ABSTRACT
The Yangtze River near the city of Nanjing contains many islands inside the river channel. The Baguazhou Island divides the Yangtze River into two branches in the north of Nanjing. The ratio of the flow rates through the two branches has been experiencing some unwanted changes in recent years. The flow rate in the left branch has dropped to only around 13% of the total flow rate of the Yangtze River, which causes siltation and may eventually lead to the disappearance of the left branch. However, the area along the left branch of Yangtze River has witnessed rapid economic development, and left branch of the River offers convenient navigation and water resources in this process. The decline of the left branch is a major threat to the continuous prosperity in this area. In order to increase the flow through the left branch, some hydraulic structures have been constructed at the head of the Baguazhou Island to guide more water to the left, which achieved limited success. This paper reports on the laboratory experiments and numerical simulations carried out to find the most effective design of a diversion dike in front of the Baguazhou Island to regulate the flow. We first compared the numerical results and the experimental and field measurements in the present conditions, and good agreement was reached. Then parametric study was conducted to optimize the two geometric parameters of the diversion dike: its orientation and length. Considering the financial and technical constraints of the construction of such a dike, recommendations were provided at the end of the study regarding the shape of the diversion dike and its effectiveness.
