Enhanced Grass Swale

Enhanced grassed swales are gently sloping conveyance channels with a designed underdrain system to filter or infiltrate stormwater runoff as it flows through the channel. Slopes of less than 2 percent are necessary to avoid swale erosion. These are best used along roadways and parking areas in moderate or low density residential or commercial areas.

Rooftop Runoff Management

Rooftop runoff management includes the use of cisterns or rain barrels and roof gardens to detain stormwater runoff. Rain barrels and cisterns collect runoff from roofs and store it for household use, such as garden watering. A green roof uses vegetation to soak up and evapotranspire rainfall, much like a bioretention area, before it is discharged. Green roofs require extra engineering to support the weight of the gardens, but can be highly effective in removing pollutants.

Stormwater Wetlands

Stormwater wetlands are constructed to treat stormwater runoff by mimicking the physical, chemical, and biological functions of natural wetlands. Constructed wetlands consist of shallow pools that support wetland vegetation and wildlife. The natural processes remove pollutants from runoff before discharging to local streams and waterways.

Infiltration Trench

Infiltration trenches are devices that are designed to fill with stormwater runoff and let it soak into the surrounding soil. These devices allow the water to be filtered and allow biogeochemical processes in the soil to treat the water and remove pollutants. They are most effective for small drainage areas.

Pervious Pavement

Pervious pavement differs from conventional concrete or asphalt by using air spaces to allow infiltration and storage of stormwater runoff. Conventional pavement generates significant stormwater runoff. Pervious pavement can often reduce the size needed for stormwater detention elsewhere on a developed parcel. Pervious pavement is typically used in low-traffic areas such as parking stalls, emergency lanes, bike paths and sidewalks.

Filter Strip / Level Spreader

Filter strips are vegetated buffers through which diffused stormwater runoff is filtered. The system includes a forebay to dissipate concentrated stormwater runoff, a channel with a level spreader to diffuse the flow, and vegetated buffer or filter strip through which the diffused runoff flows before it enters a waterway or ditch. The buffer is intended to remove sediment and pollutants before it reaches the waterway.

Filter strips are vegetated buffers through which diffused stormwater runoff is filtered. The system includes a forebay to dissipate concentrated stormwater runoff, a channel with a level spreader to diffuse the flow, and vegetated buffer or filter strip through which the diffused runoff flows before it enters a waterway or ditch. The buffer is intended to remove sediment and pollutants before it reaches the waterway.