Programs / Riparian Zones

Riparian Zones: What are they and why protect them?


Riparian zones are the transitional areas between land and water, including the margins of streams, rivers, lakes, and wetlands. They are rich in biodiversity and play an important role in protecting water quality and stream ecosystem health. Riparian zones containing of a variety of native woody and herbaceous plant species provide habitat and food for aquatic organisms, as well as terrestrial animals. Root structure in a healthy, dense mix of riparian vegetation fortifies streambanks, which helps control erosion caused by extreme flow velocities and flooding.

Example of healthy riparian buffer on the Harpeth River.
Example of a healthy riparian buffer on the Harpeth River.

Riparian vegetation functions as a large sponge that reduces overland surface flow and absorbs pollutants caught up in stormwater runoff. In addition, tree canopy in riparian zones provides shade, which helps maintain cooler water temperatures and higher dissolved oxygen levels. Although riparian zones begin at the water's edge, there are no formulas or rules that clearly define the outer limit. However, research shows that many of the benefits provided to streams by healthy riparian vegetation are retained with a 35-foot buffer (Wenger 1999). These benefits increase considerably with a 100-foot buffer and even moreso with a 300-foot buffer.

Considering all the benefits that healthy, natural riparian zones provide to streams and other surface waters, these areas should be protected. However, properties  are often developed without knowledge or consideration of the importance of the riparian zone. During the development process, riparian areas are degraded when vegetation is removed, the terrain is graded or plowed, utilities are installed, structures are built, and areas are paved. These changes to the landscape and subsequent human activity in the riparian zone have consequences on steam ecosystem health; nutrients from fertilizers and pet wastes, contaminants from cars and roads, and soils from eroded areas are among some of the pollutants that wash into and degrade streams and other surface waters.

Example of poor riparian buffer in an agricultural area (Wikimedia).
Example of poor riparian buffer in an agricultural area (photo source: Wikimedia).













Harpeth Conservancy has a long history of protecting and restoring this important zone to ensure the streams of the Harpeth River Watershed remain healthy. Some examples of the types of riparian zone projects that Harpeth Conservancy has carried out can be found here. If you are interested in learning more about  riparian buffers and how to protect them, we recommend the Tennessee Department of Agriculture’s Urban Riparian Buffer Handbook. In terms of wildlife habitat in riparian areas, in your backyard, or even front yard, have a look at UT Extension's thorough and insightful Improving Your Backyard Wildlife Habitat guide.