Gully Erosion Problems in Selected Areas of Edo State: Factors and Control

Abstract

Gully erosion is a serious ecological problem in Edo State and has negative impact on agricultural productivity, lives and properties in both urban and rural environments. This paper therefore aims at identifying factors contributing to the formation of gullies and methods of controlling them so that further environmental degradation would be averted. Three gully sites were selected from the three geo-political zones of the State. Data were collected through remote sensing, field topographical survey and soil sampling on gully walls and gully beds. Meteorological and hydrological data were also collected. Slope stability analysis was also carried out. The KerbyKirpich equation was applied to estimate the overall time of concentration and Rational formula used to determine the peak discharge. The study revealed that the selected study areas possess all the characteristics of an erosion prone area which are: rainfall of very high intensity, steep slopes resulting in large runoff and soil with low organic content and relatively low shear strength obtained from the geotechnical investigations. Results from the studies revealed that the gully width and depth varied considerably from top to bottom. The cross section shows that the gully is Ushaped for Ekehuan gully and V-shaped for Auchi and Ewu gullies, indicating a large catchment area and a large volume of discharge passing through the gully.