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Storm surge mapping of typhoon Haiyan and its impact in Tanauan, Leyte, Philippines
Author’s Accepted Manuscript Storm Surge Mapping of Typhoon Haiyan and its Impact in Tanauan, Leyte, Philippines Carine J. Yi, Anawat Suppasri, Shuichi Kure, Jeremy D. Bricker, Erick Mas, Maritess Quimpo, Mari Yasuda www.elsevier.com/locate/ijdr
PII: DOI: Reference:
S2212-4209(15)30007-8 http://dx.doi.org/10.1016/j.ijdrr.2015.05.007 IJDRR223
To appear in: International Journal of Disaster Risk Reduction Received date: 7 October 2014 Revised date: 3 May 2015 Accepted date: 3 May 2015 Cite this article as: Carine J. Yi, Anawat Suppasri, Shuichi Kure, Jeremy D. Bricker, Erick Mas, Maritess Quimpo and Mari Yasuda, Storm Surge Mapping of Typhoon Haiyan and its Impact in Tanauan, Leyte, Philippines, International Journal of Disaster Risk Reduction, http://dx.doi.org/10.1016/j.ijdrr.2015.05.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Storm Surge Mapping of Typhoon Haiyan and its Impact in Tanauan, Leyte, Philippines Carine J. Yi1, Anawat Suppasri1, Shuichi Kure1, Jeremy D. Bricker1, Erick Mas1, Maritess Quimpo2 and Mari Yasuda1 1
Carine J. Yi (Corresponding author) International Research Institute of Disaster Science, Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel/Fax: +81 022-217-6367 Email: [email protected] 1
Anawat Suppasri International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81 022-795-7515 Fax: +81 022-795-7514 Email: [email protected] 1
Shuichi Kure International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel/Fax: +81 0227-95-7525 Email: [email protected] 1
Jeremy D. Bricker International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81-22-395-7201 Email: [email protected] 1
Erick Mas International Research Institute of Disaster Science, Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81-22-795-4901 Email: [email protected] 2
Maritess Quimpo Bureau of Research and Standards, Department of Public Works and Highways, Philippines EDSA, Diliman, Quezon City, Philippines Tel: +632-481-0086 Email: [email protected] 1
Mari Yasuda International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81 022-795-7515 Fax: +81 022-795-7514 Email: [email protected]
Abstract Super Typhoon Haiyan (locally known as “Yolanda”), which featured wind speeds of 315 km/h, corresponding to a category 5, struck the Eastern Visayas region of the Philippines on November 8, 2013. The municipality of Tanauan, home to 50,907 people and 9,624 households in 54 barangays was one of the locations in Leyte Province. Because of Typhoon Haiyan, 822 people died in 32 barangays, and 35 people went missing. Tanauan received less attention from international emergency aid organizations than Tacloban or Palo. The survey team of the International Research Institute of Disaster Science, Tohoku University, was deployed to investigate the on-site damage in Tanauan in February, March and May of 2014. The main purpose of the survey was to identify the extent of Typhoon Haiyan’s storm surge; face-to-face interviews were conducted to determine the water limit points. The storm surge flood map based on the surveyed water limit points for Haiyan in 2013 did not match the storm surge hazard map provided by the municipality of Tanauan. The causes of death were reviewed, and 94.7% of the deaths of the 17 Barangays along the coastal area were the result of drowning. To conduct a risk assessment, it is important to develop a digital database that includes geospatial maps and utilizes a cross-section database that contains categorized data and has dynamical accessibility for query functions. The hazard maps can be an effective way to increase residents’ awareness of the natural disaster risk and enhance risk reduction and community resilience.
Key words: Typhoon Haiyan, storm surge extent mapping; risk reduction and risk management Tanauan - Leyte, Philippines
1. Introduction Super Typhoon Haiyan, which featured wind speeds of 315 km/h (195 mile/h), corresponding to a category five storm on the Saffir-Simpson Hurricane Wind Scale, struck the Eastern Visayas region of the Philippines on November 8, 2013 [1][2]. In response to this dire situation, a joint field survey of the Japan Society of Civil Engineers (JSCE) and the Philippine Institute of Civil Engineers (PICE) was conducted from December 12, 2013, to December 16, 2013 [3]. The survey measured inundation and run-up heights at almost 80 different locations along the coast and more than 70 locations in the cities of Tacloban and Palo. The International Research Institute of Disaster Science (IRIDeS) of Tohoku University published a preliminary survey report, which covers the damage level evaluation, storm surge simulation, warning and evacuation assessment, medical assessment and recovery assessment [4]. The municipality’s primary data, such as demographic information, statistical data, and spatial
data, are not publicly available, which affected the post-disaster analysis. For this reason, the survey team of IRIDeS was deployed to investigate the on-site damage in Tanauan in February and March of 2014. Tanauan was chosen for several reasons. First, its damage types were complicated by wind, storm surge and flooding, and it is located within Leyte Province. Second, Tanauan received less attention from international emergency aid organizations than the City of Tacloban or Municipality of Palo. Third, there was a lack of risk reduction related to documented information about Tanauan. Tanauan provided hazard maps beginning in 2007; however, the strength of Typhoon Haiyan exceeded the scale of these estimations and left tremendous devastation behind. The survey objectives were to create a storm surge flooding map and conduct demographic thematic mapping to understand the human damage condition and future risk assessment. The team members interviewed residents about whether the water reached their house, the time at which flooding occurred and subsided, the direction of the water movement, and whether the water was salty. Based on the residents’ reports, the inundation depth was measured from the surface of the road; roads were commonly found above the ground level. Additionally, some human damage impacts on the periphery were reviewed.
