Disaster risk analysis of Merapi Volcano eruption in the north slope based on the New Volcanic Risk Ranking (VRR) methods

Merapi Volcano is one of the most active volcanoes in the world and has inconsistent direction and eruption types. In addition, unplanned urbanization and the ever-increasing population on the North Slope of Merapi Volcano can cause population concentration and increasingly complex economic activities in areas exposed to natural hazards. This research aims to determine the hazard, exposure, vulnerability, resilience, and risk of Merapi Volcano eruption on the northern slopes. Risk level analysis uses the New Volcanic Risk Ranking methodology. The New Volcanic Risk Ranking consists of 34 parameters, with hazard having two parameters, exposure having nine parameters, vulnerability having ten, and resilience having thirteen parameters. Because the number of parameters evaluated for each factor is different, normalization is required to 10 so that they have the same weight. The research results show that the eruption threat index on the northern slopes of Merapi Volcano was dominated by high class, with the highest areas in Tlogolele Village (priority in Hamlet 5) and Klakah Village (focus in Hamlet 3 and 4). The high-exposure index within a 5 km radius of the Merapi Volcano crater is Tlogolele Village (priority in Hamlet 5) and Klakah Village (focus in Hamlet 4). The overall vulnerability index on the North Slope is in the medium class. The highest disaster resilience index is in Tlogolele and Klakah Villages. The high-risk level is in Tlogolele Village (priority in Hamlet 5) and Klakah Hamlet (focus in Hamlet 3 and 4).


Introduction
Merapi is one of the most active volcanoes in the world [1], located in the subduction zone of the Indo-Australian Plate, which subducts beneath the Eurasian Plate [2,3].Merapi volcano is in four administrative, Sleman, Magelang, Klaten, and Boyolali districts.Merapi Volcano has been actively erupting for an average of 3.5 years [4].Small eruptions occur every 2-3 years, while high eruptions occur once every 10-15 years [5].The results of historical studies show that the center of Merapi's Volcano eruption changes.Around 400,000 years ago, the center eruption on the northeastern slopes known as Mount Bibi, then 40,000 years ago, the eruption center moved to the southern slopes with the names Mount Turgo and Plawangan; in 8000-2000 years ago, the eruption center moved to the northern slopes with the former crater at Pasar Bubrah, and finally Merapi Volcano which is known to currently appear above Pasar Bubrah as the center of the eruption [3].Based on BPPTKG records, the direction of Merapi's Volcano eruption also changes, influenced by changes in the shape of the mountain peak.The movement of eruptions recently has been dominant towards the southwest and south, but this does not rule out the possibility that the northern slope area also has the potential to be affected by the eruption There are 9 (nine) exposure parameters, namely population density, residential buildings, transportation, electric power infrastructure, water infrastructure, telecommunications infrastructure, emergency facilities, important facilities, and economic activities [11].The next step is to overlay a map of each exposure parameter using ArcGIS.

c. Merapi Volcano Eruption Vulnerability Index
Vulnerability refers to physical, social, economic, and environmental conditions that are susceptible to danger [15,17,18].The vulnerability index data analysis technique is to provide a score for each vulnerability parameter according to the provisions of the New Volcanic Risk Ranking (VRR) method.There are four vulnerability parameters, namely physical vulnerability, systemic vulnerability, social vulnerability, and economic vulnerability [10].Physical vulnerability is assessed based on the type of main construction in the community within a radius of 5 km and 10 km from the crater of Merapi Volcano.Systematic vulnerability is assessed based on redundancy (important facilities, emergency facilities, transportation, electric power infrastructure, water infrastructure, and telecommunications infrastructure), accessibility, and border distance to the volcanic crater.Social vulnerability is assessed based on age, ethnicity, unemployment, disability, and education level.Meanwhile, economic vulnerability is assessed based on the number of economic activities, including livestock, forestry, fisheries, mining, industry, or tourism within a radius of 5 km and 10 km from the crater of Merapi Volcano.The vulnerability index is obtained by overlaying a map of each parameter using ArcGIS software.

d. Merapi Volcano Eruption Resilience Index
Resilience is defined as a society's ability to adapt to change and the capacity to overcome disturbances with the aim of reaching a new level of balance and dynamics.Therefore, resilience is considered a positive factor that reduces risk.The data analysis technique to determine the resilience index is to give a score to each question item in accordance with the provisions of the New Volcanic Risk Ranking (VRR) methodology.There are two resilience parameters, namely: (1) Mitigation includes volcanic risk and hazard maps, land use planning, monitoring, early warning systems, simulation exercises, outreach or education, and insurance protection; (2) Emergency response includes evacuation plans, availability of shelters, successful evacuation in the event of an eruption that has occurred.The resilience index is obtained by overlaying a map of each parameter using ArcGIS software.

e. Merapi Volcano Eruption Risk Index
Based on Republic of Indonesia Law no.24 of 2007 concerning Disaster Management, disaster risk is the potential loss arising from a disaster in an area and a certain period in the form of death, injury, illness, life at risk, loss of security, displacement, damage or loss of property, and disruption of community activities.After obtaining the hazard index, exposure, vulnerability, and resilience, normalization is required.Based on [19], the score value for each parameter was chosen after performing a sensitivity analysis with different score values.According to [6,17], each factor was equally normalized to ten for them to have the same weight regardless of the different scores, following standard strategies.The following is a normalization factor for the hazard, exposure, and vulnerability index.
Meanwhile, normalization for the resilience index adds a value of 1.The following is a normalization factor for the resilience index.
After obtaining the normalized values for hazard, vulnerability, exposure and resilience, the disaster risk index is calculated using the following formula: (1) Then the results of the calculation are classified based on the classification of low, medium, and high according to the value and colour as follows.

