Mixed-sediment dynamics at a back-barrier beach nourishment

Sand nourishments are increasingly applied to systems where the morphodynamics are driven by mixed hydrodynamic forcing (i.e., tides and waves) rather than by waves alone. Here, mixed-sand deposits are usually retrofitted to inadequate, hard flood defenses to act as a buffer against erosion and eventually failure of such infrastructure. Introducing different grain sizes into a system leads to more complex, differentiated sediment transport, as coarser fractions are mobilized under different conditions than finer fractions (McCarron et al., 2019). By focusing on a nourishment on the leeward side of a barrier island, we aim to find quantitative answers to the questions where, when and how the mixed-sediment composition changes and how that already is and will be expressed in the morphologic evolution of the area.