The Characteristics and the Erodibility Potentials of Soils from Different Geologic Formations in Anambra State, Southeastern Nigeria

摘要

The characteristics and the erodibility potentials of soils from Benin, Ogwashi-Asaba, and Nanka formations in Anambra state, Nigeria were studied. The study involved an integration of field observations, geotechnical analyses, and topographical modelling. About ten gullies were identified in the field. However, six major gullies labeled BN1, BN2, OA1, OA2, NK1, and NK2 were chosen and studied extensively to represent the three geologic formations. The results showed that soil properties, anthropogenic activities, topography, fierce surface runoff, and sparse vegetation are the factors that commonly and systematically influence the characteristics and erodibility potentials of all these soils. However, anthropogenic activities and soil properties play the most, dominant roles in the erosional processes. The specific gravity of the soils are similar, with values ranging from 2.50 to 2.69. Compaction test revealed all the soils were loose and collapsible. Grain size analysis further revealed that they have low content of fines (<25%, except for OA1 with 58.87%). The plasticity index of the fines indicated that they are nonplastic to low plastic soils (values range from 0–12%). The soils are highly to moderately permeable, with values ranging from 4.22×10_(?6)m/sec to 4.34×10_(?4)m/sec. All have low cohesion ranging from 1–7kPa, except for the OA1 with 27kPa. Based on the study, the three geologic formations have similar characteristics and high erodibility potentials; though OA1 has varied characteristics and thus, lower erodibility potential.