Evaluation of the benefits of facility for disaster mitigation based on the risk of debris flow

Numerous collapses and landslides caused by the Wenchuan earthquake provide abundant loose materials for a large number of debris flows that occurred after the earthquake. Most of the check dams were silted or damaged by debris flow due to the increased volume of materials after the earthquake. Taking the debris flows in the Qinglin Basin in China as a case study, 43 sets of numerical simulations of debris flow with different probabilities of occurrence and different facility combinations were performed to obtain the submerged range, velocity, and mud depth of debris flow in the residential area. The total risk of the residential area is calculated on the basis of the risk of a single building according to the vulnerability of the property and population and combined with the depth and velocity of debris flow. According to the change in risk in the residential area under different facility combinations, a novel method of quantitative evaluation of the benefits of facilities for disaster mitigation based on risk reduction per unit height of facility (RRPH) has been proposed. According to the result of the analysis, the method can quantify the benefits of disaster reduction by different facilities, analyze whether existing facilities meet disaster mitigation goals, and determine the optimal facility height, facility combination, or existing facilities improvement and optimization scheme.