Social Vulnerability Level Appraisal at Tidal Flood Areas

The Case of A Coastal Settlement in Indonesia

Abstract

Coastal areas play a vital role by providing some people with their source of livelihood. Coastal areas are vulnerable to the impacts of climate change, such as sea-level rise (SLR), which could damage infrastructure and threaten the socio-economic conditions of communities, thus making the regions vulnerable. Semarang City located in a coastal zone, and one of the coastal settlements in Semarang City experiencing the impacts of climate change is Tambak Lorok in North Semarang District. Adaptive capacity is needed for solutions to climate change vulnerability. This study aims to determine the level of vulnerability due to tidal flood disasters resulting from climate change in coastal settlements. In this initial stage, this study assesses the level of vulnerability and uses a quantitative approach. Through lessons learned by comparing the conditions of vulnerability in Bilu Village, Banjarmasin City, differences in capacity vulnerability were obtained. Tambak Lorok has a low level of social vulnerability, while Bilu Village has a medium level of vulnerability. Assessments related to social vulnerability are identified through individual and community capacity indicators measured at the household and community levels. Differences in the conditions of coastal areas and the impacts of climate change that occur affect the level of vulnerability of these areas.

Introduction

There is a growing concern for urban scholars that population growth has a significant contribution to the increased risk of coastal flooding. Wolff, Nikoletopoulos et al. (2020) even emphasised that uncontrolled urbanization in developing countries has become a new exposure that increases vulnerability. The interaction between humans and their environment is increasing due to global climate change. For example, the occurrence of sea-level rise (SLR) in some areas can cause a substantially increased flood risk (Bronstert, 2003). There is an urgent need to understand, both physically and economically, the relationship between humans and natural hazards as well as the suffering that humans experience (Mileti and Peek-Gottschlich, 2001). Hazard events and conditions are included in the risk level factors that contribute to social vulnerability in the locations where hazard events occur.

Coastal areas are very vulnerable to natural hazards (Kron, 2013), and this vulnerability will increase as a result of SLR caused by climate change and its related impacts, such as flooding, erosion, permanent inundation, and seawater intrusion (Nicholls and Cazenave, 2010). Therefore, people in coastal areas are required to adapt to changes and natural phenomena that occur (Faustino and Jr, 2009). Adaptive behaviours could be affected by internal awareness of disaster, risk communication mechanisms and the external environment (Hu, Pai et al., 2018). According to Tsai, Song et al. (2021), people who face environmental pressures will more likely to increase their awareness in building a strong community. Coastal communities can barely cope with the impacts of climate change such as tidal floods which require more adaptive livelihood systems (Rudiarto and Pamungkas, 2020).

These coastal conditions are causing surrounding residential areas to experience a deterioration in the quality of the environment, and as a result, they are becoming informal settlements. The term slum refers to when the conditions of informal settlements and human life are below standards (UN‐Habitat, 2004). To define informal settlements, several different criteria can be used, namely, spatial, physical, behavioural, and social factors. Additionally, there is an increased vulnerability of poor individuals to the disaster risk of flooding due to poor housing standards, and building materials and poor locations such as those near rivers can also increase the vulnerability of residents (Yuliastuti, Rahdriawan et al., 2016). Some impact of floods in coastal slums according to Owusu and Nursey-Bray (2018) are damage to fishing infrastructure, lack of clean water, contamination of freshwater which results in the spread of diseases (such as cholera), damage to houses, damage to wastewater disposal sites, psychological trauma, and increasing community vulnerability to violence/crime.

One solution to reduce the level of damage from natural disasters is to reduce social vulnerability, namely by intervening in policies and planning (Bui, Kawamura et al., 2018). Vulnerability is a person's relationship with the environment, cultural values, and the strengths and social institutions that support or oppose it (Comfort, Wisner et al., 1999; Cutter, 1996; Wisner, Blaikie et al., 2014). Social vulnerability in a community or society is a concept that refers to the social level, and it includes political and economic vulnerability (Wisner, Blaikie et al., 2014). Social vulnerability could also be a sign that social conditions also influence the loss of the area due to flood (Wang and Shaw, 2018).

