2022 Volume 78 Issue 1 Pages 29-41
The beach topography is subject to seasonal variations, especially in the swash zone, where sediment movement is pronounced and the beach face slope and sediment grain size are constantly changing, resulting in a state of dynamic equilibrium. In this study, the constructal law, which states that the flow system in nature behaves in an efficient manner, was applied to the sediment transport in the swash zone. The dynamic relationship between sediment grain size and beach face slope in the dissipative and reflective beaches was analyzed using the energy model and the Shields number model. There was no difference among the models, and the beach face slope became slower as the wave height increased, similar to the characteristics of the field beaches. The relationships between sediment particle size and beach face slope in the inner bay, open sea and coral reef beaches were explained.
As an application of the analytical solution, the changes in sediment grain size and beach face slope with the change of waves on an artificial beach are clarified, which is useful for the maintenance and management of the beach. The applicability of the solution to the evaluation method of shoreline retreat due to sea level rise by Bruun’s rule is also discussed.