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Evaluation of along-channel sediment flux gradients in an anthropocene estuary with an estuarine dam
Marine Geology ( IF 2.6 ) Pub Date : 2020-08-15 , DOI: 10.1016/j.margeo.2020.106318
Steven Miguel Figueroa , Guan-hong Lee , Jongwi Chang , Nathalie W. Schieder , Kyeongman Kim , Seok-Yun Kim

While estuarine dams can develop freshwater resources and block the salt intrusion, they can result in increased sediment deposition in the estuary. The mechanism of increased sediment deposition in an estuary with an estuary dam is not well understood. To fill this knowledge gap, 7 ADCP measurements of flow and suspended sediment concentration (SSC) were collected along-channel in an estuary with an estuarine dam over a neap-spring cycle. Flow and SSC were used to calculate the sediment flux and sediment flux gradients, which in turn were decomposed into mean-flow fluxes (which occur on timescales longer than a tidal cycle) and correlation fluxes (which occur on the tidal timescale). Then the fluxes were compared with the external forcing to determine the relative importance of tides, dam discharge, and waves in driving the fluxes. The results indicated that the cumulative sediment fluxes at all stations were directed landward. The along-channel sediment flux gradient was negative, which indicated deposition along the channel. The landward mean-flow fluxes were dominant in the deep portion of the channel near the estuary mouth, whereas landward correlation fluxes were dominant in the shallow portion of the channel near the estuarine dam. The tides were the dominant forcing driving the sediment fluxes throughout the estuary. Waves and dam discharge were locally important forcing however. In particular, the dam discharge resulted in seaward mean-flow fluxes for 7 km seaward of the estuarine dam. This distance corresponded approximately to a tidal excursion seaward from the dam. It was the distance a freshwater mass discharged during an ebb tide could propagate before the currents returned landward during the following flood tide. Overall, the along-channel sediment flux gradient in an estuary with an estuarine dam was different from a similar estuary without an estuarine dam because the mean-flow fluxes in the inner estuary are forced by episodic dam discharge which was limited in seaward extent by the tidal excursion. This imposed a limitation for the seaward mean-flow fluxes which counteract the landward mean-flow and correlation fluxes due to the tides. With restricted seaward flushing, the tides could dominate, which could in turn result in increased depositional rates for an estuary with an estuarine dam.



中文翻译:

河口大坝人类世河口沿河道泥沙通量梯度的估算

尽管河口大坝可以开发淡水资源并阻止盐分入侵,但它们可能导致河口沉积物增加。人们对河口大坝的河口沉积物增加沉积的机理尚未完全了解。为了填补这一知识空白,在河口水坝的泉水-春季循环中,沿河道沿河道收集了7条ADCP流量和悬浮泥沙浓度(SSC)测量值。流量和SSC用于计算泥沙通量和泥沙通量梯度,然后将其分解为平均流量(发生在比潮汐周期长的时间尺度上)和相关通量(出现在潮汐时间尺度上)。然后,将通量与外部强迫进行比较,以确定潮汐,大坝排放和波浪在驱动通量方面的相对重要性。结果表明,所有站的累积泥沙通量均向着陆方向。沿河道的沉积物通量梯度为负,表明沿河道的沉积。在河口附近,河道的深部占主导地位,而在河口大坝附近,河道的浅部占主导地位。潮汐是驱使整个河口泥沙通量的主要强迫。然而,波浪和水坝泄洪是当地的重要因素。特别是,大坝泄洪导致河口大坝向海7 km的向海平均流通量。该距离大致对应于从大坝向海的潮汐偏移。这是在退潮期间淡水流在下一个洪水潮汐流返回陆地之前可以传播的距离。总体而言,有河口大坝的河口沿河沉积物通量梯度与没有河口大坝的类似河口不同,这是因为内河口的平均水流是由偶发性大坝排放推动的,而该过程在一定程度上限制了向海的排放。潮汐游览。这就限制了向海平均流量通量,该通量抵消了由于潮汐引起的向岸平均流量和相关通量。在限制向海冲洗的情况下,潮汐将占主导地位,这反过来可能导致河口大坝的河口沉积速率增加。有河口大坝的河口沿河道的泥沙通量梯度与没有河口大坝的类似河口不同,这是因为内河口的平均水流是由间歇性大坝排放推动的,潮汐偏移限制了向海延伸的程度。 。这就限制了向海平均流量通量,该通量抵消了由于潮汐引起的向岸平均流量和相关通量。在限制向海冲洗的情况下,潮汐将占主导地位,这反过来可能导致河口大坝的河口沉积速率增加。有河口大坝的河口沿河道的泥沙通量梯度与没有河口大坝的类似河口不同,这是因为内河口的平均水流是由间歇性大坝排放推动的,潮汐偏移限制了向海延伸的程度。 。这就限制了向海平均流量通量,该通量抵消了由于潮汐引起的向岸平均流量和相关通量。在限制向海冲洗的情况下,潮汐将占主导地位,这反过来可能导致河口大坝的河口沉积速率增加。这就限制了向海平均流量通量,该通量抵消了由于潮汐引起的向岸平均流量和相关通量。在限制向海冲洗的情况下,潮汐将占主导地位,这反过来可能导致河口大坝的河口沉积速率增加。这就限制了向海平均流量通量,该通量抵消了由于潮汐而向陆地的平均流量和相关通量。在限制向海冲洗的情况下,潮汐将占主导地位,这反过来可能导致河口大坝的河口沉积速率增加。

更新日期:2020-08-15
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