Extended Data Fig. 3: Additional granular materials and their shape properties.

a, Tempered glass chips. b, Shell fragments. c–f, Natural gravels 2–5, respectively, with differences in gross grain shape, angularity and surface properties. All materials have similar average sizes and densities to each other and to the five granular materials used in the flume experiments (Extended Data Table 1). g, Normalized coefficient of friction, μ*, as a function of the Corey shape factor for the five granular materials used in the flume experiments and the six additional granular materials shown in a–f. h, Normalized coefficient of drag, C*, as a function of Corey shape factor for the same 11 granular materials as in g. i, The ratio of the two normalized coefficients from g and h, C*/μ*, as a function of Corey shape factor for the same 11 granular materials as in g and h. The parameters C* and μ* tend to vary similarly for many of the measured materials, such that their ratio is close to one. However, several materials have ratios of C*/μ* distinctly different from one. This highlights the difficulty of guessing the net effect of grain shape on sediment transport based on qualitative inspection of grains. Error bars show one standard error of the mean.