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Current reversals in a large tidal river

Zhang, Fanyi, Lin, Binliang and Sun, Jian 2019. Current reversals in a large tidal river. Estuarine, Coastal and Shelf Science 223 , pp. 74-84. 10.1016/j.ecss.2019.04.017

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A tidal river is a special zone where the basic hydrodynamic process is the interaction between riverine flow and tides. Existing studies focus mainly on the water level fluctuations, while the effort is limited regarding the flow regime between uni- and bi-directional currents. Along a tidal river, the current direction reverses where the landward flow meets with seaward flow. So far, the occurrence and movement of current reversal is not fully investigated, and the number and location of reversal points are not well understood. In this study, the water flow in the Yangtze tidal river was simulated using a hydrodynamic model, and the phenomenon of current reversals in the tidal river were investigated. It is found that in the dry season up to three reversal points may occur simultaneously, including two convergence points and one divergence point, separating the entire tidal river into two seaward-current reaches and two landward-current reaches. These multiple reversal points result from the co-existence of the preceding and present flood tidal waves. During a spring tide the peak landward flux of the preceding wave can reach up to 10,000 m3/s, about the same magnitude as the riverine discharge and the length of the landward-current occupation is as large as 120 km. It was also found that a current reversal point always coexists with a zero-gradient point of water level, and the location of this reversal is downstream of the zero-gradient point. The reversals shift landward from the river mouth consecutively, and could finally disappear farther at the upper reach of the tidal river. The bidirectional flow could extend up to 550 and 200 km upstream from the river mouth in the dry and wet seasons, respectively. The current reversals are influenced by the discharge regulation of the Three Gorges Dam. These movements of current reversals in the flow regime could furtherly have significant impact on local hydrodynamic process and material transportation.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Publisher: Elsevier
ISSN: 0272-7714
Date of Acceptance: 13 April 2019
Last Modified: 09 Jun 2020 01:31

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