Spatial Analysis of Flood Prone Areas in Ilaje Local Government Arae, in Ondo State, Nigeria

Abstract

Flood is one of the natural disaster known to be part of the earth biophysical processes, which its occurrence can be devastating; due to mostly anthropogenic activities and climatological factors. The aim of the research is to identify flood prone areas using geospatial techniques and the specific objectives are to carry out terrain analysis of the study area and to generate flood vulnerability map of the study area. The study analyzed rain fall data; soil map, the drainage system and Shuttle Radar Topographic Mission (SRTM 30m) of the area. A geographic positioning system (GPS) device was used to take coordinate points of flooded areas in the study area during field work. With the use of ArcGIS 10.8 version the data were modelled to generate the vulnerability map of the study area. The drainage system was generated through on-screen digitization of topographic map of scale 1:50,000 of Ondo South-West. The mean annual rainfall of Ilaje local government was generated in the ArcGIS environment from the rainfall data through spatial analysis tool. The SRTM was used in terrain analysis of the study area. The soil map of the study area was clipped to generate the different soil map of the area which are Arenosol, Gleysol and Acrisols. Weighted sum analysis of ArcGIS was adopted to generate the final vulnerability map of the area. The results generated showed the lowest mean annual rain fall of the area between 1,880mm and 1,990mm and the highest mean annual rain fall was between 2,340mm and 2,440mm. Digital elevation model (DEM), slope, aspect and flow direction were generated from the SRTM. Drainage density of the area was generated using the drainage system. 360.35km square was vulnerable, 474.79km square was least vulnerable, 235.31km square was moderately vulnerable and 218.01km square was highly vulnerable in the study area.