Riparian Buffer Zones
Riparian buffer zones are vegetated areas along both sides of water bodies that generally consist of trees, shrubs and grasses and are transitional boundaries between land and water environments. Riparian zones act as buffers to protect surface waters from contamination and are habitats for a large variety of animals and birds.
Riparian zones aid in the protection of stream- banks and shorelines against erosion and can provide flood attenuation. They reduce sedimentation in water bodies by reducing the erodibility of streambanks. These areas also aid in improved aesthetic environment; water quality improvement, including soluble contaminant transport and pollutant attenuation; and dispersion of concentrated flow, thereby minimizing gully erosion.
Riparian plants provide aeration and reduce pollutants by plant uptake. Vegetated riparian zones recycles entrapped nutrients in deposited material, provides a habitat corridor for many types of wildlife and offers shade, thereby reducing stream temperature. Riparian zones can provide a great amount of biodiversity to the landscape. Even the detritus (i.e., leaves) that accumulates can provide a valuable food source for plants and animals as well as plays an important role in overwintering habitat for insects and amphibians.
How Does This Practice Work?
Sedimentation and eutrophication can severely interfere with aquatic life. This practice works by reducing excess sediment and phosphorus transport to water bodies through entrapment and vegetation establishment. As water levels rise during rains, riparian vegetation reduces flow velocity, captures sediment, filters out pollutants that would otherwise be transported downstream. Phosphorus that is sorbed to sediment is deposited in riparian zones, remaining on the landscape and enabling plant uptake in the root zone. Riparian buffer zones can improve infiltration and percolation, thus reducing runoff amounts and minimizing the amount of phosphorus transported to nearby surface waters. In some instances, however, riparian buffer areas can contribute soluble P from the vegetation or deposited soils.
Where This Practice Applies and Its Limitations
Riparian buffer zones are established along shorelines or stream banks of waterbodies of any size or scale. The regional and local topography, rainfall pattern, runoff prevalence, climate and soil type all affect riparian zone function. They can be implemented to reduce downstream flooding, to improve water quality, and to enhance wildlife habitat. Deep-rooted native plants, such as trees, grasses, bushes and vines, are a critical component of a functioning riparian zone. These zones run parallel to streams and are dependent upon periodic flooding.
Considerations of other land uses must be made when implementing riparian zones. Such factors include potential for wildlife to damage crops, difficulty in operating farm equipment through the area, and inability to use land for grazing, Variability in local topography and stream condition will affect the frequency and occurrence of inundation in riparian zones, therefore creating variability in nutrient removal and sediment trapping efficiencies, and plant community establishment.
The effectiveness of riparian zones for sediment and sediment-attached P are dependent on water flowing over the soil surface and interacting with vegetation. This can be diminished by disturbances to the natural drainage or habitat. Soil compaction, increased sediment deposits, changes in vegetated cover, and stream channel alteration can affect the balance of the system. Bypassing the buffer with ditches or subsurface drainage reduces the effectiveness of the practice. The removal of vegetation and substrate (e.g. boulders, gravel, and cobbles), stream channelization, damming and dredging can also severely degrade the habitat, thereby affecting the usefulness of riparian buffers.
The ecosystem services provided by riparian zones include soil stabilization and aggregation by plant roots; plant shoots protecting soil by absorbing forces of wind, water and rain- drop impact; cooling and temperature buffer through shading water body; recycling of nutrients and carbon; providing critical habitat; and supporting biodiversity. Because the effectiveness of riparian zones is dependent on several factors, results vary as to how functional they are regarding water quality protection. Challenges to riparian zone function include increased erosion or gully erosion, changing climate factors, invasive species pressures, and land use change.
Cost of Implementing the Practice
The establishment and construction costs depend on available equipment and labor, the level of grading needed, noxious weed and invasive species control, and the vegetation selected for planting. Factors to consider before implementing riparian zones include:
- steepness of slope/irregularity of topography
- soil characteristics, such as clay content, organic material and infiltration rate
- size of runoff-contributing area
- existing vegetation
- availability of native vegetation adaptable to the area
- climatic conditions at planting times
- possible combinations of conservation practices upslope of the riparian zone to reduce erosion, slow runoff velocity, and ensure uniform flow through practice.
Riparian buffer zones are recommended to be at least 50 to 100 feet wide with expansion necessary where there are high sediment loads, steep slopes, or saturated soils (floodplain wetlands). Finding the needed riparian zone width based on desired trapping efficiency rate is a function of pollutant type (particulate or dissolved), field length, slope, soil texture, and field management. Narrow riparian buffer zones are practical where soils are flat and sandy. Clayey soils require a relatively wider buffer. The U.S. Forest Service in the Northeast region recommends a width of 75 ft. on both sides of a stream-based system when plans included using the riparian zone for improved water quality purposes.
The landowner/farmer may be eligible for CRP and WRP assistance as well as both technical and financial assistance from federal, state and local levels, such as the U.S. Fish and Wildlife Service.
Operation and Maintenance
Maintenance of riparian buffer zones is critical to their long-term function. Using native perennial vegetation that is adapted to the setting will create a self-sustaining system, where the plants repopulate and respond to disturbance to regain a natural balance. Management activities will vary based on the vegetation selected. The frequency and required effort of regular maintenance activities are primarily a function of the land’s slope, erosive potential, and weed or invasive species pressure level. Regular maintenance activities include visually inspecting the area after major rain events, removing invasive species and noxious weeds, addressing erosion
The Environmental Protection Agency recommends that total phosphorus (inorganic and organic) remain at concentrations less than 0.1 mg L-1 in surface waterways; this is half of the amount of phosphorus usually found in soils. Nutrient management should be used as the first conservation practices to reduce P moving into water resources. Phosphorus can be managed using the 4Rs: right rate, placement, timing, and source. Using a combination of preventative conservation practices including riparian buffers provide more protection for surface waters than relying on single practice.
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Palone, R.S. and A.H. Todd (eds). 1997. Chesapeake Bay Riparian Handbook: a guide for establishing and maintaining riparian forest buffers. USDA-Forest Service, Northeastern Area State and Private Forestry. NA-TP-02-97. Radnor, PA.
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Wentzel, J., & Hull, C. (2022). An Introduction to Riparian Restoration and Management on Oregon’s North Coast. https://extension.oregonstate…
For Further Information
Contact your local soil and water conservation district, USDA-NRCS or Cooperative Extension Service office. To find your local USDA Service Center, visit https://www.nrcs.usda.gov/contact/find-a-service-center.
University of Tennessee
Editing and Design
NC State University
University of Tennessee
Ludwig, A. 2023. Riparian Buffer Zones. SERA17 Phosphorus Conservation Practices Fact Sheets. https://sera17.wordpress.ncsu.edu/riparian-buffer-zones/