Vegetated swales are broad, shallow channels with dense vegetation (often grass) covering the side slopes and bottom. Swales can be natural or man made, and serve to trap particulate pollutants, increase infiltration, and reduce the flow of stormwater runoff. A swale is much shallower than a ditch, and is designed to be easily maintained by lawn equipment such as on the sides and medians of highways. Vegetated swales are best used in conjunction with wet ponds, infiltration strips, constructed wetlands and rain gardens, but can exist as stand alone features as well.