BEACH CHANGES DUE TO HIGH-ANGLE WAVE INSTABILITY ALONG SOUTH COAST OF PANAI ISLAND IN THE PHILIPPINES

Abstract

 The Philippines has many islands and complicated embayed coastlines, so the wave incident angle to the direction normal to the shoreline may be significantly large, causing beach changes due to High-angle wave instability. Along such a coast, ordinary shore protection method using groins is not applicable for the conservation of the shoreline. The southern coast of Panai Island in the Philippines has such characteristics. In this study, beach changes of this island was investigated using satellite images together with field observations. Wave field was also calculated using the energy balance equation. It was found that waves are incident at an angle larger than 45° at several locations along the coastline, causing severe beach erosion douncoast of the protruded shorelines.