Performance Assessment of SWMM 5.1 Green Roof LID Control in Modeling Runoff

Green roof is one of the emerging Low Impact Development (LID) technologies highly applicable in urban areas used to temporarily retain storm water. However, there are limited data available on their field performance. Thus, development of effective mathematical models is important to predict the runoff and evaluate the retention capacity of green roofs. The Storm Water Management Model (SWMM) is a widely utilized rainfall-runoff modeling software. It recently released its version 5.1 which includes green roof as a basic LID control and no study was found to evaluate it yet. Therefore, the goal of this study is to evaluate the performance of SWMM 5.1 Green Roof LID control in predicting runoff volume. The performance of sensitivity analysis showed that field capacity and wilting point are the most influential parameters that affect runoff volume. The highest NSE coefficient produced in the calibration was 0.508 which is considered unsatisfactory. This is due to the extreme overestimation in high runoff events. Further improvements involving factors affecting the drying of the substrate layer (e.g. evapotranspiration) are needed.