Effect of Human Interference on the Change of Mean Water Level at the Entrance of North Branch of the Yangtze Estuary

The abnormal trend of mean sea level (MSL) at Lianxinggang station located at the entrance of the North Branch (NB) of the Yangtze Estuary (YE) in 2007–2015 was observed. The MSL was falling in that period, which is opposite to that in the nearby area, as well as to the global MSL rising trend. Various aspects are investigated to get the insight of such falling trend of the MSL at the entrance of the NB based on a numerical hydrodynamic model for the estuary. Model results show that the Middle Narrowing project tremendously decrease the width of the NB resulting more flood dominate characteristics. The flow diversion ratio decreases about 8% after the narrowing project with a result of less discharge flows to the sea through the NB, as well as less tidal discharge powering into the estuary by this outlet. This reveals that the change of topography in the NB due to human interference affects the MSL trend.