Wave Climate Modeling on the Abandoned Huanghe (Yellow River) Delta Lobe and Related Deltaic Erosion

Abstract The modern Huanghe Delta was formed by a huge amount of sediment from the Loess Plateau accumulating in the shallow shelf of the Bohai since 1855. In 1976, the terminal channel of the Huanghe River shifted southeastward from the Diaokou course to the Qingshuigou course, and significant deltaic erosion has emerged on the abandoned Diaokou delta lobe since then. This article presents a wave climate modeling over the modern Huanghe delta based on the mild-slope equation. The calculated wave characteristics and wave-induced bottom shear stress show good agreement with the coastal erosion of the abandoned Diaokou delta lobe. The cross-shore bathymetric and hydrologic data, suspended sediment distribution, and satellite image were analyzed comprehensively to illustrate the deltaic erosion and its hydrodynamics mechanism. The protuberant topography of the abandoned Diaokou delta leads to a convergence of wave energy in the shallow coastal region, with a water depth ranging from 4 to 10 meters, which results in resuspension of the bottom sediment due to high bottom shear stress. The wave processes reshape the subaqueous delta slope into an equilibrium profile with gentle steepness to match the dynamic regime. The high-turbidity zone revealed by the field investigation and satellite image indicates that the suspended sediment in the high-turbidity zone was resuspended from the bottom but not dispersed from the river effluent. The resuspended sediment was transported by the interaction of waves and strong tidal currents in this area, some of which moved down-slope and accumulated in the lower slope as a result of the reshaping process.