Assessing Avalanche-Risk Levels on Walking Tracks in Fiordland, New Zealand

Abstract

Walking tracks which cross relatively rugged avalanche-prone terrain are becoming increasingly popular in New Zealand. Consequently, there exists the need to develop a methodology by which it will be possible objectively to assess the avalanche hazard in the vicinity of the tracks. This paper outlines some procedures that have been used to map avalanche paths, and introduces modifications to an internationally used highway hazard index employed to quantify the danger to walkers. The Fiordland region of south-west New Zealand is an area of spectacular scenic beauty, made famous by the Milford Track which has been walked by large numbers of tourists since the late nineteenth century. In recent years, avalanches have killed one person on the track, severely damaged a lodge, and destroyed several small bridges. Other walking tracks have been opened to tourists in this century and one of these, the Routeburn Track, is included in this study. Avalanche paths which affected the Milford and Routeburn Tracks were mapped in the field using well-established techniques and applying the results of previous research on the Milford Road, where historical records are available for a period of 50 years. The risk to walkers was assessed with a hazard index which depends on frequency of avalanches, numbers of paths, time taken to traverse each path, and numbers of walkers using the track. Results indicate that the avalanche hazard is low to moderate on the Milford Track and moderate on the Routeburn Track. The management implications of these findings are outlined.