Analysis of Social and Economic Vulnerability to Landslides Disaster in Imogiri District, Bantul Regency

Landslide, one of the natural disasters that often occur, especially in areas that have moderate to high slopes. Imogiri is a sub-district located in Bantul Regency. This sub-district has a percentage of relief of flat to wavy by 30% and relief of wavy to hilly by 70% with a predominantly clay texture. Therefore, Imogiri is included in an area that prones to landslides. In a history of disaster BPBD Bantul explained that there are several areas in Imogiri Subdistrict such as Village of Wukirsari, Sriharjo, Selopamioro, and Karangtengah which are in the red zone. According to the BPBD, in Bantul there were more than 2.000 people living in the red zone. Based on this statement, this study aims to analyze the areas in Imogiri Subdistrict which have low to high landslide hazard levels, as well as analyze the level of social and economic vulnerability of the people living in Imogiri Subdistrict, especially areas with potential landslides. The results obtained from this study in the form of landslide vulnerability maps, social vulnerability maps, and economic vulnerability maps. Based on the map, it can be analyzed that the Imogiri has a moderate level of landslide vulnerability, while the level of social and economic vulnerability in some areas shows a high level of vulnerability. This is influenced by population density, type of work, and its relationship with the level of landslide vulnerability in the areas.


Introduction
Landslide, one of the natural disasters that often occur, especially in areas with moderate to high slopes. Arsyad (2010) and Asdak (2002) explain that a landslide is a form of soil mass transfer in a short time and usually has a relatively large volume. Landslide occurs as a result of the sliding of a volume of soil over a slightly impermeable layer that is saturated with water. Layers consisting of clay or containing clay content will act as a launcher. Harjadi (2013) stated that this landslide occurred in areas with steep slopes or slopes of more than 45%. Landslides usually occur preceded by heavy rainfall or more than 300 mm for three consecutive days, rainwater then falls and enters the soil pores above the impermeable rock layer so that the soil pressure on the slope increases.
Imogiri District is one of the sub-districts located in Bantul Regency. This sub-district has a percentage of flat to wavy relief of 30% and undulating to hilly relief of 70% with a clay texture.
Therefore, Imogiri District is included in an area that is prone to landslides. BPBD Bantul Regency (2019) explained that there are several areas in Imogiri District such as Wukirsari Village, Sriharjo Village, Selopamioro Village, and Karangtengah Village which are areas that are in the red zone prone to disasters. According to the Bantul Regency BPBD, in Bantul there are more than 2,000 people living in the red zone.
When compared with the number of landslides in 17 different sub-districts in Bantul Regency, Imogiri District has the most frequent landslide occurrences from 2015 to 2019. Landslides that often occur in Imogiri District will certainly cause physical, social, economic, and environmental vulnerability. environment. The conditions most closely related to human survival are social and economic. This condition is interesting to study because it is closely related to human life. Therefore, this study discusses social and economic vulnerability to landslides. The social and economic conditions of the community will certainly be different when there is no disaster with a disaster. The existence of a landslide disaster can cause potential disaster losses, especially in social and economic conditions, such as loss of work, decreased production processes, and reduced income. Therefore, Imogiri District requires disaster management efforts both by the government through relevant government agencies and the community supported by research on the impact of landslides in the area.

Method
The research method used is secondary data analysis with ratings and weights on each parameter supported by secondary data validation in the field. While the quantitative technique is carried out by mathematical calculations of scoring the rank value and weight value of each parameter then 'overlay' is carried out to obtain the results of social and economic vulnerability.
Meanwhile, field survey data validation was used to validate the secondary data used. Based on the research method that has been planned, it can be detailed and explained as follows.

Sampling Method
The sampling method in this study used 'purposive sampling method'. This method is a method for taking research samples where the researcher determines sampling by setting special characteristics or making judgments according to the research objectives. This sampling method is included in non-random sampling because each population does not have the same opportunity to be sampled, but is chosen as an object according to the research objectives. Things that must be met to perform this technique include, among others, that the selected sample must have appropriate characteristics, properties, and special characteristics from the population selected as a sample, and from the entire population, the subject or object being sampled must be closest to the description of the research objective. .

Collecting Data
Data collection methods were used to obtain research data. The data collected is secondary data originating from government agencies, BPS, BPBD Bantul Regency, Special Region of Yogyakarta Provincial Population Service..

Data Process
The data processing method used is scoring and weighting the landslide parameters, social vulnerability parameters, and economic vulnerability parameters. The weight value that has been obtained is then determined by the class interval for each parameter by calculating the highest value minus the lowest value then dividing by the number of classes.
Landslide parameter data that had previously gone through the scoring and weighting process were then overlaid or stacked. The results obtained from this overlay process are the level of vulnerability to landslides in Imogiri District. The vulnerability to landslides is divided into 3 classes, namely high, medium, and low. This class will indicate which areas in Imogiri District have a high, medium, or low level of vulnerability to landslides. This landslide vulnerability map is then analyzed based on the level of social and economic vulnerability that has been made.

