| Summary: | This study provides the first global evaluation of both direct and indirect flood hazard impacts on road transportation networks. It constructs topological road networks for 2,564 human settlements, representing over 14 million kilometers of urban roads. It assesses their exposure to pluvial and fluvial flood risks under 10 scenarios, corresponding to different flood intensities (1:5 year to 1:1,000 year return periods). Under each scenario, the study analyzes direct infrastructure exposure and assesses the indirect effects of flood-induced mobility disruptions: route failures, travel delays, and travel distance increases. The results document a positive relationship between flood return period and flood impact (both direct and indirect). Compared with direct flood hazard exposure, the indirect impact of floods on mobility is more prominent and heterogeneous. The average share of the road network that is flooded by at least 0.3 meters is 3.64 percent (or 24.84 percent) under the 5-year (or 1,000-year) return period, yet 11.58 percent (or 65.67 percent) of the simulated trips fail in the same scenario. The results enable comparisons of exposure and vulnerability of road networks to flood hazards across countries, allowing the identification and prioritization of urban transport resilience measures
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