Risk analysis of pipeline drainage capacity at typical time of urban rainstorm waterlogging process

Based on the storm water management model (SWMM), the urban waterlogging process in Zhengzhou High-tech Zone was simulated under rainfall events of varying magnitudes and types. An operational risk assessment system for the drainage network was developed, incorporating three primary indicators and several secondary indicators. The risk levels at four typical moments (rainfall peak, runoff peak, water accumulation peak, and one hour after rainfall) during urban rainstorm waterlogging were analyzed. The results show that the relative order of waterlogging risk across these key moments remains consistent for different types of rainstorms. Specifically, the risk level decreases in the following order: water accumulation peak, one hour after rainfall, runoff peak and rainfall peak. If the total rainfall duration and rainfall pattern are constant, the risk peak time of pipeline overload, node overflow and urban waterlogging shifts earlier as the rainfall magnitude increases. If the total duration and magnitude of rainfall are constant, the larger the rainfall peak coefficient leads to prolonged drainage times, more severe urban waterlogging, and a noticeable reduction in the time intervals between the critical moments.