Gully Erosion in Rafingora, North Central Nigeria: Role of Geology and soil properties

Abstract

Geological and geotechnical study of gully erosion was carried out in Rafingora, northern part of Bida basin to determine the lithologies of the area and assess the influence of geotechnical properties of the soil on the gully erosion. Field study across the gully profiles revealed 3 lithologies of highly erodible massive reddish sandstone underlain by light brownish clastic supported sandstone with cross bedding and herring-bone as structural imprint, underlain by light greyish mudstone of high resistance to gully influence. Results of the sieve analysis indicated that the soils in the area are poorly graded with average coefficient of uniformity Cu of 4.61 and coefficient of curvature Cc ranged between 0.4 – 2.54 indicating that the soils are poorly graded and susceptible to erosion. The soil in the area possess an average low Plastic index (19.52 ), Optimum Moisture Content (8.3), Maximum Dry Density (1.98), low values (22° and 18.9max) of AIF and cohesion and as well moderate glad2deen@gmail.com Coefficient of permeability (K) between 1.29 × 10-6 to 1.29 × 10-3 cm/sec. These indicate that such soil can only offer little resistance to the effect of both surface water and subsurface flow which made these soil to be loose, non-coherent and to slide upon getting in contact with water or even to disintegrate under dry conditions.