Graph Method for Modelling Multiple Pipe Failure Scenarios in Urban Drainage Networks

Urban drainage networks (UDNs) ensure protection of humans from harmful impacts of nature as well as nature from negative anthropogenic impacts. These networks are under pressure both internally (structural failures) and externally (functional failures) and hence require efficient modelling strategies for their management and maintenance. Most of literature on pipe failure modelling in UDNs focuses on single pipe failure analysis, while there are very few studies that target multiple pipe failure scenarios while considering cascading failure. One reason is that systematically evaluating different combinations of multiple pipe failure using conventional hydrodynamic modelling methods is computationally very expensive. Considering this research gap, a novel graph-based method is presented in this study for evaluating multiple pipe failure scenarios in UDNs. The presented method evaluates the overall flooding impact on the system when different combinations of pipes fail together. The number of possible combinations increases tremendously with increasing number of pipes failing. Graph-based method is used to find the most critical failure combinations. The results show that the proposed graph-based methodology overestimates flooding volumes as compared to hydrodynamic modelling results but can still be used reliably to recognize the critical combinations. In terms of computational time, the graph-based methodology is much more efficient as it is a non-iterative method and hence a lot of pipe failure combinations can be evaluated in a reasonable time. Furthermore, a hybrid graph and hydrodynamic approach is also discussed, combining the accuracy of hydrodynamic modelling with efficient computational time of graph method.