MORPHOLOGICAL CHANGES OF THE RIVER MOUTH SAND BAR AT THE KUMANO RIVER

Abstract

 The river mouth sand bar in the Kumano River, which is located in the heavy rainfall and typhoon hit areas, causes the discharge capacity to decrease and the water level to rise. Therefore, it is important to establish an effective and efficient management method. In this study, in order to understanding the morphology changes and factors of the sandbar, the topography surveys using UAV and RTK-GPS for the sandbar and the sea bottom surveys around the river mouth were carried out. In addition, a numerical analysis of wave, flow, and topographical changes associated with the sandbar recovery process was performed. From the survey results, we clarified the seasonal morphology changes, the characteristics on the left and right sandbar, and the influence of the wave direction. Furthermore, we clarified the sediment transport around the sandbar from the terrace including the adjacent sandy shore during high waves. Finally, the BG model was developed, and examined its applicability to the erosion of the terrace, the sedimentation around the sandbar, and the drifting sediment transport for each wave direction.