Past, present and future morphological development of a tsunami-affected coast: a case study of Banda Aceh

This thesis investigated a thorough geomorphology of Banda Aceh, a coast on the north tip of Sumatra Island, Indonesia which was severely affected by the earthquake and tsunami occurred on 26 December 2004. The response and development of the Banda Aceh coast before and after the tsunami was thus not well-understood. The main objective was to increase the understanding of the future development of a coastal system that is prone to the large-scale natural interventions of tectonic land subsidence and tsunami. Explorative methodologies were used and the time-scale-related issues were emerged on the coastal morphological processes. The research flow was driven by a wide span of geomorphological interpretation, field observations, spatial data analysis from satellite images, topographic and bathymetric maps, analysis of forcing factors magnitudes and frequencies as well as sediment budget analysis of the littoral transport. Banda Aceh coast is a sand-poor environment contains only a thin layer of loose sand on top of a consolidated Holocene prograding delta. The earthquake and tsunami of 26 December 2004 have affected the morphological units that have been established in the Holocene period which responses were different under different geomorphic settings. This research suggests that the damage caused by the probable recurrence of tsunami and land subsidence events to the coastal morphology within a century can be an order of magnitude greater than the effect of the well-known sea-level rise due to global climate change, which is often considered important in modern coastal management practices. In a time scale of a century, tsunami and land subsidence events due to tectonic activities are not unprecedented. More frequent but smaller magnitude tsunami and subsidence may occur; i.e. once every 20 to 30 years. Management of such coastal area in future should consider such magnitudes of intermittent forcing factors in the coastal morphological development analysis.