THE IMPLICATION OF URBANIZATION ON LAND USE/LAND COVER AND RUNOFF TRENDS DYNAMICS IN ABEOKUTA (1988-2018)

Abstract

This paper investigates the implication of urbanization on land use/land cover and runoff in Abeokuta from 1988-2018. Land use/Land-cover changes in the study area were quantified by extracting data from satellite imagery; the flow data of the Ogun River from 1988-2018 was also evaluated. The study shows gross changes in the 6 land cover types identified in the study area which were estimated for Landsat imagery (1988, 1998, 2008, and 2018); with some of the land cover types increasing while others decreased. An estimated increase in the built-up area occurred within the space of 30 years from 38.8km2 in 1988 to 109.3km2 in 2018; light forest increased from 6.1 8km2 in 1988 to 118km2 in 2018 while dense forest/swamp decreased from 66.8 8km2 in 1988 to 398km2 in 2018. The Mann-Kendall statistical technique was used to identify significant decreasing, increasing, and stable trends in time series data. The study shows both increasing and decreasing trends in the different land use types identified; also that urbanization affects the trend of runoff in Abeokuta from 1988 - 2018, it was discovered that the increase in runoff trend is directly proportional to the increase in impervious surfaces. The implication of this is the recurrent incidence of flood, loss of lives and properties, loss of arable lands, and human displacement. The paper suggests ways of reducing impervious surfaces in the study area like increasing green spaces, land reclamation, etc. and mitigating the effects of floods like legislation against building on floodplains, introduction of forest reserves, etc.