A fundamental quantity affecting landslide impact is its size: we ask how size might be known in advance of failure, and explore conditions under which there might be useful answers. The regional answer comes from probabilistic landslide hazard analysis. We approach the local problem by discussing forms that answers might have taken in some historical New Zealand landslides. Edifice shape seems more important than specific, weakest defects in determining release surfaces, and so the probability-density distribution of potential failure sizes at a site is estimable from topography, general knowledge of rock-mass characteristics, and the probability-density distributions of potential triggers. To understand and predict how far a landslide of known size will travel, and what its internal structure will be, we discuss dynamic grain fragmentation and its role in rock-avalanche and block-slide motion. We then examine how fragmentation affects the stability of rock-avalanche and block-slide dams.
Davies, T. R., & McSaveney, M. J. (2011). Rock-Avalanche Size and Runout – Implications for Landslide Dams (pp. 441–462). https://doi.org/10.1007/978-3-642-04764-0_17