A cascading risk and resilience assessment framework for urban lifeline systems under extreme flooding

Urban lifeline systems are essential for sustainable urban development, yet they face increasing threats from climate-induced extreme flooding. A comprehensive understanding of cross-dimensional cascading failures in these systems is critical for targeted flood risk reduction. To address this need, this study develops an integrated assessment framework combining cross-dimensional cascading failure models, social vulnerability assessment, and emergency recovery capacity assessment. Building on prior research, the framework extends cascading effect analysis beyond physical infrastructure networks to assess associated social impacts and emergency recovery efficiency. It quantifies the spatial scale and severity of flood impacts, sets priorities for emergency restoration, and offers risk mitigation strategies that can be adapted to other coastal cities with adjustments based on local contexts. Using Xiamen, a coastal city in China, as a case study, we constructed flood scenarios with inundation heights of 1m, 3m, and 9m to analyze spatial disruptions to infrastructure services and differential impacts on residents. The results show how cascading effects amplify the number of affected people. These findings identify high-risk zones facing the most severe impacts, supporting the design of targeted protection measures for vulnerable groups. We also identify critical infrastructure types and facilities, proposing targeted strategies to optimize emergency restoration priorities. These findings provide empirical support for disaster management authorities to refine climate adaptation policies and improve urban resilience against growing flood hazards.