Impacts of green infrastructure implementation within the Neuse River Basin

American Rivers is advocating for implementation of Green Infrastructure (GI) as a stormwater management strategy within the City of Raleigh. Incorporation of GI into future development plans is an appealing option for growing urban centers to minimize their impact upon surrounding aquatic ecosystems. Since Raleigh lies outside the regulatory boundary of the Falls Lake Nutrient Strategy, there is not a significant driver in place to encourage a shift towards GI. This study provided American Rivers with estimates of potential scale of GI retrofit implementation within a highly developed stormwater drainage basin, as well as the benefits those retrofits would provide in terms of nutrient load and peak flow reductions from stormwater flow. This was accomplished through the development of a GIS tool that identifies potential GI retrofit locations within Raleigh stormwater drainage basins, expediting the retrofit field reconnaissance process. The outputs of this tool were then incorporated into PLOAD, a GIS-based pollutant load modeling application for watershed-scale management, which provided estimates of mass loading rates of TN, TP, and TSS. The study area consisted of 11 subcatchments within Pigeon House Branch stormwater drainage basin (3200 acres, ~32% mean impervious coverage). Estimated annual pollutant load reductions resulting from GI implementation were 0.67, 9.92, and 16.82 tons of TP, TN, and TSS, respectively, although the accuracy of these numbers is questionable due to the coarse scale at which PLOAD operates. Ideally, other modeling efforts can be applied within this study’s framework to produce more informed scenarios within other drainage basins throughout the Neuse River Basin.