Land use/ land cover classification and change detection mapping: A case study of Lagos state, Nigeria

Abstract

The study attempts to determine the land use/land cover expansion that occurred in the area over a period of thirty years. Multi temporal Landsat satellite images TM 1986, ETM+ 2001, 2006 and 2018 from the United States Geological Survey (USGS) website as primary dataset. Area of interest was clipped in ArcGIS environment and then enhanced and classified in ENVI. Using supervised classification algorithm, the images were classified into bare land, built-up area, vegetation and water body used to carry out change detection analysis or time series analysis. In-addition, figures from National Population Commission (NPC) were used. Change detection analyses was carried out on the imageries to obtain the physical expansion of the area. The Land Consumption Rate (LCR) and Land Absorption Coefficient (LAC) were determined as well. Accuracy assessment was carried out on the images classified using the confusion matrix with Ground truth image tool on ENVI. An overall kappa coefficient was generated from this assessment which proved to be a very good result. Results obtained from the analysis of built-up area dynamics for the past four decades revealed that the town has been undergoing urban expansion processes. There was an increase in the built-up area between 1986 and 2018 which is largely due to the increase in population of Lagos state based on its high Urbanization rate. Vegetation cover reduced between 1986 and 2001, which is reasonable considering the rate at which the built-up area was increasing. But between 2001 and 2006, vegetation increased a little, this due to farming in 2006. Bare land had an inconsistent change. The increase in bare land could be as result of bush burning while the reduction could be as a result of more farming in the state or development of more built-up areas. It is recommended that Global change research efforts should be encouraged through international research partnerships to establish international land use /land cover science program to bridge the gap between climate researchers, decision makers and land managers; There was more reduction in vegetation than increase which poised a great danger that could cause greenhouse effect on the environment. Government at all levels should ensure that all these land use/land cover types are maintained to save our ecological biodiversity.