LAND-USE AND LAND-COVER CHANGES IN PORT HARCOURT AND OBIO/AKPOR LOCAL GOVERNMENT AREAS OF RIVERS STATE - USING

REMOTE SENSING & GIS APPROACH

ByHappiness E. Ihueze*, H. U. Nwosu & Victor U. OkoronduDepartment of Environmental Engineering Technology,

University of Port HarcourtPort Harcourt, Nigeria

*happiihueze@yahoo.comAbstractLand-Use and Land-Cover changes for Port Harcourt and Obio/Akpor L.G.A.’s (Study Area) between 1986, 2000 and 2007 covering about 723.6 km2 were assessed using Remote Sensing (ENVI) Software, Geographic Information System (ArcGIS 9.3) Software and Land sat images of 30m x 30m resolution of the study area. The Land-Use types include; Farmland, Built-Up Areas, water, Open Space, Mangrove Vegetation and Forest. The area in (km2) of each land use type in each year was calculated and thereafter the change was determined by subtracting the area of the same land use type in 1986 from 2000 and 2000 from 2007. Thus, the percentage of change was therefore calculated. The study revealed that from 1986 to 2000, Built-Up Area and Mangrove Vegetation increased by 514.3% and 96.7% respectively, while Farmland, Forest, Open Space and Water Bodies decreased by 51.1%, 58%, 23.6% and 0.84% respectively. It also revealed that from 2000 to 2007, Built-Up Area, Farmland, Open Space and Water Bodies increased by 9.3%, 22.7, 11.1% and 3.6% respectively, while Forest and Mangrove Vegetation decreased by 33.5% and 87.9% respectively. Thus, it was recommended that laws should be promulgated to prevent unlawful expansion of construction of any form and that the people in the communities in the study area should be enlightened and educated on the effects of deforestation on the environment.

Key words: Arc GIS 9.3, Deforestation, ENVI, Land use and land cover images of Port-Harcourt and Obio/Akpor, Spatio-temporal assessment

INTRODUCTION The knowledge about land use and land cover has become increasingly important as the nation plans to overcome the problems of haphazard, uncontrolled development, deteriorating environmental quality, loss of prime agricultural lands, destruction of important wetlands, and loss of fish and wildlife habitat (Fasote, 2007).

Land-Use change over time is an inevitable phenomenon occurring globally due to both temporary and permanent interest of the inhabitants in a particular area (Eludoyin, 2010). The phenomenon could be revealed either in a small or large scale but the most interesting and fundamental observation is that change occurs over time in a particular place.

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Land-Use and Land-Cover changes are local and place specific, occurring incrementally in ways that often escape our attention (De-Sherbinin, 2002). Humans have been altering Land-Cover since prehistory through the use of fire to flush out game and, since the advent of plant and animal domestication, through the clearance of patches of land for agriculture and livestock (De-Sherbinin, 2002). In the past two centuries the impact of human activities on the land has grown enormously, altering entire landscapes, and ultimately impacting the earth's nutrient and hydrological cycles as well as climate.

Most major metropolitan cities face the growing problems of urban sprawl, loss of natural vegetation and Open Space and a general decline in wildlife habitat. This problem is observed when residential and commercial development replaced undeveloped land around them. Cities have changed from small, isolated population centers to large, interconnected economic physical and environmental features. According to USGS fact sheet 188-99 in 1999, one hundred years ago, approximately 15% of the world population was living in urban areas. Today the percentage is nearly 50%. Urbanization and rapid population growth cause increasing pressure on the cities in Nigeria, especially in the oil-rich south-south region of Nigeria in which communities in Port Harcourt and Obio/Akpor LGAs are inclusive, however, Braissoulis (1999) argued that Land-Use changes such as urbanization tend to radiate out from existing areas of the same class, and many models take advantage of this characteristic to make predictions of future change.

