Purpose. The work consists in developing a mathematical model to study the flooding processes in the Don delta during the extreme surges.

Methods and Results. The level fluctuations in the Taganrog Bay are calculated based on solving a system of equations for long waves in a homogeneous incompressible fluid in the Coriolis force field. The problem is solved by the finite-difference methods on high-performance computing systems. The algorithm for determining the area of the Don delta flooding in the process of a surge is given. It is based on comparing the heights of the delta area to the water level and on taking a decision whether to flood or drain a computational cell. The calculation results are compared to the water level values observed at the gauging station, and are also displayed as a map diagram of the flooded area.

Conclusions. The proposed model should be applied in case of the extreme surges when a significant delta area is flooded. The model makes it possible to calculate accurately the hydrodynamic parameters of a flow including the magnitude of water level difference. The proposed algorithm determining whether flooding or draining is required for a computational domain, permits to reveal the areas in the Don delta where flooding depends on the wind conditions.