Editing Wind wave (section)

==Breaking==
[[File:Big wave breaking in Santa Cruz.jpg|thumb|Large wave breaking]]
[[File:Giant ocean wave.jpg|thumb|{{center|Giant ocean wave}}]]
{{see also|Surf wave|Breaking wave|Iribarren number}}

Some waves undergo a [[phenomenon]] called "breaking".<ref>{{Cite book|url=https://books.google.com/books?id=E5F8KiuSVjAC&q=Some+waves+undergo+a+phenomenon+called+%22breaking%22.&pg=PA319|title=Advances in Robotics and Virtual Reality|last1=Gulrez|first1=Tauseef|last2=Hassanien|first2=Aboul Ella|date=2011-11-13|publisher=Springer Science & Business Media|isbn=9783642233630|language=en}}</ref> A [[breaking wave]] is one whose base can no longer support its top, causing it to collapse. A wave breaks when it runs into [[Waves and shallow water|shallow water]], or when two wave systems oppose and combine forces. When the slope, or steepness ratio, of a wave, is too great, breaking is inevitable.

Individual waves in deep water break when the wave steepness—the [[ratio]] of the [[wave height]] ''H'' to the [[wavelength]] ''λ''—exceeds about 0.17, so for ''H''&nbsp;>&nbsp;0.17&nbsp;''λ''. In shallow water, with the water depth small compared to the wavelength, the individual waves break when their wave height ''H'' is larger than 0.8 times the water depth ''h'', that is ''H''&nbsp;>&nbsp;0.8&nbsp;''h''.<ref>{{Cite book |author= R.J. Dean and R.A. Dalrymple |title=Coastal processes with engineering applications |year=2002 |publisher=Cambridge University Press |isbn=978-0-521-60275-4 }} p. 96–97.</ref> Waves can also break if the wind grows strong enough to blow the crest off the base of the wave.

In shallow water, the base of the wave is decelerated by drag on the seabed. As a result, the upper parts will propagate at a higher velocity than the base and the leading face of the crest will become steeper and the trailing face flatter. This may be exaggerated to the extent that the leading face forms a barrel profile, with the crest falling forward and down as it extends over the air ahead of the wave.

Three main types of breaking waves are identified by [[surfer]]s or [[Surf lifesaving|surf lifesavers]]. Their varying characteristics make them more or less suitable for surfing and present different dangers.
# Spilling, or rolling: these are the safest waves on which to surf. They can be found in most areas with relatively flat shorelines. They are the most common type of shorebreak. The deceleration of the wave base is gradual, and the velocity of the upper parts does not differ much with height. Breaking occurs mainly when the steepness ratio exceeds the stability limit.
# Plunging, or dumping: these break suddenly and can "dump" swimmers—pushing them to the bottom with great force. These are the preferred waves for experienced surfers. Strong offshore winds and long wave periods can cause dumpers. They are often found where there is a sudden rise in the seafloor, such as a reef or sandbar. Deceleration of the wave base is sufficient to cause upward acceleration and a significant forward velocity excess of the upper part of the crest. The peak rises and overtakes the forward face, forming a "barrel" or "tube" as it collapses.
# Surging: these may never actually break as they approach the water's edge, as the water below them is very deep. They tend to form on steep shorelines. These waves can knock swimmers over and drag them back into deeper water. 
When the shoreline is near vertical, waves do not break but are reflected. Most of the energy is retained in the wave as it returns to seaward. Interference patterns are caused by superposition of the incident and reflected waves, and the superposition may cause localized instability when peaks cross, and these peaks may break due to instability. (see also [[Clapotis|clapotic waves]])