Toe Scour of Seawall on a Steep Seabed by Breaking Waves

This paper reports experimental results of the toe scour of seawall on a steep seabed with slope of 1:5 under the action of breaking waves. The equilibrium toe scour profiles were investigated and the depths of toe scours related to the wave parameters were analyzed. Experimental results indicated that the depth of toe scour increased as the steepness of the incoming wave increased, but decreased with an increase in the water depth at the toe. The breaker types in front of the seawall were investigated. The scour depth due to a plunging breaker is larger than that of a spilling breaker or a nonbreaking wave in front of the seawall. The down-rush flow velocity induced from the wave rundown on the seawall was also investigated in the experiment, and it was found that the scour depth increased as the flow velocity at the toe increased. Empirical formulas of the relative scour depth in terms of the relative toe water depth or surf similarity parameter were obtained based on the experimental results.