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The Philippines are heavily impacted by tropical cyclones. This project aimed to determine where women and children in the Philippines are most vulnerable to cyclones.
Cyclone Threat in the Philippines
The Republic of the Philippines lies in the western Pacific Ocean and consists of more than 7,000 islands (Image A). The climate of the Philippines can be divided into two main seasons: the dry season (December to May) and the wet season (June to November). The wet season is when the country experiences the majority of its precipitation, due in part to the Southwest Monsoon, a seasonal reversal of the winds from the Indian Ocean transport atmospheric moisture northward over the region.
One of the greatest natural threats to the country is tropical cyclones, with almost half (48.8 percent) forming in the surrounding region between July and September, though the majority (53 percent) of landfalls occurs between October and December . According to the World Risk Index of 2012, the Philippines ranks third among 173 countries most vulnerable to disaster risk and natural hazards . In the Philippines, cyclones are common natural hazards with extensive consequences, depleting government funds and exacerbating poverty throughout the nation.
Disaster Response Planning
The Philippines Department of Science and Technology launched the Nationwide Operational Assessment of Hazards (NOAH) in 2012 as part of President Corazon Aquino’s goal to implement a disaster prevention and mitigation program. NOAH’s mission is to provide three key support tools throughout the country, including the provision of disaster science research and development. Since its launch, project NOAH has installed more than 500 automated weather stations (AWS) and rain gauges (ARG). Project NOAH ensured location-specific weather forecasts seven days in advance, as opposed to previous forecasts that were given only three days in advance. Furthermore, the government has implemented a master plan in and around the city of Manila, in hopes of providing a flood management plan through the year 2035.
Despite these efforts, hazard management does not reach all vulnerable populations across the country and there remains a need to assess the specific vulnerability of women to gender-based violence (GBV). GBV refers to human trafficking, domestic violence, sexual violence, abuse, and child/early marriage. A report by the International Federation of Red Cross and Red Crescent Societies looking at nine different countries recently impacted by a disaster suggest that ÛÏÛ_overall, it seems that disasters tend to increase the risk of GBV and that new forms of GBV can emerge in their aftermath .Û To address this issue, this DEVELOP project partnered with the United Nations Office for the Coordination of Humanitarian Affairs (UN-OCHA) to use additional datasets including tropical cyclone tracks, and population statistics that focus on gender vulnerability to study the characteristics and effects of cyclones since 1982.
The aim of this project was to contribute to UN-OCHA an understanding of where the most vulnerable populations are located in conjunction with where the most devastating cyclones have historically made landfall, in order to enhance prevention and preparation plans for future disaster risk. The team created cyclone vulnerability maps for UN-OCHA, who is responsible for ensuring an organized response to assist vulnerable populations before, during, and after a natural disaster in the Philippines. These vulnerability maps were created with a special focus on low-income populations that remain sensitive to gender-based issues. They will be integrated into UN-OCHA’s current preparation and mitigation disaster procedures to help locate areas most prone to dangerous cyclone activity and assess the socioeconomic vulnerability of those locations.
To assess tropical cyclone frequency and threat, this project used the International Best Track Archive for Climate Stewardship (IBTrACS) . This dataset includes 6-hourly best tracks from multiple agencies, including the United States military’s Joint Typhoon Warning Center (JTWC), the Japanese Meteorological Agency, the Shanghai Typhoon Institute of the Chinese Meteorological Administration, and the Hong Kong Observatory. Even though these four agencies focus on the western Pacific, they often produce conflicting estimates of storm location and intensity  . For simplicity, the project used data only from JTWC since this is the most widely used agency in the region.
The project also incorporated data from the Satellite Radar Topography Mission (SRTM), gathered at a 90-meter resolution, to incorporate slope into the calculations for landslide susceptibility. Demographic data were provided by the Humanitarian Data Exchange and combined with data from the 2015 Philippines Census. Variables highlighted in this study included the percentage of single mother households, elderly females, female child-led households, disabled females, and access to resources such as stable housing, sanitary toilet facilities, and clean water.
A multivariate weighted approach was used to derive the final threats map. Quality controlled wind speed data were used to calculate the Accumulated Cyclone Energy (ACE, Bell et al. 2000), which can be used as a proxy for the destructive potential of cyclones over time by summing the squares of the maximum 6-hour wind speeds represented by each track segment (i.e., ACE = Vmax2). Using a spatial join in ArcMap 10.4.1, these ACE values were combined at the municipal-level to determine their study period total ACE. We combined SRTM slope data to consider areas more prone to landslides.