2. Introduction to Tanauan 2.1 Background of Tanauan Tanauan
is
a
second-class
municipality and one of the oldest towns in Leyte Province, Philippines (see
Figure
1).
agricultural/industrial
It
is
town
an and
eco-tourism destination in Eastern Visayas. Tanauan has a land area of 7,877 hectares and is bordered by Palo to the north; Tacloban is located beyond Palo to the north [5]. Both towns were severely damaged by Typhoon Haiyan. The municipality of Tanauan provided a summary of its demographic statistics for 2012. Its
Figure 1. Location of the municipality of Tanauan, Leyte Island, Eastern Visayas.
total population is 50,907 (26,134 males and 24,648 females), and 9,624 households are located in 54 barangays (village-scale settlements), which is the smallest administrative division in the Philippines. Only 45.9% (23,387) of
the total population is currently employed, and 9.9% (2,316) of the labor population is recorded as being unemployed. The income of Tanauan residents is largely derived from agriculture and fishing [6]. In 2012, 10.5% of people were living in poverty in Tanauan [7], compared to 27.6% of Filipino families overall [8]. Small-scale industries associated with the production of rice and coconuts, local staple crops, are the main industries in this area [5]. Tanauan hosts three well-known manufacturing companies: Pepsi Cola (Tanauan Plant), Wella Metal Corporation and New Leyte Edible Oil Manufacturing Corporation. 2.2 Preparation for the Flood The Filipino people are at risk of water-related disasters, with storms being a primary concern. Water-related disasters, especially storms, are the most frequent natural disasters in the Philippines, which is shown in figure 2; 73.7 % people were killed by storms and 6.6% by floods between 1980 and 2010 [9]. Coastal towns in Leyte Province experienced powerful tropical storms in 1897 and 1912. In 1897, 400 Europeans and 6,000
Figure 2. Percentage of reported people killed by disaster type in the Philippines. (*Including tsunami)(Data source: EM-DAT and PreventionWeb.net)
natives lost their lives; 15,000 died in 1912, and Typhoon Haiyan killed thousands of people in 2013 [10]. The Community-Based Flood Early Warning System (CBFEWS) of the Philippines Atmospheric, Geophysical & Astronomical
Figure 3. Storm surge hazard map of Tanauan. (Source: the municipality of Tanauan)
Services Administration (PAGASA), in connection with the READY Project under the United Nations Development Program (UNDP), empowers local government units (LGUs) [11][12][13]. Its main objectives include multi-hazard mapping and encouraging communities to protect themselves against floods. The hazard mapping prepared by the municipality of Tanauan in 2007 includes tsunamis, rainfall-induced landslides, floods, and storm surge risk. The storm surge map of Tanauan, which is shown in Figure 3, suggests that the flooded area due to the storm surge extended inland by 330 m. The flood area is shown in pink in Figure 3. Because of Typhoon Haiyan, in Tanauan, 822 people died in 32 barangays (as of February 6, 2014), and 35 people went missing (as of March 19, 2014). Tanauan/Palo experienced approximately 271 km/h onshore 10-minute sustained winds by the Japan Meteorological Agency [14]. Figure 4 shows the maximum still water level (the height the sea rose to) and the maximum wave height obtained by numeric simulation. The municipality of Tanauan was severely affected by a 3-m storm surge in addition to the waves [15].
Figure 4. a) The maximum still water level (the height to which the sea rose) and b) the maximum significant wave height (m) in San Pedro and San Pablo Bay (both are simulated heights (Bricker, 2014)).
