Sediment supply as a driver of river meandering and floodplain evolution in the Amazon Basin
Sediment supply as a driver of river meandering and floodplain evolution in the Amazon Basin
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DOI：
10.1038/ngeo2282
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发表时间：
2014-12-01
影响因子：
18.3
通讯作者：
Lazarus, Eli D.
中科院分区：
文献类型：
--
作者：
Constantine, Jose Antonio;Dunne, Thomas;Lazarus, Eli D.
尽管我们对河流曲流的物理理解取得了分析性进展，但外界施加的沉积物供应对曲流河流及其洪泛平原演变的作用知之甚少（1,2）。亚马逊河流域拥有的支流在很大程度上不受工程控制的影响，并持有一系列泥沙负荷，这使我们能够探索泥沙供应对河流演变的影响。在这里，我们从1985-2013年的陆地卫星图像中计算了亚马逊流域20个河段的平均年迁徙率。我们发现，高含沙量的河流的年迁移速率高于低含沙量的河流。沿含沙量较高的河流，曲流断流也更为频繁。研究河段之间曲流迁移和截流率的差异不能用河道坡度或河流流量的差异来解释。由于更快的曲流迁移和更高的切断率导致形成的牛轭中的沉积物储存空间增加，我们认为沉积物供应调节了曲流河流对洪泛平原环境的重塑。我们的结论是，施加的泥沙负荷影响了亚马逊低地河流的台地变化。
The role of externally imposed sediment supplies on the evolution of meandering rivers and their floodplains is poorly understood, despite analytical advances in our physical understanding of river meandering(1,2). The Amazon river basin hosts tributaries that are largely unaffected by engineering controls and hold a range of sediment loads, allowing us to explore the influence that sediment supply has on river evolution. Here we calculate average annual rates of meander migration within 20 reaches in the Amazon Basin from Landsat imagery spanning 1985-2013. We find that rivers with high sediment loads experience annual migration rates that are higher than those of rivers with lower sediment loads. Meander cutoff also occurs more frequently along rivers with higher sediment loads. Differences in meander migration and cutoff rates between the study reaches are not explained by differences in channel slope or river discharge. Because faster meander migration and higher cutoff rates lead to increased sediment-storage space in the resulting oxbows, we suggest that sediment supply modulates the reshaping of floodplain environments by meandering rivers. We conclude that imposed sediment loads influence planform changes in lowland rivers across the Amazon.