富山県宮崎海岸の海浜過程について

Abstract

The objective of this paper is to make clear the beach processes of Miyazaki beach, facing the Japan Sea. Recently, the recession of shoreline has remarkably occurred nearthe mouth of the Sakai river to Ichiburi Fishery Harbour, and it has a tendencyadvancing westward. This is mainly due to the construction of the eastern breakwater ofthe harbour, acting as a barrier to longshore sediment transport. The processes of beacherosion at Miyazaki beach were found to be similar to those at Shimoniigawa coast fromthe view point of the geographical and oceanographical situations. Both the beaches aredowncoasts from the view point of longshore sediment transport. From investigationswith depth sounding charts and aerial photographs, sediment statistics and composition ofspecial minerals, it is found that the dominant direction of longshore sediment transport iswestward. This fact is also confirmed by the characteristics of longshore wave energyflux. Therefore, the beach procesess are governed by the so-called Yorimawari-nami, huge swells coming from the E to NE directions. It is found that the beach processesare predictable by the analysis of the rate of shoreline changes and a one-dimensionalanalysis of beach change prediction in which changes of the rate of sediment supplyupcoast is taken into account.