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

Abstract. Hydrometeorological events have a significant impact on road infrastructure and traffic flow. Floods can lead to the collapse or weakening of bridges, compromise river protection, and inundate riverine roads, thereby restricting or halting the traffic. These events incur additional user costs owing to the increased travel times resulting from the rerouting and reduced speeds on the affected roads. The economic impact of such natural events on road networks is typically quantified in terms of the infrastructure recovery costs. However, the expected road user cost (EUC) associated with driving on damaged roads is often neglected. This study aimed to estimate the 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 Bajo" Watershed in central Chile, considering floods with return periods ranging from 2 to 100 years, the vulnerability of bridges to scour, road waterlogging, travel times, and fuel consumption costs incurred by the road users.