Abstract: When a composite bank fails,slump blocks deposit at the toe of the bank. This alters the flow structure near the bank and affects the bank erosion processes. To investigate the effects of slump block at different locations on the flow structure near the outer bank,a generalized model of Shishou reach was conducted. Acoustic Doppler Velocimeters (ADV) was used to precisely measure the three-dimensional flow velocities. Experimental results show that the slump block upstream of the head-on scouring point shifts the region of maximum streamwise velocity away from the outer bank and reduces the averaged bed shear stress between the slump block and the bank toe. In contrast,the slump block downstream of the head-on scouring point makes the region of maximum streamwise velocity closer to the outer bank and increases the averaged bed shear stress between the slump block and the bank toe. This study enriches the understanding of composite bank erosion process,and helps to develop and improve the erosion model of composite bank.