A systematic approach for the assessment of flooding hazard and risk associated with a landslide dam

Inundation caused by landslide dams may occur in the upstream and downstream of the dams. A proper flooding hazard assessment is required for reaction planning and decision-making to mitigate possible flooding hazards caused by landslide dams. Both quick and detailed procedures can be used to evaluate inundation hazards, depending on the available time and information. This paper presents a systematic approach for the assessment of inundation hazards and risks caused by landslide dam formation and breaches. The approach includes the evaluation of dam-breach probability, assessment of upstream inundation hazard, assessment of downstream inundation hazard, and the classification of flooding risk. The proposed assessment of upstream inundation estimates the potential region of inundation and predicts the overtopping time. The risk level of downstream flooding is evaluated using a joint consideration of the breach probability of a landslide dam and the level of flooding hazard, which is classified using a flooding hazard index that indicates the risk of potential inundation. This paper proposes both quick and detailed procedures for the assessments of inundation in both the upstream and downstream of a landslide dam. An example of a landslide dam case study in southern Taiwan was used to demonstrate the applicability of the systematic approach.