Turbulent sediment fluxes along migrating sand dunes

Dunes are the most common bed forms in lowland river channels consisting of sand and gravel, generated by divergences and convergences of sediment over the bed. They act as roughness to the flow leading to increasing water levels. To be able to model dune evolution and dune dimensions adequately, knowledge on flow and sediment transport processes are crucial. Despite the dominance of suspended load in sand bed rivers (Kostaschuk et al., 2009), it is often assumed that bed load is the dominant transport mechanism in generating and migrating dunes. Suspended load is then neglected in modelling dune morphology and evolution for flood management purposes (Jerolmack et al., 2005; Paarlberg et al., 2009). However, several theoretical as well as field studies have shown significant difference in dune mechanisms under bed load and suspended load dominant transport regimes (Best, 2005). Our aim in this study is to understand and quantify the sediment transport distribution along equilibrium sand dunes (Figure 1). In particular, we are interested in the contribution of turbulent sediment fluxes to the total sediment fluxes.