The theoretical framework provided by the concept of vulnerability includes multidimensional disasters by combining several elements in various proportions, such as environmental, community, and cultural aspects (Comfort, Wisner et al., 1999; Cutter, 1996; Wisner, Blaikie et al., 2014). Social vulnerability is influenced by many factors, namely, geographical, community, organizational or institutional factors, as well as the individuals in households (Dwyer, Zoppou et al., 2004). Moreover, the level of vulnerability is determined by the response of the system and the capacity for adaptation. According to Adger and Vincent (2005), the ability to adapt is very local and is influenced by economic conditions, experience, and education. The subsequent research by Dintwa, Letamo et al. (2019) states that one of the factors that increases social vulnerability is a low level of education.

The interaction between people and their environment, as a social-ecological system, will form local capital that determines the level of vulnerability. People categorized as poor tend to be more vulnerable to natural disasters, because of their inability to face disasters and recover themselves from disasters that occur (Etinay, Egbu et al., 2018). In developing countries, population growth, poverty, and the marginalization of some groups in society are the most easily understood hazards of social vulnerability. People who live in substandard housing tend to have limited access when a disaster occurs due to the lack of physicality in their environment.

Semarang City and Banjarmasin City are experiencing such conditions, primarily those related to the dangers of floods, which still happen in some area of informal housing areas in the northern parts of these cities. The threat of tidal floods in the Semarang coastal settlement also impacts individuals, communities, and households simultaneously (Marfai, King et al., 2008). Community characteristics in the form of community capacity, which is how communities anticipate recovering from the impacts of hazards, provide definitions of vulnerability that are suitable for this research. The level of vulnerability can be observed based on the level of resilience when floods occur (Isa, Sugiyanto et al., 2018). The life of people vulnerable to hazards can be threatened; in addition, their livelihoods, economic productivity, infrastructure, and natural resources will be threatened.

To deal with the risk of community vulnerability, an adaptation response is needed. Government and local institutions have the same role in dealing with responses to hazards and managing vulnerability. New hazard research practices have been reflected in public policies related to hazard management. Some studies have made significant contributions, and the current research continues in this vein, focusing on mitigation, preparedness, response, and recovery (Jones and Preston, 2011). However, most of the previous research focuses more on the vulnerability assessment rather than the community coping with the disaster. In fact, governing social vulnerability plays important role in the form of social resilience. Recent study by Usamah, Handmer et al. (2014) concluded that social capital could help vulnerable people be resilient in the Philippines. It means that social governing in the social capital could be understood in the future disaster management.

Based on the statements above, the research question is follows: "What is the capacity of communities for dealing with vulnerability, and how do people overcome shocks that occur in the form of floods?" Therefore, this article aims determine the level of vulnerability due to tidal flood disasters resulting from climate change in coastal settlements. This article compared the vulnerability characteristic in two groups (Tambak Lorok & Bilu Village) and investigated how social governing take place. The following section will explain the research methodology. The finding and discussion will take place in the end of article.

Methodology

Case Study

Administratively, Tambak Lorok area located in Tanjung Mas Village in several part of area called Rukun Warga (RW), which are RW XII to RW XVI area, North Semarang Sub-district, Semarang City, and it has an area of 46.8 ha. Located in north-eastern Tanjung Mas Village, the Tambak Lorok area is directly adjacent to the sea and Kemijen Village. The Tambak Lorok area consists of 5 parts of RW Tanjung Mas Village, namely, RW XII, RW XIII, RW XIV, RW XV, and RW XVI (see Figure 1).

Figure 1. Tambak Lorok Map

The topographic conditions in Tambak Lorok area include sloping, with a slope of 0-2° because the area is located in a coastal area; thus, it can avoid landslides but is prone to tidal floods. Tidal flood water often hits the Tambak Lorok area because it is at an altitude of 0.5-1 m above sea level. The rainfall in Tambak Lorok, which is 27.7-34.8 mm/year, falls under the medium to high categories. Additionally, this area is affected by the tides of Java Sea water because of its location between the mouths of two large rivers. The Tambak Lorok area is also prone to land subsidence, which can reach 9-10 cm/year. To respond to flood disasters, the Tambak Lorok area is included in the disaster area of the North Semarang Sub-district. The area of the Tambak Lorok area is 46.8 ha, and the land use is divided into settlements (32.4 ha), ponds (11.2 ha), and the port (3.2 ha).

