Conversions of Surface Grain-Size Samples Collected and Recorded Using Different Procedures

Abstract

Abstract:Information about the grain-size distribution of the surface layer of sediment exposed on river beds is often critical in studies of fluvial hydraulics, geomorphology and ecology. A variety of sampling and analysis techniques are in common usage which produce grain-size distributions that are not directly comparable. This paper seeks to explore the appropriate conversions between different types of surface grain-size sampling methods. This is particularly timely in the light of increasingly widespread use of automatic and semiautomatic image-based measurement methods, the comparability of which with conventional measurement methods is relatively poorly constrained. For conversions between area-bynumber (paint-and-pick) and grid-by-number (pebble count) samples, the empirically-derived conversion factor (±2.2) was found to be greater than that predicted by the Kellerhals and Bray model (±2), but the errors associated with using the value predicted by the model were small (3.8% in mm). For conversions between areal samples recorded by count and weight, 2 the empirically-derived conversion factor was approximately ±2.9, but the use of the value predicted by the Kellerhals and Bray model (±3) resulted in only small errors (5.2% in mm).Similarly, for conversions between image-based grain-size distributions recorded in area-bynumber and grid-by number form, the emipirically-derived conversion factor was ±1.9, but the using the model value of ±2 resulted in only small errors (4.1% in mm). Although these results are specific to the datasets analysed, the variety of sedimentary conditions included gives us confidence that the results are representative.

Transferable wavelet method for grain‐size distribution from images of sediment surfaces and thin sections, and other natural granular patterns

“…The reader is referred to Kellerhals & Bray () and Graham et al . (, ) for a comprehensive review of these phenomena, as well as conversion procedures which are applicable for grain‐size distribution measurements from geometrical algorithms such as Graham et al . ().…”

Biogeomorphic influence of soil depth to bedrock, volcanic ash soils, and surface tephra on silversword distribution, Haleakalā Crater (Maui, Hawai'i)

“…Comparisons of results with those obtained by in situ clast measurements have shown little to no statistical differences between techniques (Caine, 1969;Adams, 1979). Some authors have measured the particle b axis (Adams, 1979;Sime and Ferguson, 2003;Graham et al, 2012); others have chosen the a axis (Caine, 1969;Iwata, 1983;Ibbeken and Schleyer, 1986;Pisarska et al, 2011;Pérez, 2012). A 100 × 50 cm graduated frame was laid on the ground near the quadrat center and photographed around noontime, to minimize shading.…”

Estimating the settling velocity of bioclastic sediment using common grain‐size analysis techniques

“…The results of DGS are an ‘area by size’ measure of grain diameter, whereas sieve, laser diffraction and settling tube are a ‘volume by size’ or ‘mass by size’ measure. Although these two measures of grain diameter are not directly comparable, there exists a common method to convert from areal‐based to volume‐based measures of grain size (Diplas & Sutherland, ; Graham et al ., , ): …”