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1 Special Session on Urban Water Environment Monitoring & Management, 4 th International Conference on Structural Engineering and Construction Management 2013, Kandy, Sri Lanka, 13 th, 14 th & 15 th December 2013 SECM/13/236 SELECTION OF SUITABLE SITES FOR LAND FILLING OF SOLID WASTES USING GIS INTEGRATED WITH ANALYTIC HIERARCHY PROCESS (AHP): A CASE STUDY FOR THE GALLE MUNICIPAL COUNCIL AREA A.G.O.A. Chathuranga 1, J.K.A.L. Darshaka 2, A.G.A. Wanshanatha 3, W.K.C.N Dayanthi 4 1 Department of Civil & Environmental Engineering, University of Ruhuna, Sri Lanka. Telephone: osura89@gmail.com 2 Department of Civil & Environmental Engineering, University of Ruhuna, Sri Lanka. Telephone: lahirudarshaka@gmail.com 3 Department of Civil & Environmental Engineering, University of Ruhuna, Sri Lanka. Telephone: aruna182@gmail.com 4 Department of Civil & Environmental Engineering, University of Ruhuna, Sri Lanka. Telephone: neetha@cee.ruh.ac.lk Abstract: Land filling is one of the primary methods of municipal solid waste disposal. Appropriate selection of landfill site is an important issue due to enormous impacts on the economy, ecology, environment and public health. The aim of this study was to use GIS technology and multi-criteria decision technique called Analytic Hierarchy Process (AHP) in finding suitable landfill sites for solid waste disposal in the study area and to evaluate the existing landfill sites. Several factors were considered in the siting process including surface water bodies, forest reserves, wetlands, town and village centers, coastal belt, important buildings, transportation network and land use pattern. Weights were assigned to each criterion depending upon their relative importance and relative magnitude of impact using AHP. The weights were incorporated into GIS environment to determine suitability of landfill sites in study area. The study revealed that the present dumpsite of Galle Municipal Council was categorized as moderately suitable for landfill siting. Keywords: Land filling, GIS, AHP, Siting 1.0 Introduction In Sri Lanka integrated solid waste management is hardly practiced. A greater percentage of the raw solid waste is usually open dumped. These open dumps are a threat to the living and non-living environment. In fact open dumps do not comply with the environmental protection regulations. The 69

2 proper practice is to dispose only inert matter in engineered landfills. Even engineered landfills should be located at places that impose less adverse impacts. Therefore selecting appropriate sites for land filling is a major issue in both developed and developing countries. In order to overcome these problems, selecting appropriate landfill sites as well as evaluating the existing locations of landfill site are imperative to prevent negative impacts on the public as well as the environment. Landfill siting is a complex process involving the processing of massive amount of spatial data. At present a new application technology called Geographic Information System (GIS) is frequently used for the process of landfill site selection. GIS is an efficient and a latest tool that is integrated with computerized software tools, mathematical and statistical methods for efficient and effective site analyses. Selection of appropriate landfill sites depends on several factors such as land use, transportation network, environment, hydrology etc. The Analytic Hierarchy Process (AHP) is a multi-criteria decision technique that helps the decision maker to set the priorities and make the best decision by reducing complex evaluations to a series of pair wise comparisons. Combining GIS and AHP is a powerful tool to solve the landfill site selection problem, because GIS provides an efficient manipulation and presentation of data and AHP provides factor s weights of the landfill sites according to the importance of the criteria. 2.0 Literature review 2.1 Landfill site selection criteria The landfill site selection criteria are associated with the bio-physical environmental features such as surface water bodies, forest reserves, wetlands, town and village centers, coastal belt, important buildings, transportation network and land use pattern. Streams, channels, lakes, tanks, lagoons, lewayas and etc. are considered as surface water bodies. According to the Central Environmental Authority (CEA), all surface water bodies that may be affected by a contaminant release from a source of wastewater shall be monitored to prevent waste entering the water body which may have irreversible environmental and health impact. Therefore, the appropriate distance from a landfill to a water body should be greater than 100 m. National parks and reserved forests are included in forest reserve. To avoid the risk of damaging areas of high environmental value such as forest reserves, national parks landfill sites should be within 250 m of any of the above areas according to Environmental guidelines: Solid waste landfill (EPA, 1996). Wetlands include marshes and mangroves. Distance of 100m and above from the wetlands to the landfill was considered as the suitable location of landfill sites (Environmental guidelines: Solid waste landfill (EPA, 1996)). The aim is to protect the environmental values of sites which have mangroves and reduce the ground water pollution due through the wetlands. Site for landfill should be safe 500m and above distance from the Town & Village centers. Landfill sites should be located as close as possible to where solid waste being generated to minimize handling and reduce transport cost according to CEA. A distance of 500m and above from urban areas was considered as to be suitable for landfilling (Mohd Din, 2008). 70

