In order to advance debris flow loss assessment from macroeconomic evaluation to service for civil engineering

the concept of engineering vulnerability based on structural devastation extent of civil engineering infrastructures is put forward. However

for those engineering harmed by debris flow hazards

such as bridges and tunnels

it is insufficient to determine the actual disaster loss merely according to structural devastation extent. When the engineering function is completely lost but structure slightly damaged

its vulnerability can be underestimated. Besides

when the engineering function is fairly workable but structure severely damaged

its vulnerability can be overestimated. Therefore

on the basis of the conventional assessment of structural devastation extent

the influencing factors for bridges and tunnels’ function is introduced

such as hazard-affected characteristics

railway/highway ranking and restoration cost. Thus

the engineering vulnerability assessment method for bridges and tunnels harmed by debris flow hazards is proposed

considering both structural devastation and function loss. In the case study

the assessing results show that the insufficiency of the conventional structural assessment can be overcome by this method. This method extends and develops the concept of engineering vulnerability

which makes the assessment more comprehensive and credible. Hence

it is concluded that this method is of great significance to correctly predict and verify the disaster situation of bridges and tunnels harmed by debris flow hazard

to properly prepare the emergency plans or to initiate a quick response.