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首页> 外文期刊>Journal of Geophysical Research, C. Oceans: JGR >Flood dispersal and deposition by near-bed gravitational sediment flows and oceanographic transport: A numerical modeling study of the Eel River shelf, northern California
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Flood dispersal and deposition by near-bed gravitational sediment flows and oceanographic transport: A numerical modeling study of the Eel River shelf, northern California

机译：近地心引力沉积物流和海洋运动对洪水的扩散和沉积作用：加利福尼亚北部鳗鱼河架子的数值模拟研究

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摘要

A large flood of the Eel River, northern California, created a thick sediment deposit between water depths of 50 and 70 m in January 1997. The freshwater plume, however, confined sediment delivery to water depths shallower than 30 m. Mechanisms proposed to explain the apparent cross-shelf transport include dispersal by oceanographic currents, resuspension by energetic waves, and gravitationally forced transport of a thin layer of fluidized mud. Field observations indicate that these processes were all active but cannot determine their relative significance or whether these mechanisms alone explain the location, size, and timing of deposition. Approximately 30% of the sediment delivered by the Eel River is accounted for in the midshelf mud bed and inner shelf, but the fate of the remaining 70% is uncertain. A three-dimensional, hydrodynamic model was used to examine potential mechanisms of sediment transport on the Eel River shelf. The model includes suspended sediment transport and was modified to account for a thin, near-bed layer of fluidized mud. It was used to simulate flood dispersal on the Eel River shelf, to compare the relative importance of transport within the near-bed fluid mud layer to suspended sediment transport, and to evaluate sediment budgets for floods. Settling properties of fine-grained sediment, both within the flood plume and the fluid mud layer, critically impact depositional patterns. To a lesser degree, wind-driven ocean currents influence the volume of sediment that escapes the shelf, and wave magnitude affects the cross-shelf location of flood deposits. Though dilute suspension accounts for a large fraction of total flux, cross-shelf transport by gravitational forcing appears necessary to produce a midshelf mud deposit similar in volume, location, and timing to those seen offshore of the Eel River.
机译：1997年1月，加利福尼亚州北部的鳗鱼河大洪水在50至70 m的水深之间形成了厚厚的沉积物沉积物。然而，淡水羽流将沉积物输送到30 m以下的水深处。提出的解释表观跨架运移的机制包括通过洋流扩散，通过高能波重悬以及在重力作用下流化薄层流化泥浆。现场观察表明，这些过程都是活跃的，但不能确定它们的相对重要性，或者这些机制是否能单独解释沉积的位置，大小和时间。鳗鱼河输送的沉积物约有30％属于中层泥床和内陆架，但其余70％的命运尚不确定。使用三维水动力模型来研究鳗鱼河架上泥沙输送的潜在机理。该模型包括悬浮泥沙运移，并经过修改以解决流化泥浆的薄近床层问题。它被用来模拟鳗鱼河架子上的洪水扩散，比较近床流体泥浆层内运输对悬浮泥沙输送的相对重要性，并评估洪水的泥沙预算。洪流羽流和泥浆液层内的细颗粒沉积物的沉降特性均会严重影响沉积模式。在较小程度上，风力驱动的洋流会影响从架子逸出的沉积物的体积，而波幅会影响洪水沉积物的跨架位置。尽管稀悬浮液占总通量的很大一部分，但通过重力强迫进行的跨架运输似乎是必要的，以产生与Eel River海上看到的沉积物相似的体积，位置和时间。

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