How do swales function?
Generally, swales receive stormwater from adjacent roadways and other paved areas. Usually swales are covered in grass and the grass removes some of the dissolved nutrients that may be present in the stormwater. The grass also slows down the velocity of the stormwater and helps settle out sediment and particulates washed off the roads. Many times, swales are designed to hold water for up to 72 hours during which time they percolate the captured stormwater into the soil.
