GEO-ENVIRONMENTAL ASSESSMENT OF GULLY EROSION AT THE UNIVERSITY OF BENIN USING GEOINFORMATION AND ENGINEERING METHODS
This paper assessed gully erosion at the University of Benin, Nigeria, using geoinformation, ground survey data and geotechnical engineering methods. This will help to understand the mechanism responsible for the gully formation and then develop control/management measures. The catchment was geo referenced using GNSS, total station, Google historical imageries and multi temporal images for monitoring land degradation. Topographical parameters of the catchment such as slope angle, spot height, contour and other morphological parameters of the gully were obtained. Using the multi temporal images, the gully head retreat was ascertained for 2003, 2005, 2007, 2010 and 2013 respectively. Soil samples were obtained to a maximum depth of 2m at both the upper and lower reach of the catchment using hand auger. Boreholes 1, 2 and 3 where recovered from the upper reach of the catchment while Boreholes 4, 5 and 6 were obtained from the lower reach of the catchment. Information obtained during the topographical survey shows that the ground slope at the upper reach of the catchment is between 0,3 and 0,5 % while that of the lower reach is between 3 and 7 %; this accounts for the high rate of erosion at the lower reach of the catchment. Ground survey data were processed in excel format before imported into Arc GIS 9.3 software used for environmental modeling; this was used to produce trend in environmental degradation.