International Symposium on Mitigative Measures against Snow ...

<strong>International</strong> <strong>Symposium</strong> on Mitigative Measures against Snow Avalanches
Egilsstaðir, Iceland, March 11–14, 2008
3. APPLICATION OF TWO-DIMENSIONAL SIMULATIONS
3.1 Hazard zoning of settled areas
As mentioned earlier, the SAMOS model has been used in the hazard zoning process,
described by Jónasson and others (1999) and Arnalds and others (2004), for several Icelandic
villages since the year 2000. The two-dimensional simulation results have proved to be
valuable for showing the direction of the main avalanche tongues from the starting areas, in
particular the influence of ridges and gullies and to estimate the shortening of avalanche runout
due to lateral spreading . The use of the 2D run-out index scale and the parameter axis has
already been implemented to this process in a recent project (Jóhannesson and others, 2007).
Figure 3 Comparison of 1D and 2D run-out indices based on simulations with a modified
PCM flow-line model and samosAT, respectively.
As shown in Figure 3, the 1D and 2D run-out indices coincide in middle of the avalanche path
of Seljalandsdalur/Tungudalur, N-W Iceland, where it is rather unconfined and the flow-lines
are roughly parallel, whereas a difference is evident where the landscape is more complex.
This information can be useful when hazard zones are delineated and make it possible to
better consider the effect of ridges, gullies and curves in the path.
Hazard maps have already been issued for the most vulnerable villages of Iceland. The maps
are constantly reviewed, especially in connection to the construction of defence structures.
Furthermore, the avalanche hazard is yet to be assessed in many rural areas. Two-dimensional
avalanche simulations and 2D run-out indices will be of good use in that process since twodimensional
avalanche models can provide a good overview and comparison of avalanche
conditions from one place to another.
3.2 Hazard zoning of unsettled areas
The IMO is developing a methodology to be used for the hazard mapping of public ski areas
in Iceland. Two-dimensional avalanche simulations will be important for this work and a first
proposal of guidelines for systematic simulation for avalanche paths in Icelandic ski areas has
been issued (Gíslason, 2007). This methodology could possibly apply for other recreational
166 Application of two-dimensional avalanche model simulations at the IMO