AbstractBarges offer a safe and cost-effective means for transporting commodities in inland waterway systems. This, however, comes with the risk of barge collision into bridge piers that span navigable waterways. While the vulnerability of such bridges has been investigated in an intact condition under vessel collision, the existing assessment methods fail to capture how scour events that bridge piers often experience during their service life can affect their response to vessel-induced impact loads. To address this gap, three bridge structures were modeled in this study, and a fully loaded barge traveling at 0.5, 1.0, 1.5, 2.0, and 2.5 m/s was allowed to collide into each of them after they underwent various scour scenarios. The scour scenarios under consideration were developed, following the procedure provided in Hydraulic Engineering Circular No. 18, for both 100- and 500-year floods. Based on the obtained results, the impact force, maximum shear, and maximum bending moment that the bridge piers experienced were found to decrease as the scour depth increased, mainly because the bridge piers gained flexibility. On the other hand, the maximum force that the bridge ends witnessed were determined to increase, indicating that the bridge structure can become vulnerable to failure at locations other than bridge piers as the scour depth increases. With an in-depth understanding of the magnitudes and trends of key structural response measures, the outcome of this study provided a rigorous multihazard perspective to improve the safety and performance of bridges built on navigable waterways.