Increasingly, proponents of green building are realizing the potential of green site development strategies on the future sustainability of urbanized areas. In particular, alternative strategies for stormwater management are being implemented and show significant promise (US EPA 2003). As the global population becomes more urban, the increase of impermeable surfaces has deleterious effects on water quality and amounts of urban runoff. Traditional approaches to development and stormwater management have resulted in stormwater systems becoming a rapid conduit for delivery of contaminated runoff to rivers and streams. Volumes have increased, concentration times reduced, and natural filtering processes have been bypassed. The result is increased flooding, polluted rivers and streams, health threats, habitat degradation, and increasing expense to maintain inadequate systems. Many municipalities and other government agencies in the US and abroad are attempting to address this issue through regulation and incentive. The United States Green Building Council LEED system recognizes and addresses this problem and the potential for more sustainable stormwater management practices.
The benefits of green stormwater management strategies vary depending on the circumstances of each condition, but examples of lower cost and environmentally superior approaches are found in cities in the US and around the world. Integrating green strategies into new development projects, from planning stages through implementation, is the most cost effective and yields the most efficient and beneficial systems. Retrofitting existing stormwater management systems in cities can be more costly and provide more limited environmental benefits, but antiquation of existing systems creates opportunities to adapt and include green strategies as systems are rebuilt, updated, and improved (Kloss and Calrusse 2006).
It is best to think of green stormwater management strategies holistically, allowing the most efficient opportunities for integration of techniques into the planning, design, and implementation process. These approaches are sometimes represented as green infrastructure (Dunn and Stoner 2007). They are cost effective, sustainable, and environmentally friendly. In general, green infrastructure uses natural systems to the greatest extent possible, but also uses engineered systems that mimic natural systems to collect, treat, and reduce stormwater runoff using plants, soils, and microbes. At broader scales, green infrastructure can consist of a set of connected natural and human-created open space elements that may include forests, flood plains and riparian corridors, wetlands, parks, and more. In addition to the stormwater management benefits provided, recreational activities and wildlife habitat are often accommodated.