lessons learned from the 2010 tsunami around the ...

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Journal of Earthquake and Tsunami Vol. 7, No. 1 (2013) 1350002 (14 pages) c World Scientific Publishing Company DOI: 10.1142/S1793431113500024

J. Earthquake and Tsunami 2013.07. Downloaded from www.worldscientific.com by 39.225.253.131 on 08/11/14. For personal use only.

TSUNAMI MITIGATION MEASURES FOR TSUNAMI PRONE SMALL ISLANDS: LESSONS LEARNED FROM THE 2010 TSUNAMI AROUND THE MENTAWAI ISLANDS OF INDONESIA

SYAMSIDIK Tsunami and Disaster Mitigation Research Center (TDMRC ) Syiah Kuala University Jl. Tgk Abdurrahman, Gampong Pie, Banda Aceh 23233, Indonesia Civil Engineering Department Faculty of Engineering, Syiah Kuala University Jl. Syeh Abdurrauf No. 7, Banda Aceh 23111, Indonesia [email protected] DINAR CATUR ISTIYANTO International Center for Water Hazard and Risk Management (ICHARM ) 1-6, Minamihara, Tsukuba-shi, Ibaraki-ken 305-8516, Japan Received 5 June 2012 Accepted 15 October 2012 Published 30 April 2013 The challenge of protecting communities in tsunami-prone populated small islands is difficult to meet. Likewise, the islands are often found with a lack of disaster mitigation infrastructure. A tsunami that occurred around the Mentawai Islands of Indonesia on October 25, 2010, causing around 500 dead, is the inspiration for this paper. This study was aimed at elaborating practices in protecting communities of small islands from tsunamis by incorporating information about the estimated time of arrival of a tsunami into the islands mitigation measures. A field survey to obtain the impacts of the tsunami on the number of casualties and damages was conducted in February 2011 around the Mentawai Islands. In the survey, a set of questionnaires were distributed in the Mentawai Islands to investigate the small island residents’ responses just after the shock from the tsunami waves. This study was also followed by numerical simulations to obtain tsunami wave Estimated Time of Arrival (ETA) for the Mentawai islands. Numerical simulations were conducted using Delft3D software coupled with Tsunami toolkit. This research found that the ETAs for the Mentawai Islands range between 9–20 min. With the existing tsunami early warning system in Indonesia, the ETAs are quite short. Comparing the Simulated ETAs to the findings from the Mentawai Islands tsunami survey led to the recommendation that the best way to increase the community’s preparedness for a tsunami would be by managing village-based spatial planning. Such spatial planning may include relocating the residents far away from the coastal area. This would enable the community to have more time to evacuate should a tsunami threat occur. Keywords: Delft3D; estimated time of arrival; evacuation; small island; spatial planning.

