Mechanism in Turbulence and High‐Frequency Oscillation Due To Wave‐Current Interactions in Qiantang River Estuary, Hangzhou Bay, China

Abstract The world‐renowned tidal bore forms in the Qiantang River Estuary (QRE) and leads to distinctive hydro‐sediment dynamics and the reshaping of coastal geomorphology. This study presents a time series of in situ data of wave, current, and suspended sediment concentration (SSC) in the tidal bore, covering the spring‐neap tidal cycle in 2020. Field data analysis reveals the spring‐neap and flood‐ebb asymmetries in hydro‐sediment dynamics. Current‐induced bed shear stress is mostly larger than that induced by waves. The interactions of semi‐diurnal tide and shallow water tide play a leading role in the tidal asymmetry. Turbulence, particularly ejection and sweep, contributes to the sediment inception and increased turbidity. Peak turbulent kinetic energy (TKE) and strong high‐frequency water level oscillations occur during both flood and ebb tides, driven by different mechanisms. During the flood tides, they are initiated by the breaking of the tidal bore and its secondary waves. During ebb tides, the wave‐current interactions enhance TKE and generate intense high‐frequency oscillations, which is a process previously under‐documented. The findings reveal the dynamic mechanism of turbulence asymmetry and high‐frequency oscillation in water level due to current‐wave interactions and shed light on the evolution of dynamic geomorphology in macro‐tidal turbid estuaries.