Marsh-induced backwater: the influence of non-fluvial sedimentation on a delta's channel morphology and kinematics
Marsh-induced backwater: the influence of non-fluvial sedimentation on a delta's channel morphology and kinematics
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DOI：
10.5194/esurf-11-1035-2023
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发表时间：
2023-11
影响因子：
3.4
通讯作者：
K. Sanks;J. Shaw;S. Zapp;J. Silvestre;R. Dutt;K. Straub
中科院分区：
文献类型：
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作者：
K. Sanks;J. Shaw;S. Zapp;J. Silvestre;R. Dutt;K. Straub
抽象的。研究了河流沉积与非河流沉积相互作用对河口三角洲航道形态和运动的影响。我们比较了两个三角洲：一个是非河流(沼泽)沉积的替代物(处理实验)，另一个是没有替代物的三角洲(对照)。结果表明，非河流沉积物替代物的加入改变了三角洲的航道形态和运动学。值得注意的是，在处理实验中，通道外的流量显著减少，通道更深(与源之间的径向距离的函数)和更长。我们还发现，控制通道和处理通道在接近海岸线时都变窄了，尽管与处理相比，控制通道的变窄更明显。有趣的是，处理实验中的河床经常存在于三角洲顶部陆地部分的海平面以下，产生了稳定的、非均匀的回水∼0.7m河段。然而，在控制试验中，河床一般存在于相对海平面或以上，造成类似于地形动力回水运动学和地形水流扩张的河道运动。与对照组相比，通道和远场沉积的差异产生了更长的通道充填时间刻度，这表明在治疗实验中，由通道沉积峰值引发的通道撕裂发生的频率较低。尽管存在这种差异，但整个盆地横向河道流度的时间尺度仍然相似。最终，三角洲顶部的非河流沉积在试验性河流三角洲的河道形态和运动学中起着关键作用，产生的河道更类似于全球河流三角洲的河道，不能仅仅通过增加试验性河流三角洲的内聚力来产生。
Abstract. We investigate the interaction of fluvial and non-fluvial sedimentation on the channel morphology and kinematics of an experimental river delta. We compare two deltas: one that evolved with a proxy for non-fluvial (“marsh”) sedimentation (treatment experiment) and one that evolved without the proxy (control). We show that the addition of the non-fluvial sediment proxy alters the delta's channel morphology and kinematics. Notably, the flow outside the channels is significantly reduced in the treatment experiment, and the channels are deeper (as a function of radial distance from the source) and longer. We also find that both the control and treatment channels narrow as they approach the shoreline, though the narrowing is more pronounced in the control compared to the treatment. Interestingly, the channel beds in the treatment experiment often exist below sea level in the terrestrial portion of the delta top, creating a ∼ 0.7 m reach of steady, non-uniform backwater flow. However, in the control experiment, the channel beds generally exist at or above relative sea level, creating channel movement resembling morphodynamic backwater kinematics and topographic flow expansions. Differences between channel and far-field aggradation produce a longer channel in-filling timescale for the treatment compared to the control, suggesting that the channel avulsions triggered by a peak in channel sedimentation occur less frequently in the treatment experiment. Despite this difference, the basin-wide timescale of lateral channel mobility remains similar. Ultimately, non-fluvial sedimentation on the delta top plays a key role in the channel morphology and kinematics of an experimental river delta, producing channels which are more analogous to channels in global river deltas and which cannot be produced solely by increasing cohesion in an experimental river delta.