-, 50-, and lOO-year recurrence intervals on the Cache La
poudre River were computed by the U.S. Army Corps of Engineers,
Omaha District. Water-surface elevations for the 500-year flood
were estimated based on rating curves prepared for each cross section
using the U.S. Army Corps of Engineers' information.

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