A Shallow Water Model for Estimating Water Level During Tropical Storms Along the Coast of Bangladesh

The coastal region of Bangladesh is surrounded by coastline except to the south and there are several small and large islands in the offshore region. The coastlines are morphologically complex and it is extremely challenging to represent them accurately in the numerical scheme. To address this complexity, it is necessary to consider a very fine grid along the coastal zones whereas this is unnecessary away from the coasts. An approximately orthogonal grid system developed to solve vertically integrated shallow water equations along the coastal region of Bangladesh, utilising an in-house python code. The grid system consists a set of straight lines at a uniform angular distance through the origin O, at ( 23 ⁰ N, 90 . 25 ⁰ E) in the mean sea level (MSL) and a system of uniformly distributed concentric ellipses with the same centre as straight lines. To use finite difference scheme in numerical computation, the original grid system is transformed into a rectangular form in the transformed domain by applying suitable transformations. The model is applied to predict the water levels at different coastal and island stations associated with the recent storms Amphan and Bulbul that hit the coast of Bangladesh. The computational results are in good agreement with the observational data.