Hydrogeological and Geotechnical Assessment of Gully Erosion Sites in Parts of Uturu, Southeastern Nigeria

This study aims at assessing the hydrogeological and geotechnical characteristics of gully erosion sites in Uturu and environs. Standard hydrogeological and geotechnical investigation methods were adopted in this study. Field geological study of the area revealed that it is covered by sedimentary rocks. The soils are lateritic and are the product of intensive weathering that occurs under tropical and subtropical climatic conditions resulting in accumulation of hydrated iron and aluminum oxides. Results of sieves analysis show that the soils at the gully sites having sorting values ranging between 0.42 and 2.3 coefficient of uniformity values ranging between 3.0 and 10, and the coefficient of curvature values ranging between 0.2 and 1.3. These indicate that the soils are fair to well-sorted in places. The plasticity indices values ranging between 11.0 and 29 with mean value of about 20 indicate soils of moderate to high plasticity, slight dry strength and easily friable. Value of maximum dry density ranges between 1.83 g/cm3 and 2.12 g/cm3 at optimum moisture contents of between 7.4% and 11.3% reveals that the soils were generally loose. The hydraulic conductivity and transmissivity values as determined from statistical grain size method range between 3.8 x 10-4 cm/s to 6.4 x 102 cm/s and 3.8 x 10–2 cm 2 /s to 9.6 x 104 cm 2 respectively. These indicate moderate seepage fluxes and adverse pore pressures and are thus easily erodible. From the geotechnical analysis results, recommendations for erosion control such as aforestation and construction of drainages were suggested.