OVERVIEW OF THE SPATIAL DISTRIBUTION OF AVALANCHE ACTIVITY IN RELATION TO METEOROLOGICAL AND TOPOGRAPHIC VARIABLES IN AN EXTREME MARITIME ENVIRONMENT

ABSTRACT: The spatial distribution of avalanche occurrences on the Milford Road, Fiordland, New Zealand have been qualitatively examined and related to meteorological and topographic parameters. Using an 18 year data set of over 2800 avalanche occurrences from the Transit New Zealand Milford Road Avalanche Programme we have explored the spatial relationship between avalanche occurrences, topography, and storm direction. The climate is strongly maritime with annual precipitation exceeding 8m (water equivalent), while winter storms often deposit in excess of 2m of snow in the start zones. Pleistocene glaciation of resistant bedrock has resulted in a landscape characterised by U-shaped valleys with very steep sides and extensive snowfields perched almost 1000m above the valley floor. Avalanche activity has been represented on a high resolution aerial photograph in ESRI’s ArcGIS and linked with a 5m DEM, the preceding 72 hours meteorological data, and field observations. This Geographic Information System (GIS) allows for hypothesis testing and visualisation of avalanche occurrences under various temporal, spatial and meteorological parameters. This analysis is aimed at maintaining the institutional memory of the programme and quantifying what local forecasters suspect about the influence of topography and dominant meteorological conditions in relation to the spatial distribution of avalanching on the Milford Road