FIELD OBSERVATION AND NUMERICAL SIMULATION OF BARRIER ISLAND FORMATION AS RESULT OF ELONGATION OF SAND SPIT AND ITS ATTACHMENT TO OPPOSITE SHORE

An artificial mound was produced from dredged materials containing sand and gravel in the Nakatsu tidal flat facing the Suo-nada Sea, and this artificial mound served as a supply source of sediment for the development of a barrier island. A sand spit extended from this mound in an extremely shallow sea and attached to the opposite shore, resulting in the formation of a barrier island. The planar changes in the sand spit were investigated using aerial photographs. Observations were compared with the results of a numerical simulation regarding the formation of a barrier island on a sloping bed with a 1/40 slope using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept). The observed change in the barrier island and the calculated results were in good agreement.