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4 Ameliorating the Effects of Roads
Pages 98-116

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From page 98...
... Protecting natural resources and providing safe and effective transportation are in the public interest, and addressing both of them is good public policy and practice. Ameliorating environmental effects can occur at all phases of road projects -- from planning and design through construction and maintenance operations.
From page 99...
... It begins with a discussion of mitigating effects organized by scales of administrative organization; the largest scale pertains to national or regional perspectives, the medium scale includes state or highway corridor planning, and the smallest or finest scale applies to the decisions and opportunities associated with individual transportation projects. The chapter ends with a section on opportunities for increased environmental stewardship during routine maintenance operations after construction.
From page 100...
... State and Highway Corridor Considerations (Medium Scale) Opportunities to ameliorate the ecological effects of transportation activities at the medium scale equate best to the planning stages of individual projects, larger road corridors, and statewide transportation system plans.
From page 101...
... For example, the appropriate planning area for concerns about the continued survival of a species that is dependent on a particular ecosystem process (improved water quality) may need to consider two ecologically defined boundaries: watershed and species range.
From page 102...
... . Natural water bodies are a critical component of the life-history requirements of many species, which may be required to move between the water body and other habitat areas on a daily basis or during an annual migration.
From page 103...
... In most cases, it will not be possible to either remove roads or reduce overall traffic volume in the region. However, planners can strive to reduce the ecological impacts of roads by implementing measures that redirect most traffic away from ecologically sensitive natural areas in the region (Figure 4-3)
From page 104...
... For example, if the existing road is near a water body, more ecological damage might be caused by increasing traffic on it than by building a new road if it is in a less ecologically sensitive location. There also can be social and political reasons for not increasing traffic volume on existing roads.
From page 105...
... The result of these tactics is less construction of new roads and therefore reduced habitat fragmentation, suggesting that a less dense road network with higher volumes results in less habitat fragmentation. Sometimes, political and economic conditions might not allow implementation of measures to reduce traffic on roads near natural areas.
From page 106...
... environment, regional or landscape habitat connectivity models can facilitate decision making in identifying, setting priorities Worse Better FIGURE 4-6 Illustration of mitigation measures to reduce the ecological effects of roads when it is not possible to redirect traffic away from natural areas. Measures include lengthened bridges to permit flows of water and animals under the road and wildlife overpasses to permit animal movements over the road.
From page 107...
... Some examples include state biodiversity plans, endangeredspecies recovery plans, and watershed-restoration plans. Many of these plans are not conducted in coordination with transportation planning information and as a consequence do not take the existing transportation network or potential expansion into account.
From page 108...
... have collaborated on a partnership to minimize the environmental impacts from road projects. Developed in 2002, Caltrans and TNC combined California Transportation In vestment System data highlighting existing paved roads, current pro jects, and planned development for the next 20 years and TNC port folio sites displaying conservation and biodiversity data at multiple scales.
From page 109...
... Wildlife passages are found in 23 states, 17 of which are beginning to systematically incorporate wildlife crossings into roadway designs (Evink 2002) and across Europe (Damarad 2003)
From page 110...
... Design standards for stream crossings that routinely incorporate in-water piers can help to improve environmental conditions. The periodic reconstruction of highway bridges that span riparian areas is an excellent opportunity to improve wildlife passage along riparian corridors by widening bridge spans or by habitat enhancement.
From page 111...
... Consequently, there are few published studies to refer to for design criteria for habitat connectivity structures for wildlife (for example, wildlife passages) or guidelines for multiple species or fragmentation-sensitive species (for example, wide-ranging large carnivores)
From page 112...
... A Transportation Research Board report cited the highway mitigation research in Banff National Park as having worldwide importance and as being one of the most successful research projects for wildlife connectivity (Evink 2002)
From page 113...
... Wildlife crossings are expensive measures, but the gap in devising cost effective designs and decision-support tools based on ecological and engineering criteria leaves no alternative. Roads do not affect wildlife populations equally (Forman et al.
From page 114...
... . The state of Iowa's roadside management program is an example where transportation agencies are partnering with other groups to achieve goals of restoring large areas of prairie ecosystem (White and Ernst 2003)
From page 115...
... conditions, to provide erosion control, slope and stream bank stabilization, wildlife habitat, and other benefits. These projects usually require less heavy machinery and can be installed when the site problem is small and during slow construction periods, thereby costing less and causing fewer impacts.
From page 116...
... Other small-scale projects focused on endangered species recovery and restoration, such as riparian and stream restoration for salmon in the Pacific Northwest and fencing for protection of the desert gopher tortoise. Other projects included attempts at decreasing habitat fragmentation by construction of multifunctional crossings, widening of bridges, and improving wildlife connectivity.


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