French Broad River Watershed
Education and Training Center
Stormwater BMPs
Rain Gardens/Bioretention Cells
Rain gardens (also called bioretention cells) treat runoff before it is discharged to streams and rivers. Stormwater is pooled in a shallow basin with a high infiltration soil. As water infiltrates through the rain garden, pollutants like sediment and trash are filtered, and metals and excess nutrients can be reduced by the plant roots in the soil. Attractive plants like native grasses, flowers, and shrubs that can withstand both extended wet and dry conditions are best suited for rain gardens.
Examples:
Green Roof
A green roof is a layered roofing system installed directly on top of a building. It captures and treats rainfall and can be designed to enhance energy efficiency for the building. Plant selection is important as the green roof faces a variety of extreme conditions including heat, wind, and freezing temperatures. Green roofs absorb a large volume of water, have better heat and noise insulation than traditional roofs, and can also reduce the ‘heat island’ effect in urbanized areas.
Examples:
Stormwater Wetlands
Stormwater wetlands use natural processes to treat stormwater. They are basins designed with a permanent pool of water that fosters habitat for mosquito predators. These basins are planted with native wetland plants and can provide excellent wildlife habitat. After a storm, stormwater temporarily ponds and pollutants such as sediment and trash settle out and pollutants like metals and excess nutrients are removed by biological reactions within the soil and plants. Treated stormwater slowly drains over several days to make room for the next storm.
Examples:
Water Harvesting
Cisterns and rain barrels harvest rainwater from rooftops and temporarily store it for irrigation, washing vehicles, laundry, and flushing toilets. Stored water is most easily used for nonpotable (nondrinkable) purposes. The size of water harvesting systems can range from less than 100 gallons for home use (rain barrels) to more than 10,000 gallons (cisterns). They can be installed either above ground or entirely underground and can be made of plastic, metal, or concrete, depending upon the cistern’s use, size and location.
Examples:
Permeable Parking
For many developments, the availability of space can limit the ability to implement stormwater best management practices. Permeable parking is an excellent way to utilize limited space and store, treat and cool stormwater runoff onsite while promoting infiltration in certain settings. Parking areas can be created using permeable pavers, permeable concrete and asphalt.
Examples:
Map of Project Sites