3. Storm Surge Extent Mapping due to Typhoon Haiyan The face-to face interview survey method was utilized to explore residents’ personal experience with Typhoon Haiyan and gather related information (see Figure 5). The team members obtained answers from more than 160 victims about when the flooding occurred and subsided, the direction of the water
Figure 5. Interviewing victims.
movement, whether the water was salty, and the inundation depth. For residents who witnessed flooding in their homes, the time of the flooding differed by the location of their residence. Flooding between 6:30 and 7:00 a.m. was considered to
be storm surge flooding, while flooding in the low-land areas beside the Binahaan River at approximately 8:00 a.m. was considered to be river overflow. The Tacloban station (PAGASA) lost their precipitation records and data due to the storm surge. However, Global Satellite Mapping of Precipitation
(GSMap,
refer
Japan
Aerospace
http://sharaku.eorc.jaxa.jp/GSMaP_crest/index_j.html)
Exploration released
Agency
(JAXA)
near-real-time
website;
satellite-derived
rainfall data that showed 250 mm of rainfall during 72 hours of the Haiyan event (21:00 November 6 to 20:00 November 9); however, there are concerns regarding uncertainties and biases in the rainfall data [16]. In accordance with the testimonies of the residents, the water height near the river was between 50 cm and 1 m. Figure 6 shows the extent of the flooded area caused by Typhoon Haiyan based on survey points in Tanauan. The storm surge flood map generated by the survey team did not match the storm surge map (Figure 2) provided by the municipality of Tanauan. The 28 valid storm surge limitation points in Tanauan were identified by interviewing residents, and 6 points in Tanauan were provided by the JSCE [17]. Based on residents’ testimonies, the inundation depth was measured on the road surface using a laser rangefinder and a tape measure. Additionally, related information, such as the time that the flooding occurred and subsided, the direction of the water movement, and whether the water was salty, was gathered. Based on testimonies, the residents living near the river stated that they experienced two flooding events, one from the coast and one from the river They saw water increasing at approximately 6:30am and subsided within an hour. The second event came from the river, which occurred at approximately 8:00am. Some of the residents tasted the water to determine if it was salty. The points were recorded using a GPS digital camera to obtain accurate locations as GPS coordinates. Photographs were imported into GIS software (ArcGIS Desktop 10.1) as point
Figure. 6. The extent of the flooded area based on survey points in Tanauan.
features. The obtained information was then added to the point feature as an attribute. The municipality of Tanauan provided geospatial base maps, including roads, barangay’s boundary polygons, rivers, and hills. The coordinates of this data set were projected to GCS_WGS_1984. The Google Earth image was referenced to identify locations. The area west of the Pan-Philippine highway featured inaccessible open areas in which bushes and coconut trees grow naturally. The 30 m
STRM
image
(Shuttle
Radar
Topography
Mission,
refer
NASA
website;
http://www2.jpl.nasa.gov/srtm/) was arbitrarily used for open areas to identify the ground elevation. The Japan Society of Civil Engineers (JSCE) provided their survey points with the inundation depth values on Google Earth. Mas et al. (2014) measured the inundation depth points in downtown Tacloban [18]. Google Earth kml format files were converted and imported into the ArcGIS shape file format and referenced to create the storm surge flooding map.
4. Discussion of the different types of damage to buildings Tanauan was the second most severely damaged area by Typhoon Haiyan in Leyte Province [19]. Figure 7 compares the Google Earth images of downtown Tanauan before (as of February 23, 2012) and two days after (November 10, 2013) the event. The red circle indicates the pier of the New Leyte Edible Oil Manufacturing Corporation that was destroyed by Typhoon Haiyan.
Figure 7. (left) Images of downtown Tanauan on February 23, 2012, and (right) in the aftermath of Typhoon Haiyan on November 13, 2013. (Source: Google Earth) The building destruction conditions can be broadly classified by the structure of the house: concrete or wood and bricks. Wood and brick houses were totally destroyed by the storm surge, and concrete houses were severely damaged. For example, the Santa Cruz Primary School was entirely destroyed (see Figure 8 a)); the school was located only 425 m from the coast and constructed of bricks. The school was constructed with irregular interval wired reinforcement though the bricks; its walls were coated with painted cement. Figure 8 b) shows the damaged houses along the coast; most of the houses were washed away by the storm surge.
a) b) Figure. 8. a) Santa Cruz Primary School located on the coast and b) a village near an oil company along the coast.
5. Discussion of causes of death The cause of death data were obtained from the death registrar office of the Municipality of Tanauan and were
presented
as
features
and
integrated as a geospatial attribute. Figure 9 and Figure 10 indicate the number of deaths and missing persons by barangay due to Typhoon Haiyan. Deaths were prominent throughout
Figure. 9. Distribution of the number of deaths.
Tanauan; the primary cause of death in inland
areas
was
strong
winds.
According to the testimonies of the residents, a man died when a coconut tree fell on his house. Deaths by drowning and the number of missing persons
were
conspicuously
concentrated in the coastal areas. The number of deaths in Brangay Calogcog and Barangay Santa Cruz were 164 and 125, respectively, corresponding to 14.7% and 14.6% of the population. The corresponding values for Barangay
Figure. 10. Distribution of the number of missing people.
Mohon and Barangay San Roque were 117 and 82, respectively. The Barangay Santa Cruz reported 20 people missing, the highest number for any barangay.
