Graph method for modelling multiple pipe failure scenarios in urban drainage networks

Drainage networks in an urban environment ensure protection of humans from harmful impacts of nature as well as nature from 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 urban drainage networks focuses on single pipe failure analysis, while there are very few studies that target multiple pipe failure scenarios. 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 urban drainage networks. The presented method evaluates the overall flooding impact on the system when different combinations of pipes fail together. Number of different failure combinations studied can be represented by, ∏(c=0)^(N-1)〖N-c〗, where N is the number of pipes and c is the failure level, so for failure level 1 number of combinations will be N*(N-1). The flooding impact calculated using graph-based method is compared with the results obtained from hydrodynamic model. Results are compared in terms of accuracy and computational time requirements. The results show that the proposed graph-based methodology shows some differences as compared to hydrodynamic modelling results. However, in terms of computational time, 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.