CHAPTER ONE – INTRODUCTION
Urbanization as a process is a universal phenomenon being experienced all over the world, anywhere humans live (Sudhira etal., 2004), and it has been observed as a major trend in recent years (Weber and Puissant, 2003).According to UN (2009), research showed that half of the world population is in urban areas. Moreover, most of the urban population growth has been in the developing countries. In some cases, the space taken up by urban areas is increasing faster than the urban population itself (Pijanowski et al, 2010).
Industrial Revolution led to the rapid expansion of cities globally and in the last 10 years, lots of attention was given to urban land use/cover change because ecosystems in urban areas are strongly affected by human activities and have close relations with the life of almost half of the world’s population (Xiao et al., 2006).
This rapid growth of urban areas has caused complex problems such as environmental pollutions; endanger natural resources, reduced open spaces, the modification of the thermal environment, unsatisfied infrastructures and unplanned or poorly planned land development
(Parka et al., 2011). It also has caused an unprecedented urban environmental degradation and inadequate urban infrastructure needed to support the population. Urban expansion is defined as modification of environment or the replacement of natural or agricultural land cover with urban land use (e.g., buildings, transportation, parking lots) (Slempet al., 2012). Urban development and expansion comes with increase in population as a major factor, because aspopulation increases, it brings up the needs for new facilities, amenities and decentralization from the urban center and valuable farmland is often left exposed as a result of activities of commercial or residential developers. These cause land use/land cover (LULC) changes. Land use/land cover (LULC) change is a key driver of global change.Noted that changes in land cover and in the way people use the land have become recognized over the last15 years as important global environmental changes in their own right. In Nigeria, several studies on LULC using maps, aerial photographs and satellites imagerieshave been documented. Also, it was reported that several factors such as agricultural colonization, spread of rural settlements, and evolution of rural road networksand governmenthave modified the original form of land cover in Nigeria.
This is also the case in Akure where urbanization, housing development, agriculture and deforestation are the driving factors of land cover change and in extension to urban sprawl. The effect of these changes can be seen on the population growth, land consumption rate and local climate (Owoeye and Akinluyi, 2018). The expansion in the urban status of Akure has caused the depletion of natural resources and also contributed tothe deterioration of the environment due to incompatible changes in land use pattern (Oyinloye, 2013).Agriculturally productive land and forestland are being converted to residential and other private and public uses.
Balogun et al., (2011) in their argument state that the land use land cover pattern of a region is an outcome of natural and socio-economic factors and their utilization by man in time and space. Hence, the uncontrolled growth of urban development of Akure has adversely affected its ecosystem which may indirectly reflect on weather parameters with eventual local climate modification (Akinbode et al.,2007).
Urban sprawl is an adverse effect of urban expansion if not managed properly, it comes up as an unplanned, undisturbed monotonous developments that does not provide for a functional mix of uses and which variously appears as low-density, ribbon or strip, scattered, leapfrog discontinuous development, hot and inefficient use of land. According to Glaeseret al (2001), urban sprawl as a pattern in an urbanized area that exhibits some combination of eight distinct dimensions such as density, continuity, concentration, clustering, centrality, nuclearity, mixed uses and proximity. These dimensions eliminate agricultural lands, pollute water quality, increase the landsurface temperature and cause air pollution.Covering the earth surfaces with construction materials like concretes and asphalts, for example buildings and paved roads, the areas as a result have a higher absorption of solar radiation and greater thermal conductivity and capability for emitting the heat stored during the day and night. This came up as a process of urbanization which changed the natural landscape of the earth.
Remote sensing technology makes the assessment and management of an urban area efficient. It serves as a reliable source of thematic maps such as those that represent land cover as it provides the representation of the Earth’s surface on a map with consistent spatial features, as well as available at a range of spatial and temporal scales (Giles, 2002). UrbanPlanners frequently make use of remotely sensed imagery, which they can overlay on other demographic or geographic information to provide a more detailed and insightful picture of the human landscape (Carlson, 2003).Few studies provided enough consideration to urbanexpansion and linked directly to its impact on natural resources and community character; however a lack of quality land use/cover maps for successful management and monitoring made their work redundant in the long run.
