Study of Coastal Morphology Changes Due to Tsunami in the Sunda Megathrust—A Case Study at Pelabuhan Ratu Bay

Pelabuhan Ratu Bay is located in an area facing the Sunda Megathrust which has the potential for a Tsunami to occur. The danger from the Tsunami is not only in the form of run-up and inundation but also the danger of changing the morphology of the area. This study aims to investigate the morphological changes of the area in the form of changes in erosion and sedimentation due to the Tsunami generated by the earthquake in the Sunda Megathrust with various seismicity scenarios and sediment grain size without being influenced by other external effects such as tides and wind. This study was performed using two modelling tools, namely COMCOT for modelling Tsunami propagation and Delft3D for modelling the sediment transport. The result in instantaneous water level of the tsunami, wave propagation, and morphological changes is discussed. The geometry and slopes of Pelabuhan Ratu Bay allow the wave to experience a shoaling which escalates the wave height to at least tripled compared to the offshore value. The incoming waves induced sedimentation at the offshore region and mixed erosion and sedimentation at the nearshore region. Findings in each scenario are compared, and the impact of seismicity and sediment size is evaluated.