A fuzzy comprehensive method for the risk assessment of a landslide-dammed lake

A landslide-dammed lake is a common geological disaster in mountainous areas that is usually triggered by heavy rainfall or a strong earthquake, posing a great threat to the population and property downstream. As quantitative data and decision-making time are usually limited in many landslide dam cases, to mitigate damage, a rapid assessment of the risk of a landslide-dammed lake is required for a successful emergency dam treatment. Based on easily available data from historic landslide dams of the Wenchun earthquake, a fuzzy comprehensive method is proposed to assess the danger of a landslide dam, the vulnerability resulting from an outburst flood and the risk associated with a landslide-dammed lake. Dam materials, dam height, maximum storage capacity, and ratio between dam length and width were four main factors used for danger assessment; four social factors (including population, administrative region, facilities, and art relics and rare species) and four environmental factors (river, wildlife habitat, human landscape and pollution enterprise) were used for vulnerability assessment. Both assessments were implemented via a first level fuzzy comprehensive evaluation. Meanwhile, the risk level of a landslide-dammed lake included the combined effects of danger and vulnerability, and the risk level was classified based on levels of danger and vulnerability by a second-level fuzzy comprehensive evaluation. Finally, this proposed fuzzy comprehensive method was successfully applied to a recent landslide dam that occurred on June 24, 2017, in Maoxian County, its danger, vulnerability and risk were rated at level IV. Accordingly, the method is supposed to be feasible and applicable for comprehensive assessment of landslide-dammed lakes, contributing to making effective measures for timely disaster mitigation.