Abstract: Debris flow is a common geological disaster in the mountainous area of west China leading to huge loss of people’s property and life and devastating ecology and geological environment. Evaluating the susceptibility of debris flow accurately is of crucial importance to disaster prevention and mitigation. In this paper, a cloud model of evaluating the susceptibility of debris flow is built based on the game theory. The susceptibility of debris flow is classified into four levels: not susceptible (level Ⅰ), lowly susceptible (level Ⅱ), moderately susceptible (level Ⅲ), and highly susceptible (level Ⅳ). Qualitative indices are determined as slope gradient of gullies (index X₁), longitudinal gradient of gully bed (index X₂), vegetation coverage (index X₃), solid material source storage per unit area (index X₄), catchment area (index X₅), and rainfall in wet season (index X₆). The criteria of rating these indices and the characteristic quantities of the corresponding cloud models are proposed. Moreover, the subjective weights and objective weights of the evaluation indices are calculated using hierarchy analytical method and entropy method respectively, and the combinatorial subjective and objective weights are given in the light of the game theory. The effectiveness of the proposed model is verified by five debris flow examples in the west Qinling Mountain area. The evaluation result is consistent with the actual situation in general. The model is further applied to evaluating the susceptibility of debris gully in Xi’an, and the result suggests that the debris flow is moderately susceptible (level Ⅲ).

Key words: debris flow hazard, susceptibility evaluation, cloud model, game theory, combinatorial weighting