1.2Statement of Problem
Akure-South local government as part of Akure metropolis has undergone rapid population growth, environmental changes and witnessed immense growth in the size of built-up areas, transportation and commercial activities. Within the last three decades, these have resulted in environmental deterioration and stress on the ecosystem structure, increased air pollution, water consumption, lost of wildlife, increase racial and economic disparity, increase in risk of obesity, insufficient housing facilities, insuffiÂcient infrastructure, and increasing urban climatological and ecological problems. All these were gotten from news forecast, the ministry of lands, housing and urban development in Ondo State and national agency for population program and development act. Â This study is carried out to assess these problems and how they can be solved using remote sensing and GIS techniques.
1.3 Research Questions
i.           What are the patterns of the urban expansion?
ii.           What are the effects of urban expansion on vegetation, land surface temperature?
iii.           How urban expansion modifies the land use/cover change?
1.4.1 Aim of the Study
The aim of the study is to carry out the assessment of urban expansion in Akure-South Local government area using Remote Sensing and GIS techniques.
1.4.2 Objectives of the Study
The objectives of the study are:
i.           Assessment of the Land use/land cover change in the study area between the years 1986 to 2017.
ii.           Assessment of the Land surface temperature variation for a period between 1986 to2017.
iii.           To assess the Normalized Difference Vegetation Index (NDVI) for the 30 years-period in the study area (1986-2017).
iv.           Determine patterns of the urban expansion in respect to the previous years.
1.5Justification for the Study
Akure, the state capital of Ondo state, Nigeria is undergoing rapid growth in every sense of its urban status. Ranging from its population which has tremendously increased from 157 947 in 1990 to 500 000 in 2006 (Balogunet al., 2011), the infrastructural development of the city also has been given a facelift, transportation and commercial activities have also increased.
The city serves as the administrative and economic seat to Akure South Local Government Area and Ondo State with its creation in 1976 from the old Western State. Since then, Akure South Local Government Area has seen extensive growth in the size of built-up areas, number of inhabitants, transportation, and commercial activities, especially with establishment of the Federal University of Technology, Akure (FUTA) in 1981.In the last three decades, it has experienced urban growth and expansion with respective changes in the land-atmosphere energy balance relationships which have occurred alongside traffic related, air quality degradation over the city (Balogunet al., 2011). Also the energy balance has been affected due to the increase in the number of built-up area there’s been some built up structures not adequately planned being put into place that did not follow regulations of relevant environmental agencies.
For this reason it’s crucial that a research/study is carried out to monitor, assess and evaluate the effect of this urban expansion for proper understanding and management of the environment.
1.6The Study Area
The Akure-south LGA lies within Latitudes 7º 12′ 18.04̋ N and Longitudes 5º 11′ 15.58̋E (Nothings 790820 – 809277 mN and Easting 733726 – 752139 mE, UTM Minna Zone 31). The area is located on a gently undulating terrain surrounded by isolated hills and inselbergs. The study area covers about 331 km².
Topographic elevations vary between 260 and 470 m above sea level (Owoyemi, 1996). The metropolis is drained by several streams and rivers. The major ones are Ala and Owena.
The city of Akure since it became the administrative headquarters of Ondo State in 1976 has been witnessing rapid developmental changes in terms of physical landscape, city growth and urban sprawl. In 1982 establishment of the Federal University of Technology, Akure (FUTA) has also brought about rapid and unprecedented development leading to deforestation in Akure South Local Government Area. Figure 1.1 below shows the study area.
Figure 1.1: Map of the study area
1.6.1Geology of Study Area
AkureSouth is underlain by precambian basement complex rocks of South Western Nigeria. The major types ofrocks in Akure South are theMigmatite-Gneiss-Quartzite Complex, Charnockitic and Dioritic rocks, Older Granites and Unmetamorphosed dolerite dykes. The study area exhibits varieties of structures such as foliation, schistosity, folds, faults, joints and fractures. Generally, the structural trends in the study area are NNW-SSE and NNE-SSW. Numerous small and long fractures, joints and fissure zones whichgenerally trend north-south are common.Seven principal varieties are recognized, the fine-grained biotite granite, medium to coarse grained granite rocks, porphyritic gneissmigmatite, gneiss, charnokiteand pegmatite.
Figure 1.2: Geologic map of study area
1.6.2Climate of Study Area
The climate is tropical with two distinct seasons, the rainy season, (April- October) and dry season (November – March) with slight variations from year to year. The annual rainfall is about 1500mm in the study area, the area generally enjoys luxuriant vegetation. The vegetation consists of coastal forest and mangrove swamp forest and moist lowland forest.
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