Self-organization
Self-organization
This theory was initially dismissed due to complications with it but by using more advanced computer simulations, it has been developed to the point where it now provides a reasonable alternative to the standing edge wave theory. The theory has two main points that seek to explain the formation of regularly spaced beach cusps.
The first is that positive feedback between the morphology of the beach and the flow of the water creates relief patterns. On a flat beach, surface areas will develop with a slightly lower relief than their surroundings. Areas with lower relief attract and accelerate water particles, which means they have more energy and the area is eroded further. Through positive feedback, the area becomes more and more eroded, and this creates the embayment. The development of these areas of lower relief causes mean beach level to be lowered and so areas that were initially on the level are now below the average and as such, are now areas of higher relief. Areas of higher relief slow the water down and sediment is deposited on top of them, which increases their impact. This creates the horns.
The uniform spacing of cusps is caused by the communication of surface gradients along the beach by the smoothing of the beach surface as the beach tries to rearrange itself to reduce variations in the plane.
The second main point about the regular spacing of cusps is that negative feedback will decrease the amount of net erosion and deposition within a well-formed cusp. As the wave strikes the beach, it will first come into contact with the cusp horns, which will slow the water down. This causes it to lose energy and some of the heavier sediment that it is carrying will be deposited. The loss of this sediment, however, gives the water extra energy and it uses this to remove sediment from the embayment on the backwash.
The problem with this theory is that this method of cusp formation would take time and if you were observing their formation, then you would see a number of random cusps form along the beach, which then slowly spread along the shore as they even out in size, with small cusps joining together and larger cusps being separated in two. But in the field, cusps form a regular pattern almost instantly and they all appear at the same time.
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