Tambak Lorok has enormous potential, especially in the production of marine products. In the village, there is a fish market where many people from outside Tambak Lorok come to buy seafood. In 2009, the fish market had a production amount of 74,037 kg, with a production value of IDR 198,183,700.00; then, in 2010, there was an increase in the production value to IDR 271,668,500.00, and the production amount was 50,052 kg (Fisheries Agency Semarang, 2011).

In 2015, the Tambak Lorok area had 1,551 households, and the population was 9,503 people. The male population amounted to 4,373 people, and there were 5,130 female residents. At present, the occupations of Tambak Lorok residents can be grouped into fishers and non-fishers. Fishers are categorized into 3 categories: fishing fishers, fisher workers, and fisher boat rental service providers. Based on data from the fisheries agency of Semarang City, in 2014, more than 50% of the total number of fishers in Semarang City, i.e., 897 people, were in the Tambak Lorok area. The non-fisher group consists of workers, employees, and traders.

Conceptual Framework

Vulnerability cannot be considered to be adequately demonstrated by a conceptual framework consisting of multiple structures without copying and management capacity. Wisner, Blaikie et al. (2014) define vulnerability in terms of the characteristics of people or groups related to the ability to anticipate, overcome, fight, and recover from the effects of natural hazards. The framework of local communities and institutions channels the aspirations of citizens and mobilizes residents to form a proposal based on real needs (Yuliastuti and Widiastomo, 2015). Bohle, Downing et al. (1994) define vulnerability as a multidimensional social space determined by the ability of determination, people's institutions, the economy, and the politics in a particular time and place. Vulnerability implies a risk for people in the form of internal and external dimensions (Brklacich and Bohle, 2006).

Moreover, a social network's ability to cope with the exposure has been understood as human cooperation (Rand, Arbesman et al., 2011). It enables social culture to develop self-organization ability in technology, social movement, and individual response. Therefore, personal support and community support for disaster are the feedback form for the self-organization in emergency response. Briefly, the social movement in response to the disaster can be viewed as an embryo of the downstream approach to be resilient. Therefore, it is better to consider this approach complements the upstream system from the government.

Figure 2. Conceptual Framework

The creation of tools for analysing causes and solutions in vulnerability research is the next step that must be performed (Birkmann, 2006). Moreover, to explain and deal with the complex interactions among engineering, natural systems, and social systems, it is necessary to focus on analytic (empirical models) or social dynamics (Cutter, Emrich et al., 2009). Conceptual framework could be seen at Figure 2.

Research Design

The total number of respondents in this study was 50 people each for Tambak Lorok and Bilu Village. The questionnaire is divided into open- ended and closed-ended questions. Open-ended questions are necessary to directly obtain a respondent’s view of a problem. Additionally, interviews with the key informants in the study area are necessary to determine vulnerability at the household and community levels. The average interview at the household level lasted 45 minutes.

In the interviews, the key informants who were needed were religious leaders, community heads, and traders. In addition, interviews were conducted with people involved in local decision making, communities engaged in local non-governmental organizations, and flood management in the city of Semarang.

To understand the form of interaction based on the community at the household and environmental levels and to improve the sense of place, observation of community activities is necessary. Among them, this study examines some indicators related to households and the local environment. These indicators serve as benchmarks for observing people’s sense of place and communication. Finally, comparisons are made between two locations, namely, Tambak Lorok and Bilu Village.

The selection of communities in the slums in this study is based on the fact that people who are continuously affected by floods incur a risk of suffering. Furthermore, it is based on the frequent involvement of the community in mitigation actions. The focus of this research is the community, which is analysed in a more subjective manner because if the community is taken in a larger sense, then there will also be a variety of management strategies.

Tambak Lorok is one of the fishing villages located on the coastline of the Java Sea. The village is situated just on the outskirts of Semarang City and directly adjacent to the waters of the Java Sea. This area is affected by the tides of the Java Sea, which often cause tidal floods. Meanwhile, Bilu Village is a slum area located right on the Martapura River in Banjarmasin City. As a result of this area’s being situated on the banks of the river, it has become vulnerable to floods. The similarity of this condition underlies the selection of Bilu Village as a study area to observe the level of vulnerability in a location other than Tambak Lorok.

