Development of Accurate Tsunami Estimated Times of Arrival for Tsunami-Prone Cities in Aceh, Indonesia

International Journal of Disaster Risk Reduction 14 (2015) 403–410 Contents lists available at ScienceDirect International Journal of Disaster Risk Reduction journal homepage: www.elsevier.com/locate/ijdrr Development of accurate tsunami estimated times of arrival for tsunami-prone cities in Aceh, Indonesia Syamsidik a,n, Teuku Muhammad Rasyif b, Shigeru Kato c a Tsunami Computation and Visualization Laboratory of Tsunami and Disaster Mitigation Research Center (TDMRC) and Civil Engineering Department, Syiah Kuala University, Jl. Syeh Abd Rauff, No. 7, Banda Aceh 23111 Indonesia b Tsunami and Disaster Mitigation Research Center (TDMRC), Syiah Kuala University and Civil Engineering Master's Program, Syiah Kuala University, Jl. Syeh Abd. Rauff, No. 7, Banda Aceh 231111, Indonesia c Department of Architecture and Civil Engineering, Toyohashi University of Technology, 1-1 Tempaku-Cho, Aichi Prefecture, 441-8580, Japan article info abstract Article history: Ten years after the Indian Ocean Tsunami of 2004, the Aceh Province in Indonesia has made progress Received 11 April 2015 toward becoming a more tsunami resilient area. The government of Indonesia has undertaken a number Received in revised form of efforts to facilitate a better evacuation process, but a smooth evacuation process is still at large. A 15 September 2015 major issue is that the disaster management office for the districts are yet to have clear, accurate esti- Accepted 16 September 2015 mations of what would be the shortest time of the arrival of the tsunami waves.The worst scenario for Available online 24 September 2015 these cities' tsunami evacuation procedures has yet to be determined. This study seeks to discern worst Keywords: tsunami estimated times of arrival for the tsunami-prone cities in Aceh. A number of numerical simu- City Evacuation lations were performed using data from past events of tsunamis in this area and a future near-shore Tsunami tsunami events anticipated by most of the disaster managers around the Mentawai Island. The Cornell Numerical simulation Multi-grid COupled Tsunami (COMCOT) model was used as the tool for the simulations. Nine selected ETA COMCOT cities were determined as observation points, i.e., Sabang, Banda Aceh, Calang, Lageun, Teunom, Meu- laboh, 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. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction guideline for related stakeholders and emergency responders be- fore and during emergency period [31]. Visible tsunami evacuation The Indian Ocean Tsunami on December 26, 2004 left behind a signs are found in most of the cities. Although not on a regular stark landscape and initiated a drastic period of change for Aceh basis, the government and population of Aceh have performed Province and the Nias Island of Indonesia. Approximately 230,000 some tsunami evacuation drills. However, disaster management people died and nearly 1,000,000 people suffering from clear authorities still have not figure out how to be prepared for a worst images of the extensive damage caused by the tsunami were case scenario for emergency response to future tsunamis. In ad- displaced [29]. Ten years after the tsunami, Aceh has been re- dition, they are unsure of how such a scenario should be in- covered from the severe destruction and is now in much better corporated into the existing SOP. One complication is that in cities that were not affected by the 2004 tsunami, the perception and condition. A four-year rehabilitation and reconstruction process the preparedness efforts are different or somewhat lacking, leav- conducted in Aceh and the Nias Islands of Indonesia has brought ing them ill-prepared [26]. significant changes to the area, including infrastructure improve- Concerns became even greater after the two major earthquakes ments, new settlements, and new livelihoods [22–25]. At the (8.6 Mw and 8.2 Mw) that occurred on April 11, 2012. The earth- present, Aceh has built eight tsunami escape buildings, a number quakes' epicenters were located off the western part of the Sunda- of siren towers, and several well-designed tsunami escape roads. A Subduction Zone [30]. Although they did not produce a giant provincial standard operating procedure (SOP) for tsunami eva- tsunami, they did cause massive panic in major coastal cities in cuation has been formulated since 2011 [16]. The SOP is an official Aceh. The newly-constructed evacuation facilities were not able to accommodate the sudden spike in traffic. People had not been n trained on how to select the best modes of evacuation. The greater Corresponding author. E-mail addresses: [email protected] (Syamsidik), number of cars on the roads overloaded them and soon created [email protected] (T.M. Rasyif), [email protected] (S. Kato). traffic jams at many places in the cities. In contrast, in the 2004 http://dx.doi.org/10.1016/j.ijdrr.2015.09.006 2212-4209/& 2015 Elsevier Ltd. All rights reserved. 