Zhidanyuan sluice of Yuan-dynasty, Shanghai area of Yangtze delta: Discussion of its abandonment

The present study examines the rise and fall of the sluice of the Yuan dynasty (1279-1368 AD) unearthed in Zhidanyuan, Shanghai, by means of radiocarbon-dated sediment profiles, sedimentary facies indices and the historical literatures. Magnetic fabric parameters of sediment profiles help reconstruct the tidal creek setting at the sluice site. Our records evidence a fluvially-dominated hydrodynamic setting before sluice construction, but a saltwater intruded setting in the later stage. Magnetic fabric shows a stable flow direction in the upstream of the sluice, implying the fluvial deposition, while scattering flow directions downstream, suggesting interactions between the river flow and tidal currents. It is concluded that the sluice construction was primarily aimed at preventing saltwater intrusion from the Yangtze River mouth, but its operation did not fully fit the high sediment siltation in the channel that occurred after the sluice construction. This weakens significantly the role of sluice operation, leading to its abandonment eventually.