Multidecadal Shoreline Evolution Due to Large-scale Beach Nourishment in Japan

A large-scale beach nourishment in the Netherlands, the Sand Engine, is getting attention as a new type of nourishment. As a similar case in Japan, here, we investigated morphological changes from 1961 to 2013 on the Hasaki coast, where approximately 50 million cubic meters of sands were dumped into the nearshore zone. The Hasaki coast, which is located in the eastern Japan facing the Pacific Ocean, has 16 km long sandy beach. From 1965 to 1977, approximately 50 million cubic meters of sediments were dumped into the nearshore zone on the north side of the beach for disposal of the earth and sand generated during the construction of the Kashima Port, which is an artificially-excavated port. A part of the shoreline-advanced area due to the dump was reclaimed for a land space. Therefore, in practice, approximately 26 million cubic meters of them was the volume of the sediment supply contributed to the morphological change. The volume is comparable to the nourishment of the Sand Engine, of which the volume is 21.5 million cubic meters. An increase in the sediment budgets due to the dump resulted in the mean shoreline advance of approximately 40 meters from 1969 to 1984. After that, although the advance was abated from 1984 to 1993, the shoreline began to advance again from 1993. As the result, the mean shoreline position in 2013 was located approximately 70 meters seaward compared to the position in 1961.