Coupling a Distributed Time Variant Gain Model into a Storm Water Management Model to Simulate Runoffs in a Sponge City

Abstract

The storm water management model (SWMM) has been used extensively to plan, implement, control, and evaluate low impact development facilities and other drainage systems to solve storm-related problems in sponge cities. However, the calibration of SWMM involves a variety of sensitive parameters and may bring significant uncertainties. Here we incorporated the distributed time variant gain model (DTVGM), a model with a simple structure and few parameters, into the SWMM (called DTVGM-SWMM) to reduce the complexity but keep the mechanistic representation of the hydrological process. The DTVGM runoff module parameters were calibrated and validated using the Nash–Sutcliffe efficiency (NSE), based on measured data and the results of SWMM. It was then coupled with the SWMM routing module to estimate catchment runoffs and outflows. Finally, the performance was evaluated using NSE (0.57~0.94), relative errors of the flow depth (−7.59~19.79%), and peak flow rate (−33.68~54.37%) under different storm events. These implied that the DTVGM-SWMM simulations were generally consistent with those of the control group, but underperformed in simulating peak flows. Overall, the proposed framework could reasonably estimate the runoff, especially the outflow process in the urban catchment. This study provides a simple and reliable method for urban stormwater simulation.