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Syamsidik & D. C. Istiyanto


1. Introduction A tsunami is a type of disaster characterized by a low frequency of occurrence, but it causes massive damage and a staggering number of human casualties. These characteristics contribute to a sometimes low awareness and a low preparedness level of a coastal community for a potential tsunami. A similar phenomenon contributed to the large number of human casualties due to the Indian Ocean Tsunami in 2004 in Aceh. Although a tsunami of almost similar magnitude occurred in Aceh around 1907, this story did not pass to most of coastal communities in Aceh before 2004. Despite this, some local wisdom of the Simeulue island community about tsunamis, called Smong, is widely spread on the small island, and this saved them during the 2004 Indian Ocean Tsunami: the local indigenous knowledge taught the people of the Simeulue Island to evacuate immediately after confirming a sudden water recession following an earthquake [Gaillard et al., 2008]. The challenge of saving lives during a tsunami becomes more difficult to meet for small islands in Indonesia where the typical islands are situated in relative isolation from the national tsunami early warning system. For the small islands close to a tsunamigenic source of earthquakes (nearfield tsunami cases), the challenge of evacuating people becomes even more serious. As the number of the small islands close to such tsunamigenic sources is large in Indonesia, increasing the community’s preparedness is crucial. The time needed to produce the first tsunami warning in Indonesia and the time needed to deliver the warning to small island communities provides only a quite short time for the community to escape. Furthermore, as the infrastructure for evacuation is relatively minimal, this makes it more difficult to provide ample evacuation facilities for a small island’s community. Therefore, knowing the time of the tsunami waves’ arrival will help the local disaster management authorities of the islands to create the best method for evacuating their people or for providing measures to mitigate the impact of the tsunami on the islands [McAdoo et al., 2009]. Around the Indo–Australian fault that has been actively producing tsunamis in the recent centuries, there are many small islands located off the Sumatra Islands, namely, Pulo Aceh, the Banyak Islands, the Mentawai Islands, and the Enggano Islands. The most recent small islands impacted by a tsunami are the Mentawai Islands. The Mentawai Islands were struck by a tsunami on October 25, 2010. The tsunami was produced by 7.7 Mw of earthquake with the epicenter located at — 3.484◦E and 100.114◦N, and a focal depth of 20.6 km. This earthquake produced tsunami waves as high as 9 m around the Islands [Koresawa, 2011]. The tsunami waves produced by the earthquake were disproportionately large waves following a long rupture duration of about 125 s [Newman et al., 2011]. The number of casualties were 509 dead, 43 missing, 24 injured, and around 7,000 people displaced [BNPB, 2011]. The tsunami also caused a transoceanic disaster as far away as La Réunion Island, located about 5,000 km to the Southwest of the earthquake epicenter. The tsunami took about 7 h and 20 min to travel from its source and to generate about 1.72 m of tsunami wave around La Réunion Island [Sahal and Morin, 2012]. 1350002-2

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Tsunami Mitigation Measures for Tsunami Prone Small Islands


Comparing the human casualties to the total population of the Mentawai Islands (76,173 people) leads to the question of what could have saved the rest of the community despite the difficult situation of the islands? What type of mitigation measures could have been taken by the island community for anticipating the tsunami? This paper is aimed at investigating mitigation measures that have been performed by the island community related to tsunami disaster and elaborating the lessons learned from the October 25, 2010 tsunami around the Mentawai Islands. A field survey was conducted around the impacted area and a set of questionnaires were distributed to selected respondents. Additionally, to estimate the time interval between the earthquake and the first tsunami wave’s arrival at selected shores, numerical simulations were conducted. 2. The Study Area Off the Sumatra Island of Indonesia, there are many lightly populated islands, e.g. Pulo Aceh Islands, Weh Island, the Banyak Islands, the Nias Islands, the Mentawai Islands, and the Enggano Islands. Most of the islands have limited space. Only some of them have any hilly terrain. This study was performed on the Mentawai Islands, which have four major islands, namely the Siberut Island, the Sipora Island, the North Pagai Island, and the South Pagai Island (see Fig. 1). All of these four islands have hilly terrain, but most of the people live near the coastal area. The islands are believed to have been created during the Oligocene or late Eocene era [Curray et al., 1979; van der Werff, 1996]. The presence of the Mentawai Islands at the central offshore of the Sumatra Island is likely the result of the large sediment volume that moved southward from the Indo–Eurasian plate collision. A further process of the collision resulted in an accreted wedge that formed a row of small islands located off Sumatra, where the Mentawai Islands are part of a ridge [McCaffrey, 2009]. Within the small island groups in the Indian Ocean basin, the Mentawai Islands are part of the Northeastern group, together with the Andaman and Nicobar Islands [Poh, 2010]. These islands have been put under intensive scrutiny due to their potential as a place for a giant powerful earthquake that is predicted to be larger than 8.0 Mw. The earthquake may generate a tsunami wave as high as 15 m at the densely populated city of Padang, the main city of West Sumatra Province [McCloskey et al., 2007]. The district of the Mentawai Islands is one of districts in West Sumatra Province. The Mentawai Islands District is the only district in this province that is located far from the mainland of Sumatra Island. The Mentawai Islands District is divided into ten sub-districts. The total population of the Mentawai Islands District, based on 2010 statistical data, is 76,173 [BPS Mentawai, 2011]. The survey in this study was focused on three sub-districts of the islands, namely, Sipora, North Pagai, and South Pagai. These three sub-districts are believed to have been severely affected by the 2010 tsunami. The Mentawai Islands District is considered rather isolated from the major socio-culture conditions of the province. The number of its population 1350002-3

