The typical river-blocked case was studied. The features of the river-blocked by debris flow were proposed, such as total blocking, obstruct blocking, and local blocking.The local blocking is the most widespread type. One of the disaster modes caused by the local blocking is the river diversion due to the scouring of the opposite bank by the river flow with high velocity.The flow field of the main river with different block coefficients was analyzed by the numerical simulation method according to this disaster type.The order degree of the main river was studied based on information entropy principle. When the block coefficient R is in the range of 0.8 to 0.9,the entropy of the main river decreases rapidly, and the velocity of the water flow is fast.The block coefficient,R>0.80,was taken as the criterion of the local blocking of the river by the debris flow.The simulation was verified by the river-blocked event caused by the debris flow along Minjiang River between Yinxing to Yingxiu section, and the the results were in good agreement with the field data.
