Short-term morphological responses and developments of Banda Aceh coast, Sumatra Island, Indonesia after the tsunami on 26 December 2004

The destructive earthquake and tsunami waves have caused sudden and immense changes in the morphology of the low-lying coast of Banda Aceh, Sumatra Island, Indonesia on 26 December 2004. Data from different sources and different instants in time used in this study to investigate the morphological responses and developments of two coasts that were affected by the tsunami near Banda Aceh; i.e. Ulee Lheue on the northwest coast and Lampu Uk on the west coast. The objective was to quantify the morphological changes of the two coasts that were affected by the tsunami and tectonic land subsidence, and their subsequent short-term developments. Interestingly, the foreshore zone of the two coasts after six months showed a contrasting development relative to their pre-tsunamiʹs morphological state. Ulee Lheue, on the northwest coast, experienced ongoing erosion of about 15% of the total sediment loss due to the tsunami and land subsidence. The erosion effect from the land subsidence is not pre-dominant in this coast, compared to the erosion that was caused by the tsunami waves. Keeping in mind that the coast is a sand-poor environment, the coastal process under normal condition could not keep pace with not only the sudden loss of sediment due to land subsidence, but also to a greater extent, due to lack of sediment availability in the coastal system to replace the amount of sediment loss due to the tsunami waves. On the other hand, the amount of sediment regain in Lampu Uk was 60% out of the total sediment loss due to the tsunami and land subsidence. It compensated to a great extent the sudden loss of sediments due to land subsidence which was greater than the one on the northwest coast. The wide and shallow inner shelf and higher wave energy in this coastal region can be the controlling factor of this temporary sediment storage and the rapid accretion.