Geospatial assessment of land use/cover, rainfall, and flood incidents in Eti–Osa, Lagos, Nigeria

Flooding in Lagos State has been on the rise in the past two decades, especially in the Eti-Osa area of the state. This is largely due to the increased volume of rainfall associated with climate variability and sea level rise. Flooding incidents have led to loss of lives and properties. The objective of this study is to examine the dynamics of flood occurrences in the Eti-Osa area of Lagos metropolis. Rainfall data for the area covering a period of 30 years (1990 to 2019) were obtained from the Nigerian Meteorological Agency (NiMET) in Lagos, and analyzed using the basic descriptive statistical technique. The purpose was to evaluate rainfall characteristics that were influencing flooding events in the area. Furthermore, remotely sensed multi-date Landsat imageries of 1990, 1997, 2001, 2012, and 2017 were obtained, and analyzed to determine how land use and land cover characteristics have changed and have been affected by flooding over the study period. The data were subjected to digital image processing and supervised classification was carried out on the images of the various dates. Results showed that flooding became prevalent as more areas became built up and as vegetated areas declined. Also, flooding events appeared to be responsive to the climatic extremes. Moreover, poor drainage, increased population number s, and non-compliance to building and current environmental regulations were key factors that exacerbated the increased prevalence of flooding in the area. The study recommended that flood control policies, including land-use planning for the area, need to be pursued urgently.