AASCIT Journal of Environment 2017; 2(2): 23-33 http://www.aascit.org/journal/environment ISSN: 2381-1331 (Print); ISSN: 2381-134X (Online) Keywords Landfill, Selection, Site, GIS, MCDA, Akure Received: March 9, 2017 Accepted: March 29, 2017 Published: June 13, 2017 Integration of Geographical Information System and Multicriteria Decision Analysis for Landfill Site Selection in Akure, Nigeria Olajire Olabanji Olatona 1 , Ojeh Vincent Nduka 2, * 1 African Regional Centre for Space Science and Technology Education-English, Obafemi Awolowo University, Ile-Ife, Nigeria 2 Institute of Foundation Studies, Federal University, Otuoke, Yenagoa, Nigeria Email address [email protected] (Ojeh V. N.) * Corresponding author Citation Olajire Olabanji Olatona, Ojeh Vincent Nduka. Integration of Geographical Information System and Multicriteria Decision Analysis for Landfill Site Selection in Akure Nigeria. AASCIT Journal of Environment. Vol. 2, No. 2, 2017, pp. 23-33. Abstract The shortage of land for waste disposal is one of the serious and growing potential problems in most large urban areas. Although there are some efforts to reduce and recover the waste, disposal in landfills is still the most common method for waste destination. An inappropriate landfill site may have negative environmental, economic and ecological impacts. Therefore, it should be selected carefully by considering both regulations and constraints on other sources. In Nigeria solid wastes are frequently dumped haphazardly in inappropriate locations. This study identifies suitable sites appropriate for solid waste landfill in Akure South local government of Ondo State using the integration of Multi-Criteria Decision Analysis (MCDA) and Geographical Information System (GIS). GIS was used in integrating various layers of information to produce a suitability map for solid waste landfill. The process requires the input of multiple criteria and each of which have some level of importance. Multi-Criteria Decision Analysis especially Analytical Hierarchy Process was used to identify the significant role of each criteria in the analysis. Six (6) criteria were considered and were used as input map layers and they include land use, slope, drainage, road network, geology and lineament. Each criteria was ranked according to their level of importance using pairwise comparison method. Weighted overlay tool in ArcGIS was used to produce the final suitability map. Out of the 329.79km 2 area of Akure South Local government, 45.92km 2 (≈14%) of the area was discovered to be most suitable for siting landfill. The map has four (4) categories; most suitable, suitable, less suitable and not suitable. At the end of the analysis, potential landfill sites are determined for Akure south Local government. 1. Introduction Disposal of waste in landfill is an inevitable part of a solid waste management system. Most municipal waste generated in Nigeria is disposed in landfills. Nigeria with a population growth rate of about 2.8% per annum and urban growth rate of about 5.5% per annum (Imam et al., 2008) generates about 20kg of solid waste per capita every year (Olaleye and Sangodina, 2000). Also, solid waste generated by an average Nigerian per day is estimated to be around 0.49kg while commercial centres and households
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AASCIT Journal of Environment
2017; 2(2): 23-33
http://www.aascit.org/journal/environment
ISSN: 2381-1331 (Print); ISSN: 2381-134X (Online)
Keywords Landfill,
Selection,
Site,
GIS,
MCDA,
Akure
Received: March 9, 2017
Accepted: March 29, 2017
Published: June 13, 2017
Integration of Geographical Information System and Multicriteria Decision Analysis for Landfill Site Selection in Akure, Nigeria
Olajire Olabanji Olatona1, Ojeh Vincent Nduka
2, *
1African Regional Centre for Space Science and Technology Education-English, Obafemi
Awolowo University, Ile-Ife, Nigeria 2Institute of Foundation Studies, Federal University, Otuoke, Yenagoa, Nigeria
Citation Olajire Olabanji Olatona, Ojeh Vincent Nduka. Integration of Geographical Information System
and Multicriteria Decision Analysis for Landfill Site Selection in Akure Nigeria. AASCIT Journal
of Environment. Vol. 2, No. 2, 2017, pp. 23-33.
