A coupled hydrodynamic modeling system for PHAILIN cyclone in the Bay of Bengal

Abstract

East coast of India is characterized by low to medium topography and an extensive network of major estuaries, bays, mangrove creeks, rivers and tidal inlets that permit inland flooding during tropical cyclones. A coupled wave+surge hydrodynamic modeling system (ADCIRC+SWAN) is implemented to simulate storm surge, still water level elevation and wave induced setup associated with 'Phailin', a very severe cyclonic storm that made landfall in the Odisha State, east coast of India, during October, 2013. The coupled model provides a realistic description on the dynamic interaction of tides, wind, waves and currents, which is critical for operational needs. The study assesses the role of wave-induced setup on the net water level elevation using time varying wave radiation stress that is dynamically updated in the coupled model run. Numerical experiments are carried out for both storm surge alone and coupled mode versions. Dependent upon complex bathymetry and coastal geometry, inclusion of wave-induced setup in coupled runs results in an additional 23-36% increase of peak surge relative to an uncoupled, surge-tide simulation. The significant wave height from coupled model also shows an excellent match with observed wave heights from a wave-rider buoy located offthe Odisha coast. The comparison of surge residuals between model and observation also exhibits a good match. The study highlights the importance of having a coupled wave-hydrodynamic model for operational needs in the north Indian Ocean.