Scale effects arise due to force ratios which are not identical between a model and its real-world prototype and result in deviations between the up-scaled model and prototype observations. This review article considers mechanical, Froude and Reynolds model–prototype similarities, describes scale effects for typical hydraulic flow phenomena and discusses how scale effects are avoided, compensated or corrected. Four approaches are addressed to obtain model–prototype similarity, to quantify scale effects and to define limiting criteria under which they can be neglected. These are inspectional analysis, dimensional analysis, calibration and scale series, which are applied to landslide generated impulse waves. Tables include both limiting criteria to avoid significant scale effects and typical scales of physical hydraulic engineering models for a wide variety of hydraulic flow phenomena. The article further shows why it is challenging to model sediment transport and distensible structures in a physical hydraulic model without significant scale effects. Possible future research directions are finally suggested.

Subaerial landslide generated impulse waves were investigated in a prismatic wave channel based on Froude similitude and granular slide material. The tests included the following seven governing parameters: still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter. All governing parameters, except for the grain diameter with a negligible effect, are included in the impulse product parameter P allowing for a simple application. Empirical equations based on 211 experiments for all relevant wave features in practice including the maximum wave height, the maximum wave amplitude with its location and period in the slide impact zone, and both the wave height and amplitude decay and the period increase in the wave propagation zone are a simple function of P . The presented equations were validated with 223 runs resulting in improved goodness of fit. The limitations of the herein derived empirical equations are also highlighted. The wa...

Preliminary landslide–tsunami hazard assessment is commonly based on empirical equations derived from wave channel (2D) or wave basin (3D) experiments. The far-field wave in 2D can easily be an order of magnitude larger than in 3D. The present study systematically investigates the effect of the water body geometry on the wave characteristics in the near- and far-field. Subaerial landslide–tsunami tests were conducted relying upon both a 2D and a 3D physical model, undertaken with identical boundary conditions. The test parameters included two water depths, three rigid slides, as well as various slide release positions. Empirical equations for 3D offshore and laterally onshore wave properties are presented and compared with previous work. A direct comparison of the wave features reveals that the waves decay in 2D, 3D onshore and 3D offshore with x− 0.30, r− 0.67 and r− 1.0, where x (2D) and r (3D) describe the distance from the impact zone. In 2D four wave types are observed, whereas only the two least non-linear types were observed in 3D. This finding is further analysed with wavelet spectra. For a large slide Froude number F, relative slide thickness S and relative slide mass M, the 3D wave heights in the slide impact zone can be as large as in 2D. However, for small F, S and M, the 3D waves are considerably smaller both in the near- and far-field. A novel method is presented and validated to transform data from 2D studies to 3D. This method may have favourable implications on preliminary landslide–tsunami hazard assessment