ANALYSIS OF LANDCOVER AND LANDUSE CHANGES IN ABA URBAN AREA USING MEDIUM RESOLUTION SATELLITE IMAGERIES
This study focused on the analysis of landuse and landcover changes in Aba Urban Area using medium resolution satellite imageries (Landsat ETM+, 2000 and Nigeria Sat-1, 2005) acquired for Aba Township in order to detect the changes that have taken place within this time interval. Change detection being a process of identifying differences in the state of an object or phenomena by observing it at different times. In determining the landuse/cover of Aba, Remote Sensing technique was applied using the ILWIS software in image processing and analysis.
The Landuse map of the study area was produced using ArcGIS/ArcView software. Two multidate datasets (LandsatETM+ image of 2000 and NigeriaSat-1 image of 2005) respectively and analogue base map Aba township (produced in 1991) were used. The base map was scanned, digitized and georeferenced in AutoCAD environment. The digitized base map was polygonized and classified. The Landsat ETM+ and the NigeriaSat-1 imageries were resampled to one resolution and classified. Through an overlay operation the various spectral and temporal changes in Landuses were obtained and analyzed. The result reveals that from 1991, 2000 to 2005, the River increased from 15.1% to 22.1% and finally to 22.4% due partly to increasing activities within and around the waterways, Builtup area increased from 21.7% to 26.8% and to 36.5%. Unlike river and built-up area, there is a significant disparity and trend in vegetation Landcover due to rapid urbanization and socio-economic activities. Thus, vegetal cover decreased from 63.2% in 1991 to 51.1% in 2000 and in 2005 it further decreased to 41.1% However, I recommended to Government that timely Landuse and Landcover mapping of the entire Aba Township should be embarked upon to forestall the ugly consequences of erratic and haphazard land utilization in the town. It was also recommended that the government and relevant authorities to embark on conversion of analogue maps of the state at different scales to digital maps and also update them to reflect the changes and development in the state. This will facilitate necessary landuse planning and forestall the rising sprawl in urban landuse in Aba Township.
1.1 BACKGROUND OF THE STUDY
Research has proved that problems associated with environmental monitoring and
control persists through the history of mankind. But the situation is aggravated in
recent times due to man’s increasing intervention on the environment. There
remain few landscapes on the earth’s surface that have not been significantly
altered by human beings in some ways (Opeyemi, 2007).
Riebsame et al. (1994) observed that due to anthropogenic factors, the landscape is
significantly altered in some ways and man’s activities on the earth surface and his
cultural activities have produced a great influence upon the natural environment
resulting in an observable trends or patterns over a time scale. These changes in
Landuse and Landcover due to mankind’s contributions are pervasive and have
adverse implications on local, regional and global scales. Thus, according to
Igbokwe (2008) and Onu (2008), large scale transformation is commonly witnesses
in and around major cities of Nigeria.
Meyer (1995) observed that humans have an increasingly large role in the
modification of the global environment. In addition, Raddison et al. (1999) cited in
Igbokwe (2008) and Onu (2008) stated that population growth pressure forces man
to invade the undeveloped environment, hence, tampering with the Landscape and
disturbing the natural habitat.
Demographic and socio-economic factors have had increasing pressure on the
landscape as demands for food, water; shelter and fuel have increased regionally
and globally. Thus, Landuse practices are influenced by different environmental
conditions, political, climate, and demographic and social conditions.
Landcover refers to the natural surface of the earth undisturbed by human
activities. It is often used to represent vegetation, natural or man-made features and
every other visible evidence of Landuse e.g. forest, cultivated/uncultivated land,
settlements, etc. Landuse on the other hand, refers to the use of land by humans. It
is the alterations done to Landcover by human activities e.g. farming, road
construction etc. Landuse and Landcover change studies has become a key
component for managing of natural resources and monitoring environmental
changes. If we are going to manage our urban areas as systems for the betterment
of the environment, Igbokwe (2008) recommended that in Nigeria we need to gain
better understanding of the type of disturbances and changes that can occur in
urban systems. Igbokwe (2008) further stressed that landcover and landuse
information should form part of the environmental data, which are kept in the form ...Get Complete Material.
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