Land-Use/Land-Cover Dynamics in Calabar Metropolis Using a Combined Approach of Remote Sensing and GIS

This paper assessed the dynamics in the land use/land cover (LULC) within patterns of the land use/land cover (LULC) in Calabar metropolis. The thermal imageries for 2002, 2006, 2008, 2010, 2012, 2014 and 2016 were obtained and processed using remote sensing and Arc GIS software package in order to determine the changes that have occurred in the LULC in study area. The result of the LULC thematic maps overall accuracies was computed above 80 percent, which indicates an almost perfect agreement. The findings of this study reveal that, LULC classes by the year 2016 have assumed different dimensions of change from the sizes of their previous sizes in comparison to their current sizes. Land-use pattern changes in the study area were characterized by an increase in the built up class, waterbody (though with a slightly negative change from 2010 to 2012) and a predominant negative trend in dense vegetation and bare land classes; thus, indicating that the future changing trends will pose a depleting threat to the overall LULC. This study has shown that, the changing land use pattern of the area is capable affecting certain characteristics of the environment such as surface temperature. The study recommends that effort should be made by the government to increase urban vegetation around city centers and outliers by embarking on reforestation.

in the environment triggered by the interaction between human and the environment. Population increased to major cities has resulted in urban sprawl at an unprecedented rate, which according to [1] analysis and prediction report, is projected to continue into the next era. The geometric increase in the global population has necessitated the building of services such as, settlements, to accommodate the growing population. These activities result in land conversion, such as, forest or plantations, agricultural lands and grasslands to grow impervious surfaces such as roads, sidewalks, parking lots, rooftops and bare lands [2] [3] [4]. According to numerous studies [5] [6] [7] [8], land conversion to impervious surfaces is one of the main contributors to climate change and variability in different parts of the world which potentially affects the health of urban dwellers living in localities that continue to experience LULC changes.
More also, land-use/land-cover change contributes significantly to earth-atmosphere interactions, forest fragmentation, and biodiversity loss and has become a major issues for environmental change monitoring and natural resource management [3] [4]. Therefore monitoring land cover dynamics in the urban area, in an appropriate and cost effective manner, is very important to local communities and decision makers. It enables the planning, management and conservation of natural resources and the environment.

Study Area
Calabar Metropolis, the study area, is the capital of Cross River State, Nigeria, located at the southern part of the State. It encompasses of Calabar Municipality and Calabar South Local Government Areas and lies between latitudes 4˚50'N and 5˚10'N and longitudes 8˚17'E and 8˚20'E; bounded to the north by Odukpani Local Government Area (LGA) and to the East by Akpabuyo LGA. Calabar Metropolis is sandwiched between the Great Kwa River to the East and the Calabar River to the West. The present of urban area is on the eastern bank of the Calabar River. Its growth of the southern part is hindered by the mangrove swamps. It covers an estimated land area of about 274.593 km 2 ( Figure 1). Calabar falls within tropical equatorial (Af) climate of high temperature, high relative humidity and abundant annual rainfall [9]. The annual rainfall is 2750 mm and mean annual average temperature is 26.1˚C. The study area has witnessed a tremendous increase in the population of 10,000 estimated at the pre-colonial, to 99,352 in 1993; 328,876, in 1991. The last census in 2006 put the population to 371,022 [10]. The population growth of Calabar has been followed by the expansion of its physical boundaries. This increase in the physical boundaries implies a corresponding loss of vegetation and land in the area thereby a direct impact on the micro-climate [11].

Image and Pre-Processing
Landsat cloud-free imagery were acquired from the NASA web site which M. E. Awuh et al.

Image and Pre-Processing
where P is the water proportion, S water is the pixel area of water; S urban is the pixel area of urban-used land.

Change Detection
Cross tabulation was employed to determine quantities of conversions from a particular land cover to another land cover category at a later date [12]. The change matrices based on post classification comparison were obtained. Change that occurred over the study period 2002-2016 (15 years) was analyzed. The extent of the land use and land covers change in the study period was also calculated, the results were presented in maps, charts and tables.     Table 2).

Analysis of LULC Class Image for 2006
The result of the land use class image of 2006 is displayed in Figure 4. The result     Table 3). The result further showed a considerable increase in the built up cover by 711.95 ha, representing 10.9 percent of the total LULC classes of the area (Table 3 and Figure 5). Also

Analysis of LULC Class Image for 2008
The results of the 2008 land-use class image ( Figure 6) revealed a considerable

Analysis of LULC Class Image for 2010
The results of the LULC image for 2010 revealed some astonishing alteration as far as the area coverage of the corresponding land uses are concerned (Table 4).       Furthermore, the findings of this study as depicted in Figure 13, show that dense vegetation class had the highest percent coverage of 38.07, though with a decreasing trend, followed by sparse vegetation. Waterbody and barelands had the lowest area coverage. Also, the highest percent drop in its dense vegetated cover compared to other years. Sparse vegetation class witnessed a tremendous increase in its cover compared to 2014 with its area coverage exceeding 6000 ha.

Analysis of LULC Classes for 2016 Image
By 2016, all the LULC classes continue to experience dramatic changes in their area coverage ( Figure 14 and Table 5 The results further revealed that, despite the dramatic negative change in the dense vegetation cover it still maintained its high area of coverage with 16,629.85 ha, representing 51.08 percent of the total area of land use and covers (Table 5).

Change Trends of LULC Classes between 2002 and 2016
The LULC classes by the year 2016 have assumed different dimensions of change     (Table 7 and Figure 15).

Conclusion
The findings of this study revealed that, the overall condition of the dense cover is decreasing from abundance and resilience. This is revealed by the decreasing NDVI values generated from the maps. The predominant negative trend in the LULC classes can also be attributed to the expansion, which can be explained by endogenous and exogenous factors such as, population growth through  in-migration into the Calabar metropolis. Furthermore, the fact that vegetation, particularly dense covers is diminishing, using the evidence of the LULC classes, as revealed by the findings of this study which indicates that, future changing trends will pose a depleting threat to the overall LULC. The primary cause of these losses was the expansion of urban development. The increase in the built-up area can be attributed to the rapid urbanization of Calabar Metropolis.
Transition from barelands to waterbody class can be attributed to sea level rises [15]. Lastly, though there is a moderate growth rate of built-up, bare land cover, efforts must be made to augment vegetation cover in Calabar Metropolis.