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Table 1. Demographic composition based on educational background by sub-districts of the study area. Name of sub-district Sipora North Pagai South Pagai

Population

No formal education (%)

Elementary school (%)

Secondary school (%)

High school (%)

Higher education school (%)

7,903 4,609 8,243

54.85 34.67 34.65

22.43 29.02 28.99

6.12 13.05 13.05

3.72 10.15 10.19

0.65 0.36 0.35

who graduated from a higher education institution is small. A background of formal education background is related to a community’s capacity to anticipate disaster. The ratio of the Mentawai Islands’ population who graduated from an institution of higher education is believed to influence the island community’s tsunami preparedness. The demographic composition of the three sub-districts, based on educational background, can be seen in Table 1. The island’s residents have limited possibilities to commute within or from the islands to Padang city. The only transportation access to the islands is by sea, either by ferry or by traditional boat. Although the islands are famous for their surfing, public infrastructure and communication lines are apparently inadequate. Transportation between villages (Dusun in the Mentawai’s local language) can be made by a traditional long boat. Electricity is only available in certain villages, such as Tua Pejat (the capital city of the District) and Sikakap (the biggest village in North Pagai Island). Communication by phone is almost impossible for most of the area of the islands. The access to national mainstream news media is only possible at Tua Pejat and at Sikakap. This hinders the people of the islands from receiving real-time information, such as a tsunami warning, from a national tsunami early warning system. 3. Methods This study has two parts: computing the tsunami Estimated Time of Arrivals (ETAs) by means of numerical simulation, and investigating the response of the island residents by means of a questionnaire survey and in-depth discussions with key persons. The computation of the ETAs is aimed at predicting the first tsunami wave arrival to selected observation points in the islands and correlating them to the residents’ responses obtained from the questionnaire survey. The field survey is also aimed at picturing the physical damage caused by the tsunami. 3.1. Simulation of the tsunami ETAs A tsunami wave’s ETA is assumed to correlate with the time of evacuation and number of survivors or casualties at every impacted Dusun. Simulation of the tsunami ETAs was done by Delft3D software made by Deltares [2007]. The Delft3D employs a nonlinear shallow water equation and the Boussinesq assumption. Initially, the 1350002-4

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Delft3D was initiated for simulating non-tsunami hydrodynamic cases. Taking advantage of the Tsunami Toolkit developed in 2004, the Delft3D has been also useful for simulation of the propagation of tsunami waves [Vatvani et al., 2012; Apotsos et al., 2012; Gelfenbaum et al., 2011]. The tsunami toolkit was used to generate a tsunami wave around the earthquake’s epicenter as the initial condition for the simulation. The fault scenario in this toolkit adopts the Okada fault model to transform the seafloor rupture into a surface wave around the epicenter [Okada, 1985]. In this simulation, the data of the fault scenario was obtained from USGS information. The tsunami toolkit coupled with the Delft3D can usefully employ the fault model produced by the USGS even though some previous research has found that the fault model developed based on USGS information has produced overestimates for the 2010 Mentawai Islands tsunami [Hill et al., 2012]. Here, the earthquake was estimated to create a strike of 325◦ and dip of 11.6◦ at −3.484◦E and 100.114◦N with a focal depth of about 20.6 km. Bathymetry data for the simulation used 2-min resolution of ETOPOv2 bathymetry data coupled with hydrographical charts. A set of 30-m Shuttle Radar Topography Mission (SRTM) was used in this simulation. However, since the simulations were aimed at producing ETAs, the resolution of the topography data did not contribute significantly to the results. A Manning number of 0.02 was used uniformly in the simulation domain to represent the sea bed friction. 3.2. Investigation of people’s responses To obtain the people’s responses to the event of the tsunami, a field investigation was done at three sub-districts, as depicted in Fig. 1. Interviews with community leaders, selected respondents, and a questionnaire survey were carried out. The field investigation was conducted between March 9, 2011 and March 16, 2011. The investigation also aimed at finding the measures used by the survivors during the event and at observing community interventions prior to the event that could possibly correlate with successful and unsuccessful tsunami mitigation for the small islands. The questionnaire survey was conducted to find important aspects of the response of the survivors to the tsunami threat. Several key questions, related to their pre-event knowledge of the tsunami, were addressed to 65 respondents of the selected sub-districts. Questions asked in the survey to the respondents as to their reactions to the 7.7 Mw earthquake included such as their reasons for evacuating, their activity just before and after the earthquake, the goods brought along while evacuating, and estimated tsunami wave depths inundating the survivors’ bodies. In-depth interviews to investigate the first response of official disaster management authorities at the provincial, district, and dusun levels were carried out. The first interview was done with Edward (male, age 40) as head of the logistic division at the West Sumatra Disaster Management Agency. The second in-depth interview was done with the Mentawai Islands District’s Government official, represented by Pudjo (male, age 50). The third in-depth interview was conducted with the Head of 1350002-5

