**5.1. Formation of barrier island on flat shallow seabed**

Given the same initial topography and wave conditions as those in the experiment (regular waves with *H*0' = 4.6 cm and *T* = 1.27 s obliquely incident to the model beach with an angle of 20), the beach changes after 8 hr were predicted. The depth of closure was given by *hc* = 2.5*H* (*H*: wave height at a local point). The berm height was assumed to be 5 cm, and the angles of the equilibrium slope and repose slope were set as 1/5 and 1/2, respectively, on the basis of the experimental results. The calculation domain was divided by *x* = *y* = 20 cm intervals in the cross-shore and longshore directions, respectively, and the calculation for up to 8 hr (8×104 steps) was carried out using time intervals of *t* = 1×10-3 hr. Table 1 shows the calculation conditions.
