The Bottom Surface Sediment Transport Changes in Bathymetry in the Rupat Strait, Riau Province, Indonesia

The Rupat Strait is located at the eastern coast of Sumatera Island, Riau Province,Indonesia, under the influence of the current system flowing from the Malacca Strait into the Strait.The primary purpose of this study is to identify the topographyof Rupat Strait prevailed by bathymetry changes, which was analyzed using oceanographic and satellite images.This study was conducted in the Rupat Strait in July 2018 through two steps of research: 1) oceanographic observation; 2) bathymetry measurement.The study of oceanographic observation was carried out along the coastal areas of Dumai City and Rupat Island. The depth of Rupat Strait (bathymetry) was measured using an echosounder at 60 stations in July 2018. The changes in the depth of the Strait were analyzed by comparing data between depth in 1990 by satellite images and the depth in 2018 by the measurement. The results of study indicate that dominantly, the depth of the Strait has increased by 1.5-2.7 meters for 28 years. The depth of the Rupat Strait, based on the interpretation of the satellite image data of MIKE C-MAP (1990) ranges from 0.9 to 29.4 meters, and of the measurement in 2018, ranging from 2.4 to 32.1 meters.The dominant factor causing the changes are the current system flowing from the Malacca Strait through the Strait during high and low tides, and the surface bottom sediments are transported out the Strait by the current, including the bottom current.