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.