Unravelling equilibrium shoreline response to waves and sea-level rise: Numerical modelling of laboratory experiments
Knowledge gaps in the physics of shoreline response to the combined action of waves and sea-level rise (SLR) make long-term shoreline projections uncertain. The lack of sufficiently long-term shoreline data partly hinders a better understanding of shoreline change driven by SLR. Thereby, existing formulations related to the equilibrium approach, which states that a beach profile shape equilibrates with its local wave and sea-level conditions, have serious limitations. Recent physical modelling studies provided data of beach profile evolution under changing sea levels in controlled laboratory settings. Here, we bring together and analyze laboratory data from three different physical modelling studies to better understand and predict shoreline response to SLR in the context of equilibrium concept. The data indicate a clear relationship among the analyzed variables, highlighting the importance of accounting for interactions between SLR and incident wave power. To further understand these interactions, and given the limited range of conditions tested in the laboratory, we implement a quasi-2D shoreline change model to generate additional synthetic data. We first calibrate and validate the model to emulate the existing laboratory experiments. The model reproduces multiple laboratory experiments that cover a range of settings, providing confidence in its accuracy. Further work will include the generation of synthetic data obtained by forcing the model with new combinations of SLR and wave conditions to better capture the dependency of shoreline recession on SLR and wave conditions.