Assessment of debris flow risk according to damage type

Abstract The spatial distribution of hazard risk due to debris flows is discussed using a horizontal two-dimensional numerical simulation of debris flow, and the hazards are evaluated according to the type of damage. Compared to the hazard areas between the flow depth of the debris flow and the building destruction, many of the areas inundated by debris flows are outside the hazardous area for building destruction. Compared to the hazard areas between the building destruction and the sediment deposition, there is almost no overlap between the two areas. In other words, the area away from the stream exit does not suffer from severe damage such as the destruction of buildings, but it is not completely free from damage due to the accumulation of sediment on the site and the inflow of sediment into the houses. It is important to evaluate the hazard level for various types of damage when considering the hard and soft countermeasures against debris flow damage.