Research Area
The research area on the North Slope of Merapi Volcano is primarily in the Selo District, Boyolali Regency, including the villages of Tlogolele (five hamlets), Klakah (four hamlets), Jrakah (three hamlets), Lencoh (two hamlets), Samiran (three hamlets), and Suroteleng (two hamlets).This area is dominated by the high slope class, namely 15-25% with an area of 669.75 Ha or 24.26% of the total area, then the slope class >45% with an area of 659.Based on Table 2 above, the areas that have a high threat class for the eruption of Merapi Volcano on the North Slope are the villages of Tlogolele, Klakah, Jrakah, Lencoh, Samiran and Suroteleng.The largest high-threat class is in Tlogolele Village, with 843.18 hectares or 100% of the village area, and Klakah Village, 617.45 hectares or 81.12%.Tlogolele and Klakah villages are the most significant areas threatened by the eruption of Merapi Volcano.Apart from that, Tlogolele Village is crossed by the Apu River, which originates in the Merapi crater.Historically, this river has been a route for hot and cold lava.A residential area in the high threat zone 3 km from the crater, namely Stabelan Hamlet, Tlogolele Village.The following is a map of the eruption threat on the northern slopes of Merapi Volcano.Economic vulnerability is a natural event that causes loss of resources and impacts the territorial system over a long period so that it can affect the development of a region.The economic vulnerability factor is calculated based on economic activities carried out by the community within a radius of 5 km and 10 km from the peak of Merapi Volcano.Lencoh, Suroteleng, and Samiran villages have the most diverse economic activities.Physical vulnerability is the loss of buildings, such as building categories and construction materials, due to hazards.The type of community building construction on the northern slopes of Merapi Volcano is more than 50% reinforced concrete structure.These buildings include villas, apartments, and collective residences within a 5 km and 10 km radius in all study villages.Systemic vulnerability is the level of vulnerability to the direct or indirect effects of several physical, functional, or organizational failures, with the main aspect being a lack of redundancy (based on the amount of each type of infrastructure, for example, transportation, electricity, water, telecommunications in a particular area) and the level of accessibility (based on the number and type of transportation facilities available to reach an infrastructure).Meanwhile, social vulnerability refers to the inability of people, organizations, and society to withstand the adverse impacts of danger due to the inherent characteristics of social interactions, institutions, and cultural value systems.Social vulnerability is related to the well-being of individuals, communities, and society, including literacy and education levels, security, customs/ethnicity, age, unemployment, and disability.Of these five parameters, the most influential factors are vulnerable people, namely those aged less than five years, those aged more than 60 years, and disabilities.The availability of risk and hazard maps strengthens community resilience.However, there is a need to increase capacity in all villages including hazard-based spatial planning, early warning systems and insurance protection.The entire resilience index on the northern slopes of Merapi Volcano can be seen on the following map.Then using Merapi Volcano eruption risk analysis using the New VRR method results that the highrisk level for Merapi Volcano eruption on the North Slope is in Tlogolele Village (Priority Hamlet 5) and Klakah Hamlet (Priority Hamlets 3 and 4).Increasing resilience is one way to reduce the risk of eruption disasters, through this method it is necessary to increase capacity in all villages including hazard-based spatial planning, early warning systems and insurance protection.

Figure 1 .
Figure 1.Location Research Map in North Slope of Merapi Volcano3.2.Hazard Indeks Merapi Volcano EruptionThe threat of exposure to the eruption of Merapi Volcano on the northern slopes occurs not far from the central crater point, which experts have included in the Merapi Volcano Disaster Prone Area.Apart from that, the threat of volcanic eruptions also lies in areas crossed by rivers that originate in the crater area of Merapi Volcano, such as the Apu River, which separates Tlogolele Village from other villages in the Selo District.The threat of the eruption of Merapi Volcano on the North Slope of Merapi Volcano can potentially threaten six villages, including the Jrakah, Klakah, Lencoh, Tlogolele, Samiran and Suroteleng.The following is the area threatened by Merapi Volcano's eruption.

