Evaluating Hazard of Landslide-Induced Water Waves

Dimensional analysis of the landslide parameters which control dimensionless maximum wave amplitude, η_m/d, when slides impact with a water body, shows that dimensionless slide kinetic energy, E_k, is most important. Data from two site-specific hydraulic studies combine to produce a consistent data set and give a statistically significant linear regression equation of log (η_m/d) = -1.25 + 0.71 log (E_k), in which E_k = ρ_s lwhV² (2ρgd⁴)^-¹, l, w, h, ρ_s, and V are slide length width, thickness, density, and maximum velocity, ρ is water density, g is gravitational acceleration, η_m = maximum wave amplitude at a standard distance r/d≈4 directly in front of a slide, d = water depth at that site, and r = radial horizontal distance from the point of slide impact. The hydraulic model studies had scale factors of 1:120 and 1:300, with 0.4<h/d<0.8. Landslides were simulated by 1/18- 1/3 cu ft (0.002-0.005m³) triangular or tabular bags of metal or gravel, with toes initially above water level. η_m/d, back calculated from observed waves and wave run-ups for the 1958 Gilbert Inlet slide in Lituya Bay, Alaska, and the 1905 glacier fall in Disenchantment Bay, Alaska, are accurately predicted by the regression equation in the first case and conservatively predicted in the second.