Abstract
The typhoon impact on an estuarine environment is complex and systematic. A three-dimensional hydrodynamic and salinity transport model with a high-resolution, unstructured mesh and a spatially varying bottom roughness, is applied to investigate the effects of a historical typhoon, Fongwong, which affected Shanghai, on the hydrodynamics and saline water intrusion in the North Branch (NB) of the Yangtze River Estuary (YRE). The model is well validated through observation data of the tidal level, current velocity and direction, and salinity. The numerical results of this typhoon event show that: (1) the tidal level and its range increase toward the upstream part of the NB due to the combined effects of the funnel-shaped plane geometry of the NB and the typhoon; (2) the current velocity and the flow spilt ratio of the NB varies with the tides, with a maximum increase by 0.13 m/s and 26.61% during the flood tide and a maximum decrease by 0.12 m/s and 83.33% during the ebb tide, i.e., the typhoon enhances the flood current and weakens the ebb current; (3) the salinity value increases in the NB to a maximum of 1.40 psu and water is well-mixed in the vertical direction in the typhoon’s stable and falling period. The salinity distribution gradually recovered to the normal salt wedge pattern in 3 days following the typhoon. Although this study is based on a site-specific model, the findings will provide valuable insights into saline water intrusion under typhoon events, and thus assist in implementing more efficient estuarine management strategies for drinking water safety.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
We aim to investigate responses of hydrodynamics and saline water intrusion in the North Branch (NB) of the Yangtze River Estuary (YRE) to Typhoon Fongwong, which landed in Shanghai, using a process-based numerical model based on MIKE3
A process-based, three-dimensional, hydrodynamic and salinity-transporting, numerical model based on MIKE3, with a high-resolution of unstructured mesh and spatially varying bottom roughness, is applied to investigate the effects of the historical Typhoon
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Saline water intrusion is a common phenomenon in estuaries, which is affected by different spatial-temporal hydrodynamic forces such as river discharge, sea level rise, tides, waves and cyclonic conditions [1]. Severe saline water intrusion, which may be caused by low river discharge and sea level rise (SLR), can impair fresh water supplies in local regions and threaten aquatic plants and animals [2]. The perturbation of winds and the fluvial flow interacting with tides increase the complexity of the dynamics and salinity distributions in the estuary system
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