Data Analysis
The data analysis method used in this study uses the overlay method and the creation of tables to distinguish social and economic vulnerabilities. The table of each vulnerability is calculated through class intervals based on the lowest and highest values of each parameter component. The result of this class interval is then summed from each class in its parameter component and the interval is recalculated. The results obtained from the most recent class interval are then used as the basis for determining the class of social and economic vulnerability in Imogiri District. The results obtained from making tables and filling in the interval values are then entered into ArcMap to create a social and economic vulnerability map that describes the level of socio-economic vulnerability of the community in each village in Imogiri District. This level of social and economic vulnerability will later be divided into 3 classes, namely high, medium, and low so that the class interval calculation of each parameter component is divided by a value of 3.
The vulnerability map that has been made is analyzed by applying geographic analysis techniques. The technique applied is by using a complex regional approach, which has been explained by Yunus (2010) that an area is part of a system in which there are regional components that are believed to be interrelated, reciprocal, and interact with each other. The consequence of this interaction is that if one or more component members change, it may result in changes in other components. Based on this explanation, it can be described that the occurrence of landslides in Imogiri District can lead to changes in both the social and economic conditions of the community so that an analysis of the social and economic vulnerability of landslide disasters is needed which is expected to provide benefits in the future, especially in efforts to overcome landslide disasters.

Land use
Land use in Imogiri District can be divided into 6 types, namely settlements, rice fields, shrubs, dry land, mixed crops, and bodies of water. The dominant land use in the area is mixed crops and rice fields. Mixed land use can be found in the eastern and southern parts of Imogiri District because most of the area is hilly. While the use of paddy fields can be found in the western part of Imogiri District. The majority of residential land use can be found in the western part because the area has a flat relief. Settlements located in hilly areas have a clumped pattern.

Rainfall
Based on the rainfall data, it can be analyzed that the rainfall intensity in Imogiri District is divided into 1 class with a rainfall intensity of 1,500-2,000 mm/year. The same rainfall intensity in the Imogiri sub-district makes the rainfall parameters have the same score when welding is carried out.

Soil Type
Imogiri sub-district is dominated by soil types that are relatively poor in nutrients and easily eroded, such as Mediterranean and litosol. However, there are also types of soil that are rich in nutrients. This type of Mediterranean soil is found in the southern and eastern parts of Imogiri IJDDI 2022, 2, 1, 20 http://ijddi.net District. This soil is formed through the weathering process of limestone so that it has a poor fertility level, yellowish red to gray in color because it contains high carbonate compounds. Therefore, the land in the area is mostly used as fields or fields and mixed crops. Meanwhile, soil types rich in nutrients are more commonly found in the western part of Imogiri District such as alluvial soil, so that in the western part of this area there are many land uses in the form of rice fields.

Slope
There are 5 classes of slope in Imogiri District. Low slope classes can be found in the western part of Imogiri District, while moderate to high slope classes can be found in the eastern and southern parts, and partly on the north side of Imogiri District. When depicted using color, there are 5 colors that indicate the level of slope in this region. Dark green color indicates 0-8% slope, light green color indicates 9-15% slope, yellow color indicates 16-25% slope, orange color indicates 26-45% slope, and red color indicates slope level of more than 45%.

Landslide Hazard Mapping
The level of vulnerability to landslides in Imogiri District is influenced by the relief conditions. The western area of Imogiri District is dominated by a moderate level of landslide susceptibility, while the areas in the east and north and part of the south side are dominated by a high level of vulnerability. Based on the figure, the high level of vulnerability is dominated by hilly relief with a slope of more than 25% and the type of soil is Mediterranean and lithosol. This affects the level of vulnerability to landslides because the Mediterranean soil type is a thin type of soil.

Social Vulnerability
Social vulnerability in Imogiri was mapped using 5 parameters, namely population density, percentage of the disabled population, percentage of the population in the vulnerable or elderly age group, percentage of education, and percentage of female population. Each parameter is welded based on the level of vulnerability where the low vulnerability level is assigned a class 1, the medium vulnerability level is assigned a level 2, and the high vulnerability level is assigned a class 3 as shown in Table 1 below. Source: Giyarsih, et al (2012) in Muawanah (2016) The classed parameters are then weighted and added up from all the parameters as follows.

Economic Vulnerability
Economic vulnerability in Imogiri District was mapped using 3 parameters, namely the area of agricultural land, livelihoods, and the number of economic facilities. Each parameter is welded based on the level of vulnerability where the low vulnerability level is assigned a class 1, the medium vulnerability level is assigned a level 2, and the high vulnerability level is assigned a class 3 as shown in Table 2 below. Source: Giyarsih, et al (2012) in Muawanah (2016) The classed parameters are then weighted and added up from all the parameters as follows.
(6 x area of agricultural land) + (4 x livelihood) + (2 x number of economic means) After obtaining the calculation results, an overlay is carried out between landslide disaster vulnerability and economic vulnerability parameters. Based on the calculation results, there are 4 classes of economic vulnerability for Imogiri District, namely very low, low, medium, and high.
Similar to the level of social vulnerability, the very low and low level of economic vulnerability is

Conclusion
The level of landslide hazard in most of Imogiri District is divided into 4 classes where the dominant class is the medium and high landslide hazard class, the level is influenced by the relief conditions.
The level of social vulnerability in Imogiri District due to landslides can be divided into 4 classes. Most of these areas are classified as having moderate social vulnerability, but there are 2 villages that have high social vulnerability due to having a narrow area and large population, especially people of vulnerable age, causing a higher level of vulnerability compared to other villages.
The level of economic vulnerability in Imogiri District due to landslides can be divided into 4 classes where the majority of vulnerabilities in this area are classified as moderate, but there are 2 villages that have high economic vulnerability because both villages have large land, a lot of economic facilities, but the income of the population by type of work is low, causing a higher level of vulnerability compared to other villages.