Modeling the hydrodynamic responses to land reclamation in different regions of a semi-enclosed bay

Abstract

Water area in bays has been reclaimed to meet the increasing land demand for development. Numbers of studies have examined the hydrodynamic impacts induced by land reclamations in semi-enclosed bays such as San Francisco Bay in the U.S., Tokyo Bay in Japan, and Jiaozhou Bay in China. However, they have not compared the impacts of land reclamations taken place in different regions. The Deep Bay in China was selected as a case study to evaluate and compare the hydrodynamic responses to land reclamations that narrows the bay mouth and that causes water surface loss inside of the bay. A numerical model was employed to simulate the hydrodynamics throughout the bay and to examine the differences in impacts through scenario experiments. The model was validated using the observations of water elevation, currents, and salinity. To indicate the changes in hydrodynamics, tidal prism, current field, tidal energy flux, and water age were computed. Simulation results show that narrowing the bay mouth length by 30% with ??% loss of its original water surface area would increase the total energy flux entering the bay by 26 %, while 14% loss of its original water surface area in middle bay would decrease the total energy entering the bay by 23%. The two regions of reclamations have both resulted in substantial but different changes in current field, the spatial distribution of tidal energy flux and water age. For example, the reclamation at bay mouth has increased the current velocity and tidal energy flux at the bay mouth while that inside of the bay has streamlined the current field and increased the velocity in the inner bay. The water age throughout the bay has been reduced by 5.1% and 13.7% respectively in the two scenarios, increasing the water exchange ability of the bay with the adjacent sea. This study is beneficial to other semi-enclosed bays considering land reclamations, facilitating quick and preliminary estimations of hydrodynamic impacts for planning and management.