Contribution of swash processes generated by low energy wind waves in the recovery of a beach impacted by extreme events : Nha Trang, Vietnam

Nba Trang beach experiences southerly sediment drift during winter monsoons and northerly sediment drift during summer monsoons. In addition, the area is likely to be impacted by tropical storms or typhoons. Due to the presence of islands at the south east border of the bay, the strongest impact on the shoreline apart from extreme events is due to NE swell from October to April. The mechanism responsible for the sediment drift generated by low energetic locally generated wind waves is insufficiently understood. It involves the functioning of the swash zone for weak conditions. Two field experiments were scheduled before and after the period of cyclonic activity. The aim of the first experiment was to describe the site's bathymetry and the geomorphology of the upper beach and hydrologic functioning of the bay. A new method of measurements in the swash and surf zone based on processing of data extracted from HD video processing was tested successfully for wind wave conditions in a reflective beach. Here, we present some data obtained during the field experiment at different time scales. The data provides a first quantification of the impact on sediment transport from typical low energy conditions which are encountered during spring and summer in Nha Trang