Wave dynamics in the Yellow River Estuary during cold wave and typhoon events

The Yellow River Estuary (YRE), located in the semi-enclosed Bohai Sea, is characterized by complex shorelines and shallow water depths and is vulnerable to high waves during extreme weather events. Therefore, a dual-nested third-generation wave model was applied to investigate wave dynamics during Typhoons In-Fa (2021) and Mui-Fa (2022) and a pair of cold wave events in 2021 and 2022. The YRE model was refined to reproduce realistic high-resolution terrain and then calibrated against observations at four long-term buoy stations. Results indicate that wave characteristics closely correlate with winds, modulated by local bathymetry. During cold waves, the temporal evolution of the significant wave height (H_s) exhibits double peaks, whereas a single peak is observed during typhoons due to alternative development responses to winds. This resulted in a 1.5-h time lag between H_s and winds. Wind waves primarily dominate sea states, while swells occur after the typhoon passage. Bathymetric refraction plays an essential role in sheltering the southern region of the YRE from remotely energetic swells. Further investigations reveal that depth-induced breaking and whitecapping jointly control wave energy dissipation. Bathymetric heterogeneity and shoaling processes substantially influence wave energy, resulting in wave attenuation and spatial variability. Intense triad wave-wave interactions and wave breaking contribute to increased H_s, causing multiple wave-breaking processes during propagation. The findings in the YRE help enhance the understanding of wave dynamics in similar shallow-water mega deltas and estuaries.