Exploring Wave and Sea‐Level Rise Effects on Delta Morphodynamics With a Coupled River‐Ocean Model
Exploring Wave and Sea‐Level Rise Effects on Delta Morphodynamics With a Coupled River‐Ocean Model
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DOI：
10.1029/2018jf004757
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发表时间：
2018-11
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影响因子：
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通讯作者：
Katherine M. Ratliff;Eric H. W. Hutton;A. Murray
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文献类型：
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作者：
Katherine M. Ratliff;Eric H. W. Hutton;A. Murray
三角洲通常人口稠密，由于海平面上升速度加快和沉积物供应减少，三角洲变得更容易受到洪水的影响。这些景观是通过三角洲叶的连续叠加而形成的，因为河流的突然变化会偶尔改变河口的位置。这些通道撕脱的动力学决定了三角叶的位置和大小。我们使用一个新开发的河流和海岸过程的耦合模型来探索不断变化的波浪气候（不同的波高和离岸接近角）和一系列海平面上升率如何影响撕脱过程和大规模三角洲形态。虽然河流沉积物通量和波浪影响的相对影响已经研究了很长时间，最近量化，我们发现，波气候扩散率的符号和幅度都发挥重要作用，不仅确定三角洲形态，但也撕脱动力学。我们还发现，令人惊讶的是，海平面上升率的增加并不总是加速撕脱。如果河道相对于海平面上升速度足够快，那么撕脱频率将不会受到海平面上升速度的显著影响。这一发现突出了波浪和河流主导的三角洲之间的重要差异，以及实验室中创建的原型三角洲和实验三角洲之间的重要差异。波浪气候、海平面上升率和触发撕脱所需的临界超高在确定三角洲系统中自生变化的程度方面都起着重要作用，这对撕脱动力学和三角洲地层学的解释都有影响。
Deltas, which are often densely populated, have become more vulnerable to flooding due to increasing rates of sea‐level rise and decreasing sediment supply. These landscapes grow through the successive stacking of delta lobes, as abrupt changes in the river's course episodically alter the river mouth's location. The dynamics of these channel avulsions determine the location and size of delta lobes. We use a newly developed coupled model of river and coastal processes to explore how changing wave climates (varying wave heights and offshore approach angles) and a range of sea‐level rise rates affect avulsion processes and large‐scale delta morphology. Although the relative impacts of the fluvial sediment flux and wave influence have long been studied and more recently quantified, we find that the sign and magnitude of wave climate diffusivity both play important roles in determining not only delta morphology but also avulsion dynamics. We also find, surprisingly, that increasing sea‐level rise rates do not always accelerate avulsions. If the river channel is prograding rapidly enough, relative to the rate of sea‐level rise, then avulsion frequency will not be significantly affected by the rate of sea‐level rise. This finding highlights important differences between wave and river‐dominated deltas, as well as between prototypical deltas and experimental deltas created in the lab. The wave climate, sea‐level rise rate, and critical superelevation required to trigger an avulsion all play important roles in determining the degree of autogenic variability operating in delta systems, which has implications for both avulsion dynamics and interpretation of delta stratigraphy.