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Fig. 1. The Mentawai Islands. Epicenter of 7.7 Mw earthquake that occurred on October 25, 2010 is marked by a red star.

Dusun of Malakopa on the South Pagai Island, Sudirman (male, age 45). The three levels of interviews were expected to represent the responses of the authorities and their policies related to the 2010 tsunami. A set of questionnaires comprising 20 questions were distributed at six Dusuns, namely Dusun Malakopa, Bulasat, Surat 1350002-6

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Aban, Tapak, located on the South Pagai Island, and Dusun Sabeugunggung, and Dusun Montei Teikaku on the North Pagai Island. Observation on spatial interventions that might correlate to tsunami mitigation prior to the tsunami event was also done at the selected dusuns. The educational capacity of the respondents in this survey is fairly similar to the population of the Mentawai Islands. Educational background is believed to be correlated closely with tsunami disaster perception in the community. A similar urgency was also found in the case of the September 29, 2010 tsunami around Niuatoputapu Island of Tonga. Clark et al. [2011] confirmed that the small, isolated islands may have particular issues during response and recovery phases of tsunami that are unlikely to be encountered in a larger region. 4. Results and Discussion 4.1. The ETAs and the islands’ community responses Based on numerical simulations using Delft3D, the ETAs for selected locations can be seen in Table 2. The table shows that the escape window time for the island dwellers was quite limited. It was predicted that there was a time interval between the occurrence of the earthquake and the first evacuation response of the tsunami impacted area. During the interviews with respondent, it was found that the fastest estimated response period of the survivors was about 2 min. As can be seen in Table 2, the distances between the villages to shoreline are varied. The closest distance of the villages to the shoreline is for Dusun Sabeugunggung. This village was once proposed to be relocated to a farther place but this was refused by its residents. On the other survey done at Usa city of Japan, it was found that the first time response was between 5–15 min after the earthquake [Sugimoto et al., 2003]. They also found that the average evacuation speed of the people was about 1.02 m/s if the people run while carrying an infant and about 1.07 m/s in the case the people run without carrying anything. Considering that the 2010 Mentawai tsunami occurred at 21.42 o’clock, local time, most of the people in the islands were resting (either sleeping or no outdoor activity). Looking at this, there was only a limited time for evacuation the location around the South Pagai Island, as

Table 2.

ETAs at selected locations based on numerical simulation.

Name of village

Name of sub-district

ETA (min)

Est. distance to shoreline (m)

Evacuation distance (m)