3 The coastal belt is an environmental sensitive area with a sandy soil layer. Therefore distance of 100m and above from the coastal belt was considered as the suitable location of landfill sites to protect the environmental values and protect the ground water condition (Environmental guidelines: Solid waste landfill (EPA, 1996)). Residential buildings, public buildings, commercial buildings, factories, hotels, religious buildings are normally included as important buildings. A landfill site should be located more than 250 m away from important buildings. According to EPA (1996), landfill sites should not be within 250 meters of a residential zone or a dwelling not associated with the development and, in the opinion of the consent authority likely to significantly affect the amenity of the neighborhood by reason of noise, visual impact, air pollution (including odor, smoke, fumes or dust), vermin or traffic. Landfill sites should not be placed too close to the roads, railways etc. due to health and aesthetic reason. But landfills should be located as close as possible to roads to reduce transport cost. By considering suggested distance from the literature review, and CEA, the distance of 1000m-2500m is taken as the most suitable and below 100m is considered as unsuitable for landfill sites (Jayawickrama, 2010). This includes agricultural lands, hydrological features, reserves, forest, buildup areas, homesteads, grassland and scrubs. Landfill should not be located in agricultural land (Abu Albert, 2010). The land use criterion was incorporated into the ArcGIS 9.3 and reclassified into not suitable, less suitable and high suitable. Agricultural lands, hydrological features, reserves, forest, buildup areas consider as unsuitable areas for landfills. Homesteads taken as less suitable and grass lands, scrub lands taken as high suitable for landfills. 3.0 Materials and methods 3.1 Landfill site selection criteria The first step of the methodology was to identify different criteria for landfill site selection. The criteria were obtained from the EPA (EPA, 2006) guidelines; technical guidelines on solid waste management published by the CEA; and research articles on the same nature (Mohd Din, 2008; Jayawickrama, 2010; Abu Albert, 2010; Ayo Babalola, 2010). The landfill site selection criteria which are associated with the bio-physical environmental features, namely surface water bodies, forest reserves, wetlands, town and village centers, coastal belt, important buildings, transportation network, land use pattern, slope of the ground were considered for the study. The slope was considered at the secondary screening while the other features were used for the primary screening. Table 1 depicts the suitability and unsuitability criteria for selected features. 3.2 Developing the suitable area map Arc GIS 9.3 was used to develop maps. A database of 8 feature classes was created using the individual map for each of above features, developed by the Survey Department. During the primary screening process, 7 features, namely, surface water bodies, forest reserves, wetlands, town and village centers, coastal belt, important buildings, transportation network were used. An individual map (feature class) was developed for each of these 7 features using the associated landfilling constraints. This was done by buffer tool in Arc GIS. These maps are called constraint maps. Then 71

4 all individual constraint maps and the unsuitable area map of the land use pattern was union using the union tool in Arc toolbox to extract the suitable area. Then the overlaid area was erased from the study area map by using the erase tool in Arc toolbox. The remaining map was called the suitable area map. Feature Surface water bodies Table 1: Suitability and unsuitability criteria for the selected features Criteria for Criteria for suitability unsuitability Low Moderate High Remarks <100m m m >600m Distance Forest reserves <250m m m >450 m Distance Wetlands <100m m m >300 m Distance Town and village centers <500m m >2500m m Distance Coastal belt <100m m m >600m Distance Important buildings <250m m m >750m Distance Transportation network <100m m m >2500m Distance Land use pattern Agricultural Non reserved land, forest, Grass lands, Environmental - Homesteads, Scrubs sensitive area, Gardens Build up area Developing buffer zones in the suitable area map Next the suitable area map was reclassified into three buffer zones as highly, moderately and low suitable areas for landfilling. Weights were assigned to the buffer zones using internal factors such as distance from a feature and the environmental quality and external factors using the Analytic Hierarchy Process (AHP) techniques. Considering all the criteria, the weights were calculated by using Analytic Hierarchy Process (AHP). The Analytic Hierarchy Process (AHP) is a theory of measurement through pairwise comparisons and relies on the judgments of experts to derive priority scales (Saaty, 2008). Table 2 shows relative importance among those criteria obtained by pairwise comparisons. 72