Other elements that are also considered in this study are the level of flooding in the environment, the initiatives and activities that the community carries out with regard to vulnerability, and the type of economic activity. When applying these criteria, the characteristics of society will provide much diversity. The main objective of this research is to determine the level of social vulnerability to flooding faced by communities by examining the contextual differences viewed from several perspectives, not to compare the perspective of the two communities.

Analysis Method

The methods used to analyse the results of the information obtained from the questionnaires, interviews, and observations are qualitative and quantitative. The dimensions of exposure, implications, resource capacity, and response can be explored based on social vulnerability. The proportion of exposure to flooding can be examined based on settlement factors, slums, demographic characteristics, and infrastructure status. However, the dimension of resource capacity has been studied based on institutional political and economic factors, awareness and knowledge, and the role of social capital. In this research, the case study area adopted refers to the local Rukun Warga (RW) institution.

To obtain people's opinions about constraints and problems as well as desired expectations, it is necessary to conduct comparative analysis between management capacity and exposure at the household level in various slum communities. In addition to the results of the information from observations, surveys and questionnaires, ethnographic methods are applied to evaluate and understand resources, lifestyles, people's attitudes towards vulnerability in slums, the risk of recurrence of floods, and community perceptions regarding the responsibility for and causes of loss. The comparative analysis of Tambak Lorok and Bilu Village will be discussed at the end of this paper.

Analysis of the level of social vulnerability was carried out using weighting analysis, which consists of assigning a weight to each predetermined indicator. The determination of this weight is adjusted in regard to the criteria for the community’s level of social vulnerability. To obtain the level of social vulnerability, the variables needed are individual capabilities, households, local institutions, facilities and infrastructure, and safety (Tables 1 to 5).

Table 1. Individual Capability Weighting Criteria

Variable	Indicator	Weight Value
		High Vulnerability (3)	Medium Vulnerability (2)	Low Vulnerability (1)
Individual Capabilities	Education	The head of household is an S1/D3 graduate and has better ability and knowledge; thus, the expectancy to move is higher	The head of household is a junior/senior high school graduate and has sufficient capacity and expertise to move	The head of household who is an elementary school graduate or has had no schooling and has low ability and knowledge; thus, there is no expectancy or courage to move
	Mode of Transportation	The head of household uses public transportation/ a bus/a motorcycle/a taxi to travel to work	The head of household uses a motorcycle to travel to work	The head of household uses the mode of transportation of walking/bicycling
	Amount of Income	Does not obtain income when tidal floods occur	The amount of income decreases when tidal floods occur	The amount of income does not decrease when there are tidal floods

Source: Kelly and Adger (2000); Adger and Vincent (2005); Social Vulnerability Index (2020)

Table 2. Household Weighting Criteria

Variable	Indicator	Weight Value
		High Vulnerability (3)	Medium Vulnerability (2)	Low Vulnerability (1)
Household	House Status	Houses with the status of lease or contract rights	Homes with building usufruct status	Houses with property rights
	Length of Stay	Families with a range of stay under two years	Families with a range of stay of 2-8 years	Families with more extended stays of more than eight years
	Place of Origin	Families that are not native	-	Families that are native
	Expectancy to Move	Families that want to move	-	Families that do not want to move

Source: Social Vulnerability Index (2020)

Table 3. Local Institution Weighting Criteria

Variable	Indicator	Weight Value
		High Vulnerability (3)	Medium Vulnerability (2)	Low Vulnerability (1)
Local Institution	Involved in Local Institutions	The community is not involved in local institutions	-	The community is involved in local institutions
	Local Institutional Performance	Local institutional performance is not optimal	Local institutional performance is not maximal	Optimal local institutional performance
	Involved in Community Service	Never participates in community service	Sometimes participates in community service	Always participates in community service
	The Intensity of Community Service	Never	Sometimes	Once a month or less
	Involved in Maintaining Facilities	There are no residents involved in maintaining public facilities	Only part of the community is involved in maintaining public facilities	All community members are involved in maintaining public facilities

