FLOOD10390

• County: Boulder
• Community: Boulder
• Stream Name: Fourmile Canyon
• Basin: South Platte
• Title: Fourmile Canyon Creek - Major Drainageway Planning - Phase A Report - Alternatives Analysis
• Date: 6/1/2000
• Prepared For: UDFCD, Boulder
• Prepared By: Love & Associates
• Floodplain - Doc Type: Flood Mitigation/Flood Warning/Watershed Restoration

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reaches to convey 1 OO-year flood.

selected channel

Table 7.3
Alternatives Evaluation

Create frequent flood terrace. Grade to establish
a diverse hydrologic regime.

Revegetate with native species. Create wetlands as
feasible. Implement vegetation maintenance & weed
management.

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Alternate 3
Maintain
Existing
Floodplain
Configuration

Alternate 2
IOO-year
Flood

Improvements

Alternate 1
50-year
Flood

Improvements

Environmental Criteria

Establish a buffer between trails and -~
riparian areas to enhance wildlife habitat
and public safety,

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2

1

Long- Term Benefits

Riparian Enhancement
Potential

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o

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2

2

2

1

1

1

Aquatic Enhancement
Potential

Water Quality Enhancement
Potential

Flood Spill/Unknown
Impacts Mitigation

Create a meandering low flow channel, as
feasible, and diverse aquatic habitat -
riffle-type grade control, scour pool creation,
selective maintenance,

Excavation Concept

Figure 7-5
Excavation -Channel

100- Year Flood Channel

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Short- Term Impacts
Notable Habitats* 2 2 2
Riparian Vegetation/Habitat 1 0 2
Aquatic Structure/Habitat 1 0 2
A veralZe 1.3 0.7 2.0

0.0

2.0

1.0

A verav;e

1, 50-year
maintain
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ALTERNATES EVALUATION

The three alternatives chosen for detailed consideration in this report are: Alternate
channel improvements; Alternate 2, lOa-year channel improvements; and Alternate 3,
existing floodplain configuration. These alternates are discussed in further detail in Chapter

7.5

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Legend
Worst
Medium
Best

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1
2

The environmental criteria for evaluating the three master plan alternatives is the degree to which
each alternative fulfills the two stated environmental goals. Specifically, how well the alternative
maximizes the opportunity to enhance the long-term health of the ecosystem, and how well it
minimizes impacts to healthy plant communities, wildlife habitats, and water quality is assessed.
Table E-3 summarizes the relative ranking of each of the alternatives in fulfillment ofthese goals. As
previously stated, the greater the long-term benefits of the alternative, the greater are the short-term
impacts. The specific environmental benefits and detriments of each alternative follows.

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7-9

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