Investigating bedload transport under asymmetrical waves using a coupled ocean-wave model

Transport by asymmetrical wave motions plays a key role in cross-shore movement of sand, which is important for bar migration, exchange through tidal inlets, and beach recovery after storms. We have implemented a modified version of the SANTOSS formulation in the three-dimensional open-source Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling framework. The calculation of bedload transport requires inputs that include: water depth, bulk wave statistics (significant wave height, wave period, wave orbital velocity), current velocity at the edge of the wave boundary layer, and sediment density and grain size. While the coupled ocean-wave model computes water density, depth, and bulk wave statistics, we implement a method to calculate current velocity assuming a log profile and using the Madsen formulations for wave-current bottom boundary layer flows. We investigate the sensitivity of the calculation of near-bottom current velocity to model choices and its influence on cross-shore bedload transport. Results are compared to available numerical experiments using coupled fluid and discrete element model (CFDEM) simulations.