Surat Aban Bulasat Malakopa Tapak Sabeugunggung South Sipora South Siberut

South Pagai South Pagai South Pagai South Pagai North Pagai Sipora Siberut

9 10 10 11 12 15 20

500 600 800 1,000 20 1,000 1,000

470 500 490 1,500 612 796 1,102

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can also be seen in Table 2. Interestingly, the number of human casualties in the South Pagai Island are fewer than that of the North Pagai Island. One of the worst cases of human casualties due to the tsunami was found at Dusun Sabeugunggung in the North Pagai Island. At this dusun, 117 people died. The tsunami caused structural damage around dusuns located at the western part of the North and South Pagai Islands. Damaged houses at Dusun Surat Aban of the South Pagai Island can be seen in Fig. 2(a). At Dusun Sabeugunggung, the village was flattened by the tsunami (see Fig. 2(b)). Most of the survivors from this dusun mentioned that they were saved by hanging on the remaining trees around the village and they could not reach higher ground due to landcover obstacles and the lack of a designated escape road for the community of the dusun. The community houses were located between 10 to 50 m from the coast. On the other hand, in the backyard of the village, dense vegetation surrounded the village and limited the access of the dusun’s dwellers to higher ground located about 1 km from the village. In contrast, at Dusun Surat Aban on the South Pagai Island, there were no human casualties although the village is the closest village to the earthquake’s epicenter. In terms of ETA, Dusun Surat Aban also had a shorter time to evacuate than that of Dusun Sabeugunggung. The results of the questionnaire revealed that about 40% of the respondents said that they had already learned about the threat of a tsunami and the process involved in a tsunami. About 32% of the respondents did not know about the tsunami before the 2010 tsunami. Based on interviews with selected respondents who had pre-event knowledge of the tsunami process, it was found that the contribution of community-based disaster risk reduction conducted by various parties, such as Non-Governmental Organisations (NGOs) and related government

(a)

(b)

Fig. 2. (a) Houses damaged by the tsunami at Dusun Surat Aban at South Pagai Island (b) Village flattened by tsunami at Dusun Sabeugunggung at North Pagai Island. 1350002-8

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agencies, helped them to understand the disaster. The efforts to increase the island community’s preparedness for a tsunami disaster were increased significantly by these parties especially after the Indian Ocean Tsunami in 2004. The efforts of these parties are interesting due to the lack of IT media in the islands. According to the survey, about 51% the respondents revealed that they started to evacuate immediately after the earthquake (see Fig. 3(a)). Although about 11% of them did not know about the tsunami before the event, they were inspired by other people to run immediately after the earthquake. This finding is similar to the case of the Tohoku 2011 earthquake and its tsunami [Ouchi, 2011]. The remaining respondents answered that they did not evacuate immediately since the mildness of the shaking of the earthquake had misled them. The island community’s perception of the earthquake’s magnitude has been discussed by Yulianto et al. [2012]. This also strengthens the findings that the pre-event knowledge of the island community is good to some extent. Most of the respondents were also not affected directly by the tsunami waves (see Fig. 3(b)). In the figure, a small portion of the respondents said that the height of the tsunami waves had drowned their bodies. The respondents resided at Dusun Muntei Teikaku and Dusun Sabeugunggung of the North Pagai Island. A significant percentage (about 68%) of the respondents felt that they ran very fast during the evacuation (see Fig. 4(a)). Family connection played a significant role during the evacuation process. It is shown in Fig. 4(b) that about 44.6% of the evacuees carried their kids during the evacuation process. As the maternal instinct is strong, taking along a kid with the evacuee is unavoidable. Hence, other support methods to accelerate the evacuation process are vital, such as developing evacuation roads, assigning clear escape locations, and constructing effective early warning system for the community of the small islands.

4.2. The dissemination of the tsunami early warning The Mentawai Islands tsunami occurring on October 25, 2010 gives another proof of the urgency of an effective telecommunication and transportation system during

(a)

(b)

Fig. 3. (a) Reasons for the survivors to evacuate during the tsunami event. (b) Estimated height of the tsunami waves that inundated the survivors. 1350002-9

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(a)

(b)

Fig. 4. (a) Estimated evacuation speed by running of the survivors. (b) Thing(s) carried by the survivors while evacuating.

disaster, especially when dealing with remote islands such as the Mentawai Islands. The unavailability of this system was considered to be one of the roots of the late emergency response in this disaster. The importance of integrated operation and maintenance of a tsunami early warning system was also learned from this disaster event. The tsunami responses by various of the related parties to release the tsunami warning can be seen in Fig. 5. The figure gives several facts related to

