The self-regulation process and its mechanism of channels’ bed changes in the Changjiang (Yangtze) Estuary in China
-
摘要: 基于长江河口1997年以来数字地形图和近期水文泥沙实测资料, 分析研究了近期长江河口大量人工整治工程和流域水库工程建造的影响下的河口河道自动调整过程。结果表明:1997年以来的16年中河口段中上游河道微冲刷、拦门沙滩顶仍保持淤积外移、口门外侧近海域冲刷的态势略有增强, 而其影响原因与历史时期的自然因素影响为主略有差异, 近期人类高强度活动的影响贡献率增大。首先, 南支至南港和北港中上游河段河床发生普遍冲刷, 河床沙活动较活跃, 床面微地貌沙波发育更明显, 而口门外侧海域地形略有冲刷蚀退, 这些变化与流域来沙锐减有直接关系;北支、北港口门、南槽和北槽河道拦门沙河段呈淤积, 尤其北槽主航道的拦门沙河段6m水深浚深为12.5m后回淤量很大, 这些与拦门沙河道动力结构环境、河口和海域再悬浮泥沙补给有关;局部河段出现强冲和强淤现象, 与近期河口工程建造有关。所以, 长江河口近期正处在对自然因素变化和人类活动增强的自我缓慢地自动调整和适应过程之中。故然, 开展此类研究有其重要的现实意义。Abstract: Recent bathymetric changes in the Changjiang Estuary under the influence of artificial regulation engineerings and basin reservoirs have been analyzed based on the maritime charts since 1997 and recent fieldworks. The results indicate a slight erosion of the channels in the upper and middle estuary, continuing deposition and seaward move of the mouth bar crest and intensifying erosion at the nearshore seabed. It is noteworthy that the morphological evolution caused by intensive human activities dominates over the changes from nature process. First, the riverbes are eroded overall in the South Branch (SB), the South Channel (SC) and the upper and middle reaches of the North Channel (NC). The nearshore seabed outside the river mouth is being eroded slightly, which is attributed to the declining sediment supply from the Changjiang Basin due to the construction of the Three Gorges Dam upstream. The sediment above the seabed is very active and coarsened, meanwhile, sand waves are becoming more distinct. Second, a deposition occurs in the North Brach (NB), the mouth of the NC, the mouth bars of the North Passage (NP) and the South Passage (SP) and especially the main channel of the NP, where it shows a massive siltation after the deep waterway project. The reasons for the recent changes are not only the dynamic structure in estuarine mouth bars, but also the supply of sediment resuspension in a local and offshore area. Meanwhile, the severe erosion and siltation in some reaches is related to the construction of estuarine engineerings. It is indicated that the Changjiang Estuary is gradually self-adjusted and adapting to the varying natural factors and intensive human activities. The study on the mechanism of self-regulation of the recent bathymetric changes in the Changjiang Estuary has important and practical significance.
-
Key words:
- Changjiang Estuary /
- bathymetric changes /
- self-regulation /
- human activities /
- tidal current /
- sediment transport
-
Changjiang Water Resources Commission. Changjiang Sediment Bulletin. Beijing: China Water Power Press, 2005 Chen Jiyu, Yun Caixing, Xu Haigen, et al. 1979. The developmental model of the Chang Jiang River Estuary during last 2000 years. Haiyang Xuebao (in Chinese), 1(1): 103-111 Dai Zhijun, Du Zinzhou, Chu Ao, et al. 2011. Sediment characteristics in the North Branch of the Yangtze Estuary based on radioisotope tracers. Environmental Earth Sciences, 62(8): 1629-1634, doi: 10.1007/S12665-010-0647-7 Dai Zhijun, Liu J T, Fu Gui, et al. 2013. A thirteen-year record of bathymetric changes in the North Passage, Changjiang (Yangtze) estuary. Geomophology, 187: 101-107 Feng Lingxuan, Li Jiufa, Dai Zhijun, et al. 2009. Analysis of river channel stability and the characteristics of suspended sediment and water in the North Branch of the Changjiang River Estuary in recent years. Journal of Marine Sciences (in Chinese), 27(3): 40-47 Feng Lingxuan, Li Jiufa, Liu Xincheng, et al. 2012. Morphological evolution of diffluence pass of South Passage and North Passage in Yangtze Estuary and its response to diversion works. Journal of Sediment Research (in Chinese), (6): 39-45 He Yufang, Cheng Heqin, Chen Jiyu. 