Analysis of Offshore Bathymetric Changes Using GPS and Fishfinder Data

Abstract

Bathymetric data in a wide coastal area were derived from frequent monitoring using fishfinder and GPS data logged during fishing operation in Enshu-nada Sea. The offshore bathymetric changes in near critical depth were evaluated by the annual changes of contour line positions along the cross-shore direction and these standard deviations. The analysis revealed long-term trend with short-term fluctuation in the sea bottom changes associate with the frequent monitoring data. We found that slow erosion appeared in the offshore area except around river mouth and inlet was indicated.