[Objective]Ocean engineering has a certain influence on the deposition-erosion envi﹣ronment of harbor or gulf.Ocean engineering construction in Qinzhou Gulf was more frequent in the past 20 years.Understanding the changes of topography in this region can provide a ref﹣erence for ocean development.[Methods]Field investigation,data analysis and numerical simu﹣lation have been used to study this issue.[Results]In recent twenty years,large-scale develop﹣ment activities led to the gulf area significantly reduced in Qinzhou Gulf.The shoreline change exhibited smooth trend,and artificial shoreline gradually replaced natural shoreline.Reclama﹣tion made 0 m isobath blocked at the gulf eastern shoal,meanwhile 10 m isobath connected to the mouth of the gulf due to east channel construction.The gulf sediment mainly came from three aspects:Continental runoff,marine transportation and coastal marine construction. The distribution of sediment concentration changed in different seasons,but overall was a low sediment concentration scope in the gulf. Numerical simulation results showed that the gulf generally exhibited stable situation with mi﹣cro-erosion and micro-siltation,but seabed erosion was obvious in the jet waters of Longmen.[Conclusion]In the east of Qinzhou Gulf,erosion and deposition environment in some waters had undergone a significant change due to large-scale reclamation.The shallow status in the middle of east Sandun road turned to be obvious erosion from weak deposition,and the annual erosion was up to 0.07 m.%【目的】海洋工程对海湾港口的冲淤环境有一定的影响，而近20多年来钦州湾海洋工程建设较为频繁。了解该地区地形地貌的变化，可以给海洋开发提供参考。【方法】采用外业调查、资料分析与数值模拟等手段对钦州湾围填海与海洋开发建设引起的岸线变迁、地形改变、泥沙冲淤等问题进行研究。【结果】近20多年来，钦州湾大规模海洋开发活动导致海湾面积明显缩小，岸线变化呈现平顺化趋势，人工岸线逐渐替代自然岸线。钦州湾东部浅滩因填海使得0 m 等深线被阻断，而10 m 等深线因东航道扩建得以贯通至湾口。钦州湾的泥沙主要来源于陆相径流、海相输送以及近岸海洋工程建设等几个方面；含沙量分布随季节变化而不尽相同，但总体属低含沙量范畴。数值模拟结果显示，钦州湾总体呈现微冲微淤的稳定态势，但在龙门水道等急流水域，底床冲蚀较为明显。【结论】在钦州湾东部，因大规模围填海建设，导致局部海域的冲淤环境发生显著改变：三墩公路东侧中部的潮滩，由微弱淤积状态转变为明显冲蚀状态，年冲刷量可达0.07 m。
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