Historically, the work of stormwater engineers has involved capturing rainwater and conveying the flows offsite as quickly as possible. This approach led to the development of a vast system of large, centralized treatment facilities handling millions of gallons of stormwater annually – a very efficient, but not very environmentally-minded solution.
After decades of development that prioritized efficiency over ecology and short-term convenience over long-term benefits, there has recently been a major shift in how we approach this design problem. Green Stormwater Infrastructure (GSI) is a subset of low impact development (LID), an approach focused on stormwater management through techniques that mimic and/or restore the natural water cycle. GSI aims to decrease the amount of stormwater conveyed to these large municipal systems and to reduce the impacts of overflows and flooding events associated with their failures. This means that stormwater engineers are trading pipe flow rate equations for soil infiltration rates and designing systems that keep rainwater on the site, where it lands, thereby returning rainfall to the natural environment after cleaning it.
A byproduct of this shift is that not all land developers and owners understand the advantages of adopting green stormwater infrastructure approaches. The success of these systems not only rests in their design, installation, and maintenance, but also in the successful education of those impacted by them. Site owners and developers must see and understand the value of these systems to support the architects and engineers who design them.
Here are nine talking points for designers to explain to owners and developers what they can expect from LID and GSI strategies – and why they’re often the better solution to stormwater management:
Low Impact Development techniques have positive environmental impacts
Evidence shows that the techniques of low impact development have a beneficial impact on the environment ( GSI performance research). By promoting the reduction of hardscapes and the increase of on-site infiltration, GSI results in sites that produce less surface water runoff, less pollution, better air quality, less erosion, and have reduced flooding impacts. Infiltration also recharges the groundwater aquifer and reduces the damage that urban run-off has on fresh water bodies (lakes and streams) and salt water bodies (estuaries and oceans), while also recharging base flows that are essential to fish and other wildlife.
Low Impact Development techniques include a greater diversity of drainage solutions
“Conventional” stormwater control facilities include catch basins, storm drain pipes, conveyance channels, and vault-type facilities. These structures and pipe networks provide a “capture and convey” approach to stormwater management. The techniques of LID provide a greater suite of distributed and infiltrative flow management approaches such as rain gardens, cisterns, pervious pavements and plantings (preservation of native areas/mature trees and restoration of landscapes and tree planting) techniques.
Low Impact Development techniques distribute stormwater management across the site
Through varied surface collection alternatives and widespread infiltration areas, LID techniques can provide a diversity of discharge locations — this supports maintenance of natural discharge locations and mimics the natural water cycle by promoting distributed stormwater management and infiltration. This also reduces the risk and impacts associated with failure of a single type of facility or single discharge point.