Depositional dynamics in a river diversion receiving basin: The case of the West Bay Mississippi River Diversion
Depositional dynamics in a river diversion receiving basin: The case of the West Bay Mississippi River Diversion
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DOI：
10.1016/j.ecss.2012.04.005
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发表时间：
2012-06-20
影响因子：
2.8
通讯作者：
Weathers, H. Dallon
中科院分区：
文献类型：
--
作者：
Kolker, Alexander S.;Miner, Michael D.;Weathers, H. Dallon
河流三角洲是一类分布于全球的沉积环境，生产力高、生态多样，是人口和商业中心。许多三角洲也处于环境退化的状态，密西西比河三角洲（MRD）就是一个特别典型的例子。恢复 MRD 的计划要求部分改道密西西比河，这应该会重新启动自然三角洲土地建设过程。虽然河流改道的基本物理基础相对简单，但对于改道是否能够并且确实向沿海地区输送足够的沉积物以在取决于恢复的时间尺度上建造地下土地，存在相当大的争议。这一争议是通过对西湾密西西比河改道的裂缝展开动力学的研究得到解决的，西湾密西西比河改道是专为海岸恢复而建造的 MRD 中最大的改道。我们发现大多数沉积物分布在13.5 km的区域内，最大沉积发生在该区域的向海端。这些结果表明项目边界下游有大量沉积物沉积，这与简单沉积模型相反，简单沉积模型预测最大沉积物沉积应发生在最靠近河岸的地方。尽管如此，大多数沉积物似乎保留在近岸区域，这表明沉积物保留效率处于一些沉积物预算建议的 30-70% 范围的较高端。 (C) 2012 Elsevier Ltd. 保留所有权利。
River deltas are a globally distributed class of sedimentary environment that are highly productive, ecologically diverse and serve as centers for population and commerce. Many deltas are also in a state of environmental degradation, and the Mississippi River Delta (MRD) stands out as a particularly iconic example. Plans to restore the MRD call for partially diverting the Mississippi River, which should reinitiate natural deltaic land-building processes. While the basic physical underpinnings of river diversions are relatively straightforward, there exists a considerable controversy over whether diversions can and do deliver enough sediment to the coastal zone to build sub-aerial land on restoration-dependent time scales. This controversy was addressed through a study of crevasse-splay dynamics at the West Bay Mississippi River Diversion, the largest diversion in the MRD that was specifically constructed for coastal restoration. We found that most sediments were distributed over a 13.5 km area, with the maximum deposition occurring at the seaward end of this field. These results indicate substantial sediment deposition downstream of project boundaries and run counter to simple sedimentary models, which predict that maximum sediment deposition should occur closest to the riverbank. Despite this, most sediments appear to be retained in the nearshore zone, suggesting that the sediment retention efficiency was at the higher end of the 30-70% range suggested by some sediment budgets. (C) 2012 Elsevier Ltd. All rights reserved.