Investigation of morphodynamic evolution in a shelf region of Bay of Bengal under extreme conditions

A comprehensive review of state of the art numerical modeling in the field of sea bed morphology during cyclonic events is of vital importance. In this study a high impact and devastating cyclone, Vardah (2016) is considered to understand the hydrodynamic conditions, whereas, the recent cyclone, Nivar (2020) is considered for investigating the morphodynamic changes along the continental shelf region off the state of Tamilnadu, India. Three different models are coupled intrinsically to simulate hydrodynamics of tides and surges, waves and morphodynamic conditions. Initially, the hydrodynamic and wave models are established and validated with field measurements for an extreme event. Then, morphodynamic model is coupled with validated wave and tide model. Furthermore, the validation of bed evolution is performed for two cases viz., currents only and combination of waves and currents. The combined effect of tides, waves and surges improves the morphodynamic predictions. The present paper emphasizes the spatial and temporal morphological changes along the radius of cyclone pertaining to the shelf region. It is observed that the impact of cyclone on morphodynamics is predominant upto half the radius of the cyclone along the coast and upto 25 m contour from the coast across the shelf region. In this study, the bed evolution and its rate of change at various locations along the coast and across the shelf are extensively discussed.