The results of the pressure are numerous and they include intensified agriculture, decreasing amount of forestland, loss of biodiversity, intensified land degradation and soil erosion (Pellika, Clark, Hurskainen, Keskinen, Lanne, Masalin, Nyman-Ghezelbash, and Sirvio, 2004). Despite this, the strong interest in Land-Use and Land-Cover results from their direct relationship to many of the planet’s fundamental characteristics and processes, including the productivity of the land, the diversity of plant and animal species, and the biochemical and hydrological cycles. In a nutshell, Land-Cover is continually transformed by Land-Use changes, suggesting that Land-Use is the cause of Land-Cover change and the underlying driving forces remain economic, technological, institutional and demographic factors (De-Sherbinin, 2002).

In addition to being a driver of earth system processes affecting climate, the carbon cycle and the ecosystem, Land-Use and Land-Cover change has a significant impact on the feedback of hydro-climatic processes on the surface hydrology (Odunuga and Oyebande, 2007). No wonder Adeniyi and Omojola (1999) in Odunuga and Oyebande (2007) viewed that an understanding of past Land-Use practices and current Land-Use and Land-Cover pattern and projections of future Land-Use and Land-Cover as affected by various factors which include population size and distribution, economic development and technology are used to determine the effects of Land-Use and Land-Cover change on the earth system. Changes in Land-Use and Land-Cover are central issues in the study of global environmental change. These changes have profound regional implications that can be left during the life span current generation, while also

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exhibiting cumulative long-term global dimensions. GIS and remote sensing are powerful tool that have been widely used for monitoring and detection of Land-Use and Land-Cover change (Anderson, Hardy, Roach, & Witmer, 2001; Musaoglu, Kaya, Seker, & Goksel, 2002; Tardie & Congalton, 2002) MATERIALS AND METHODSStudy Area: This study was carried out on the entire Local Government Areas of Port-Harcourt and Obio/Akpor.

Port Harcourt city, due to its strategic position in land and sea has become one of the fastest growing cities in Nigeria and the most industrialized in the southern part of the country. Due to this advantaged position, this urban city is becoming congested and expanding rapidly. The ambient temperature of Port Harcourt City is 27ºC during the rainy season and 37ºC during the dry and ‘harmattan’ seasons. Due to global warming, the temperature is becoming higher. The ground temperature is even higher than the ambient temperature due to the heat absorbed and therefore, requires the knowledge of soil temperature for reliable underground system distribution. Obio/Akpor Local Government Area belongs to Rivers State in the South-South region of Nigeria or otherwise known as Niger Delta Region. Obio/Akpor area is influenced by urbanization or urban sprawl whereby smaller communities have merged together and formed a mega city. The reason is due to high influx of people resulting to rapid growth of the population. This in turn is largely due to the expansion of the oil and allied industries, which have also attracted many, varied manufacturing industries. The population of the city therefore increases on a daily basis.

The study area enjoys tropical hot monsoon climate due to its latitudinal position. The tropical monsoon climate is characterized by heavy rainfall from April to October ranging from 2000 to 2500 mm with high temperature all the year round and a relatively constant high humidity. The relief is generally lowland which has an average of elevation between 20 and 30m above sea level. The geology of the area comprises basically of alluvial sedimentary basin and basement complex. The vegetation found in this area includes raffia palms, thick mangrove forest and light rain forest. The soil is usually sandy or sandy loam underlain by a layer of impervious pan and is always leached due to the heavy rainfall experienced in this area. The study area is well drained with both fresh and salt water. The salt water is caused by the intrusion of seawater inland, thereby making the water slightly salty. Due to continuous heavy rainfall and river flow, the study area experiences severe flooding almost every year and the effects are extended to biological resources.

