GUIDELINES / 1.0 Water Quality
1.16 Urban Runoff and Roadsides
Buffers for urban runoff can be effective for trapping sediment but are generally less effective for dissolved pollutants. Buffers may be ineffective for urban stormwater where high runoff volume converges on and is channelized through the buffer. Buffers need to be designed to prevent flows from inundating or bypassing the buffer.
Key Design Considerations
- Buffers are best suited for low to moderate density areas (less than 20 percent impervious cover).
- Flow length into a buffer should be less than 150 feet for pervious surfaces and less than 75 feet for impervious surfaces.
- A level spreader can be used to disperse concentrated flow along the width of the buffer.
- Other best management practices should be used with buffers including low impact development that minimizes impervious cover.
Vegetated roadside buffers can be used to improve water quality by filtering runoff. Use check dams to slow water movement and increase retention time. Select salt tolerant plants where road salt is used.