Interface Network Models for Complex Urban Infrastructure Systems

The reliability assessment of infrastructure systems providing power, natural gas, and potable water is an integral part of societal preparedness to unforeseen hazards. The topological properties of interface networks connecting electric substations to water pumping stations and natural gas compressors have received little attention, despite the key role these connections play in operation and failure propagation. This work introduces a performance assessment methodology for coupled infrastructures that links physical fragility modeling with the topology of realistic and ideal connecting interfaces. Distinct interfaces based on features such as betweenness, clustering, vertex degree, and Euclidean distance are assessed regarding their role in connecting utility systems and propagating failures from random and hurricane events in Harris County, Texas. The interface minimizing the Euclidean distance between electric substations and other utility nodes exhibits a slow performance decline as random failures increase, and retains the greatest functionality under hurricane events compared to alternative interfaces, although it suffers from limited efficiency and controllability during normal operation. A convenient hybrid interface using both betweenness and distance features shows adequate performance during normal operation while exhibiting tolerance to random failures and sufficient performance at increasing hurricane event levels. These findings provide utility owners and operators with new simple yet adequate strategies focused on the interface across complex systems to enhance routine operation and reduce the probability of widespread interdependent failures following disruptive events.