By Ayogu, Chinero Nneka
This research work aimed at characterizing the stream sediments of the Anambra drainage basin, southern Nigeria. From the research objectives, the sediment geo- chemical composition, spatio-temporal variation, grain size distribution, sources of sediments, geo-technical matrix of the basin soil, drainage composition were studied. Sediments were analyzed to determine the composition of the selected 21 parameters (clay, silt, fine sand, coarse sand, pH/ H2O, KCL, carbon, organic matter, nitrates, sodium, potassium, calcium, magnesium, cation exchange capacity, base saturation, aluminum, hydrogen, phosphorus, manganese, zinc and iron) and the sediment grain size distribution (mean size, skewness, sorting and kurtosis) in the laboratory. Soil samples were also collected from the six sub basins for evaluation of their physical properties (aggregate stability, bulk density, total porosity, hydraulic conductivity, macro porosity, dispersal ratio, moisture and micro porosity). Sediments were composed of metals, non-metals and heavy metals with 85.57% and 85.3% of the composition loading (clay, silt, sand, iron, magnesium, carbon, organic matter and sodium) explained at the rainy and dry seasons, respectively. The sediments exhibited spatio-temporal variation at p < 0.05 in carbon (0.19), organic matter (0.19), magnesium (.002)-cum- CEC (.008) in most sub basins. The calculated T-value for silt, pH/H2O, KCl, carbon, organic matter, sodium, potassium, calcium, CEC and base saturation were greater than T-tab, implying significance. There was a significant relationship (r=>.661, p < 0.05) between variables-base saturation and potassium chloride; organic matter and carbon; nitrates and clay; hydrogen and pH/H2O; fine sand and clay; manganese and fine sand; hydrogen and potassium chloride; manganese and CEC; coarse sand and silt; calcium and fine sand together with manganese and coarse sand. Sources of sediments were mainly from physical processes (erosion) and anthropogenic activities (construction works, agricultural activities, sand mining and decay of vegetal matters occurring in the stream channel). Grain size was dominated by sand which ranged from coarse to fine, sorting ranged from poorly to moderately sorted, skewness spanned from positive to negative, while kurtosis was between leptokurtic to very leptokurtic. The basin soil was porous with a low stability index (9.17- 27.55), easily dispersed and accelerated accumulation of sediments. The drainage composition indicated a 6th order dendritic drainage, heavily dissected, elongated shape, low drainage density (0.10) and a low relief (relief ratio=0.68; relative relief =.002) with a viable potential for agricultural and water resource planning and development.