Fine-sediment Dynamics in the Mekong River Estuary, Vietnam
Fine-sediment Dynamics in the Mekong River Estuary, Vietnam
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DOI：
10.1006/ecss.1996.0088
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发表时间：
1996-11
影响因子：
2.8
通讯作者：
E. Wolanski;Nguyen Ngoc Huan;Le Trong Dao;N. Nhan;N. Thuy
中科院分区：
文献类型：
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作者：
E. Wolanski;Nguyen Ngoc Huan;Le Trong Dao;N. Nhan;N. Thuy
在1993年11月的高流量季节，在越南湄公河河口进行了细泥沙输运的实地研究。在淡水区，悬浮泥沙的侵蚀和沉积发生在潮汐频率下，具有较强的下游输运，平均流速为1 m s− 1，平均悬浮固体浓度约为250 mg l−1。悬浮泥沙以细粉砂为主，粘粒含量仅占15%。悬浮泥沙以单个颗粒或与有机碎屑团聚的形式被搬运。在河口处，存在一个盐楔，但在低潮时被冲出河口。在密度跃层上发生了流动逆转。涨潮时，盐楔趾部存在最大浑浊带。大部分悬浮泥沙是凝结的，有机质含量很少。大部分的悬浮泥沙输出到沿海沃茨，但一些泥沙返回河口的盐楔。低流量季节的数据是稀疏的，但表明，部分混合河口条件占上风，渗透约40公里的内陆，携带细沉积物上游的最大浑浊带的盐度。这些沉积物中的大部分在以前的高流量季节沉积在浅水沿海沃茨。在湄公河上游建造大型水电大坝可能会加剧河口的淤积模式。
Field studies of fine-sediment transport were carried out in the Mekong River estuary, Vietnam, in the high-flow season of November 1993. In the freshwater region, erosion and deposition of suspended sediment occurred at tidal frequency with a strong down-river transport at a mean velocity of 1 m s−1and mean suspended-solid concentration of about 250 mg l−1. Also, the suspended sediment was mostly fine silt, and the clay fraction accounted for only 15%. The suspended sediment was transported either as individual particles or agglomerated with organic detritus. At the mouth of the estuary, a salt wedge was present but was flushed out of the estuary at low tide. Flow reversal occurred across the pycnocline. A turbidity maximum zone was present at the toe of the salt wedge at flood tide. Most of the suspended sediment was coagulated with little organic matter. The bulk of the suspended sediment was exported to coastal waters, but some sediment returned to the estuary in the salt wedge. Data for the low-flow season are sparse but suggest that partially well mixed estuarine conditions prevail, with salinity penetrating about 40 km inland, carrying fine-sediment up-river to a turbidity maximum zone. Most of this sediment would have been deposited in shallow coastal waters in the previous high-flow seasons. The construction of large hydro-electric dams further upstream on the Mekong River may exacerbate siltation patterns in the estuary.