Copula-Based Probabilistic Approaches for Predicting Debris-Flow Runout Distances in the Wenchuan Earthquake Zone

Abstract

After the Wenchuan earthquake, frequent debris-flow disasters caused catastrophic damage to the infrastructures and inhabitants in the downstream. It is very important to properly determine the runout distances of debris flows to delineate potential hazard areas for the postearthquake mitigation work design and effective risk management. However, this is a difficult task due to the high variability and uncertainty of debris flows. This paper developed copula-based probabilistic approaches for predicting the runout distances of debris flows on depositional fans. The proposed approaches integrate the debris flow’s maximum runout distance (L), debris-flow volume (VD), and catchment internal relief (H) into a three-dimensional copula-based probabilistic model. A probabilistic model of debris flows in the Wenchuan earthquake zone was developed based on the field investigation data of 133 channelized debris-flow events. The developed model is able to predict the possible maximum runout distances for a specific hazard level. The proposed approaches were validated using an independent field investigation dataset of debris flows. Results show that the proposed approaches properly estimate the maximum runout distances of debris flows in the Wenchuan earthquake zone for a specific probability level of 0.88.