Slide 2

Methodology and Spatial Analysis

The main input data for LAWIPROG is a high resolution digital elevation model with a maximum cell width of 25 meters. From this raster grid the data for slope, aspect, and altitude are derived through the use of the Idrisi 32 Modules of SLOPE and ASPECT.

The input parameters for the model are derived from reclassification, and weighting of the attributes of slope, altitude, and aspect. A fourth parameter termed hazard level represents the main result of forecast bulletins for snow pack stability. Hazard level weights, a priori, twice as much as input data.

Parameter values are weighted according to their significance:

Parameter Reclassification Scheme Value Range

Hazard Level    Phl                                             2-10
Altitude           Palt                                            1-5
Slope              Pslp                                           1-5
Aspect            Pasp                                          1-5

The predicted hazard grid (PHG) is calculated through the usage of Idrisi 32 Map Calculator as follows:

PHG = Phl * Palt * Pslp * Pasp PHGmax = 10 * 5 * 5 * 5 = 1250

The result is an integer value between 0 and 1250 for each raster cell of the digital elevation model. The predicted hazard grid values are further reclassified to correspond to the standard avalanche hazard descriptors of Low, Moderate, Considerable, High, and Extreme.

PHG                [ 0 - 250 )         ~ >    LOW
                        [ 250 - 500 )     ~ >    MODERATE
                        [ 500 - 750 )     ~ >    CONSIDERABLE
                        [ 750 - 1000 )   ~ >    HIGH
                        [ 1000 - 1250 ) ~ >    EXTREME