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
Simulation of snow drift as a tool for operational avalanche
warning
Simon Schneiderbauer 1 *, Walter Hinterberger 1 , Peter Fischer and Arnold Studeregger 2
1 dTech-Steyr Dynamics and Technology GmbH, Steyrerweg 2, A-4400 Steyr
2 Zentralanstalt für Meteorologie und Geodynamik, Regionalste,lle Steiermark, Klusemannstr. 21, A-8053 Graz
* Corresponding author, e-mail: simon.schneiderbauer (at) dtech-steyr.com
ABSTRACT
A new numerical approach is introduced as a tool for avalanche warning. Avalanches are
mostly triggered by a critical rate of snow loading. The snow drift pattern on mount
Grimming was computed. By examining the snow distribution, the potential avalanche
fracture areas were identified. The results show the applicability of the new simulation
method for operational avalanche warning.
1. INTRODUCTION
Up to now, the evaluation of avalanche danger depends on the knowledge of the properties of
the snow cover, the available meteorological data and the interpretation of meteorological
weather models. Following this approach it is possible to identify regional levels of avalanche
danger, but the outcome is not sufficient for assessing the avalanche danger on small scales.
The determination of snow drift occurrences at critical local failure scars is limited by these
common methods. Due to low visibility during snow storms it is not possible to evaluate the
layering of the snow cover by visual monitoring. In fact, the avalanche professionals are
aware of the existence of a critical snow layer, but it is very difficult to examine the amount of
accumulated snow at potential avalanche fracture areas from the valley. The decision of
avalanche commissions whether roads or ski trails should be closed because of avalanche
danger is based on experience and the available data mentioned above.
In contrast to the current way of determine the critical snow load on slopes and potential
fracture lines we introduce a new approach: Potential avalanches threatening roads, rail traffic
or ski trails are determined by a new simulation tool.
Avalanches are mostly triggered by a critical snow load during storms. The numerical simulation
of snow drift occurrences and precipitation provides an area-wide and time-dependent
distribution of snow depth. Hence, potential avalanche fracture areas can be identified,
supporting the local avalanche commissions and, respectively, the local avalanche warning
services in decision making.
The numerical approach includes time-dependent geometries of the snow cover, time
dependent weather data and complex particle transport phenomena. Additionally, the erosion
and accumulation of snow particles leading to a deformation of the snow cover is determined
by wall shear stress criteria. These deformations of the shape of the snow pack couple to the
wind field and thus the flow is changed by the new geometry.
74 Simulation of snow drift as a tool for operational avalanche warning