Swash hydrodynamic modelling using a tri-dimensional model: CROCO

Abstract

The swash zone is one the most dynamic regions in the nearshore. During storms the beach response (erosion and recovery) is strongly controlled by the swash zone and for this reason it is crucial to acquire field data to and develop new modelling solutions to improve the forecast of the processes in this zone. New remote sensing techniques, such as 2D Lidar, that can measure swash hydro- and morphodynamics provide extremely valuable observations to develop and validate numerical models. In the present work a novel dataset of swash hydrodynamic observations (performed by a 2D Lidar) are used to test the performance of a new non-hydrostatic tri-dimensional numerical model (CROCO) to predict wave transformation and swash motions on a sandy beach with a low tide terrace (Nha Trang, Vietnam). An high resolution grid was setup, covering the entire swash zone and the inner surf zone, and 2 types of simulations were performed with energetic waves and mild wave conditions. Comparisons between CROCO and 2D Lidar indicate that despite some differences between individual waves characteristics (length of swash excursions and durations) in the overall the model show skills to predict extreme runup statistics (e.g., R2% or R10%) with very high level of accuracy,