Mapping The Location of Flood Shelters in Demak Regency using The Spatial Multi Criteria Evaluation Method

Floods are the most common disasters in the world and severely disrupt lives and livelihoods. Furthermore, the developing countries, especially Indonesia, around 241 flood events in early 2023. The World Bank’s through its Climate Change Action Plan 2021-2025, aims to support Green, Resilient, and Inclusive Development, in pursuing poverty eradication and shared prosperity with a sustainability lens. In the action plan, there are actions to identify and prioritize mitigation and adaptation activities to this effect. In connection with Flood Risk Management where there is no flood shelter location Demak Regency, this study aims to research location using the Spatial Multi Criteria Evaluation method by using the Geographic Information System. Geographic Information System can provide a precise and an effective mapping to mitigate the flood disaster. The Flood shelter can help disaster preparedness activities by minimizing casualties in Demak Regency. Based on the identification results, it was found that there were 36 main points and priority flood shelters in the form of worship facilities and educational facilities.


Introduction
Flooding is a phenomenon of increasing unwanted water discharge (puddles) on the surface caused by overflowing water that exceeds the capacity of water disposal sites in an area [1].According to the Center for Research on the Epidemiology of Diseases (CRED), from the results of calculating the annual average disaster events from 2001 -2021, 45.4% were dominated by flood events [2].Indonesia is a country that frequently experiences floods in 2015, namely 44% of the total number of flood disasters in the world.Indonesia is one of the countries prone to flooding because it has 5,590 main rivers and 600 of them frequently experience floods.Based on BNBP data in 2022 flood events in Indonesia are 1,520 (48%) of the 3,552 incidents of all disasters in Indonesia.In general, floods in Indonesia are caused by hydrometeorological factors, that is climate and weather [3].Indonesia is one of the areas prone to flooding in terms of geographical and geological location and regional characteristics.There are about 30% of the 500 rivers in Indonesia that pass through densely populated areas [4].The problem of floods has existed since humans started living and doing activities in the floodplains [5].
Demak Regency is a northern coastal area which is included in the Kedungsepur Economic Growth Strategic Area.Demak Regency has a recorded population in 2021 of 1,212,377 people with the largest 1264 (2023) 012010 IOP Publishing doi:10.1088/1755-1315/1264/1/012010 2 distribution in Mranggen District (14.57%) and Kebonagung District (3.44%) with a growth rate over the past decade of 1.28% Central Beaureau of Statistics.The condition of the area in Demak Regency consists of lowland areas, hills, and coastal areas, which illustrates the uniformity of the characteristics of natural physical conditions in the form of various slopes, bulges and expanses of lowlands with an average height of 0 -100 MDPL and dominated by relatively flat slopes (0-8%).This natural physical condition coupled with having high levels of rainfall makes Demak Regency vulnerable to the threat of floods, tidal floods, droughts, landslides, and fires [6].
Based on data from the Demak Regency Regional Disaster Management Agency, there were 173 incidents in 2021, 59 of which were floods with the highest number of incidents in Sayung District, 17 incidents with a total loss and damage from the disaster reaching Rp. 24,751,020,946.High rainfall causes several inundation points which result in flood disaster.Floods in Demak Regency are not only caused by extreme weather, but also caused by shipments from the upstream watershed, namely the Babon and Jragung watersheds.The water debit exceeds the capacity of the drainage system and the amount of sedimentation in the river so that the dimensions of the river cannot accommodate the water discharge resulting in water overflow [7].The Jragung watershed, which originates in the Bandungan area, is a watershed that is prone to flooding [8].This happened in Karangtengah District on March 9 2023, when there was an overflow due to heavy rain in the upstream area.Demak Regency is also passed by the Babon Watershed which is prone to flash floods [9].Demak Regency is prone to tidal floods, especially in Sayung District.Tidal floods are caused by tides and sea level rise.It is predicted that in 2090 the sea level will increase by 22-44 cm at a rate of 4 mm/year compared to 1990., while sea level rise in Demak Regency, especially Sayung District, is 8.294 cm/year [10][11].
According to Smith, 1996, modern society is more open in understanding the occurrence of a disaster, so that the awareness of disaster-affected people about disaster mitigation increasingly requires mitigation actions, so there is a need for location planning flood shelters [12].Flood shelters are temporary buildings that are used when a flood disaster arrives with the aim of minimizing losses caused by flood disasters [11].Demak Regency has no flood shelters as a mitigation system.Flood shelter is a temporary building that is used when a flood disaster arrives with the aim of minimizing losses caused by flood disasters.The existence flood shelter locations is a form of capacity building in regional disaster management and helps carry out programs for providing mitigation infrastructure and preparedness in the 2015 -2045 disaster management master plan document [12,13].Determining the location of the flood shelter using the Spatial Multi Criteria Evaluation (SMCE) method and spatial analysis by utilizing a Geographic Information System which is expected to be able to plan the location of the flood shelter in Demak Regency and can improve the quality of Demak Regency's resilience to flood disasters.

