Abstract: For the composite riverbank, the continuous erosion of the lower non-cohesive layer results in the failure of upper cohesive layer. The cohesive soil block deposits at bank toe, which can alter the flow structure and the following erosion process in the bend. To reveal the effect of failed soil block, a three-dimensional numerical model was developed to simulate the flow structure and wall shear stress pattern in the Shishou bend with different failed block. The results indicate that soil block deposit at bank toe shifts the dynamic axis of flow away from the outer bank, decreases the intensity of the secondary flow, and changes the direction of the secondary flow. The effect of failed block on the wall shear stress changes greatly with space. For the riverbed and inner bank, the average wall shear stress tends to increase, while decreases in the head and upstream area of the failed block for the outer bank. The larger the failed block is, the greater the variation of wall shear stress will be. In comparison, The variation of wall shear stress is about 2%—10% of the variation of cross-sectional area of the failed block. The results are expected to provide a basic theoretical and technical support for river regulation and riverbank planning.