Using fairly standard techniques, a vertically-integrated model is formulated for simulating the interaction between surge and tide in the Bay of Bengal. The model includes a simplified representation of the river system at the head of the Bay that permits the incorporation of the effect of fresh water input into the system. The equations of the model are nonlinear and their numerical solution, corresponding to prescribed surface wind stress, tidal forcing and fresh water discharge, enables the interactions between the three processes to be evaluated. Some early results are given that correspond to the passage of an idealized tropical cyclone across the analysis area.

An important part of the formulation of the model relates to the way in which nonlinearity and bottom friction are included. The questionable nature of this is emphasized and an alternative scheme is proposed. This involves the use of an energy-based closure scheme to parameterize the Reynolds' stresses together with a transformed set of coordinates to facilitate the numerical solution of the free surface problem. These ideas are introduced in connection with the simulation of tide and surge in an elongated channel which could be readily adapted to represent the river system at the head of the Bay of Bengal. This reformulation, together with a choice of parameters representative of conditions in the River Thames, England, is used to assess the validity of the assumptions made in the earlier formulation of the storm-surge model. […]