A natural drainage way is graded and shaped to form a smooth, bowl-shaped channel. This area is seeded to sod-forming grasses. Runoff water that flows down the drainage way flows across the grass rather than tearing away soil and forming a larger gully. An outlet is often installed at the base of the drainage way to stabilize the waterway and prevent a new gully from forming.
These structures are used to help control the grade in natural and artificial channels. They may be used where the concentration and velocity of water requires a structure to stabilize the grade in the channel or to control gully erosion. These structures are designed to reduce the amount of sediment delivered to local streams and rivers.
Wetlands filter and collect sediment from runoff water, slow overland flow and store runoff water, they reduce both soil erosion and flooding downstream.
A filter strip is a strip of grass, trees or shrubs that filter runoff and remove contaminants before they reach water bodies or water sources such as wells.