Long Term Change of Terrace Morphology and Longshore Sediment Transport around the Tenryu River Mouth

Abstract

This study investigates long-term change of terrace morphology and longshore sediment transport around the Tenryu River mouth based on bathymetry data of past 50 years. Based on the sediment budget around the terrace and the assumption of little sediment supply from the river in recent years, CERC formula was calibrated to estimate the longshore sediment transport rates at both east and west boundaries of the focusing area. Obtained boundary conditions then yielded distribution of the longshore sediment transport around the terrace and estimations of sediment supply from the river. These results and additional numerical analysis clearly showed increasing impacts of the detached breakwaters and indicated that the terrace morphology in 1984 may be required for dynamic equilibrium of the sediment budget around the river mouth.