LONG-TERM SHORELINE CHANGES DURING HALF CENTURY SINCE 1964 ALONG COASTS BETWEEN HITACHI PORT AND ISOZAKI FISHING PORT

Abstract

 Shoreline changes associated with the extension of offshore breakwaters during half century since 1964 were investigated, taking the coasts of a 12.5 km stretch between Hitachi Port and Isozaki fishing port facing the Pacific Ocean as the examples. On the Naka coast in the northern part of the study area, shoreline changes were triggered by the wave-diffraction effect of the offshore breakwater of Hitachi and Hitachinaka Ports. The coastline of the eroded area has been completely covered with a seawall and concrete blocks until present. At Ajigaura Beach in the south part of the study area, clockwise shoreline rotation took place owing to the extension of the offshore breakwater of Hitachinaka Port. Future measures to preserve sandy beach was proposed on the basis of field data.