Volume 3, Number 1                                                       March 1998

Greenways and Stream Buffers

   Greenways can be an effective, attractive, and useful means of protecting water quality and enhancing the aesthetic and recreational amenities of a community. Greenways are areas of open space or reduced development density which are generally linear in nature and can be located along stream or river corridors or used to surround and/or connect community features. Greenways provide excellent chances to preserve agricultural land, create recreational opportunities, and protect natural resources in close proximity to even highly developed urban and suburban areas. Similarly, water quality buffers tend to be linear in nature; they are areas of natural or planted vegetation along streams, rivers, lakes, or wetlands through which stormwater flows in a diffuse manner so that runoff does not become channelized and so that infiltration of the runoff and filtering of pollutants is possible. Vegetated buffers play a vital role in protecting water quality by reducing erosion and by trapping nutrients and preventing them from entering waterways and wetland areas. Greenways and riparian buffers can be used in conjunction to protect water quality by creating a vegetated corridor along surface waters.

Water Quality Protection
   Buffers and greenways function as a trap for pollutants and nutrients suspended in stormwater runoff. Leaf litter and groundcover slow stormwater velocity, thereby reducing soil erosion and stream sedimentation. The minimum effective buffer or greenway width to protect water quality depends on factors such as the type of soil, slope, and volume and type of pollutants which would be found in the runoff. Under the Water Supply Watershed Protection (WSWP) Rules, a minimum 30 foot vegetated buffer is required along perennial streams for low density development; and a 100 foot buffer is required for high density development (see graphic, below). Unpaved paths are allowed in the buffer; however, paved pathways would have to be located outside the vegetated buffer area. The vegetated buffer or greenway protects the stream from pollutants transported in urban stormwater runoff. Undisturbed, forested buffers are recommended, and may be more effective for protecting streams from nutrients transported in runoff from agricultural lands.

Greenways and Property Values
   One great selling point for buffers and greenways is that property values tend to increase as a result of open space provision within and around developments where lots have been sized to create that open space. Protected open space in cities and towns of all sizes increases the marketability of adjacent property. This can be an important factor in terms of long-term resale value and appreciation and, of course, the local tax base. Providing buffers and greenways along surface waters therefore achieves multiple goals by protecting the environment, increasing the tax base, and providing recreational opportunities for the community.

Greenway Planning
   If we are to understand the impact of development (whether urban, suburban, rural, or agricultural) on the landscape, we must look at it not as independent pieces -- a woodlot here, a river there, and a pasture yonder -- but as intricately connected parts of a larger whole. Any given part of the landscape affects other parts. When designing a greenway, it is important to consider what impact it will have on natural processes. Greenways, like natural environmental corridors can operate in six basic ways:

1. as habitat for plant and animal communities;
2. as a conduit for plants, animals, water, sediment, and chemicals;
3. as a barrier preventing movement;
4. as a filter allowing some things to pass while inhibiting others;
5. as a source for animals or seeds which move to other parts of the landscape; and
6. as a sink for trapping sediment, toxins, or nutrients.

   Successful completion of a greenway network depends on that network being planned, and it is usually much easier to plan for linear corridors in advance of development. If every square foot of land in a new project is assigned to individual lots or streets (or not planned at all), then wetlands, streams corridors, ridgelines, and other areas suitable for greenways may be rendered inaccessible by lot lines which extend so that each building parcel adjoins similar lots on all sides. Recognizing that it is easier and cheaper to reserve greenway corridors in advance of development rather than to acquire easements which cross property lines after land is subdivided and sold, a number of North Carolina municipalities and counties have incorporated greenway networks into their comprehensive plans and maps.

   While it is easier to create buffers, greenways, and linear parks as an amenity for new developments, it is certainly possible to create these features in areas that are already built out. Open space acquisition, including fee simple purchase as well as purchasing development rights, has been used in Massachusetts and Maryland to preserve farmland and can be used here in North Carolina as well. (Transfer of development rights is not currently enabled in North Carolina however.) While these measures are permanent ways to preserve open space, they are expensive and rarely protect large, contiguous tracts of land. More often, greenways and open space are created through dedication and fee-in-lieu provisions within local government zoning ordinances.

Greenway Guidelines
   There are several ways to make the water quality protection aspect of greenways more effective:

• Make greenways continuous along the river or stream.
• Locate greenways on both sides of the river or stream, if possible.
• Include the river's flood plain, riparian forest, associated wetlands, intermittent tributaries, gullies, and swales in the greenway.
• Either undertake a study of the sitešs sediment and nutrient flow to establish how much is entering the riparian zone and how much it will need to filter, or rely on results from studies done on similar sites.
• Make greenway widths site-specific as opposed to jurisdiction-specific. Greenways which neighbor intensive land uses such as clearcutting, dense residential development, or shopping malls will need to be wide enough to absorb excess nutrients and toxins.
• Maintain a band of natural vegetation along the stream bank to protect against temperature increases.
• Minimize or avoid mowing streamside vegetation because it may decrease filtering effectiveness.

Conclusions
   Nature is a series of interactions among plants, animals, and even air, soil, and water. A healthy environment depends upon keeping those interactions intact. Threats to our environment result from alterations we have made in the landscape that hinder natural processes. The challenge is to ensure that development occurs in a way which will allow the continuity of natural processes.

   Local governments, private landowners, developers, and land trusts play important roles in establishing greenways and protecting stream buffers. The purpose of setting aside buffer zones is to create a zone of transition between two different land uses -- the water and the development -- in order to protect them from one another. A vegetated buffer or greenway may catch and retain sediment carried by overland water flow from construction sites and developed landscapes. The buffer or greenway may also help to protect development on those sites from flooding. Protecting environmental corridors through establishing and managing greenways represents one important method which will safeguard vital ecological processes.

Resources Arendt, Randall. Rural by Design: Maintaining Small Town Character. American Planning Association: Chicago, IL, 1994. N.C. Division of Water Quality -- Water Supply Watershed Protection (WSWP) Local Government Technical Assistance Unit. "Buffers Help Protect Water Quality," Streamlines newsletter. Vol. 1, number 4 (June 1996). Labaree, Jonathan M. How Greenways Work: A Handbook on Ecology. Conservation Fund American Greenways Program, 1992. Scheuler, Thomas R. Blueprint to Protect Coastal Water Quality. The Center for Watershed Protection: Ellicott City, MD, 1995. Scheuler, Thomas R. Site Planning for Urban Stream Protection. The Center for Watershed Protection: Ellicott City, MD, 1995. Terrene Institute and the U.S. Environmental Protection Agency. Local Ordinances: A User's Guide. 1995.