Source: Bohle, Downing et al. (1994)

Table 4. Facilities and Infrastructure Weighting Criteria

Variable	Indicator	Weight Value
		High Vulnerability (3)	Medium Vulnerability (2)	Low Vulnerability (1)
Facilities and Infrastructure	Distance from Home to Work Place	Distance> 5 km	Distance of 2-5 km	Distance <2 km
	Distance from Home to Market	Distance> 5 km	Distance of 2-5 km	Distance <2 km
	Distance from Home to Educational Facilities	Distance> 5 km	Distance of 2-5 km	Distance <2 km
	Distance from Home to Health Facilities	Distance> 5 km	Distance of 2-5 km	Distance <2 km
	Environmental Infrastructure Conditions	Unpaved roads, broken, often flooded with tidal floods	Perforated roads and flooded by tidal floods	Roads in good condition, not damaged, not flooded by tidal floods

Source: Owusu and Nursey-Bray (2018)

Table 5. Safety Weighting Criteria

Variable	Indicator	Weight Value
		High Vulnerability (3)	Medium Vulnerability (2)	Low Vulnerability (1)
Safety	Sick Because of Tidal Floods	Family members are sick and receive treatment > 5 times/month	Family members are sick and receive treatment 2-5 times/month	Family members are sick but do not seek treatment
	Security regarding Criminal Acts	Criminal acts often occur	Criminal acts have occurred several times	There has never been a crime
	Tidal Floods	The surrounding environment often has tidal flooding	The surrounding environment has had tidal flooding several times	The surrounding environment has never had a tidal flood

Source: Owusu and Nursey-Bray (2018)

The average weight value was analysed by calculating the weight in each data point. This value was calculated to determine the level of vulnerability that occurs for each indicator in the variables that affect the level of social vulnerability in Tambak Lorok and Bilu Village. The calculation of the average weight value is performed as follows:

Average Weight Value = $\frac{{\text{(∑R x High Weight) + (∑R x Medium Weight) + (∑R x Low Weight)}}_{}}{{\text{High Weight + Medium Weight + Low Weight}}_{}}$ ............(1)

Information:

∑R = Number of Respondents

High weight = High weight determined is 3; the level of vulnerability is higher

Medium weight = Medium weight determined is 2; the level of a vulnerability is medium

Low weight = Low weight determined is 1; the level of a vulnerability is lower

After calculating the average weight value of each indicator, it is necessary to group the categories of vulnerability. The number of classes needed is divided into three, which are categorized as high vulnerability, medium vulnerability, and low vulnerability. The interval formula is as follows:

  

The total number of respondents in this study was 50 people each for Tambak Lorok and Bilu Village. From the formula above, we obtain the average weight value for each indicator for Tambak Lorok, Semarang City, and Bilu Village, Banjarmasin City, as follows:

Low vulnerability level = 8.3 – 30.5

Medium vulnerability level = 30.6 – 52.8

High vulnerability level = 52.9 – 75.0

Results

An interesting finding from this research is that most people living in coastal flood areas accept tidal inundation. From the deep interview, we concluded that there is place attachment. They feel that the place is land of their bird. They have subjective memory to that place. This finding support previous research by Usamah, Handmer et al. (2014) which concluded that vulnerable people can be resilience in Phillipines. The social relations within the community through local institutions make residents socialize and feel that they are not alone in facing tidal flood disasters. A similar feeling of facing disasters forces residents to share the risk and make connections between them. This is also support Rand, Arbesman et al. (2011) which investigated the role of dynamic social network.

Moreover, home elevation activities are a common way in which Tambak Lorok community members make connections; thus, residents feel that this activity is enough to allow them to survive when a tidal flood comes. They tend not to question the costs they incur each time they raise a house, and they maintain the land where they live, which is one of their assets. Low levels of education indirectly influence their decision making. In addition, the ease of access to health and education facilities is one reason why people in Tambak Lorok have low social vulnerability. The reason is that they feel that they have enough with what they have been given due to being born in a place where people can have a livelihood as fishers; thus, they do not know any choice of occupation other than that of becoming fishers.

