**6. Discussion**

In general, when a detached breakwater or submerged breakwater is constructed on a coast composed of fine and medium-size sand, sand accumulates in the lee of the structure owing to the wave-sheltering effect, forming a salient behind the structure. Owing to this sand deposition effect, these structures have been widely used in Japan as a measure against beach erosion. However, the beach formed by this accretive effect of waves is also subject to wind action, resulting in a significant amount of windblown sand. On a sandy beach widened in the lee of the structure, therefore, the amount of sand blown to the hinterland is also increased, causing loss of foreshore sand. Accordingly, on such a coast, even though beach nourishment is carried out, nourishment sand is transported to the hinterland, devaluating the effect of beach nourishment, and causing another sand maintenance problem. When considering

*Numerical Simulation on Sand Accumulation behind Artificial Reefs and Enhancement… DOI: http://dx.doi.org/10.5772/intechopen.107014*

**Figure 24.**

*Calculation results in Case 4 after the removal of the artificial reefs. (a) Predicted topography in Case 4. (b) Topographic changes in Case 4 relative to initial topography.*

shore protection measures against beach erosion on a coast composed of fine and medium-size sand, the effect of windblown sand must be taken into account. In such a case, the present model can be useful for predicting future beach changes.