5 Table 2: Relative importance of each criteria Building Town & Villages Surface water body Transportation Network Costal Belt Land use pattern Wet land Reserves Building Town & Villages Surface water body Transportation Network Costal Belt Land use pattern Wet land Reserves Weights of each sub criteria were obtained by pairwise comparison between each sub criteria and weights (priorities) of the main criteria as percentages shown in Table 3. Table 3: Weights of sub-criteria Criteria Low suitable Moderately suitable High Suitable Priority Building Town & Village centers Surface Water Transportation Network Coastal belt Land use pattern Wetland Reserves Sum Reclassification of the suitable area into three buffer zones mentioned above, was done by using Multiple Ring Buffering tool in Arc toolbox. The buffer zones were determined for each criteria according to the sub-criteria based on distance. Weights were incorporated to GIS by adding a field to each criteria attribute table and insert weights against sub - criteria. Table 4 show the final weights assigned to each sub-criteria. 73

6 Table 4: Final weights assigned to sub-criteria Criteria Sub-criteria Suitability Weight Surface Water Body Forest reserves Wetlands Town and village centres Coastal Belt Important Buildings <100m not suitable m less suitable m moderate suitable >600m high suitable <250m not suitable m less suitable m moderate suitable m< high suitable <100m not suitable m less suitable m moderate suitable m< high suitable <500m not suitable m less suitable >2500m moderate suitable m high suitable <100m not suitable m less suitable m moderate suitable >600m high suitable <250m not suitable m less suitable m moderate suitable Transportation network Land use >750m high suitable <500m not suitable m less suitable >2500m moderate suitable m high suitable Agricultural land, Environmental sensitive area, Build up area Non reserved forests, Homesteads, Gardens not suitable - less suitable Grass lands, Scrub lands high suitable Development of the suitable area map with buffer zones The reclassified and weighted maps were combined using the union tool in ArcGIS. New field was added to its attribute table to take the total weight of single criteria maps and clipped full map to extract the suitable area using the clip tool in Arc GIS. Classification of the suitability of landfills was done according to the total weights obtained in the final map as shown in Table 5. 74

7 Table 5: Suitability of landfill sites Suitability Weight range Low suitable Moderately suitable High suitable Result and discussion Figure 1 shows the suitable area map with buffer zones for each criteria. Figure 2 shows the final suitable area map with buffer zones considering all criteria. Three different considerable large sites was obtained for the Galle MC as shown in Figure 2. Site A is moderately suitable for landfilling. Also that is the location of existing dumping site of Galle municipal council. Therefore existing dumping site is moderately suitable for landfilling. Site B is low suitable and Site C is high suitable for landfilling. Figure 1(a): Suitable area map with buffer zones for each criteria 75

8 Figure 1(b): Suitable area map with buffer zones for each criteria A B C Figure 2: Final suitable area map with buffer zones 5.0 Conclusion This study describes how to integrate the GIS technique and Analytic Hierarchy Process (AHP) to select appropriate sites for the disposal of municipal solid wastes in the Galle municipal council area. The study also confirms the ability of GIS as a viable tool for decision making in the field of Environmental Science and Engineering. This methodology is applicable for any other area. The site selection could be made more environmentally friendly by incorporating additional criteria according to the available guidelines. Acknowledgements This work was supported by the research grant from the JST/JICA Science and Technology Research Partnership for Sustainable Development (SATREPS). 76

9 References Mornya, A; Majid,R; Yola, L(2010). Identification of Landfill Sites by Using GIS and Multi-Criteria Method in Batam, Indonesia. 3rd International Graduate Conference on Engineering, Science and Humanities (IGCESH) Universiti Tekologi Malaysia, 2010 Babalola, A; Busu, I(2010). Selection of Landfill Sites for Solid Waste Treatment in Damaturu Town-Using GIS Techniques. Journal of Environmental Protection, 2011, 2, 1-10 Central Environmental Authority (CEA), Ministry of Environment & Natural Resource. Technical Guidelines on Solid Waste Management in Sri Lanka. (available onlinehttp:// [accessed on 09/25/2013]) Environmental Protection Authority(2006). Landfill Manual on Site Selection, (available onlinehttp:// [accessed on 05/22/2013]) Environmental Protection Authority(1996). Environmental Guidelines: Solid waste landfills,(available-online [accessed on 09/25/2013]) Jayawickrama, N.T. and Weerasinghe, V.P.A., GIS application in locating suitable site for solid waste landfill Mohd Din M.A, (2008). Identification of landfill site using GIS and multi criteria method in Klang, Malaysia. Saaty, T.L. (2008). Decision making with the analytic hierarch process. Int. J Service Sciences, I(1),