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Recent sediment dynamics in the region of Mekong water influence

机译：湄公河水域影响地区近期泥沙动力学

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The recent fine sediment dynamics in the region of fresh water influence (R0FI) off the Mekong River are subject of this study. Each year about 160 t of sediment discharges from the river and disperses over the shelf. The typical tropical monsoon regime induces the pronounced seasonal cycle of the discharge of water and sediment This cycle is reflected in rates of erosion and deposition on the shelf. The modern hypothesis says that this cycle of sediment results in deposition of sediment on the shelf during the high flow season and the transport back into the river mouth during the low flow season. A coupled hydrodynamic-wind-wave and sediment model, which simulates the seasonal cycle of the system, is used to prove this hypothesis. According to the simulation discharge and monsoon winds underlie significant asymmetries in the seasonal cycle. Modifications of the transport of sediment are the result of the asymmetry: As suggested in former studies the fine sediment spreads over the shelf during the high flow season. However, our model simulates wider deposition areas than suggested before. During low flow season the deposition is restricted to regions near the river mouth, elsewhere erosion due to waves, tides and wind driven circulation occurs. The asymmetry of the system results in the net-transport of most of the fine sediment predominately to the south - into the Gulf of Thailand. Additionally, we interpret our results in that way that near the river mouths the growth of the sub-aquatic delta is still ongoing. On the shelf, off the river mouths, the balanced seasonal cycle of deposition and erosion is present South of the delta, the lack of deposition of sediments and strong coastal currents results in pronounced erosion, which should be taken seriously into account for coastal management strategies.
机译：这项研究的主题是最近在湄公河以外的淡水影响（R0FI）区域的精细沉积物动力学。每年约有160吨沉积物从河中排放并散布在架子上。典型的热带季风状态引起明显的季节性水和泥沙排放周期。这种周期反映在架子上的侵蚀和沉积速率上。现代假设说，这种沉积物循环导致在高流量季节沉积物沉积在架子上，而在低流量季节导致沉积物运回河口。模拟水动力系统的季节周期的水动力-风-波浪-泥沙耦合模型被用来证明这一假设。根据模拟，在季节周期中，排风和季风是重要的不对称性。沉积物迁移的改变是不对称性的结果：如先前的研究所建议，在高流量季节，细小沉积物会在架子上扩散。但是，我们的模型比以前建议的模拟了更大的沉积区域。在低流量季节，沉积物仅限于河口附近的区域，其他地方则由于波浪，潮汐和风力驱动的环流而发生侵蚀。该系统的不对称性导致大部分细颗粒泥沙最终向南净输送到泰国湾。此外，我们以这种方式解释我们的结果，即在河口附近，亚水生三角洲的增长仍在继续。在河口附近的陆架上，三角洲南部存在平衡的沉积和侵蚀季节循环，沉积物缺乏沉积和强烈的沿海水流导致明显的侵蚀，应采取沿海管理策略予以认真考虑。

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