Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya

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1 Journal of Earth Science and Engineering 4 (2014) doi: / X/ D DAVID PUBLISHING Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya Titus Mugi Ng ang a 1, Wachira Peter Muturi 2, Kimenju John Wangai 3, Wango Tim Joash 4 and Ndungu Joseph Matheri 5 1. Department of Geospatial and Space Technology, University of Nairobi, Nairobi, Kenya 2. School of Biological Sciences, University of Nairobi, Kenya 3. Department of Plant Science and Crop Protection, University of Nairobi, Kenya 4 Department of Geomatic and Geospatial Information Systems, Jomo Kenyatta University of Science and Technology, Nairobi, Kenya 5. Department of Geospatial and Space Technology, University of Nairobi, Nairobi, Kenya Received: October 5, 2014 / Accepted: October 28, 2014 / Published: November 25, 2014 Abstract: Solid waste dumping is a hectic problem in urban and developing areas due to shortage of land for the purpose. The main objective of this study was to select potential areas for suitable solid waste dumping for Kajiado County, Kenya. Eight input map layers including DEM (digital elevation model), topography, urban settlement, roads, wetlands, rivers, forests and protected areas were prepared and MCDA (Multi Criteria Decision Analysis Methods) were implemented in a GIS (geographic information systems) environment. GIS, RS (remote sensing) and MDCA are powerful tools which can effectively be applied during the planning phase of solid waste management in order to avoid adverse catastrophes in future. The final suitability map was prepared by weighted overlay analyses and leveled as the most suitable, moderate suitable, less suitable and unsuitable areas. The area of each suitability level was calculated using spatial statistics. Polygons representing the most suitable sites were further analyzed in terms of area perimeter ratio in order to investigate the most suitable areas in terms of shape regularity. The leading four polygons considered were marked A, B, C, D respectively in the final map. This study showed that suitable areas for solid waste landfills were limited and scattered in the study area. Key words: Solid waste dumping, geographic information system, remote sensing, multi criteria decision analysis. 1. Introduction 1.1 Landfilling Wastes are substances which are potentially hazardous to human health and/or the environment. As such, they typically require special disposal techniques to eliminate or reduce the hazards they pose [1]. Landfilling is the process that the solid wastes which cannot be recycled or further used are placed in a landfill [2]. Landfill operations are often blamed for causing Corresponding author: Titus Mugi Ng ang a, MSc, research field: geospatial science and remote sensing. titusngng@yahoo.com. external costs to nearby residents who perceive risks associated with traffic, noise, dust, litter, unattractive neighborhoods, groundwater contamination and hazardous waste pollution, among others, to be associated with landfill [3]. Landfilling is the only management technique that is both necessary and sufficient. Some wastes are simply not recyclable, because they eventually reach a point at which their intrinsic value is dissipated completely [4]. Landfill is the only easy and cost effective management system used in many parts of the world to dispose solid wastes [5]. Other methods of waste disposal are commonly referred to as the three Rs (reduce, reuse and recycle). In Kenya, only Nairobi County has a

