Karstein Lied

Statistical and geometrical definition of snow avalanche runout

Abstract Two mathematical models for calculating the extreme avalanche runout from a fixed reference point on the path are presented and contrasted. The models are: (1) estimates of confidence limits on regression analyses of topographic parameters and (2) calculation of confidence limits on runout estimates from extreme value statistics. Using the extreme value statistics model to define runout, and polynomial fits to avalanche path profiles, a geometrical model for avalanche terrain was constructed. Taken together, these models redefine the traditional zoning problem by dividing it into (1) an estimation of runout distance, requiring an engineering decision on the choice of confidence limit, and (2) a dynamic problem requiring speed estimates along the incline between the start and stop positions, with the geometry specified by the geometrical model between these positions.

Measurements of powder snow avalanche- nature -

Snow cloud growth rates of powder snow avalanche were obtained with analysing the pictures recorded in Ryggfonn, Norway. Although results showed wide scattering, as far as the data obtained in runout zone are concerned, they roughly agreed with the water tank experiments by Beghin and Olagne (1991).Air movement in snow avalanche cloud was measured with an ultra-sonic anemometer in Kurobe Canyon, Japan. It showed rising current existed near the front and downward at the trail. Comparing with drifting snow threshold and particle suspension criterion, entrainment, suspension and deposition of snow particles in the snow cloud were discussed.

Particle simulation of snow avalanche motion

Abstract The continuum model of a snow avalanche is abandoned, and instead an avalanche is modeled as a collection of ∼10 3 particles that move randomly and independently subject to gravity and resistive forces which have a random fluctuation computed by Monte-Carlo simulation. The model includes entrainment at the avalanche front and the possibility of varying resistive parameters with speed and slope position. Particle statistics computed for an avalanche event in Norway, April 1982, provide a reasonable simulation of recorded speeds and debris distribution.

The avalanche accident at Vassdalen, Norway, 5 March 1986

Abstract Shortly after 1300 hrs on wednesday March 5, 1986, a snow avalanche released from Storebalak, a mountain located at Vassdalen in Nordland county. The avalanche struck 31 men from the North Norway Brigade while they were moving snowmobiles along a stream valley on the north side of Storebalak. Thirty men (3 sergeants and 27 soldiers) originated from Platoon 2, Engineer Company, and one soldier had been borrowed from Infantry Battalion 3. All of the men were swept along by the avalanche, and to a greater or lesser extent, buried in the snow mass. A total of 16 of the 31 men were killed in the accident, and there were 15 survivors. The accident took place in association with the Nato winter exercise, Anchor Express. According to the battle plan, Brigade North was to advance northward along the highway E6 from the Bjerkvik area near Narvik. One battalion, Infantry Battalion 3 was to carry out a flank operation through the valleys Vassdalen, Bukkedalen and Rauddalen to Bonnes, in order to come behind the enemy and cut off the E6 at Salangsdalen. The opening of a snowmobile track through the abovementioned valleys as early as possible, was essential to carrying out this operation. Platoon 2, from the Engineer Company, Brigade North, was in the process of preparing this track when the accident took place.