Urban Road Network Resilience to Flooding, a Global Evaluation

Road networks are the backbone of modern societies without which transportation operations and essential services would be paralyzed. Over the past few decades, multiple studies have revealed both the growing density and connectivity of road networks as well as their increasing vulnerability to both pluvial and fluvial flooding. Past research mainly focuses on the impact of flooding on roads in terms of accessibility, efficiency, vulnerability, etc. within local and regional scales. However, a comprehensive horizontal evaluation of urban road network resilience at the global scale is still absent. In this effort, we create a framework of metrics that captures different dimensions of network resilience including network dynamics, robustness, error and attack tolerance, susceptibility, centrality, etc. We leverage the publicly accessible Open Street Map (OSM) dataset for creating topological road networks for cities and the outputs from Fathom high-resolution global flood model for assessing pluvial and fluvial flood extent and inundation depth under ten return periods (1:5 year to 1:1000 year). We disrupt the road network under ten scenarios and apply the framework on city-level road networks for more than one hundred most populated cities worldwide and analyze the changes in multiple network resilience dimensions. A resilience index is calculated for each city based on their overall network resilience performance. The results of this study can support decision-making processes for international development agencies to identify as well as prioritize key cities around the world and their road components that warrant immediate mitigation of pluvial and fluvial flooding impacts. The framework developed in this study also provides a foundation for future network resilience research at global scales.