Based on the analysis of many international documented cases as well as on the study of Brazilian debris flows, a description is made on the main factors that intervene in the deflagration of this type of mass movement. These factors are basically the rainfall intensity, declivity of the slopes, geological conditions and availability of material to be removed and carried by the moving mass. A graph of the rainfalls in terms of accumulated precipitation and time is presented, for cases of diverse intensities, and a critical line above which mass movements occur is proposed, distinguishing zones of increased severity. The paper also compares several events in terms of height to length ratios and volume of sediments, as well as initiation slope angles related to hydraulic basin area of debris flows. Based on the analysis of the studied cases, the relative importance of the intervening factors and their weights was established, leading to a methodology to assess the susceptibility of an area with respect to debris flow occurrence.
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