Solid wastes disposal has become a serious and challenging problem in major urban centres in Nigeria including Okigwe. The common sights of refuse that accumulates along the roads and market squares that make the road impassable to traffic are examples of the problem. Waste disposal problem often results from the inability of government and its agencies to match the collection and disposal with the generation of waste. Sometimes too, the problem could be due to lack of suitable disposal sites as against the arbitrary and illegal dumps with their attendant health hazards. Different techniques have been used to select solid waste disposal sites in various parts of the world. The aim of this study is to carried out the selection of suitable wastes disposal sites in Okigwe and its environs of Imo State using a high resolution satellite imagery and GIS technique. When remotely sensed data are used to generate a map, it assumes a new form, encourage new uses, new users and cartographic visualization can be possible. The study specified data acquired such as SPOT 5 (5m) satellite imagery of Okigwe, the 10m DEM and the Imo State Administrative map. The hardware used were laptop computer, hand-held GPS receiver, a scanner and a HP plotter. Software utilized were ArcMap 10.1, ERDAS Imagery 2014, Google Earth, Global mapper and Microsoft word, Microsoft excel and CorelDraw. The methodology included the scanning of the base map covering the study area using A0 scanner at a resolution of 300dpi in colour mode. These images were georeferenced to establish the relationship between the image coordinate system and the corresponding ground coordinates system. The images were visually analyzed to determine generic and specific characteristics of various features. Features such as roads, water bodies,streams and built up areas were extracted by one-screen vectorisation. The satellite image was enhanced and classified. The enhancement operation was done by splitting the multispectral spot image composite into individual RGB channels and then recomposing these bands by changing their group. Supervised classification method was used to classify the features. Preprocessing of DEM was done and contour interpolation from DEM was achieved and subsequently converted to TIN. This GIS operation was done using Buffer operation, exclusion and overlay operation. The result of the analysis showed that, two locations namely Ezinachi and Ugwuaka with a total area of 601.847 hectares and 4.8kms away from residential area are suitable for the location of disposal sites. They satisfied the criteria. Solid wastes disposal sites can be selected and established successfully using remote sensing data and GIS technique. This will help planners and decision makers in land use and budgeting of solid waste disposal and management. The study recommends that remotely sensed data and GIS technology be used to establish suitable disposal site rather than choosing disposal sites arbitrarily.
Keywords — Remote Sensing, GIS, solid waste, Imo State, Suitable Sites
1.1 BACKGROUND TO THE STUDY
Waste is an issue that affects us all, and the environment is heading towards a potential risk due to unsustainable waste disposal management. Selecting and managing appropriate solid waste dumping site is one of the challenging problems in developing countries due to inadequate proper solid waste management system and the type of waste thrown into the environment. It is a sensitive issue which concerns about serious environmental problems in today’s world. The present situation of direct dumping of the waste without proper inspection and separation leaves a serious impact of environmental pollution causing a tremendous growth health related problems. Also, the uncontrolled refused disposal has always been associated with serious health hazards (United Nations Centre for Human Settlement (Habitat)., 1989). For instance environmental pollution affects women more than any other group especially as regards to health and sanitation. The effects of radiation and chemicals on women have led to infertility, miscarriage, neonatal deaths, malformation and growth retardation. Worse still, this chemical now appears in woman breast milk (Agoawaike, 1992).
Furthermore, the solid waste materials in both rural and urban areas are the natural outcome of human activities. However, more predominant in cities and municipalities owing to intense activities by human and machineries. The solution therefore is the implementation of a functional and sustainable framework for proper disposal. The rapid growth of population and urbanization decreases the non-renewable resources and disposal of waste matter and toxic waste haphazardly are some of the major environmental issues posing threats to the existence of human society. The most common problems associated with improper management of solid waste include diseases transmission, fire hazard, odor nuisance, atmospheric and water pollution, aesthetic nuisance and economic losses (Basagaoglu etal; 1997).
In most of the urban cities of Imo State of Nigeria, such as Okigwe and its environs refuse heaps are left to intrude on or totally blocked roads, thereby hindering traffic flow, sometimes causing accident particularly near market or industrial areas. Solid wastes are left to block drainages and other drainage channels causing flooding on roads especially during rainy season. Furthermore, during dry season the refuse are being dispersed by wind into residential areas thereby creating unpleasant environment to the residents. Solid waste is dumped in burrow pits, at road junction, along highways, near streams and litter the roads. The preference for burrow pit for a dump site is most outdated and are not scientifically done. From the few existing dumps in Okigwe and its environs, wastes are collected and transported to more or less open disposal site in open Tippers and other waste disposal waste without any separation of the vital constituents.
It is therefore, evident that the most common form of solid waste disposal site in Imo State especially Okigwe and its environs is the crude open dumps system in the various burrow pit, natural depressions, gullies and even agricultural lands. This crude form of waste disposal which has been ongoing for several decades is not only environmental unfriendly but also present a high nuisance value and is detrimental to the health of the people living close to this site. This crude form of solid waste disposal in an area of scarce resource is unacceptable and requires that a sustainable solution based on proper planning and careful research must be adopted. There is need to properly select our landfill site and adequately managed them and make them not only sanitary but also technically and scientifically acceptable in terms of operation and efficiency, adaptable to changing condition. It is in view of the vital concern that this project is aimed at scientifically selecting a suitable site using remote sensing and GIS techniques.
