Computer simulations of megaripples in the nearshore

Megaripples (bedforms with heights of 20-40 cm and lengths of 1-5 m) occur frequently in the shallow surf zone. However, their relationship to the flow field is unclear. It has been suggested that self-organization is responsible for the formation of many different morphological patterns (eg, river meanders, sorted-patterned ground, beach cusps, wind ripples, eolian dunes). Each of these systems is nonlinear, dissipative and open to the environment, as is the surf zone. Thus, surf zone megaripples also may be good candidates for formation via self-organization. Werner (1995) assumed self-organization and successfully predicted eolian dune morphologies using computer simulations based on simple rules governing the motion of sediment. Here, a similar model is used that describes forcing by combined flows in the nearshore. Preliminary results look remarkably like observed morphologies measured during the SandyDuck Nearshore field experiment.