GEOSPATIAL ASSESSMENTS OF HYDROLOGICAL IMPACTS OF FLOOD OCCURRENCES IN ADO-EKITI AND ENVIRONS

ABSTRACT

Flood risk assessment is an important component of risk management. This study aims to generate a GIS-based flood risk map that can facilitate proper planning of mitigation measures against future floods occurrences. This study uses GIS technique and remotely sensed data to assess the extent of urbanization in land use, and vegetation changes in Ado-Ekiti metropolis between 1986 and 2017. Digital Elevation Models (DEM), settlement maps and satellite imageries to assess the susceptibility of the infrastructures located within the study area (Ado - Ekiti). Spatial analysis are used over Ado local government area with a view to making suggestions for future flood disaster and risk mitigation, generate map that provides useful spatial information of land use changes, population distribution and rainfall variability within flood vulnerable areas. The result shows that the NORMALIZED DIFFERENCE VEGETATION INDEX were generated for the years 1986, 2003 and 2017 to assess the changing patterns of vegetation in response to flooding in Ado-Ekiti metropolis. The NDVI for year 1986 shows that the vegetation was very healthy, recording high value of 0.35. The NDVI value obtained for year 2003 however decreased as compared to that of 1986 with a high value of 0.143accross the Ado-Ekiti metropolis. The vegetation pattern continued to change with a fairly lower value in 2018 with a low value of-0.007, depicting the extent of vegetation loss over the area. The significance of the normalized difference vegetation index values, which is a decreasing trend indicates increase in population that reduces natural vegetation, changing land use pattern (construction, anthropogenic) and significantly increased Flooding Drainage channels map generated indicated that stream channels and their characteristics (i.e. area and slope) affect the extent and frequency of runoff thus determine the likelihood of flooding within the study area.

Overall study therefore reveals that flood severity is rated very highly in the core Ado-Ekiti city centre, and that flooding in the town can be attributed to both physical and humanly activities. While factors, such as rainfall intensity and duration, cannot be controlled, early warning of flooding based on climatic variability will help people in flood prone areas to prepare ahead oftirne.