ICG project 2: Vulnerability and risk assessment for geohazards. Case studies: Risk associated with avalanches.

This report documents an approach for the probabilistic risk assessment for avalanches. It presents two case studies: 1) A case regarding the risk to a building in an avalanche path: 2) A study concerningtherisk to traffic on a major mountain road. Estimates of hazard, vulnerability and risk are given. The methodology adopted in the present case study refers to the general risk terminology from ICG (2004). The report summarizes vulnerability values due to avalanche impacts retrieved from the literature. In the first case study of a farm in an avalanche path, a combination of empirical meteorological data (extreme snow precipitation data), a slide release model, and a runout model employing Monte-Carlo simulations in both cases are used to quantify hazard and risk. The second case study considers traffic along a road stretch in avalanche-prone area and reveals high risk to individuals. A comparison between the risk with and without å mitigation measure (i.e. with and without a protection gallery) shows the beneficial effect of the mitigation measure. However, waiting traffic increase significantly the risk, which implies that after an avalanche event immediate action is needed to avoid waiting traffic. The case studies illustrate the methods, but do not claim to be generally valid. A main challenge for the proposed methodsis the choice of realistic distribution functions and their parameters. Not enough knowledge is available on this subject. To fill those gaps, expert judgment needs to be applied, more data should be gathered, and more research should be carried out. Deterministic models support the probabilistic approach for the choice of parameters.Norges Forskningsråd (NFR

The use of a numerical snow-drift model as a decision making tool in the planning of avalanche protection measures.

Blowing and' drifting snow is not only a major factor in the assessment of the acute avalanche danger, its contribution to the snow distribution also influences land-use planning. In many parts of alpine terrain end an ge red areas are secured by expensive avalanche protection measures. The effidency of these measures can be affected by the redistribution of snow due to wind. Numerical snow-drift simulation could providc useful information at the planning state of protection measure to increase their effidency and so to reduce costs

Avalanche studies and model validation in Europe, SATSIE. Ryggfonn measurements. Winter 2002 / 2003 and 2003 / 2004

This report presents data collected from the full-scale Ryggfonn project during the Winters 2002/2003 and 2003/2004. The weather and snow conditions described and when possible, the avalanches have been characterized according to the IAHS avalanche code and the deposit boundaries have been mapped. Measurements obtained from the avalanche path include pressure readings from two load cells at a steel tower, as well as avalanche pressure on three load cells fixed to a concrete structure. In addition, normal stress and shear stress were measured on two locations at a 16 high dam. Six geophones, placed on the ground in the runout zone, have detected vibrations from some of the passing avalanches. When possible, for each avalanche the front speeds have been estimated. The estimates are based on continuous-cave Doppler radar measurements, seismic measurements, and the timing between impacts on the constructions.The measurements obtained are briefly discussed and presented in graphs.European Commissio

Cross-comparison of Selected Avalanche Observations

In many mountainous regions, snow avalanches are severe threats to the population and their infrastructure. Delineation of avalanche endangered areas or the design of suffcient mitigation measures require in-depth understanding on the avalanche phenomenon. Measurements and observation constitute the basis for this understanding