Berm Effects on the Probability Distribution of Individual Wave Overtopping Discharge over a Low-Crested Sea Dike

Existing studies on the distribution of individual wave overtopping over sea dikes have not taken the effects of the berm into consideration. In this study, a series of physical experiments have been conducted on smooth sea dikes with intermediate berm and low-crested slopes, aiming to gain the knowledge of the berm effects on the probability of wave overtopping $P_{ow}$ and the probability distribution of individual wave overtopping (characterized by a shape factor $b$ and a scale factor $a$, which are related to the probability of wave overtopping $P_{ow}$). Two prediction equations have been derived based on the new experiment data to account for the reduction effects of the berm on the parameters $P_{ow}$ and $b$. In both equations, the relative berm length appears to be more effective in reducing the two parameters in contrast to the relative water depth on the berm, and both parameters decrease with an increase in the relative berm length and a decrease in the relative water depth on the berm in an exponential manner. The equations give an insight into the influence of the berm on the probability distribution of individual wave overtopping and provide good predictions of the berm effects.