Violent overtopping of vertical seawalls under oblique wave conditions

Most prediction methods for wave overtopping are based on physical model tests under simple 2-D conditions. This paper describes final results of a physical model study measuring mean and wave-by-wave overtopping discharges over a vertical seawall under impulsive and oblique long-crested wave attack. The design guidance offered for these conditions shows that a significant reduction in overtopping can only be expected for obliquities > 30 degrees. With increasing obliquity, impulsive events transform to "impact-like" events (0 degrees < Chi <= 30 degrees) and then eventually to reflecting (non-breaking) waves (60 degrees). Spatial variability of overtopping volumes along the seawall could be measured and was considered in the design guidance.