Model for Predicting Topographic Changes of Beaches Composed of Sand of Mixed Grain Sizes Under Compound Action of Waves and Wind

On a coast composed of sand of mixed grain sizes and affected by strong wind, fine and medium-size sand is selectively transported inland as Aeolian sand, leaving coarse sand and gravel on the foreshore. In this study, a model for predicting topographic changes of beaches composed of sand of mixed grain sizes was proposed, taking the effects of not only waves but also wind into account. To verify the validity of the model, a model calculation was first carried out for a coast with a wave-shelter zone produced by the construction of an offshore breakwater, and then the model was applied to the Inage coast located in Tokyo Bay. On the Inage coast, beach nourishment using white sand imported from Western Australia was conducted. After the beach nourishment, it was observed that white sand was selectively deposited on the backshore, whereas gravel was left behind near the shoreline. The calculation results were in good agreement with the observation results on the Inage coast, and the effectiveness of the model was confirmed.