Figure 11 shows the cause of death for the 722 cases reported between November 25, 2013, and May 16, 2014. Based on the records of the death certificates obtained from the Municipal Civil Registrar Office of Tanauan, 94.7% (683 people) were pronounced dead by drowning by doctors in 17 barangays. Cerebral hemorrhage (11 people, 1.5%) was the second leading cause of death, and internal organ failure, such as congestive heart failure or respiratory arrest, was the third cause. Injury and wound infection was the fourth cause of the death (7 people, 1.0%). The investigation into the land of Tanauan revealed that two people died after a house collapsed, which occurred when a coconut tree fell on the house. Some of the inland barangays and barangays located beside the Binahaan River suffered deaths. The creeks were running from the west, and the riverside area was uncultivated lowland.
Figure 11. Cause of death for the casualties of Typhoon Haiyan.
6. Recommendations The municipality of Tanauan, a very small town, was the second most damaged town after Tacloban, losing over 800 residents, most of whom lived along the coast. This number is similar to the records of the death certificates in the Municipal Civil Registrar Office, which lists 683 people (94.7%) from 17 coastal barangays as having drowned. The storm surge flooding map produced by the IRIDeS survey team can serve as a useful tool for the Tanauan staff, who have difficulty identifying the storm surge water limitation boundaries without aid. Without a high-resolution Digital Elevation Model (DEM), the storm surge inundation map provides only an initial assessment. Different damage types were observed at different locations. Residential wooden houses close to the coast were washed out by the storm surge in the early morning, whereas houses beside the Binahaan River flooded when the river overflowed at a later time during the storm event.
Leelawat et al. (2014) noted that the PAGASA earned the trust of the people as an official information source for warnings about flooding and typhoons [20]. Nevertheless, 94.7% of the deaths were due to drowning, which is supported by the fact that the numbers of individuals dead or missing are concentrated in storm surge flooded area. In the aftermath of Typhoon Haiyan, interpretation of the scientific terms used in the warning system should be further considered for risk communication. It appears that Tanauan’s residents did not realize that a storm surge hazard map existed. Typhoons are regular hazards in this area, and previous experience partially affected the evacuation behavior of the residents [21][22]. In addition, the relationship between the barangay captain and community members is a strong factor for obtaining information. Therefore, community-level political activities also affect communication risks. The difficulty acquiring data may delay the estimation of the damage and early-stage responses. Additionally, the accuracy of data affects the accuracy of the risk assessment. Therefore, developing a geospatial data set associated with the tabulated database should be prioritized for early-stage response analysis and future risk mitigation. The hazard maps produced by the READY project were only displayed in the central governmental building, not the barangay buildings. This storm surge extent map based on Typhoon Haiyan can be used as preliminary information and to improve Tanauan’ storm surge hazard map. Displaying the hazard maps in every barangay office may be an effective means to raise residents’ awareness of the natural disaster risk and enhance the community’s resilience, which is especially important due to global climate-change scientists’ warning that the same class of natural disaster will occur frequently in the future [23] [24].
ACKNOWLEDGMENTS: This study was funded by a discretionary budget from the president of Tohoku University and the director of the International Research Institute of Disaster Science (IRIDeS), Tohoku University, and Tokio Marine & Nichido Fire Insurance Co., Ltd. We deeply thank the officers of the Planning Departments of the Municipality of Tanauan, Ms. Cecile Mae M. Ocado, Ms. Dayday M. De La Cruz and Mr. Jerome S. Fabre, who provided the geospatial data set and its attribute values.
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Ronwaldo, Aquino, William Mata, Justin Caldez, and Ferdinand Briones, 2014. Initial report of JSCE-PICE joint survey of the storm surge disaster caused by typhoon Haiyan, Coastal Engineering Journal, Vol. 56, No. 1. 4. International Research Institute of Disaster Science (IRIDeS), 2014, IRIDeS Fact-finding missions to Philippines (Initial Report), Tohoku University. 5. Philippine Commission on Women (PCW), 2012, Gender Responsive Local Economic Governance: Creating and Sustaining an Enabling Environment for Women’s Economic Empowerment, Publication online 2012-09-07. 6. Trinh D Nguyen, 12 Novemner, 2013, After the storm: The Philippines copes with catastrophe, HSBC Global Research. 7. Bernadette B. Balamban, Mildred B. Addawe and Mary Grace G. Darunday, 2013, Official Poverty Statistics and Poverty Reduction Programs of the Philippines. 8. National Statistical Coordination Board (NSCB), 2004, Other Measures of Poverty by Province, Year and Indicator. 