The first scaled experiments to determine breaking wave impact modes and energies responsible for the transport of boulder clasts of O(100 t) positioned atop coastal cliff s were carried out at Ecole Centrale de Marseille (ECM) in February 2021. In the experiments, the influence of the breaking wave crest shape and of the energy contained in the breaking wave were investigated.

Breaking waves were created using dispersive focussing and the impact type and strength of the breaking wave was altered by perturbing the focus position and spectral energy. Detailed measurements of the local free surface, global free surface, and the reaction of the boulder were made. These measurements are 3-axis shock and steady accelerations from within the boulder model, boulder position and orientation, pressure on the impacting face of the boulder, subsurface particle image velocimetry, and a very-high speed camera.

The experiments were quite successful. James Steer (postdoctoral researcher) is going through all the data that was acquired during the two week experimental campaign.