The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam.
The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam.
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DOI：
10.1038/s41598-018-29734-7
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发表时间：
2018-07-30
影响因子：
4.6
通讯作者：
Teatini P
中科院分区：
文献类型：
--
作者：
Zoccarato C;Minderhoud PSJ;Teatini P
越南湄公河三角洲是由全新世后半期的快速海侵形成的，主要是松散的细粒（粘土）沉积物经历高压实率的沉积。自然沉降会严重影响本已脆弱的三角洲平原，因为其低海拔使三角洲暴露在全球海平面上升、洪水和盐碱化的影响之下。抽取地下水、基础设施荷载、采砂和修建水坝等人类活动加剧了自然固结的影响。在这里，我们提出了一项新颖的模型研究，可以重现过去 4000 年来湄公河三角洲的形成和演化。该模型使用自适应有限元网格，正确模拟了三角洲演化特征的增生和自然固结。考虑了大的土粒运动和孔隙水超压的延迟消散。我们发现三角洲演化后全新世沉积物的自然压实超过了绝对海平面上升的预测值。前所未有的高洪水率（高达约 20 毫米/年）威胁着下游三角洲平原的永久性洪水，并不可避免地缩短沿海防洪建筑物的设计使用寿命。三角洲平原的总沉降和沉积物输送将决定其未来的海拔和相对海平面上升的脆弱性。
The Vietnamese Mekong Delta was formed by rapid transgression during the second half of the Holocene by deposition of mainly unconsolidated, fine-grained (clayey) sediments undergoing high compaction rates. The natural subsidence can seriously impact the already vulnerable delta plain as its low elevation exposes the delta to global sea level rise, flooding, salinization. Human activities such as groundwater pumping, infrastructural loading, sand mining and dam construction have exacerbated the effects of natural consolidation. Here we present a novel modeling study that has allowed to reproduce the formation and evolution of the Mekong delta over the past 4000 years. Using an adaptive finite-element mesh, the model properly simulates accretion and natural consolidation characterizing the delta evolution. Large soil grain motion and the delayed dissipation of pore-water overpressure are accounted for. We find that natural compaction of Holocene deposits following delta evolution exceeds predicted values of absolute sea level rise. The unprecedented high rates (up to ~20 mm/yr) threaten the lower delta plain with permanent inundation and inevitably reduce the designed service life of flood defense structures along the coast. Total subsidence and sediment delivery to the delta plain will determine its future elevation and vulnerability to relative sea level rise.
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影响因子：
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作者：
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通讯作者：
Dussouillez, Philippe
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