Numerical Study on the Difference in Geomorphic Dynamics between Current and Abandoned Estuarine Coasts of the Yellow River Delta

Dong, C.; Zhan, C.; Lin, Z.; Yi, F.; Zhu, J.; Shi, H., and Wang, Q., 2020. Numerical study on the difference in geomorphic dynamics between current and abandoned estuarine coasts of the Yellow River Delta. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 227–235. Coconut Creek (Florida), ISSN 0749-0208.Waves are the important driving factors that shape the estuary and coastal landscape of the Yellow River Delta (YRD). Changes in wave dynamics can affect the evolution of landforms, causing erosion or accumulation between coastal areas. In this study, the variation in suspended sediment concentration in the Yellow River under different seawater conditions is simulated based on the Delft3D. Quantitative study of the difference in ocean dynamics between the current estuary and abandoned estuary of the Qingshuigou channel in the YRD is conducted based on the difference in suspended sediment concentrations (Di), which revealed the shaping effect of tidal currents and waves in the evolution of the YRD during different periods. The results show that under multiple sediment and inflow conditions during different periods, the Di-value of the abandoned estuary and its nearshore area is generally high and positive, which indicates that the coastal dynamics of the abandoned estuary are dominated by waves. However, the distribution of Di-value in the current estuary is generally negative, indicating that the coastal dynamics of the current estuary are dominated by tidal currents. In the abandoned estuary, waves restarted and resuspended the deposited silt and clay, and they were moved away from the coast by tidal current, thus causing coastal erosion. However, due to the rapid input of a large amount of sediment in the current estuary, the tidal current could not move all of it; deposition occurred in the estuary and along both sides of the coast, extending the estuary into the sea. By comparison, the waves have a strong geomorphological effect on the abandoned estuary but are relatively weak in the current estuary. These findings have important theoretical value for understanding the evolutionary mechanism of dynamic geomorphology in the YRD.