9. PreventionWeb.net; Philippines - Disaster Statistics, http://www.preventionweb.net/english/countries/statistics/?cid=135 (Accessed 2014.05.08). 10. Ambeth R. Ocampo, 2014, History replayed, ROGUE, Volume 7 Issue 72, pp.107. 11. Philippines government, Philippines: The national disaster risk reduction and management plan (NDRRMP) 2011 to 2028, 2011 (http://preventionweb.net/go/35457) 12. Hazards Mapping and Assessment for Effective Community-Based Disaster Risk Management: ANNUAL REPORT (1 January 2009 – 31 December 2009) http://aid.dfat.gov.au/countries/eastasia/philippines/Documents/dcrm-ready-project-reportipm.pdf (Accessed 2014.05.12) 13. NDRRMC: Situation Report No.78 Effects of Typhoon “YOLANDA” (HAIYAN) - 31 December 2013. 6:00 AM. 14. Olaf Moritz Neussner, 2014, Assessment of early warning efforts in Leyte for typhoon Haiyan/ Yolanda, Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) (Germany - gov). 15. Bricker, J. 2014, Spatial variation of damage due to storm surge and waves during Typhoon Haiyan in the Philippines, in: Proceedings of Coastal Engineering, JSCE, pp. 1-4. 16. Syuichi Kure, Maritess S. Quimpo, Jeremy Bricker and Akira Mano, 2015, flood runoff responsenses to T1330 (Haiyan) of rivers in Leyte Island, Philippines, The Journal of Japan Society of Civil Engineers, Vol. 9. 17. Haiyan surge height result, 2013, Coastal Engineering Committee - Japan Society of Civil Engineers (JSCE), Available: http://www.coastal.jp/ja/index.php?2013 年台風 Haiyan によるフ ィリピン災害 18. Mas, E., Kure, S., Bricker, J., Adriano, B., Yi, C., Suppasri, A., Koshimura, S. 2014, Field
survey and damage inspection after the 2013 Typhoon Haiyan in The Philippines, Proceedings of the Coastal Engineering Conference of the Society of Civil Engineers, Vol. 70, No. 2. 19. The
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PII: DOI: Reference:
S2212-4209(15)30007-8 http://dx.doi.org/10.1016/j.ijdrr.2015.05.007 IJDRR223
To appear in: International Journal of Disaster Risk Reduction Received date: 7 October 2014 Revised date: 3 May 2015 Accepted date: 3 May 2015 Cite this article as: Carine J. Yi, Anawat Suppasri, Shuichi Kure, Jeremy D. Bricker, Erick Mas, Maritess Quimpo and Mari Yasuda, Storm Surge Mapping of Typhoon Haiyan and its Impact in Tanauan, Leyte, Philippines, International Journal of Disaster Risk Reduction, http://dx.doi.org/10.1016/j.ijdrr.2015.05.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Storm Surge Mapping of Typhoon Haiyan and its Impact in Tanauan, Leyte, Philippines Carine J. Yi1, Anawat Suppasri1, Shuichi Kure1, Jeremy D. Bricker1, Erick Mas1, Maritess Quimpo2 and Mari Yasuda1 1
Carine J. Yi (Corresponding author) International Research Institute of Disaster Science, Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel/Fax: +81 022-217-6367 Email: [email protected] 1
Anawat Suppasri International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81 022-795-7515 Fax: +81 022-795-7514 Email: [email protected] 1
Shuichi Kure International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel/Fax: +81 0227-95-7525 Email: [email protected] 1
Jeremy D. Bricker International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81-22-395-7201 Email: [email protected] 1
Erick Mas International Research Institute of Disaster Science, Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81-22-795-4901 Email: [email protected] 2
Maritess Quimpo Bureau of Research and Standards, Department of Public Works and Highways, Philippines EDSA, Diliman, Quezon City, Philippines Tel: +632-481-0086 Email: [email protected] 1
Mari Yasuda International Research Institute of Disaster Science, Tohoku University, Japan Tohoku University, Japan 468-1 Aoba, Aramakiaza, Aoba-ku, Sendai 980-0845 JAPAN Tel: +81 022-795-7515 Fax: +81 022-795-7514 Email: [email protected]
Abstract Super Typhoon Haiyan (locally known as “Yolanda”), which featured wind speeds of 315 km/h, corresponding to a category 5, struck the Eastern Visayas region of the Philippines on November 8, 2013. The municipality of Tanauan, home to 50,907 people and 9,624 households in 54 barangays was one of the locations in Leyte Province. Because of Typhoon Haiyan, 822 people died in 32 barangays, and 35 people went missing. Tanauan received less attention from international emergency aid organizations than Tacloban or Palo. The survey team of the International Research Institute of Disaster Science, Tohoku University, was deployed to investigate the on-site damage in Tanauan in February, March and May of 2014. The main purpose of the survey was to identify the extent of Typhoon Haiyan’s storm surge; face-to-face interviews were conducted to determine the water limit points. The storm surge flood map based on the surveyed water limit points for Haiyan in 2013 did not match the storm surge hazard map provided by the municipality of Tanauan. The causes of death were reviewed, and 94.7% of the deaths of the 17 Barangays along the coastal area were the result of drowning. To conduct a risk assessment, it is important to develop a digital database that includes geospatial maps and utilizes a cross-section database that contains categorized data and has dynamical accessibility for query functions. The hazard maps can be an effective way to increase residents’ awareness of the natural disaster risk and enhance risk reduction and community resilience.
