Modelling Green and Grey Stormwater Infrastructure Using a 2D Model for New York City

Stormwater management strategies, or interventions, play a critical role in protecting urban regions from flooding. Stormwater interventions are used to enhance the resiliency of cities to changes in climate, sea level rise, land development, as well as other considerations that result in an increased likelihood of flooding. Interventions may include grey, green, and hybrid interventions that are designed and deployed individually or in combination within a comprehensive strategy. Interventions within New York City have been used to address issues such as flood prevention, water quality control, improved resiliency of communities to climate change, and improved livability, ecosystem integrity, and human health. Through this study, thirteen two-dimensional hydrologic and hydraulic models were developed to represent the entire city of New York and a comprehensive analysis was conducted to evaluate the effects of green and grey infrastructure for reducing maximum flood depths, reducing combined sewer overflows and increasing the quality of life in New York City through various co-benefits. In this study, a new approach for modelling green infrastructure within a 2D model was developed and used to evaluate the potential impact green infrastructure can have for five precipitation events ranging from small, 25mm events to extreme, 230 mm events. The primary findings of the study are presented as well as several lessons learned from modelling large urban areas with a 2D model.