Statistically, the average final weight value of Tambak Lorok is 25.6, which falls into the low vulnerability category. This result is based on the weighting carried out for each indicator. Some aspects reinforce the social viability of the Tambak Lorok community; thus, the Tambak Lorok community has a low level of social vulnerability. This low level of vulnerability indicates that the social bond and cohesion of community members with their place of residence are strong enough to be a reason for community members to “accept” the existence of tidal floods in their environment. With the average ability of people with a low level of education, the modest housing conditions, and the tidal flood conditions, the community is in a condition of low vulnerability. This result is due to the level of involvement in local community institutions and the infrastructure conditions of Tambak Lorok’s environment, which is improving, making the Tambak Lorok community able to adapt to the dangers of tidal floods.

The average final weight value of Bilu Village is 31.9, which falls into the category of medium vulnerability. This result is based on the weighting carried out for each indicator. Some aspects reinforce the social viability of the Bilu Village community so that the Bilu Village community has a medium level of social vulnerability. The fact that the weight value belongs to the medium category indicates that the level of social ties and cohesion of residents in Bilu Village with their place of residence are not yet strong enough to be a reason for community members to understand the conditions of their environment.

The lives of people of Bilu Village, who are close to the river, force them to be able to adapt to the environment. Moreover, the people in Bilu Village are dominated by natives because they have been living in that location for generations. However, even though they have been living there from one generation to the next, there are still some residents who do not have rights to the land that they currently occupy. This situation will make the community vulnerable to relocation from this location because there is no guarantee for the land that community members currently occupy.

The lack of involvement in and intensity of community service activities can also influence social vulnerability within the Bilu Village community. The conditions for the social relations of the community are worse because of the lack of a sense of interaction and concern for the environment among fellow citizens. Some facilities such as education, health, and trade facilities in the form of markets that are close to settlements make it easier for people to reach them and make it easier for people to meet their daily needs. This convenience is an important aspect of why people want to remain in Bilu Village.

Table 6. Comparison of the Levels of Social Vulnerability

Variable	Average Weight Value
	Tambak Lorok	Bilu Village
Individual Capabilities	37.7	44.3
Households	32.4	36.9
Local Institutions	20.8	33.7
Facilities and Infrastructure	10.6	11.6
Safety	26.4	33.3
Average	25.6	31.9
Category	Low Vulnerability	Medium Vulnerability

The results of the calculation for the value of social vulnerability in the two research locations (Tambak Lorok and Bilu Village) have different final values. Based on the table below (Table 6), Tambak Lorok has a final vulnerability value that is included in the low category, with a final value of 25.6, while Bilu Village has a vulnerability value of 31.9, which is included in the category of medium vulnerability.

Discussion

Based on comparative analysis, the level of vulnerability of Tambak Lorok is in the low category, while that of Bilu Village is in the medium category. The strength of family ties and the sense of belonging to the environment make people in Tambak Lorok tend to be more comfortable with the land of their birth, which is also the place of residence for the Tambak Lorok community and many other migrants. In addition, the reach of facilities and infrastructure is adequate; thus, it is also a reason for the strong ties between community members and the environment in which they live. Of course, it is also accompanied by a low level of public education. Therefore, community members feel that there is not enough capital to start a new life outside Tambak Lorok; thus, they have tended to accept the conditions in their area.

People who face environmental pressures will more likely to increase their awareness in building a strong community (Tsai, Song et al., 2021). Various community activities in Tambak Lorok related to local community RW institutions are still taking place effectively, and there is still community participation in such activities. An activity consists of a place where people gather and socialize; thus, it creates a sense of cohesion in the face of the tidal flood disasters that often occur. This aspect is one of the differences in social vulnerability between Tambak Lorok and Bilu Village.

Social vulnerability in Bilu Village belongs to the medium category due to the low level of social activities among the people of Bilu Village. The social cohesion in Bilu Village is not good enough and the land occupied by people in Bilu Village is not their private property. Therefore, when tidal floods become a problem that continuously occurs in Bilu Village, the community can only surrender if evictions are carried out at any time. In contrast, in Tambak Lorok, people tend not to move because the houses they occupy are based on their property rights; thus, they defend the land that is their property.

