## 2 Physical Experiment  
### Experimental Setup  
The experiment was conducted in a wave flume located at the Korea Institute of Ocean Science and Technology (KIOST) in Busan, Republic of Korea. The dimensions of the wave flume are 50 m in length, 1.2 m in width, and 1.6 m in depth [12]. The wave flume is equipped with a piston-type wave maker developed by VTI (Vazquezy Torres Ingenieria, Spain) Corporation. The wave maker can generate a regular wave, an irregular wave, and a solitary wave. The wave paddle is made of stainless steel and glass fiber reinforced plastic. To reduce re-reflected waves at the wave paddle, an active absorption system was applied to the wave generation software (AwaSys 7), based on the digital filtering of signals from the wave gauges in the nearfield [13; 14]. Passive wave absorbers were placed to absorb wave energy at both ends of the wave flume. As shown in Figure 2a, 11 wave gauges (Equations (1)-(11)) were placed, and the model structure made of acrylic plates was placed 32.13 m from the left end of the wave flume. Without the model structure, the wave gauges from Equations (9) to (11) are used to analyze the incident wave heights of the target waves. The distance between Equations (9) and (10) is 0.3 m, and the distance between Equations (10) and (11) is 0.5 m.  
Figure 3 shows a conceptual design for the movable barrier on the revetment of Haeundae Marine City in Busan, Republic of Korea. The height of the movable barrier was designed to be 6.5 m. In a normal state, during which the movable barrier does not stand, the designed sea level is the approximate highest high water (Approx. H.H.W.). Under an abnormal state activating the movable barrier, the designed sea level is considered to be the storm surge height and the sea level rise (SLR). In this study, a 1/36 scale model was adopted to consider the bathymetry in the wave flume. The similitude ratio for the Froude similarity was then scaled down. At this scale, the weight of the tetrapod (T.T.P) was 3.051 N per each. T.T.Ps were randomly placed (considering those placed on the target site) for all experiments. Figure 2: Schematic sketch of the wave flume with the location of the model structure, with the wave gauges and pictures of the experimental equipment; (**a**) side view (unit: m); (**b**) wave flume; (**c**) wave maker; (**d**) passive absorbers. The first purpose of the experiments was to measure the discharge of the wave overtopping. Thus, a waterway was placed on top of the movable barrier, as shown in Figure 4. A water trap was installed behind the model to capture the overtopped waters during the experiment. In the water trap, a flowmeter (Manufacturer: NTON INTERNATIONAL, China; Model: K24 turbine digital oil fuel flow meter gauge for chemicals liquid water) was installed to detect the discharge of the wave overtopping. The measurement range was 0.01 to 0.12 m\({}^{3}\)/min, and the measurement accuracy was less than 1%. The discharge was measured and calculated during the full test time to be 30 min, corresponding to a full-scale time of 3 h. Figure 4 also shows the installed model structure in the wave flume. The model structure has been reproduced as similar as possible the design of the target site. The second purpose of this experiment was to measure the wave pressure and to determine the occurrences of impulsive wave pressures acting on the movable barrier, as shown in Figure 5. In order to characterize the wave pressure acting on the movable barrier, pressure measurements were taken at four points (p\({}_{1}\) to p\({}_{4}\)) in a normal state and at eight points (p\({}_{1}\) to p\({}_{8}\)) in an abnormal state. The pressure gauges use disk-type pressure transducers with 10 mm diameters. Table 1 shows the specification of the disk-type pressure transducer [15]. All pressure gauges were mounted at the digging holes in the desired locations of the model structure. To protect the pressure gauges from the impact of the armor unit, a safe guard was installed in front of the mounted pressure gauges.