Rhythmic Patterns

Beaches are seldom straight or smoothly curved in the longshore direction. Instead, they commonly include seaward projections of sediment, termed cusps, or embayments locally cut into the shore. Such features may be isolated, but more often occur in groups of alternating cusps and embayments that have a fairly regular spacing; they are then referred to as rhythmic patterns. There are several recognized types of rhythmic patterns, including beach cusps, sand waves, and giant cusps (Komar 1998).

A wide range of spacings of rhythmic patterns can be found on beaches. Along the shores of ponds and small lakes the spacings between adjacent cusps may vary from less than 10 cm to 1 m. On ocean beaches with small waves, the spacing may be on the order of 2 m, while those built by large storm waves may be 50 m or more. Other rhythmic patterns, sand waves and giant cusps, have still larger spacings, typically ranging from 150 to 1500 m, but with most being between 500 and 750 m, with the cusps...