Fig. 5. First response and early warning dissemination after the 7.7 Mw earthquake around the Mentawai Islands between October 25–27, 2010. 1350002-10

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the response situation at the initial stage of the Mentawai Islands tsunami. Based on a rapid analysis done by the Meteorological, Climatological, and Geophysical Agency of Indonesia (BMKG), the agency concluded that the earthquake had the potential to generate a tsunami that would effect the coastal area near the epicenter. It was predicted that the tsunami would attack the South Pagai Island at about 21:49:52 local time. Immediately, the BMKG released tsunami warning 5 min after the earthquake through the electronic media as well as a direct message to the local governments including the Mentawai Islands authority. However, as has been elaborated previously, there was no effective electronic medium with which to disseminate this information. The condition became worse when the only electric power in the islands was down due to a lack of fuel. On further process, the tsunami warning was cancelled 47 min later since there was no feedback confirmation from the Mentawai Islands local government about the actual situation from the islands, and the tide-gauge measurement network said there was a small tsunami amplitude (0.2–0.4 m). In fact, the Mentawai Islands regularly experienced a lack of fuel supply to support their daily activities. The first information from the islands to Padang city was only received the next morning, reported by a courier from the Mentawai Islands who had to face 6 h of a tough motorboat journey due to bad sea condition. Immediately after receiving the actual disaster information, emergency responses were started by the Provincial Government of West Sumatra. However, severe sea condition (strong winds and high waves) hampered this emergency response. These unfortunate conditions also resulted in the return of several emergency ships dispatched back to Padang city. A national level emergency coordination meeting was held on the evening of the same day to make a decision on the mobilization of helicopters to support these emergency measures. Nonetheless, the effective response of the disaster authorities were started only the next morning. 4.3. The spatial planning intervention in the islands Looking at the findings about the number of human casualties in one village and another, the correlation between the ETAs and the victims is expected to draw on other contributed parameters. One of the most probable parameters is intervention of the village spatial planning prior to the 2010 tsunami. The spatial planning intervention at the villages was done by relocating the coastal community farther from the coastal area. This was intensively done beginning in 2007. Nevertheless, the intervention was not made, or was challenged, in several villages such as Dusun Sabeugunggung and Dusun Muntei Teikaku of the North Pagai Island. The population of each village, the casualties due to the tsunami, and the relocation process as part of the spatial intervention in the villages before the tsunami, are shown in Table 3. According to Sudirman, the head of Dusun Malakopa, since 2007, almost all the houses near the coastal area had been moved to a higher location in the South 1350002-11

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Table 3.

Spatial planning intervention and casualties at selected villages.

Name of village

Name of sub-district

Surat Aban Bulasat Malakopa Tapak Montei Teikaku Sabeugunggung

South South South South North North

Pagai Pagai Pagai Pagai Pagai Pagai

Population

Number of deaths

Injured

Spatial planning intervention

436 2030 2121 112 260 212

0 1 0 0 113 117

0 13 1 0 90 62

Intervention Intervention Intervention Intervention No Intervention No Intervention

