Evaluation of drainage networks under moving storms utilizing the equivalent stationary storms

Abstract

This paper investigates the effect of rainstorm movement on the peak discharge response (PDR) of drainage networks by comparing it with the corresponding equivalent stationary and uniform rainfall. A synthetic circular watershed is introduced to avoid biases from interaction between catchment geometry and storm orientation. The drainage network of the watershed is simulated by the Gibbsian model to examine the effect of network configuration on the peak response depending on the storm kinematics. This study utilizes two types of the equivalent stationary storm (ESS): the average rainfall intensity over the entire catchment (ESSAV) and the point stationary rainfall intensity (ESSQ) to evaluate the effect of moving rainstorms in terms of the PDR. The results show that there exists an interval in which the same rainfall duration produces higher peak responses for moving storms compared with ESSQ. The augmentation of the peak response by moving rainstorm is dependent on the relative rainstorm speed, size, and direction as well as drainage network configuration of the catchment; especially, the results show that a less efficient network tends to mitigate the effect of rainstorm movement on peak response. In contrast, a more efficient network is more sensitive to storm kinematics and the peak response increases compared with ESS. Therefore, the results in this study imply a potential improvement in urban drainage networks in terms of efficiency as well as safety to moving rainstorms. Also, this study suggests the range of variation in peak flows due to storm kinematics compared with the ESS, which can be a reference to the current design practices.