天津港水域围垦条件下的水动力变化分析

本研究旨在讨论天津滨海新区的围垦对其附近水域水动力和悬沙输运所造成的影响,并进行定量评估。在天津港南部、北部海域分别选取4个站位进行了全潮水文观测,获取了流速剖面、悬沙浓度剖面数据,并据此计算了底切应力、潮不对称性以及余流。结果表明,底部悬沙浓度与流速、底切应力存在相位一致性,绝大部分站位的沉积物都呈现向岸净输运的趋势,悬沙通量分解显示潮汐捕捉项是该区域悬沙输运的主要贡献项;围垦愈增的2009～2015年,天津港北部潮不对称性增强,向陆的单宽悬沙输运率由20.15 g/(m·s)变至24.92 g/(m·s),而南部海域潮不对称性减弱,向陆的单宽悬沙输运率从37.75 g/(m·s)减小至6.37 g/(m·s)。综上,持续地围垦可能导致天津港附近海域的水动力条件改变,推测北部潮滩淤涨可能加快,而南部淤涨速率减小。

Hydrodynamics and sediment transport in response to seque-ntial reclamations over subtidal waters near Tianjin Port

Extensive reclamations along China''s coast have potentially changed the hydrodynamics and sedimentary processes in the coastal waters. Their influence and underlying mechanisms require careful examination, particularly for waters near major ports where sediment siltation in navigational channels is a major concern. We collected monitoring data at eight stations during 2014-2015 in the vicinity of Tianjin Port, around which sequential reclamations were conducted over recent decades. We calculated the bottom shear stress, tidal asymmetry, and residual current, and compared these with another dataset collected during 2009, aiming to quantitatively examine the influence of the reclamations during 2009-2015 on the hydrodynamics and sedimentary processes in this region. The results of the observed data indicated that bottom suspended sediment concentration varied in phase with the velocity and bottom shear stress. Comparison between 2009 and 2015 datasets revealed opposing trends for southern and northern Tianjin Port areas. In the northern area, the tidal asymmetry became stronger and landward sediment flux increased from 20.15 to 24.92 g/(s·m), while in the southern area, the tidal asymmetry became weak and landward sediment flux decreased from 37.75 to 6.37 g/(s·m). The net sediment fluxes were in the landward direction for all monitoring stations, implying that the tidal flat near Tianjin Port will continue to accrete. The decomposition of the sediment flux suggested that tidal pumping was the major contributing factor in the net landward sediment flux. The opposite trends between northern and southern area suggested that the tidal flat accretion rate was likely to be enhanced in the northern area and reduced in the southern area because of the new reclamation.