The recent morphological evolution in the upper mouth sandbar of the North Branch and the impacts on its upper reach in the Changjiang Estuary
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摘要:
针对近年来长江口南北支分汊口近北支一侧水域发育的新生沙体，采用该区域2010—2020年的实测地形资料，分析了江心沙近10年的演变特征，并采用水动力数学模型结合经验公式分析沙体进一步淤涨或对其采取疏浚措施后对周边水动力和地形冲淤变化的影响。结果表明，近10年间，江心沙面积增加了近5倍，滩顶高程从＜1 m逐步发育至＞3 m，近期沙体已不再“长大”，但仍在逐渐“长高”，并有从低滩向高滩逐渐转化的趋势；若江心沙进一步淤涨，北支分流比将进一步减小，海门港至日新河段主槽流速减小并产生淤积，不利于北支的入流，同时跃进港近岸流速增加，深槽将进一步冲刷逼岸，不利于沿线海塘安全；若对江心沙采取疏浚措施，北支分流比将增加，有利于缓解其上段“S”型河势，海门港至日新河段流速增加，深槽冲刷，有利于北支入流以及分流比的增加，同时，跃进港近岸流速减小，出现淤积，有利于该岸段海塘安全。
Abstract:Due to the new-born sandbank found in the upper river mouth of the North Branch in Changjiang Estuary, the bathymetry data during 2010—2020 was used to investigate its evolution and trends in the last decade. Additionally, a hydrodynamic numerical model combined with an empirical formula was used to further explore the effects on the hydrodynamics and bathymetry after the sandbank was further silted up or dredged. Results indicate that, in the past 10 years, the area of the sandbank has increased by nearly 5 times, and its elevation has gradually developed from less than 1 m to more than 3 m. In the recent years, the sandbank has stopped growing larger, but still gradually grown taller, and exhibited a trend of transformation from the lower tidal flat to the higher one. If the sandbank further silts up, the water diversion ratio of the North Branch will be further reduced. At the same time, the velocity of the main channel from Haimen Port to Rixin River will decrease, which may lead to siltation and the restrict of inflow in the North Branch. The nearshore water speed around Yuejin Port will increase, and may enhance the erosion there, which may threaten the safety of sea dikes. If the sandbank is dredged off, the water diversion ratio of the North Branch will increase, which takes advantageous to alleviate the S-shaped river regime in the upper North Branch. At the same time, the velocity from Haimen Port to Rixin River will increase, the main channel will be deepened, which will promote the water diversion ratio in the North Branch, decrease the nearshore water speed around Yuejin Port, induce the local siltation, and finally benefit the safety of sea dikes.
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表 1 2010—2020年北支上口江心沙不同等高线面积变化情况
Table 1. The 0, 1, 2, and 3 m isobaths zones of the sandbank in the upper reach of the North Branch from 2010 to 2020
等高线/m 2010年 2011年 2012年 2013年 2014年 2015年 2016年 2017年 2018年 2019年 2020年 面积/km2 0 1.78 1.55 2.34 6.34 6.25 7.92 7.8 8.32 8.41 8.83 8.65 1 0 0 0 2.29 3.91 4.97 5.84 5.75 5.95 6.46 6.24 2 0 0 0 0 0.57 0.46 2.44 1.43 2.15 2.47 2.51 3 0 0 0 0 0 0 0 0 0 0.03 0.07 
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表 2 2010—2020年北支上口江心沙0 m以上不同高程面积占比
Table 2. Proportion of different elevation areas above 0 m of the sandbank in the upper reach of the North Branch from 2010 to 2020
高程/m 2010年 2011年 2012年 2013年 2014年 2015年 2016年 2017年 2018年 2019年 2020年 面积占比/% ＞3 0 0 0 0 0 0 0 0 0 0.3 0.8 2～3 0 0 0 0 9.1 5.8 31.3 17.2 25.6 27.6 28.2 1～2 0 0 0 36.1 53.4 56.9 43.6 51.9 45.2 45.2 43.1 0～1 100 100 100 63.9 37.4 37.2 25.1 30.9 29.3 26.8 27.9 ＞0 100 100 100 100 100 100 100 100 100 100 100
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表 3 江心沙疏浚2 m前后北支中上段枯季深槽和浅滩过流比例
Table 3. The discharge ratios of deep channel and tidal flat during flood and ebb tides under current topography and case of sandbank dredging 2 m in the upper and middle reaches of the North Branch in dry season
断面位置 深槽/浅滩 涨潮 落潮 现状 疏浚2 m 变化 现状 疏浚2 m 变化 崇头边滩（断面1） 深槽 76.2% 79.2% 3.0% 87.8% 88.3% 0.5% 浅滩 23.8% 20.8% −3.0% 12.2% 11.7% −0.5% 跃进港（断面2） 深槽 47.0% 45.3% −1.7% 52.5% 51.1% −1.4% 浅滩 53.0% 54.7% 1.7% 47.5% 48.9% 1.4% 新跃沙（断面3） 深槽 86.5% 86.0% −0.5% 82.5% 82.3% −0.2% 浅滩 13.5% 14.0% 0.5% 17.5% 17.7% 0.2% 庙港北闸（断面4） 深槽 60.4% 60.7% 0.3% 67.6% 67.6% 0.0% 浅滩 39.6% 39.3% −0.3% 32.4% 32.4% 0.0%
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表 4 江心沙疏浚2 m前后北支中上段洪季深槽和浅滩过流比例
Table 4. The discharge ratios of deep channel and tidal flat during flood and ebb tides under current topography and case of sandbank dredging 2 m in the upper and middle reaches of the North Branch in wet season
断面位置 深槽/浅滩 涨潮 落潮 现状 疏浚2 m 变化 现状 疏浚2 m 变化 崇头边滩（断面1） 深槽 48.40% 55.3% 6.9% 84.4% 83.9% −0.5% 浅滩 51.60% 44.7% −6.9% 15.6% 16.1% 0.5% 跃进港（断面2） 深槽 47.10% 41.7% −5.4% 52.9% 52.0% −0.9% 浅滩 52.90% 58.3% 5.4% 47.1% 48.0% 0.9% 新跃沙（断面3） 深槽 87.00% 87.0% 0.0% 79.8% 80.2% 0.4% 浅滩 13.00% 13.0% 0.0% 20.2% 19.8% −0.4% 庙港北闸（断面4） 深槽 59.90% 60.0% 0.1% 66.4% 66.4% 0.0% 浅滩 40.10% 40.0% −0.1% 33.6% 33.6% 0.0%
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[1] 陈正兵,陈前海,谢作涛. 长江口北支近期水沙特性及河道演变特征[J]. 人民长江,2016,47(23):5-9.
