Identifying Responses to Changing Climate Conditions in a Multiple Green Stormwater Infrastructure as a Single System

Abstract

As research on green stormwater infrastructure (GSI) and its implementation in cities has increased, we can move beyond understanding the performance of multiple GSI functions as a system to how they respond to changing climate conditions. While models have been utilized in the past, they may be based on the performance evaluation of an interconnected system consisting of ten rain gardens, two cisterns, a detention basin, three infiltration systems, and a bioswale that was evaluated and do not accurately represent the future efficiency of the system while climate change is imposed. Over the course of this investigation, the climate change response of an interconnected system was evaluated. Additionally, the variability of response between rain gardens of an interconnected system and how the interconnected GSI system responds to urban stressors (the heat island effect) were evaluated. The 16 GSI were retrofitted alongside multiple new residence halls on a nine-acre parking lot at Villanova University. Upon comparing the response of the observed storm runoff to that of the projected near- and far-term runoff, it was determined that the total discharge volume for a variety of rainfall events has increased by approximately 2–16.9 percent, the average flow increased by approximately 1.8–15.7 percent, and the maximum outlet flow increased by approximately 1.8–18.6 percent based on the size of the rainfall event for two individual climate projections. The post-construction model SWMMCAT climate prediction observations from this study revealed an overall increase in peak flow and volume for both climate scenarios, indicating that the GSI system has the probability of getting excess water in the future. However, as the GSI system is a combination of storage structures (detention basins, cisterns, and infiltration trenches) and rain gardens, it can successfully mitigate the increasing effects of stormwater runoff and peak flow if properly monitored. With these observations, some monitoring keys have been proposed to increase the efficiency of the GSI as an integrated system if climate change is imposed. When comparing the overflow events for all rain gardens, it is determined that the performance of rain gardens was similar to the previous year's results, except for more overflow events in 2023. So, proper monitoring and continuous charting of observed variables can help to maintain the system's efficiency in the future if extreme storms arise or overflow in rain gardens becomes more frequent. GSI has also demonstrated its effectiveness in mitigating the urban heat island effect. Therefore, the multidisciplinary design of the interconnected GSI, which includes rain gardens and storage, can successfully handle extreme future storms in a variety of climate change situations.