Abstract
Causes of increase in artificial coastline associated with the extension of harbor breakwater were studied through the case study of Ohtsu Fishery Habor and Oharai Port both located in Ibaraki Prefecture. Circurating currents with longshore sediment transport toward the lee side of the harbor breakwater were induced after the extension of the breakwater in these areas. Measures were taken after the severe beach erosion to reduce their effect and the natural sandy coastline were transformed into the artificial one. To improve this condition, it is neccesary for related organaizations responsible for coastal protection works to take measures cooperatively.
