Rockfall hazard zoning is usually achieved using a qualitative estimate of
hazard, and not an absolute scale. In Switzerland, danger maps, which
correspond to a hazard zoning depending on the intensity of the considered
phenomenon (e.g. kinetic energy for rockfalls), are replacing hazard maps.
Basically, the danger grows with the mean frequency and with the intensity
of the rockfall. This principle based on intensity thresholds may also be
applied to other intensity threshold values than those used in Switzerland
for rockfall hazard zoning method, i.e. danger mapping.
In this paper, we explore the effect of slope geometry and rockfall
frequency on the rockfall hazard zoning. First, the transition from 2D
zoning to 3D zoning based on rockfall trajectory simulation is examined;
then, its dependency on slope geometry is emphasized. The spatial extent of
hazard zones is examined, showing that limits may vary widely depending on
the rockfall frequency. This approach is especially dedicated to highly
populated regions, because the hazard zoning has to be very fine in order to
delineate the greatest possible territory containing acceptable risks.
|