Pagai Island. The remaining houses abandoned in the coastal area were destroyed by the 2010 tsunami. None of the Dusun Malakopa’s residents died because of the tsunami. The National Disaster Management Agency of Indonesia (BNPB) released the data of total deaths due to the tsunami: 509 lives; most of the victims were located on the North Pagai Island [BNPB, 2011]. The statistics of deaths has drawn attention due to the fact that the North Pagai Island is located farther from the earthquake epicenter than the South Pagai Island. At Dusun Surat Aban, Dusun Tapak, and Dusun Malakopa, permanent public facilities such as churches, schools, and village offices were relocated about three years before the tsunami. In contrast to South Pagai Island, the relocation program was difficult or a failure on the North Pagai Island. At Dusun Sabeugunggung, none of the dusun’s dwellers wanted to move away from the coastal area. Among the reasons for this rejection were transportation problems and access to fishery activity. The connection between one dusun to another is difficult by land transportation. Therefore, if they had resided in the inner part of the island, far from the coastal area, it would have added more time for them to reach the boat. Although most of the Mentawai Island people rely for their livelihood on more than one type of occupation, e.g. as farmers and fishermen, being close to the coastal area would make it easier to perform their daily activities. Based on this observation, it was found that the low casualties at several locations is to be attributed to spatial planning intervention at the villages prior to the 2010 Mentawai Island tsunami. The village-based spatial planning intervention seems to be effective as a mitigation measure for tsunami-prone small islands, such as the Mentawai Islands. The low casualties at certain villages, e.g. Surat Aban and Malakopa, were also supported by clear escape locations and roads assigned by the villagers before the tsunami. In these villages, the community had agreed to formulate their own evacuation procedures and escape locations. During the 2010 tsunami, people in these villages responded effectively by following the assigned escape roads to higher ground areas. This did not obtain at Sabeugunggung and Muntei Teikaku. 5. Conclusions This study revealed that the ETAs of tsunami waves on the Mentawai Islands are noticeably short, leaving only a limited window of time for the small island 1350002-12

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community to evacuate. This short evacuation period coupled with the complexity of the landscape of the coastal villages has contributed to the number of casualties. In some villages, where the relocation of the coastal community to the inner part of the small islands made since 2007, the number of deaths was relatively low or none. The low level of deaths in these villages is to be attributed to the spatial planning intervention made before the 2010 tsunami. This study recommends that spatial planning for the small islands should be made in order to mitigate tsunami losses by considering the most probable tsunami wave travel time (ETA), the landscape of the small islands, and the community culture. The integration of the national tsunami early warning system by developing ample communication and transportation infrastructures in the tsunami-prone small islands is urgent in order to increase the island community’s preparedness for tsunami disasters. Acknowledgments The Multi Donor Fund (MDF), through its implementing partner UNDP, has provided financial support for the survey conducted by the authors through Disaster Risk Reduction for Aceh (DRR-A Project) output 3. Thanks also to Try Al Tanto from the Ministry of Marine and Fishery of Indonesia and Reno Arief Rachman from the Coastal Dynamic Studies Research Center of the Agency for the Assessment and Application of Technology of Indonesia (BPDP-BPPT). This paper also has also been assisted by Arizal and Suhada Arief of the Tsunami and Disaster Mitigation Research Center of Syiah Kuala University. The Sea Defense Consultant of The Netherlands has provided Delft3D computational platform for this study. References Apotsos, A., Gelfenbaum, G. and Jaffe, B. [2012] “Time-dependent onshore tsunami response,” Coast. Eng. 64, 73–86. BNPB [2011] “Badan Nasional Penanggulangan Bencana,” The Mentawai Islands Actions Plan (in Bahasa Indonesia), Jakarta. BPS Mentawai [2011] “Badan Pusat Statistik Kabupaten Kepulauan Mentawai,” Kepulauan Mentawai dalam Angka 2011 (in Bahasa Indonesia) Available at http://mentawaikab.bps.go.id/livebeta/?p=104. Accessed on July 20, 2012. Clark, K., Power, W., Nishimura, Y., Kautoke, R. A., Vaiomo’unga, R., Pongi, A. and Fifita, M. [2011] “Characteristics of the 29th September 2010 South Pacific tsunami as observed at Niuatoputopu Island, Tonga,” Earth-Sci. Rev., doi:10.1016/j.earscirev.2010.12.001. Curray, J. R., Moore, D. G., Lawver, L. A., Emmel, F. J., Raitt, R. W., Henry, M. and Kieckhefer, R. [1979] “Tectonics of the Andaman Sea and Burma”. In: Watkins, J. S., Montadert, L. and Dickerson, P. W. (Eds.), Geological and Geophysical Investigations of Continental Margins, Memoir, Vol. 29, American Association of Petroleum Geologists, Tulsa, OK, pp. 189–198. Deltares [2007] Deltares, User Manual Delft3D-Flow: Simulation of Multi-Dimensional Hydrodynamic Flows and Transport Phenomena, Including Sediments (Delft, The Netherlands). 1350002-13

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