In addition to this natural assessment, we utilized municipal-level demographic data such as the number of elderly females and female child-led households. After normalizing these data, a weighting scheme preferential to the ACE and gender-based vulnerable households was applied to determine a particular municipality’s gender risk to tropical cyclones (Table 1). Descriptive statistics, including the number of storms and maximum wind speed of all cyclones in the study period, were calculated to identify regions most likely to be affected by cyclones based on past storms. We derived our destruction variable (ACE, topography, building materials, and proxy for population) weighting scheme from importance factors used by Netherlands Red Cross and our demographic variable weighting scheme from expert advice provided by UN-OCHA .
Table 2 shows cyclone track summary statistics, highlighting the dramatic number of tropical cyclones impacting the Philippines within the last few decades.
Of significant interest was the proportion of major tropical cyclones (37 percent) that affected the islands or an area within 100 km. The municipality with maximum ACE was the Calanasan region in north central Luzon. This north-south cyclone ACE pattern continues throughout the islands with few exceptions best explained by stronger storms passing through relatively quiet zones (e.g., Davao region in southeast Luzon).
These natural hazards were combined with demographic factors including poor households with single mothers, disabled or elderly females, weak walls and roofs, and unsafe drinking water.
Using an equal weighting scheme of destructive variables (including natural dangers like tropical cyclones and infrastructure vulnerabilities) and demographic variables, a final threat map was rendered to show overall gender vulnerability to natural hazards. Of particular note was the fact that while natural hazard vulnerability was greatest to the north on Luzon, the demographic vulnerability remained to the south on Mindanao. This lead to a uniformly spread ÛÏthreat indexÛ as both factors were combined. Project partners at the UN-OCHA will use this threat index to identify regions where women and children are at high risk during a tropical cyclone. Individual threat maps for demographic vulnerabilities and exposure vulnerabilities (derived from the destructive variables specified above) are used by the partners to advocate for proactive disaster relief resources based on either socioeconomic or exposure vulnerability respectively. A second project term will further analyze the impacts of tropical cyclones by incorporating the size and shape of storms in the tropical cyclone intensity climatology.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration. åÊ
This material is based upon work supported by NASA through contract NNL16AA05C and cooperative agreement NNX14AB60A.
 I. L. Corporal-Lodangco and L. M. Leslie, ÛÏClimatology of Philippine tropical cyclone activity: 1945-2011: PHILIPPINE TROPICAL CYCLONE CLIMATOLOGY,Û Int. J. Climatol., Nov. 2016.
 ÛÏDisaster Preparedness | GOVPH,Û Official Gazette of the Republic of the Philippines. [Online]. Available: http://www.gov.ph/aquino-administration/disaster-preparedness/. [Accessed: 20-Apr-2017].
 ÛÏUnseen, unheard: Gender-based violence in disasters,Û International Federation of Red Cross and Red Crescent Societies, Geneva, Nov. 2015.
 K. R. Knapp and M. C. Kruk, ÛÏQuantifying Interagency Differences in Tropical Cyclone Best-Track Wind Speed Estimates,Û Mon. Weather Rev., vol. 138, no. 4, pp. 1459ÛÒ1473, Apr. 2010.
 C. J. Schreck, K. R. Knapp, and J. P. Kossin, ÛÏThe Impact of Best Track Discrepancies on Global Tropical Cyclone Climatologies using IBTrACS,Û Mon. Weather Rev., vol. 142, no. 10, pp. 3881ÛÒ3899, Oct. 2014.
 ÛÏA priority index for humanitarian aid after a typhoon,Û 510.global, 09-Nov-2016.
Daniel T. Martin is a recent graduate from Appalachian State University working with DEVELOP at NCEI as an independent research consultant on the Philippines Disasters project. åÊ
Jessica Vermillion is a recent graduate from the University of South Carolina working with DEVELOP at NCEI as an independent research consultant on the Philippines Disasters project. åÊ
Allison Daniel is a recent graduate from the University of Alabama Huntsville working with DEVELOP at NCEI as an independent research consultant on the Philippines Disasters project.
Kelly Meehan is a recent graduate from Duke University working with DEVELOP at NCEI as an independent research consultant on the Philippines Disasters project.