Spatial distribution of social vulnerability to flood disasters in Mejobo Sub-District, Kudus Regency, Indonesia

Central Java province has the highest disaster risk index (score 203) of 33 provinces in Indonesia. In 2022, the Province was most affected by floods with 203 incidents. Kudus Regency is one of the regencies in Central Java that is often affected by floods. Mejobo sub-district is the sub-district with the most flood events in the last 5 years. The frequent occurrence of floods triggers various emerging problems such as social vulnerability. Hence, the purpose of this study is to examine social vulnerability and population analysis in the Mejobo sub-district. The calculation of vulnerability classes uses 5 parameters, namely population density, people with disabilities, vulnerable age groups, poor people, and women. which is then scored for each parameter and classified into 3 vulnerability classes (low, middle, and high vulnerability). The results obtained for low vulnerability were found in 3 villages, namely Jojo, Temulus, and Tenggeles Villages. Moderate vulnerability is in the villages of Hadiwarno, Kirig, and Mejobo. In the high vulnerability class, there are 5 villages, namely Golantepus, Jepang, Gulang, Kesambi, and Payaman.


Introduction
Indonesia is a tropical country with hot and rainy seasons throughout the year [1].Annual rainfall characteristics, sporadic rainfall patterns, severe and prolonged dry periods are influenced by monsoon winds and large-scale climate phenomena such as El Nino Southern Oscillation (ENSO) [2].These climatic conditions, combined with diverse surface topography and rocks can have a positive impact on fertile soil conditions [3].However, these conditions can also have several negative impacts on humans, such as the occurrence of hydrometeorological disasters (floods, landslides, forest fires, and droughts) [4].As time goes by and human activities increase, environmental damage tends to get worse and trigger an increase in the number and intensity of hydrometeorological disasters that occur one after another in various regions in Indonesia [5].
The definition of disaster has been stated in Number 24 Year 2007 of Undang-Undang Republik Indonesia (the Law of the Republic of Indonesia) on Disaster Management, Disaster is an event or series of events that threaten and disrupt the lives and livelihoods of people caused by both natural factors and/or non-natural factors and human factors resulting in the emergence of human casualties, environmental damage, property loss, and psychological impact.Furthermore, there are natural disaster that caused by one or series of natural events such as earthquakes, tsunamis, volcanoes, floods, droughts, hurricanes, and landslides.Non-natural disaster that caused by one or a series of non-natural events that might include failing technology, failing modernization, epidemics, and disease outbreaks.Social 1314 (2024) 012130 IOP Publishing doi:10.1088/1755-1315/1314/1/012130 2 disaster that caused by one or a series of human-caused events that encompass social conflicts between groups or between communities, including terrorism [6].
Floods are one of the most frequent natural disasters and have greatly affected human life and the environment since in the beginning of time [7].The direct impacts of flooding include loss of human life, damage to property and infrastructure, damage to crops and livestock [8].Floodwater is often contaminated with sewage, which can cause disease and affect clean drinking water [9].Flooding can also have long-term impacts, such as the spread of waterborne diseases and worsening health conditions [10].Transportation networks can also be affected, such as damage to bridges, railways, roads, homes and property [11].When flood waters occur, they can carry various materials and debris as they move.Floods can damage crops on farmland and remove natural river banks and levees.Although floods are of natural origin, the main cause of damage can be identified in human occupation of flood-prone areas [12].
Based on data from the National Disaster Management Agency (abbreviated as BNPB) during 2014-2023, the number of flood events in Indonesia reached 8142 events with the highest number of events in Central Java which could reach 1419 events.Floods in Central Java (2014-2023) have caused 214 deaths, 21 people missing, 188,4078 people suffering and 23,738 people displaced.Losses are estimated to reach hundreds of billions of rupiah.Central Java province has the highest disaster risk index (score 203) of 33 provinces in Indonesia.In 2022, the Province will be the province most affected by floods with 203 incidents.Meanwhile, Data for 2023, January -July 2023, total flood events in Central Java reached 14 events.Noted by BNPB Indonesia, several areas in Central Java are included in flood-prone areas, including Kudus, Banyumas, Purwokerto, Pati, Demak, Brebes, and Cilacap Regencies [13].
