BEACH CUSPS AS SELF-ORGANIZED PATTERNS

Computer simulations of flow and sediment transport in the swash zone on a beach demonstrate that a model that couples local flow accelerati on and alongshore surface gradient is sufficient to produce uniformly spaced beach cusps. The characteristics of the simulated cusps and the conditions under which they form are in reasonable agreement with obs ervations of natural cusps. The self-organization mechanism in the mod el is incompatible with an accepted model in which standing alongshore waves drive the regular pattern of erosion and deposition that gives rise to beach cusps. Because the models make similar predictions, it i s concluded that currently available observational data are insufficie nt for discrimination between them.