The Impacts of Green Infrastructure on Flood Level Reduction for the Raritan River: Modeling Assessment

The Raritan River has a history of overflowing its banks and causing substantial damage to nearby townships and boroughs. In this study, a hydrological model was developed for the Raritan Basin. The calibrated model was subsequently used to compute the reduction in stream flow as a result of implementing sufficient green infrastructure to reduce runoff depth by one inch throughout a chosen watershed management area. To simulate the runoff reduction, the curve number corresponding to the reduced runoff was back calculated. Changing the curve number also changes the lag time and initial abstraction so these values were adjusted accordingly. In terms of discharge, the peak flow would pass from approximately 30,000 cfs to just under 20,000 cfs. The reduction in the stream was then translated to the reduction in the stream water level using the established rating curve. The types of green infrastructure that can be used to reduce one inch of runoff were also assessed, and their costs were estimated as well.