Hydrodynamic characteristics of porous seawall protected by submerged breakwater

•Hydrodynamic characteristics of porous seawall protected by submerged breakwater are tested.•Regular waves with wide ranges of wave heights and periods are used.•Influence of different structural parameters is investigated.•Empirical equations for the hydrodynamic coefficients are developed.

In this paper, the hydrodynamic efficiency of a new type porous seawall is experimentally studied by using physical models. The seawall consists of front steel screen, back solid wall and filled rock-core. A submerged breakwater with different parameters is installed in front of the seawall. The wave run-up on the seawall and the wave reflection due to the seawall with or without the submerged breakwater are investigated. The wave transmission due to the submerged breakwater is investigated also. The results indicate that the run-up and reflection coefficients due to the seawall only decrease with increasing of: the relative water depth (h/L); the wave steepness (Hi/L); the relative seawall width (b/h); and the seawall porosity (n). The submerged breakwater decreases the run-up on the seawall and the wave reflection by about 20–60% and less than 70%, respectively. In addition, the submerged breakwater is achieving low transmission coefficients with increasing of the relative breakwater height (D/h) and the relative breakwater width (B/h).