New Conversion Model for Areal Sampling of Fluvial Sediments

Abstract

Commonly applied procedures for the evaluation of surface bed-material composition in rivers often include collection of particles by wax or adhesives. These collection procedures produce particle frequency distributions that are not directly applicable to sediment transport models. Appropriate conversion models are required to turn these distributions into volumetric frequency distributions. An empirical exponential formula has been widely used in the past, but it breaks down under some circumstances. Failures are due to conceptual limitations of the empirical approach and to a rough schematization of reality. These problems led to some recent discouragement towards wax sampling. A new conversion model based on the statistical properties of homogeneous mixtures is presented here. The model performs the conversion through evaluation of the sample layer thickness calculated from the total weight of the sample. Results from the proposed model are in good agreement with experimental results obtained from the literature, and compare well with an extensive set of new experimental data.