Calculation of Maximum Snow-Avalanche Run-Out Distance by use of Digital Terrain Models

Digital maps and terrain models are used to calculate maximum snow-avalanche run-out distance based on topographic parameters. Maps of 1:50 000 scale are found to be accurate enough for the purpose. 113 well-known avalanches are discussed in this paper. A computer system is used to calculate terrain parameters such as rupture area ( A ), avalanche-path length ( L ), avalanche-track lengths ( L 1 L 2 ), and run-out lengths ( L 3 ). Maximum run-out angle ( α ), avalanche-track angle (β). and average angle of rupture zone ( γ ) are also found by computer. The use of computer and terrain model reduces subjective judgement of parameters to a minimum. Run-out distance was found to be best expressed by the regression equation: α = 0.91β + 0.08 γ –3.5°. R 2 = 0.94, S = 1.4°. L = 0.93 L 1 + 0.97 L 2 + 0.61 A + 182 m. R 2 = 0.96, S = 137 m.