RELATIONSHIP BETWEEN DYNAMICS OF RIVER MOUTH SANDBAR AND RIVER DISCHARGE AND WAVE AT OMONO RIVER

Abstract

 River mouth sandbar grows in Omono River in Akita prefecture. River mouth sandbar topography was affected by combined forces, such as river discharge, ocean waves. River mouth sandbar interrupts salt and wave intrusion and affects the navigation of cruisers and fishing vessels. Therefore, study on sandbar on Omono River was carried out. However, field investigation was conducted more frequently to understand the change of sandbar in detail. In this study, field investigation using UAV was conducted. Then, sandbar change process was analyzed calculating sandbar area and river mouth width from reconstructed topography by the SfM technique. Furthermore, the investigation of relationship between sandbar area and river mouth width and river discharge, cross-shore, and longshore waves was carried out.

 As a result, the following results were found out from this study. The relationship between sandbar area and river mouth width and river discharge, cross-shore, and longshore waves were cleared. The seasonal cycle was discovered. Moreover, recovery of sandbar was cleared partly. It was found out that sandbar area was changed -500-+400 m² per day and river mouth width was changed -2-+2 m per day.