| A hydrologic and hydraulic model was designed to model green stormwater infrastructure in New York City, particularly GreenStreets. GreenStreets are a type of source control that utilize bioretention to reduce stormwater runoff Three GreenStreet sites were analyzed to see how well they performed, and how the best way to model them would be. Three models were developed. Model 1 accounted for hydraulics and interception. Model 2 was a SWMM model that did not account for hydraulics or interception. Model 3 behaves the same way that the SWMM model does except that it accounts for hydraulics, in part, to see how sensitive the results are to hydraulics. The interception at each GreenStreet site predicted about 32% capture of the gross precipitation per storm, but only about 7% of the total precipitation. The large difference exists because interception captures a small percentage of large storms, which can account for a large portion of the gross precipitation, and a large percentage of frequent small storms. The inlets that were perpendicular to incoming flows did not appear to limit the retention at a GreenStreet. However, Furmanville in Queens which has a perpendicular inlet did not perform well because it lacked sufficient internal storage space to retain the flows. At the Nashville site in Queens, the larger bioretention area rejects flow into the smaller bioretention area if its inlet cannot accommodate the flow. This is an inefficient design. The inlets that were parallel to incoming flows at Sagamore in the Bronx, performed poorly compared to models that did not account for hydraulics, with differences in performance as high as 30%. It is recommended that GreenStreets are built with inlets that are perpendicular to incoming flows and with sufficient internal storage volume to retain a probable flow from its catchment area. |
