Simulation of the cumulative hydrological response to green infrastructure

In this study, we evaluated the cumulative hydrologic performance of green infrastructure in a residential area of the city of Parma, Ohio, draining to a tributary of the Cuyahoga River. Green infrastructure included the following spatially distributed devices: 16 street‐side bioretention cells, 7 rain gardens, and 37 rain barrels. Data consisted of rainfall and outfall flow records for a wide range of storm events, including pretreatment and treatment periods. The Stormwater Management Model was calibrated and validated to predict the hydrologic response of green infrastructure. The calibrated model was used to quantify annual water budget alterations and discharge frequency over a 6 year simulation period. For the study catchment, we observed a treatment effect with increases of 1.4% in evaporation, 7.6% in infiltration, and a 9.0% reduction in surface runoff. The hydrologic performance of green infrastructure was evaluated by comparing the flow duration curve for pretreatment and treatment outfall flow scenarios. The flow duration curve shifted downward for the green infrastructure scenario. Discharges with a 0.5, 1, 2, and 5 year return period were reduced by an average of 29%. Parameter and predictive uncertainties were inspected by implementing a Bayesian statistical approach. Plain Language Summary Green infrastructure facilities experience a range of rainfall‐runoff events that are difficult to fully capture during a monitoring program. In this study, we evaluated the cumulative hydrologic performance of green infrastructure in a residential area of the city of Parma, Ohio, USA. Green infrastructure involved the following spatially distributed devices: 16 street‐side bioretention cells, 7 rain gardens, and 37 rain barrels. A hydrologic model was calibrated and validated to predict the hydrologic response of green infrastructure. The calibrated model was used to quantify annual water budget alterations and discharge frequency over a 6 year simulation period. For the study catchment, we observed a treatment effect with increases of 1.4% in evaporation, 7.6% in infiltration, and 9.0% reduction in surface runoff. Key Points Green infrastructure decreased the magnitude of discharges with a 0.5, 1, 2, and 5 year return period Street‐side bioretention cells exhibited the highest performance by disconnecting impervious areas from streets, driveways, and sidewalks A Bayesian calibration of the SWMM model considering the cumulative effects of several storm w