Additionally, the educational level of residents in Bilu Village tends to be better because most people are junior high school graduates, while the majority of people in Tambak Lorok have only the lowest level of education, i.e., an elementary school level, and some to not even have any education. This condition against Dintwa, Letamo et al. (2019) opinion that states one of the factors that increases social vulnerability is a low level of education. Apparently, lower education does not increase social vulnerability if it is balanced with high social cohesion.

Individual capabilities have a high value because the weighting for the variable of individual capabilities is the highest. The reason is that the abilities that individuals have, in terms of the lowest level of education and changes in income when tidal floods occur, very directly influence the social vulnerability faced. Additionally, the value of the individual ability to represent the community is related to vulnerability when the area is affected by tidal flood disasters.

Hence, to the extent that the variables above have a role in a social vulnerability in the community, they also have an impact on community members’ decision to survive in the midst of a location that is prone to tidal flood disasters or, in contrast, their choose to move and start a new life in another region. Therefore, social aspects are essential because they can change and have a direct impact on people's lives.

The differences between Bilu Village and Tambak Lorok are due to difference in the quality of education, the type of work, the participation of community members in maintaining the environment, community members’ concern for the housing environment, and the role of the city government. Compared to Bilu Village, all of these factors will lead to low vulnerability for Tambak Lorok because the indicator values above for Tambak Lorok are better than those for Bilu Village. This result is consistent with Adger and Vincent (2005) view that people's adaptive abilities strongly influence the condition of vulnerability.

Moreover, we identified that the vulnerability is not only from external factor but also internal factor. The serial response of the local people to the environmental disturbance exhibits their ability coping the problem. Experience which is represented by the age of stay shows positive effect to the coping capacity. It is also support Adger and Vincent (2005) that explained that experience, education and finance are the main factors of social vulnerability. We also concluded that the situation in Phillipines (Usamah, Handmer et al., 2014) also identified in our research areas. Social capital plays essential role in the disaster communication and then governing the social vulnerability.

Conclusions

The result shows that Tambak Lorok has a low level of social vulnerability, while Bilu Village has a medium level of vulnerability. Tambak Lorok has stronger community ties and stronger environmental ties than Kampung Bilu, which makes the level of vulnerability in Kampung Bilu higher than in Tambak Lorok.

This study revealed that vulnerability concerns not only the people who live in informal settlements such as those in Tambak Lorok, which are at risk of flooding, but also conditions that continue to change through spatial and structural changes in urban areas. Therefore, the conclusions of this study are that vulnerability is a phenomenon that appears and flows in response to a series of pressures from external and internal factors.

The internal pressure is a social and environmental force in regard to housing, a force that changes and can affect people's lives. Tambak Lorok community can overcome its conditions. The external pressure is the influence of policies related to improving the informal housing environment implemented by the government and non-governmental organizations. The better adaptability of the community supports this situation and this internal force.

This mechanism for reducing risk and strengthening the safety net has been designed based on the characteristics of slum communities and is a strategy offered to the inhabitants of the Tambak Lorok slum area. To strengthen and increase community resilience, support is needed. In addition, it is necessary to strengthen social networks because the relationships between residents in slums are incorporated in the economy and socio-culture.

Another important aspect involves identifying and supporting local institutions that are needed to create innovative networks so that they can be stronger. A vibrant civil society and network with local institutions as members should generate different methods of integrating the community itself. The new clusters of a community, such as local RW institutions and private and state institutions, collaborate and are initiated in urban society, adding safety based on diverse approaches to generate adaptation systems and hazard mitigation in the Tambak Lorok coastal area.

Author Contributions

Conceptualization, N.Y. and S.; methodology, S. and S.; investigation, N.Y. and S.; writing—original draft preparation, N.Y.; writing—review and editing, S. and S.; supervision, N.Y. All authors have read and agreed to the published version of the manuscript.

Ethics Declaration

The authors declare that they have no conflicts of interest regarding the publication of the paper.

Funding

This research was funded by Diponegoro University.

Acknowledgments

The authors would like to thank Diponegoro University for supporting and funding the research. The authors would also like to acknowledge the contribution of Tambak Lorok community for their assistance in gathering information.

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