大目涂海域含沙量分布及其对滩涂围垦的响应研究

发布时间：2018-11-15 16:30

【摘要】：含沙量是反应泥沙运动的重要物理量,了解海域含沙量分布变化特征对于认识和掌握泥沙运动规律具有重要的理论意义。而对于近岸滩涂海域,作为海域泥沙补给的重要来源之一,滩涂的围垦可能导致近海海域水动力条件及海相泥沙输入的改变,最终对海域含沙量产生深远影响。因此,研究滩涂海域含沙量对滩涂围垦的响应也是十分必要的。本文根据2011年冬季、2012年夏季及2014年秋季实测水沙资料,通过比较、归纳等方法分析了大目涂海域含沙量的潮周期变化、季节差异、空间分布特征并探讨了其形成原因。应用MIKE21建立波流共同作用的二维水沙耦合模型,分别模拟了大目涂海域原始、lm等深线围垦、3m等深线围垦后的悬沙场分布情况,并对模拟结果给予了分析与解释。研究结果表明:大目涂海域潮流以顺时针旋转流为主,近岸受地形影响呈一定的往复性,潮流流向基本与岸线走向一致,近岸落潮流占优。海域潮动力分布具有“近岸小、外海大,北部小、南部大,冬季小、夏季大”的特点。驻波特性显著。大目涂海域近岸与中部海域含沙量的潮周期变化以无峰型为主,远岸海域呈明显的单峰型,仅近岸南部海域为双峰型。近岸海域涨、落潮含沙量均值涨潮期多大于落潮期,远岸海域则多出现落潮期大于涨潮期的现象。无峰型和双峰型的海域含沙量垂梯度向随流变化显著,单峰型海域则表现为“落潮含沙量高、垂向梯度大,涨潮含沙量小、垂向梯度小”的特点。冬季含沙量剖面形态呈“准直线型”、秋季呈“斜线型”、夏季呈“指数型”。按lm等深线和3m等深线围垦滩涂未改变海域含沙量分布的基本格局,但对近岸海域含沙量影响较大,中部海域次之。其中lm等深线围垦使海域含沙量变幅最大达13%,3m等深线围垦对应的含沙量变幅最大为26%。大潮期含沙量变化普遍大于小潮期,冬季含沙量变化明显,夏季工程影响小于2%,暂可忽略。
[Abstract]:Sediment concentration is an important physical quantity reflecting sediment movement. It is of great theoretical significance to understand and master the law of sediment movement by understanding the characteristics of sediment concentration distribution in sea area. As one of the important sources of sediment recharge, the reclamation of tidal flat may lead to the change of hydrodynamic condition and marine sediment input in the offshore area, which will have a far-reaching effect on the sediment content in the sea area. Therefore, it is necessary to study the response of sediment content in tidal flat area to tidal flat reclamation. Based on the measured data of water and sediment in the winter of 2011, summer of 2012 and autumn of 2014, the tidal cycle variation, seasonal difference and spatial distribution characteristics of sediment concentration in the large area are analyzed by means of comparison and induction, and the reasons for its formation are discussed. A two-dimensional coupled model of water and sediment interaction between waves and currents is established by using MIKE21. The distribution of suspended battlefield after the reclamation of the large grain-coated sea area, the lm isobath reclamation and the 3m isobath reclamation is simulated, and the simulation results are analyzed and explained. The results show that the main tidal current in the area is clockwise rotating current, the inshore is affected by topography, the direction of tidal current is basically consistent with the trend of shoreline, and the inshore tidal current is dominant. The tidal dynamic distribution in the sea area is characterized by "small inshore, large offshore, small northern, southern, small winter and large summer". The standing wave characteristic is remarkable. The tidal cycle variation of the near shore and the middle part of the sea area is dominated by the non-peak type, the far shore sea area is obviously single peak type, and only the southern coastal area is of the double peak type. In the coastal waters, the mean value of the sediment content in the falling tide is larger than that in the lower tide, and the lower tide is larger than the high tide in the far shore. The vertical gradient of sediment concentration in the non-peak and bimodal sea areas varies significantly with the current, while the single-peak sea area is characterized by "high sediment content in the falling tide, large vertical gradient, small sediment content in the high tide and small vertical gradient". The shape of sediment content profile in winter is "quasi-linear", "diagonal" in autumn and "exponential" in summer. The basic pattern of sediment concentration distribution in the coastal area has not been changed according to the lm isobath and 3m isobath reclamation tidal flat, but it has a great influence on the sediment content in the coastal area, followed by the middle sea area. The maximum variation of sediment content in the sea area by lm isobath reclamation is as high as 13 ~ 3 m. The maximum range of sediment content is 26m for the reclamation of isobath with lm isobath. The variation of sediment content in spring tide period is generally greater than that in low tide period, and the change of sediment content in winter is obvious. The influence of summer engineering is less than 2, which can be ignored temporarily.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P748;TV148

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