[2] DAI Z J,FAGHERAZZI S,MEI X F,et al. Linking the infilling of the North Branch in the Changjiang (Yangtze) Estuary to an-thropogenic activities from 1958 to 2013[J]. Marine Geology,2016,379(11):1-12.
[3] GUO L C,XIE W M,XU F,et al. A historical review of sediment export–import shift in the North Branch of Changjiang Estuary[J]. Earth Surface Processes and Landforms,2022,47(1):5-16. doi: 10.1002/esp.5084
[4] 李伯昌. 1984年以来长江口北支演变分析[J]. 水利水运工程学报,2006(3):9-17. doi: 10.3969/j.issn.1009-640X.2006.03.002
[5] 代炳珂,路川藤,韩玉芳,等. 1958年以来长江口南、北支河段河床演变及影响因素研究[J]. 水利水运工程学报,2021(2):27-37. doi: 10.12170/20210105003
[6] GU J,QIN X,CHEN W,et al. Influence of the diversion angle on flow characteristics of the North Branch of the Changjiang River Estuary[J]. Advanced Materials Research,2013,610:2697-2700.
[7] 周良平,周东泉,杜德军,等. 长江北支进口段演变特征及治理[J]. 水运工程,2022(12):128-133. doi: 10.3969/j.issn.1002-4972.2022.12.020
[8] 季永兴,李路,袁琳,等. 长江口北支上段岸滩侵蚀及保护实施效果分析[J]. 海洋地质前沿,2024,40(2):11-19.
[9] 李路,刘新成,宋永港,等. 强潮河口海岸冲蚀对海堤安全的影响研究[J]. 华东师范大学学报(自然科学版),2019(4):202-211.
[10] 杨芳丽,韩婷,闫军,等. 长江口北支河段演变分析及航道治理思路初探[J]. 水运工程,2014(12):79-82. doi: 10.3969/j.issn.1002-4972.2014.12.015
[11] 孙永涛,张金池. 长江口北支湿地分类及生境特征[J]. 湿地科学与管理,2010,6(2):49-52. doi: 10.3969/j.issn.1673-3290.2010.02.11
[12] WU H,ZHU J R,CHEN B R,et al. Quantitative relationship of runoff and tide to saltwater spilling over from the North Branch in the Changjiang Estuary:a numerical study[J]. Estuarine,Coastal and Shelf Science,2006,69(1/2):125-132. doi: 10.1016/j.ecss.2006.04.009
[13] GU J H,ZHU J R,LYU H H. Observation and analysis of water and salt transports in the North Branch of the Changjiang Estuary[J]. Journal of Coastal Research,2021,37(3):518-527.
[14] YANG Y D,ZHU J R,CHEN Z B,et al. The impact of sluice construction in the north branch of the Changjiang Estuary on saltwater intrusion and freshwater resources[J]. Journal of Marine Science and Engineering,2023,11:2107. doi: 10.3390/jmse11112107
[15] 李志鹏,朱建荣. 2007—2016年北支河势变化对长江口盐水入侵影响数值研究[J]. 华东师范大学学报(自然科学版),2022(3):109-124.
[16] DING J,SHAO Y C,WU D A. Effect of tidal currents on the transport of saline water from the North Branch in the Changjiang River Estuary[J]. Journal of Oceanology and Limnology,2018,36(6):2085-2097. doi: 10.1007/s00343-018-7357-5
[17] 卜东平. 咸潮入侵对长江上海段过境水资源利用的影响探讨[J]. 上海国土资源,2023,44(3):61-67. doi: 10.3969/j.issn.2095-1329.2023.03.010
[18] 王义刚,林祥,吴中. 河口边滩围垦后淤积计算方法研究[J]. 海洋工程,2000(3):67-70. doi: 10.3969/j.issn.1005-9865.2000.03.013
[19] 刘家驹,喻国华. 淤泥质海岸保滩促淤计算及预报[J]. 海洋工程,1990(1):51-59.
[20] 徐群,张继昌,王俊,等. 瓯江河口浅滩促淤估算分析[J]. 海洋工程,2005(3):39-44. doi: 10.3969/j.issn.1005-9865.2005.03.006
[21] 黄胜,卢启苗. 河口动力学[M]. 北京:水利电力出版社,1995.
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