黄河现行与废弃河口海岸地貌动力作用差异的数值研究

NUMERICAL STUDY ON THE DIFFERENCE OF GEOMORPHIC DYNAMICS BETWEEN THE CURRENT AND ABANDONED ESTUARY COASTS OF THE YELLOW RIVER

波浪是塑造黄河三角洲河口与海岸地貌的重要动力因素之一。基于Delft3D模型耦合水动力与泥沙输运模块,模拟了黄河不同入海水沙条件下的表层悬沙浓度的分布变化,通过悬沙浓度差异值(Di值)定量研究了黄河清水沟流路现行河口与废弃河口之间的海洋动力差异,进而揭示了潮流与波浪在不同时期黄河三角洲地貌演变中的塑造作用。研究结果表明,在不同时期不同入海泥沙条件下,废弃河口及其近岸区域Di值普遍较高且为正值;但现行河口近岸的Di值分布普遍为负值。在废弃河口波浪使已沉积的粉砂、黏土起动、再悬浮,由潮流将其搬离海岸,从而使海岸发生蚀退;但现行河口由于大量黄河粉砂、黏土快速输入,潮流无法在短时间内将其全部搬离河口,进而使河口及两侧海岸向海淤进。比较而言,波浪在废弃河口及海岸的地貌作用较强,在现行河口相对较弱。这些研究结果对了解黄河三角洲动力地貌演变机理有重要的理论价值。

Waves are one of the important driving factors that shape the estuary and coastal landscape of the Yellow River Delta.Based on the Delft3D model coupled hydrodynamic and sediment transport module,this study aims to simulate the variation of surface suspended sediment concentration in the Yellow River under different seawater conditions.The current estuary and waste of the Qingshuigou channel of the Yellow River are quantitatively studied by the difference of suspended sediment concentration(Divalue).The differences in ocean dynamics between the estuaries reveal the shaping of tidal currents and waves in the evolution of the Yellow River Delta in different periods.The results show that the suspended sediment concentration difference along the abandoned estuary and ts nearshore area is generally high and positive under different sediment conditions in different periods.However,the Di value in the current estuary is generally negative.The abandoned estuary waves resuspend the deposited silt and clay,and move it off the coast by the tidal current,thus causing the coast to eclipse.However,due to the rapid input of a large number of Yellow River silt and clay,the current estuary cannot transport all of them out of the estuary in a short period of time,and thus the estuary and the coasts on both sides are deposited into the sea.In comparison,waves have a strong geomorphological efect on abandoned estuaries and coasts,and are relatively weak in the current estuary.These findings have important theoretical significance for understanding the evolution mechanism of dynamc geomorphology in the Yellow River Delta.