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The effect of bottomset on fluviodeltaic land-building process: Numerical modelling and physical experiment
Basin Research ( IF 3.2 ) Pub Date : 2022-05-30 , DOI: 10.1111/bre.12684
Minsik Kim 1 , Wonsuck Kim 1 , Wook‐Hyun Nahm 2
Affiliation  

The loss of land in coastal regions is an emerging topic across the scientific community, as many countries struggle to minimize the consequences of an accelerating relative sea-level rise. Various methods have been attempted to mitigate land loss, and river diversion for the Mississippi River Delta, which makes use of the natural river delta-building process, has been proposed and significantly examined. Prior delta-building models predicted possible ranges of new delta-building rates and verified the feasibility of reduction in land loss on the Louisiana coast by river diversion by only considering the delta topset and foreset deposition without incorporating the muddy bottomsets because sand was regarded as the main delta-building sediment, and mud was treated as washload. Since sand flux is significantly smaller than mud flux in most coastal rivers and muddy bottomsets are common in most deltas, it is critical to understand the depositional processes of mud in deltas. Here, we present the results of a coupled numerical modelling and flume experiment that includes a moving boundary at the foreset-bottomset break in addition to the shoreline. We find that bottomset aggradation can accelerate the shoreline progradation by decreasing the foreset length (i.e., depth at the delta front). We also apply our model to a field scale based on parameters taken from the Wax Lake Delta. When 10%–50% of the mud supplied to the delta is retained in the bottomset, the subaerial delta area increases by 4.4%–25.4% compared to that in a delta with no bottomset accumulation. Therefore, considering the bottomset in land-building modelling can provide more accurate predictions for a new land-building area by river diversion.

中文翻译:

底积对河流三角洲造地过程的影响:数值模拟和物理实验

沿海地区的土地流失是整个科学界的一个新兴话题,因为许多国家都在努力将加速相对海平面上升的后果降至最低。已经尝试了各种方法来减轻土地流失,并且已经提出并认真研究了利用天然河流三角洲建造过程的密西西比河三角洲河流改道。先前的三角洲建设模型预测了新的三角洲建设率的可能范围,并验证了通过仅考虑三角洲顶部和前林沉积而不考虑泥泞底部而通过河流改道减少路易斯安那州海岸土地流失的可行性,因为沙子被认为是主要三角洲建筑沉积物,泥浆被视为洗涤负荷。由于在大多数沿海河流中,沙粒通量明显小于泥浆通量,而且大多数三角洲地区普遍存在泥质底部,因此了解三角洲泥浆的沉积过程至关重要。在这里,我们展示了耦合数值模拟和水槽实验的结果,该实验包括除了海岸线之外的前底-底断裂处的移动边界。我们发现底积加积可以通过减少前积长度(即三角洲前沿的深度)来加速海岸线的前移。我们还将我们的模型应用于基于从 Wax Lake Delta 获取的参数的现场规模。当供应给三角洲的泥浆有 10%~50% 滞留在底积时,与没有底积聚的三角洲相比,陆上三角洲面积增加了 4.4%~25.4%。所以,
更新日期:2022-05-30
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