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wave steepness The ratio of a wave's height to its length (expressed as a fraction or a decimal) or sometimes expressed as the ratio of length to height. Generally it is the steepness of waves that pose the greatest hazard to vessels underway, in part because it is the steepness that determines when a wave will break. Typical waves break when the steepness reaches about 1/10 (height equal to one tenth of the length), although they will appear menacing and steep when they have built to just (1/18)th of the length or so. The face of individual waves, however, will be steeper than this ratio implies because the front face of a wind wave is cusp-shaped, not a straight descent from crest to next trough ahead. Wave steepness is dramatically increased when the waves are running against a current (wind and current opposite direction). Wave statistics including steepness are given in G238 on sea state. See G114 for a graph relating wave steepness and current. G149 shows how to use this information to judge current flow. See ART-20 on wave steepness.

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