17 Aug 2021

17 Aug 2021

Review status: this preprint is currently under review for the journal NHESS.

Quantification of meteorological conditions for rockfall triggers in Central Europe

Katrin M. Nissen1, Stefan Rupp2, Thomas M. Kreuzer3, Björn Guse4, Bodo Damm2, and Uwe Ulbrich1 Katrin M. Nissen et al.
  • 1Institute for Meteorology, Freie Universität Berlin, Berlin, Germany
  • 2Institute for Applied Physical Geography, University of Vechta, Vechta, Germany
  • 3Institute for Geography and Geology, University of Würzburg, Würzburg, Germany
  • 4GFZ, German Research Centre for Geoscience, Potsdam, Germany

Abstract. A rockfall dataset for Germany is analysed with the objective of identifying the meteorological and hydrological (pre-) conditions that change the probability for such events in Central Europe. The factors investigated in the analysis are precipitation amount and intensity, freeze-thawing cycles as well as sub-surface moisture. As there is no suitable observational dataset for all relevant sub-surface moisture types (e.g. water in rock pores and cleft water) available, simulated soil moisture and parameterised pore water are tested as substitutes. The potential triggering factors were analysed both for the day of the event as well as for the days leading up to the event.

It is found that the most important factor influencing rockfall probability in the research area is precipitation amount at the day of the event but the water content of the ground on that day and freeze-thawing cycles in the days prior to the event also influence the hazard probability. Comparing results with simulated soil moisture and parameterised pore water revealed that precipitation minus potential evaporation evaluated for a weekly period performs well as a proxy for the relevant sub-surface moisture types.

A logistic regression model was built, which considers individual potential triggering factors as well as their interactions. Using this model the effects of meteorological conditions on rockfall probability in the Central European low mountain ranges can be quantified. The model suggests that precipitation is most efficient, when the moisture content of the ground is high. An increase of daily precipitation from its local 50th percentile to its 90th percentile approximately doubles the probability for a rockfall event under median sub-surface moisture conditions. When the moisture content of the ground is at its 95th percentile the same increase in precipitation leads to a four-fold increase in rockfall probability. The occurrence of a freeze-thaw cycle in the preceding days can further increase the rockfall hazard. The most critical combination can be expected in the winter season after a freeze-thaw transition which is followed by a day with high precipitation amounts and takes place in a region preconditioned by a high level of sub-surface moisture.

Katrin M. Nissen et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-243', Anonymous Referee #1, 27 Aug 2021 reply
    • AC1: 'Reply on RC1', Katrin Nissen, 17 Sep 2021 reply

Katrin M. Nissen et al.

Katrin M. Nissen et al.


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Short summary
A statistical model is introduced which quantifies the influence of individual potential triggering factors and their interactions on rockfall probability in Central Europe. The most important factor is daily precipitation, which is most effective if sub-surface moisture levels are high. Freeze-thaw cycle in the preceding days can further increase the rockfall hazard. The model can be applied to climate simulations in order to investigate the effect of climate change on rockfall probability.