Figure 2 .
Figure 2. Merapi Volcan Hazard Map in North Slope3.2.1.Exposure Indeks Merapi Volcano Eruption.Exposure is assessed based on nine parameters, but five parameters have the most influence: population density (people/km2), residential buildings, transportation, essential facilities, and economic activities, which are calculated based on a radius of 5 km and 10 km from the crater of Merapi Volcano.Based on calculations, population density with a medium classification is in the villages of Jrakah, Lencoh, and Samiran, while with a low category, it is in the Klakah, Tlogolele, and Suroteleng.The population on the northern slopes is 19,289 people; the male population is 9,946 (51.56%) while the female population is 9,343 (48.44%).Apart from that, residential settlements were found relatively close to the crater, namely in Stabelan Hamlet, which is 3 km from the crater of Merapi Volcano.The closer to a residential building, the higher the level of exposure in an area.The most significant residential buildings within a radius of 5 km from the crater of Merapi Volcano are in Samiran Village, with an area of 53.46 Ha, then in Lencoh Village, with an area of 38.45 Ha, and Suroteleng Village with an area of 37.32 Ha.Meanwhile, the lowest place is in

Figure 3 .
Figure 3. Area of Residential Buildings on the North Slope within 5 km radius and 5-10 km from the crater of Merapi Volcano in hectares

Figure 4 . 7 Figure 5 .
Figure 4. Length of Roads on North Slope within 5 km Radius and 5 -10 km in units of km Essential public facilities such as government offices, school buildings, recreational facilities, etc., will contribute to high exposure values.The number of critical facilities on the North Slope within a 5 km radius from the crater of Merapi Volcano in Tlogolele Village is 8 points, while in Klakah Village, there are 2 points in a 5 km radius and 7 points in a 10 km radius.Agriculture is the most influential economic activity because most people on the North Slope of Merapi live as farmers.The most extensive agricultural land is in Klakah Village, with an area of 305.98 ha.The following is a graph of the exposure of agricultural land on the North Slope of Merapi Volcano.
Based on the analysis results, the vulnerability class is moderate in all villages on the North Slope of Merapi Volcano.Still, there are high points, namely in Tlogolele Village in Hamlet 5, Klakah Village in Hamlet 3 and 4, Jrakah Village in Hamlet 3, 4 and 5, Village Lencoh is in Hamlet 1 and 2, Samiran Village is in Hamlet 1, 2 and 3, and Suroteleng Village is in Hamlet 2 and part of Hamlet 1.The Merapi Volcano Eruption Vulnerability Map can be seen as follows.

Figure 7 .
Figure 7. Merapi Volcano Vulnerability Map in North Slope Based on the assessment of eruption disaster resilience indicators on the North Slope of Merapi Volcano, high scores exist in all villages.The highest total indicators of the mitigation parameters are spread across 3 villages, namely Klakah Village.During the emergency response period consists of three indicators: the existence of evacuation SOPs, agreed evacuation locations, and successful evacuation.All resilience indicators were rated as good, and the highest community resilience indexes were in Tlogolele and Klakah Villages.The following is a capacity assessment based on disaster mitigation in facing an eruption on the North Slope of Merapi Volcano.

Figure 8 .
Figure 8.Total results of Merapi Volcano eruption disaster mitigation indicators in North Leren

Figure 9 .
Figure 9. Merapi Volcano Resilience Map in North Slope3.2.4.Risk Indeks of Merapi Volcano Eruption.The risk index for the eruption of the northern slopes of Merapi Volcano is assessed based on the threat, exposure, vulnerability, and resilience index.The higher the level of disaster risk, the greater the potential for losses due to the eruption of Merapi Volcano.These losses include casualties, injuries, damage or loss of property, and disruption of community activities.Based on the analysis produced in the research area, no one is at high disaster risk, but only in the medium and low classes.The most significant medium class is in Tlogolele Village (326.99 Ha, priority Hamlet 5) and Klakah, with an area of 105.02 Ha (Priority Hamlets 3 and 4).Meanwhile, the low class with the highest percentage is in Suroteleng Village, with a 413.92Ha or 100%.Thus, the total area of the medium class is 447.95Ha, and the low class is 2317.44Ha.The following is a graph of the extent of the risk of an eruption of Merapi Volcano.

Figure 10 .
Figure 10.Graphic of Merapi Volcano Eruption Risk Area on North Slope

Figure 11 .
Figure 11.Merapi Volcano Risk Map in North Slope

Table 1 .
Classification of values and colours in the index calculation

Table 2 .
Merapi Volcano Eruption Hazard Area in Hectares

Table 3 .
Extent of Merapi Volcano Eruption Exposure on North Slope

Village Extent of Merapi Volcano Eruption Exposure on North Slope (Ha) Total Area
Vulnerability Indeks Merapi Volcano Eruption.Vulnerability is assessed based on Economic, Physical, Systemic, and Social vulnerabilities calculated based on the unit of analysis of the land unit.
Figure 6.Merapi Volcano Exposure Map in North Slope

Table 5 .
3.2.3.Resilience Indeks Erupsi Gunungapi Merapi.The resilience index using VRR methodology is measured by parameters of mitigation and community emergency response.Mitigation parameters consist of 10 indicators and emergency response there are 3 indicators.The following is a table of mitigation and emergency response parameter indicators.Mitigation and emergency response parameter indicators results.