Key words: Typhoon Haiyan, storm surge extent mapping; risk reduction and risk management Tanauan - Leyte, Philippines
1. Introduction Super Typhoon Haiyan, which featured wind speeds of 315 km/h (195 mile/h), corresponding to a category five storm on the Saffir-Simpson Hurricane Wind Scale, struck the Eastern Visayas region of the Philippines on November 8, 2013 [1][2]. In response to this dire situation, a joint field survey of the Japan Society of Civil Engineers (JSCE) and the Philippine Institute of Civil Engineers (PICE) was conducted from December 12, 2013, to December 16, 2013 [3]. The survey measured inundation and run-up heights at almost 80 different locations along the coast and more than 70 locations in the cities of Tacloban and Palo. The International Research Institute of Disaster Science (IRIDeS) of Tohoku University published a preliminary survey report, which covers the damage level evaluation, storm surge simulation, warning and evacuation assessment, medical assessment and recovery assessment [4]. The municipality’s primary data, such as demographic information, statistical data, and spatial
data, are not publicly available, which affected the post-disaster analysis. For this reason, the survey team of IRIDeS was deployed to investigate the on-site damage in Tanauan in February and March of 2014. Tanauan was chosen for several reasons. First, its damage types were complicated by wind, storm surge and flooding, and it is located within Leyte Province. Second, Tanauan received less attention from international emergency aid organizations than the City of Tacloban or Municipality of Palo. Third, there was a lack of risk reduction related to documented information about Tanauan. Tanauan provided hazard maps beginning in 2007; however, the strength of Typhoon Haiyan exceeded the scale of these estimations and left tremendous devastation behind. The survey objectives were to create a storm surge flooding map and conduct demographic thematic mapping to understand the human damage condition and future risk assessment. The team members interviewed residents about whether the water reached their house, the time at which flooding occurred and subsided, the direction of the water movement, and whether the water was salty. Based on the residents’ reports, the inundation depth was measured from the surface of the road; roads were commonly found above the ground level. Additionally, some human damage impacts on the periphery were reviewed.
2. Introduction to Tanauan 2.1 Background of Tanauan Tanauan
is
a
second-class
municipality and one of the oldest towns in Leyte Province, Philippines (see
Figure
1).
agricultural/industrial
It
is
town
an and
eco-tourism destination in Eastern Visayas. Tanauan has a land area of 7,877 hectares and is bordered by Palo to the north; Tacloban is located beyond Palo to the north [5]. Both towns were severely damaged by Typhoon Haiyan. The municipality of Tanauan provided a summary of its demographic statistics for 2012. Its
Figure 1. Location of the municipality of Tanauan, Leyte Island, Eastern Visayas.
total population is 50,907 (26,134 males and 24,648 females), and 9,624 households are located in 54 barangays (village-scale settlements), which is the smallest administrative division in the Philippines. Only 45.9% (23,387) of
the total population is currently employed, and 9.9% (2,316) of the labor population is recorded as being unemployed. The income of Tanauan residents is largely derived from agriculture and fishing [6]. In 2012, 10.5% of people were living in poverty in Tanauan [7], compared to 27.6% of Filipino families overall [8]. Small-scale industries associated with the production of rice and coconuts, local staple crops, are the main industries in this area [5]. Tanauan hosts three well-known manufacturing companies: Pepsi Cola (Tanauan Plant), Wella Metal Corporation and New Leyte Edible Oil Manufacturing Corporation. 2.2 Preparation for the Flood The Filipino people are at risk of water-related disasters, with storms being a primary concern. Water-related disasters, especially storms, are the most frequent natural disasters in the Philippines, which is shown in figure 2; 73.7 % people were killed by storms and 6.6% by floods between 1980 and 2010 [9]. Coastal towns in Leyte Province experienced powerful tropical storms in 1897 and 1912. In 1897, 400 Europeans and 6,000
Figure 2. Percentage of reported people killed by disaster type in the Philippines. (*Including tsunami)(Data source: EM-DAT and PreventionWeb.net)
natives lost their lives; 15,000 died in 1912, and Typhoon Haiyan killed thousands of people in 2013 [10]. The Community-Based Flood Early Warning System (CBFEWS) of the Philippines Atmospheric, Geophysical & Astronomical
Figure 3. Storm surge hazard map of Tanauan. (Source: the municipality of Tanauan)
Services Administration (PAGASA), in connection with the READY Project under the United Nations Development Program (UNDP), empowers local government units (LGUs) [11][12][13]. Its main objectives include multi-hazard mapping and encouraging communities to protect themselves against floods. The hazard mapping prepared by the municipality of Tanauan in 2007 includes tsunamis, rainfall-induced landslides, floods, and storm surge risk. The storm surge map of Tanauan, which is shown in Figure 3, suggests that the flooded area due to the storm surge extended inland by 330 m. The flood area is shown in pink in Figure 3. Because of Typhoon Haiyan, in Tanauan, 822 people died in 32 barangays (as of February 6, 2014), and 35 people went missing (as of March 19, 2014). Tanauan/Palo experienced approximately 271 km/h onshore 10-minute sustained winds by the Japan Meteorological Agency [14]. Figure 4 shows the maximum still water level (the height the sea rose to) and the maximum wave height obtained by numeric simulation. The municipality of Tanauan was severely affected by a 3-m storm surge in addition to the waves [15].
