Observations and modelling of a Shoreward Propagating Accretionary Wave (SPAW) at a microtidal beach

Abstract

At straight sandy coasts, wave-induced processes often lead to intriguing alongshore-variable morphology on spatial scales from 10s - 1000s of meters. Observations have shown that the horns of crescentic bars may separate from the bar during storms and subsequently migrate onshore towards the beach during calmer periods as a spatially coherent structure, termed Shoreward Propagating Accretionary Wave, or SPAW. Here, we aim to (1) quantify the morphological evolution of a SPAW and (2) unravel the physical processes underlying its onshore migration and spatial coherence. To do so, we studied onshore migration of a SPAW using a process-based morphodynamic model.