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Breaking Waves and the Breaking Wave Environment
Why Do Waves Break?
Waves break as they encounter shallow water because the "bottom" portion of the wave hits either the nearshore shelf or reef while the "top" portion of the wave continues to move forward and ultimately steepens and falls over. The condition for wave breaking is when a wave reaches the shore and enters water that is approximately 1.3 times as deep as the wave is high. At this depth the wave becomes unstable and crest is thrown forward into what we observe as white water and turbulence. The reason a wave breaks is that the wave becomes overly steep, particularly at the peak of its crest. This over steepening is due to the water particles in the wave crest exceeding the velocity of the wave form. In this situation the the crest surges ahead resulting in the breaking wave.
Three "Types" of Breaking Waves
The Gulf of Mexico and specifically Texas barrier island beaches are sculpted by spilling breakers and the currents generated by these waves. Spilling breakers are waves that gradually peak until the crest becomes unstable and cascades down in bubble and foam known to most as "white water". Plunging breakers describes a wave wher ethe wave face becomes vertical and then curls over plunging forward and downward as an intact mass of water (such waves are generally observed on the Hawaiian and California coasts). Surging breakers look like they are going to plunge but then the base of the wave runs up the beach face resulting in the collapse and disappearance of the crest.
Surf Zone - nearshore area in which bore-like waves occur following wave breaking. This portion of the nearshore extends from the inner breakers shoreward to the swash zone.
Swash Zone - nearshore area of the beach face that is intermittently covered by run-up of the wave swash and then exposed by the backwash.
Incident Wave - Waves approaching the shoreline at angles rather than perpendicular to the shoreline.
Texas A&M University-Corpus Christi