Vegetated Swales
Vegetated swales, either natural or manmade, are shallow channels filled with dense vegetation designed to slow water, increase infiltration and filter sediments. Swales are generally used in conjunction with other stormwater practices such as rain gardens but can be used alone. They are not suitable for every situation. The area must be able to support dense vegetation to prevent erosion of soil. This limits swales to locations that receive a lot of sun. Flat areas will not drain properly and a rain garden should be considered instead. High gradient sites, slopes greater than 4%, and sites with large volumes of water may be suitable if additional techniques are employed such as check dams, but a professional should be consulted. Swales are similar in shape to rain gardens, they are broad, shallow dish shapes, though swales tend to be longer. They should be about 1% in size of the drained area.
| Pollutant Median | % Removal |
| Total Suspended Solids | 81 |
| Oxygen Demanding Substances | 67 |
| Nitrate | 38 |
| Total Phosphorus | 9 |
| Hydrocarbons | 62 |
| Cadmium | 42 |
| Copper | 51 |
| Lead | 67 |
| Zinc | 71 |
