Steepest wave criterion

The steepest-wave criterion is the wave-breaking limit on steepness, the ratio of height to length H over L, beyond which a regular gravity wave cannot exist and breaks. In deep water the theoretical Stokes limiting steepness is H over L = 0.142, close to 1 over 7, reached when the crest angle becomes 120 degrees and the crest particle speed equals the wave celerity. In shallow water the depth limit governs instead, with breaking near H over h about 0.78. The criterion caps the amplitude of design regular and equivalent design waves, and flags steep sea states where nonlinear and breaking loads, not linear theory, set the structural demand.