Influence of Wave-Current Interaction on a Cyclone-Induced Storm-Surge Event in the Ganges-Brahmaputra-Meghna Delta: Part 2-Effects on Wave

The Ganges-Brahmaputra-Meghna delta, located in the southern part of Bangladesh, is periodically exposed to severe tropical cyclones. It is estimated that two-fifths of the world's total impact from tropical-cyclone-induced storm surges occur in this region, and these cause fatalities and economic losses every year. A barotropic numerical 3D model is used to investigate wave dynamics during a cyclone-induced storm-surge event. The model is calibrated and validated for Cyclone Sidr (2007) and applied to ten idealized cyclonic scenarios. Numerical experiments with different coupling configurations are performed to understand wave-current interactions on significant wave heights. Results show that the water level is the dominant factor in significant wave height modulation when the wave propagates into shallower regions from the deeper ocean, whereas the current modulates the deep ocean wave height. The WCI causes higher significant wave heights in shallower waters close to the coast compared with the deep ocean. Wave energy dissipation related to whitecapping processes plays a greater role in reducing the wave height nearshore than the dissipation due to depth-induced breaking and bottom friction in the GBMD during a cyclone-induced storm-surge event.

Automated summary

The Ganges-Brahmaputra-Meghna delta in southern Bangladesh experiences severe tropical cyclones, accounting for 40% of the global impact from storm surges caused by cyclones. A numerical 3D model was used to study wave dynamics during a cyclone-induced storm surge event, showing that water level and current have significant effects on wave heights. The study also found that the Whitecapping Induced Energy (WCI) mechanism leads to higher wave heights in shallower waters near the coast.