Settling‐velocity distributions and sorting processes on a longitudinal dune: A case study

The processes acting on a longitudinal dune are inferred from the response in the area size‐sorting characteristics of the sediment of the active layer. The sediment size distributions are determined by settling and are best described by a log‐hyperbolic model which provides the most information on size‐sorting processes. Size‐sorting characteristics are markedly different across the low round‐crested part of the dune from cross‐sections of the high more sharp‐crested part. This results in changes in textural parameters along the lee‐side consistent with changes in the lee‐side separation vortex. This is the first time that the effect of wind speed up on the lee‐side is observed to be reflected in the sediment; it can only be detected with the very sensitive log‐hyperbolic parameters.