Matrices, curves and indicators: A review of approaches to assess physical vulnerability to debris flows

Debris flows are natural processes that cause considerable economic loss and sometimes also casualties. The motion of the debris flow is influenced by both solid and fluid forces making it particularly destructive. Although a large amount of studies regarding the process itself is available in the literature, scientists repeatedly focused on the physical vulnerability of the elements at risk since this is often the key for the reduction of devastating consequences. In the present paper, different approaches for the assessment of physical vulnerability to debris flows are presented, discussed and highlighted through studies from the literature. Their advantages and particular challenges are outlined and studies following a similar approach (e.g. vulnerability curves, vulnerability indicators) are presented and compared. Finally, recommendations for the future are outlined including: (1) better damage documentation for improved datasets, (2) improvement, combination and expansion of existing methods (3) consideration of change for future risk scenarios (4) further research on the interaction between elements at risk and the hazard process including laboratory experiments and (5) consideration of the resilience of buildings in the physical vulnerability assessment.