Abstract The shortage of land for waste disposal is one of the serious and growing potential
problems in most large urban areas. Although there are some efforts to reduce and
recover the waste, disposal in landfills is still the most common method for waste
destination. An inappropriate landfill site may have negative environmental, economic
and ecological impacts. Therefore, it should be selected carefully by considering both
regulations and constraints on other sources. In Nigeria solid wastes are frequently
dumped haphazardly in inappropriate locations. This study identifies suitable sites
appropriate for solid waste landfill in Akure South local government of Ondo State using
the integration of Multi-Criteria Decision Analysis (MCDA) and Geographical
Information System (GIS). GIS was used in integrating various layers of information to
produce a suitability map for solid waste landfill. The process requires the input of
multiple criteria and each of which have some level of importance. Multi-Criteria
Decision Analysis especially Analytical Hierarchy Process was used to identify the
significant role of each criteria in the analysis. Six (6) criteria were considered and were
used as input map layers and they include land use, slope, drainage, road network,
geology and lineament. Each criteria was ranked according to their level of importance
using pairwise comparison method. Weighted overlay tool in ArcGIS was used to
produce the final suitability map. Out of the 329.79km2 area of Akure South Local
government, 45.92km2 (≈14%) of the area was discovered to be most suitable for siting
landfill. The map has four (4) categories; most suitable, suitable, less suitable and not
suitable. At the end of the analysis, potential landfill sites are determined for Akure south
Local government.
1. Introduction
Disposal of waste in landfill is an inevitable part of a solid waste management system.
Most municipal waste generated in Nigeria is disposed in landfills. Nigeria with a
population growth rate of about 2.8% per annum and urban growth rate of about 5.5%
per annum (Imam et al., 2008) generates about 20kg of solid waste per capita every year
(Olaleye and Sangodina, 2000). Also, solid waste generated by an average Nigerian per
day is estimated to be around 0.49kg while commercial centres and households
24 Olajire Olabanji Olatona and Ojeh Vincent Nduka: Integration of Geographical Information System and Multicriteria
Decision Analysis for Landfill Site Selection in Akure, Nigeria
contribute almost 90% of the total waste found in urban
centres (Solomon, 2009).
In Nigeria, open or uncontrolled dumping is largely used
as waste disposal method but the benefit of sanitary landfill
over the open dumping methods cannot be overemphasized
because it is pollution-free thereby eliminating any health or
environmental risk that may result from solid waste disposal
(UN-HABITAT, 2010). The process of solid waste disposal
management mainly consists of collection, processing,
recycling and disposing. At present, waste disposal in most
cities in Nigeria is done in form of landfill disposing.
Landfill siting is a complex process involving the processing
of massive amounts of spatial data.
Geographical Information System (GIS) is a digital
database management system that is ideal for advanced site-
selection studies because it can efficiently store, retrieve,
analyse and display information according to user-defined
specifications (Kao and Lin, 1996, Sener et al., 2006 and
Shamshiry et al., 2011). Multi-Criteria Decision Analysis
(MCDA) is a set of systematic procedures for analysing
complex decision problems. These procedures include
dividing the decision problems into smaller more
understandable parts; analysing each part; and integrating the
parts in a logical manner to produce a meaningful solution
(Malczewski, 1997). The integration of GIS and MCDA
provides a reliable platform for solving the landfill site
selection problem, because GIS provides efficient
manipulation and presentation of the data and MCDA
supplies consistent ranking of the potential landfill areas
based on a variety of criteria.
2. Study Area
Akure, the capital city of Ondo State, Nigeria is located on
latitude 7.25°N and longitude 5.20°E (Figure 1). Akure is a
city in South-West Nigeria and capital of Ondo State. Akure
produces cocoa, wood, cassava and palm-oil. The city is
surrounded by extensive tracts of tropical forest reserves and
supports a large timber industry. Akure is connected by road
and water to other Nigerian cities. The city also has an
airport. The city is the site of the Federal University of
Technology Akure, Ondo State founded in 1981. Akure is a
tourist destination and departure point for visitors to the
nearby Ose River.
