A global delta dataset and the environmental variables that predict delta formation on marine coastlines
A global delta dataset and the environmental variables that predict delta formation on marine coastlines
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DOI：
10.5194/esurf-2019-12
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发表时间：
2019-03
影响因子：
3.4
通讯作者：
Rebecca L. Caldwell;D. Edmonds;S. Baumgardner;C. Paola;Samapriya Roy;J. Nienhuis
中科院分区：
文献类型：
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作者：
Rebecca L. Caldwell;D. Edmonds;S. Baumgardner;C. Paola;Samapriya Roy;J. Nienhuis
抽象的。河流三角洲是沿着海岸线沉积物聚集的场所，形成重要的生物栖息地，拥有特大城市，并含有大量的碳氢化合物。尽管它们很重要，但我们不知道哪些因素最显著地促进沉积物积累并主导三角洲的形成。为了调查这个问题，我们提出了一个全球数据集的5399个沿海河流和数据的8个环境变量。在这些河流中，40%（n = 2174）具有由区域海岸线突出物、分流河道网络或两者定义的地貌三角洲。在全球范围内，海岸线平均每300公里海岸线就有一个三角洲，但也有三角洲形成的热点，例如在东南亚，每100公里海岸线就有一个三角洲。我们的分析表明，河流形成三角洲的可能性随着水流量、泥沙流量和流域面积的增加而增加。另一方面，三角洲可能性随波高和潮差的增加而减小。三角洲似然与接收盆地斜率有非单调关系：它随着斜率的增大而减小，但对于斜率> 0.006的三角洲似然则增大。这反映了主动边缘和被动边缘对三角洲形成的不同控制。沉积物浓度和最近的海平面变化不影响三角洲的可能性。Logistic回归分析表明，流量、输沙量、波高和潮差是影响三角洲形成的重要因素。逻辑回归正确预测三角洲形成的时间为74%。我们的全球分析表明，三角洲的形成和形态代表了建设性和破坏性力量之间的平衡，这个框架可能有助于预测三角洲迅速转变形态的临界点。
Abstract. River deltas are sites of sediment accumulation along the coastline that form critical biological habitats, host megacities, and contain significant quantities of hydrocarbons. Despite their importance, we do not know which factors most significantly promote sediment accumulation and dominate delta formation. To investigate this issue, we present a global dataset of 5399 coastal rivers and data on eight environmental variables. Of these rivers, 40 % (n=2174) have geomorphic deltas defined either by a protrusion from the regional shoreline, a distributary channel network, or both. Globally, coastlines average one delta for every ∼300 km of shoreline, but there are hotspots of delta formation, for example in Southeast Asia where there is one delta per 100 km of shoreline. Our analysis shows that the likelihood of a river to form a delta increases with increasing water discharge, sediment discharge, and drainage basin area. On the other hand, delta likelihood decreases with increasing wave height and tidal range. Delta likelihood has a non-monotonic relationship with receiving-basin slope: it decreases with steeper slopes, but for slopes >0.006 delta likelihood increases. This reflects different controls on delta formation on active versus passive margins. Sediment concentration and recent sea level change do not affect delta likelihood. A logistic regression shows that water discharge, sediment discharge, wave height, and tidal range are most important for delta formation. The logistic regression correctly predicts delta formation 74 % of the time. Our global analysis illustrates that delta formation and morphology represent a balance between constructive and destructive forces, and this framework may help predict tipping points at which deltas rapidly shift morphologies.