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Suspended sediment transport at a tidal river divergence.

机译：潮汐河分流处的悬浮泥沙输送。

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摘要

This study investigated suspended sediment routing through a diverging tidal river channel, a complex landform largely ignored in the geomorphic literature. The lack of research is largely due to the assumption that suspended sediment 'goes with the flow', meaning that a calculation of the ratio of discharge divided between downstream branches will yield a similar ratio for suspended sediment concentrations (SSC) by proxy. The goal of this study was to determine: (1) if the 'go with the flow' assumption is legitimate and (2) if non-uniform distributions of cross-channel SSC driven by secondary flows and channel bathymetry play a role in suspended sediment routing through a tidal river divergence. These questions were investigated at a divergence on the Sacramento River at Georgiana Slough in the Sacramento-San Joaquin River Delta in central California over a range of flow and tidal conditions. Instrumentation was boat-based and consisted primarily of an Acoustic Doppler Current Profiler and Optical Backscatterance Sensors to measure flow and suspended sediment across six channel cross-sections. Fixed tide gages were also installed in each branch of the divergence. The data show that channel bathymetry and secondary flows contributed to preferential transport of suspended sediment into the larger downstream branch, but that the total effect was small (∼3%). During periods of low-flow coupled with flood tide, significant variations in SSC between the downstream branches occurred for a short period of time, due to a reversal of flow direction on the larger downstream branch (lower Sacramento River). Different tidal signatures of the downstream branches resulted in a seaward directed water slope in Georgiana Slough, giving it the capacity to receive the flows of both the mainstem and lower Sacramento River. This condition was brief (∼1 hr) and total suspended sediment discharge was minimal due to small flow velocities. A modeling exercise showed that the effects of secondary flows and non-uniform cross-channel distribution of SSC were overwhelmed by the greater magnitude downstream velocity field. Resource managers interested in suspended sediment availability for tidal marsh reconstruction can use the 'go with the flow' assumption with a large degree of certainty.
机译：这项研究调查了通过一条分散的潮汐河道的悬浮泥沙路线，潮汐河道是一种复杂的地貌，在地貌文献中被忽略。缺乏研究的主要原因是悬浮泥沙“随流量而流”的假设，这意味着计算下游分支之间的流量比将通过代理产生相似的悬浮泥沙比（SSC）。这项研究的目的是确定：（1）“顺流而下”的假设是否合理，以及（2）由二次流和测深法驱动的跨河SSC的不均匀分布是否在悬浮泥沙中起作用通过潮汐河道发散。这些问题是在加利福尼亚中部萨克拉曼多-圣华金河三角洲佐治亚州泥沼的萨克拉曼多河上，在一定流量和潮汐条件下的分歧处进行调查的。仪器是基于船的仪器，主要由声学多普勒电流剖面仪和光学反向散射传感器组成，用于测量六个通道横截面的流量和悬浮沉积物。固定的潮汐计也安装在分叉的每个分支中。数据表明，航道测深法和次要流量有助于将悬浮泥沙优先输送至较大的下游分支，但总影响较小（约3％）。在低流量加上洪水潮期间，由于较大下游分支（萨克拉曼多河下游）的水流方向发生逆转，下游分支之间的SSC发生了短暂变化。下游支流的不同潮汐特征导致佐治亚州泥沼向海定向水坡，使其有能力接收主干河和萨克拉曼多河下游的水流。这种情况是短暂的（〜1小时），并且由于流速小，总的悬浮沉积物排放量很小。建模实验表明，更大的下游速度场会淹没二次流和SSC跨通道分布不均匀的影响。对潮汐沼泽重建中悬浮沉积物的可用性感兴趣的资源管理者可以高度肯定地使用“顺其自然”的假设。

著录项

  • 作者

    Lange, Mark David.;

  • 作者单位

    University of Southern California.;

  • 授予单位 University of Southern California.;
  • 学科 Physical Geography.;Hydrology.;Geology.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 238 p.
  • 总页数 238
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:38:19

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