Cell circulation is the term used to describe currents within the surf zone that are
not parallel to the shore. The existence of cell circulations is evidenced by rip currents
(a common hazard for swimmers!) Rip currents are a seaward return flow of water
concentrated at points along the beach. They are caused by a longshore variation of
wave height and hence set-up which provides the necessary hydraulic head to drive
them. The longshore variation of wave height can be caused either by refraction
effects or by the presence of edge waves. Under the latter circumstances a regular
pattern of cell circulations and rip currents will exist and beach cusps may be formed.
The interested reader is referred to Komar (1976) and Huntley et al. (1993) for further
details.