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
Light rockfall prevention mesh used as retention structure in
snowpacks of limited height
Erik Hestnes* and Tore Valstad
Norwegian Geotechnical Institute, PO Box 3930 Ullevål Stadion, N-0806 Oslo, NORWAY
*Corresponding author, e-mail: eh (at) ngi.no
ABSTRACT
A concept for application of light rockfall prevention mesh as retention structures has been
developed. The structure is flexible and easily adjustable to undulating terrain. It is easy to
construct as well as repair, if needed. The retention mesh is designed for snow height limited
to two metres measured normal to the ground within a predefined return period. The cost per
metre was one fifth of an ordinary retaining structure of comparable height.
1. INTRODUCTION
Conventional supporting structures like snow bridges and snow nets are expensive and barely
feasible on slopes where the snow height is limited and primarily controlled by the
precipitation and not by snow drift. Typical examples can be steep meadows, open patches in
wooded areas and potential starting zones of limited size in rocky hillsides.
A concept for application of light run-proof prevention mesh as retention structure has been
introduced as mitigative measures above a new tourist resort in Sirdal in Southern Norway.
The retention structure has been designed for a lifetime of 25 years. Meanwhile vegetation is
meant to be established where conditions are favourable. Beyond that the structure will be
maintained when needed (Fig. 1).
Figure 1 Tourist resort protected by light retention meshes and conventional snow bridges.
Six locations of meshes can be identified by grey posts in the hillside.
52 Light rockfall prevention mesh used as retention structure