Grain Size Distribution of the Sediments from Odi River, Bayelsa State, Nigeria

Ten samples from Odi River bed were collected by divers at different locations and sent to the laboratory for granulometric analysis. Samples were dried to remove moisture content and poured into a set of BSS standard sieves and mechanically vibrated for at least fifteen minutes to enable the grains to separate into their different sizes. Textural and statistical parameters were then calculated from the results of the particle size distribution. The result shows that the grain size ranges from -2 φ – -1 φ (granules) to 3 φ – 4 φ (very fine sand). The average mean of the population is 0.89 φ, with a modal class in the 1 φ – 2 φ size grade. The average sorting value is 1.26 σ which indicates a poorly sorted population. Skewness varies through the population, but, the average skewness is -0.16 (Negatively skewed). 60% of the sediments range from leptokurtic to extremely leptokurtic, 10% are very platykurtic, 10% are platykurtic and 20% are mesokurtic. Traction and saltation transport modes were inferred from the cumulative curves of the sediments. The plot of skewness versus kurtosis shows the energy of deposition to be fluctuating between high and low, depositing coarse and fine sands facies respectively. The grain size distribution is observed to be finer downstream.