Modelling of sediment transport pattern in the mouth of the Rhone delta: Role of storm and flood events
Modelling of sediment transport pattern in the mouth of the Rhone delta: Role of storm and flood events
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DOI：
10.1016/j.ecss.2016.10.004
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发表时间：
2017-11
影响因子：
2.8
通讯作者：
L. Boudet;F. Sabatier;O. Radakovitch
中科院分区：
文献类型：
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作者：
L. Boudet;F. Sabatier;O. Radakovitch
罗纳河三角洲是地中海最重要的三角洲之一。近几十年来，海岸线的海滩侵蚀问题日益严重，因此需要更好地了解罗讷河口和邻近海滩的沉积物输送过程。由于在这种充满活力的环境中很难获得现场数据，因此在该区域应用了高分辨率数值模型（Delft3D）。该模型通过考虑流体动力学和形态学观察来校准。特别关注风暴和洪水事件，它们是主要的形态驱动因素。因此，运行不同波浪和水流条件的情景来估计这些事件对泥沙输运的影响。对历史水文数据的分析显示，1979年至2010年期间，70%的事件来自东南部，其中20%的事件发生后几天内就发生了洪水。因此，使用 Delft3D 对此类条件进行了具体模拟。该模型模拟了底泥沉积物迁移的趋势，该趋势与测深数据中观察到的底床形态一致。出口处的总泥沙输送仅受河流流量的影响，但河口坝的泥沙输送取决于洪水和风暴的影响以及这些事件的连续性之间的平衡。风暴峰和洪水峰之间相隔 2 或 3 天的时间足以区分波浪和河流引起的泥沙输送。波浪限制了河口坝和浅口瓣上的总运输，并引起向邻近海滩的沿岸转移。只有当洪水的能量与风暴强度相比足够大时，河流沉积物才能向海洋输出。无论如何，当洪水大于十年一遇期（7800 m3s−1）时，沉积物会从出水口输送穿过河口坝，并被引导至近海。
The delta of the Rhone River is one of the most important in the Mediterranean Sea. Beach erosion problems along its coasts have developed in recent decades, raising the need for a better understanding of the sediment transport processes at the Rhone mouth and the adjacent beaches. Because field data are very difficult to obtain in such an energetic environment, a high-resolution numerical model (Delft3D) is applied to this area. This model is calibrated by taking into account hydrodynamical and morphological observations. Special attention is given to storm and flood events, which are the major morphological drivers. Therefore, scenarios with different wave and flow conditions are run to estimate the influence of these events on the sediment transport. The analysis of historical hydrological data shows that storms from the southeast represent 70% of the events between 1979 to 2010 and that 20% of them were followed by a flood within a few days. Consequently, specific simulations for such conditions are performed using Delft3D. The model simulates trends in the bedload sediment transport that are consistent with the bedforms observed in the bathymetry data. The total sediment transport at the outlet is only influenced by the river flow, but sediment transport at the mouth-bar depends on an equilibrium between the influence of floods and storms and the succession of these events. A period of 2 or 3 days separating the storm and flood peaks is sufficient to differentiate wave and river flow-induced sediment transport. The waves constrain the total transport on the mouth-bar and shallow mouth-lobe and induce a longshore transfer towards the adjacent beaches. The riverine sediments can be exported seaward only if a flood is energetic enough compared to the storm intensity. Regardless, when a flood is greater than the decadal return period (7800 m3s−1), the sediment is transported from the outlet across the mouth-bar and is directed offshore.