Recently, it has increased the case to be constructed the breakwaters where thewater depth is deeperand the wave height is greater. The authors developed a new type of breakwater.This breakwater consists of wave absorbing caisson and sloping top caisson. Through the model experiments, the wave force formula, the reflection coefficient, and the wave overtopping quantity weredefined. However, it was not defined the relation between the crown height and the transmission coefficient ofthis breakwater. When the crown height of the breakwater is higher it can be tranquil. Otherwise, thebreakwater width must be extended because of the wave force increased. Then, it is important to define therelation between the crown height of the breakwater and the transmitted wave height and find theappropriately crown height of the breakwater.
In this paper, the authors carried out the experiments for several types ofbreakwaters by using irregular waves, and defined the formula for the transmission coefficient and the crown height of the breakwater to be required.