Compound flooding escalates unequal access to critical facilities in urban areas

Urban road networks underpin human mobility, economic activity, and timely access to essential services. Yet these lifelines are increasingly susceptible to climate‑driven compound flooding, when fluvial, pluvial and coastal processes interact to create complex urban inundation scenarios. While resilience assessments have begun considering equity, many fail to account for the nuanced impacts of hazard driven infrastructure disruptions on sub-populations' access to critical facilities. Here we examine how compound flooding events reshape access to hospitals, shelter houses, and transportation centers across a representative coastal metropolis of Boston by combining a high-resolution 1D–2D hydrodynamic flood model with dynamic mesoscopic traffic simulation. This approach captures both street-level inundation and evolving traffic conditions, including rerouting and congestion during extreme events. We evaluate changes in travel time to critical facilities under both normal and flood conditions. Results reveal that even localized flooding can lead to widespread travel delays, significantly reducing or even eliminating access to emergency services. Further, these disruptions are spatially unequal, with socially vulnerable neighborhoods experiencing significantly longer delays. Our findings highlight the need for resilience strategies that not only maintain system functionality but also ensure equitable access. This includes distributed siting of critical services, adaptive traffic management, and nature-based flood mitigation to reduce future systemic risks.