SWMM-based rainfall-runoff simulations in large-scale urban area with no pipeline-flow observations: Ⅱ: model calibration and analysis of rainfall-runoff simulations

At present, many cities in China are short of pipeline-flow observations, which leads to large challenges to construct urban hydrological models for detailed rainfall-runoff simulations. In this study, the core district of Yizhuang Economic Development Zone was selected as the study area. Based on the accurate digitalized land-surface data, field survey and empirical verification of urban storm process was carried out in terms of the maximum runoff depth at specific spots, and the SWMM model was calibrated and verified for the two typical storm events in July 21st, 2012 and June 23rd, 2011. Subsequently, the runoff response rate and traffic congestion risk of design rainstorms in different return periods were analyzed and evaluated in sub-catchments with various land-uses. The results show that as return period increases, street and transportation land-uses have a higher response rate to the increase of rainstorm than park and green land-uses do, and the former has a higher risk of waterlogging-triggered traffic congestion than the latter. This finding indirectly reflects the variability of runoff response rates under different land-surface conditions. This study is potential to provide decision-makers with valuable suggestions on effective local urban-flood control and early warning.