According to the Koppen classification scheme, Akure lies
within the AF climate type characterized by short dry season
with precipitation not less than 60mm at its driest. This area
is located within the rainforest climate region and is
characterized by average annual temperature is 25°C
temperature near the equator varies little over the course of a
year, so rain forest temperatures are about the same year
round; the average minimum monthly temperature in a rain
forest is about 18°C. Rainforests can average as little as 1.8m
(6 ft.), or as much as 9.0m (30 ft.) of rainfall a year. Every
month, typically more than 100mm (4 in) of rain falls. If a
rainforest does have dry periods, they are usually short and
unpredictable. Though, Akure lies between the tropical rain
forest and guinea savanna type climate belt but is typically
classified under the tropical rainforest belt.
Figure 1. Location map of Akure showing the City centre (1) and Airport (2) sites. Inset (top left and right) are photos of the sites, while bottom left shows
Akure in Nigeria and Nigeria in Africa.
AASCIT Journal of Environment 2017; 2(2): 23-33 25
3. Materials and Methods
3.1. Data Used
The data that was used include the Landsat 8 imagery
classification was carried out on the imagery using
supervised classification.
3.2. Spatial Multicriteria Decision Analysis
Decision Analysis is a set of systematic procedures for
analysing complex decision problems. These procedures
include dividing the decision problems into smaller more
understandable parts; analysing each part; and integrating the
parts in a logical manner to produce a meaningful solution
(Malczewski, 1997). In general, MCDA problems involve six
components (Keeney and Raiffa, 1976; Pitz and McKillip,
1984):
a. A goal or a set of goals the decision maker want to
achieve,
b. The decision maker or a group of decision makers
involved in the decision making process with their
preferences with respect to the evaluation criteria,
c. A set of evaluation criteria (objectives and/or physical
attributes)
d. The set of decision alternatives,
e. The set of uncontrollable (independent) variables or
states of nature (decision environment)
f. The set of outcomes or consequences associated with
each alternative attribute pair.
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 (Dodgson, 2000).
There are various types of spatial multi-Criteria decision
analysis, they include simple addictive weighting, analytical
hierarchy process, the value/utility function method, the ideal
point method, outranking method, ordered weighted average,
goal programming and compromise programming. The
method adopted for this study is the analytical hierarchy
process.
3.3. Analytical Hierarchy Process (AHP)
The AHP developed by Saaty (1980) is a technique for
analysing and supporting decisions in which multiple and
competing objectives are involved and multiple alternatives
are available. The method is based on three principles:
decomposition, comparative judgment and synthesis of
priorities.
In the AHP, the first step is that a complex decision
problem is decomposed into simpler decision problems to
form a decision hierarchy (Erkut and Moran, 1991). When
developing a hierarchy, the top level is the ultimate goal
of the decision. The hierarchy decreases from the general
to more specific until a level of attributes are reached.
Each level must be linked to the next higher level.
Typically a hierarchical structure includes four levels:
goal, objectives, attributes and alternatives. The
alternatives are represented in GIS database. Each layer
consists of the attribute values assigned to the alternatives
(cell or polygon) which are related to the higher level
elements (attributes).
Once decomposition is completed, cardinal rankings for
objectives and alternatives are required. This is done by using
pairwise comparisons which reduces the complexity of
decision making since two components are considered at a
time. It involves 3 steps: (1) development of a comparison
matrix at each level of hierarchy (2) computation of weights
for each element of the hierarchy and (3) estimation of
consistency ratio.
The final step is to combine the relative weights of the
levels obtained in the above step to produce composite
weights. This is done by means of a sequence of
multiplications of the matrices of relative weights at each
level of the hierarchy. The weighted overlay tool in ArcGIS
was used to achieve this and the final output map are
classified into not suitable, suitable and most suitable sites.
4. Result and Discussions
4.1. Land-Use
The supervised image classification carried out resulted
in the land use map of Akure. From the imagery, five land
use types were generated which include the built up areas,
bare surfaces, light vegetation (which would include farm
lands, pasture, grass lands, derived savannah, and light
forest), dense forest and rocky areas. The suitability map
for land-use was then generated by reclassify the land-use
imagery.
Table 1. Land use type by Ranking.
Land-use Types Ranking
Built up 0
Bare Surface 1
Light Vegetation 5
Dense Vegetation 3
Rocks 0
26 Olajire Olabanji Olatona and Ojeh Vincent Nduka: Integration of Geographical Information System and Multicriteria
Decision Analysis for Landfill Site Selection in Akure, Nigeria
Figure 2. Land-use Maps of Akure.