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Fig 1: Map of Nigeria and Rivers State showing Study area.The study was conducted on the entire area of Port-Harcourt & Obio/Akpor Local Government Area, knowledge of Remote System and Geographic Information System were used in the production of land use maps of 1986, 2000 and 2007. The Land sat images of TM 30 by 30m resolution of 1986, 2000 & ETM of 2007 were obtained from Land sat global Land-Use and Land-Cover facility (www.glfc.com) and the Nigerian copy (base map) of State, Local Government Area and town maps which was delineated to Port Harcourt and Obio/Akpor Local Government Area of Rivers State was gotten from the Regional Centre for Training in Aerospace Survey (RECTAS) at Ile-Ife, Osun State. The Land sat images TM & ETM at band 2, 3, 4 for the years 1986, and 2000 & 2007 respectively were made to pass through processes of image enhancement, geo-referencing, region of interest selection, digitizing and image classification. A supervised classification was performed on colour composites of band 2, 3 and 4 into the following Land-Use and Land-Cover classes; Built-up areas, Mangrove Vegetation, Forest, Open Spaces, farm lands and water bodies.

Thus, the Land sat images were composited, designed & classified and post classified using supervised maximum likelihood method. The post classification analyses carried out includes; Confusion Matrixes- for accuracy assessment in kappa coefficient, Class Statistics- to observe the mass class conformation per year calculated in square kilo meter, Change Detection- to detect changes of mass class between 1986-2000 and 2000-2007, Vectorisation- conversion of mass class to vector for easy enhancement in GIS environment.

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The Land-Use and Land-Cover classification class statistics for each year in (km2) was copied to Microsoft office where table and charts were created. Also, the vectorised images of each year was exported to ArcGIS and clipped (clip analysis) with the study area boundary. The resultants were categorized in the ArcGIS environment using the symbiological property method as shown below on figure 3-5.

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ENVI to ArcGIS

ENVI

ArcGIS to ENVI

Data

Geo-referenced Port Harcourt and

Obio/Akpor LGA Map

Land sat imagery 1986, 2000 &2007

Clip Management

Image subset subset

- Results - LULC Maps (1986, 2000 & 2007)

Color composite creation

Classification (maximum likelihood)

Post Classification (Class statistics,

confusion Matrix, Change detection)

Vectorisation

Clip analysis

Database

ArcGis

ArcGIS ENVI

Fig 2: Cartographic model of the project.

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Figure 3: Map showing the towns and 1986 mass classification of the study area.

Figure 4: Map showing the towns and 2000 mass classification of the study area.

Figure 5: Map showing the towns and 2007 mass classification of study area.

RESULTS AND DISCUSSION

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The major Land-Use and Land-Cover classes for 1986, 2000 and 2007 are quantitatively analyzed for the area covered by each Land-Use and Land-Cover categories. The results of the land-use type observed in the 1986, 2000 and 2007 Mass Class are shown in table 1.

Table 1: Shows the occurrence of Land-Use type and percentage in the 1986, 2000 and 2007 Mass Class respectively.

Land-Use type

Area (km2) 1986 Mass

Class

1986%

occurrence

Area (km2) 2000 Mass

Class

2000%

occurrence

Area (km2) 2007 Mass

Class

2007%

occurrence

Built-Up Area 23.1 3.2 141.9 19.6 155.1 21.4

Farmland 132.6 18.3 64.8 9.0 79.5 11.0Forest 128.1 17.7 53.8 7.4 40.3 5.6Mangrove Vegetation

33.8 4.7 66.5 9.2 35.4 4.9

Open Space 26.3 3.6 20.1 2.8 22.6 3.1Water body 379.7 52.5 376.5 52.0 390.7 54.0total 723.6 100 723.6 100 723.6 100

Table 2: Shows the Land-Use type and difference in area within the Mass Classes of 1986 to 2000 and 2000 to 2007 and their percentage changes.

