Numerical Modelling and Validation for Three-dimensional Boulder Transport during Tsunami

Coastal boulders are usually the results of extreme wave events, and many imply tsunami events, which can cause significant damage and dramatic coastline changes. However, the interpretation of boulder accumulations still remains challenging. Recent boulder transport studies primarily focus on steady flow conditions with discontinuous simulations. Time-varying characteristics of tsunami waves and topography have been ignored in previous researches. To explore the boulder transport mechanisms under different boundary conditions and topographies, we establish a new sediment transport model that includes three different transport modes (sliding, suspension, and rolling) and tracks the boulder movement processes in actual topography and flow conditions. Using the field observation distribution of boulders during Chile 2010 Tsunami at Bucalemu, we validate the stability and accuracy of the boulder transport model and invert the potential hydrodynamic properties of the tsunami. The results show that our model can effectively simulate and predict the tsunami boulder transport hazard and hydrodynamic characteristics. The initiation and transport of boulders in interaction with various geophysical flows, including tsunamis, is essential for understanding geophysical flows dynamics, assessing natural hazards, and also for interpreting sedimentary evidence.