Wave Crest

The wave crest is the highest point of a surface-wave profile, where the water surface stands above the still-water level and the orbital motion of water particles is forward, in the direction of wave travel. It is the counterpart of the trough, the lowest point; the vertical distance between them is the wave height, and the horizontal distance between two successive crests is the wavelength. In shoaling water the crest sharpens and the trough flattens as the wave departs from the sinusoidal Airy form, and breaking begins when the crest particle speed reaches the wave celerity. Crest elevation drives wave runup and overtopping at coastal structures.