INVESTIGATION ON THE RELATIONSHIP BETWEEN CHANGE OF THE RIVER MOUTH SANDBAR AND RIVER DISCHARGE AND OCEAN WAVE ENERGY AT OMONO RIVER

A lot of sand was deposited at river mouth of the gentle flow river and the sandbar was formed.The river mouth sandbar topography was affected by combined forces, such as river discharge, sea waves, and wave direction, etc. River mouth sandbar interrupts salt and wave intrusion and affects the navigation of cruisers and fishing vessels.A field investigation was carried out for change of a river mouth sandbar in Omono River which was located in Akita Prefecture in Japan.The topographic surveys using UAV were conducted.Then, analysis of the sandbar change process was conducted on how sandbar area and river mouth width were calculated from reconstructed topography by the SfM technique.Moreover, an investigation of a relationship between sandbar area and river mouth width and river discharge, cross-shore, and longshore direction waves was carried out.As a result, the following results were confirmed from this study.(1) Right side sandbar has the sand spit which faced the south or left side sandbar was developed very much in winter.(2) Sandbar area and river mouth width have a positive interrelation between river discharge and cross-shore waves.(3) Sandbar area has a strong negative interrelation between river mouth width.