Integrated Modeling of Typhoon Damrey’s Effects on Sediment Resuspension and Transport in the North Passage of Changjiang Estuary, China

Typhoon triggers estuarine heavy metal risk by regulating the multifractal grainsize of resuspended sediment.

To reveal the mechanism for the transport of water and suspended sediments by wind-induced estuarine residual circulations, in situ moorings of acoustic Doppler current profilers were conducted in microtidal Onsan Bay. Water circulation within the bay was characterized by freshwater discharge from the river and free exchange with the open sea, showing current seaward outflow and landward inflow in the western (M1) and eastern (M2) flanks of the navigation channel, respectively. This circulation was influenced by the intrusion of alongshore currents strengthened (weakened) by the northerly (southerly) winds. In M1, seaward outflow was dominant, except for surface disturbances caused by winds. Meanwhile, the classical estuarine circulation (72% of the entire period) in M2, which prevailed under the southerly winds, was switched into the reversed estuarine circulation when the stress of the northerly wind persistently exceeded 0.005 Pa (>5 h). The water transport (Trw) in M1 did not significantly vary depending on the wind direction, but the Trw in M2 could be reduced by 53% within 10-m above the bed as the southerly winds were transited into northerly winds. Over the entire period, Trw tended to be mutually compensated for and balanced by the circulation system between M1 and M2. On average, however, the sediment transport (Trsed) in M2 was 37% higher than M1, indicating that the suspended sediments were preferentially deposited within the bay. Most of the suspended sediments causing the deposition within the bay were mainly transported by estuarine residual circulation rather than tidal pumping. In M2, the frequent resuspension events of the fine-grained sediments (d50 = 6 μm) due to the high variability of the along-channel current velocity could maintain a sediment concentration of 18 mg l−1 in the bottom layer. These suspended sediments responded mainly to landward current in bottom layer (classical estuarine circulation) rather than seaward current (reversed estuarine circulation), contributing to increase in Trsed. Considering that the prevailing winds from 2013 to 2020 in Onsan Bay mainly create a favorable condition for the development of the classical estuarine circulation, the sedimentation is expected to persist. 

Wind-induced switch of estuarine residual circulations and sediment transport in microtidal bay

这篇论文扩大放射应力的常规概念(Longuet-Higgins 和斯图尔特， 1964 ) 在进步的水里向站的波浪招手，以便它的垂直侧面能以一个新技术方法被定义并且计算。水动力学被结合的数字模型在承受波浪的垂直地变化的放射压力被用来模仿被在垂直的节承受波浪导致的水流。推迟的沉积运输的数字建模然后被执行模仿水流由好沉积组成的床的进化。模仿的 scour 和免职模式在对优先的实验室和地观察的质的同意。

Currents induced by vertical varied radiation stress in standing waves and evolution of the bed composed of fine sediments

Formation of turbidity maximum in the Modaomen Estuary of the Pearl River, China: The roles of mouth bar

After the construction of the Deep-water Navigational Channel (DNC) in the North Passage of the Changjiang Estuary, siltation in the channel became severe during the flood season in the navigation channel. To investigate the causes, field observations of tidal current, salinity and suspended sediment concentration (SSC) were conducted by 16 anchored boats in the navigation channel of North Passage during spring tide in the flood season. The across-channel differences of salinity, SSC, and near bottom residual sediment transport at the high siltation area of the DNC were observed and analyzed. The results show that the near bottom SSC presented a south-to-north decreasing trend during the flood tide at the lower reach of the North Passage. During the ebb tide, a suspended sediment cloud of extremely high concentration was detected within the channel. The observed longitudinal sediment trapping was not only shown as the turbidity maximum (TM) trapped within the moving salinity front but also as the longitudinal convergence of the residual sediment transport at the middle reach. The mechanism for the longitudinal sediment trapping was due to the tidal asymmetry in mixing. The observed lateral sediment trapping was prominent at the most severe siltation area of the DNC in the section #2. The lateral sediment trapping at the across-channel section #2 was not only shown as the lateral transport of the sediments from the channel flanks during the flood slack but also as the lateral convergence of the residual sediment transport during the entire spring tidal cycle. The mechanism for the lateral sediment trapping was dominated by the advective transport. The lateral impact on the channel sediment trapping was not negligible in view of the depth-mean lateral tidal straining on the water stratification. The observed convergences of both the longitudinal and the lateral residual sediment transports were responsible for the severe channel siltation in the North Passage.

Observation of the sediment trapping during flood season in the deep-water navigational channel of the Changjiang Estuary, China

Shen, Q; Gu, F; Qi, D, and Huang, W, 2014 Numerical study on the flow and sediment variation affected by the sea-level rise in the north passage of the Yangtze estuary A three-dimensional, sigma coordinate coastal ocean model, based on unstructured C-grid and semi-implicit finite volume method, is built to study the flow and sediment variation affected by the sea-level rise (SLR) at the north passage of the Yangtze estuary Firstly, the details of the numerical method used in this model are introduced, including the layout of model variables, the discretization of the governing equations and the semi-implicit method, etc Then, two test cases are employed to verify the proposal model, including an idealized test case as well as a simulation of the tidal flow and mass transport at the north passage of the Yangtze Estuary Finally, based on the verified model, a numerical study on the flow and sediment variation affected by the SLR at the north passage of the Yangtze estuary is carried out T

Numerical Study of Flow and Sediment Variation Affected by Sea-Level Rise in the North Passage of the Yangtze Estuary

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Observation of the sediment trapping during flood season in the deep-water navigational channel of the Changjiang Estuary, China

Numerical Study of Flow and Sediment Variation Affected by Sea-Level Rise in the North Passage of the Yangtze Estuary