In order to improve the utilization rate of the shoreline,we propose to arrange the excavated harbor basin due to the lack of shoreline resources in the middle and upper reaches of Qiantang mountainous rivers.In view of the problems of large discharge,fast velocity and poor navigation flow conditions at the entrance of the excavated harbor basin,we study its layout and navigation flow conditions by means of the physical model and ship model tests.The results show that the angle between the axis of the harbor basin and the flow direction should be as small as possible from the navigation aspect.Maximum back flow velocity for the safe navigation of ships into the harbor basin is about 0.4 m/s at the brake section of the harbor basin and 0.5 m/s at the entrance area.The transverse velocity at the entrance area should be less than 0.8 m/s.