Accumulated impacts of imperviousness on surface and subsurface hydrology-continuous modelling at urban street block scale

To quantify the hydrological effects of disconnected impervious area is significant for urban planning and storm water management. Most relevant studies were event-based analysis and only focused on surface runoff. The accumulated impacts of disconnected imperviousness on both surface and subsurface runoff have not been fully understood yet. In this study, a physically based model coupling surface runoff, subsurface runoff and evapotranspiration was constructed for continuous simulation of the hydrological processes in an RPA (receiving pervious area)-DIA (disconnected impervious area) system at street block scale. Five RPA types with natural clay loam, compacted clay loam, natural sandy clay loam and depressed clay loam were considered. For each RPA type, urban development scenarios with varying disconnected impervious area ratios (DIRs) were designed. The results presented that both the annual total and averaged event-based surface runoff followed a generally Power form relationship with DIR for all the RPA types, which can be satisfactorily described by a concise and meaningful formula. Disconnected impervious surface can lead to higher event-based initial soil moistures, and it is much more significant when during dry months (autumn and winter) with less potential evapotranspiration intensity than during wet months (spring and summer). This results imply the importance to take the potential increased initial soil moisture of RPA and the corresponded increased runoff generation into consideration of storm water management when imperviousness disconnection is applied. At last, with the increase of DIR, the annual total groundwater recharge had a tendency to rise first and then decrease. This proves the possibility of improving underground water resource storage or maintain the groundwater recharge to the predeveloped level in the process of urban imperviousness expanding. Since this simulation work lacks on-ground validation, further studies based on the conclusions are still needed from the perspective of measured data analysis in urban RPADIA system.

Automated summary

Quantifying the hydrological effects of disconnected impervious area is important for urban planning and storm water management. This study constructed a physically based model to simulate the continuous hydrological processes in an RPA-DIA system. The results showed that disconnected impervious surface can lead to higher initial soil moisture and increased surface runoff, with the relationship between event-based surface runoff and disconnected impervious area described by a concise formula. Furthermore, the study suggested the possibility of improving underground water resource storage or maintaining groundwater recharge with the expansion of imperviousness.