Agricultural Stream Buffers

Why Needed?

Two major pollution concerns from agricultural land, sediment and nutrients, can be effectively controlled by vegetative buffers adjacent to agricultural land.  Iowa State University found that along a 6.8 mile stretch of a local stream, stream bank erosion was reduced by 72 percent by installing a forest buffer.  This same area illustrated that buffers of 66 foot widths reduced overland sediment flow by more than 90 percent (Zaimes et. al, 2004). 

Sediment has been recognized as the number one pollutant to Ohio streams.  Sedimentation is the accumulation of excess soil particles in streams which can suffocate organisms and block sunlight needed by aquatic life.  Nutrients such as phosphorus and nitrogen can attach to soil particles and be transported to streams.  Phosphorus and Nitrogen cause excessive algae growth, deteriorate water quality, and can kill fish. 

In 2002, the Wisconsin Natural Resource board adopted a resolution that will require a mandatory buffer provision to be in place by January, 2008 (Wisconsin Rivers, 2002).  This provision will require stream buffers along all high quality and impaired streams where cost share dollars are available. 

How Large?

The recommended buffer width and type vary depending on the research and site conditions.  For example, the Natural Resource board in Wisconsin determined that a minimum of 30 feet to be an adequate buffer width to protect water quality.  Researchers from the USDA AgroForestry Center and Iowa State University created guidelines for a multi-purpose riparian buffer that included two rows of trees, two rows of shrubs and then 20 feet of grass adjacent to the agricultural land for a total buffer width of 50 feet on each side of the stream (See Figure 74). 

Figure 74: Agricultural Riparian Buffer Model

Source: Dosskey, Schultz, and Isenhart, 1997. Riparian Buffer Design for Cropland. Agroforestry Notes. USDA Forest Service, Rocky Mountain Station.

The placement of trees along stream banks are important in improving water quality.  Trees shade streams and help protect aquatic life from high summer temperatures.  Leaf material from trees also serves as food for aquatic life.  Certain aquatic species are not capable of surviving in streams without a wooded buffer. 

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Last updated: September 19, 2008.