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
Comprehensive snow net project Hafelekar/Innsbruck
Matthias Granig
Center for Snow and Avalanches, Avalanche and Torrent Control (WLV), Swarovskistraße 22a,
6130 Schwaz, AUSTRIA
e-mail: matthias.granig (at) die-wildbach.at
ABSTRACT
This paper gives information about the snow net project at the Hafelekar at 2250m a.s.l. above
Innsbruck/Austria performed by the Forest Technical Service for Avalanche and Torrent
Control (WLV) in cooperation with the Federal Forest Research Center (BFW) in Innsbruck.
For snow pack stabilisation in the avalanche starting zones principally two systems are
applied: snow bridges and snow nets. The construction of snow bridges is well established in
Austria. In contrast, snow net systems are used less extensively, because there are still some
uncertainties in the construction and the foundation of nets. Therefore, a test site at the
Hafelekar above Innsbruck was installed to analyse the different systems. Especially the
difference between the triangle net types and the rectangular net types was one of the major
points of interests. The WLV/BFW carried out extensive measurements of the forces in the
installed snow nets, in order to obtain information of the forces in the different net systems.
Additionally, tests with anchors and the analysis of materials in terms of corrosion protection
are ongoing and will help to estimate the durability of the different systems. These findings
from the test site at the Hafelekar should help to define an Austrian guideline for snow nets.
Keywords: avalanche protection, snow net, snow bridges
1. INTRODUCTION
The Forest Technical Service for Avalanche and Torrent Control (WLV) has been
constructing a large number of avalanche protection works in the avalanche starting zones for
more than fifty years. In Austria, snow bridges are the standard type to prevent the release of
avalanches in Alpine regions. Flexible snow net systems are installed only to a certain extent.
As steel prices are continuously rising, the price difference between the two systems is getting
smaller and smaller. There is a paradigm shift of the population in their perception of efficient
protection works to fit well into the landscape. In consequence, a variety of approved systems
allow a broad spectrum of applicable protection works to be installed.
In 2006, the WLV launched a comprehensive project for detailed investigation on snow nets.
The goal of the project is to combine empirical experience and scientific data in order to avoid
a long period of trial and error with this system and to provide a scientifically based decisionmaking
aid for engineers within 2−3 years. An intensive survey to gain experience on snow
nets is necessary to ensure the correct application of the system, in places where it is possible,
and the construction of snow bridges, where the need to provide maximum security for
settlements necessitates this.
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