The waves of the sea as they break on a shore or reef. On beaches, surf is formed between the breaker and swash zones. See S. H. Sweeny (2008) on the geography of surfing.
The surf similarity parameter is based on a consideration of the wave characteristics and the gradient of the beach (Battjes 1974) may be used to predicted breaker type via the formula:
where tan β is the gradient of the beach and the subscripts
b and
o indicate breaker and deep-water conditions respectively. Small values for ξ are attained when the beach has a gentle gradient and the incident wave field is characterized by a large wave height and a short wave length (or a short wave period). Large values of ξ are found when the beach is steep and the incident wave field is characterized by a small wave height and a long wave length (or a long wave period). Spilling breakers occur for ξ < 0.4; plunging breakers for ξ= 0.4 to 1; and surging breakers for ξ > 1 (Masselink in J. Holden 2012).