GIS-based modeling of debris flows in Banff National Park, Alberta

Abstract

Debris flows are rapid movements of water, rock debris and vegetation down confined channels. Based on field examinations of these channels, a review of current literature and eyewitness accounts of the processes, it is evident that debris flows pose a significant risk to roads, structures and the increasing number of visitors entering Banff National Park. In order to help the Park identify potentially hazardous areas, a GIS database of the locations and attributes of these channels has been developed along with a recurrence interval model. Mode 1 of the model assigns hazard ratings to sites, which may become unstable given predetermined short-term atmospheric conditions. Mode 2 calculates the absolute recurrence interval for an event of given magnitude for each site. Measurements from digitized aerial photographs were evaluated and employed in the recurrence interval model. Photo interpretation skill was important in reducing variance in measurements made. 12 of 22 sites are currently assigned a high hazard rating and a further 8 sites require between 5 and 93 years to reach a high hazard rating. Mean recurrence interval for each site is $64 \pm 6$ years based on a $\rm 20,000m\sp3$ event. Further research regarding rate of rock erosion and meaningful threshold volumes is required. Spatial distribution of meteorological stations for the Park needs to be improved in order to precisely establish the factors which lead to debris flow failure.