Probabilistic-Deterministic Modelling of Swash Zone Morphology

A probabilistic-deterministic model for swash zone sediment transport is presented and applied to predict cross-shore beach profile change under random waves. For accretionary conditions, inclusion of a random wave approach is essential for accurate representation of berm building processes. The model provides good estimates of beach volume changes for small scale laboratory experiments and sediment overwash volumes on a natural beach. Future modeling improvements are discussed, notably the inclusion of pre-suspended sediment, sediment pickup and long wave influences. Field and laboratory data show that sediment is advected into the swash zone from much further offshore than predicted by the classical swash solution, which increases uprush suspended sediment flux. Conversely, backwash suspended sediment flux may be limited by hindered pickup which may occur when the thickness of the backwash sheet flow layer becomes large relative to the flow depth.