FREQUENCY-DISTRIBUTION OF RIVER BED MATERIALS

The size distribution of river bed material plays an important role in the study of fluvial hydraulic processes. It is not always easy to sa mple the river bed material for the determination of its size distribu tion, but knowledge of the frequency distribution and of bed material sizes can be used to predict its size distribution. Therefore, data on bed material size distributions of 63 streams from 10 different count ries have been analysed to determine the frequency distribution which can be best fitted to them. The log normal distribution cannot be fitt ed to the bed material mixtures when the entire range of sizes is cons idered. The method of power transformation is found to normalize these mixtures. Relationships have been proposed between the parameters of the normalization and the stream slope. These relations can be used to predict the size distribution of the river bed material.