EVALUATION OF BEACH NOURISHMENT ON MIYAZAKI COAST

Miyazaki Coast locates between the Hitotsuse River mouth and the northern side of Miyazaki Port. This beach has been suffering from severe beach erosion due to the shortage of sediment supply from rivers and the change of waves and nearshore currents by the construction of an offshore breakwater at Miyazaki Port. In order to preserve the sandy beach, a beach nourishment project has been implemented since 2008 in combination with the installation of Sand-Packed containers that were placed in front of the dune. A certain volume of nourishment sand has been installed for the sand fill work that covers Sand-Packed containers, and the rest has been dumped off the coast. The purpose of this research is to evaluate the effectiveness of the beach nourishment with using long-term bottom sounding data. This study discussed the effect of the beach nourishment on longshore sandbar evolution. The change of the sand volume in research area was also discussed in this study. Furthermore, the method of Empirical Orthogonal Functions, EOF, was applied to some cross sections in order to describe the spatial and temporal variability of longshore sandbars.