Bathymetric Changes Related to Wave and Flood in the Tenryu River Delta-front, Japan

摘要

This study presents bathymetric changes and its characteristics due tohigh waves and fluvial floods are examined for wave-dominated deltafrontof Tenryu river, a sediment-rich river on the Pacific coast (Enshunada)of central Japan. Frequent continuous bathymetries around theriver mouth are obtained from records of coastal fishing activity ofsmall vessels. Dominant feature of 4-year bathymetric trend areexhibited by concentrated erosion (approximately 3 m vertically) withinthe delta-front terminal and the lobe migration. Wave-inducedretrogradation and flood-induced progradation of the delta-front duringshort-term meteorological event are examined by transect analysis ofthe terminal lobe. A tentative estimate, cross-shore variations of thelobe are explained in terms of offshore wave energy and the river flooddischarge. Flexible terrain analysis of the river delta bathymetry by useof the data and the bathymetric changes of different time periods areshown in this paper.