EFFECT OF TRAINING JETTY NECESSARY FOR DYNAMICALLY MAINTAINING A RIVERMOUTH BAR IN EQUILIBRIUM STATE

Abstract

 The effect of a training jetty to control sand deposition at the river mouth was investigated, taking the mouth of the Minato River that flows into Uraga Strait in Chiba Prefecture as a study area. Because the size of this river is small, sand deposition at the mouth due to waves is remarkable, whereas flusing of sand by floods often occurs, and the river mouth topography is in dynamically equilibrium state. The variation of the rivermouth bar was investigated using satellite images and field observation was carried out on 22 June 2022. Moreover, cross sections of the rivermouth bar were measured using a GPS-RTK along three transects across the rivermouth bar as well as the sampling of riverbed material. At this river mouth, when the shoreline of the rivermouth bar completely attached to the training jetty and the direction normal to the shoreline became equal to the wave incident angle, the sandbar became stable.