On avalanche (front) velocity measurements at the Ryggfonn avalanche test site and comparison with observations from other locations
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Besides the runout distance of an avalanche, information on avalanche intensity along the path are often required for hazard zoning or planning of mitigation measures. The avalanche (front) velocity is a common measure as it can be linked to expected impact pressures. At the same time, the velocity of an avalanche determines, if it stays in its usual track or if the avalanche unexpectedly deviates from it and thus endangers areas believed to be safe. Therefore, a reasonable prediction of the expected velocities is most important. However, many of the prevailing avalanche models tend to underestimate velocities in the track or they overestimate the runout distances. In this paper, several avalanche front velocity measurements from the Ryggfonn test site are presented. The measurements are derived from photo and/or video analyses. The measurements can be used for future model calibrations. Additionally, the measurements from the Ryggfonn test site are compared with velocity measurements from other locations to obtain a wider spectrum of avalanche conditions. By analyzing these velocities, constraints for possible rheological models of avalanche flows are obtained.