Numerical Investigation of Land Reclamation Effects on Hydrodynamics and Water Quality in Sanmen Bay, China

Abstract

The study found that two large-scale bay reclamations in the 1970s and 2005-2013 significantly impacted the hydrodynamics and pollutant transport in SMB. The model results showed the tidal prism of SMB decreased by 13% and the average velocity and residual current of the main branches became weakened remarkably over the last 50 years. The area of SMB with an average current velocity greater than 0.5 m/s has decreased by 158.19 km2. The amplitude of constituent M2 in SMB has increased, between the mouth and the top of SMB has risen from 0.16m to 0.26m. Additionally, the weakened hydrodynamic field also effected the water exchange capacity and pollutant transport. There was an increase of 7.7 days in the basin residence time during the last 50 years. The distribution pattern of pollutants in SMB was altered by the large-scale reclamation, leading to an obvious area expansion of high concentration of COD and TN. The Shepan Channel, Baijiao Channel and Jiantiao Channel were identified as areas with pronounced susceptibility to water pollution resulting from bay reclamation. The comprehensive analysis of the hydrodynamic evolution in SMB over the last 50 years provides useful insights for future spatial planning and water environmental remediation policies, and contributes to the understanding of effect of reclamation on the water environment in semi-enclosed bays.

Keywords: Sanmen Bay, tidal dynamics, tidal prism, water exchange, land reclamation, pollutant.