This communication is related to the energy dissipation by porous media. A particular attention is paid on the effects of specific surface on dissipated energy through a porous media constituted by a compact network of emerging vertical cylinders. Experiments have been performed with three porous structures with varying cylinder diameters. The porosity is chosen constant whereas the specific surface depends on diameters of cylinders. Two series of experiments have been carried out, the first with stationary flows and the second with regular waves. Finally, scale effects on the reflection and transmission coefficients are also studied.