Wave-structure interaction is an important topic concerning the modelling and performance optimization of Wave Energy Converters (WECs) operating in nearshore and coastal areas. In this work a BEM is developed and applied to the investigation of variable bathymetry (bottom slope and curvature) effects on the performance of surge-type wave energy converters excited by harmonic monochromatic waves in the two-dimensional space. Numerical results are presented illustrating the effect that the modification of the wave field has on the devices and the effects of depth variation in conjunction with other parameters like inertia and power-take-off, on their performance.