Grassed Waterways (NRCS #412)

Applicable Systems

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About

Grassed waterways¹ are channels with vegetation used to convey water flows to prevent soil erosion, gully formation and flooding. They are also used to protect water bodies and water quality.

Key aspects and considerations:

Consider federal, state, and local laws and regulations, species selection, topography, and common associated practices².
Establish grassed waterways where runoff from arable land concentrates.
Select species able to achieve adequate density, height, and vigor within an appropriate time frame.
Preserve waterway capacity, vegetative cover, and outlet stability through maintenance.
Fill and reseed eroded areas quickly after heavy rainfalls to prevent further erosion.
Allow livestock and vehicle crossings perpendicular to the waterway.
Do not use grassed waterways as field roads.
Evaluate costs based on site-specific characteristics such as slope, soil type, and drainage.

Benefits and Limitations

ACRE Category	Benefits	Limitations
Soil Health	Reduces soil erosion especially in concentrated flow areas. Prevents gully formation by safely conveying runoff. Perennial roots provide greater soil aggregate stability. Perennial vegetation support microorganisms and other biological activities that enrich soil and increase soil organic matter.	If soil is compacted or grass is too short, the effectiveness is reduced.
Water Management	Conveys runoff while reducing flow velocity. Increases water interception and soil water holding capacity thus reducing surface runoff. Enhances water infiltration thus reducing ponding, flooding, and sediment transported to surface water. Reduces nitrate pollution in tile drainage from agricultural land. Reduces surface and ground water contamination and improves water quality.	Requires stable outlet protection to prevent downstream erosion. Can be overwhelmed during heavy precipitation.
Nutrient Management	Reduces nutrient losses by reducing runoff, and by filtering and absorbing chemicals and nutrients. Improves nutrient cycling. Promotes nutrient uptake by perennial grasses.	Dissolved nutrients may still be transported downstream.
Agricultural Production	Prevents loss of productive land from expanding gullies. Improves plant productivity and health. Contributes to pest suppression.	If poorly managed, can harbor invasive weeds.
Biodiversity and Wildlife	Permanent vegetation promotes stable habitat for soil organisms, shelter and corridors for wildlife, and connects patches of fragmented habitats. Improves overall habitat quality for pollinators and wildlife. Provides seasonal habitat for aquatic species, especially if connected to a stream or river.	If mowed frequently, provides less wildlife habitat.
GHG Emission	Perennial grasses and deep-rooted plants have potential to offset CO₂ emissions and store C in both biomass and root systems. Can reduce fuel associated with repairing erosion damage.	In wet and saturated soils, denitrification of N-rich fertilizer received from the fields can increase N₂O emissions.
Economics	Protects long-term land productivity. Reduces maintenance costs associated with gully repair and sediment removal. Extra revenue can be obtained from grasses planted to feed the livestock. Farms can benefit from state, federal, and private financial assistance programs, such as the Conservation Reserve Program (CP8A), to mitigate the costs.	High initial cost for installation and the land taken out of production. Grassed waterway is among the most expensive practice of erosion control³. Requires sediment buildup and regular mowing thus increasing labor and associated costs.

Impact on Agricultural Resilience

Grassed waterways buffer extreme rainfall and flooding by slowing down runoff and increasing infiltration, making water available for plants in dry periods.
Act as natural filters by intercepting contaminants (sediment, nutrients, pesticides, pathogens) before reaching streams, thus protecting soil and water quality.

Regional Applicability

In Midwest corn-soybean systems, grassed waterways help to prevent erosion during bare soil periods.
Discovery Farms has an ongoing edge-of-field monitoring site study in Kewaunee County, Wisconsin, which started in 2019 and illustrates the impact and importance of stable grassed waterways.
In Iowa, mixes of brome-alfalfa are recommended for grassed waterways because they require low maintenance and have the ability to auto-repair when damaged by heavy storms. However, mow and weed control are required.
According to Iowa Agriculture Water Alliance, "the cost of constructing a grassed waterway depends on the area draining to the waterway, the slope of your land, and the length of the waterway. If only seeding is needed, installation is estimated at around $30-$40 per acre. If you're looking to construct a waterway from scratch, it could cost around $2,000 per acre. Maintenance costs involve mowing and average $20 per acre annually."