4.2. Slope
The slope map was generated from Digital Elevation
Model (DEM) using the Shuttle Radar Topography Mission
(SRTM) imagery. The distribution of slope values in the
study area ranges between 0 and 60°. There are many
suggestions about slope in various literature. As stated by
Allen (2002) and Oweis et al. (1990) and applied in this
study, areas with slopes greater than 15° should be avoided
for a waste dump site.
Table 2. Slope Degree and Ranking.
Slope Ranking
0-5 5
5.1-10 3
10.1-15 1
> 15 0
AASCIT Journal of Environment 2017; 2(2): 23-33 27
Figure 3. Slope map of Akure.
4.3. Road Network
The road network was digitised from google earth
imagery. The road contains minor and major roads. By
considering suggested values from past literatures, the
distance from road and related rankings are determined for
the road network.
Table 3. Road Distance and Ranking.
Distance to Road Rankings
0-250 4
251-500 2
> 500 0
28 Olajire Olabanji Olatona and Ojeh Vincent Nduka: Integration of Geographical Information System and Multicriteria
Decision Analysis for Landfill Site Selection in Akure, Nigeria
Figure 4. Road network class in Akure.
4.4. Drainage
The drainage pattern was generated from the Shuttle Radar
Topography Mission (SRTM) Imagery using hydrology
analysis tool in ArcGIS. The necessary buffer distances to
drainage are determined as 250m, 500m and above 500m.
The buffer distances were created for the drainage and
divided into three classes.
Table 4. Distance to drainage and Ranking.
Distance to Drainage Ranking
0-250 0
251-500 2
>500 4
AASCIT Journal of Environment 2017; 2(2): 23-33 29
Figure 5. The drainage pattern classes.
4.5. Lineament
Lineament is one of the most important criterion for site
selection. As contaminants can be strongly influenced by
fracturing or by an interconnected series of solutions
openings, these may provide pathways for easier flow (Lee
2003; Sener et al., 2005). Lineaments analyses of basin were
made using Shuttle Radar Topography Mission (SRTM)
satellite images. Safe distance information are compiled from
related literature. According to the calculations, the areas that
are 0–250 m away from the lineaments have the lowest
weight values, but those > 500 m from the lineaments have
the highest weight values.
30 Olajire Olabanji Olatona and Ojeh Vincent Nduka: Integration of Geographical Information System and Multicriteria
Decision Analysis for Landfill Site Selection in Akure, Nigeria
Figure 6. Lineament Distances/Classes.
4.6. Geology
There are two types of geological formation in Akure. The
migmatite gneiss and granite gneiss are the geology types
present in Akure. They are not easily affected by weathering
but are rough on the surface (Ademeso, 2009). The geology
types where ranked according to their suitability for waste
dump site selection.
Table 5. Geology class and ranking.
Geology Type Ranking
Granite Gneiss 2
Migmatite Gneiss 4
AASCIT Journal of Environment 2017; 2(2): 23-33 31
Figure 7. Geology Maps/Class of Akure.
4.7. Selected Sites
The various factor for identifying a suitable location for
waste dump site were inputted into the GIS environment. The
maps for the factors were reclassified to make them suitable
for the overlay analysis. Weighted overlay was performed on
the various factor and the final result for the selected sites
was generated. The weighted overlay was performed on the
factors based on the importance ranking generated from oral
interview to experts. Out of the 329.79km2 area of Akure
South Local government, 45.92km2 area was discovered to
be most suitable for siting landfill.
32 Olajire Olabanji Olatona and Ojeh Vincent Nduka: Integration of Geographical Information System and Multicriteria
Decision Analysis for Landfill Site Selection in Akure, Nigeria
Figure 8. Landfill Suitability map of Akure.
Table 6. Landfill suitability map and ranking.
CRITERIA RANKING
Settlement 26
Lineament 21
Drainage 21
Geology 16
Slope 11
Road 5
5. Conclusion
The study examined the integration of geographical
information system and multicriteria decision analysis for
landfill site selection in Akure South Local Government. The
study demonstrates that GIS and MCDA are veritable tool for
the selection of appropriate landfill locations which is needed
for sustainable urban waste management.
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