A Framework for Hazard Assessment of Debrisflow Accumulation Areas

Abstract

An increasing demand for assessing the hazard of debris-flow accumulation areas is critical to risk management and policy implication for debris-flow hazard mitigation. In this paper, a framework for hazard assessment in debris flow-prone areas is proposed. Based on the hazard definition, debris-flow hazard is computed by its occurrence probability and disruptive intensity. Debris-flow occurrence probability is defined as a joint probability considering both hydrological and debris supply condition. Debris-flow disruptive intensity is introduced to express the inundated and impact damage of debris flow by the distribution of flow depth and velocity. The distribution is based on an extended geometric model of debris-flow fans, including the maximum length, width, and thickness (or flow depth) of debris-flow fans, and the channel outlet width. A hazard matrix, correlated to debris-flow occurrence probability and disruptive intensity, is used to map the hazard on debris-flow accumulation areas. The proposed procedure is applied to assess the debris-flow hazard on the accumulation area of Shuida gully, located in the Longchi town, Sichuan province of China. Finally, the article considers the effects of hazard maps.