BEACH EROSION OF ARAHA BEACH IN CHATAN TOWN IN OKINAWA

Abstract

 In Chatan Town in Okinawa, an artificial beach of 630 m length bounded by groins on both sides was constructed along with beach nourishment. After the beach nourishment, marked shoreline changes were triggered by obliquely incident waves. Immediately offshore of this artificial beach a deep channel was remained in the south-north direction owing to the past dredging of the reef bed, but a shallow reef flat was remained offshore of the northern part of the artificial beach. Because of the wave-sheltering effect of this shoal, northward longshore sand transport was induced, resulting in the shoreline recession in the south part and accretion in the north part. To investigate these beach changes, bathymetric survey was carried out, and the mechanism of beach changes were analyzed. Two stabilization methods were shown.