Grain-Shape Analysis--A New Method for Determining Representative Particle Shapes for Populations of Natural Grains

摘要

The size sorting and shape sorting of gravel bedload by running water often is investigated using identifiable tracer grains that represent the grains within the riverbed. A new, robust, and reproducible method is described for the objective selection of three-dimensional shapes that are representative of the variety of shape within any whole sample. Widespread adoption of the method would ensure comparability between the shape-sorting results of different experiments. The approach identifies average and extreme grain shapes from natural gravel samples. Importantly, tracer dimensions are derived that form shapes with equal volume, thus ensuring that the shape of the tracers is the only transport variable. The method is tested on seven gravel samples from a range of fluvial, beach, and scree-slope environments as well as different sieve sizes.