静岡県馬込川河口域における非対称な流況場と堆砂特性

Abstract

This paper investigates asymmetric current fields and resulting sedimentation characteristics observed around the Magome River mouth. Field survey was first conducted to obtain detailed bathymetry of the river mouth and to capture spatial current patterns by tracing wooden chips floated on the water surface. Image rectification technique was utilized to track the actual coordinates of wooden tracers. Time-varying water level and flow velocity near the bottom were also measured and, not only yielded time-varying tidal characteristics, did these data support the validity of estimated current patterns using wooden tracers. Circulation current patterns induced by broken waves were clearly observed in the area where the distance between two jetties was widened and local sedimentation was observed in the landward edge of this circulation current. This circulation current also caused asymmetric distributions of tidal current velocity across the narrow river mouth. Numerical analysis was finally conducted to investigate the influence of observed asymmetric current on the sand discharge rate at the river mouth.