The joint probability distribution of streamwise particle hop distance,
lateral particle hop distance, and travel time constrains the
relationships between topographic change and sediment transport at the
granular scale. Previous studies have investigated the ensemble
characteristics of particle motions over plane-bed topography, however
it is unclear whether reported distributions remain valid when bedforms
are present. Here, we present measurements of particle motion over
bedform topography obtained in a laboratory flume and compare these to
particle motions over plane-bed topography with otherwise similar
conditions. We find substantial differences in particle motion in the
presence of bedforms that are relevant to macroscopic models of sediment
transport. Most notably, bedforms increase the standard deviation of
streamwise and lateral hop distances relative to the mean streamwise hop
distance. This implies that bedforms increase the streamwise and lateral
diffusion lengths and, equivalently, increase diffusive-like fluxes.