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首页> 外文期刊>Estuarine Coastal and Shelf Science >The sediment trapping efficiency of the macro-tidal Daly Estuary, tropical Australia
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The sediment trapping efficiency of the macro-tidal Daly Estuary, tropical Australia

机译：澳大利亚热带大潮河戴利河口的沉积物捕获效率

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摘要

Field studies were carried out on the water and sediment dynamics in the tropical, macro-tidal, Daly Estuary. The estuary is shallow, very-turbid, about 100 km long, and the entrance is funnel-shape. In the wet, high flow season, normal tidal ranges can be suppressed in the estuary, depending on inflow rates, and freshwater becomes dominant up to the mouth. At that time a fraction of the fine sediment load is exported offshore as a bottom-tagging nepheloid layer after the sediment falls out of suspension of the thin, near-surface, river plume. The remaining fraction and the riverine coarse sediment form a large sediment bar 10 km long, up to 6 m in height and extending across the whole width of the channel near the mouth. This bar, as well as shoals in the estuary, partially pond the mid- to upper-estuary. This bar builds up from the deposition of riverine sediment during a wet season with high runoff and can raise mean water level by up to 2 m in the upper estuary in the low flow season. This ponding effect takes about three successive dry years to disappear by the sediment forming the bar being redistributed all over the estuary by tidal pumping of fine and coarse sediment in the dry season, which is the low flow season. The swift reversal of the tidal currents from ebb to flood results in macro-turbulence that lasts about 20 min. Bed load transport is preferentially landward and occurs only for water currents greater than 0.6 m s~(-1). This high value of the threshold velocity suggests that the sand may be cemented by the mud. The Daly Estuary thus is a leaky sediment trap with an efficiency varying both seasonally and inter-annually.
机译：对热带，大潮汐，戴利河口的水和沉积物动力学进行了实地研究。河口很浅，很浑浊，长约100公里，入口呈漏斗状。在潮湿，高流量的季节，河口的正常潮汐范围可能会受到限制，具体取决于流入量，淡水在河口处占主导地位。那时，沉积物从稀薄的近地表河羽悬浮液中悬浮下来后，一部分细颗粒泥沙就作为底部标记的星状胶质层向海上输出。其余部分和河道粗沙形成长10 km，高6 m的大型泥沙条，并延伸至河口附近整个河道。该栅栏以及河口的浅滩部分地掩盖了河口中部至河口上方。该条是在高径流量的湿润季节中河流沉积物的沉积物上堆积而形成的，在低流量季节的上河口，平均水位最多可升高2 m。这种积水作用大约需要连续三年的干旱年才能消失，这是由于在干燥季节（即低流量季节）通过潮汐泵送细颗粒和粗颗粒沉积物而使条形沉积物重新分布在河口，从而消失了。潮流从退潮到洪水的迅速逆转导致持续约20分钟的宏观湍流。床层负荷运输优选为陆运，仅在水流大于0.6 m s〜（-1）时发生。阈值速度的高值表明沙子可能被泥浆胶结。因此，戴利河口是一个漏水沉积物陷阱，其效率随季节和年际变化。

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