Geospatial mapping of gully erosion susceptibility in Etsako West Local Government Area, Edo State, Nigeria

Gully erosion is one of the major challenges faced in the southern part of Nigeria. This research aims to map gully erosion invested areas within Etsako West Local Government Area of Edo State and further produce the susceptibility map. The methodology entails the acquisition of Geo-environmental datasets using cloud-free high-resolution satellite images, SRTM DEM data and FAO soil data which aid in gully erosion analysis such as slope aspect, slope degree, slope-length (LS), topographic wetness index (TWI), plan curvature, profile curvature, soil texture, stream power index (SPI), altitude. These derivatives were selected for further analysis to produce the various maps. Multi-criteria decision making and statistical methods, such as frequency ratio (FR) were utilized during data analysis to investigate the spatial correlation between gully erosion and each of the listed factors. The results obtained showed that soil texture and slope degree were the most important gully susceptibility factors. All the maps were created at the same scale of 1: 160,000 except for the susceptibility map that is produced on a scale of 1:180,000. The computation of the Area Under Curve (AUC) showed 76.47% which is practically reliable. The conclusion from the research demonstrates that the northern and southern parts of the study area are highly prone to gully erosion. It is therefore recommended that good drainage channels and tree planting be promoted to reduce the gully erosion influence across the settlements at risk.