A two-dimensional horizontal hydrodynamical model has been used to estimate the changes that a harbour road will cause in the water exchange of an estuary. The research area has been the Kokemäenjoki river estuary on the coast of the Gulf of Bothnia in western Finland.
The numerical model has been verified on the basis of a regression model describing the water exchange of the estuary at present with a multiple correlation squared of 0.9. The factors having an influence on the water exchange are the wind, the sea level fluctuation and the river discharge.
The changes in the water exchange have been considered during a dry spell, a flood period and an average year with three different cross-section areas of the road line. The accuracy and reliability of the estimation are found to be very satisfactory.