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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 located on the high slope region.

An integrated geophysical investigation involving Very Low Frequency Electromagnetic (VLF-EM), and electrical resistivity methods using Schlumberger Vertical Electrical Sounding (VES) techniques was conducted at Deeper Life Camp ground, Ipinsa, Akure, Southwestern Nigeria with the aim of developing a model map that will enhance the knowledge of the subsurface geology viz-a-viz foundation integrity for appropriate location of building within the study area. The effect of four factors including soil apparent resistivity at different depths, depth to bedrock, geology and fracture density on engineering foundation were considered. In order to achieve this, a total of ten traverses were established in approximately NW-SE, NE-SW, N-S and E-W directions with station interval of 5 m and inter-traverse separation of 10 m. One hundred and forty eight (148) station positions were occupied in all for the VLF-EM profiling. Also, fifty four (54) VES stations were occupied across the study area with current electrode spacing (AB/2) varying from 1 to 65 m. Hilbert transform, Amplitude analysis, Fraser technique and Q-Factor performed on the VLF-EM method assisted in the delineation of conductive zones that could be inimical to foundation integrity. The VES result delineated four major geo-electric layers within the study area which are: topsoil, weathered layer, fractured bedrock and the fresh bedrock. The thickness of the layers generally ranges from 0.5-19.6 m. Based on geological and geophysical investigations, foundation integrity map of the area was produced using the Multi-criteria Decision Analysis, approach of Analytical Hierarchy Process (AHP). The model map classified the foundation integrity of the study area into very low, low, moderate, high and very high foundation integrity zones. The competency model at a depth of 3 m is adjudged most suitable for foundation in the study area.

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