Physical and numerical modeling of landslide-generated wave runup on steep slopes
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Landslides generate waves when they fall into water, and these waves can be major hazards where they interact with coastlines and runup slopes on land. In this thesis, physical and numerical models of landslide-generated waves on steep slopes were constructed and used to develop a deeper understanding of the runup process. First, a physical model was developed to investigate landslide wave runup. Impulse waves were generated in a series of laboratory flume experiments by releasing a range of different slide source volumes of highly mobile slide material (water) into different reservoir depths, to observe the runup of waves that are breaking and non-breaking on steep slopes ranging from 25° to 45°. The maximum runup and the cross-slope variability in runup of each wave was captured using hydrochromic paint, which changes colour on contact with water, and this novel technique was developed as part of this thesis. The experimental results indicate that in the near-field the runup of breaking waves is dependent on the wave amplitude relative to the water depth, and is nearly independent of the slope angle. The observations, combined with runup data from previous studies, are used to develop a new semi-empirical equation for runup of breaking and non-breaking waves. The formulation is valid over an extended range of relative wave amplitudes, relevant for near-field runup that has been documented in major field cases. The experimental observations provide, for the first time, a comprehensive dataset of near-field runup for breaking and non-breaking impulse waves. Second, a high-resolution phase resolving numerical model was applied to investigate landslide wave runup. The non-hydrostatic SWASH model was used to simulate wave propagation and runup corresponding to the laboratory experiments. The model adequately resolves the propagation and interaction of the incident wave with the slope but does not capture the very thin and fast fluid flow that reaches the maximum runup in the experiments, especially for cases when the waves are breaking. In future, the benchmark experimental dataset on impulse wave runup collected in this study can be used to validate other types of numerical models.