Data-Driven and Theoretical Beach Equilibrium Profiles: Implications and Consequences

Abstract

This paper presents a concept of data-driven beach equilibrium profiles of cross-shore seabed records from the coastal station of Instytut Budownictwa Wodnego Polskiej Akademii Nauk at Lubiatowo, Poland, where multiple longshore bars are present. Data-driven equilibrium profiles are the monotonic trends of cross-shore seabed profiles. They were extracted using the empirical mode decomposition method. They retain general properties of Dean profiles, i.e., the Dean coefficients fitted to raw profiles are practically identical to those fitted to their trends. The monotonic property of trends allows for the introduction of cross-shore variable wave-energy dissipation rates, which can be compared with the constant Dean rates. This is the novel element of data-driven beach equilibrium profiles. Variable rates help indicate locations on a beach where wave-energy dissipation is intensive and produces erosion and where it is lower and generates deposition of sediment. In other words, variations of wave-energy dissipation can be assessed with greater precision from seabed configuration only, without any hydrodynamic information. Importantly, when a local wave climate is known, the associated depths of closure can be evaluated to determine the offshore limits, where the data-driven beach equilibrium profile concept can be valid.