Spatial vulnerability assessment of climate-related disasters in the Rebana Metropolitan Coastal Area, West Java Province

Human activities have become the main significant factor of the occurrence of climate change. Because of this phenomenon, the negative impacts of climate change influence human life itself, especially for the people who live in coastal area. One part of the Rebana Metropolitan Area in West Java Province is the coastal area consisting of Indramayu, Subang, and Cirebon regencies, which is closely related to climate-related disasters issues, such as coastal flooding and sea-level rise. To adapt the negative impacts of climate change, the local decision-makers should know the vulnerability to climate-related disasters. Therefore, the vulnerability assessment of climate-related disasters should be conducted. The spatial assessment was applied in this study to give a deeper perspective on the spatial vulnerability index. This study used georeferenced statistical data of three aspects (physical, geological, and socio-economical). These data then were overlaid with the support of the Geographical Information System (GIS) and eventually produced the vulnerability index for each zone. Based on the result, the Rebana Metropolitan Coastal Area has high vulnerability indexes (9 of 16 districts in these three coastal areas are very vulnerable). Two reasons have been identified. First, the intensity of rainfall and sea-level rise index that occurs annually in Indramayu and Subang is very high. Second, at the same time, these regencies have many vital infrastructures that make the massive potential of losses when climate-related disasters happen in the future. For the Cirebon case, the lack of supportive socio-economy situation in the coastal area has become the main factor for its vulnerability index. Based on these findings, the decision-makers could create different approaches to improve the resilience of each area. In Indramayu and Subang cases, their resilience could be strategically improved by strengthening their physical aspects, especially by ensuring the government protects their vital infrastructures. Meanwhile, for the Cirebon case, the government could be more concerned with its population density and income per capita for each district so that more people could avoid the coastal disaster directly and push their livelihood up in the more uncertain environment.


Introduction
One thing for certain is that human activities have been inducing climate change around the world, particularly in coastal areas (Nicholls, Wong, Burkett, Woodroffe, & Hay, 2008).The growth of people who reside in coastal cities has become a major issue over the last decades, leading to the creation of numerous megacities in world coastal regions (RJ, 1995).Because of this growth, the number of IOP Publishing doi:10.1088/1755-1315/1318/1/012008 2 demands in coastal natural resources and infrastructures has grown significantly (Sterr, Klein, & Reese, 2000) and consequently emitted substantial number of heat-trapping gases to the atmosphere (Glick, Stein, Edelson, & editors, 2011).Therefore, the constant-growing of the gases on the atmosphere make the heat could not leave the earth and slowly make the rise in the global average temperature, start from less than 1 o C to the 2 o C which would be probably happening in the near future if there is no significant intervention towards gas emissions (T.G. & Watson, 2016).The rise of temperature has induced climate change with notable indicators that have occurred over five decades (Foden, et al, 2018).
The coastal environment has been heavily inflicted by climate change impacts.Because of increased temperature, there are several changes in coastal ecological systems such as the occurrence of storm surge (Foden, et al, 2018) and sea level rise (Nicholls, Wong, Burkett, Woodroffe, & Hay, 2008).There are also collateral damages after the occurrence of extreme weather and sea level rise, for instance like the extinction of less-adaptive species because the destroyed coastal and marine habitat (Razgour, et al, 2019), coastal erosion, saltwater intrusion into coastal aquifers, declined wetlands habitat, and sediment deficits (Nicholls, Wong, Burkett, Woodroffe, & Hay, 2008).Moreover, not only giving the negative impact to the environment aspect, but climate change also gives a limitation for economic growth, especially when it comes to the coastal tourism who are highly dependent to the coastal nature as its main attraction (Moreno & Becken, 2009).
Because of the impact of climate change has been increasing overtime, many stakeholders are starting to give their attention to this issue.They have been trying to understand the science behind coastal climate change and creating many strategies to tackle the problem (Fussel & Klein, 2006).The first attempt they have tried to conduct was greenhouse gas emissions reduction (Glick, Stein, Edelson, & editors, 2011).However, even though the effort to reduce the gas emissions has achieved the best scenario (where almost all of gases would be significantly removed in 100 years), some of climate change's side effect would be still happened in the future, especially when it related to sea level rise and the people who are exposed to it (Climate Change Interactive & MIT Sloan Sustainability Initiative, 2022).For this inevitable reason, the stakeholders believe that there should be another approach to complement the effort in gas emissions reduction and this second approach is called adaptation management (Glick, Stein, Edelson, & editors, 2011).The principle is simple, instead solely focusing all the effort the reduce the gases, the stakeholders also must prepare the system so that it could cope with the climate change (Intergovernmental Panel on Climate Change (IPCC), 2007d).
The first step of adaptation management in coastal areas is trying to understand the vulnerability of the coastal objects or the systems (Parry, et al, 2007).Vulnerability itself could be defined as the extent to which a species, habitat, or systems is prone to harm from climate change impacts (Schneider, et al, 2007).By knowing the vulnerability index of a certain zone in coastal area, the policymaker could create strategies to make it less vulnerable/safer and achieve sustainable future (Patt, Klein, & Vega-Leinert, 2005).However, the knowledge about the degree of vulnerability in certain coastal areas is limited.For this reason, this paper has a purpose to conduct the vulnerability assessment in coastal area with the study case in the shoreline of Rebana Metropolitan Area, West Java Province, Indonesia.

