Assessing the temporal qualities of indirect impacts of flooding on traffic

This study presents a detailed assessment of the temporal characteristics of indirect and cascading impacts of flooding on urban traffic, using the 2013 Calgary flood as a case study. It integrates hydraulic flood modelling (HEC‑RAS) with microscopic traffic simulation (SUMO) to examine how rainfall, flood progression, and post‑flood recovery influence mobility across different phases—before, during, and after inundation. The paper highlights how flood‑related disruptions increase delays, rerouting, and unmet trips, with rainfall compounding these effects. It also proposes a theoretical framework to distinguish direct, indirect, compounded, and cascading impacts on transportation networks, offering insights relevant for disaster risk reduction. 

The study recommends adopting integrated hydrological–traffic modelling to better anticipate secondary and cascading disruptions during extreme weather events. It underscores the value of dynamic routing, realistic driver‑behaviour modelling, and penalty‑based metrics to capture unmet demand and incomplete trips—factors often overlooked in traditional assessments. The authors suggest that urban planners and emergency managers should incorporate staged flood progression, rainfall effects, and early recovery dynamics into preparedness and response strategies. Strengthening data availability, refining origin–destination structures, and improving simulation calibration are identified as key steps to enhance future flood‑risk assessments and support more resilient transport networks.