Empirical quantification of rockfall reach probability: objective determination of appropriate topographic descriptor

TL;DR

This study evaluates various topographic descriptors derived from rockfall paths to improve the empirical estimation of rockfall reach probability, focusing on the most effective metrics for hazard assessment.

Contribution

It identifies the most appropriate topographic descriptors, such as curvilinear length and area under the path, for better empirical rockfall reach probability estimation.

Findings

Curvilinear length of the propagation path improves reach probability estimates.

Area under the propagation path enhances hazard prediction accuracy.

Descriptors computed along the final portion of the path are particularly effective.

Abstract

For rockfall hazard assessment on areas more than several km2 in size, the quantification of runout probability is usually done empirically. Classical methods use statistical distributions of reach or energy angles derived from rockfall databases. However, other topographic descriptors can be derived from the topographic profiles along the rockfall path. Using a database of more than 4,000 profiles of rockfall paths, we determine which topographic descriptors are most appropriate for reach probability estimation, by comparing their statistical distributions for rockfall stopping points, and for points the rocks overtook. We show that the curvilinear length of the propagation path, and the area under the propagation path can improve propagation estimations, especially when they are computed only along the final portion of the propagation path. This is illustrated by comparing an experimental distribution of rockfall stopping points to the estimated distributions.