Swash Oscillations in a Microtidal Dissipative Beach

This paper evaluates the relationship between gravity and infragravity energy with swash oscillations as well as the model's ability to reproduce the transformation of the wave as it approaches the shore on a dissipative beach. For this purpose, numerical experiments were conducted in a dissipative beach from Cartagena, Colombia. Mean free surface measurements were carried out for 2 days in February 2014 by installing a cross-shore array of pressure sensors, as well as a Fourier analysis from these measurements to identify frequency components that characterize the waves and the energy associated with them. To implement the numerical modelling, the SWASH model (The Simulation WAves till Shore is a numerical model that resolves nonlinear shallow-water equations) was set up by using the bathymetric profile of Bocagrande Beach obtained during the field campaign. The results of this numerical modelling enabled the study of the infragravity energy growth mechanism and the evolution of gravity energy as the wave approaches the shore, as well as the relationship between gravity and infragravity energy with swash oscillations. Overall, the results show that the model is able to reproduce the significant wave height and significant wave height associated with infragravity energy; moreover, the model is able to accurately describe processes of energy dissipation and energy transfer. Furthermore, through a spectral analysis applied to the swash oscillations time series it was possible to find that saturation occurs at low-frequency significant swash height and high-frequency significant swash height as the significant wave height increases, since its increase is not linear with respect to the signficant wave height incident.