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首页> 外文期刊>Ocean Dynamics >Mechanisms of along-channel sediment transport in the North Passage of the Yangtze Estuary and their response to large-scale interventions
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Mechanisms of along-channel sediment transport in the North Passage of the Yangtze Estuary and their response to large-scale interventions

机译：长江口北通道沿河沉积物运移机理及其对大规模干预的响应

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摘要

The effects of large-scale interventions in the North Passage of the Yangtze Estuary (the Deep Waterway Project, DWP) on the along-channel flow structure, suspended sediment distribution and its transport along the main channel of this passage are investigated. The focus is explaining the changes in net sediment transport in terms of physical mechanisms. For this, data of flow and suspended sediment concentration (SSC), which were collected simultaneously at several locations and at different depths along the main channel of the North Passage prior to and after the engineering works, were harmonically analyzed to assess the relative importance of the transport components related to residual (time-mean) flow and various tidal pumping mechanisms. Expressions for main residual flow components were derived using theoretical principles. The SSC revealed that the estuarine turbidity maximum (ETM) was intensified due to the interventions, especially in wet seasons, and an upstream shift and extension of the ETM zone occurred. The amplitude of the M 2 tidal current considerably increased, and the residual flow structure was significantly altered by engineering works. Prior to the DWP, the residual flow structure was that of a gravitational circulation in both seasons, while after the DWP, there was seaward flow throughout the channel during the wet season. The analysis of net sediment transport reveals that during wet seasons and prior to the DWP, the sediment trapping was due to asymmetric tidal mixing, gravitational circulation, tidal rectification, and M 2 tidal pumping, while after the DWP, the trapping was primarily due to seaward transport caused by Stokes return flow and fresh water discharge and landward transport due to M 2 tidal pumping and asymmetric tidal mixing. During dry seasons, prior to the DWP, trapping of sediment at the bottom relied on landward transports due to Stokes transport, M 4 tidal pumping, asymmetric tidal mixing, and gravitational circulation, while after the DWP the sediment trapping was caused by M 2 tidal pumping, Stokes transport, asymmetric tidal mixing, tidal rectification, and gravitational circulation.
机译：研究了长江口北通道（深水航道工程，DWP）的大规模干预对沿通道流动结构，悬浮泥沙分布及其沿通道主要通道的运输的影响。重点是根据物理机制解释净沉积物输送的变化。为此，在工程工作之前和之后，沿北通道主河道在多个位置和不同深度同时采集的流量和悬浮沉积物浓度（SSC）数据进行了谐波分析，以评估水流和悬浮泥沙浓度的相对重要性。与剩余（时间平均）流量和各种潮汐抽水机制有关的运输要素。使用理论原理推导了主要剩余流量分量的表达式。 SSC指出，由于采取了干预措施，特别是在雨季，河口最大浊度（ETM）增强了，并且发生了ETM区上游的移动和扩展。 M 2潮流的幅度大大增加，并且剩余水流结构因工程工作而发生了显着变化。在DWP之前，两个季节的残余流量结构都是重力循环，而在DWP之后，在雨季期间整个通道都有向海流动。对净泥沙输送的分析表明，在湿季和DWP之前，泥沙的捕集是由于不对称的潮汐混合，重力循环，潮汐整流和M 2潮汐抽水造成的，而在DWP之后，泥沙的捕集主要是由于斯托克斯回流和淡水排放引起的向海运输以及由于M 2潮汐泵送和不对称潮汐混合而引起的陆运。在干旱季节，在DWP之前，由于斯托克斯运输，M 4潮汐泵送，不对称的潮汐混合和重力循环，底部的泥沙截留依赖于陆运，而在DWP之后，泥沙的截留是由M 2潮汐引起的。抽水，斯托克斯输运，不对称潮汐混合，潮汐整流和重力循环。

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