Abstract

Erosion index map of Akure Metropolis was developed using an integrated remotely sensed, geological and soil data. This was with a view to classifying the metropolis into different erosion risk zones. Administrative and topographic maps, geologic and soil maps, Landsat ETM+, Aster DEM and thirty two (32) erosion types data were acquired. Landsat ETM+ was pre-processed for geometric correction, haze reduction and re-sampling. Optimum index factor and covariance analysis were carried out in order to determine the least correlated bands and these bands were subjected to convolution filters, texture analysis at 3X3 window size, histogram equalization, de-correlation stretch, principal component analysis (PCA) and the Aster DEM to topographic analysis such as sink fill and shielded relief to generate slope map and lineament map. All the derived maps including the soil map were reclassified and given risk values according to their order of degree of contribution to either accelerate or decelerate soil erosion. Using weighted index overlay raster tool in ArcGIS software, all thematic maps were captured in GIS environment to produce a composite erosion index map of the study area. Existing erosion type data were used to establish the reliability of the erosion index map. The erosion index map classified the Akure Metropolis into three zones – very low risk (57.5%); low risk (33.9%) and moderate risk (8.6%). Most parts (91.4%) of the metropolis fell within the very low to low risk zones with tendency for sheet/reel erosional features. Areas with moderate risk with tendency for gully erosion were majorly located on the high slope region.

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