Numerical Modeling of storm surge for the coastal region of Bangladesh

Abstract

This study investigates the estimated water levels during a cyclonic storm due to the interaction of tide and surge which also includes air bubble entrainment along the coastal areas of Bangladesh. Thus, a two-dimensional, vertically integrated hydrodynamic model in Cartesian coordinates has been developed. The model equations are solved using finite difference schemes implementing a staggered C-grid. Nested scheme methods are used to incorporate the complexity of the coast in order to not waste central processing unit time. Along the northeast corner of the innermost scheme or the very fine mesh scheme (VFMS), the Meghna river discharge is considered and the coastal and island boundaries are approximated via proper stair steps. A stable tidal condition over the area of interest is produced by making the sea level oscillate with the major tidal constituent M2 through the southern open boundary of the parent scheme or the coarse mesh scheme (CMS). The model is used to compute the water levels due to tide-surge interaction including the air bubble effect for the April 1991 cyclone. The model results are found to compare well with the observations from Bangladesh Inland Water Transport Authority. Therefore, the model is found to adequately simulate water levels which is in the presence of air bubbles. Additionally, it can also be observed that water levels are affected by factors such as river discharge and inverse barometer among others.