Prediction of impact of large constructions in gulf on bathymetry of its remote parts as inverse problem of wave theory

Abstract

The intentional bottom changes associated with construction of dams, breakwaters and other large structures in gulfs (or harbors) often lead to unintentional delayed bottom changes at remote locations. These unintentional changes can occur due to adjustment of frequencies of natural water oscillations in gulfs (or harbors) to the frequencies of natural water oscillations in the connected seas. Affecting conditions for wave propagation, a large structure changes the natural frequencies of the gulf because these frequencies are predetermined by the gulf size and bathymetry. The sea impact will restore the old natural frequencies of the gulf, but such a restoration requires change the bottom and shoreline at various locations along the gulf. Prediction of these remote changes can be formulated as an inverse problem for shallow water equations. The key to this formulation is the orthogonality of eigen modes of water level variation and water flux in the shallow water theory. The computed predictions of bathymetry changes are compared with observed trends of changes in the Gulf of Finland.