A Physical Modelling Environment for Laboratory‐Scale Assessment of Rainfall‐Runoff Responses in Urban Areas

ABSTRACT A laboratory‐based physical modeling environment has great potential to reproduce the complex physical hydrologic phenomena and understand the interactions of rainfall‐runoff processes in a visual and informative manner. In this study, a three‐layer physical modeling environment was developed to represent the dynamics of runoff production from the urban drainage system. The three‐layer physical modeling environment consists of a rainfall simulator (the 1st layer), a surface drainage network (the 2nd layer) and a subsurface rainwater pipe network (the 3rd layer). The degree of homogeneity of the spatial rainfall distribution produced by the rainfall simulator ranged from 78.6% to 84.0%, which lies within an acceptable range in the rainfall uniformity. The physical catchment model accurately represented the dynamic characteristics of the catchment response in a natural system associated with differing rainfall intensities within a controlled laboratory modeling environment, particularly the magnitude, volume, and shape of the discharge hydrographs. The three‐layer physical modeling setup was implemented to identify the effects of stormwater management facilities such as the rooftop detention storage and the permeable road pavement on the urban rainfall‐runoff responses. The runoff reduction rates for the peak discharge and the total discharge volume showed a strong linearity with the percentage coverages of the stormwater management facilities. Functional relationships between the variables were established to provide intuitive criteria for the runoff reduction rates for a specific coverage percentage of the rooftop detention storage and the permeable road pavement. These results demonstrate the effectiveness of the three‐layer physical setup for modeling rainfall‐runoff processes within the urban drainage network.