404 Syamsidik et al. / International Journal of Disaster Risk Reduction 14 (2015) 403–410 Fig. 1. Area simulation and points for numerical simulations. Simulations were done in several runs of the process. The color of the rectangles represent areas in the same run of the numerical simulation process. The numbers refer to number of layers of the simulation in Table 1. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) tsunami, the existing escape buildings were almost totally de- not only for nearfield tsunamis, where the ETA is faster than serted. And to make matters worse, the siren towers did not work 30 min, but also for farfield tsunamis. A study conducted around properly [17]. In the 2012 event, people rushed to evacuate due to the southern coast of Myanmar indicated that this area was their experience during the 2004 tsunami. Another good sign was stricken by a tsunami 2.5 h after the first earthquake that triggered that none of them went to the coastal area to pick fish unlike what the December 26, 2004 tsunami [12]. Since the people did not feel happened in the 2004 tsunami. Some schools who have regular any shaking from the earthquake, the ETA information would have training and SOPs for tsunami and earthquake disasters managed helped the community and the government to anticipate the to evacuate their students calmly [27]. However, most of the tsunami [12]. However, those study results are yet to be included evacuation facilities are found in Banda Aceh, the capital city of to improve future evacuation procedures for the study area. Also, Aceh Province. Other cities that have been affected by previous the results have not yet been discussed with emergency managers tsunamis, such as Sabang, Lageun, Calang, Sinabang, and Meulaboh to see the practicality of incorporating the ETA information for were not equipped with such facilities. Although Meulaboh uses those cities. This research uses the Cornell Multi-Grid Coupled two-story shop roofs as shelters, the city still does not have ample Tsunami (COMCOT), a numerical model, to produce ETAs for the escape roads or siren towers. In Tapaktuan and Singkil, the impacts selected cities along the western coasts of Aceh. The results of the of the 2004 tsunami were minor, so the tsunami preparedness modeling were brought into discussions with emergency stake- efforts there have been minimal. Another troubling issue is that holders in the cities to incorporate the results into evacuation these cities have not put any shortest evacuation period into their procedures. evacuation SOPs. Therefore, in this study the goal was to develop and provide worst case tsunami Estimated Times of Arrival (ETAs) for these tsunami-prone cities in Aceh. 2. The study area An ETA is defined as a computed arrival time of the first tsunami wave after the occurrence of an earthquake-generating tsu- Except for Banda Aceh, the western coastal cities of Aceh are nami [8,14,13]. The travel time of the tsunami is correlated with well-known to be less populated in comparison to the eastern evacuation time to improve the number of survivors in tsunami- coasts of Aceh. The population of this area is about one third that impacted coastal areas [15]. City evacuation planning should of the northeastern part. Off the western coast of this area is the consider the shortest time that it will take an anticipated tsunami Sunda Fault where the Indo-Australia tectonic plate and Eurasian to get to their coastal area in order to assure that they can evacuate plate collide with each other. According to United State Geological their residents in time. The ETA and number of evacuees will de- Survey (USGS) data, between 1976 and 2012, there have been 64 termine where tsunami shelters should be placed, evacuation earthquakes in this area with magnitudes greater than 6.5 Mw. It routes, evacuation roads' dimensions, as well as evacuation traffic is anticipated that this tectonically active region will produce fu- management [28]. Numerous models were used to study ETA at ture major earthquakes [6]. Off the coast of the western region various locations. ETAs based on historical tsunami scenarios were there are a number of small islands: Simeulue Island, the Banyak found to be key factors in saving lives [15,21]. Zhang et al. [21] Islands, and the Pulo Aceh Islands. These islands are believed to be introduced a rapid method for estimating the arrival time of tsu- a natural barrier providing protection from the propagating tsunami waves using linear wave theory and data from tsunamis nami waves generated around the subduction zone.

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