A numerical investigation of tsunamis impacting dams

Landslides, rockfalls, and iceberg calving impacting into a water body generate large landslide-tsunamis posing a serious hazard in lakes and reservoirs. These waves can impact and even overtop dams as in the 1963 Vajont disaster in Italy. However, estimating the effects of tsunamis on dams, e.g. pressures and forces, and 3D effects is challenging. An accurate prediction of these effects is also important for a range of coastal and offshore applications. The present study focuses on the numerical modelling of landslide-tsunamis impacting dams with the open source toolbox solids4foam. After a validation with theoretical, experimental, and numerical results, 5th order Stokes, cnoidal, and solitary waves were simulated in 72 2D experiments with dams of steep to vertical inclinations. The wave loading on dams was found to be in agreement with predictions based on an existing empirical approach, significantly expanding its limited validation conditions. New empirical equations are suggested to predict the wave run-up height together with the overtopping volume and depth. These address the cases where no empirical equations are available or existing equations result in large deviations from the numerical results. Novel insight in the dynamic pressure is provided, supported by new semi-empirical equations. Further, simulations in 3D were performed to quantify the effects of the dam curvature and asymmetrical wave impact angles. Both effects combined induce an increase in the run-up height at dam flanks of up to 32%. Such findings support the design of dams and tsunami hazard assessment.