白良浜の海浜過程とその保全 (1)

Abstract

The objective of this paper is to study the beach processes of Shirarahaina and to proposethe most adequate beach erosion control work. Shirarahama beach is a white sandy beachsurrounded by rocky headlands so that it is very stable as a pocket beach. But, recenturbanization of the hinterland has reduced sediment supply to the beach. A little beach erosion, therefore has gradually occurred due to the imbalance between gains of sediment and losses byincoming waves and blown sands. This situation is very severe, because the total volume ofwhite sand in the beach is only approximately 10 5 m3. From the results of the field dataanalysis, of one dimensional analysis of beach change using long-term and short-term energyfluxes and of numerical simulation of nearshore currents, it is concluded that Shirarahaina beachis stable for most of the year, but the beach sediment may be carried away in the offshoredirection of Yuzaki headland in high wave conditions. The headland control work isproposed to control the beach erosion engaging beach nourishment.