Effects of large-scale embankments on the hydrodynamics and salinity in the Oujiang River Estuary, China

Humans have built many large-scale embankments in estuarine areas to promote economic development. These projects have various adverse effects on marine environments because of changes in tidal circulation and salinity. This study uses data from large-scale field observations and three-dimensional mathematical models to investigate changes in hydrodynamics and salinity distribution after the construction of the Ling-Ni Embankment, a large-scale embankment for continuous islands in China. After the construction of the Ling-Ni Embankment, the exchange of seawater between the two sides of the embankment was hindered and the flow velocity changed. The freshwater upstream of the Oujiang River extended farther up the northern channel than before the project. The difference between the salinities of the southern and northern channels increased as the salinity of the northern channel decreased. The salinity was higher in the southern channel than in the northern channel. Thus, several significant hydrodynamic and salinity changes occurred after constructing the Ling-Ni Embankment. Consequently, more attention should be given to the environmental changes that are induced by blocking projects. The three-dimensional mathematical models that are used in this study serve as effective tools to evaluate the advantages and disadvantages of man-made embankments. These models may also benefit tidal circulation monitoring and management in estuarine areas.