At a low crown caisson seawall with a large-size wave overtopping drainage, overtopping water lump collides with a wall of drainage and the resultant return flow falls down to blocks in front of seawall. This falling water can pick blocks up, however, the velocity measurement around the blocks is difficult in a hydraulic experiment. In this study, using the MPS method, which is suitable to analyse wave overtopping process in a complicated setup of seawall, the velocity field was calculated and compared with the critical velocity of blocks based on CERC formula. The pick-up condition of blocks predicted by the MPS method with CERC formula showed good agreement with ones in a hydraulic experiment.
