Hierarchical fuzzy expert system for risk of failure of water mains

In Canada and the United States, there have been 700 water main breaks per day costing more than CAD 6 billion since 2000. Risk of failure is defined as the combination of probability and impact severity of a particular circumstance that negatively impacts the ability of infrastructure assets to meet municipal objectives. The presented research in this paper assists in designing a framework to evaluate the risk of water main failure using hierarchical fuzzy expert system (HFES). This system considers 16 risk-of-failure factors within four main categories representing both probability and negative consequences of failure. Results show that pipe age confers a strong impact on risk of failure followed by pipe material and breakage rate. They also show that damage to surroundings has the most negative consequence of a failure event. A set of municipal water network data are collected and used to examine the developed HFES. According to the proposed scale of risk of failure, about 8.4% (13 km) of the network's pipelines are risky and require mitigation actions in the short term.