2 694 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya near comprehensive solid waste landfill. With the devolution of government operations, there is crucial need to strategize on suitability of dumping sites in each county, especially due to the high urbanization and population growth within counties, including Kajiado. Solid waste management may be defined as the discipline associated with the control of generation, storage, collection, transfer and transport, processing and disposal of solid wastes [4]. The major goal of the landfill site selection process is to ensure that the disposal facility is located at the best location possible with little negative impact to the environment or to the population [6]. Proper landfill site selection is the fundamental step in sound waste disposal and the protection of the environment, public health and quality of life. It determines many of the subsequent steps in the landfill process, which, if properly implemented, should ensure against nuisances and adverse long-term effects [7]). GIS (geographic information systems) are ideal for preliminary site selection studies because it can manage large volumes of spatially distributed data from a variety of sources and efficiently store, retrieve, analyze and display information [6]. Local governments generally lack sufficient funds and experts to implement a complete siting process that causes significant damage to the environment [8]. GISs and environmental models function with a board spectrum of geospatial data are used for divers applications and spatial analyses at different scales. The examination and organization of data into a useful form produce information, which then enables appropriate analysis and modeling [9]. Numerous criteria must be taken into consideration in the landfill sitting and weights must be assigned to each of them [10, 11]. Many factors must be incorporated into landfill siting decisions and GIS is ideal for these preliminary studies due to its ability to manage large volumes of spatial data from a variety of sources [6]. 1.2 Spatial MCDA and GIS Decision analysis is a set of systematic procedures for analyzing complex decision problems. MCDA is used to deal with the difficulties that decision-makers encounter in handling large amounts of complex information. The principle of the method is to divide the decision problems into smaller more understandable parts, analyze each part separately and then integrate the parts in a logical manner thereby produce a meaningful solution [12]. MCDA techniques can be used to identify a single most preferred option, to rank options, to list a limited number of options for subsequent detailed evaluation, or to distinguish acceptable from unacceptable possibilities [13]. The integration of GIS and MCDA is a powerful tool to solve the landfill site selection problem, because GIS provides efficient manipulation and presentation of the data while MCDA supplies consistent ranking of the potential landfill areas based on a variety of criteria [14] Spatial multi-criteria approaches have the potential to reduce the costs and time involved by narrowing down the potential choices based on predefined criteria and weights [15]. One of the MCDA techniques mostly applied in planning is the AHP (analytical hierarchy process). AHP provides a hierarchical structure by reducing multiple variable decisions into a series of pair comparisons and develops subjective priorities based upon user judgment [16]. By creating a ratio matrix, AHP uses pair wise comparison to allocate weights to the elements of each level, measure their relative importance and finally calculate overall weights for evaluation [17]. AHP is a technique for analyzing and supporting decisions in which multiple and competing objectives are involved and multiple alternatives are available [18]. First, the comparison matrix is squared and the row sums are calculated and normalized for each row in the comparison matrix. This process is continued when the difference between the normalized weights of the iterations become smaller than a prescribed value [19].

3 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya 695 AHP has widespread use due to its flexibility. It is also incorporated into GIS environment [20-22] and can be used in two distinctive ways within GIS to derive weights and combine them with attribute map layers and to aggregate the priority for all levels of the hierarchy structures. In addition, the AHP can even be implemented in spreadsheet environment [23]. GIS tools are applicable for site suitability assessment and provide results in a good manner with high accuracy [24, 25]. As the landfill site selection process depends on a variety of laws, regulations and factors, large volume of spatial data should be evaluated and processed [26, 27]. GIS has a high capability of managing large amounts of data, as well as changes in the data [28]. The GIS analytical tool is useful in checking spatial parameters (criterion attributes) imposed in site selection process [2]. Landfill siting is a difficult, complex, tedious, and protracted process requiring evaluation of many different criteria [29]. Manually performing such a spatial analysis with drawing tools is generally tedious [30]. 2. Methodology 2.1 The Study Area The Kenya District 1998 boundaries acquired from ILRI (International Livestock Research Institute) were added into Arcmap 10.1 and Kajiado County boundary was extracted through clipping. Kajiado County boundary map was thus extracted and was found to lie between 1 31'16" S, 36 49'57" E and 3 12'22" S, 37 52'15" E. Similar extractions for layers was done and overlayed to the Kajiado County boundary resulting into the map of study area (Fig. 1). These layers included roads, rivers, wetlands, protected areas, forests and towns. Kajiado County is located in the southern part of the former Rift Valley Province. It borders the Republic of Tanzania to the southwest, Taita Taveta District to the southeast, Nairobi City to the northeast, Kiambu District to the north and Narok District to the west [31]. The eastern boundary is formed by the Chyulu Range and western limit of Tsavo National Park [32]. The impact of population growth and the consequent increasing demands for productive agricultural land is felt by pastoralists as well as by farmers [33]. 2.2 Methods Bagchi et al. [34] and Tchobanoglous et al. [35] stated that landfills should be located a certain distance from the features such as lakes, ponds, rivers, wetlands, flood plain, highway, critical habitat areas, water supply, well and airports. Most of data used for the study was secondary data acquired from ILRI website, books and journals. In this study, the approach was to utilize models that combine and integrate maps to determine an optimal landfill sitting. Accordingly, six major GIS spatial operations were performed to achieve the objective. These are multiple ring buffering, overlaying, clipping, and querying. Kajiado County solid waste disposal site selection was done using Multi Criteria Decision Evaluation and creating layers to yield a single output map. The weights were developed by providing a series of pair wise comparisons of relative importance. Based on experience and likely impact on surrounding environment, different weights were assigned to all the parameters. AHP was used to produce the weights. These criteria were developed by referring to different sources from various literatures. The results of pair-wise comparison results were put into a comparison matrix (Table 1). The matrix was populated with values from 1 to 9 for whole numbers from 1/9 to 1/2 for fractions. The weights calculated from each column were summed and every element in the matrix was divided by the sum of the respective column and the first eigenfactor was computed. This process was iterated twice and the second eigenfactor for each layer was computed. The second eigenvector was used to