Figure 4. a) The maximum still water level (the height to which the sea rose) and b) the maximum significant wave height (m) in San Pedro and San Pablo Bay (both are simulated heights (Bricker, 2014)).
3. Storm Surge Extent Mapping due to Typhoon Haiyan The face-to face interview survey method was utilized to explore residents’ personal experience with Typhoon Haiyan and gather related information (see Figure 5). The team members obtained answers from more than 160 victims about when the flooding occurred and subsided, the direction of the water
Figure 5. Interviewing victims.
movement, whether the water was salty, and the inundation depth. For residents who witnessed flooding in their homes, the time of the flooding differed by the location of their residence. Flooding between 6:30 and 7:00 a.m. was considered to
be storm surge flooding, while flooding in the low-land areas beside the Binahaan River at approximately 8:00 a.m. was considered to be river overflow. The Tacloban station (PAGASA) lost their precipitation records and data due to the storm surge. However, Global Satellite Mapping of Precipitation
(GSMap,
refer
Japan
Aerospace
http://sharaku.eorc.jaxa.jp/GSMaP_crest/index_j.html)
Exploration released
Agency
(JAXA)
near-real-time
website;
satellite-derived
rainfall data that showed 250 mm of rainfall during 72 hours of the Haiyan event (21:00 November 6 to 20:00 November 9); however, there are concerns regarding uncertainties and biases in the rainfall data [16]. In accordance with the testimonies of the residents, the water height near the river was between 50 cm and 1 m. Figure 6 shows the extent of the flooded area caused by Typhoon Haiyan based on survey points in Tanauan. The storm surge flood map generated by the survey team did not match the storm surge map (Figure 2) provided by the municipality of Tanauan. The 28 valid storm surge limitation points in Tanauan were identified by interviewing residents, and 6 points in Tanauan were provided by the JSCE [17]. Based on residents’ testimonies, the inundation depth was measured on the road surface using a laser rangefinder and a tape measure. Additionally, related information, such as the time that the flooding occurred and subsided, the direction of the water movement, and whether the water was salty, was gathered. Based on testimonies, the residents living near the river stated that they experienced two flooding events, one from the coast and one from the river They saw water increasing at approximately 6:30am and subsided within an hour. The second event came from the river, which occurred at approximately 8:00am. Some of the residents tasted the water to determine if it was salty. The points were recorded using a GPS digital camera to obtain accurate locations as GPS coordinates. Photographs were imported into GIS software (ArcGIS Desktop 10.1) as point
Figure. 6. The extent of the flooded area based on survey points in Tanauan.
features. The obtained information was then added to the point feature as an attribute. The municipality of Tanauan provided geospatial base maps, including roads, barangay’s boundary polygons, rivers, and hills. The coordinates of this data set were projected to GCS_WGS_1984. The Google Earth image was referenced to identify locations. The area west of the Pan-Philippine highway featured inaccessible open areas in which bushes and coconut trees grow naturally. The 30 m
STRM
image
(Shuttle
Radar
Topography
Mission,
refer
NASA
website;
http://www2.jpl.nasa.gov/srtm/) was arbitrarily used for open areas to identify the ground elevation. The Japan Society of Civil Engineers (JSCE) provided their survey points with the inundation depth values on Google Earth. Mas et al. (2014) measured the inundation depth points in downtown Tacloban [18]. Google Earth kml format files were converted and imported into the ArcGIS shape file format and referenced to create the storm surge flooding map.
4. Discussion of the different types of damage to buildings Tanauan was the second most severely damaged area by Typhoon Haiyan in Leyte Province [19]. Figure 7 compares the Google Earth images of downtown Tanauan before (as of February 23, 2012) and two days after (November 10, 2013) the event. The red circle indicates the pier of the New Leyte Edible Oil Manufacturing Corporation that was destroyed by Typhoon Haiyan.