2011. Morphological evolution of mouth bars of the Yangtze Estuarine waterways in the last 100 years. Acta Geographica Sinica (in Chinese), 66(3): 305-312 Jiang Chenjuan, de Swart H E, Li Jiufa, et al. 2013. Mechanisms of along-channel sediment transport in the North Passage of the Yangtze estuary and their response to large-scale interventions. Ocean Dynamics, 63(2-3): 283-305 Jiang Chenjuan, Li Jiufa, de Swart H E. 2012. Effects of navigational works on morphological changes in the bar area of the Yangtze Estuary. Geomorphology, 139-140: 205-219 Jiang Chenjuan, Li Jiufa, Wu Hualin, et al. 2013. Effects of the deep waterway project on the characteristics of hydrodynamics and sediment dynamics in the North Passage of the Changjiang Estuary. Haiyang Xuebao (in Chinese), 35(4): 129-141 Lane A. 2004. Bathymetric evolution of the Mersey Estuary, UK, 1906-1997: causes and effects. Estuarine, Coastal and Shelf Science, 59(2): 249-263 Li Maotian, Cheng Heqin, Zhou Fengnian, et al. 2011. The effect of sand digging to bedfrom stability of the Nangang Channel in the Changjiang River mouth. Hydrographic Surveying and Charting (in Chinese), 31(1): 50-53 Li Jiufa, Li Zhanhai, Yao Hongyi, et al. 2013. Study on the Sediment Properties and Resuspension in the South Branch in the Changjiang Estuary (in Chinese). Beijing: China Ocean Press, 1196-1200 Li Jiufa, Zhang Chen. 1998. Sediment resuspension and implications for turbidity maximum in the Changjiang Estuary. Marine Geology, 148(3-4): 117-124 Liu jie, Le Jiahai, Hu Zhifeng, et al. 2003. The influence on the north passage bar after executing the first phase regulation project of the Yangtze Estuary. The Ocean Engineering (in Chinese), 21(2): 58-64 Pan Lingzhi, Ding Pingxing, Ge Jianzhong, et al. 2011. Analysis of influence of deep waterway project on morphological change in North passage of Changjiang estuary. Journal of Sediment Research (in Chinese), (5): 51-59 Qian Ning, Zhang Ren, Li Jiufa, et al. 1981. A preliminary study on the mechanism of selfregulation of sediment transport capacity in the lower Huang He (the Yellow River). Acta Geographica Sinica (in Chinese), 36(2): 143-156 Roelvink J A. 2006. Coastal morphodynamic evolution techniques. Coastal Engineering, 53(2-3): 277-287 Shen Huanting, Pan Dingan. 2011. Turbidity Maximum in the Changjiang Estuary (in Chinese). Beijing: China Ocean Press Song Zekun, Cheng Heqin, Hu Hao, et al. 2012. Numerical simulation analysis of influence of reclamation of north branch in the Yangtze River estuary on hydrodynamic characteristics. Yangtze River (in Chinese), 43(15): 59-63 Syvitski J P M, Vörösmarty C J, Kettner A J, et al. 2005. Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science, 308(5720): 376-380 Tambroni N, Pittaluga M B, Seminara G. 2005. Laboratory observations of the morphodynamic evolution of tidal channels and tidal inlets. Journal of Geophysical Research, 110(F4): doi: 10.1029/2004JF000243 Walling D E. 2006. Human impact on land-ocean sediment transfer by the world's rivers. Geomorphology, 79(3-4): 192-216 Wang Yonghong, Dong Ping, Oguchic T, et al. 2013. Long-term (1842-2006) morphological change and equilibrium state of the Changjiang (Yangtze) Estuary, China. Continental Shelf Research, 56: 71-81 Yang Shilun, Shi Zhong, Zhao Huayun, et al. 2004. Effects of human activities on the Yangtze River suspended sediment flux into the estuary in the last century. Hydrology and Earth System Sciences, 8(6): 1210-1216 Zhou Xiaoyan, Zheng Jinhai, Doong D J, et al. 2013. Sea level rise along the East Asia and Chinese coasts and its role on the morphodynamic response of the Yangtze River Estuary. Ocean Engineering, 71: 40-50, doi: 10.1016/j.oceaneng.2013.03.014
点击查看大图
计量
- 文章访问数: 1351
- HTML全文浏览量: 66
- PDF下载量: 704
- 被引次数: 0