Direct, continuous measurements of ultra-high sediment fluxes in a sandy gravel-bed ephemeral river
Direct, continuous measurements of ultra-high sediment fluxes in a sandy gravel-bed ephemeral river
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DOI：
10.1016/j.geomorph.2021.107682
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发表时间：
2021-03
期刊：
影响因子：
3.9
通讯作者：
K. Stark;D. Cadol;D. Varyu;J. Laronne
中科院分区：
文献类型：
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作者：
K. Stark;D. Cadol;D. Varyu;J. Laronne
沙质砾石河床河流的野外测量资料很少。实验室实验表明，含沙量大的泥沙混合物在向下游输送推移质时特别有效。为了评估这些环境中的输运过程，我们建造了一个泥沙监测研究设施，能够连续监测泥沙通量。阿罗约德洛斯皮诺斯河位于美国新墨西哥州，是一条砾石床临时河道，含有大量(30%)沙子。该野外站使用里德型槽式采样器直接测量推移质通量，并高质量地测量悬浮泥沙、水深、水流速度和颗粒大小。瞬时推移质流量高于全球平均值，高达12 kg S−1M−1。悬浮泥沙也很高，峰值为100,000 mg L−1，并存在顺时针滞后现象。PINOS无量纲推移质通量与其他短暂河道相似，但高含沙量允许在相对较浅的水深时具有相同的移动性，并在过程线衰退期间提供高推移质输移率。泥沙通量的响应具有滞后性，在水位上升过程中，等剪应力时，泥沙通量较高。这可能是由于没有充分利用深度-坡度乘积来计算河床剪切力，或在上升支段时摩擦坡度较陡，或两者兼而有之。这些首次监测到的泥沙输送山洪事件揭示了一条在短时间内非常活跃的河道。平均而言，阿罗约德洛斯皮诺斯河每年在3-5场活动中流动12-24 h。然而，在这些短暂的时间里，该航道在输送推移质和悬浮泥沙方面非常高效，其输沙率比常年的同行高出几个数量级。
A dearth of field measurements exists from sandy gravel-bed rivers. Laboratory experiments suggest that sediment mixtures with a large sand component are particularly efficient at transporting bedload downstream. To evaluate transport processes in these environments, we constructed a sediment monitoring research facility with the ability to continuously monitor sediment fluxes. The Arroyo de los Pinos is a gravel-bed ephemeral channel with a large (>30%) sand component in New Mexico, USA. This field station incorporates direct measurements of bedload flux using Reid-type slot samplers with high quality measurements of suspended sediment, water depth, water velocity, and grain size. Measurements are collected at a stable cross section constructed for long-term, consistent monitoring.Instantaneous bedload flux is high compared to global averages, as high as 12 kg s−1m−1. Suspended sediment is also high, peaking at 100,000 mg L−1, with evidence of clockwise hysteresis. The Pinos nondimensional bedload flux rates are similar to those in other ephemeral channels, but the high sand content allows equal mobility at relatively shallow water depths and high rates of bedload transport during hydrograph recession. Bedload flux responded hysteretically, higher at equal shear stresses during stage rise. This is likely caused by an inadequate use of the depth-slope product for calculation of bed shear, steeper friction slopes during the rising limb, or both.These first monitored sediment transporting flash flood events reveal a channel that is very active during short periods of time. On average, the Arroyo de los Pinos flows 12–24 h during 3–5 events every year. However, in these brief periods, the channel is hyper-efficient at transporting bedload and suspended sediment at rates that are orders of magnitude higher than perennial counterparts.