Figure 7. (left) Images of downtown Tanauan on February 23, 2012, and (right) in the aftermath of Typhoon Haiyan on November 13, 2013. (Source: Google Earth) The building destruction conditions can be broadly classified by the structure of the house: concrete or wood and bricks. Wood and brick houses were totally destroyed by the storm surge, and concrete houses were severely damaged. For example, the Santa Cruz Primary School was entirely destroyed (see Figure 8 a)); the school was located only 425 m from the coast and constructed of bricks. The school was constructed with irregular interval wired reinforcement though the bricks; its walls were coated with painted cement. Figure 8 b) shows the damaged houses along the coast; most of the houses were washed away by the storm surge.
a) b) Figure. 8. a) Santa Cruz Primary School located on the coast and b) a village near an oil company along the coast.
5. Discussion of causes of death The cause of death data were obtained from the death registrar office of the Municipality of Tanauan and were
presented
as
features
and
integrated as a geospatial attribute. Figure 9 and Figure 10 indicate the number of deaths and missing persons by barangay due to Typhoon Haiyan. Deaths were prominent throughout
Figure. 9. Distribution of the number of deaths.
Tanauan; the primary cause of death in inland
areas
was
strong
winds.
According to the testimonies of the residents, a man died when a coconut tree fell on his house. Deaths by drowning and the number of missing persons
were
conspicuously
concentrated in the coastal areas. The number of deaths in Brangay Calogcog and Barangay Santa Cruz were 164 and 125, respectively, corresponding to 14.7% and 14.6% of the population. The corresponding values for Barangay
Figure. 10. Distribution of the number of missing people.
Mohon and Barangay San Roque were 117 and 82, respectively. The Barangay Santa Cruz reported 20 people missing, the highest number for any barangay.
Figure 11 shows the cause of death for the 722 cases reported between November 25, 2013, and May 16, 2014. Based on the records of the death certificates obtained from the Municipal Civil Registrar Office of Tanauan, 94.7% (683 people) were pronounced dead by drowning by doctors in 17 barangays. Cerebral hemorrhage (11 people, 1.5%) was the second leading cause of death, and internal organ failure, such as congestive heart failure or respiratory arrest, was the third cause. Injury and wound infection was the fourth cause of the death (7 people, 1.0%). The investigation into the land of Tanauan revealed that two people died after a house collapsed, which occurred when a coconut tree fell on the house. Some of the inland barangays and barangays located beside the Binahaan River suffered deaths. The creeks were running from the west, and the riverside area was uncultivated lowland.
Figure 11. Cause of death for the casualties of Typhoon Haiyan.
6. Recommendations The municipality of Tanauan, a very small town, was the second most damaged town after Tacloban, losing over 800 residents, most of whom lived along the coast. This number is similar to the records of the death certificates in the Municipal Civil Registrar Office, which lists 683 people (94.7%) from 17 coastal barangays as having drowned. The storm surge flooding map produced by the IRIDeS survey team can serve as a useful tool for the Tanauan staff, who have difficulty identifying the storm surge water limitation boundaries without aid. Without a high-resolution Digital Elevation Model (DEM), the storm surge inundation map provides only an initial assessment. Different damage types were observed at different locations. Residential wooden houses close to the coast were washed out by the storm surge in the early morning, whereas houses beside the Binahaan River flooded when the river overflowed at a later time during the storm event.
Leelawat et al. (2014) noted that the PAGASA earned the trust of the people as an official information source for warnings about flooding and typhoons [20]. Nevertheless, 94.7% of the deaths were due to drowning, which is supported by the fact that the numbers of individuals dead or missing are concentrated in storm surge flooded area. In the aftermath of Typhoon Haiyan, interpretation of the scientific terms used in the warning system should be further considered for risk communication. It appears that Tanauan’s residents did not realize that a storm surge hazard map existed. Typhoons are regular hazards in this area, and previous experience partially affected the evacuation behavior of the residents [21][22]. In addition, the relationship between the barangay captain and community members is a strong factor for obtaining information. Therefore, community-level political activities also affect communication risks. The difficulty acquiring data may delay the estimation of the damage and early-stage responses. Additionally, the accuracy of data affects the accuracy of the risk assessment. Therefore, developing a geospatial data set associated with the tabulated database should be prioritized for early-stage response analysis and future risk mitigation. The hazard maps produced by the READY project were only displayed in the central governmental building, not the barangay buildings. This storm surge extent map based on Typhoon Haiyan can be used as preliminary information and to improve Tanauan’ storm surge hazard map. Displaying the hazard maps in every barangay office may be an effective means to raise residents’ awareness of the natural disaster risk and enhance the community’s resilience, which is especially important due to global climate-change scientists’ warning that the same class of natural disaster will occur frequently in the future [23] [24].
ACKNOWLEDGMENTS: This study was funded by a discretionary budget from the president of Tohoku University and the director of the International Research Institute of Disaster Science (IRIDeS), Tohoku University, and Tokio Marine & Nichido Fire Insurance Co., Ltd. We deeply thank the officers of the Planning Departments of the Municipality of Tanauan, Ms. Cecile Mae M. Ocado, Ms. Dayday M. De La Cruz and Mr. Jerome S. Fabre, who provided the geospatial data set and its attribute values.
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