Beach cusps

Beach cusps are shoreline formations made up of various grades of sediment in an arc pattern.

They nearly always occur in a regular pattern with cusps of equal size and spacing appearing along stretches of the shoreline.

The crashing of the wave into the cusps slows its velocity, causing coarser sediment to fall out of suspension and be deposited on the horns.

The movement patterns of these waves are fixed and so can be defined as two regions of interest, the nodal and antinodal points.

The antinodal point is where all the movement takes place as the water rises and falls, creating a series of peaks and troughs.

The theory has two main points that seek to explain the formation of regularly spaced beach cusps.

Areas of higher relief slow the water down and sediment is deposited on top of them, which increases their impact.

In recent years, there has been considerable debate about whether beach cusp formation is associated with the presence of standing edge waves (standing edge wave theory), results from self-organizing feedback between changing topography and swash motion (self-organization theory) or is attributable to a number of other less popular mechanisms.

The National Centre of Scientific Research in France, collected a large amount of data from laboratory experiments and field studies, published over the last 50 years to test the predictions of the two main cusp forming hypotheses.

[2] The Naval Research Laboratory, the corporate research laboratory for the United States Navy and Marine Corps carried out nearly nine years of video imagery from Duck, North Carolina to determine the timing of cusp formation (to within half a day) and the distances separating consecutive cusp horns (to within half a metre).

Supplementary data provided by nearshore instrumentation and surveying vehicles was used to document the environmental conditions during cusp development.