Feasibility of natural condition to build an artificial island outside the Hengsha East Shoal in the Changjiang Estuary

Shanghai harbor is to be built to an international shipping center,and needs deep-water harbor to meet the continuous increasing cargo transportation demands and larger vessels. Based on nautical charts during 2001 to 2008 and in-situ survey data obtained during 2011 to 2012, this paper discussed the feasibility of natural condition to build an artificial island outside the Changjiang Estuary. The results showed that the sea bed of the study area was stable,and its topography changed little from 2001 to 2008. Seven cross-section profiles showed that there was slight deposition in the upper part but erosion in the lower part, and the transforming depth from deposition to erosion was about -7 m to -10 m. The Hengsha East Shoal expands southeastwards due to the construction of north leading dike of the Changjiang Estuary deep-water navigation channel. The in-situ survey data showed that there was a rotary tidal current during the entire tide phase in winter,and the maximum current velocity was less than 188 cm/s during the flood of spring tide and no more than 134 cm/s during the ebb of neap. The residual current of the observation points showed some differences,e.g.,it was transported into the estuary outside of North Channel,and it was transported toward the sea outside of Northern Passage. The in-situ average suspended sediment concentration was 0.061 kg/m³ to 0.116 kg/m³, corresponding to neap tide and spring tide,respectively. Based on analytical data provided above,we suggested that the hydrodynamic condition and the suspended concentration outside the Changjiang Estuary were suitable to build an artificial island,and weak local siltation could be expected due to rotary tidal current at the east edge of the Hengsha east shoal in the Changjiang Estuary.