Mountain forests play an important role in the protection against rockfall events. Within the Interreg Alpine Space
project RockTheAlps we focus on how the protection effect can be quantified, allowing to establish a rockfall risk
reduction (RRR) index for mountain forests. This index equals a dimensionless reduction factor of the total travel
angle, defined by the energy line of the rockfall event. The final objective of this study is therefore to develop a
toolbox called TORRID that allows i) to identify and map forests that contribute to RRR in the Alpine space ii),
to define optimal forest characteristics for an efficient RRR and iii), to be easily combined with existing runout
simulations models of rockfall events based on a simple 1d energyline approach. First of all, the most significant
forest parameters were compiled through literature research and could be defined as mean stand density [N=ha],
basal area of living trunks [m2=ha], basal area of dead trunks [m2=ha], ratio of coniferous/broadleaved trees [-],
proportion of shrub forest originating from coppice (only if broadleaved) [%], proportion of shrub forest (also
Pinus mugo) [%], proportion of coppice with standards [%], proportion of high forest [%] and amount of lying tree
(alive or dead) [m3=ha]. The primarily aim was to create a short list of parameters, which is easy employable for
practitioners recording rockfall data. Another perspective was to get the maximum of possible data with the most
meaningful information output to analyze. In a first step we compiled observation data of historic rockfall events
in Austria as well as the corresponding forest parameters. The
