Geoelectric Investigation of Shallow Subsurface Stability at Oko-Nanka Prominent Gully Erosion Site in Niger Delta Basin, South-Eastern Nigeria

Publication Date : 10/05/2022


Author(s) :

Egwuonwu, G.N, Umeobika, M.N, Okpala, P.K, Orji, O.


Volume/Issue :
Volume 58
,
Issue 1
(05 - 2022)



Abstract :

The shallow subsurface horizons at vicinity of Oko-Nanka prominent gully erosion site in Niger Delta Basin were surveyed. Using two-dimensional electrical resistivity tomography (2DERT) geophysical technique, the survey was aimed at inferring the stability gully's wall and its surrounding for engineering development. The 2DERT was carried out along accessible survey lines laid parallel and perpendicular to the flanks of the gully. Apparent resistivity data 6 collected ranging from low to high resistivity (1.22 to 1.0 x 10 Ùm) were processed using modelling software namely Res2DInv version 3.56 hence, 2DERT models obtained with the registered data. The tomographic models obtained show that the gully erosion site is predominantly characterized by unconsolidated earth materials. Holistic interpretation unveils the fact that weak formations such saturated sand, sandy clay and some consolidated soil occurrences at various depths predominates the gully site. Based on resistivity model values, the Oko and Nanka flanks were noticed to bear significant contrast comparatively Oko-flank bearing lower resistivity range. The landsliding tendency was found to be lower at Nanka side of the gully compared Oko flank of it. Predominantly, differential saturation was observed to be more across the profiles surveyed at the Oko side compared with those at the Nanka side of the gully site. The variations the 2DERT models resistivity values have provided useful information for measures of various civil engineering constructions and superstructures at the Oko-Nanka gully vicinity


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