Impacts of a storm on the erosion process of a tidal wetland in the Yellow River Delta

Accretion rates of estuarine tidal flats have strongly decreased globally due to the combined impacts of sea-level rise, reduction in sediment supply, and human interventions. Storms and associated high-energy activities influence sedimentary processes on tidal flats. A better understanding of the role of storm events on the evolution of tidal flats can facilitate better coastal management. This study assesses the impacts of storms on intertidal sedimentary processes. We monitored tidal water levels, tidal currents, waves, suspended sediments, and morphological changes of the eroding Diaokouhe lobe in the Yellow River Delta during and after a storm event. The estimated bed shear stress during the storm event (average 1.60 N/m²) was much higher than that during fair-weather conditions (average 0.71 N/m²). However, surface erosion of tidal flats was negligible during the storm, which was ascribed to the high critical bed shear stress owing to the compacted bed surface. The tidal flats were inundated for a longer time with a higher water depth and higher suspended sediment concentrations (average 1.13 g/L) during the storm, indicating sediment supply from the subtidal zone and adjacent sea. These conditions, namely moderate storm strength, high sediment compaction, and high sediment availability, led to deposition rather than erosion on the intertidal flats. Overall, the results imply that storm-induced erosion is less likely to occur on tidal flats with rich sediment supply and high erosion resistance.