**Author details**

lake causes downward longshore sand transport, and vice versa, when waves are incident from the lower half. Without an island, net sand transport at point A is 0 because of the symmetricity of the closed water body. With an island, however, the area of the water body in the lower half decreases than that in the upper half, resulting in weaker wave action. As a result, the direction of the net sand transport fluxes at points **a** and **b** became downward, enhancing sand transport from the upper half to the lower half, resulting in erosion in the upper half.

**Figure 24.** Mean sand transport flux averaged over 1000 steps in Cases 5 and 7.

**Figure 23.** Lakeshore changes around a sandy island in lake (Case 8).

68 Applications in Water Systems Management and Modeling

Takaaki Uda1 , Masumi Serizawa2 \* and Shiho Miyahara2

\*Address all correspondence to: coastseri@nifty.com

