Aeolian sand transport influenced by tide and beachface morphology

Abstract

Beach aeolian sand transport is one of the most complicated but significant processes in beach-dune interactions. Focusing on tidal and morphological effects, field observations over several tidal cycles were carried out successively on two macrotidal and gently sloped beaches to clarify the characteristics, dominant factors and possible mechanism of aeolian sand transport in the intertidal zone. The results show that there is a clear “time window” for aeolian sand transport in the intertidal zone under the joint effect of tidal action and ridge morphology. During ebb tide, the factors controlling the initialization of intertidal aeolian sand transport shifted sequentially from ridge inundation (controlled by tide) to seepage, capillary and drying processes. During the time window, the fluctuations of dew point appear to be a good indicator of the variations in aeolian transport rates. During flooding, the dominant factor for the cessation of intertidal aeolian sand transport is inundation (controlled by the tidal elevation). Further exploration shows that for the wide and gently sloped beachface, the presence of intertidal ridges may be necessary for the aeolian process to entrain and transport sand from the moist intertidal zone. Finally, a conceptual model for the intertidal aeolian sand process under the joint effect of tide and ridge morphology is proposed.