Abstract: The height of debris flow barrier dam directly determines the reservoir capacity and outburst flood flow, which is a key factor affecting the disaster-stricken degrees of both upstream and downstream areas.Main parameters influencing debris flow blocking river are grouped into four dimensionless factors(the volume concentration factor, the volume factor, the clay-content factor, and the flow velocity ratio).Through indoor flume experiments, complete blocking forms of high density debris flows and height characteristics of barrier dams under the influence of these dimensionless factors are studied.And then a predictive model for gully height and river blockage height of debris flow dams under right-angle confluence conditions is established.The results show that:(1) According to the product of two dimensionless factors, namely the main-tributary flow ratio(Q) and the flow velocity ratio(U),the complete-blockage modes of debris flows can be further classified into two forms, the "opposite-bank top rushing" type(Q×U≤0.045) and the "continuous advancing" type(Q×U>0.045).(2) The analysis of the height of debris flow barrier shows that the height of debris flow gully is proportional to both the volume concentration factor and the volume factor, and is inversely proportional to the flow velocity ratio.The height of debris flow blocking river is proportional to the volume factor, and is inversely proportional to the volume concentration factor and the flow velocity ratio.Under the influence of the clay content factor, the height of debris flow gully and the height of blocking river show a trend of increasing first and then decreasing.(3) The predictive model demonstrates good prediction accuracy and is validated through comparison with real-world case studies.The results show that the predictive model is applicable.The research findings can provide valuable reference for disaster prevention and mitigation measures related to debris flow river blockage.