Extreme Rainfall Induced Flood Risk Assessment Model and Resilience Enhancement Method on Metro Networks

In recent years, the global climate change-induced flood risk has posed great threats to the safety of the most important geotechnical infrastructure in mega-cities, namely the metro networks. A highly networked metro system will lead to a quicker spread of risks, and furthermore, the impact range of single-node accidents is nonlinearly amplified due to the complex underground interconnections of tunnels. This paper develops a method to assess the influence of extreme rainfall uncertainties on metro systems based on a multi-layer network model combining with Areal Reduction Factor. This method can not only analyse the uncertainties of rainfall centres and rainfall spatial distribution, but also can reflect the drainage conditions by runoff parameters in certain geotechnical sites. By incorporating rainfall intensity and spatial distribution parameters, taking Shanghai metro as an example, the method demonstrates how increased rainfall and spatial uncertainties amplify flood risks, particularly affecting central urban areas with higher station density and connectivity. This paper highlights the system's vulnerability to extreme rainfall events, characterized by the finding that nearly 50% of extreme rainfall events result in less than 5% network loss, whereas fewer than 5% of the events lead to more than 50% network loss. In order to enhance the resilience of metro networks, this paper also assessedstrategies to improve the drainage conditions. The resilience enhancement strategy aims to ensure the sustainability of geotechnical engineering and urban transportation in the long-term urban renewal process.

Keywords: Uncertainty analysis, Risk assessment, Resilience enhancement, Metro flooding, Extreme rainfall, Multi-layer network.