In Kudus Regency, flooding is a disaster that occurs every year [14] one of the causes of flooding in Kudus Regency is high intensity rainfall.Based on the Meteorology, Climatology and Geophysics Agency (abbreviated as BMKG), the classification of rainfall in Kudus Regency in 2022 has a high annual average rainfall and a very high classification in December -January.Data from the Kudus Regency Agricultural Meteorological Station, Kudus Regency has an average rainfall of 312.9 mm, with the highest rainfall in December -January reaching 700 -860 mm.Based on BMKG data, a rainfall classification of 300 -500 has a high classification, and a very high classification if the amount of rainfall is >500 mm [15].
Mejobo is the most frequently flooded sub-district in Kudus Regency.this is caused by poor drainage density and the high intensity of rainfall.Historically over the past 5 years (2019-2023), in 2019, flooding occurred causing 3 villages (Golantepus, Mejobo, Temulus) to be flooded with a height of up to 60 cm [16].Furthermore, in 2020, flooding occurred by causing 600 houses to be submerged in flood water, the cause of flooding occurred because the Dawe River and Setro River were unable to accommodate rainwater.The water level reached 30 cm [17].In 2021, flooding in Mejobo Subdistrict occurred in Mejobo Village and Golantepus Village with a height of 40 cm, the heavy rain that occurred overnight caused the Dawe River embankment in Mejobo Subdistrict to break [18].
In 2022, flooding occurred not only in Mejobo Sub-district, but also in Kaliwungu and Undaan Subdistricts.The flood caused more than 200 people to be displaced in Jati Wetan Village and Tanjungkarang Church, Jati Sub-district.The total number of displaced residents was 222, the flood height reached 40 cm, and the loss was estimated at 40 million rupiah [19].In 2023, the flooding was more severe because the embankment broke due to the very high intensity of rainwater.There were 5 villages affected by the flood (Golantepos, Kesambi, Mejobo, Temulus, and Hadiwarno).The flood caused 400 houses to be inundated [20].BPBD Kudus reported that a total of 8527 families (2,421 people) were affected and 197 families (571 people) were displaced.The flood inundated 8095 hectares of rice fields.A total of 9 out of 11 villages were flooded, namely Temulus, Mejobo, Payaman, Gulang, Hadiwarno, Kesambi, Kirig, Jojo, and Golantepus Villages.The number of refugees in Mejobo Subdistrict was 44 families (113 people) spread across 4 points (Temulus Village Hall, Mejobo, Payaman, Gulang).The following are flood events in Mejobo Subdistrict in 2019-2023 (Figure 1).Mejobo sub-district is located on an alluvial plain formed by the activity of the Juwana River.The alluvial plain is a fertile soil because the nutrients in the water are slowly absorbed into the soil making it suitable for agricultural land.The slope of the area tends to be flat.Passed by the Pantura Line, which is the main economic route in the northern region of Java Island, Mejobo Sub-district plays an important role.This makes many industries grow in the surrounding area.
This study aims to analyze the social vulnerability of communities in Mejobo Sub-district in the face of flood disasters.Social vulnerability assessments are used to identify factors that contribute to social vulnerability and to design fair and equitable flood risk management strategies.The criteria used to analyze social vulnerability to flood disasters in this study include population density, number of people with disabilities, vulnerable age groups, female population, and poor population in Mejobo Sub-district.By identifying factors that contribute to social vulnerability, flood risk management strategies can be designed to meet the specific needs of socially vulnerable populations and reduce the impact of flooding on communities.
Social vulnerability can have a significant influence on the impact of flooding on communities.Socially vulnerable populations tend to live in flood-prone areas and have limited resources to cope with flood impacts.Social vulnerability assessments can be used to identify factors that contribute to social vulnerability and design fair and equitable flood risk management strategies.

