FLOOD05064

• Designation Number: 205
• County: Larimer
• Community: Fort Collins
• Basin: South Platte
• Title: Master Drainageway Planning - Cooper Slough, Boxelder Creek, Fort Collins, Larimer County, Colorado
• Date: 8/1/1981
• Designation Date: 1/1/1983
• Floodplain - Doc Type: Floodplain Report/Masterplan

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VI. ALTERNATE IMPROVEMENT PLANS

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Table 21. Average Annual Flood Damages

General Considerations

This chapter discusses the alternative improvement plans and the concep-

tual designs to implement these plans. First, the general considerations used

in formulating and designing the alternatives are presented.

Conceptual drainageway improvement plans were formulated to alleviate

flood damages in the Boxelder Creek-Cooper Slough Basins. In the formulation

of improvement alternatives the following factors have been considered:

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Location Annual Flood Damages

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Boxelder Creek

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Reach 1

$ 23,200

1.

Long term relief of flood problems.

Reach 2

$ 7,670

2.

Adequacy of existing detention and conveyance.

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Reach 3

$ 5,710

3.

Increases in stormwater flows across downstream properties due to
development upstream.

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Cooper Slough

4.

Available right-of-way.

Reach 1

$150,000

5.

Ease of maintenance and access.

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Reach 2

$712,700

6.

Water quality improvements.

7. Erosion control.

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The design criter~a utilized for formulating these master drainageway

improvement plans are those contained in the "Larimer County Storm Water

Management Manual" (reference 11). Specific considerations for the Boxelder

Creek-Cooper Slough drainageway improvements are summarized below.

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1. Open Channels: Two types of channels are commonly used - natural and

constructed. Constructed channels may be lined or unlined. Unlined open

channels with grass cover are preferred due to lower velocities and the

natural appearance. In addition, the shape of unlined channels can be chosen

to create additional sociological benefits by establishing greenbelts or

recreational opportunities.

Lined open channels are sometimes required due to limited right of way

and topographical or hydraulic considerations.

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2. Hydraulic Structures: Flow characteristics may be controlled with the

proper use of hydraulic structures. Hydraulic structures such as energy

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