Literature Review and Variable Formulation
Concepts, indices, and indicators of vulnerability can be defined differently depending on unique characteristics.In general, vulnerability is the degree to which a system is susceptible to, or unable to cope with, the adverse effects of climate change, including climate variability and extremes (Kang et al, 2018).The IPCC further defines vulnerability which is a function of the character, magnitude, and rate of climate change and the variation to which a system is exposed, its sensitivity, and its adaptive capacity (IPCC, 2001 in Kang et al, 2018).Furthermore, Turner (2003) explains that vulnerability is the extent to which a system, subsystem, or system component tends to experience losses due to exposure to danger, either disturbance or pressure.Therefore, it can be said that in general, vulnerability is how a system can deal with disasters or disturbances, which in the context of this research is climate change in coastal areas.So, it can be said that the assessment of disaster vulnerability in coastal areas is to assess the level of vulnerability of coastal areas to adverse effects caused by exposure to marine phenomena where the assessment is carried out to evaluate exposure, which is an external strength, sensitivity, which is an adverse effect caused by exposure, and adaptive capacity, which is a response to exposure or reduced sensitivity (Kang et al, 2018).
Furthermore, conducting a vulnerability analysis of a narrow coastal area implies a level of potential change that can be sustained by several coastal segments due to the presence or impact of different natural influences determined by the parameters considered (Ružic´ et al, 2019).Vulnerability analysis can be carried out at the appropriate spatial or temporal scale for the problem in question (Turner et al, 2003).Strong variations in vulnerability assessments can be by location or even to hazards created by global-scale processes and phenomena.The basic components of the vulnerability framework consist of: (i) linkages to the broader human and biophysical (environmental) conditions and processes operating in the combined system concerned; (ii) disturbances and stressors/stress arising from these conditions and processes; and (iii) the studied human-environmental systems in which vulnerabilities exist, including exposures and responses (Turner et al, 2003).
Several other variables that can be used to calculate the vulnerability assessment of coastal areas can be classified into three components of vulnerability.These components are geological vulnerability  2018) also said that in assessing the vulnerability of coastal areas it can be seen from the Coastal Exposure Index (CEI), Coastal Sensitivity Index (CSI), Coastal Adaptation Index (CAI), Coastal Disaster Impact Index (CDII), and Disaster Vulnerability Index.Coastal (CDVI).Mullick et al (2019) also describes three sub-indices in the vulnerability assessment process which include the coastal characteristic vulnerability sub-index, coastal pressure vulnerability sub-index, and socioeconomic vulnerability sub-index.Furthermore, regarding the socioeconomic aspect, Drestalita et al (2021) explained that to measure the level of socioeconomic vulnerability, there are two main aspects which are sociodemographic and economic indicator.Population density variables, women's population, children's population, elderly population, disability population, disaster mitigation system, and community institutions for indicators can be used to measure the level of sociodemographic vulnerability.As for the economic indicators used low-income people, the dominance of the employment sector, and the availability of economic facilities.These two indicators are then analyzed to obtain the overall composite vulnerability level.
From the explanation and the results of the literature review above, it can be concluded that in general the variables used to calculate the coastal vulnerability assessment are classified into three components of vulnerability: geological vulnerability, physical vulnerability, and socioeconomic vulnerability.The three components can then be accumulated into a total vulnerability level as shown in the figure below where Coastal Vulnerability Index (CVI) = Geological Index (IG) + Physical Index (IF) + Socioeconomic Index (IS). 4

