The destruction of structures in debris flow events is most related to inundation height and the velocity of debris flow. However, previous studies had established structure vulnerability curves mostly based on inundation height. This study aims to find the relationship between vulnerability and impact forces (velocity and height). When a structure is struck by debris flow, the impact force is transformed to the displacement of the structure. In this study the dynamic impact force of debris flow needed to generate the displacement was based on the study of Haugen and Kaynia (2008). The fragility curve of a brick structure to spectral displacement was based on HAZUS (2003) damage state probability studies. After establishing the fragility curves under different damage state probabilities, we combined the fragility curves into a unitary curve for different velocities (2 to 20 m/s).
Key Words: Debris flow, vulnerability, impact force.