Land-Use Type

Area (km2)

Area (km2)

Area (km2) 2007

Difference in area (km2) 1986-2000

% change 1986-2000

Difference in area (km2) 2000-2007

% change 2000-2007

1986 2000

Built-Up Area

23.1 141.9 155.1 118.8 514.3 13.2 9.31

Farmland 132.6 64.8 79.5 -67.8 51.1 14.722.7

Forest 128.1 53.8 40.3 -74.3 58 -13.5 33.5Mangrove Vegetation

33.8 66.5 35.4 32.7 96.7 -31.1 87.9

Open Space

26.3 20.1 22.6 -6.2 23.6 2.5 11.1

Water Body

379.7 376.5 390.7 -3.2 0.84 14.2 3.6

Total 723.6 723.6 723.6        

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The Land-Use and Land-Cover of Port Harcourt and Obio/Akpor were grouped into; Built-Up Area, Farmland, Open Space, Forest, Mangrove Vegetation and water bodies. Of the total area in 1986 Mass Class, water bodies was the largest percentage 52.5%, Farmland 18.3%, Forest 17.7%, and Mangrove Vegetation 4.7%, opens space 3.6% and Built-Up Area 3.2%. Water body Dominated at the southern part of the study area while Farmland, Vegetation and Forest dominated at the southern part the study area with Open Space and Built-Up Area dominating at the centre of the study area.

In 2000 Mass Class, Water Body maintained its dominance with 52%, Built-Up Area 19.6%, Mangrove Vegetation 9.2%, farm land 9%, Forest 7.2% and Open Space 2.8%. Thus, there was an increase Built-Up Area compared to 1986 Mass Class.Spatial analysis of 2007 Land-Use and Land-Cover showed that Water Body maintained its dominance with 54.4%, Built-Up Area 21.4%, farm land 11%, Forest 5.6%, Mangrove Vegetation 4.9% and Open Space 3.1%.

In general, it was observed that Water Body decreased from 1986 to 2000 (52.5% to 50%) and increased from 2000 to 2007 (50% to 54%), Built-Up Area increased from 1986 to 2007 (3.2%, 19.6% and 21.4%), farm land decreased from 1986 to 2000 and increased at 2007 (18.3%, 9.0% and 11.0%), Mangrove Vegetation increased from 1986 to 2000 and decreased at 2007 (4.7%, 9.2% and 4.9%), Open Space decreased from 1986 to 2000 and increased slightly at 2007 (3.6%, 2.8% and 3.1%) while decreased from 1986 to 2007 (17.7%, 7.4% and 5.6%).

For a clear and informative comparison of the Land-Use and Land-Cover change, area value for the two periods 1986 to 2000 and 2000 to 2007 summarized below.

Figure 6: Chart showing the change detection form 1986 to 2000 and 2000 to 2007.

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Figure 7: Chart showing Land-Use occurrence within the 3 Mass Classes of 1986, 2000 and 2007.

Where BA- Built-Up Area, FL - Farmland, F- Forest, MV- Mangrove Vegetation, OS - Open Space and W- Water Body and Area in square kilometer.

CONCLUSIONThe study reveals that the Land-Use and Land-Cover in the study area changed over time whereby some increased, while others reduced in terms of spatial extent. The use of Remote Sensing and GIS technology is a better way of decision making on complex issues related to the earth (land suitability) and the people living therein, such as Agriculture, Forestry, Health, Resource Management, Land Administration, Water Resource Planning, Location Analysis, etc. In this study, Remote Sensing and GIS Technology were applied for decision making process in mapping the Spatio-Temporal changes in Land-Use and Land-Cover over three periods in Port Harcourt and Obio/Akpor Local Government Areas of Rivers State. This was done in line with the purpose and understanding of the colour coding criteria for RGB and 4 3 2 bands selection of Land-Use types. The geographic database was tested by defining and executing some criteria, which gave the result as shown in chapter four. Thus, this has shown the capabilities of GIS as a system to solve spatial problems and provide information to aid decision making.

RECOMMENDATIONSChanges in the Land-Use and Land-Cover of the study area and its effects on the biodiversity, the following recommendations should be adopted for policy makers for better decision-making.

