Nested Numerical Schemes to Incorporate Bending Coastline and Islands of Bangladesh and Prediction of Water Levels due to Surge

A vertically integrated shallow water model is developed in Cartesian coordinate system to solve the shallow water equations using a semi-implicit finite difference technique for computing surge associated with some storms in the Bay of Bengal. For this purpose, a fine mesh scheme incorporating the coastal belt and islands has been nested into a coarse mesh scheme covering up to 15° N latitude in the Bay of Bengal. In the fine mesh scheme, all the major islands are incorporated through proper stair step representation. For the existence of so many small and big islands and also for high bending of the coastline along the Meghna estuary, a very fine mesh scheme for the region between Barisal and Chittagong is again nested into the fine mesh scheme. The computed water levels are found to be in good agreement with those of observed.