Case Studies

Get to know how Ray Gaesser, a farmer in Adams County, Iowa, combines no-tillage and grassed waterways to improve his cropland with healthy soil management. "Water infiltration tests show Ray's fields can absorb an inch of water in two to three seconds. Comparable fields with a history of tillage take seven to eight minutes to absorb that much water."
Dan and Ruth Boerst, dairy farmers in Manawa, Wisconsin, installed grassed waterways through the Environmental Quality Incentives Program to improve water quality by trapping sediment and preventing sediment and nutrients from reaching the Little Wolf River. "We've always been involved in implementing conservation," said Dan.
Conservation efforts, including grassed waterways, are being continually implemented by Jim and Melody Bourn in Southwest Iowa to ensure their land remains productive and sustainable for future generations.

Resources

Video. USDA-NRCS: Grassed Waterway
Video. Blanchard River Demonstration Farms Network: Grassed Waterways Conservation | Ohio Demo Farms
Video. Iowa Farm Bureau: Grassed Waterways Protect Iowa Soil and Water
Clean Water Iowa: Grassed Waterway
Penn State Extension: Roadside Guide to Clean Water: Grassed Waterways
USDA Natural Resources Conservation Service, Iowa Conservation Practice 412: Grassed Waterway Iowa Fact Sheet

References

USDA-NRCS (2020). Conservation Practice Standard Document, Grassed Waterway, Code 412. https://www.nrcs.usda.gov/sites/default/files/2022-09/Grassed_Waterway_412_CPS_9_2020.pdf
USDA-NRCS (2020). Conservation Practice Standard Overview, Grassed Waterway (Code 412). https://www.nrcs.usda.gov/sites/default/files/2022-09/Grassed_Waterway_412_Overview_9_2020.pdf
Fiener, P. & Auerswald, K. (2003). Concept and effects of a multi-purpose grassed waterway. Soil Use and Management, 19, 65-72. https://doi.org/10.1111/j.1475-2743.2003.tb00281.x
Arora, K., Mickelson, S. K., & Baker, J. L. (2003). Effectiveness of Vegetated Buffer Strips in Reducing Pesticide Transport in Simulated Runoff. Transactions of the American Society of Agricultural Engineers, 46(3), 635-644. https://doi.org/10.2134/jeq2008.0266
Bryan, G. G., & Best, L. B. (1991). Bird Abundance and Species Richness in Grassed Waterways in Iowa Row Crop Fields. The American Midland Naturalist, 126(1), 90-102. https://doi.org/10.2307/2426153
Dermisis, D., Abaci, O., Papanicolaou, A. N., & Wilson, C. G. (2010). Evaluating grassed waterway efficiency in southeastern Iowa using WEPP. Soil Use and Management, 26, 183-192. https://doi.org/10.1111/j.1475-2743.2010.00257.x
Glover, J. D., Cox, C. M., & Reganold, J. P. (2007). Future Farming: A Return to Roots? Scientific American, 83-89. https://landinstitute.org/wp-content/uploads/2007/08/Glover-et-al-2007-Sci-Am.pdf
Miller, T. P., Peterson, J. R., Lenhart, C. F., & Nomura, Y. (2012). The Agricultural BMP Handbook for Minnesota. Minnesota Department of Agriculture, pp.84-86. https://www.house.mn.gov/comm/docs/AG-BMPHandbookforMN_09_2012.pdf

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Grassed Waterways photo 1 — Photo 1: Contour buffer strips offer a strategy to reduce erosion and retain nutrients on sloped cropland.

Iowa NRCS photo by Jason Johnson.

Grassed Waterways photo 2 — Photo 2: Ephemeral gully erosion on hillside with contour buffer strips used to control it.

Iowa NRCS photo by Jason Johnson.