Tide–surge interaction at the head of the Bay of Bengal during Cyclone Aila

Abstract Tide–surge interaction serves a critical role in shallow coastal regions in modifying the characteristics of peak water levels during storm events. In the present study, we investigated the tide–surge interaction in the coastal waters at the head of the Bay of Bengal (BoB) during Cyclone Aila, a Category 1 cyclone. The space–time characteristics of the interaction were discussed. The numerical simulation results reveal that the interaction was significant with interaction heights of up to 1 m at many locations that were even a few hundred kilometres away from the maximum surge. The spatial pattern of the interaction exhibited lower values in the central part of the head of the BoB due to the reduction in the width of the continental shelf and the relatively lower tidal amplitudes in this region compared with those in the remaining portion of the head of the BoB. The overall effect of the interaction was the reduction in the peak water levels. Favourable factors such as the extreme shallowness of the coastal waters, tidal contribution, and complex coastline geometry explain the strong tide–surge interaction at the head of the BoB.