Sheetflow Sediment Transport

Long-term goals are to understand the physics of sediment transport by waves and currents and to use that understanding to predict the bathymetry and sedimentology of the nearshore. Continued development, refinement, testing and production simulations were conducted using a discrete-particle computational model for sheetflow sediment transport. The model simulates the motion of individual solid particles immersed in a rapidly shearing viscous fluid, in which momentum transfer is dominated by solid-particle Simulations successfully reproduce patterns of sorting (segregation of grains by size and density) observed in the nearshore; in particular, grain-size distributions become increasingly coarse in the on-shore direction. Fine-grained layers analogous to laminations form in the simulations at depths within the bed corresponding to the maximum extent of bedload motion. Comparison of simulation results with sedimentary structures in cores taken during the Duck94 Nearshore F (1) Fine sands at Duck may not meet model assumptions for collision-dominated transport, and should be addressed in future models. (2) Non-planar bed configurations, principally megaripples, appear to persist (metastably?) under hydrodynamic conditions thou Thus determining the origin and stability of megaripples is critically important to predicting transport and bathymetric evolution.