Data
This research was conducted in Demak Regency, Demak Regency is one of the autonomous regions in the administrative area of Central Java Province.The administrative area of Demak Regency is divided into 14 sub-districts, 6 sub-districts, 243 villages, 789 hamlets, 1,324 Community Units (RW), 6,942 Neighborhood Units (RT).Demak Regency became the research location because it is one of the areas prone to floods and tidal floods [14,15,16] Based on the results of the 2016-2020 Disaster Risk Study (KRB) for Central Java Province, it shows that the risk of flooding in Demak Regency is high.Flood shelter location planning aims to increase capacity in regional disaster management and assist in implementing the Provision of mitigation and preparedness infrastructure program in the 2015 -2045 disaster management master plan document (Figure 1).

Figure 1 . The Area of Study
In research on flood shelter location planning in Demak Regency, some data is needed, both secondary data and primary (field) data.The following is the data used in the research is in Table 1.

Methods
This research used Spatial Multi Criteria Evaluation (SMCE) method.SMCE has assisted the process of making spatial policy decisions from alternative choices of existing locations by using several criteria that must be met [18].SMCE was basically evaluate several alternatives from several locations and arrange them based on the level of suitability against the spatial criteria [19].The SMCE method is a type of supporting method that collaborates GIS and AHP in the identification process and provides a rating of the parameters used in determining the level of location suitability.SMCE has higher accuracy than AHP.The accuracy rate of the SMCE method map is 96% while the AHP is 91% [20] [21].The basic concept of SMCE based on SMCE Theory is contained in Figure 2 The SMCE Hierarchical Tree [22].

Data Standardization
Each map must have different values in the form of map distances, units and others used on the map. it is necessary to standardize the map that will be used.Standardization is done by transforming the data to the same units.Standardization in the form of scaling is to give scores in each class on the parameters used.Standardization used for each parameter is goal standardization for river distance, road distance, slope, rainfall, settlement distance, land use parameters, and boolean value standardization for tidal inundated areas and flood hazard parameters (Table 2).Source: Analysis, 2023

Weighting
Weighting is done to give weight to each criterion used.In the driving criteria, determining the weight using the AHP method.The AHP method provides weight through a pairwise comparison matrix with data sources from experts or people who are experts in their field.Interviews were conducted using a pairwise comparison interview form.Interviews were conducted with respondents as experts so that the results could be valid and acceptable.Interviews were conducted at the Regional Disaster Management Agency (BPBD) of Demak Regency, BAPPEDA of Demak Regency, DINPUTARU of Demak Regency, affected communities, and disaster academics at Diponegoro University (Figure 3).Based on the processing results, an inconsistency value of 0.02 is obtained, so it can be concluded that the processing results are acceptable and the processing results can be used as weights in determining the level of suitability for flood shelter locations.

Location Suitability Level Analysis
The data that has been prepared, both spatial and tabular data, is then processed for suitability analysis using GIS software using the weighted overlay method.The stages of processing the location suitability level are data analysis, input standardization results, data conversion, weighted overlay, multiplication with the limiting criteria, namely the criteria for flood hazard and tidal flooded areas (Figure 4).The first suitability analysis was carried out using driving criteria, included in one overlay layer and giving weight according to the processing results of the AHP method.The weight value for each criterion has a different value.The weight value indicates the level of importance and influence of the criteria on determining the suitability of the location at Source: Analysis, 2023 Based on the processing results, the level of suitability for flood shelter locations in Demak Regency is dominated by a low suitability level of 65,428.81Ha or around 66.97% of the total area, which means that the area is not suitable for determining the location of a flood shelter.The sub-district that has the widest low suitability level is Wedung Sub-district, which is 12,820 Ha.The second widest low suitability level is located in the Bonang District, which is 8,163 Ha.The widest areas that have a very high degree of suitability are Mranggen District with an area of 4156.87Ha and Karangawen District with an area of 2930.78Ha.This indicates that there are several areas that can be used for flood shelter locations that are free from tidal flood inundation areas, are at a low level of flood hazard, and comply with the location criteria.The high suitability level is also in the recommended zone for flood shelter locations.The high level of suitability for locations is spread over several sub-districts with the largest area being in Karangawen, Karanganyar and Mranggen sub-districts as shown in Figure 5.While the medium suitability level is only found in Karangawen, Mranggen, and Wedung Districts.The middle class is a class that is in the low zone so it is not recommended for flood shelter locations.

