Gullying Processes in the Upper Idemili River Catchment Area of Anambra State, Nigeria

Abstract

Upper Idemili River catchment in Anambra State, Nigeria was studied for the effect of gullying processes in the area. The methods employed were fieldwork, Arc Gis production of digitized map which show the gully profile and laboratory analysis of soil and water samples. Hydrogeochemistry revealed acidic to slightly acidic water which is responsible for the decomposition of the cementing materials. The presence of the chemical species accounts for the dissolution of mineralogical and chemical composition of the rocks, and the different geochemical processes in the area. The bulk of the dissolved solid is attributed to geochemical reactions of oxidation-reduction and ion exchange reactions enhanced by acidic water. The chemical character of the water was employed to determine the water type using piper trilinear diagram and sodium bicarbonate (Na-HCO3) water type was identified. A subdivision of the piper trilinear diagram indicates that the main water class is the one in which alkalis exceed alkaline earth elements and also dominated by sodium-bicarbonate type by 100% in each category. The high percentage of sodium water suggests possible ion exchange reaction that may lead to soil disaggregation. The hydraulic properties show that the soil material is porous, and permeable with high hydraulic conductivity which enhances gully development through an increase in water flow and its proneness to gully erosion. This study will create awareness on the importance of gully erosion and the need to take precautionary measures.