Methodology
In this study, a mixed-methods approach was used, namely quantitative and qualitative approaches as a framework or guide in the process of collecting and analyzing data with not only a quantitative evidence perspective, but also an element of qualitative exploration (Creswell & Clark, 2007 and Teddie & Tashakkori, 2010).In this vulnerability assessment, a qualitative approach will be used to explore the dimensions, indicators, and weights of vulnerability to climate change and will also be used to explore vulnerability reduction strategies on the coast of Rebana Metropolitan Area.The data used are primary data obtained from field observations and secondary data obtained from the Central Statistics Bureau, Village Potential Data, Geospatial Information Agency, and reports from other relevant sectoral agencies.
Data analysis methods used to process and present data and information are spatial analysis, which also supported with qualitative analysis.The spatial assessment was applied in this study to give a deeper perspective on the spatial vulnerability index.This study used georeferenced statistical data of three aspects (physical, geological, and socio-economical).These data then were overlaid with the support of the Geographical Information System (GIS) and eventually produced the vulnerability index for each zone.The data that was used in this research was then degenerated as district data.Based on the literature review and variables formulation, this research decides to use 3 variables which are physical vulnerability index, geological vulnerability index, and socioeconomic vulnerability index.The following table shows the variable used in each variable used for this research.The first step in the analysis is to calculate the level of vulnerability for each variable using overlay techniques (By, 2001).Then, the results of the vulnerability level in each variable, are accumulated to get the total vulnerability level which will also be classified.The analysis process is carried out entirely by using GIS software to see how the level of vulnerability spatially for each coastal area in Rebana Metropolitan Area.The results of this vulnerability level will also be explained through color gradations.The darker the color indicates the higher the level of vulnerability, and vice versa.The brighter the color, the lower the vulnerability of the area.

Physical Vulnerability
In measuring the physical vulnerability of a coastal area to climate change, this study used 3 main indicators, namely rainfall that occurred in the area, the percentage of sea level rise, and the number of vital objects in the area.From the analysis that has been carried out, the following results were obtained: Based on the results of the mapping analysis above, it can be seen that in the very high level of physical vulnerability, there are 4 districts namely Kandanghaur, Cantigi, Pasekan, Balongan, all of them are in Indramayu Regency.For a high level of vulnerability, there are Legonkulon (Subang Regency) and Sukra, Patrol, Losaran, and Indramayu (Indramayu Regency).Blanakan and Pusakanagara Districts (Subang Regency), Gunungjati, Mundu, Astanajapura, Pangenan (Cirebon Regency), and Lemahwungkuk District (Cirebon City) are in the medium category for the level of physical vulnerability.For the low physical vulnerability class, there are Juntinyuat, Karangampel, Krangkeng (Indramayu Regency) and Kapetakan District (Cirebon Regency).As for the very low class, there are Sukasari Regency (Subang Regency), Suranenggala Regency, Gebang, Losari (Cirebon Regency), and Kejaksan Regency (Cirebon City).From this, it can be concluded that the areas with the highest physical vulnerability are mostly located in Indramayu Regency.This is because there is agglomeration of vital objects in several districts as well as indications of dominant sea level rise in these areas.

Geological Vulnerability
To measure the geological vulnerability of coastal areas to climate change, in this study 2 main indicators were used, namely the slope and elevation of the area.From the analysis that has been carried out, the following results were obtained: Based on the results of the mapping analysis above, it can be seen that in the high geological vulnerability class there are 2 districts, namely Pangenan and Gebang Districts, both of which are in the Cirebon Regency.For the medium level of vulnerability, there are Sukra, Pasekan, Juntinyuat, Karangampel, and Krangkeng Districts, all those districts are located in the Indramayu Regency.As for the low class, there are all districts in the coastal area of Subang Regency; Patrol, Kandanghaur, Losarang, Cantigi, Indramayu, and Balongan (Indramayu Regency); Kapetakan, Suranenggala, Gunungjati, Mundu, Astanajapura, and Losari (Cirebon Regency), and all districts in the coastal area of Cirebon City.From this, it can be concluded that the areas with the highest geological vulnerability are mostly located in the southern part of the Cirebon Regency.This is because the altitude of the area is quite low and quite flat.

