The Geomorphological Dynamic of the Rupat Strait on the East Coast of Central Sumatera Island, Indonesia

Abstract

The Rupat Strait on the eastern coast of Sumatera Island is currently undergoing a geomorphological process due to the current system, which flows from the Malacca Strait, and the change of use of the hinterland. The main purpose of this study is to identify the geomorphological dynamic by analyzing the changes to the width and depth of the strait. We propose a remote sensing method using satellite imagery to evaluate the changes to the width and depth. The depth was also measured using echo sounding at 60 stations. The studies of oceanographic observation and sedimentation were carried out along the coastal area of Dumai City and Rupat Island at five stations on each coast. The results showed that although the width of the strait had increased from 6.91 km in 1997 to 7.63 km in 2017, the strait length had not changed over this period. Therefore, the area of the strait increased to 82.544 km² in 20 years from 463.687 km² in 1997 to 544.231 km² in 2017. Over 28 years, the depth of the strait has increased by 1.5–2.7 meters. The changes are due to abrasion and sedimentation, which caused accretion on the coasts of Dumai City and Rupat Island, which go around the Rupat Strait. The abrasion is occupied by a strong current velocity, high-wave energy, steep bottom topography, and coarse-grained sediments, and it was reversed at the accretion areas. The results of this study can be used to guide stakeholders on the utilization and management of shallow marine waters.