Routing Optimization Framework for Exploring Time-Varying Urban Road Network Vulnerability under Floods

This work investigates the problem of vehicle routing and assessment of road network vulnerability during extreme flood conditions by considering inundation levels and their effects on road availability and travel speeds. A stormwater model is used to estimate street-level inundation during three major hurricanes that passed through Wilmington, North Carolina—Florence, Matthew, and Dorian—to determine how different storms can affect the road network system. Toward this, an optimization model was developed that uses flood versus speed reduction functions to integrate flood levels to estimate decreasing the number of available arcs and reducing the interconnectivity of different regions over time. A comparison of the road network analysis using flood estimates from the stormwater model and the 100-year flood maps from the Federal Emergency Management Agency of the United States was performed, and overall results indicate the importance of storm-specific flood estimates to assist emergency planners in the definition of critical roads and affected areas. The paper also explores how different regions are affected during various flood severity levels and identifies areas of vulnerability. It introduces severity scenarios based on route feasibility, shedding light on the dynamic nature of flood impact, and concludes by highlighting the influence of flood changes on the importance of specific road segments in network planning and operation.