GIS is a suitable tool for site selection since it has the capability to manage large amount of spatial data that comes from various sources (Kao, J., Chen, W., Lin, H. &Guo, S.,1996). Daneshvar et al. (2005) claimthat GIS is an ultimate method for preliminary site selection as it efficiently stores, retrieves analyses and displays information according to user-defined specification. However, GIS can be limited by the existing sources of data needed in siting analysis. The fundamental analytical function of a GIS based spatial decision support system include query analysis, proximity or buffer analysis, overlay analysis, neighborhood analysis and network analysis. Various combinations of these functions are commonly used during the geographical data analysis process (Besr, 2002).
1.2. Statement of the Problem
Municipal solid waste generation is among the most significant sources that threaten the global environmental health. Accordingly, it is essential that integrated systems of waste management should be considered within the path towards achieving sustainable development. Such systems generally emphasize on functional elements of waste minimization (reduction), reuse, recycle and finally placing the remained material in landfills. As sanitary landfilling is an inevitable part of municipal solid waste (MSW) management system, appropriate site selection of waste disposal may play a key role in reducing the environment contamination.
However, solid waste management system in Okigwe and its environs is not effective as wastes are seen dumped on all manner of places including roads, near sensitive areas, and on private properties. It is therefore of importance that solid waste collected are properly disposed at designated sites in the city in order to avoid environmental degradation. It has been identified that almost all solid waste generated in household was indiscriminately disposed together in Okigwe town. It is this gap in research that this study intends to fill by using GIS and Remote Sensing techniques to design and select a suitable site for solid waste disposal in Okigwe.
1.3. AIM AND OBJECTIVES OF THE STUDY
The aim of this study is to select suitable solid waste disposal sites in Okigwe and its environs of Imo State with the intention of locating suitable sites using remote sensing and GIS techniques.
To achieve the above aim, the following objectives would be pursued:
- i) To map out the study area using spot 5 imagery for the selection of solid waste disposal sites.
(ii) To determine the criteria for suitable locations as disposal sites using GIS as a tool.
(iii) To determine the capacity of the selected sites.
1.4 SCOPE OF THE STUDY
The scope of the project covered the following operations;
- Geometric data acquisition using GPS
- Attribute data acquisition
- Design and creation of spatial database using Microsoft Excel and ArcGIS Desktop 10.3
- Production of a digital map showing the selected suitable site for solid waste disposal
1.5. THE STUDY AREA
Okigwe Local Government is one of the 27 LocalGovernment Areas (LGA’s) in Imo State. It is located between latitudes 50◦56’24”N to 50 ̊ 42’19”N and longitudes70 ̊ 12’58”E to 70 ̊ 24’02”E. It is bounded to the North byOrumba South LGA of Anambra State and Umu-NneochiLGA of Abia State, to the East byIsuikwatoLGA ofAbia State and to the South by Umuahia North LGA of AbiaState, Ihitte/Uboma and Ehime MbanoLGA’s both of ImoState while Onuimo and Ideato-NorthL.G.A’s both of ImoState forms the border to the west. The Imo River forms the natural boundaries between Okigwe LGA and a few of these neighboring Local Government areas such as Onuimo andEhime MbanoLGA’s (see Fig. 1).Okigwe L.G.A is found inthe tropical rainforest region of Nigeria. It is according to (NEST 1991) the natural rainforest (Riparian forest and Lowland forest). It is drained mainly by River Imo and tributary streams. Like most towns in Nigeria, it experiences two distinct climatic seasons; namely dry (October to March) and wet (April to September) seasons. A period of cold, dry, dusty winds known as “Harmattan” occurs from December to February annually. Okigwe L.G.A has a mean temperature range between 240C to 340C with a relative humidity of 70% in dry months and 90% in wet months. The hottest months are between January and March (NIMET2009).Okigwe L.G.Ais the fourth largest LGA in Imostate of Nigeria in terms of land mass with a projected 2014population of about 169,861 people (National Population Commission NPC, 2006) unevenly distributed over a total land area of 32,037.445 hectares. Most of the population is made up of immigrant workers from other states. OkigweL.G.A shares partly with IsuikwatoL.G.A of Abia State the primary host site of the old Imo State University (now AbiaState University). Okigwe has various tourist and historicalsites.Okigwe also has a number of secondary schoolsnamely;Federal Government College Okigwe, Agbobucommunity secondary school, Community secondary schoolOkigwe, Girls secondary schoolIhube, Ihubeboys high school, Urban secondary school Ubaha, Girls secondary school Okigwe and others.
Figure 1: Map showing the study area
Source: Map digitized from the administrative map of Nigeria 2012 obtained from OSGOF
1.6. JUSTIFICATION OF THE STUDY
This research is carried out to find out a suitable site for the disposal of municipal solid waste generated from Okigwe using GIS and Remote Sensing techniques. A suitable site for waste disposal must have environmental safety criteria and attributes that will enable the wastes to be isolated so that there will be no unacceptable risk to people or the environment. Therefore, this study considers physical and socio-economic criteria and integrate them for selecting suitable sites for solid waste disposal so as to produce a final map layer in the study area. As the final map presents land suitability from less suitable to the most suitable areas for the municipal solid waste disposal, the findings from the study could be used for urban planners and decision makers to implement ecologically sound waste management scheme in Okigwe town.
The end results of the research will also show the efficacy of GIS and multi-criteria decision making method in decision making using GIS environments. In light of this, the study had both academic and practical relevance. Furthermore, the product of the study can be used by academicians, researchers, practitioners and urban decision makers either for academic purpose or decision making. If the sites for solid waste disposal that has been identified by this paper is properly used by the inhabitants, healthy and neat environment would be created.