Self-Organizing of Waves and Sandy Bottom Relief—Laboratory Experiments

Many studies suggest that, as waves propagate toward the shore, mutual adaptation (self-organization) occurs between the wave transformation and the bottom relief. However, the details of this process are unknown. Is nonlinear transformation or wave breaking the primary factor influencing bottom relief deformation? The main goal of this study is to assess the impact of nonlinear wave transformation on bottom relief changes and to identify the key patterns of mutual adaptation between bottom topography and waves. A specialized laboratory experiment was conducted for this purpose. Based on an analysis of the evolution of wave spectra, changes in wave asymmetry, phase shift between harmonics and bottom relief deformations, it was revealed that self-organization occurs primarily due to the nonlinear properties of wave transformation. The nonlinear wave transformation scenario (the spatial evolution of the amplitudes of nonlinear wave harmonics toward the shore) determines the positions of the main minima and maxima of the first and second harmonic amplitudes, corresponding to sediment flow divergence points, which are maintained throughout the period of constant wave action. Wave breaking does not change this scenario, but it does affect the absolute values of the amplitudes and biphases, accelerating bottom change.