现行黄河三角洲叶瓣蚀积演化对动力环境的影响

现行黄河三角洲地貌演化已使河口动力环境发生了显著变化，但黄河改道清8汊后，现行河口以及废弃河道清水沟河口动力环境如何变化尚不清楚。基于1976、1995和2002年黄河三角洲实测水深数据，应用Delft3D模型对清水沟流路不同时期冬夏季河口动力环境进行了数值模拟，定量研究了黄河三角洲地貌演化对动力环境的影响。模拟结果表明，黄河现行三角洲地貌演化导致河口动力环境发生了显著变化，1976年河口动力环境弱，随着河嘴向海突出，1995年河口处涨、落潮最大流速较1976年增长了约60%~90%，潮致剪切力增大约2倍，冬季大风条件下浪致剪切力较1976年增加1个数量级，2002年黄河改道清8汊入海后，现行河口处涨、落潮最大流速较1995年减小约20%，潮致剪切力减小1/3，冬季大风条件下浪致剪切力是1995年的1~2倍，而废弃河道河口处涨、落潮最大流速较1995年减小约20%~40%，潮致剪切力减小约20%。黄河三角洲动力环境变化也显著影响了入海泥沙的搬运与沉积，造成清水沟河口呈“南肥北瘦”形态，且废弃后侵蚀速率不断降低。同时，地貌形态与动力环境之间的耦合关系对黄河三角洲冲淤模式的转变有重要影响。

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.