Analysing neo-tectonic effects on gully development within orlu and environs south-eastern nigeria from landsat imagery and azimuthal sounding data

Geophysical study was carried out in some gully erosion sites within Orlu and environs with the objectives of identifying tectonic and neo-tectonic features, delineate their trends and evaluate their effect in gully development and propagation in the study area. Detailed geological field mapping was carried out to characterize the gullies and to estimate the strikes and directional trends of the gullies. Similarly, GIS interpreted Landsat-ETM imageries were also used to determine the lineaments and their trends in the study area. Azimuthal resistivity sounding was carried out at various locations in the study area to determine the direction of electrical anisotropy as well as the coefficient of anisotropy. This was rotated in four azimuths at angles of 0°, 45°, 90°, and 135° corresponding to the N-S, NE-SW, E-W, and NW-SE directions respectively. Geological field mapping of the study area revealed that the gullies in the study area trend approximately in the NW-SE and NE-SW directions with the NE-SW being preponderant. Rose diagrams generated from the strikes and lengths of lineaments interpreted from Landsat images revealed two structural trends of NW-SE and NE-SW with the NW-SE being dominant. Results of the azimuths frequency diagrams generated from the anisotropic soundings revealed uni-modal to poly-modal pattern with the dominant trend observed to be in the NW-SE and NE-SW directions. The correlation of the trends of the gullies with the lineament trends from Landsat and the direction of electrical anisotropy suggests that the gully origin and propagation in the study area may be tectonically controlled