Methods
The research location is in Mejobo Sub-district, with an absolute location of -6.8428078, 110.8910556 and a relative location in the east of Kudus Regency which is directly adjacent to Jekulo Sub-district to the east and north, Sukolilo Sub-district in Pati Regency and Undaan Sub-district to the south, and Jati Sub-district to the west.This sub-district has an area of 37.33 km 2 , which is shown in Figure 2 as follows:

Figure 2. Administrative Map of Mejobo Sub-District
This research used a quantitative deductive method.The research was conducted through several sources such as Central Agency on Statistic (abbreviated as BPS), literature review, and news portals.From the literature, this research can be carried out in determining which parameters are influential.In this research, the tools and materials used are presented in Table 1 and Table 2 Geographic information system (GIS) can be used to investigate flood [21][22][23][24].There were several calculations for population density, population with disabilities, vulnerable age group, poor population, and female population.Population density has a significant influence on disaster impacts.Population density greatly affects the evacuation process and disease transmission during an outbreak, as well as being a measure of potential exposure to life during a flood disaster [25].Area size is a measure of population movement; vulnerability will increase if a large number of people live in a narrow area because it affects accessibility during evacuation [26,27].The following formula is used in calculating population density: The parameter of the number of people with disabilities also affects social vulnerability to flood disasters.Disabled groups are vulnerable to disasters, due to their limited ability to anticipate and react so they are at risk of injury and trapping [1].The following formula is used in calculating persons with disability: Next, World Bank (2018) stated that children and the elderly are more vulnerable to the impacts of natural disasters due to their physical limitations and dependence on others for assistance.They may have difficulty evacuating, understanding instructions, or communicating during an emergency [28].The following formula is used in calculating vulnerable age group: Poor people are more often affected by natural hazards because they often have to settle in areas at risk, Limited financial resources can force them to live in locations prone to flooding, landslides, or other hazards, Lack of access to safe housing and infrastructure increases their exposure to disaster risk [29].Beside that,it isalso related to the time needed for affected people to recover from disasters [30].The following formula is used in calculating percentage of poor population: Percentage of Poor Population = Women's specific health needs and safety concerns can make them more vulnerable during disasters.These include pregnant women, new mothers, and women with chronic health conditions who require specialized care and support that may be disrupted during emergencies [31].The following formula is used in calculating percentage of female population: Percentage of Female Population =     (5) After the data was processed, scoring was conducted for each of these parameters.Vulnerability scoring uses parameters classified into 3 classes with the assumption that score (1) is low class, score (2) is middle class, and score (3) is high class.Social vulnerability parameters consist of population density, number of people with disabilities, number of women, number of poor people, and vulnerable age groups.The social vulnerability scoring table can be seen in Table 3. From the parameter data, the scoring results of each variable indicate the level of social vulnerability.The results analysis of each parameter are classified into 3 vulnerability classes, namely low (1), middle (2), high (3).These five parameters were then classified and scored.The scoring results of each parameter are then summed up and the final scoring value is obtained, then classified again into 3 classes, namely low, middle and high classes.The total classification of scoring can be seen in Table 4.The final stage of the model development aims to present the real conditions in the field in the form of a social vulnerability map in Mejobo Sub-district.All social vulnerability variables were scored and mapped, then overlay analysis was conducted.Overlay analysis was conducted by entering data on social vulnerability variables using quantitative data and spatial data in the form of maps that aim to determine the level of social vulnerability in Mejobo Sub-district.

Results and Discussion
This research aims to analyze the level of social vulnerability of communities in Mejobo Sub-district to floods.Mapping the level of social vulnerability is supported by other parameters which results in a map of the distribution of social vulnerability to flooding.Social vulnerability to flooding uses 5 aspects, namely the percentage of population density, percentage of people with disabilities, percentage of vulnerable age population (elderly and toddlers), poor population, and female population.

Population density
The results of population density are described in table 5. From the processing results, the population density in Mejobo Sub-district is divided into 3 classes (Fig. 3).In class 1 (low) there are 5 villages, namely Gulang, Jojo, Kirig, Payaman, and Temulus, with density values between 7.74 -18.96 people/ha.Class 2 (middle) there are 3 villages, namely Golantepus, Hadiwarno, and Kesambi, with a density value between 18.96-30.18people/ha.Class 3 (high) 3 villages, namely Jepang, Mejobo, and Tenggeles with a density value between or more than 30.18-41.44 people/ha.Mejobo Village has the highest density, while Kirig Village has the lowest.

