潮汐汊道形态动力过程研究综述

潮汐汊道是潮流作用占优势的沉积环境之一。潮汐汊道系统的口门水道往往是天然航道，在海港建设上具有重要性。从动力地貌学的观点来看，口门水道形态特征和演化研究涉及多种关键的海岸动力过程，因而具有重要的理论意义。均衡态下的潮汐汊道的口门过水断面面积与纳潮量之间存在着幂函数关系，当用传统的O′Brien方法来确定幂函数曲线时，指数n的值变化范围较大，这是由于参与统计分析的部分汊道系统未达到均衡态而造成的；而应用沉积动力学方法，所获的n值稳定在1.15左右，能更好地代表均衡态断面面积。在断面形状上，小型潮汐汊道可以形成宽浅水道中镶嵌次级水道的形态，以适应沉积物输运和堆积过程，提高汊道系统的稳定性。因此，小型潮汐汊道具有不同于大型潮汐汊道的时间—流速不对称特征。这些研究结果在小型汊道的开发和整治工程上具有应用价值。由于口门断面形态是与口门水道和潮流三角洲的整体特征及其动态相联系的，因此，今后的研究重点应是水动力条件、沉积物输运和堆积过程、水道形态之间的反馈关系，以及与纳潮海湾充填同步的潮流三角洲的生长过程，从而使水道地貌演化能够被定量地模拟。

Morphodynamic Processes of Tidal Inlets: A Review

Tidal inlets represent a typical tidally dominated sedimentary environment.The entrance channel of an inlet system tends to serve as a natural navigation channel,which is important for harbours.From the viewpoint of morphodynamics,the inlet system is also important because its formation and evolution are concerned with a number of crucial dynamic processes.Under the dynamic equilibrium condition,there is a power law relationship between the cross-sectional area and tidal prism.However,the parameter n in the equation varies considerably for different regions if the O'Brien method is applied.These values do not truly represent the equilibrium condition because some inlet systems involved in the regression analysis have not reached equilibrium.The power law relationship can also be defined on the basis of a sediment dynamic approach,which generates a stable n value(around 1.15).With regard to the shape of the cross-section,small inlet systems are different from large ones.In response to the intense sediment transport and accumulation associated with small inlets,the cross-section tends to have a combined shape,i.e.,a channel with a large depth to width ration scoured into the bed of a wide and shallow channel.Such a shape enhances the stability of small inlets systems and results in more complicated time-velocity asymmetry patterns.These results may be applied to small inlets in coastal development activities.Since the cross-sectional morphology is related to the entire entrance channel and the associated tidal deltas,a thorough understanding of the cross-sectional morphology depends upon further studies of the feedbacks among the hydrodynamic processes,sediment transport and accumulation and the overall morphology of the channel,the coupling of the growth of the tidal deltas and the processes of tidal basin infilling,and the techniques of quantitative simulation of the channel morphological evolution.