Vegetated swales (also known as grass swales) are shallow areas built to store, filter, and transport small amounts of water before it gets to storm sewer system.

Usually vegetated with grasses, they can either have tall native grasses or turf. This makes them easy to maintain.

Among their benefits, swales:

• Divert water away from an area it will pick up pollution
• Slow water flow to prevent erosion
• Filter water to remove sediment and pollutants
• Allows small amounts of water to soak into the ground
• Create habitat (only when wild grasses are used)

They also reduce the temperature of water before it goes into a stream or pond -- a serious issue for sensitive species like trout.

Grass swales are easily maintained. The shallow nature of a swale allows for native plants necessary for stormwater best management practices like raingardens to be replaced by
turf. This can then be mown and maintained like the rest of the yard.  

Swales can be planted with native plants, which provide additional benefits such as habitat. Their deep roots also help break up compacted soils allowing for more space in the soil for
water increasing the amount of water that is soaking into the soil rather than running off into the storm sewer system.

For More Information: 

• View the Massachusetts LID Toolkit for more information on swale design.
• Rice Creek best management practices has a good description of swales
• View the Lake Superior Duluth Streams Site Design Tool Kit for grassed swales