This chapter explores the significance of intensity measures for flood hazards in assessing the fragility of bridges. Flood hazards pose considerable challenges to bridge infrastructure due to factors such as hydrodynamic forces, scouring, and debris accumulation. The study reviews various methodologies and models used to quantify flood intensity, including hydraulic simulations, empirical equations, and computational fluid dynamics. Despite advancements in modeling techniques, challenges persist, including uncertainties in hazard prediction and gaps between research and practical applications. Importantly, the chapter highlights the need to incorporate climate change considerations into hazard assessments and infrastructure design, given the projected increase in the intensity and frequency of extreme weather events. The absence of climate change in existing studies underscores a critical area for future research and intervention. By integrating advancements in modeling techniques and proactive adaptation strategies, this study’s outcome promotes sustainable infrastructure development and ensures the longevity of bridge structures in the face of evolving environmental conditions.