4 696 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya Fig. 1 Study area Kajiado County.

5 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya 697 Table 1 The comparison matrix for the landfill site selection. Urban Slope Road River Wetland Protected areas Forest Urban Slope 1/ Road 1/9 1/ River 1/7 1/5 1/ Wetland 1/6 1/4 1/5 1/ Protected 1/3 1/5 1/2 1/3 1/3 1 2 Forest 1/2 1/4 1/3 1/2 1/2 1/2 1 Table 2 First and second eigenvectors and weights derived by calculating the principal eigenvector of pair wise comparison matrix. Factor First eigenvector Second eigenvector Percentage (%) Urban Slope Road River Wetland Protected Forest Table 3 Suitability criteria. Suitability Unsuitable (1) Less suitable (2) Moderate suitable (3) Most suitable (4) Distance from urban 0-2,500 m 2,500-5,000 m 5,000-7,500 m Over 7,500 m Percentage slope Over 20% 15%-20% 10%-15% Less than 10% Distance from roads m 500-1,000 m 1,000-1,500 m Over 1,500 m Distance from rivers/wetlands m 500-1,000 m 1,000-1,500 m Over 1,500 m Distance from protected areas/forests m 750-1,500 m 1,500-2,250 m Over 2,250 m compute the percentage weight for each factor that contributed to the solid waste suitability analysis (Table 2) Production of Input Data Various suitability criteria (multicreria) were applied to derive the suitability maps as summarized below (Table 3) Suitable Distance from Main Roads to Solid Waste Dumping Site Although landfills should have suitable transport access, they should not be located within 100 meters of any major highways, city streets or other transportation routes. Twumasi et al. [36] recommended a distance of 300 meters. As the general concept, the landfills shall not be located within 100 m of any major highways, city streets or other transportation routes. Due to the trend of urbanization and human settlements along major transport infrastructures in Kenya, the roads network layer was considered for analysis. Areas measuring below 500 m were considered unsuitable for solid waste dumping site, less suitable between distances from 500 m to 1,000 m. The distance starting from 1,000 up to 1,500 was considered as moderate suitable and highly suitable distance is beyond 1,500 m Suitability Analysis of Distance to Rivers, Lakes/Wetlands The farther lands from lakes and river banks and wetlands got more preferences for solid waste dumping site suitability. In Kajiado County, there is notably Lake Magadi. Other smaller lakes include Lake Natron, Lake Amboseli, Lake Kwenia and Ziwa Kambe. Swamps and rivers were also found to be ample in

