Probabilistic Risk Assessment of Coupled Natural-Physical-Social Systems: Cascading Impact of Hurricane-Induced Damages to Civil Infrastructure in Galveston, Texas

The combined effect of storm surge and wave action during severe storms in coastal regions can cause significant damage to civil infrastructures with cascading consequences to coastal communities and their residents with respect to emergency response, repair, and recovery. This coupling of natural, physical, and social systems presents an important yet relatively underexplored problem in the probabilistic risk assessment of coastal systems. Not only does coupling exist among the built and social systems triggered by natural hazard events, but a wealth of sources of uncertainties inherent in modeling these systems also renders the problem more complex. This paper presents a framework for the probabilistic risk assessment of coupled natural-physical-social systems exposed to coastal storms. It departs from traditional literature in this area by considering interconnected coastal transportation and residential building infrastructure coupled with social systems-households in this case-focusing on households failing to respond to official calls to evacuate. A holistic multihazard risk assessment framework is posed for probing these coupled systems in the face of uncertainty. New hybrid risk metrics across built and social systems are proposed, including the probability of nonconnectivity to emergency services, time loss to access emergency services, and the number of nonevacuees at risk. The concept of a hot household is developed, at which a building with nonevacuees inside experiences collapse-limit failure and is disconnected from emergency services during a storm event. The proposed framework is applied to a case study on Galveston Island, Texas, considering uncertainties in storm frequency and intensity, damage to physical infrastructure (buildings, roadways, and bridges), and evacuation decisions of the population. The resulting models offer a foundation for risk-informed decision-making to enhance the resilience of coastal communities and provide new insight into the coupled performance of natural-physical-social systems in the face of coastal storms. (C) 2021 American Society of Civil Engineers.