On full-scale avalanche measurements at the Ryggfonn test site, Norway

Avalanche measurements carried out at the Ryggfonn test site, Norway, during several winter seasons are analyzed with emphasis on recognizing different flow regimes and estimating flow densities. Measurements include impact pressure readings from load cells mounted at two locations within the track and stress readings from load plates flush with the upstream slope of a catching dam. Pressure measurements were combined with velocity estimates based on cross correlations between the load cell readings and, in several cases, on Doppler radar measurements. In most cases a saltation (fluidized) layer in front of a more dense part could be identified. Doppler radar measurements confirm a fast moving head, in some instants preceded by a slower snout, and decreasing speed from the head to the tail. Calculated accelerations (decelerations) indicate that the effective friction parameter varies strongly and depends on the flow regime.