Quantifying the ability of green infrastructure to reduce coastal zone pollution

With significant increase in the application of green infrastructure (GI) technology to mitigate urban coastal zone pollution caused by wet-weather-flow, the ability to quantify the stormwater retention of different green infrastructure designs is needed. In New York City (NYC), an aggressive 20-year plan proposes to use green roofs and other street level bioretentions, such as bioswales and green streets, to reduce the volume of polluted stormwater and combined sewerage that overflows into the City’s water ways. As a part of an NSF Coastal SEES project, we are actively quantifying the role of GI in reducing stormwater runoff and pollutant loading in a network of NYC green roofs and street level bioretentions. Green roofs and green streets manage only their incident precipitation, whereas bioswales also manage stormwater upstream of their footprint, depending on flow conditions and the inlet design. Conversely, green roofs are predominately planted with sedum species, whereas street level bioretentions have a much broader plant pallet. As a result, the performance of different GI systems requires different approaches. In this talk we will demonstrate the severity of coastal zone pollution in New York City (NYC), describe the current green infrastructure (GI) designs that the City is using to abate this problem, and present the experimental protocols and methods we have developed to assess and model urban GI performance. In addition to quantifying the stormwater retention performance of GI, these methods include quantification of the pollution added or removed from the GI systems. The talk will end with a discussion of our findings to date in the context of pollutant loading in the Bronx and Hudson Rivers, both of which impact the health of the local coastal zone.