A predictive relationship for the spacing of beach cusps in nature

Erosion/accretion patterns and multiple beach cusp systems on a meso-tidal, steeply-sloping beach

“…Sunamura (2004) developed a model based on the theoretical concepts that the extent of wave uprush flow divergence at a cusp horn is related to the cusp spacing, and that the flow path is affected by the grain size of beach sediment. He derived the following equation to predict cusp spacing:…”

“…Finally, Various numerical modelling efforts (e.g. Coco et al, 2001Coco et al, , 2003Sunamura, 2004;Dodd et al, 2008), together with laboratory experiments (e.g. Takeda et al, 1986;Aoki and Sunamura, 2000), have resulted in important insights being gained into the mechanisms of beach cusp formation, some of which are awaiting confirmation by field observations.…”

Observations of beach cusp evolution at Melbourne Beach, Florida, USA

“…Over the last 30 years, this rhythmic pattern has received a considerable amount of study. Largely, research has focused on the formation mechanisms underlying cuspate morphology in order to accurately describe relationships between hydrodynamic forcings and beach cusp spacing (Inman and Guza, 1982;Werner and Fink, 1993;Masselink, 1999;Coco et al, 1999, 2003, 2005Sunamura, 2004Dodd et al, 2008). These studies, relying predominantly on theoretical or numerical modeling, have shifted focus towards cusp initiation and away from characterization of cusp morphology.…”

“…However, Emery (1960) and Williams (1973) observe that the relationship is less significant on finer-grained beaches and Coco et al (2003) saw no difference between horns and embayments. Given that grain size can also be important in determining prominence and spacing of the features (Sunamura, 2004) more observations are needed to see if (and how) sediment is sorted during beach cusp growth.…”

Relation between beachface morphology and wave climate at Trafalgar beach (Cádiz, Spain)

“…Masselink et al (2004) also focused on the relation between the offshore wave forcing and the formation of the rhythmic topography concluding that cusps are formed under calm conditions and destroyed by the larger energetic conditions. Sunamura (2004) discussed the importance of the longitudinal distribution of the wave height in the initial cusp formation. Nevertheless, although beach cusp formation and evolution have been intensively studied, there are no clear relationships between their presence (or absence) and the wave forcing.…”