Identify Flood Shelter Locations
Identification of flood shelter locations, namely identifying specific locations that can be used for evacuation sites.Flood shelters are basically temporary buildings that are used when floods come.The building can be in the form of temporary housing, public service facilities, and others.Evacuation activities are literally moving from the incident area to an area that is not affected.The selected location is a location that is free from flooding.A location that is safe from flooding is an area that is outside the tidal flood inundated area, has a high class of flood vulnerability, and has a high and very high level of location suitability.The flood shelter chosen in this Final Project is a facility that meets the criteria in terms of accessibility (distance and time).The data used to identify flood shelter locations are data on religious facilities in the form of mosques, educational facilities in the form of elementary/equivalent facilities.SMP/equivalent, and SMA/equivalent, health facilities in the form of hospitals, government facilities in the form of village offices.sub-district offices and others, and social facilities in the form of a multi-purpose building.Other data used is the point of occurrence of the disaster and the map resulting from the suitability of the flood shelter location.The steps taken are to eliminate the facilities using GIS software by entering facility data and maps of the results of location suitability processing.

Input facilities data
Elimination Output facilities Figure 6.Facilities Elimination Process (Analysis, 2023) The elimination process is carried out to remove facilities that do not meet the criteria.Facilities that are at low and medium location suitability levels will be removed and facilities that are at high and very high location levels will be recommended to be used as flood shelters that illustrated in Figure 6.Based on the processing results, it was found that the distribution of flood shelter locations totalled to 36 locations consisting of educational and worship facilities that can be used to evacuate residents when a flood disaster occurs.In addition to the suitability of the location, the basic principle in determining the location of a flood shelter is the proximity factor and the distance travelled by the community to the shelter location.
Sayung District and Karangtengah District are districts that have many shelter locations because they are districts that are prone to flood disasters, both tidal floods and water runoff.The suitability of the flood shelter location is shown in the Figure 7 and Table 4.

Conclusion
Based on the results of the processing carried out, namely the planning of flood shelter locations in Demak Regency, several conclusions were obtained.The results of location suitability processing using the criteria of rainfall, slope, river distance, road distance, land cover, settlements, flood hazard maps, and tidal flood inundated area maps using the spatial multi criteria evaluation (SMCE) method obtained the location suitability class of low, medium, high and very high.From these results it was found that Demak Regency was dominated by a low suitability level of 65,428.81Ha or around 66.97% of the total area, which means that the area is not suitable for determining the location of a flood shelter.
The location used for the flood shelter is in the form of a point that is outside the inundated area of tidal floods, high class flood vulnerability, and has a high and very high level of location suitability.The location of the flood shelter is in an area that has a high level of location suitability and the shelter is dominated by educational facilities and worship facilities.Educational facilities and religious facilities are facilities that are easily accessible and have a large quantity in a region.Based on the identification results, it was found that there were 36 main points and priority flood shelters in the form of worship facilities and educational facilities.
Regency has a slope level in the flat class (0-8%).This is because Demak Regency is located in a lowland and coastal area.Demak Regency is an area located in the downstream area of large rivers.TheDemak Regency area is dominated by the flat slope class (75%) and the sloping class (22%).It can be concluded that in terms of the characteristics of the slope of the area, Demak Regency has the potential for flooding in the form of water overflows, inundation, postal floods and sea water tides.Areas that have extreme slopes are only found in several points in Karangawen and Mranggen Districts.1264 (2023) 012010 IOP Publishing doi:10.1088/1755-1315/1264/1avalue of 2000-2500 mm/year spread across all sub-districts, especially the central and northern parts.In Demak, areas in the high rainfall class have the potential for waterlogging.The most extensive subdistricts with an average rainfall of 2,500-3,000 are in Wedung District.Flood vulnerability Flood disaster vulnerability or flood hazard is an area that has the potential to be in danger of a flood disaster.The flood disaster map is compiled from the parameters of flood-prone areas, rainfall, slope and distance from the river.Demak Regency is dominated by flood hazards in the medium and high classes.Almost 99% of the Demak Regency area is in areas that have the potential for moderate and high flood hazards spread across all sub-districts.Flood accident The points of occurrence of disasters are generally on riverbanks and coastal areas because floods in Demak Regency are caused by runoff water, broken embankments and tidal floods.Areas that are often hit by floods are rice fields and residential areas, so that loss and damage comes from damage to buildings and flooding of rice fields and ponds.For the last 5 years, Demak Regency disaster event data, namely 2018 -2022, flood disasters occurred around 232 events 1264 (2023) 012010 IOP Publishing doi:10.1088/1755-1315/1264/1/0120105 Data Description Connection with the theme Visualization Land cover The land cover pattern in Demak Regency is dominated by rice fields and pond areas in the northern/coastal part.The pattern of paddy field cover is spread across all subdistricts with different areas.In the northern part, stretching from east to west, the pond use pattern is dominated Rice fields are the dominant area in Demak Regency, so rice fields are areas that are often flooded when floods come.The residential area is the largest area after rice fields around 16,168 Ha and the pond area is the largest area after the residential area with an area of 12,237 Ha.

Figure 4 .
Figure 4. Processing Process for Suitability of Flood Shelter Locations (Analysis, 2023)

Table 3 .
Area of Suitability Level for Flood Shelter Location

Table 4 .
Distribution of Flood Shelter Locations