Numerical Simulation of Cold Front-Related Hydrodynamics of Wax Lake Delta
This study applies a three-dimensional numerical model ECOM-si to simulate the circulation in the Wax Lake delta under winter cold front conditions. This model uses real topography and bathymetry of the area to reproduce tides and the circulation between December 2012 and January 2013, which captures a total of seven cold front passages. The model results demonstrate that the circulation in the Wax Lake delta area is significantly affected by the winter cold fronts. The major findings are: (1) Water fluxes in the delta distributary network are not solely propagated within the channels but also between the channels, indicating inundation process by water intrusion onto the saltmarshes, which accounts for ~25% of water flux. (2). The current flows follow the wind direction change. Along-channel current dominates while cross-channel water transport occurs at the southwester lobe during post-frontal passage. The long-term impact on sediment transport will be the lobe shift to southeastward and thus lead to a significant change in geomorphology in the delta. Water intrusion and a temporary reverse flow are observed from model results in the delta channel tip during prefrontal passage. (3) The cold-front-induced flushing event lasts 41-185 hours that flushed out 32% to 76% of total waters by seven cold front events. (4). Subtidal energy accounts for over 45% of total energy while tidal energy contributes to less than 25%. (5) Cold front-induced wind is the most important factor and dominates the hydrodynamic circulations of the Wax Lake delta in winter.
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