6 698 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya Kajiado County. Areas measuring below 500 m were considered unsuitable for solid waste dumping site, less suitable between distances from 500 m to 1,000 m. The distance starting from 1,000 m up to 1,500 m was considered as moderate suitable and highly suitable distance. The same criterion was also applied for other water sources such as lakes/wetland Suitability of Slope According to Sener et al. [37] and Leao et al. [38], the land with a slope less than 10% is highly suitable for solid waste dumping. According to Lin [39], the appropriate slope for constructing a landfill is about 8%-12%, because too steep of a slope would make it difficult to construct and maintain and too flat of a slope would affect the runoff drainage. High slopes can favour leachate drainage to flat areas and water bodies and cause contamination. Areas with high slope are unsuitable for solid waste disposal due to lack of waste containment thus leading to the release of the waste material into the surrounding area. Slope map was generated from digital elevation model. The slope map was then reclassified into four categories just like other factors. Areas whose percentage slope was over 20% was classified as unsuitable, between 15% to 20% less suitable, 10% to 15% moderate suitable and less than 10% the most suitable (Fig. 2) Suitability of Urban Settlement Solid waste disposal creates a problem primarily in high populated areas [40]. The landfill should be situated at a significant distance away from urban residential areas due to public concerns [41] especially health concerns [42]. According to the environment protection agency [43], a landfill site should be located in an area which is at least 500 meters from an urban residential or commercial area. Landfills often attract large numbers of birds, thus increasing the risk to public health by spreading scavenged items away from the landfill facility [44]. Siddiqui et al. [6] suggests that no new landfill site should be located closer than 0.4 km from a collection of ten or more houses. Urban settlement areas were classified according to their suitability. The study considered the reclassified distances as unsuitable from 0 to 2,500 m, less suitable between 2,500 m and 5,000 m, moderate suitable from 5,000 m to 7,500 m and suitable beyond 7,500 m for the urban areas. This is due to the fact that as all counties around Nairobi are fast growing, there is need to give distance away from urban settlement priority. A point in mind is Nairobi County dumping site whereby proposals have been done to move it even outside the county Suitable Distance from Protected Areas and Forests A landfill must not be located in close proximity to sensitive areas. For example, areas gazetted for special protection would be excluded. However, EPA [43] recommends that a buffer within the landfill of at least 500 meters width should be provided and maintained around the site. In Kajiado County, areas were identified as Ngong Hills, the Amboseli, Loitoktok, Namanga Hills, Tsavo West and the Chyulu Hills. Other protected areas like forests and water sources were analysed separately. The landfill should not be located in close proximity to sensitive areas listed above to limit of 2,250 m buffer. When the distance increases the suitability also increases. Areas beyond 2,250 m were considered to be the most suitable area for solid waste dumping site. The same scale was used for forests since forests, as well, are protected areas. 3. Results The resultant vector layers were converted to raster format using the Vector-To-Raster conversion tool in ArcGIS This was done in order to necessitate analysis later with the slope dataset as well as due to the fact that weighted sum overlay analysis works on rasters as opposed to vector data. This overlay resulted into a raster map. Reclassification using the Quantile option in Arcmap 10.1 of the resultant weighted sum raster was

7 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya 699 done to produce leveled suitability map for the solid waste disposal site in Kajiado County. The area of each suitability level was calculated using the spatial statistical tool utility in Arcmap 10.1 resulting into a total of 3, km 2 unsuitable sites (1), 6, km 2 less suitable sites (2), 6, km 2 moderate suitable sites (3) 5, km 2 most suitable sites (4) (Fig. 2). Polygons representing the most suitable sites were further analysed in terms of area perimeter ratio. This was done to investigate the most suitable polygons in terms of shape regularity. The leading four polygons were considered this ration with areas of 275,585,325 m 2, 259,623,525 m 2, 148,583,700 m 2, 132,511,700 m 2 and highlighted as A, B, C, D respectively in the final map (Fig. 3). Fig. 2 Reclassified weighted sum overlay analysis map.

8 700 Solid Waste Dumping Site Selection Using GIS and Remote Sensing for Kajiado County, Kenya Fig. 3 Four the most suitable sites in Kajiado County. 4. Conclusion Despite the complexity associated with the selection of suitable areas for solid waste dumping, the integration of GIS and MCDA is a powerful technique to solve the problem. GIS has the capacity to process large volumes of spatial data associated with solid waste site selection process. MCDA supplies consistent ranking of the potential landfill areas based on a variety of criteria. The study succeeded in identifying the best locations for solid waste disposal in Kajiado County, Kenya, and ranking them according to priorities. The study confirmed that GIS ability to manage large volumes of spatially distributed data from variety of sources, efficiently store, retrieve, analyze and display information. References [1] Meakin, S Hazardous Waste Management: Canadian Directions. Government of Canada:

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