Search

There are numerous small populated islands near western Sumatra in Indonesia. The Weh, Banyak, Mentawai, and Enggano islands are home to many Indonesians. These small islands have been found to be effective at reducing tsunami wave energy on several occasions. At the same time, they are situated around Sumatras active subduction zone and are often among the areas most affected by tsunamisas in the case of Pulo Raya Island, in the western Aceh Jaya district about 800 m from Sumatra. Pulo Raya was devastated by the 2004 Indian Ocean tsunami. This study investigates the hydrodynamic processes of reflected tsunami waves and their impact on Pulo Raya, using a Cornell Multi-grid COupled Tsunami (COMCOT) model to simulate the tsunami wave runup and subsequent hydrodynamic processes. The simulation confirms eyewitness accounts that it was not the initial runup, but the reflected waves that devastated the worst-hit areas of the island. As a result, we can recommend that governments and communities on small islands need to anticipate the impacts of reflected waves following a tsunami, especially at lee side of of the island that was perceived to be a safer place by the island community before the 2004 Indian Ocean tsunami.

Fifteen years since the 2004 Indian Ocean tsunami, which caused massive destruction around the Andaman Sea, people have participated in efforts to reduce tsunami risks in Indonesia. However, the most important question continues to be on whether such efforts are sufficient in dealing with tsunami risks. Among the most striking challenges here is bridging the gap in tsunami risk reduction between the Sumatra mainland and among communities in several small islands. Thus, this research aims to investigate the recent conditions of selected towns/cities in tsunami-prone small islands and identify the impediments to their tsunami hazard preparedness. It focuses on comparing efforts in terms of available facilities for tsunami evacuation plans and the tsunami estimated time of arrival (ETA), which is computed based on deterministic tsunami propagation models. In this regard, five of the observed locations are classified as being in a critical tsunami preparedness condition, namely Balai island, Lahewa of Nias Island, Sabeugunggung of North pagai Island, Surat Aban of South Pagai island, and Enggano Island. Most of them have limited space for tsunami evacuation and a short tsunami ETA, which constitutes an extreme condition requiring immediate tsunami mitigation measures. One possible approach is to construct a vertical tsunami evacuation building or modify existing buildings that can be used for tsunami evacuation on the islands. This article also highlights societal aspects related to tsunami preparedness.

Ten years after the Indian Ocean Tsunami of 2004, the Aceh Province in Indonesia has made progress toward becoming a more tsunami resilient area. The government of Indonesia has undertaken a number of efforts to facilitate a better evacuation process, but a smooth evacuation process is still at large. A major issue is that the disaster management office for the districts are yet to have clear, accurate estimations of what would be the shortest time of the arrival of the tsunami waves.The worst scenario for these cities' tsunami evacuation procedures has yet to be determined. This study seeks to discern worst tsunami estimated times of arrival for the tsunami-prone cities in Aceh. A number of numerical simulations were performed using data from past events of tsunamis in this area and a future near-shore tsunami events anticipated by most of the disaster managers around the Mentawai Island. The Cornell Multi-grid COupled Tsunami (COMCOT) model was used as the tool for the simulations. Nine selected cities were determined as observation points, i.e., Sabang, Banda Aceh, Calang, Lageun, Teunom, Meulaboh, Singkil, Sinabang, and Tapaktuan. The results of this research show that the shortest ETAs are Banda Aceh 35 min, Sabang 22 min, Lageun 25 min, Calang 29 min, Teunom 29 min, Meulaboh 35 min, Sinabang 20 min, Singkil 53 min, and Tapaktuan 24 min.