Experimental investigation into wave interaction with a rubble-mound submerged breakwater (case study)

Experimental tests on the interaction between waves and a submerged rubble-mound breakwater (SBW) were performed in the wave flume at the Institute of Hydroengineering PAS in Gdańsk (Poland). A model of a submerged breakwater was prepared based on the constructions built in 2006 in the Polish zone of the Baltic coast, in Gdańsk Bay, in the region of Gdynia Orłowo (Orłowo Cliff). The tests were carried out for regular waves (varying parameters: height, period, length, and steepness) whose parameters were determined on the basis of the actual wind field occurring in Gdańsk Bay. The experiment was conducted for two water levels corresponding to the actual long-term mean sea level (msl) of 500 cm as well as a storm surge of 550 cm. The research has focused on the analysis of the amount of wave energy transmitted into the lee region and the determination of parameters that affect the transmission size. Types of wave-breaking were described based on the extensive video and photographic documentation prepared during the measurements. Based on the results obtained from the experiment and the previous research on the functioning of submerged breakwaters in the coastal zone, including both numerical modelling as well as field research and field observations, the efficiency of the structure was assessed.