As cities all over the world become increasingly developed and urban, stormwater management becomes an issue. The impervious concrete and asphalt surfaces causes rain to directly run off into the city’s stormwater infrastructure. At the same time, climate change is causing an increase in intensity and frequency of storms. For these reasons, urban cities must pay close attention to the present and future needs of their stormwater management. Because infrastructure such as sewers, tanks, and treatment plants are very costly, city agencies have been looking to other solutions to manage stormwater.
One solution that has been gaining popularity is green infrastructure. Green infrastructure is a cost effective alternative to traditional infrastructure. It also provides many additional benefits because of its use of vegetation. Streetside bioswales are a type of green infrastructure that can be implemented by government agencies in the public right-of-way. Cities that currently have bioswales in operation include Portland, Seattle, and New York City.
Green Infrastructure[edit | edit source]
Green infrastructure (GI) uses natural and sustainable methods to manage stormwater. Some examples of green infrastructure are green roofs, streetside bioswales, and rain gardens. In addition to capturing runoff, green infrastructure provides many additional benefits such as beautifying neighborhoods, reducing the heat island effect, and increasing biodiversity. In addition, an important benefit of green infrastructure is improving air quality by reducing CO2. In the beginning, green infrastructure requires maintenance to ensure that plants are healthy and developed. Overtime, green infrastructure has the ability to sustain itself with little to no maintenance. The benefits generally increase over time, as the plants thrive.
Unlike green infrastructure, grey infrastructure (sewers, tanks, treatment plants, etc.) takes significantly longer to design and construct. Upgrading NYC’s sewer system to its needs would take billions of dollars. Grey infrastructure provides no additional benefits other than its purpose. Its functionality decreases over time, and a large amount of maintenance is needed as the years progress.
Right of Way (ROW) Bioswales[edit | edit source]
ROW bioswales are designed to capture street runoff, diverting it from the sewer system. They have notches in the concrete curb at the inlet and outlet that allow water to be retained in the bioswale and for excess runoff to empty into an usually adjacent catch basin downstream. ROW bioswales are typically divided into two layers, with the top layer composed of engineered soil that promotes water filtration and the bottom layer composed of drainage media that allows stormwater to infiltrate into the ground or be stored for a period of time in the structure itself. Drainage media could include sand, gravel or crushed stone. Some ROW bioswales contain stormwater chambers that maximize the water storage.
Vegetation, especially trees, also play an important role by up-taking water during storm events and releasing via evapotranspiration. Most bioswales are planted with plants and trees native to the area that are resistant to dry/wet weather and hardy to pollutant loadings. By building many of these bioswales around urban cities, the amount of combined sewer overflow can be reduced, therefore reducing the amount of pollution in surrounding waterways during heavy storms.
Additional Benefits[edit | edit source]
- improving air quality
- reduced pollutant loading
- reduced urban heat island effect
- increasing biodiversity
- cost effective
- energy savings
[edit | edit source]
-  NYC Green Infrastructure Plan