Assessment of land use and land cover changes and urban expansion using remote sensing and GIS in Gboko, Benue State, Nigeria
There has been a rapid growth of urban areas across the globe since 1950s with the majority of world population living in urban areas rather than rural areas, in search of better job opportunities and higher quality of services. This trend of transition from rural to urban is expected to continue to rise and government in developing countries are likely going to face more challenges in different sectors, necessitating the need of understanding the spatial pattern of the growth for effective urban planning. The objectives of this study were to map and determine the nature, extent and rate of land use and land cover changes, to analyze the spatio-temporal land use and land cover change patterns and assess urban expansion in Gboko Local Government Area of Benue State, Nigeria. The emphasis was on determining the extent and rate of urban expansion in the area. The study focused on a period of 30 years; from 1987 to 2017. Satellite imageries used included Landsat TM (1987); Landsat ETM+ (2007); and Operational Land Imager (OLI) (2017). The Landsat imagery dataset was sourced from the Earthexplorer platform from United States Geological Surveys (USGS), Global Land Cover Facility (GLCF) and GloVis. The three images of 1987, 2007 and 2017 were classified using maximum likelihood classifier in Idrisi Selva to detect the land cover changes. The study resulted in an overall classification accuracy of 80.77% ,85.84% and 86.24% for 1987, 2007 and 2017 respectively. The result of the classification revealed that between 1987 and 2017, urban area increased from 3232ha (1.68%) in 1987 to 8542ha (4.45%) in 2007 and rose up to 16614ha (8.65%) in 2017. Forest land on the other hand declined from 52108ha (27.13%) to 46523ha (24.23%) down to 16723ha (8.71%) in the same period. Grassland was the dominant land cover occupying 69074ha (35.97%) in 1987 increasing to 79874ha (41.59%) and 129715ha (67.54%) in 2007 and 2017 respectively. The overall trend (1987-2017) revealed that urban area has increased up to 13382ha (9.01%) at an annual rate as high as 2.7% higher than the rate in the first period. Forest declined throughout the period with a loss of 5585ha(12.57%) in the first period at the annual rate of -2.51% and 29800ha (25.7%) in the second period at the annual rate of -2.57%. The overall trend shows that forest lost 35385ha (23.82%) at the rate of -7.15%. Farmland also decreased during the period losing 16006ha (36.03%) in the first period at an annual rate of -7.21% and 22317ha (19.25%) in the second with an annual rate of change of -1.93%. This high rate is an indication that in no distant future the area may be completely devoid of forest vegetation. From the result, it is evident that the rate of urban growth will continue and would certainly threaten forest areas in Gboko LGA. Finally, this study provides a guide to planners for successive urban planning in exploring the rate and pattern of urban growth in Gboko LGA.
Keywords: Urban growth; LULC change; Landsat TM; Landsat ETM+; and Operational Land Imager (OLI), spatio-temporal, maximum likelihood classifier, Idrisi Selva , Gboko