Recent morphological changes in the Mekong and Bassac river channels, Mekong delta: The marked impact of river-bed mining and implications for delta destabilisation
Recent morphological changes in the Mekong and Bassac river channels, Mekong delta: The marked impact of river-bed mining and implications for delta destabilisation
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DOI：
10.1016/j.geomorph.2014.07.009
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发表时间：
2014-11-01
期刊：
影响因子：
3.9
通讯作者：
Dussouillez, Philippe
中科院分区：
文献类型：
--
作者：
Brunier, Guillaume;Anthony, Edward J.;Dussouillez, Philippe
越南境内的湄公河三角洲是世界第三大三角洲。三角洲人口稠密，拥有大量的工程和堤坝，以保护人口和基础设施免受风暴的影响，并保护养虾场免受盐水入侵。越南和上游国家的巨大发展压力导致中国修建了几座大坝，并导致重要的河床骨料开采，特别是在柬埔寨。这些发展的影响以多种方式影响着三角洲的动态。在这项研究中，利用1998年和2008年的河道深度数据，对从柬埔寨边境到海岸的250公里长的三角洲河段中的两个主要支流——湄公河和巴塞河的河道形态变化进行了分析。在10年的比较期内，河道显示出重要且不规则的河床变化，包括大量水池的显着切割、扩张和加深。两条河道的平均深度增加了1.3 m以上。这两个河道还显示出相关的显着河床物质损失：十年间湄公河和巴塞河分别损失了 9000 万立方米 (3) 和 1.1 亿立方米 (3)。这些在相对较短的时间内发生的重要损失，以及河床切口与水力参数之间的弱相关性表明，显着的形态变化与流量和泥沙夹带条件不平衡，因此与河流水文的变化无关。我们认为，目前在湄公河三角洲河道和三角洲上游大规模进行的骨料开采是造成这些近期形态变化的主要原因。这些变化被认为对三角洲严重的河岸侵蚀以及湄公河三角洲海岸线的侵蚀产生了积极的影响。其他贡献活动包括众多的堤坝和堤坝。由于缺乏湄公河沉积物负荷的可靠数据，现有水坝在河床流失中的作用仍不清楚。未来湄公河下游干流上的大型水电大坝开发将对集料开采产生累积效应，导致形态变化加剧，进一步影响三角洲，特别是在沉积物供应和海岸侵蚀方面。 (C) 2014 Elsevier B.V. 保留所有权利。
The Mekong delta, in Vietnam, is the world's third largest delta. Densely populated, the delta has been significantly armoured with engineering works and dykes to protect populations and infrastructure from storms, and shrimp farms from saltwater intrusion. Considerable development pressures in Vietnam and in the upstream countries have resulted in the construction of several dams in China and in important channel-bed aggregate extractions especially in Cambodia. The effects of these developments impact the delta dynamics in various ways. In this study, changes in the channel morphology of the Mekong proper and the Bassac, the two main distributaries in the 250 km-long deltaic reach from the Cambodian border to the coast, were analysed using channel depth data for 1998 and 2008. The channels display important and irregular bed changes over the 10-year comparison period, including significant incision and expansion and deepening of numerous pools. The mean depth of both channels increased by more than 1.3 m. Both channels also showed correlative significant bed material losses: respectively 90 million m(3) in the Mekong and 110 million m(3) in the Bassac over the 10-year period. These important losses over a relatively short period, and weak correlations between bed incision and hydraulic parameters suggest that the marked morphological changes are not in equilibrium with flow and sediment entrainment conditions, and are therefore not related to changes in river hydrology. We claim that aggregate extraction, currently practised on a very large scale in the Mekong delta channels and upstream of the delta, is the main cause of these recent morphological changes. These changes are deemed to contribute actively to rampant bank erosion in the delta as well as to erosion of the Mekong delta shoreline. Other contributory activities include the numerous dykes and embankments. The role of existing dams in bed losses remains unclear in the absence of reliable data on the Mekong sediment load. Future large-scale hydropower dam development on the Lower Mekong main stem will have cumulative effects with aggregate extraction, leading to increased morphological changes that will further impact the delta, especially in terms of sediment supply and coastal erosion. (C) 2014 Elsevier B.V. All rights reserved.