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Conservation Choices: Grassed Waterway

Grassed Waterway

Grassed WaterwayWhat it is

Grassed waterways are shaped constructed channels that are seeded to grass or other suitable vegetation to convey water to a stable outlet at a non-erosive velocity.

A structure is often installed at the base of the waterway to stabilize the waterway and prevent a new gully from forming.

How it helps

  • Grass cover protects the waterway from gully erosion and traps sediment in runoff water.
  • Vegetation can filter and absorb some of the chemicals and nutrients in runoff water.
  • Vegetation provides cover for small birds and animals.

Planning ahead

  • Is major land re-shaping needed?
  • Is there a proper outlet for surface runoff at the bottom of the waterway?
  • Are soil conservation measures installed to minimize siltation?
  • Will tile drainage be necessary to establish vegetation in the waterway?

Tech Notes

  • Shape a waterway so the depth halfway to the center is 3/4 of the depth at the center. For example, if the center depth is 1 ft., depth halfway to center is .75 ft.
  • The final graded waterway surface to be seeded should be reasonably smooth, free of rills and gullies, and has the designed cross section.
  • Silt fence fabric checks may be needed after grading and smoothing to reduce potential for gully erosion until seeding is established.
  • A firm seedbed increases the chance of a good grass stand. A roller or cultipacker may be needed to get a firm seedbed.
  • Apply fertilizer and seeding at rates recommended by NRCS.


  • Lift implements out of the ground and shut off spray equipment when crossing the waterway.
  • Inspect after heavy rains. Fill, compact, and re-seed areas damaged by the rain.
  • Don’t use the waterway as a roadway.
  • Avoid planting along the waterway. This prevents a new gully forming on the outside edges of the waterway.
  • Fertilize as needed.
  • Mow periodically, but wait until after Aug. 1 to benefit wildlife nesting.

Iowa Practice Standard

Iowa Job Sheet