For preventing bank erosion due to ship waves, many stream-wise groins have been installed in the downstream region of Arakawa River, Japan. However, the bank erosion still occurs at some locations even though similar-type groins are installed. In this study, field investigation at three locations on Arakawa River and numerical simulation were conducted. At each field investigation site, wave height, particle distribution of bed material and amount of sediment movement due to ship waves were measured. Amount of sediment volume increased with decreasing cross slope. As for numerical simulation on the flow around groins, total energy flux of ship waves by a ship was decreased due to installation of groins. The observed amount of bank erosion also decreased according to the decrement of the total energy flux. In addition, the amount of bank erosion increased with decreasing cross slope. These results indicate that the location with mild slope and steep slope has tendency to be accumulated or eroded, respectively, even after the groins were installed
