Polar coordinates shallow water storm surge model for the coast of Bangladesh

• Published in: Dynamics of atmospheres and oceans 1999-07, Vol.29 (2), p.397-413
• Main Authors: Roy, G.D., Kabir, A.B.M.Humayun, Mandal, M.M., Haque, M.Z.
• Format: Article
• Language: English
• Subjects: Coast of Bangladesh; Coastal oceanography, estuaries. Regional oceanography; Cylindrical polar coordinate; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Physics of the oceans; Shallow water
• ISSN: 0377-0265; 1872-6879
• DOI: 10.1016/S0377-0265(99)00012-3

A coastal shallow water model generally involves at least one coastal boundary which is curvilinear in nature. Representation of this curvilinear boundary needs special attention when a finite difference scheme is used. To incorporate the curvilinear coastal boundary and off-shore islands properly in the numerical scheme, we need fine resolution which may not be necessary away from the coast. In order to tackle this problem, a nested numerical scheme may be used where fine resolution for the coastal boundary region is nested into a course resolution scheme covering the whole analysis area. But this involves comparatively more memory and CPU time in the solution process. The present study aims at developing a storm surge model that may subsequently be modified for operational forecasting purpose for the coast of Bangladesh. A vertically integrated model is developed in a cylindrical polar coordinate system capable of incorporating bending of the coastline and off-shore islands with considerable accuracy without using any nesting. A comparison of CPU time and memory in the numerical computations between two types of modelling is described and it is found that the cylindrical polar coordinates model is economic. The model is applied for estimating the water levels at different coastal and island stations associated with a few storms that hit the coast of Bangladesh. It is found that the computed and observed water levels are in good agreement. Considering the computing time and other factors, it is found that the Polar Coordinates model is more suitable for operational forecasting purpose along the coast of Bangladesh.