Beach Profile (Oceanography Factors) of Labuhan Bilik Island, Aruah Island, Rokan Hilir District, Indonesia

Abstract

Labuhan Bilik island is one visible image of the coastal condition of Aruah Archipelago (also called Jemur Island, the outermost island of Indonesia where located in Rokan Hilir district). Since this area is traversed by currents of Malaca Strait, some materials are moved and drifted down by the undercurrent. The aims of the research are to measure speed and direction of the current, determine the type of tide, describe the pattern of tidal current and shape of the beach profile. The research was held using survey method on several sample points which determined through purposive sampling. Formzahl values in the Labuhan Bilik island is 0.18065. The current type is Semi-Diurnal Tides (F<0.25) either low tide or high tide occur twice a day. The speed of current was varied which range between 0.061-0,098 m/s on high tide and 0.057-0.105 m/s on low tide. On low tide, currently comes from Labuan Bilik's Nothern flows to South and opposite direction on high tide. Based on coastal slope percentage Labuan Bilik island has 3 types of coastal profile: 1). slope: sloping percentage >2-8%, 2). oblique: sloping percentage >8-30% and 3). Precipitous: sloping percentage >30-50%. Based on beach material composition Labuan Bilik beach is classified into two: sandy beach which composed dominantly by sand and rocky beach which composed dominantly by the rock.