Wave types and energy conversion of impulse waves generated by landslides into mountain reservoirs

Subaerial landslides sliding into shallow water are physically modeled in a three-dimensional wave basin. The generated impulse waves are highly nonlinear, and a large-scale splash zone is formed above the waves. Such impulse wave characteristics are different from those from landslides into deep water that are completely submerged after sliding. The recorded wave profiles included three wave types, namely nonlinear oscillatory wave, nonlinear transition wave and bore-like wave, mainly depending on the relative slide thickness and slide Froude number at impact. Bore-like waves were possible produced only by landslides into shallow water in three-dimensional experiments. The conversion rate of landslide kinetic energy at impact into the wave train energy is 1 to 18%. Energy conversion characteristics are compared with other two- and three-dimensional studies on landslide-generated waves and the results are discussed.

Model Test Research on the Propagation of Tsunamis and Their Interaction with Navigating Ships

The slope of a reservoir area is unstable and can be destroyed by natural disasters, such as strong earthquakes and rainstorms. Landslide bodies that enter the water and generate landslide surges pose serious safety risks to terminals, ships, and hydraulic structures in a reservoir area. After analyzing landslide data in a reservoir area, a series of comparative tests was carried out to investigate the propagation characteristics of landslide-induced tsunamis in channel reservoirs, and the changes in water level values at various monitoring points in the river channel after the landslides entered the water were explored. The effects of landslide width and thickness on the characteristics of landslide-induced tsunamis were analyzed. The main target was a fixed-velocity ship in landslide-swelling water. The complex nonlinear motion characteristics of the ship on the water were studied to determine the safe navigation range.

Physical modelling of tsunamis generated by three-dimensional deformable granular landslides on planar and conical island slopes

Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment.

On the characteristics of landslide tsunamis

This review presents modelling techniques and processes that govern landslide tsunami generation, with emphasis on tsunamis induced by fully submerged landslides. The analysis focuses on a set of representative examples in simplified geometries demonstrating the main kinematic landslide parameters influencing initial tsunami amplitudes and wavelengths. Scaling relations from laboratory experiments for subaerial landslide tsunamis are also briefly reviewed. It is found that the landslide acceleration determines the initial tsunami elevation for translational landslides, while the landslide velocity is more important for impulsive events such as rapid slumps and subaerial landslides. Retrogressive effects stretch the tsunami, and in certain cases produce enlarged amplitudes due to positive interference. In an example involving a deformable landslide, it is found that the landslide deformation has only a weak influence on tsunamigenesis. However, more research is needed to determine how landslide flow processes that involve strong deformation and long run-out determine tsunami generation.