A seawall made of a vertical slit caisson is tested for reflection coefficients, overtopping characteristics, and aeration capacity with irregular or regular waves. The model scale of 1/25 is used for the experiments of overtopping characteristics, and that of 1/15 is used for the experiments of the other two. From the results of these tests, the optimum opening ratio and the configuration of the front slit can be chosen. The required crest height of its parapet is also made clear.
　From the viewpoint of aeration capacity, this seawall is compared with other three types of seawall including a 1/30 smooth slope. The aeration rate is measured with four dissolved-oxygen meters, and is recognized to be dependant on the rate of energy dissipation in wave breaking. According to this test, both this seawall and the seawall covered with a mound of artificial concrete blocks have larger capacity than an upright seawall has.