Highway design traditionally has been regimented to focus on “hard” engineering approaches to efficiently convey traffic and deal with incidental concerns like the movement of stormwater. Evolving national environmental regulations and regional concerns over flooding and groundwater have begun to push designers of roadways and other “gray infrastructure” systems to consider alternative approaches. This has led to a consideration of more holistic “green infrastructure” designs that not only provide environmental benefits, but may save money in the process.
Green infrastructure has been championed by Chicago Wilderness, a regional consortium of more than 250 public and private organizations that work together to restore local nature and improve the quality of life. Green infrastructure also has been embraced by the Chicago Metropolitan Agency for Planning as a core theme of the recently adopted GO TO 2040 Plan.
So, what does green infrastructure mean in the context of roadway planning and design?
Green infrastructure is used to describe products, technologies, and practices that use natural systems—or engineered systems that mimic natural processes—to enhance overall environmental quality and provide more sustainable utility services. More specifically, it includes techniques such as porous pavement, rain gardens, and vegetated swales that use soils and vegetation to infiltrate and/or recycle stormwater runoff. On a larger scale, green infrastructure refers to strategically planned and managed networks of natural lands, working landscapes, and other open spaces that conserve ecosystem values and functions and provide associated benefits to human populations.
Following are several brief examples of recommended green infrastructure approaches in the context of proposed roadway projects.
The northeastern Illinois landscape contains an abundance of sensitive natural communities, including lakes, stream corridors, wetlands, prairies, and woodlands. Some of these systems have been identified as regionally significant “resource protection areas” in the Chicago Wilderness Green Infrastructure Vision. Highway projects have the potential to damage such systems directly, as well as fragment wildlife habitats and adversely affect critical water flows. The siting of the road rights of way should attempt to minimize direct ecosystem impacts and fragmentation. It also is recommended that highway planners work with local and regional conservation agencies to design plans for habitat damage mitigation, enhancement of ecosystem connectivity, and wildlife movement that take into account regional biodiversity considerations and opportunities. This task should include the development of refined inventories and maps of existing and potential green infrastructure in the project vicinity.
Roadway construction can dramatically increase stormwater runoff, resulting in increased flooding, water pollution, and reduced groundwater recharge. In response to such concerns, most counties in northeastern Illinois have developed comprehensive ordinance requirements that address both runoff quantity and quality. These provisions should be used as a starting point for roadway and stormwater design. However, it is suggested that local watershed plans also be utilized so that specific pollutants of local concern and local hydrologic considerations are used as the basis for optimizing the design of best management practices (BMPs). Further, it is recommended that state-of-the-art national guidelines and research be utilized in selecting and designing the most effective BMPs to address the locally identified water quality and hydrologic concerns. Finally, it is recommended that a green infrastructure theme be used for the design of roadway and water management systems. Simply put, such designs would minimize impervious surfaces and treat water at the source using soils and cleansing vegetation. This approach would value water as a resource, not a waste product to be disposed.
Traditional roadway designs contain rights-of-way that feature turf grass and ornamental shrubs and trees that often bear no resemblance to local native landscapes. Such landscapes can be expensive to maintain and offer little in the way of ecosystem services or visual appeal. As a consequence, suburban roadways in Illinois look much like roadways in Atlanta, New York, or almost anywhere in the country. A recommended alternative is natural landscaping that utilizes appropriate native grasses, forbs, trees, and shrubs to create an ecologically functional and aesthetically appealing corridor that reflects a local sense of place. The extensive use of deep-rooted native vegetation also can help to mitigate the impacts of climate change by acting as a carbon sink. Natural landscaping was recently incorporated into a “green roadway” system for a four thousand-acre intermodal project in Joliet. Other midwestern states such as Iowa have provided leadership in the natural landscaping movement through a Department of Transportation Living Roadway Trust Fund. One important proviso is that mechanisms must be adopted for the ecologically sustainable, long-term maintenance of natural landscapes so that installed landscapes thrive and corridors do not become routes for the spread of invasive species.
Green Infrastructure in Surrounding Communities
While much of the focus of new regional roadways is on mitigating the direct effects of the road corridor, far greater impacts may potentially be caused by the spin-off development spurred by the roadway. That is why it is critical that neighboring communities also consider green infrastructure principles in their plans and ordinances. At a minimum, these communities should consider green approaches to stormwater management, landscaping, and infrastructure designs as mentioned above. They should promote green infrastructure in neighborhoods, school grounds, and back yards. They should consider integrated approaches to open space and natural area protection, greenway connections, and trail and bikeway planning. These initiatives should be done not just to counteract potential adverse effects of the roadway, but to build communities that are more walkable, livable, and ultimately more healthy. Chicago Wilderness, through its Sustainable Watershed Action Team (SWAT) has supported the development of green infrastructure plans in several counties and communities that could serve as models for other communities in the region. These include the Mettawa/Lincolnshire/Riverwoods planning area, McHenry County, and the cities of Crystal Lake and Woodstock.
In conclusion, the design of a potential new roadway provides an exciting opportunity to embrace green infrastructure as a core theme. Green infrastructure reflects a fundamental paradigm shift that minimizes environmental impacts, enhances community livability and sense of place, and also has the potential to reduce construction and maintenance costs. While there are numerous green infrastructure references, a good starting point on northeastern Illinois principles and practices is the Ecological Planning and Design Directory.
Published on 11 July 2012
Image credit: Cermak Road Sustainable Streetscape – Chicago by Center for Neighborhood Technologies courtesy of Flickr.