Geological Characterisation and Environmental Assessment of Gully Erosion in Parts of Jos-Plateau, North-Central Nigeria

Gully expansion is constituting a potential hazard for construction and reduction of available land in some parts of the Jos-Plateau. This study employed geological mapping, geotechnical soil analysis, and field measurements of gully geometry to characterise the gullies. Eighteen gullies were mapped and sampled for geotechnical property determination. The gullies ranged from small to large gullies, with dominant U-shaped, few V-shaped and trapezoidal shaped. Formation processes distinguished between natural and anthropogenic influences with varying degrees of erosion. Moisture content ranged from 1.1 to 18.1%, with an optimal value of 18.1%. Grain size distribution indicated that the soils were primarily sandy, with fines (clay and silt) ranging from 0.9% to 9.3% and gravel from 0 to 20.5%, while sands constituted 73.0 to 99.1%. Liquid limits ranged between 30.4 and 61.0%, plastic limits from 19.2 to 32.2%, and linear shrinkage from 7.1 to 15.0%, indicating varying levels of plasticity. Compaction tests yielded optimum moisture content ranging from 10.0 to 15.5% and maximum dry density between 1.56 and 1.98 g/cm³. Specific gravity values ranged from 2.50 to 2.69. Gully characteristics, geotechnical and geological considerations should be applied to minimize erosion and ground instability risks for urban planning and development in the area.