Impact of quality of input data on rockfall hazard zoning

This contribution summarizes existing challenges in the implementation of a standardised procedure for natural hazard risk analysis and zoning in the Alps. The discussion focuses on (i) the impact of data acquisition strategies on the quality of input data, (ii) the applicability of different 3D rock fall simulation models for hazard zoning in different topographic and geologic environments, (iii) the definition of thresholds for hazard zoning, and (iv) the cartographic representation of the results.

The evaluation of the applicability of the model results bases on the model sensitivity to the scale-dependent accuracy of input data and on the quality of the simulated travel distances (e.g., reach probabilities) and dynamics (e.g., energies, passing heights, velocities).

Depending on the source information and the method/technique used to conduct the survey, the content and detail of the collected data and simulation results can vary significantly. Calibration and validation of simulation results is usually performed using information on the geographic position of mapped rockfall boulders and/or historical rockfall events by archive research. For the latter, there is often no size specification available. To define reproducible threshold values for hazard zoning (i.e., reach probabilities) and to transfer them as a standard to other study areas, the model input data (e.g., roughness, damping) and calibration/validation data should be clearly indicated and published.

A further very important step is the joined cartographic presentation of the results of both, the simulation results and the field mapping. Such combination of results issued from different approaches forms the basis for the final hazard zoning. Supplementing ÖNORM rules with guidelines explaining in more detail the different mapping strategies/techniques and the model decisions would be very useful for the end users.