Study Design & Methodology
This model was designed to evaluate the avalanche release potential of the North Shore Mountains based on terrain characteristics. This approach was chosen for two reasons. The first reason is that the terrain characteristics of an avalanche release area are among the most significant parameters determining the frequency of the avalanche. Maggioni and Gruber conducted a study in 2001 in which they performed a statistical analysis of avalanche releases on well documented avalanche pathways in Switzerland. Their analysis showed that terrain characteristics; specifically slope, curvature and aspect are the most important parameters influencing the avalanche release area frequency. Other terrain characteristics that have been determined to be significant in include forest cover and terrain shape, factors which not only influence the frequency of avalanche release but also the magnitude (McClung 2001).
The second reason this model will be based on terrain characteristics is data availability. The data used for this analysis includes a DEM for the District Of North Vancouver which includes elevation data for the North Shore mountains with a resolution 25m as well as a LANDSAT image that includes the North Shore mountains with a resolution of 30m. Many avalanche models incorporate climatic characteristics such as snow supply and wind effects, but the nature of these characteristics are time dependant and hard to measure on a meaningful resolution. This model does account for these climatic characteristics in an indirect way by using terrain characteristics such as aspect and vegetation coverage which influence wind effects as well as elevation which would affect snow supply. There is however no direct integration of climatic data into this model.
The project design was dependant on a Multi-Criteria Evaluation in IDRISI. Five factors were chosen for analysis. Those factors were SLOPE, ASPECT, TERRAIN COVERAGE, ELEVATION and TERRAIN SHAPE. For each factor weights were assigned based on release area suitability and all factor scores were standardized on a scale of 0 to 100 before input into the Multi-Criteria Evaluation (0 being lowest avalanche release area suitability and 100 being highest). There was also a constraint included in the MCE which masked out all urban and water areas from the analysis. Each factor was weighted according to the relative significance of the parameters on the overall avalanche release suitability. The final output from the MCE produced a map of the North Shore Mountains with avalanche release area suitability ranging from 0 to 100. The areas with a value of 0 were classed as "No Avalanche Release Danger", from 0 to 55 was classified as "Low Avalanche Release Danger", from 55 to 80 was classed as "Moderate Avalanche Release Danger" and from 80 to 100 was classified as "High Avalanche Danger".
0 -No Avalanche Release Danger
1- Low Avalanche Release Danger
2- Moderate Avalanche Release Danger
3- High Avalanche Release Danger
