Wildlife and Roads: Decision Guide Step 2.1.2

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2.1.1: Identify Species to Benefit from Potential Mitigation

2.1.2: Identify Ecological Processes (Water Flow, Animal Movement, Other)

2.1.3: Identify Landscape and Topographic Features That May Affect Movement and Mitigation

2.1.4: Identify Engineering and Maintenance Concerns

2.1.5: Weigh Cost Concerns with Potential Benefits

2.1.6: Identify Appropriate General Wildlife Crossing Type

2.1.7: Other Mitigation Options

2.1.8: References

2.1.2 Identify Ecological Processes

Ecological processes need to be accommodated for in transportation corridors, and the installation of wildlife crossings is an opportunity to take into consideration naturally flowing processes, such as the flow of water, the movement of sediment, and possible disturbance regimes such as avalanches, mud flows, and fire. Consultation with natural resource maps, wetlands maps, and hazard maps, can help find the pathways of natural processes that flow through the area. It is also helpful to contact local biological and geological professionals to learn more about these natural flows. The most typical natural process that is accommodated within the road framework is the flow of water. In the case of large wetlands and rivers, and sheet flow across the land, viaducts have been constructed and are in the plans for several road projects, including the future upgrades to Interstate 90 in Washington, and the Route 78 pass over the Mississquoi National Wildlife Refuge wetlands in Vermont, which will be a 152 m (500 feet) long bridge, 3 m (10 feet) off the ground. This accommodation for natural processes can allow the maximum permeability possible in a road corridor, because it figuratively lifts the road and traffic up off of the ecosystem so the 'ecological footprint' of the road and traffic is much reduced. A secondary way to accommodate water is to build bridge over the water system, while also leaving some terrestrial upland available under the roadway. In Montana, US 93 upgrades resulted in dozens of new wildlife crossings, many of them accommodating water while incorporating terrestrial wildlife movement.

This bridge along US 93 near the town of Sula accommodates both the Bitteroot river and terrestrial wildlife movement along paths in between the rocks. Photo credit: P.Cramer.
This bridge along US 93 near the town of Sula accommodates both the Bitteroot river and terrestrial wildlife movement along paths in between the rocks. Photo credit: P.Cramer.


2.1.1: Identify Species to Benefit from Potential Mitigation

2.1.2: Identify Ecological Processes (Water Flow, Animal Movement, Other)

2.1.3: Identify Landscape and Topographic Features That May Affect Movement and Mitigation

2.1.4: Identify Engineering and Maintenance Concerns

2.1.5: Weigh Cost Concerns with Potential Benefits

2.1.6: Identify Appropriate General Wildlife Crossing Type

2.1.7: Other Mitigation Options

2.1.8: References