A Study on Hydrodynamic Characteristics and Resulting Morphological Formation of Sand Spit around the Tenryu River Mouth based on Image Analysis

This study aimed to investigate hydrodynamics and morphology around river mouth. The propagation of long period waves along the river side of sand spit around the Tenryu River mouth was analyzed by means of image analysis. A series of field surveys were conducted using video cameras to observe shoreline morphology on the river side of the sand spit. Characteristics of the swash motion were extracted and used to describe the fluid motion on the river side. On the basis of image analysis, it was concluded that the shoreline undulation was developed by sediment transport affected by edge wave. This was suggested by shoreline undulation properties found in the images and was confirmed by the edge wave wavelength calculated based on frequency of the corresponding swash motion. In addition, longshore transport instability due to oblique wave with large angle appeared to change the shape of the shoreline undulation.