Abstract
Geological, geotechnical and geochemical
studies were carried out in Rafi Gora area to ascertain the erodibility of the
soils. Medium and coarse-grained sandstone and clay stone were mapped with
structures like joints, cross bedding (120/18E and azimuth of 190S),
Herringbone, clay clasts, lamina and bioturbation. The sand content of the
soils is between 59% and 90%, silt ranges from 18% to 1% and clay constitutes
between 9.9% and 32%). Using USDA textural classification, the soils were
classified into sand (S), Loamy Sand (LM), Sandy Clay (SC) and Sandy Loam. The
soil has a mean pH value of 4.73, average Organic Matter (OM) content of 2.72
and the Coefficient of permeability (K) of 0.90 cm/sec. This k is classified to
be within moderately rapid flow (FAO, 2010), an indication of base flows which
could result in the collapse of river bank and consequently advance the growth
of gullies. Erodibility index (EI) ranges between 0.01 and 0.16 with a
significant positive relationship with silt content (0.96), clay content (0.30)
and organic matter content (0.20) but significant negative relationship with
sand content, pH and permeability. It was advised that excavation of vulnerable
claystones by the locals for building construction be totally discouraged.
Keywords: Geological,
Geotechnical, Geochemical Erodibility index.