EVOLUTION OF THE ACTIVE DELTAIC LOBE OF HUANGHE RIVER AND ITS RESPONSE TO HYDRODYNAMICS

The hydrodynamics of the area off the Huanghe River delta is the main factor to change the morphologic evolution of the deltaic lobe. However, since the deltaic river channel shifted from the Qingshuigou to the Qing 8 course in 1996, the changes in hydrodynamics off the active river mouth and abandoned deltaic lobe have not been well studied. In this study, a 3D high-resolution baroclinic model was set up for the active Huanghe delta lobe based on the Delft-3D FLOW and WAVE modules. By altering the topography of the Huanghe delta in different years, the effects of morphology on hydrodynamics are studied. Significant changes in hydrodynamics occur due to morphology evolution in the water area off the active Huanghe deltaic lobe. Compared with those in 1976, the maximum velocities of flood and ebb currents in 1995 had increased by 60%-90% as the Huanghe river mouth protruding seawards. The tide-induced bed shear stress had tripled in 1995 and the wave-induced bed shear stress under strong wind in 1995 was one order of magnitude higher than that in 1976. The hydrodynamics weakened from 1995 to 2002 except for the wave-induced bed shear stress which was enhanced significantly off the present river mouth. Meanwhile, the variations in hydrodynamics had a feedback on morphology evolution. The strengthening of wave-induced shear stress could cause evident resuspension of sediment, and the increase in current velocity favored the lateral transport of the sediment. In addition, the coupling effects between them had an important impact on the transformation of evolution pattern of the active Huanghe delta lobe and on the morphology of the Qingshuigou course.