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
already recognized snow avalanche runout zone, and the northeastern part is the most exposed
one.
During field investigations, the presence of large boulders far down the northernmost path
drew attention as no record reported such a long runout event. According to the analysis of
aerial photographs, the position of these boulders was related to snow avalanche activities
from the above path. The application of the α/β relationship in this area confirms that snow
avalanches reaching close by the river might be expected from the north westernmost path.
However, as covering hay fields, the original location of the boulders cannot be confirmed
with precision, but still provides an indication of the extension of the snow avalanche. The
longest recorded snow avalanche in the area, which occurred in January 2005, is not the
longest expected one. The Figure 4B therefore emphasizes that buildings in Hnífsdalur are
mostly located within the runout zones of potentially large events.
Figure 4 The extent of known events and the results of the α/β relationship in
Patreksfjörður (A) and Hnífsdalur (B).
4. DISCUSSION AND CONSLUSION
We have tested a new geomorphic approach based on known proportional relationships
between topographic parameters to delimitate snow avalanche hazard zones into inhabited
areas. The results obtained in two areas, where snow avalanche records are partly reliable or
where field indicators exist, show the capability of the empirical approach to be transferred.
Here, the crucial parameters are determined in the field. Moreover, the obtained delineation is
obtained through the identification of boulders deposited by snow avalanche and not by the
actual runout of the snow avalanche (i.e. the extent of the snow itself). Such results are of
Decaulne and others 135