Loose masses caused by geologic hazards like landslides, collapse and debris flow block the valleys or rivers, and they will form natural dams with the source space location changes, as time goes by, natural dams will collapse under some conditions, forming a new type of debris flow- outburst debris flow. This kind of debris flow could cause catastrophic disasters in a short period of time, which has strong destructive power. Although there are a lot of reports about outburst debris flow, few scholars have done researches on this kind of debris flow.

An accurate warning of outburst debris flows is a worldwide problem and one of the hot topics in the academic community of landslide and debris flow in the world. Recently, the research team of CUI Peng from Institute of Mountain Hazards and Environment,CAS has made remarkable achievements and social benefits around the formation mechanism of the outburst debris flow. The research team systematically summarized the historical data of natural dam and carried out a series of model test, and obtained the data of formation process and debris flow kinematics and dynamics of natural dam. Based on the theory of stream power in sediment transport mechanics, the relationship between channel bed slope, unit weight of debris flow and peak discharge was established, and they obtained the critical condition of outburst debris flow. This critical condition is clear in physical conception and easy to obtain the parameters and it’s convenient to rapidly determine the formation of outburst debris flow.  



Figure 1. The critical conditions of the formation of debris flow


Figure 2. Experimental setup


Figure 3. The forming process of outburst debris flow

 Figure 4. The case of applying critical condition to judge the formation of outburst debris flow