Overtopping flow velocity (OFV) and overtopping layer thickness (OTL) are essential parameters in breakwater design. Several empirical equations to predict these parameters are available in many works of literature, but most of the equations were derived based on impermeable structures such as sea dikes. In this study, we experimented with overtopping waves over a composite breakwater with tetrapod armor units. In the experiments, wave overtopping was generated from regular waves. We used a digital image-based velocimetry method, bubble image velocimetry (BIV), to measure the OFV and digitize the corresponding image to obtain the OLT. The patterns of OFV and OTL with respect to time steps, wave conditions, and corresponding events were provided and discussed. The application of the widely used empirical equations for sea dike to breakwater was also tested by calibrating the coefficients. New empirical coefficients and roughness factors were suggested to reduce the difference between predicted and measured OFV and OLT on breakwater through the bootstrap resampling technique. This study provides modified empirical equations on wave overtopping, which is further applicable to breakwater design.

In Korea, the hydraulic model tests for measuring the wave overtopping have been almost conducted with no bottom slope or single slope condition in Korea. In this study, the bottom seabed for the coastal road area was fabricated at the wave flume and the wave overtopping was measured. The overtopping rate was also measured with the numerical modelling by OLAFoam. The measuring data were compared with EurOtop manual. It could be known the the influence of the foreslope in front of the vertical wall was significant and the these effects should be concerned when designing the coastal structures. And also it could be known that OLAFoam could be used to predict the wave overtopping rate for the complex bottom topography.

The crown wall with parapet on top of the rubble mound breakwater represents a relatively economic and efficient solution to reduce the wave overtopping discharge. However, the inclusion of parapet leads to increased wave pressure on the crown wall. The wave pressure on the crown wall is investigated by physical model test. To design the crown wall the wave loads should be available, and the horizontal wave pressure is still unclear. Regarding to the horizontal wave pressure on the crown wall, a series of experiments were conducted by changing the rubble mound type structure and the wave conditions. Based on these results, pressure modification factors of Goda’s (1974, 2010) formula have been suggested, which can be applicable for the practical design of the crown wall of the rubble-mound breakwater covered by tetrapods.

Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r2>0.8)the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high(A0/h0<0.07in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification.

Kim, Y.-T., and Lee, J.-I., 2018. Wave Transmission Coefficient for Rubble Mound Structures with Superstructures. In: Shim, J.-S.; Chun, I., and Lim, H.-S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 21–25. Coconut Creek (Florida), ISSN 0749-0208. The wave transmission coefficents for rubble mound structures with the superstructures were investigated using two-dimensional hydraulic tests. Most previous studies on the wave transmission coefficient were about the low crsted structures. And the main armors were almost the rock and the superstructures were not constructed. The superstructures have an important role in reducing the wave overtopping, improving the stability and so on. In this study, the wave transmission coefficient for the rubble mound structures covered with the tetrapod (TTP) on the slope with the superstructures were investigated. Also the effect of the width of superstructures and the number of armour layer in front of the superstructures were investigated.

The average wave overtopping volume is used as a design parameter for coastal structures. The crest elevation of a structure should ensure the wave overtopping volume within acceptable limit. In this study, the effects of the width of armour crest in front of the superstructure and the structure slope on the average wave overtopping volume were experimentally examined for a rubble-mound structure covered with tetrapods. Twodimensional physical model tests on a rubble-mound structure were performed for measuring the wave overtopping under various water depth and wave conditions. As the width of the armour crest increased, the average wave overtopping volume decreased, and it also decreased when the structure slope was gentle. An empirical formula from the experimental data was proposed to predict the average wave overtopping volume for a rubble-mound structure.