Study On Dynamical Characteristics Of The Water Environment During Estuarine Reclamation

It is very significant for reclamation to meet new land requirement in estuarine cities with increasing population and decreasing land due to industrialization and urbanization. Nevertheless, the process of wave propagation, tidal movement and sediment transport, which provide the basic forces for reclamation, are very complicated in an estuary with irregular bedform and coastline.This dissertation focuses on investigating the impact of reclamation in Oujiang River estuary on dynamical characteristics of the water environment, and is carried out on the basic analysis of the observed data of water-sediment environment conditions and tidal flats processes. Moreover, it also employs a numerical model to study the sediment transport under currents and waves, which supplies an effective method for complicated estuary regulation and strong technical support for feasibility demonstration of the project.Comprehensive impact of the finished projects is first examined, which include submerged dyke of Lingkun, North dam of Lingni and the first phase reclamation of Wenzhou Shoal on estuarine water-sediment environment and evolution of the topography based on the measured data. From the gotten rules, the impact of the second phase reclamation is predicted and summarized into two points. First, the dynamical characteristics of the tidal currents have vital effect on the estuary processes. The direction of Wenzhou Shoal is nearly parallel to the main flow in the North and South mouths, where the reclamation would only partly change the tidal dynamics. The second phase of the reclamation will increase the erosion in the South mouth, but won't remarkably affect the stability of estuary conditions, which corresponds to the inner processes. Second, it is highly recommended to enhance the sediment deposition and prevent the erosion in the second phase reclamation, and is on the whole in a dynamic equilibrium state of erosion and deposition.A multifactor mathematical model is established to predict the sediment transport, which is based on a rectangular mesh and the finite difference method, and consists of a wave module, a current module, a sediment transport module and a bedform topography-change module. All the radiate force, shear force, sediment transport capability of waves and the breaking effect are taken in account. The model provides an effective numerical technique for estuarine management and estuary regulation.In addition, present work has significant practical value in engineering, and numerical model has been applied for the first time to the second phase reclamation of Wenzhou Shoal. The results are as follows: (1) Two plans have been compared: plan I and II, which is with or without gap respectively. The velocity decreases widely in the silting-promotion zone, which is conducive to the sediment deposition. In terms of hydrodynamic condition of sedimentation and slit-promoting effect, plan I with an average silty depth of 0.59m is a little better than the gapped plan II with 0.51m. (2) The flux discharge and flux rate of the North and South river mouths are barely changed by the second phase project. There is no effect on Shatou Channel and Yueqing Bay, or negative effect on the port sea-route. Furthermore, in the process of implementation more measurements should be taken to prevent erosion. At the same time, it is needed to study more about the responses of the reclamation to preserve the ecological environment in the estuary.