Benchmarking and adapting the rockfall energy line method for rockfall hazard assessment

Rockfall runout and energy dissipation are controlled by complex interactions between block characteristics and terrain properties, yet simplified approaches remain widely used for rockfall hazard assessments in the praxis. This contribution revisits the rockfall energy line method (also known as the Pauschalgefälle method), presenting its conceptual basis and an online implementation tool for estimation of rockfall velocities and kinetic energies along slope profiles. The method projects an idealised energy line from the rockfall release area to the distal margin of the deposit zone, comparable to the shadow angle approach, with modified slope angles used to approximate terrain resistance due to surface roughness and vegetation.

Despite its simplicity, the rockfall energy line method is commonly employed as a first-order estimate and plausibility check in rockfall hazard assessments. Here, we evaluate the method against data from controlled, real-world rockfall experiments and examine its performance relative to advanced numerical rockfall models. The comparison illustrates how this simplified energy-based approach can complement process-based simulations, particularly where field data are limited.

Our benchmarking highlights some limitations of the current rockfall energy line method, particularly for large, idealised blocks travelling over smooth alpine meadow terrain. Based on these findings, we propose practical adaptations to the method that improve its applicability to extreme rockfall scenarios and provide guidance for its appropriate use in rockfall hazard assessment for the praxis.