People with disabilities
The results the percentage of the population with disabilities are described in Table 6.From the processing results, 3 vulnerability classes were obtained, class 1, class 2, and class 3. Class 1 (low vulnerability class) whose percentage lies between 0.09-0.33% is 4 villages, namely Golantepus, Hadiwarno, Mejobo, and Tenggeles Villages.Class 2 (middle vulnerability), which lies between 0.33-0.57%,consists of 5 villages, namely Jepang, Jojo, Kirig, Payaman, and Temulus.Class 3 (high) is 2 villages, namely Gulang and Kesambi.The highest percentage of villages with disabilities is Gulang Village at 0.81% (59 people), and the lowest percentage is Tenggeles Village at 0.09% (0 people) of the total population of each village.The results of the map of people with disabilities can be seen in Figure 4.  Social vulnerability is the potential loss to a group and indicates the estimated amount of life or health safety of the population in the event of a disaster [32].Socio-economic vulnerability relates to the ability of individuals or community groups to cope, survive and recover from the impact of disaster events, 1314 (2024) 012130 IOP Publishing doi:10.1088/1755-1315/1314/1/01213013 [33].The parameters for compiling social vulnerability consist of population density, the number of people with disabilities, vulnerable age groups (toddlers and elderly), the number of poor people, and the number of female residents in Mejobo District, Kudus Regency.
In Mejobo Sub-district, the population density varies from low, high and middle.High population density is found in Tenggeles, Jepang and Mejobo Villages.Factors affecting population density in these villages are the availability of complete facilities [34].In Mejobo Sub-district, there is 1 hospital in Jepang village, as well as easy accessibility to these facilities.There are 2 large-scale industries in Tenggeles Village and Jepang Village, and a middle-scale industry in Mejobo Village, as well as industries and household industries where most of the population work as industrial laborers.Economic facilities in the three villages are very adequate, with two markets in Jepang and Mejobo villages and one market in Tenggeles Village.
The parameter of the persons with disabilities are vulnerable to disasters due to increased vulnerability, social barriers, disproportionate impacts, and adverse socioeconomic outcomes [35].In Mejobo Sub-district, it is divided into 3 classes, namely low class in 3 villages (Mejobo, Golantepus, Hadiwarno), middle class in 5 villages (Jepang, Payaman, Kirig, Temulus, and Jojo), and high class in 2 villages.The total number of people with disabilities in Kecamatan Mejobo is 329 people spread across 11 villages or around 0.42% of the total population.The villages included in the high class are Gulang Village and Kesambi Village.It is important to maximize inclusive disaster preparedness, response and recovery efforts.By promoting accessibility, inclusiveness, their vulnerability can be reduced and their resilience can be enhanced in the face of disasters.
Age group is the third parameter in determining social vulnerability.There are 2 classes in the vulnerable age group parameter, namely low class (8 villages) and high class (3 villages).Gulang, Jepang and Payaman villages.Population size is the determining factor for the age group vulnerability parameter.Grouping by age is done because the toddler and elderly population (over 65 years old) are very vulnerable to disasters because they have limited mobility and cannot easily evacuate independently in the event of a disaster.In contrast, the productive age population tends to be more responsive when a disaster occurs.The village with the highest number of people of vulnerable age is Payaman Village, with 677 out of 5,578 people.The village with the least number of people of vulnerable age is Kirig Village, indicating that there are many people of productive age in the village.
Poverty and inequality are major risk drivers of disasters.Impoverished people are more likely to live in hazard-exposed areas and are less able to invest in risk-reducing measures (24).The poverty percentage is divided into three classes: low (5 villages), middle (4 villages), and high (2 villages).The villages with the lowest poverty percentage class are Jepang, Mejobo, Payaman, Temulus, and Tenggeles villages.Villages with middle poverty levels are found in Gulang, Kirig, Kesambi, and Jojo, indicating that the community is still in a better condition than the low-income population.Villages with the highest percentage of poverty are Golantepus and Hadiwarno.
The last parameter is the female population.Gender is a factor that affects disasters because it is considered that the female population is more vulnerable to disasters than the male population, [33].The percentage of female population in Mejobo Sub-district is divided into 3 classes, class 1 (low) is in Jepang, Tenggeles, Temulus, and Jojo Villages, class 2 (middle) is in Gulang, Kirig, and Hadiwarno Villages, class 3 (high) is in Golantepus, Mejobo, Payaman, and Kesambi Villages.Jepang Village has the largest number of female residents (6335 people) or approximately 49.36% of the total population.The largest percentage of the population is in Golantepus Village with 50.61% and the smallest percentage is in Tenggeles Village.After analyzing with 5 scoring parameters, then weighting is carried out for each village in Mejobo Sub-district.Then the final results of the weighting will be summed up to produce a class of vulnerability level to flood disasters.The results obtained in Mejobo Sub-district are 3 levels of vulnerability classes, namely low (3 villages), middle (3 villages), and high (5 villages) vulnerability classifications.Villages that have a low level of vulnerability are Jojo, Temulus, and Tenggeles.

Conclusions
The calculation of vulnerability classes uses 5 parameters, namely population density, people with disabilities, vulnerable age groups, poor people, and women.which is then scored for each parameter and classified into 3 vulnerability classes (low, middle, and high vulnerability).The results obtained for low vulnerability were found in 3 villages, namely Jojo, Temulus, and Tenggeles Villages.Moderate vulnerability is in the villages of Hadiwarno, Kirig, and Mejobo.In the high vulnerability class, there are 5 villages, namely Golantepus, Jepang, Gulang, Kesambi, and Payaman.

Figure 4 .
Figure 4. Map of the Population with Disabilities in Mejobo Sub-District

Figure 8 .
Figure 8. Social Vulnerability Map of Mejobo Sub-District

Table 1 .
. Tools used in research

Table 2 .
Data used in research

Table 3 .
Scoring of Social Vulnerability Parameters Table for Social Vulnerability Parameters

Table 6 .
Number of Persons with Disabilities in Mejobo Sub-District