(1) Crest of wave, wave crest: The highest part of a wave. (2) That part of the wave above still-water level. Crest lenght, sometimes called crest width, is the length of the wave crest, perpendcular to the wave movement.
Source http://www.kennisbank-waterbouw.nl/Glossary/printUK.php?subject=@хяр
(1)The highest stage or level of a flood wave as it passes a point. (2)The top of a dam, dike, spillway, or weir, to which water must rise before passing over the structure.
Source http://www.nws.noaa.gov/om/hod/SHManual/SHMan014_glossary.htmхяр
гребень
(1) top of a dam or spillway; (2) the highest elevation reached by flood waters.
Source John M. Sharp, Jr. 2007 Department of Geological Sciences Jackson School of Geosciences The University of Texas Austin, Texas, USA