Impacts Of Reclamation On The Erosion And Deposition At The Coast Of Zhanjiang Bay Entrance

Reclamations in the estuaries and coastal areas are important to the developmentof human society and the proper marine engineering carries great significance to thelocal city’s economic development. However, the excessive unscientific marineengineering would exert negative impacts on the hydrodynamic environment andsediment of local coastal waters, which receives much concern nowadays.In recent years, the erosion has become more serious along the East Islandshoreline off the Zhanjiang Bay. In order to examine whether the reclamation hassome influences on erosion characteristics and the morphologicall evolution and toprovide a theoretical basis and reference for the similar projects in future, with the aidof MIKE21numerical model the research here established a tidal current field modelof the Zhanjiang Bay and its adjacent waters based on its topography, hydrographicalmeteorology, tidal level, sediment and other information over many years. Thecalibration results are in consistence with the measured data and the overall status ofthe Zhanjiang bay fluctuation trend remained the same after the reclamation,nevertheless, the flow velocity and direction of the nearby waters changed in variousdegrees, for instance, the flow velocity in the Bay-mouth tended to be smaller and theebb sediment concentration was also reduced.After the reclamation construction, some deposition occurred in the works areasof the bay, the erosion at the east coast of the East Island became serious after theengineering construction and an erosion area was formed both in the south of theouter waterway and in the north of the shoal. In addition, the paper here makes aprediction and analysis of the tidal water, erosion and deposition in the Zhanjiang Bayfrom the perspective of near-term, medium-term and long-term reclamation planning. Reclamation leads to the reduction of sediment sources, with less and less sedimenttrend to the offshore because of the intensification of deposition and the sediment istransported from outside to inside of the Bay, which exacerbates the erosion along theshoreline outside the Bay.The research indicates that the northern shoal is eroded and reduced due to thenorthward movement of Jianjiang River estuary and the direction of the shoal ischanged from the northeast-southwest to northwest–southeast; at the same time, thesouth of the outer waterway is eroded in the northern part while its southern part isdeposited and the direction changes from the northwest-southeast to the east-west.Besides, the reclamation construction has exacerbated the erosion in the southernshoal and at the east coast of East Island.