Dynamics governing the response of tidal current along the mouth of Jiaozhou Bay to land reclamation

Abstract

Data collected from the previous studies show that the tidal current along the mouth of Jiaozhou Bay (JZB) appears to have weakened, whereas the spatial asymmetry (stronger flooding in the north region and stronger ebbing in the south region) has remained nearly unchanged during the past several decades of large-scale land reclamation. This study is conducted to explain the underlying dynamics for this phenomenon. The analytic evaluation of the tidal motion indicates that the tidal current in a small coastal bay such as the JZB is linearly proportional to its length (L), if L is far less than one-quarter of the tidal wave length. This relation suggests that the decrease in tidal current speed in JZB mouth results from the land reclamation within the Bay. Also, the relationship between bay areas and tidal current along the JZB mouth can be derived. The results of this simple theoretical method for predicting the change in mean tidal current amplitude after the land reclamation largely agree with previous three-dimensional (3-D) modeling studies. It is also found that the spatial asymmetry of the tidal current along the JZB mouth is controlled by the sharp headland (the local factor). The unchanged shoreline around the headland leads to the stable spatial asymmetry of the tidal current. The weaker tidal current can explain the weaker residual current, and the unchanged asymmetry of the tidal current explains the unaltered pattern of inflow over the north region and outflow over the south region for the tidally induced residual current along the JZB mouth. Key Points: Decrease in tidal current speed in JZB mouth is owing to land reclamation Spatial asymmetry of the tidal current is controlled by the sharp headland Tidal residual current changes with the change in tidal current accordingly