Time-dependent drainage capacity and runoff of pervious block subjected to repeated rainfall simulation

To mitigate flood damage in cities, pervious concrete has been developed as a viable and sustainable alternative to traditional concrete to facilitate drainage. Previous studies have tended to evaluate the drainage capacity of pervious blocks through permeability and drainage tests in simplified conditions, giving little consideration to multiple environmental factors such as rainfall rate and temporal changes in the blocks' drainage capacity. This study presents experimental results of the runoff and drainage capacity of pervious blocks subjected to time-dependent evaporation and corresponding changes in their degree of saturation. Different levels of repeated water charging at designated time intervals simulated the urban environment, and both runoff and drainage were continuously monitored. The results highlight that runoff can take place after certain time intervals despite the same water charge because of evaporation and prewetting-induced changes in water-retention capacity. The effects of the surface layer, the bedding layer, and clogging (all part of the urban areas) on the drainage were also observed. The findings underscore the significance of the actual, rather than the simplified laboratory-based, drainage capacity in urban areas.