Masateru Senge, Ryouji OOMORI, Akinori KAJIKAWA, Kentarou OOTUKA, Masayuki TOYOTA, T. Mäki
This study investigates the runoff delay effects of lightweight engineered soil made from volcanic gravel, used in rooftop greening. Laboratory tests under varied rainfall and moisture conditions informed a simplified unsaturated infiltration model based on Darcy’s law. Regression analysis enabled the prediction of runoff delay using rainfall intensity, infiltration rate, and initial moisture. Assuming infiltration parameters are independent of soil thickness, simulations evaluated thickness effects. The study offers a quantitative method for assessing rooftop greening’s role in urban flood mitigation. These findings provide a practical method for evaluating runoff mitigation in urban green roof applications.