As human beings generate the causes and experience the effects of global change processes, there is need for better understanding of the interaction between humans and the terrestrial environment. This need becomes imperative as changes in Land-Use

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become more rapid. Thus, Veldkamp and Lambin (2001) is of the opinion that understanding the driving forces behind Land-Use changes and developing models to simulate these changes are essential to predicting the effects of global change.

The continual increase of the aerial coverage of Built-Up Area needs to be checked by promulgating a law of unlawful expansion hence, this would protect the biodiversity in the study area.

Adequate continuous monitoring by making use of satellite remote sensing should be encouraged.

Forest guards should be employed if they are not yet on ground but if they exist, more should be employed and they should be exposed to more training on protecting the forest.

The people in the study area should be enlightened or educated on how to manage and protect the environment.

This research can serve as an entry point. Hence further research in the study area is recommended. The rapid Land-Use and Land-Cover change in the last ten years requires due attentions.

REFERENCES

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Adeniyi, P. O. and Omojola, A. (1999). Land-use land-cover change evaluation in Sokoto - Rima basin of northwestern Nigeria based on archival of the environment (AARSE). Geoinformation Technology Applications for Resource and Environmental Management in Africa, pp. 143-172.

Anderson, J. R., Hardy, E. E., Roach, J. T. and. Witmer, R. E. (2001). A land-use and land-cover classification system for use with remote sensor data. Geological Survey Professional Paper 964 and a revision of the Land-Use classification system as presented in U.S. Geological Survey Circular 671.

Braissoulis, H. (1999). Sustainable development and the informal sector: an uneasy relationship. J. Environ. Dev., Vol. 8(3), pp. 213-237.

De-Sherbinin, A. (2002). Land-use and land-cover change: A CIESIN thematic guide. Center for International Earth Science Information Network (CIESIN) of Columbia University, Palisades, NY, USA. Retrieved from http://sedac.ciesin.columbia.edu/tg/guide_main.jsp.

Eludoyin, S. O. (2010). GIS assessment of land-use and land-cover changes in Obio/Akpor L.G.A., River state, Nigeria.

Fasote, J. (2007). Assessment of land-use and land-cover changes in Port Harcourt and Obio/Akpor local government areas using remote sensing data and geographic.

Musaoglu, N., Kaya, S., Seker, D. Z. and Goksel, C. (2002). A case study of using remote sensing data and GIS for land management; Catalca Region. FIG XXII International Congress, Washington, DC, USA.

Odunuga, S. and Oyebande, L. (2007). Change detection and hydrological implication in the Lower Ogun flood plain, SW Nigeria. IAHS Symposium on Remote Sensing for Environmental Monitoring and Change Detection, Perugia, ITALIE, Vol. 316, pp. 91-99.

Pellika, P., Clark, B., Hurskainen, P., Keskinen, A., Lanne, M., Masalin, K., Nyman-Ghezelbash, P. and Sirvio, T. (2004). Land-Use change monitoring applying geographic information systems in the Taita Hills, SE-Kenya. Proceedings of the 5th African Association of Remote Sensing of Environment Conference, 17- 22 Oct., 2004, Nairobi, Kenya. Res. J. Environ. Earth Sci., Vol. 3(4), pp. 307-313.

RECTAS (2013) Regional Centre for training in Aerospace.

Tardie, P. S. and Congalton, R. G. (2002). A change- detection analysis: Using remotely sensed data to assess the progression of development in Essex county, Massachusetts from 1990 to

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2001. Proceedings of ACSM/ASPRS Annual Conference. Retrieved from http://www.unh.edu/naturalresources/pdf/tardie-paper 1.pdf

U.S. Geological Survey. (1999). The land sat satellite system link, USGS on the world wide web. URL: http://landsat7.usgs.gov/landsat_sat.html. 11/10/99

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