Abstract: The flash flood disasters of mountain torrent,landslide and debris flow are common in mountainous areas of China.Though the developmental background of the three types of disasters are similar to some extent,the concrete impact factors of them are different.Previous studies paid great attentions on effects of specific factors on these disasters,but the quantitative relationships of different impact factors to the three types of disasters in comprehensive analysis remain unclear.As a result,the weights of impact factors were hard to design impersonally in risk or hazard assessment of corresponding disasters.Accordingly,taking the Sichuan province as an example,a conceptual model was constructed to evaluate the impacts of basic factors,e.g.,rainfall,landforms and population-property vulnerability,and general factors on different types of flash flood disasters based on making clear the distributed pattern of disasters of mountain torrents and corresponding landsides and debris flows.The results show that:1) the flash flood disasters in Sichuan Province mainly distributed in the mountainous and plateau areas around the Sichuan basin and part of the Hengduan mountainous area,in which the mountain torrent disasters mainly developed in the northeastern and southern mountainous areas around the Sichuan basin;landslide disasters located mostly in the western and southwest mountainous areas around the Sichuan basin;and the debris flow disasters mainly distributed in the western and southwest mountainous and plateau areas around the Sichuan basin and part of the Hengduan mountainous area.2) If 100% variation of flash flood disasters on distribution was assumed to be decided by the rainfall,landforms and population-property vulnerability,the impact degrees of the three basic factors to the different types of disasters are:for the mountain torrent disasters,59%,28%,13%;for the landslide disasters,48%,34%,18%;for the debris flow disasters,15%,73%,12%.The factors of rainfall and landforms both play the most important roles in developing and distribution of the local flash flood disasters.3) Besides the three basic factors,the soil is the most important factors to the development of disasters of mountain torrent and landside,and the factor of lithology is critical to the distribution of debris flow disasters.Generally,the underlying surface condition plays a more important role on the distribution of debris flow disasters,while the rainfall condition is more critical to the disasters of mountain torrent and landslide.

Key words: flash flood disasters, weights of impact factors, risk assessment of natural disasters, spatial analysis, the Sichuan Province