风险一词虽然已经广泛被科学家和经济学家所使用，但涉及到自然灾害的风险研究则还是20世纪80年代中后期的事，国内有关泥石流风险的探讨，更是20世纪90年代才初见端倪。国际上，泥石流风险评价至今仍然是前沿探索性领域和新兴的研究课题，基于联合国对自然灾害风险的定义及其定是表达，本文给出了泥石流“风险度＝危险度×易损度”这一数学命题的近似解，讨论了风险分级和不同风险等级的分布概率以及风险指南，以云南东川因民矿区黑山沟泥石流为例，对单沟泥石流风险度评价模型进行了示范应用。

Adopting the definition suggested by the United Nations, debris flow risk is used to measure the expected loss (losses of lives, person injured, property damage, and economic activity disrupted) due debris flows for a specified area and during a reference period. Under the mathematical proposition of "Risk is the product of hazard and vulnerability" given by the United Nations, the present paper has obtained an approximate quantitative solution for emprirically assessing debris flow risk. Site-specific debris flow risk assessment model is a multiple factor composite assessment model including seven indexes, so site-specific debris flow risk assessment model is practically a synthetic model comprising of 14 variables. This paper has also discussed the classes of debris flow risk and their probability distribution. Among the five classes, from the statistical viewpoint, the very low risk class occurs with a probability of 16.88%; the low risk class occurs with a probability of 28.44%; the moderate risk class occurs with a probability of 27.46%; the high risk class occurs with a probability of 19.78%; the very high risk class occurs with a probability of 7.44%. A case study in Heishan gully of Yinmin copper mine of Dongchuan in Yunnan province has been used to demonstrate the procedures of the method for site-specific debris flow risk assessment.