Modeling Soil Moisture Redistribution and Infiltration Dynamics in Urban Drainage Systems

Hydrological modeling has become a common approach for the design of stormwater management strategies, which increasingly rely on permeable and decentralized systems in order to mitigate the impacts of urbanization. In most applications, little attention is paid to the temporal variability of infiltration fluxes resulting from soil moisture redistribution between rain events. In this paper, a conceptual infiltration-redistribution model is introduced to investigate the importance of the description of infiltration fluxes for the modeling of sustainable urban drainage systems (SUDS). The model was first verified against the numerical solution of the Richards equation. Performance indicators simulated with the model for a large range of infiltration scenarios were then compared to those obtained using simpler approaches commonly used in urban hydrology. The model was shown to replicate, at a low computational cost, numerical solutions of the Richards equation. Regarding SUDS modeling, the results indicated that a correct description of the temporal variability of infiltration fluxes (1) may be needed for some configurations in order to assess long-term volume-reduction efficiencies, and (2) is more generally required when examining frequency-based performance indicators.