Design Elements — Green Stormwater Infrastructure

Green Stormwater Infrastructure (GSI) is a nature-based stormwater management solution that aims to preserve water quality while also providing additional ecological and social benefits. Green infrastructure is distinct from traditional "gray infrastructure" in that it attempts to utilize natural processes to store, infiltrate, or evapo-transpirate stormwater runoff to reduce overland flow into streams and waterways. Green infrastructure is better able to treat and reduce stormwater at its source, while also providing additional economic and aesthetic benefits to the community. Green infrastructure can help cool the surrounding environment and soak up flood waters, making it a smart choice for the changing climate. Examples of GSI include rain gardens, vegetated swales, stormwater planters, and continuous tree trenches.

Ordinance Considerations

The County-wide Model Ordinance encourages implementing green infrastructure to meet the water quality and runoff volume requirements of the ordinance. The Ordinance also includes a Conservation Design and Low Impact Development Site Design handbook (Appendix B) that can be used as a resource to assist with the stormwater management site design process. This handbook promotes a hierarchy of types of BMPs to encourage the use of those practices that best suit the conditions and needs of the municipality. For example, BMPs that reduce the volume of runoff and enhance groundwater recharge of stormwater are prioritized (given suitable site conditions) over traditional detention ponds and gray infrastructure, like concrete convenances and subsurface detention systems.

Specifying appropriate landscaping for BMPs is critical to their functional and aesthetic performance. Most green infrastructure practices encourage the use of native plant species that are adapted to site-specific conditions. Proper species selection, installation, and maintenance is critical to ensuring that these systems continue to function as designed. Operation and maintenance plans that detail the maintenance and inspection requirements for each BMP should be developed for all stormwater management systems. Provisions for stormwater management facility landscaping are generally found in the Subdivision and Land Development ordinance.

Suggested Ordinance Language

Good Examples