Experimental Study on the Rainfall-Runoff Responses of Typical Urban Surfaces and Two Green Infrastructures Using Scale-Based Models

In this study, scale models of typical urban surfaces and two green infrastructures (concave grassland and porous pavement) were constructed, and two simulated rainfall intensities (low intensity was 0.3 mm/min with 25.4 mm depth, and high intensity was 0.6 mm/min with 42.0 mm) were utilized to investigate their runoff responses and the impacts of pervious surface positions and initial soil moisture on the runoff processes. Results indicated that impervious concrete surface exhibited a faster generation of runoff and with a runoff coefficient of 89%. Grassland surface represented that time to runoff was about 25 times than that of the impervious surface and recorded the smallest runoff coefficient of 34 and 53%. Compared with the impervious area, concave grassland was able to effectively delay time to runoff, while the porous pavement was able to significantly reduce runoff discharge and peak flow rate. A high rainfall intensity led to a reduction in time to runoff and an acceleration of runoff discharge and peak flow rate. Pervious surface under the lower side generated runoff at a slower rate, and registered a smaller runoff coefficient compared with the pervious surface under the upper side. The initial soil moisture and time to runoff had a significant negative correlation, and a positive correlation was found between the initial soil moisture and runoff coefficient. These findings facilitate a better understanding of runoff processes of urban surfaces and green infrastructures that may be able to help in better hydrology system design for mitigating urban flooding.