AbstractThe morphological features of recurved sand spits were studied by selecting recurved sand spits in Namibia, Sandy Hook on the US east coast, and Graswarder spit in Germany. The elongation of a recurved spit was predicted using the BG model (a model for predicting three-dimensional beach changes based on Bagnold's concept). A recurved spit was formed in Case 1 when waves were incident at angles of 45° and -30° with a duration ratio of 0.85:0.15. The width of the recurved sand spit in Case 1 increased with the elongation of sand spit, and the overall shape became similar to the expanded bird wing, which well explains the configuration of a recuved sand spit formed in Namibia. In Case 2 when waves were obliquely incident at angles of 45° and -45° with the same duration ratio as in Case 1, a sand spit extended straight, which well resembles Graswarder spit in Germany.
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