Wave overtopping at berm breakwaters: Experimental study and development of prediction formula

Prediction of overtopping rate plays a key role in the design and safety assessment of breakwater structures. In this study, the mean wave overtopping rate at hardly and partly reshaping berm breakwaters were investigated by means of small-scale physical model tests. The test program was designed to create a database with a wider range of wave steepness, berm width, berm level and crest level for the hardly/partly reshaping conditions with an initial slope of 1:1.50. The new formula was developed covering the comprehensive test conditions (including existing tests and newly-collected ones) using scaling arguments and data mining techniques. Dimensionless governing parameters were used in the development of the formulae, and it was found that the new formula represented the influence of relative water depth on the wave overtopping rate better than the other prediction models. Accuracy metrics such as RMSE and Bias indicated that the developed formula outperformed the existing prediction models within the range of significant overtopping rates. Moreover, the developed formula is simple and gives better insights into the physical significance of the variables in the overtopping process, and thus it is hoped it will be more appealing for engineering applications.