Socioeconomic Vulnerability
To measure the socioeconomic vulnerability of coastal areas to climate change, this study used 5 main indicators, namely population density, poverty, GRDP per capita, non-productive age, and the total of basic infrastructure.From the analysis that has been carried out, the following results were obtained: Based on the results of the mapping analysis above, it can be seen that in the very high socioeconomic vulnerability level there is one district, namely Suranenggala, which is in the Cirebon Regency.For the high level of vulnerability, there are Sukasari and Pusakanagara Districts (Subang Regency), Gunungjati, Mundu, Gebang, Kapetakan, and Pangenan Districts (Cirebon Regency), and Kejaksan District (Cirebon City).Blanakan and Legonkulon Districts (Subang Regency), Indramayu, Juntinyuat, and Krangkeng Districts (Indramayu Regency), Losari District (Cirebon Regency), and Lemahwungkuk District (Cirebon City) are in the middle level for the level of socioeconomic vulnerability.For low socioeconomic vulnerability level, there are Sukra, Patrol, Kandanghaur, Losarang, Balongan, and Karangampel Districts which are all located in Indramayu Regency.As for the very low level of vulnerability, there are Cantigi and Pasekan Districts (Indramayu Regency), and Astanajapura District (Cirebon Regency).From this, it can be concluded that the areas with high socioeconomic vulnerability are mostly located in Cirebon and Subang Regency.This is due to a high population density, a high distribution of non-productive age, agglomeration of basic infrastructure, a high number of poor people, and a lower GRDP per capita.

Cumulative Vulnerability
To measure the total vulnerability of coastal areas to climate change, it is done by calculating the total weight of each indicator which becomes the total vulnerability in an area.From the analysis that has been carried out, the following results were obtained: Based on the results of the mapping analysis above, it can be seen that the regions with the highest overall vulnerability are mostly located in Indramayu Regency.This is because the results of physical, geological, and socioeconomic vulnerabilities have a fairly high level to produce very high overall vulnerability results.The existence of vital objects in Indramayu Regency such as GITET and Pertamina Balongan which exacerbates the level of vulnerability of the area.

Findings and Discussion
Analysis of each vulnerability indicator has resulted in the level of vulnerability in each region based on the type of vulnerability studied.From the results obtained, it is shown that in general the vulnerability of coastal areas which are quite diverse is mostly dominated by moderate to very high levels of vulnerability.The level of vulnerability at a very high level is due to the distribution of vital objects in the area, rising sea levels in the form of coasts, geographical conditions of the region, to the economic conditions of the region.Locations with a high-very high level of vulnerability are mostly in the coastal areas of Indramayu Regency.This can happen because of the activity concentration in the coastal area as well as the connectivity between regions in the coastal area.

