The National Bridge Inventory (NBI) database indicates that approximately 500,000 out of 600,000 bridges in the United States (U.S.) are located over rivers and streams. As such, their foundations are constantly exposed to the erosive action of the flowing water. In addition, the projected change in the river hydrologic regime raises concerns about bridges stability failures with adverse consequences such as a traffic disruption and significant socio-economic loss. Statistical evaluation of bridge failure causes suggests that flood-induced foundation scour is the leading cause of failure in the U.S. and around the world. Moreover, as regionally distributed infrastructure systems, bridges are exposed to natural hazards such as earthquakes. Understanding how the presence of flood-induced scour affects the dynamic performance of bridge structures will lead to their resilient design. Furthermore, evidence on the climate change suggests that transportation infrastructure will be forced to operate in conditions out of their design range as flood events exceeding current 100- and 500-year design floods will become frequent. Recent disruptions in the transportation network due to flooding events highlight the importance of considering the increased likelihood of extreme flood events in design and hazard mitigation.

The objective of this dissertation is to assess the performance of highway bridges considering extreme flood-induced scour in the context of multi-hazard scenarios, then develop cost-effective adaptation strategies to mitigate the impact of climate change on bridges. To achieve these goals, a vulnerability assessment was conducted through a probabilistic-based approach by utilizing fragility functions. Furthermore, a framework is proposed to assist transportation decision-makers face with large uncertainties imposed by climate change. This framework is based on scenario planning and provides decision-makers with guidelines for economic analysis of the impact of climate change on bridges.