Indirect costs of floods: a case study of highways road users

Hydrometeorological events have a significant impact on road infrastructure and traffic flow. Floods can collapse or weaken bridges, compromise river protection, and flood riverine roads, restricting or halting the traffic. These events incur additional user costs owing to increased travel times from the rerouting and reduced speeds on affected roads. The economic impact of such events on road networks is typically quantified in terms of infrastructure recovery costs, while the expected user cost (EUC) of driving on damaged roads is often neglected. This study estimates flood risk to road networks by integrating a hydrological-hydraulic model with road and bridge vulnerability assessments and traffic assignment models to calculate the EUC. The procedure was applied to the Aconcagua River basin in central Chile, considering floods with return periods ranging from 2 to 100 years, bridges vulnerability to scour, road waterlogging, travel times, and fuel consumption costs. In the 100-year scenario, 7.65 km of roads and 3 bridges were affected. Considering all analysed return periods, the EUC of the network reached USD 5.7 × 10 ⁶  yr ⁻¹ . These results provide a quantitative basis for flood risk management and support decision-making regarding prioritization of road and bridge interventions in the Aconcagua River basin.