Figure 5. Cumulative Vulnerability
Furthermore, the level of vulnerability is not determined only by the indicators that have been formulated but is also caused by the quality of the coastal area itself, the existing condition of the coastal area, and the activities that take place in the coastal area.As on the coast of Subang Regency, there is the construction of the Patimban Port that located in Pusakanagara District where this port is a national strategy project in accordance with the Presidential Regulation of the Republic of Indonesia No. 47/2016 concerning the determination of the Patimban Port in Subang Regency, West Java Province.The construction of the Patimban Port itself has triggered other major activities such as higher logistics traffic, development of supporting infrastructure, and the construction of housing and office areas to support port activities has also been planned to be realized.Therefore, this makes the vulnerability in the coastal area of Subang Regency higher.
On the other hand, in the coastal area of Indramayu Regency, with a very high level of vulnerability, it is also caused by the presence of quite a lot of areas, especially the lower areas, especially in Patrol Regency and the intensity of activities in the coastal area which is also quite high.Activities in the coastal area of Indramayu Regency are quite diverse in the form of beach tourism, mangrove tourism, fishing boat ports, shipbuilding, fish auction sites, to industrial activities such as the oil and gas industry.With these activities, there are several multiplier effects that occur, such as at Tirtamaya Beach in Juntinyuat District and Karangsong Beach in Indramayu District, there is quite a lot of garbage piled up.Not only that, historically, the abrasion that occurred in the coastal area of Indramayu Regency was also quite large.Therefore, conservation activities are carried out for the conservation of mangrove forests, especially in the Karangsong Beach Area, where these activities were initially the result of cooperation and assistance carried out by Pertamina through CSR activities and had been on hiatus since the pandemic and then started operating again and were open to tourists.since September 2021.From this it shows that collaboration between the government, companies, and the community has been established but there is still a need for improvement for collaboration.
With a lower level of vulnerability than the coastal areas of Subang Regency and Indramayu Regency, the coastal areas of Cirebon Regency and Cirebon City are also center where the city center is in Cirebon City as National Activity Centers (locally known as PKN) which is stated in the National Government Regulation No. 26/2008 on The National Spatial Plan.It is also the core city of Ciayumajakuning dan Rebana developmental area which is supported also by the Cirebon Regency area.The dominance of activities that have more characteristics such as running and trading and services especially in the city of Cirebon.Not only that, but there is also a port that functions as a logistics port and coastal tourism.There are also local fishing activities.This activity is also quite developed in coastal areas.Meanwhile, in the coastal areas of Cirebon Regency, the dominance of activities is more likely to be fishing activities such as ponds and fish auction sites in the north and industrial activities are located in the southeastern region of Cirebon Regency.However, with a variety of activities and quite large, the level of vulnerability only in Cirebon City and Cirebon Regency is lower which is indicated by the few vital objects that exist and there are several in the southern region.
Furthermore, from the findings and discussions, it can be said that the level of vulnerability is only caused by the indicators that have been formulated, but also due to the intensity in coastal areas, the condition and quality of coastal areas, to traffic and connectivity in coastal areas that cause high activity intensity in the coastal area.However, this can begin to be tackled with the conservation of mangrove forests that have been carried out in several coastal areas as well as collaborations carried out by the government, companies, and the community as a form of adaptation and the most effective form of mitigation.

Findings and Discussion
Based on the results of the analysis that has been carried out, it can be concluded that from the indicators of physical vulnerability, most of the highest vulnerability occurs in coastal areas in Indramayu Regency.This is due to the rapid rise in sea level and the agglomeration of vital objects along the area.Of the 11 districts, 4 of them are in a very high physical vulnerability condition, 4 are high, and 3 are low.Then, from the geological vulnerability indicators, some of the areas fall into a low level of geological vulnerability.Only two districts are classified as high vulnerability, namely Pangenan and Gebang Districts, both of which are in the Cirebon Regency.Meanwhile, from socio-economic vulnerability indicators, Cirebon and Subang Regency are the most vulnerable areas.This is caused by a high population, a fairly high distribution of non-productive age, agglomeration of basic infrastructure for public services, a relatively high number of poor people, and a low GRDP per capita.There are 9 districts with high vulnerability status, namely 6 districts in Cirebon Regency (Suranenggala, Kapetakan, Gunungjati, Mundu, Pangenan, and Gebang), 2 districts in Subang Regency (Sukasari and Pusakanagara), and 1 district in Cirebon City (Kejaksan).If accumulated, the composite vulnerability level of high-very high status is in the districts located in Indramayu Regency.The existence of vital infrastructure has a significant impact on the Regency's composite vulnerability index.
By looking at the results that have been obtained, several recommendations are suggested to reduce the level of vulnerability of coastal areas to the impacts of climate change, which can be done by increasing community adaptation, especially for vulnerable communities by increasing community's welfare and understanding related to the impacts of climate change in coastal areas.A comprehensive disaster mitigation system is also needed as a form of prevention from the emergence of the impacts of climate change that occur.This strategy can be pursued by collaboration between the government, the community, and institutions in order to strengthen the regional adaptation system, especially in the coastal area of Indramayu Regency which has a fairly high level of total vulnerability than other regions.The implementation of this strategy also needs to be carried out in the coastal areas of Subang Regency, Cirebon Regency, and Cirebon City in order to strengthen the Rebana Metropolitan area.

Table 1 .
List of Analysis Variables and Indicator Number of Basic InfrastructureEach indicator represents each variable.All indicators are measured according to the existing conditions in each area.For further details, the table below shows the stipulation for each indicator.

Table 2 .
Level of Vulnerability Stipulation based on Variables.The denser the more vulnerable • The greater the percentage of the poor are vulnerable • The lower the GDP per capita, the more vulnerable • The higher the percentage of non-productive age (under 15 years and above 65 years) the more vulnerable • The more infrastructure the more vulnerable