Sediment transport controls the morphology of rivers, estuaries and coastal oceans. It is by nature a two-phase problem in which fine grain-scale processes such as collisions, segregation, or enduring contacts and turbulent-particle interactions locally control particle transport. Particulate geophysical flows is a truly multi-scale phenomenon with length-scales ranging from the submillimeter of a sand grain to the kilometer scale of a river section. This question of scale will be central in the workshop with the aim to foster the transfer of the most recent advances on the understanding of these fine-scale processes and to establish research perspectives.